Dear guests and members of the club. In this interview with an expert from Fierce Grandfather, me and other members of the Sti-Club, pressing questions on Subaru pistons were addressed. Stock, forged, Russian pistons TEIKIN, Zelenograd, reviews about them. Let's even talk about pistons with aliexpress!
Fierce Grandfather in this article talks with one of the authoritative experts in the field of engine building and tuning, on whose account there are not one or two high-profile sports projects, many cars built for civilian use in Russia and Europe.
We cannot give his name or place of work, so as not to be considered advertising and to maintain the neutrality of the article. This is indeed a long interview, so make yourself comfortable and bring popcorn, chips or beer with you.
It will be very interesting and informative. Enjoy reading!
If anything - you can subscribe to Fierce Grandfather here. Youtube - Fierce Grandfather Subaru
Fierce Grandfather: Let's go! Question number one. Why do you install forged pistons on a Subaru turbo if there is no plan to increase power and is there any point?
Expert: How to say... In short, without any arguments and life situations there, then it makes no sense. In any case, the standard piston has a fairly good margin of safety and is much lower in terms of thermal clearance. And since we have a smaller thermal gap and, as a result, the sleeve will suffer less, the quieter the engine will work, there is less risk that it will consume oil at high boost loads. Therefore, it is advisable if the power does not exceed the threshold of about 350 NM, if you judge by a 2.5 liter engine, and even by a 2 liter engine, then I would not recommend forging. You can say so ... A good new motor, in a good clearance on standard pistons, will be more pleasant to operate and will run longer and will be more efficient. Because it's not easy to do it on forged pistons... Putting forging - entails additional re-equipment of the structure of the crankcase ventilation engine itself and other things. Therefore, it does not make sense to change the stock pistons to forged, if we summarize the answer to a specific question.
Fierce Grandfather: But from the point of view of comfort, also none. Rumble and all.
Expert: In any case, no matter what they say, our nature is diverse. winter can be fierce and wet; it can be autumn and spring and hot summer. Therefore, whoever says and - the forged piston is still just motorsport. All the same, it is designed for a narrower direction than the stock piston. The stock piston will be more economical, more resourceful and it behaves well in terms of safety margin and, in principle, it will be very easy for it to digest 350 forces. And there are other nuances. If the owners of the motors had failures with stock pistons, partitions fell down, something burned out and burned out - this is not the fault of the pistons. These are related issues. There can be a lot of related problems. From the quality of the calibration of the control unit (that is, the known as flashing or firmware) to the already catering. Ignition, mixture, sensors, etc... Therefore, to blame the piston for the fact that it broke down at 300,350 NM forces is quite naive. There may be problems with the piston (unless, of course, it was defective, we met defective standard pistons and there is a separate procedure, a competent tuner should know how to determine whether it is defective or not, and this is another story). But stock pistons are quite often found defective because they pack the original one one at a time in small cardboard boxes, and in warehouses they are bitten, thrown, thrown, and they have deformations, we have met a lot of that during times. Therefore, you need to carefully check everything, weigh it, look if everything is correct and efficiently assembled. I'm all in for stock piston! Perfect and cool. we met defective standard pistons and there is a separate procedure, a competent tuner must know how to determine whether it is armored or not, and this is another story). But stock pistons are quite often found defective because they pack the original one one at a time in small cardboard boxes, and in warehouses they are bitten, thrown, thrown, and they have deformations, they have met a lot of times. Therefore, you need to carefully check everything, weigh it, look if everything is correctly and efficiently assembled. I'm for stock piston! Perfect and cool. we met defective standard pistons and there is a separate procedure, a competent tuner must know how to determine whether it is defective or not, and this is another story). But stock pistons are quite often found defective because they pack the original one one at a time in small cardboard boxes, and in warehouses they are bitten, thrown, thrown, and they have deformations, they have met a lot of times. Therefore, you need to carefully check everything, weigh it, look if everything is correctly and efficiently assembled. I'm for stock piston! Perfect and cool. and in warehouses they are bitten, thrown, thrown, and they have deformations, they have met a lot of times. Therefore, you need to carefully check everything, weigh it, look if everything is correctly and efficiently assembled. I'm for stock piston! Perfect and cool. and in warehouses they are bitten, thrown, thrown, and they have deformations, they have met a lot of times. Therefore, you need to carefully check everything, weigh it, look if everything is correctly and efficiently assembled. I'm for stock piston! Perfect and cool.
Fierce Grandfather: I agree. Listen, by the way, speaking in terms of weight characteristics, the stock piston is stock compared to forging ... Is there a big difference in weight?
Expert: From forging, the result goes from the brand to the task. It's just that each forged piston has its own specification. But on average most of the time... Forging is certainly lighter weight.
Fierce Grandfather: Yeah. This question is worth it - that without increasing power, it’s not necessary to go forged.
Expert: The fact is that a light piston will not give you anything. In general, it won't. This is a small particle, a small particle of a large mechanism that will not give so much. In order for you to feel some kind of positive increase from light parts - it is necessary not only for pistons, it is necessary to change almost 50% of the engine units so that all of this works together and brings a significant result. And so it will not give anything except for erroneous and unnecessary tuning.
Fierce Grandfather: Question number two. At what point do you need to think about forging. This refers to an increase in the power of the turbine, a banal Stage 1, and so on.
Photography - stock vs forging visually
Expert: And you can and should think about forging in several ways. We will divide them into several classifications and start from tasks. First, depending on what kind of car the owner sets the task. If he is going to use the car in some events, competitions, races and the rest ... There are still many questions where, how and at what power it will be. Because there you already need to understand the details. There are a lot of forged pistons and you need to understand on which forged piston it is all to be assembled and whether it is necessary to assemble it on a forged piston. Therefore, if you are going to increase the power of more than 350 NM force, you plan to use the car in the street, sometimes go to the track nevertheless around the city - then you can consider the already forged piston, but not aggressive, be sure the forged piston should be very similar in geometry to original. Should be Teflon coated. It is desirable that it is gonna be. Well, good casting quality is all you can see in the piston specifications. Which piston is directly needed - should be prompted directly by a motorist or tuner or other specialist. Therefore, in the cases described above, it is, of course, worth thinking about a forged piston. And you must understand that behind the forged piston, then, you must also think about the crankcase ventilation system. It's probably not a secret for anyone that the forged piston is assembled into the motor at a larger thermal gap than the standard piston. Consequently, the crankcase ventilation pressure rises and this system needs to be somehow finalized, because Subaru's regular crankcase ventilation system is quite complicated. It has a large number of breathers, equalizing chambers and simply will not cope.
Expert:In general, let's summarize. If we plan to remove more than 350 forces, nevertheless, somewhere else to participate in some competitions, we definitely need to use a forged piston. I will return to the divisions. There is a second case. It was the first. There are Subarists who love big and early torque very much, therefore, there will be a question about connecting rods. If the connecting rod limits the torque margin, and also you assume that your torque on this turbine can exceed ... Even if you put a restrictor ... And the restrictor gives a very large increase in torque and it pushes it as early as possible. That is, the car becomes more diesel-like. Consequently, in all these cases. That is, if you plan the torque more than the safety margin of the connecting rod allows = you need to put a reinforced connecting rod. But here you are faced with a problem - any forged tuning connecting rod - it is incomparable with the stock piston in configuration because the bottom of the stock piston does not allow it to fit in the section where the connecting rod pin stands. You can say: "Bullshit, but this was all built and everything is fine!". Yes, you can put it, but you will have to cut this beautiful fashionable forged connecting rod in the area of the pin, that is, additional machining will be necessary, sharpen pin and so on. This is already your "collective farm" tuning. If you work according to technology, this method is not suitable, therefore this is the second classification. Therefore, if you rest on the margin of safety in terms of moment, you need an forged connecting rod. Therefore, you must then pair with a forged piston. Something like this.
Fierce Grandfather: Listen, can you simplify the answer to this question? After all, as soon as we start to increase the boost pressure, or drive the operating range to the upper or lower revs, does it already make sense to think about it?
Expert: It makes no sense. Because we can remove both 400 and 500 NM forces at low boost.
Fierce Grandfather: I agree. In general, from what boost can you start thinking? If the car is for the city?
Expert: In terms of boost... Again, this is connected like oil temperature and oil pressure - they border on each other. Also here. Turbine size and boost all play a role. As for small turbines: a stock turbine and the like is safe up to a pressure of 1.5 bar approximately. Well, this is again 300-350 forces.
Fierce Grandfather: One and a half bar boost, you can safely ride, right?
Expert: Yes! STI - 1.5bar stock with tuning. Well, there are other problems not related to the piston.
Fierce Grandfather: I am now trying to simplify for understanding.
Expert: Nothing complicated at all - 350 NM forces without any questions at all.
Fierce Grandfather: And if we allow Precision 6466 to give 0.7 bar - do you need a forged piston?
Expert: Firstly, it will be very difficult because you will have to install giant Wastegate...
Fierce Grandfather: Hypothetically. In addition, the air flow is high, and the pressure is low.
Expert: Even at 0.7 bar with an adequate angles and an adequate fuel mixture, this Precision will give the same 400 NM forces.
Fierce Grandfather: Here, the air flow has increased - but the pressure has not increased. Is it worth it to put forging here?
Expert: Yes, it is, because in heavy gears, when 5th or 6th gear, when there is a long load ... The combustion chamber warms up significantly and it would be better to use a stronger piston.
Fierce Grandfather: Excellent. So the third question. Apart from popular brands like Mahle, Manley, CP, JE and so on... What other options are there now.
Expert: Well, in general, we can not choose too much in these options for the simple reason that we are limited in assortment. In fact, we choose from what is imported to Russia. We tell this for Russian consumers. You can open the catalog and there are a lot of manufacturers who offer their products, pistons, and you can’t say that if you haven’t tried this piston, and you cant say it’s bad. Each manufacturer, if of high quality, competent, gives a very detailed specification on pistons. As for the coefficient of expansion - also for the puddle, the degree of compression. In general, in any case, you can pick up and see if this piston is suitable for your tasks. And from what we have on the market, we correctly listed the brands above. What other pistons are there? All of them are good in their own way. All these brands and pistons - they are all good, they are all for their task. And you can’t tell them that that piston is bad, and that one is good. And that Cosworth is the top notch and Manley is the no-no. This is not true.
Fierce Grandfather: I can try to read this question somehow between the lines. For example, there are some offices in the same Zelenograd that manufacture, including custom, pistons to order. Have you met them?
Expert: I did. Unstable piston. No offense
Fierce Grandfather: Is it unstable in terms of workmanship?
Expert: First, floating in the clearance is what I personally saw. And the second - each piston has an expansion coefficient, I repeat - it has its own. under certain loads. And if the motor is assembled on a more or less tight gap, like a street car, which does not go there twice in a race and goes into analysis, but will be used for a long time ...
Expert:There were such moments, the piston simply smeared like oil on the cylinder. That is, one piston expanded more than the same second third fourth in a row. That is one cylinder. Well, again, the guys are working and finalizing. And it's cool.
Photo - a piston smeared on the cylinder wall. Consequences.
Fierce Grandfather: Yes, it's good that they exist!
Expert: Someday there will be a wonderful finished product. But if you make calibrations without asking for something unreal from the motor, then ... In principle, I think you can use it. We can also say that even you kind of had experience with us - and CP Carillo pistons broke and could not withstand the loads! Although branded and cool piston. And JE had problems. Everyone can have, depends on the project.
Fierce Grandfather: Just a question of what we want from them...
Expert: Yes, so it's better to play it safe and still take the old proven piston, which has already proven itself. And what's new... If let's say tomorrow they close trade and customs, and we won't be able to use anything other than our Russian one... Of course, we'll use local pistons. We will supplement something there ... Write recommendations to factories. We will start working with production, we will start with small capacities.
Fierce Grandfather: Here is the next question in continuation of the previous one. What are the most resistant to detonation and temperature pistons?
Expert: Well, how can I say...
Fierce Grandfather: What would you call... what are the pistons most resistant to the tuner. (Laughs)
Expert: The piston is a part. And this detail is not independent. It really depends on how it's installed correctly. That is, what is the compression ratio. Structural differences.
Expert: It's not just different. Each piston has its own task and a more heat-protected piston will in any case be one that will be Teflon coated, or the top of the piston is covered with this coating. These pistons are more protected, they reflect heat and are more stable. But if we want universality. If the car is ready for a race - if you need to remove peak power, show the result - in fact, you just need high-quality casting, everything is in the gaps - and everything will work.
Fierce Grandfather: By the way, you just accidentally answered the following question! What to look for when choosing pistons if the budget is not limited?
Expert: Again I will return to the specialist who will assemble and tune it. The user must collect a lot of information. And gain experience. You just don't get it by reading forums and stuff. Therefore, first of all, there must be a tuner-assembler, a person who designs a motor, understand the task and understand how it will all work. Know exactly how he sees it all. And only then will it prompt the user or client which piston is better to use. Simplified, for street and more versatile cars - Mahle, Manley are normal. Performs like the machine gun and works! and is not particularly loud. And the temperature is OK and the piston strong in moderation. They hold an insignificant length of detonation. In general, deton is not good! It shouldn't be. It's not like I put a forged piston - well, everything can ring and detonate. It is not right. When you detonate, not only the piston suffers. And the engine suffers! And the valve suffers. Everything suffers. And from the fact that the piston survives, and the liners cranked in the motor ... You will say that they assembled it coolly - and that's it. Therefore, if you qualify, then it is Teflon and coated. The piston for which the specification will be written. Its expansion ratio is under what compression ratio it is. Specified for what type of driving and style of using the car. It will even say what ring gap the manufacturer recommends setting. And the person who understands what he is doing and knows ... He must see it all in his motor project. So the answer to this question is rather different. You must find a competent person who will collect that info and build the engine for you. If you yourself build it and think that you know all this - then refer to what I said earlier. And from the fact that the piston survives, and the liners cranked in the motor ... You will say that they assembled it nicely - and that's it. Therefore, if you qualify, then it is Teflon and coated. The piston for which the specification will be written. Its expansion ratio is under what compression ratio it is. Written down for what type of driving and style of using the car. It will even say what ring gap the manufacturer recommends setting. And the person who understands what he is doing and knows ... He must see it all in his motor project. So the answer to this question is rather different. You must find a competent person who will build for you. If you yourself build it and think that you know all this - then refer to what I said earlier.
Photo - spoiled damaged Subaru piston
Fierce Grandfather: In short, you need to find a tuner who will not put the locks on the rings in one bed?
Expert: And just read - there are manuals everywhere. Even pistons. That is,
Fierce Grandfather: In fact, the manufacturer calculates and explains everything there?
Expert: Everything is planned. Clearance and all the recommendations that yes how. It's just better not to be lazy to calmly open and read. The tuner is competent and experienced - he will make adjustments based on his experience. Based on the installation scheme, he recommends doing everything in detail this way and that.
Fierce Grandfather: Let's go further. Number 6 question. I often hear about TEIKIN pistons. What can be said about them? Are there any reviews?
Expert:The same as in the previous answer to the question. No, not about Zelenograd! There are no bad pistons. They are all fairly normal. There is a specificity, depends on what it was created for. At what gaps it is going to, see how it is executed. Teflon or not. We are not living in the Stone Age now. Therefore, there are many things. And as for the TEIKIN pistons - there was no personal experience. Didn't use it themselves. But if TEIKIN pistons were tested, they would definitely be checked, looked at. We would try. Tested. The only recommendation is that a piston of unknown manufacture, a new one, would not assemble tightly. That is, I would make a tolerance with a large clearance. I would have assembled it to protect myself from the fact that the unknown coefficient of its expansion would be. In order not to cover it over the cylinders. That's all.
Photo - pistons for Subaru with Aliexpress.
Fierce Grandfather: By the way, this is a good recommendation. Another topic! Now more and more people are ordering iron from aliexpress. 2-5 thousand rubles per set. (50$)
Expert: Complete and complete recklessness! In our world, nothing is of excellent quality and for free.
Fierce Grandfather: We sing an ode to the madness of the brave!
Expert: Of course, you yourself understand ... If this kit costs like a restaraunt dinner, what was it made of from aluminum paper?
Fierce Grandfather: I would not be surprised that there are motors assembled on this Chinese farm and that somehow drive and drive. The answer is just the way I see it. Enormous risk! And the return? What do we get from this? Roulette is wild with no chance of winning.
Expert: Maybe it drives. The same as asking: "I need 500NM forces. Here my neighbor got 500NM forces for 1.5K USD, and here you got for 30K USD 500NM forces. Why are you pulling money at all. You can do it quickly, powerfully and cheaply." And when you see for yourself where these 500 forces are... This neighbor has 500NM forces at one point at 5 thousand revolutions, and the other person has these forces and moment in the entire range starting from 3-4 thousand revolutions. And then what goes is one thing. The question is different. What will happen if you give it a load and test it under certain conditions. Track, Dyno. And it's like roulette! If it is convenient to ride like a roulette wheel or a powder keg and worry constantly. No problem! You can buy and put it in for 50$! And if you still need stability, reliability, then of course it is better not to deceive yourself. Because we are not rich enough to buy cheap things.
Fierce Grandfather: Good phrase! Question. What can turn into a purchase of used pistons. Is there any reason.
Expert: For stock, for standard use, if a person needs to go to work and drive with children, everything is fine. You can certainly use this case, but under certain conditions. First, you need to measure your block. As I understand it, the block also drove, check the ellipticity to see the degree of wear and also, when buying used pistons, also see the degree of their wear, because the piston skirt is the first thing that suffers. If it is in good condition with minimal wear and there are no mechanical damages, bites and blows to it. In terms of gaps, it more or less converges. But in principle it is possible. But I think if you buy cheap you will risk big - in motorsport. And if just for a person to ride. Of course you can, why not?
Fierce Grandfather: A matter of state, in short, and initial conditions. Another question. Is forging on an naturally aspirated engine / motor justified?
Expert: If directly in sports. Sport, race, use for the win. That is, forging in general, what is needed? It will be easier at least.
Fierce Grandfather: It is important for us in sports that every horse counts!
Expert: This is if anyone understands that the first tuning of the NA engine is weight. Kinematics. Therefore, the first merit of the piston is that it is lighter. Second. Lower friction because it is shorter, they have shorter skirts than a standard piston. Take the NA piston. He's all big, all fat, all fat. Forged, it will be a little fragile with a small skirt with large shifts. This is the second and third, which is built on a larger gap. Consequently, there is a shift along the ring and there are all sorts of topics with a shift along the finger. That is, a change in volume and so on ... For this, in principle, forging is used, and again, yes, it is stronger. If there are any peak loads, it is high, well, a little, of course, more reliable. This will hold the load better than a standard piston. Nobody denied the same detonation chance. Of course, it does not have such a proper effect as in turbo engines, but ...
Fierce Grandfather: It's good here that there is Zelenograd. Because the rest of the options to make the shift of the fingers of this one are irreplaceable
Expert: Motors in which they are not heavily loaded in terms of torque are easier there. And turbo engines - why do they suffer? They suffer again for the NM torque. The more we get it, the sooner we get it and the duration of this torque. Basically, it turns everything out for us. The torque warms the air, and the combustion chamber warms and the intake and that's it.
Fierce Grandfather: Let's go further. Why OEM pistons on Subaru engines are often called forging if they are not.
Expert: This is more about materials science.
Fierce Grandfather: A question of material compaction?
Expert: Quite simply - stability under certain loads, it's the same as the Japanese. Why is it possible that the WRX is equipped with simple brakes, is equipped with a weaker gearbox, there is a smaller turbine and more, and so on. And let's say STI - and the gearbox is larger and the brakes, and the situation is the same here in terms of configuration. That is, the machine is more powerful - therefore, you need to add a margin of safety. Therefore, they use a slightly different piston casting there.
Fierce Grandfather: That is, there is a borderline state from casting to forging. Forging is also not forging; by and large, it is conventionally considered to be such. (Grandfather's note - forging is also conditionally considered forging, in fact it is a stamp)
Expert: Well, I'm not going to say abstruse. I come from experience that I have repeatedly used WRX pistons in STI, I shot the same results in terms of torque and power and everything drives fine.
Fierce Grandfather: Stock pistons - how much HP does EJ257 hold?
The photo. Power measurement chart EJ257
Expert:257 2.5l motor they have two types of connecting rods that can only be visually identified. One is just EJ255. You can say those. Which went until 2008 from 7 8 to hatchback. There are only rods. After the 8th year, they are a little stronger, apparently casting. Consequently, before the 8th year, in principle, it is undesirable to exceed the torque threshold of 550 newtons, because from personal experience there were already problems. That is where the connecting rods formed. Up to 550 Newton, in principle, there were no problems. And they were limited to 520,500 newtons - everything goes fine. Unless in the rally you don’t hammer somewhere on the ground. Here is the connecting rod that went from the 2008 hatchback, a little denser, loaded up to 600 newtons. After - already there were damages. That is, in general, you can put a mark up to 600nm. As for the piston. The piston does not suffer so much and there are a lot of examples when 500,600 NM forces were reached on stock pistons and it still holds. The question is again the same roulette, that is, reliability. The higher we have, the greater the load on the combustion chamber and the higher the temperature. Consequently, this piston simply cannot pass for so long, but it will withstand it. That is, the contingent of drivers is different. There are people who instantly use loads and do it very carefully. They can ride stock piston and 500 NM forces without question. I personally went by myself, without problems. And those people who feel less of this line and constantly load the motor - of course, they are worse off. Stock is not for them. Well, back to the previous questions - the forged piston has a skirt that allows you to use a reinforced connecting rod. H-shaped, I-beam, etc. And the stock piston - you can’t just put a reinforced connecting rod on it. Probably so. The higher we have, the greater the load on the combustion chamber and the higher the temperature. Consequently, this piston simply cannot pass for so long, but it will withstand it. That is, the contingent of drivers is different. There are people who instantly use loads and do it very carefully. They can ride stock piston and 500 forces without question. I personally went by myself, without problems. And those people who feel less of this line and constantly load the motor - of course, they are worse off. They have this stock piston does not move anymore. Well, back to the previous questions - the forged piston has a skirt that allows you to use a reinforced connecting rod. H-shaped, I-beam, etc. And the stock piston - you can’t just put a reinforced connecting rod on it. Probably so.
Fierce Grandfather: And what can you say about the 257 motor on the dry or wet sleeve. Does it withstand high power? The sleeve, as I understand it, is quite thin?
Expert: Like 257, they are equally fine. That is, the threshold of 350 forces and 550 torque is no longer valid. There are many more processes going on. So its another story
Fierce Grandfather: Then we are baptized and just pray, that is?
Expert: It depends not only on the block. Thermal output is high. The cooling system is overloaded, there are problems and there are problems in the heads, and we begin to seethe and boil, and so on and so forth, but also the famous cut near the 4th cylinder! Where there is the thinnest sleeve. A little warm - it can burst.
Fierce Grandfather:Well, roughly speaking, 350 forces and no more? Ceiling. Well, it's weird. That's all, actually, thanks for answering many pressing questions
That's all, perhaps! Thank you for reading to the end! If you have questions or topics on which you would like to receive more information - write to the club's telegram chat https://t.me/sticlubsu and ask them there! We will definitely find answers to them!
Fierce Grandfather in this article talks with one of the authoritative experts in the field of engine building and tuning, on whose account there are not one or two high-profile sports projects, many cars built for civilian use in Russia and Europe.
We cannot give his name or place of work, so as not to be considered advertising and to maintain the neutrality of the article. This is indeed a long interview, so make yourself comfortable and bring popcorn, chips or beer with you.
It will be very interesting and informative. Enjoy reading!
If anything - you can subscribe to Fierce Grandfather here. Youtube - Fierce Grandfather Subaru
Fierce Grandfather: Let's go! Question number one. Why do you install forged pistons on a Subaru turbo if there is no plan to increase power and is there any point?
Expert: How to say... In short, without any arguments and life situations there, then it makes no sense. In any case, the standard piston has a fairly good margin of safety and is much lower in terms of thermal clearance. And since we have a smaller thermal gap and, as a result, the sleeve will suffer less, the quieter the engine will work, there is less risk that it will consume oil at high boost loads. Therefore, it is advisable if the power does not exceed the threshold of about 350 NM, if you judge by a 2.5 liter engine, and even by a 2 liter engine, then I would not recommend forging. You can say so ... A good new motor, in a good clearance on standard pistons, will be more pleasant to operate and will run longer and will be more efficient. Because it's not easy to do it on forged pistons... Putting forging - entails additional re-equipment of the structure of the crankcase ventilation engine itself and other things. Therefore, it does not make sense to change the stock pistons to forged, if we summarize the answer to a specific question.
Fierce Grandfather: But from the point of view of comfort, also none. Rumble and all.
Expert: In any case, no matter what they say, our nature is diverse. winter can be fierce and wet; it can be autumn and spring and hot summer. Therefore, whoever says and - the forged piston is still just motorsport. All the same, it is designed for a narrower direction than the stock piston. The stock piston will be more economical, more resourceful and it behaves well in terms of safety margin and, in principle, it will be very easy for it to digest 350 forces. And there are other nuances. If the owners of the motors had failures with stock pistons, partitions fell down, something burned out and burned out - this is not the fault of the pistons. These are related issues. There can be a lot of related problems. From the quality of the calibration of the control unit (that is, the known as flashing or firmware) to the already catering. Ignition, mixture, sensors, etc... Therefore, to blame the piston for the fact that it broke down at 300,350 NM forces is quite naive. There may be problems with the piston (unless, of course, it was defective, we met defective standard pistons and there is a separate procedure, a competent tuner should know how to determine whether it is defective or not, and this is another story). But stock pistons are quite often found defective because they pack the original one one at a time in small cardboard boxes, and in warehouses they are bitten, thrown, thrown, and they have deformations, we have met a lot of that during times. Therefore, you need to carefully check everything, weigh it, look if everything is correct and efficiently assembled. I'm all in for stock piston! Perfect and cool. we met defective standard pistons and there is a separate procedure, a competent tuner must know how to determine whether it is armored or not, and this is another story). But stock pistons are quite often found defective because they pack the original one one at a time in small cardboard boxes, and in warehouses they are bitten, thrown, thrown, and they have deformations, they have met a lot of times. Therefore, you need to carefully check everything, weigh it, look if everything is correctly and efficiently assembled. I'm for stock piston! Perfect and cool. we met defective standard pistons and there is a separate procedure, a competent tuner must know how to determine whether it is defective or not, and this is another story). But stock pistons are quite often found defective because they pack the original one one at a time in small cardboard boxes, and in warehouses they are bitten, thrown, thrown, and they have deformations, they have met a lot of times. Therefore, you need to carefully check everything, weigh it, look if everything is correctly and efficiently assembled. I'm for stock piston! Perfect and cool. and in warehouses they are bitten, thrown, thrown, and they have deformations, they have met a lot of times. Therefore, you need to carefully check everything, weigh it, look if everything is correctly and efficiently assembled. I'm for stock piston! Perfect and cool. and in warehouses they are bitten, thrown, thrown, and they have deformations, they have met a lot of times. Therefore, you need to carefully check everything, weigh it, look if everything is correctly and efficiently assembled. I'm for stock piston! Perfect and cool.
Fierce Grandfather: I agree. Listen, by the way, speaking in terms of weight characteristics, the stock piston is stock compared to forging ... Is there a big difference in weight?
Expert: From forging, the result goes from the brand to the task. It's just that each forged piston has its own specification. But on average most of the time... Forging is certainly lighter weight.
Fierce Grandfather: Yeah. This question is worth it - that without increasing power, it’s not necessary to go forged.
Expert: The fact is that a light piston will not give you anything. In general, it won't. This is a small particle, a small particle of a large mechanism that will not give so much. In order for you to feel some kind of positive increase from light parts - it is necessary not only for pistons, it is necessary to change almost 50% of the engine units so that all of this works together and brings a significant result. And so it will not give anything except for erroneous and unnecessary tuning.
Fierce Grandfather: Question number two. At what point do you need to think about forging. This refers to an increase in the power of the turbine, a banal Stage 1, and so on.
Photography - stock vs forging visually
Expert: And you can and should think about forging in several ways. We will divide them into several classifications and start from tasks. First, depending on what kind of car the owner sets the task. If he is going to use the car in some events, competitions, races and the rest ... There are still many questions where, how and at what power it will be. Because there you already need to understand the details. There are a lot of forged pistons and you need to understand on which forged piston it is all to be assembled and whether it is necessary to assemble it on a forged piston. Therefore, if you are going to increase the power of more than 350 NM force, you plan to use the car in the street, sometimes go to the track nevertheless around the city - then you can consider the already forged piston, but not aggressive, be sure the forged piston should be very similar in geometry to original. Should be Teflon coated. It is desirable that it is gonna be. Well, good casting quality is all you can see in the piston specifications. Which piston is directly needed - should be prompted directly by a motorist or tuner or other specialist. Therefore, in the cases described above, it is, of course, worth thinking about a forged piston. And you must understand that behind the forged piston, then, you must also think about the crankcase ventilation system. It's probably not a secret for anyone that the forged piston is assembled into the motor at a larger thermal gap than the standard piston. Consequently, the crankcase ventilation pressure rises and this system needs to be somehow finalized, because Subaru's regular crankcase ventilation system is quite complicated. It has a large number of breathers, equalizing chambers and simply will not cope.
Expert:In general, let's summarize. If we plan to remove more than 350 forces, nevertheless, somewhere else to participate in some competitions, we definitely need to use a forged piston. I will return to the divisions. There is a second case. It was the first. There are Subarists who love big and early torque very much, therefore, there will be a question about connecting rods. If the connecting rod limits the torque margin, and also you assume that your torque on this turbine can exceed ... Even if you put a restrictor ... And the restrictor gives a very large increase in torque and it pushes it as early as possible. That is, the car becomes more diesel-like. Consequently, in all these cases. That is, if you plan the torque more than the safety margin of the connecting rod allows = you need to put a reinforced connecting rod. But here you are faced with a problem - any forged tuning connecting rod - it is incomparable with the stock piston in configuration because the bottom of the stock piston does not allow it to fit in the section where the connecting rod pin stands. You can say: "Bullshit, but this was all built and everything is fine!". Yes, you can put it, but you will have to cut this beautiful fashionable forged connecting rod in the area of the pin, that is, additional machining will be necessary, sharpen pin and so on. This is already your "collective farm" tuning. If you work according to technology, this method is not suitable, therefore this is the second classification. Therefore, if you rest on the margin of safety in terms of moment, you need an forged connecting rod. Therefore, you must then pair with a forged piston. Something like this.
Fierce Grandfather: Listen, can you simplify the answer to this question? After all, as soon as we start to increase the boost pressure, or drive the operating range to the upper or lower revs, does it already make sense to think about it?
Expert: It makes no sense. Because we can remove both 400 and 500 NM forces at low boost.
Fierce Grandfather: I agree. In general, from what boost can you start thinking? If the car is for the city?
Expert: In terms of boost... Again, this is connected like oil temperature and oil pressure - they border on each other. Also here. Turbine size and boost all play a role. As for small turbines: a stock turbine and the like is safe up to a pressure of 1.5 bar approximately. Well, this is again 300-350 forces.
Fierce Grandfather: One and a half bar boost, you can safely ride, right?
Expert: Yes! STI - 1.5bar stock with tuning. Well, there are other problems not related to the piston.
Fierce Grandfather: I am now trying to simplify for understanding.
Expert: Nothing complicated at all - 350 NM forces without any questions at all.
Fierce Grandfather: And if we allow Precision 6466 to give 0.7 bar - do you need a forged piston?
Expert: Firstly, it will be very difficult because you will have to install giant Wastegate...
Fierce Grandfather: Hypothetically. In addition, the air flow is high, and the pressure is low.
Expert: Even at 0.7 bar with an adequate angles and an adequate fuel mixture, this Precision will give the same 400 NM forces.
Fierce Grandfather: Here, the air flow has increased - but the pressure has not increased. Is it worth it to put forging here?
Expert: Yes, it is, because in heavy gears, when 5th or 6th gear, when there is a long load ... The combustion chamber warms up significantly and it would be better to use a stronger piston.
Fierce Grandfather: Excellent. So the third question. Apart from popular brands like Mahle, Manley, CP, JE and so on... What other options are there now.
Expert: Well, in general, we can not choose too much in these options for the simple reason that we are limited in assortment. In fact, we choose from what is imported to Russia. We tell this for Russian consumers. You can open the catalog and there are a lot of manufacturers who offer their products, pistons, and you can’t say that if you haven’t tried this piston, and you cant say it’s bad. Each manufacturer, if of high quality, competent, gives a very detailed specification on pistons. As for the coefficient of expansion - also for the puddle, the degree of compression. In general, in any case, you can pick up and see if this piston is suitable for your tasks. And from what we have on the market, we correctly listed the brands above. What other pistons are there? All of them are good in their own way. All these brands and pistons - they are all good, they are all for their task. And you can’t tell them that that piston is bad, and that one is good. And that Cosworth is the top notch and Manley is the no-no. This is not true.
Fierce Grandfather: I can try to read this question somehow between the lines. For example, there are some offices in the same Zelenograd that manufacture, including custom, pistons to order. Have you met them?
Expert: I did. Unstable piston. No offense
Fierce Grandfather: Is it unstable in terms of workmanship?
Expert: First, floating in the clearance is what I personally saw. And the second - each piston has an expansion coefficient, I repeat - it has its own. under certain loads. And if the motor is assembled on a more or less tight gap, like a street car, which does not go there twice in a race and goes into analysis, but will be used for a long time ...
Expert:There were such moments, the piston simply smeared like oil on the cylinder. That is, one piston expanded more than the same second third fourth in a row. That is one cylinder. Well, again, the guys are working and finalizing. And it's cool.
Photo - a piston smeared on the cylinder wall. Consequences.
Fierce Grandfather: Yes, it's good that they exist!
Expert: Someday there will be a wonderful finished product. But if you make calibrations without asking for something unreal from the motor, then ... In principle, I think you can use it. We can also say that even you kind of had experience with us - and CP Carillo pistons broke and could not withstand the loads! Although branded and cool piston. And JE had problems. Everyone can have, depends on the project.
Fierce Grandfather: Just a question of what we want from them...
Expert: Yes, so it's better to play it safe and still take the old proven piston, which has already proven itself. And what's new... If let's say tomorrow they close trade and customs, and we won't be able to use anything other than our Russian one... Of course, we'll use local pistons. We will supplement something there ... Write recommendations to factories. We will start working with production, we will start with small capacities.
Fierce Grandfather: Here is the next question in continuation of the previous one. What are the most resistant to detonation and temperature pistons?
Expert: Well, how can I say...
Fierce Grandfather: What would you call... what are the pistons most resistant to the tuner. (Laughs)
Expert: The piston is a part. And this detail is not independent. It really depends on how it's installed correctly. That is, what is the compression ratio. Structural differences.
Expert: It's not just different. Each piston has its own task and a more heat-protected piston will in any case be one that will be Teflon coated, or the top of the piston is covered with this coating. These pistons are more protected, they reflect heat and are more stable. But if we want universality. If the car is ready for a race - if you need to remove peak power, show the result - in fact, you just need high-quality casting, everything is in the gaps - and everything will work.
Fierce Grandfather: By the way, you just accidentally answered the following question! What to look for when choosing pistons if the budget is not limited?
Expert: Again I will return to the specialist who will assemble and tune it. The user must collect a lot of information. And gain experience. You just don't get it by reading forums and stuff. Therefore, first of all, there must be a tuner-assembler, a person who designs a motor, understand the task and understand how it will all work. Know exactly how he sees it all. And only then will it prompt the user or client which piston is better to use. Simplified, for street and more versatile cars - Mahle, Manley are normal. Performs like the machine gun and works! and is not particularly loud. And the temperature is OK and the piston strong in moderation. They hold an insignificant length of detonation. In general, deton is not good! It shouldn't be. It's not like I put a forged piston - well, everything can ring and detonate. It is not right. When you detonate, not only the piston suffers. And the engine suffers! And the valve suffers. Everything suffers. And from the fact that the piston survives, and the liners cranked in the motor ... You will say that they assembled it coolly - and that's it. Therefore, if you qualify, then it is Teflon and coated. The piston for which the specification will be written. Its expansion ratio is under what compression ratio it is. Specified for what type of driving and style of using the car. It will even say what ring gap the manufacturer recommends setting. And the person who understands what he is doing and knows ... He must see it all in his motor project. So the answer to this question is rather different. You must find a competent person who will collect that info and build the engine for you. If you yourself build it and think that you know all this - then refer to what I said earlier. And from the fact that the piston survives, and the liners cranked in the motor ... You will say that they assembled it nicely - and that's it. Therefore, if you qualify, then it is Teflon and coated. The piston for which the specification will be written. Its expansion ratio is under what compression ratio it is. Written down for what type of driving and style of using the car. It will even say what ring gap the manufacturer recommends setting. And the person who understands what he is doing and knows ... He must see it all in his motor project. So the answer to this question is rather different. You must find a competent person who will build for you. If you yourself build it and think that you know all this - then refer to what I said earlier.
Photo - spoiled damaged Subaru piston
Fierce Grandfather: In short, you need to find a tuner who will not put the locks on the rings in one bed?
Expert: And just read - there are manuals everywhere. Even pistons. That is,
Fierce Grandfather: In fact, the manufacturer calculates and explains everything there?
Expert: Everything is planned. Clearance and all the recommendations that yes how. It's just better not to be lazy to calmly open and read. The tuner is competent and experienced - he will make adjustments based on his experience. Based on the installation scheme, he recommends doing everything in detail this way and that.
Fierce Grandfather: Let's go further. Number 6 question. I often hear about TEIKIN pistons. What can be said about them? Are there any reviews?
Expert:The same as in the previous answer to the question. No, not about Zelenograd! There are no bad pistons. They are all fairly normal. There is a specificity, depends on what it was created for. At what gaps it is going to, see how it is executed. Teflon or not. We are not living in the Stone Age now. Therefore, there are many things. And as for the TEIKIN pistons - there was no personal experience. Didn't use it themselves. But if TEIKIN pistons were tested, they would definitely be checked, looked at. We would try. Tested. The only recommendation is that a piston of unknown manufacture, a new one, would not assemble tightly. That is, I would make a tolerance with a large clearance. I would have assembled it to protect myself from the fact that the unknown coefficient of its expansion would be. In order not to cover it over the cylinders. That's all.
Photo - pistons for Subaru with Aliexpress.
Fierce Grandfather: By the way, this is a good recommendation. Another topic! Now more and more people are ordering iron from aliexpress. 2-5 thousand rubles per set. (50$)
Expert: Complete and complete recklessness! In our world, nothing is of excellent quality and for free.
Fierce Grandfather: We sing an ode to the madness of the brave!
Expert: Of course, you yourself understand ... If this kit costs like a restaraunt dinner, what was it made of from aluminum paper?
Fierce Grandfather: I would not be surprised that there are motors assembled on this Chinese farm and that somehow drive and drive. The answer is just the way I see it. Enormous risk! And the return? What do we get from this? Roulette is wild with no chance of winning.
Expert: Maybe it drives. The same as asking: "I need 500NM forces. Here my neighbor got 500NM forces for 1.5K USD, and here you got for 30K USD 500NM forces. Why are you pulling money at all. You can do it quickly, powerfully and cheaply." And when you see for yourself where these 500 forces are... This neighbor has 500NM forces at one point at 5 thousand revolutions, and the other person has these forces and moment in the entire range starting from 3-4 thousand revolutions. And then what goes is one thing. The question is different. What will happen if you give it a load and test it under certain conditions. Track, Dyno. And it's like roulette! If it is convenient to ride like a roulette wheel or a powder keg and worry constantly. No problem! You can buy and put it in for 50$! And if you still need stability, reliability, then of course it is better not to deceive yourself. Because we are not rich enough to buy cheap things.
Fierce Grandfather: Good phrase! Question. What can turn into a purchase of used pistons. Is there any reason.
Expert: For stock, for standard use, if a person needs to go to work and drive with children, everything is fine. You can certainly use this case, but under certain conditions. First, you need to measure your block. As I understand it, the block also drove, check the ellipticity to see the degree of wear and also, when buying used pistons, also see the degree of their wear, because the piston skirt is the first thing that suffers. If it is in good condition with minimal wear and there are no mechanical damages, bites and blows to it. In terms of gaps, it more or less converges. But in principle it is possible. But I think if you buy cheap you will risk big - in motorsport. And if just for a person to ride. Of course you can, why not?
Fierce Grandfather: A matter of state, in short, and initial conditions. Another question. Is forging on an naturally aspirated engine / motor justified?
Expert: If directly in sports. Sport, race, use for the win. That is, forging in general, what is needed? It will be easier at least.
Fierce Grandfather: It is important for us in sports that every horse counts!
Expert: This is if anyone understands that the first tuning of the NA engine is weight. Kinematics. Therefore, the first merit of the piston is that it is lighter. Second. Lower friction because it is shorter, they have shorter skirts than a standard piston. Take the NA piston. He's all big, all fat, all fat. Forged, it will be a little fragile with a small skirt with large shifts. This is the second and third, which is built on a larger gap. Consequently, there is a shift along the ring and there are all sorts of topics with a shift along the finger. That is, a change in volume and so on ... For this, in principle, forging is used, and again, yes, it is stronger. If there are any peak loads, it is high, well, a little, of course, more reliable. This will hold the load better than a standard piston. Nobody denied the same detonation chance. Of course, it does not have such a proper effect as in turbo engines, but ...
Fierce Grandfather: It's good here that there is Zelenograd. Because the rest of the options to make the shift of the fingers of this one are irreplaceable
Expert: Motors in which they are not heavily loaded in terms of torque are easier there. And turbo engines - why do they suffer? They suffer again for the NM torque. The more we get it, the sooner we get it and the duration of this torque. Basically, it turns everything out for us. The torque warms the air, and the combustion chamber warms and the intake and that's it.
Fierce Grandfather: Let's go further. Why OEM pistons on Subaru engines are often called forging if they are not.
Expert: This is more about materials science.
Fierce Grandfather: A question of material compaction?
Expert: Quite simply - stability under certain loads, it's the same as the Japanese. Why is it possible that the WRX is equipped with simple brakes, is equipped with a weaker gearbox, there is a smaller turbine and more, and so on. And let's say STI - and the gearbox is larger and the brakes, and the situation is the same here in terms of configuration. That is, the machine is more powerful - therefore, you need to add a margin of safety. Therefore, they use a slightly different piston casting there.
Fierce Grandfather: That is, there is a borderline state from casting to forging. Forging is also not forging; by and large, it is conventionally considered to be such. (Grandfather's note - forging is also conditionally considered forging, in fact it is a stamp)
Expert: Well, I'm not going to say abstruse. I come from experience that I have repeatedly used WRX pistons in STI, I shot the same results in terms of torque and power and everything drives fine.
Fierce Grandfather: Stock pistons - how much HP does EJ257 hold?
The photo. Power measurement chart EJ257
Expert:257 2.5l motor they have two types of connecting rods that can only be visually identified. One is just EJ255. You can say those. Which went until 2008 from 7 8 to hatchback. There are only rods. After the 8th year, they are a little stronger, apparently casting. Consequently, before the 8th year, in principle, it is undesirable to exceed the torque threshold of 550 newtons, because from personal experience there were already problems. That is where the connecting rods formed. Up to 550 Newton, in principle, there were no problems. And they were limited to 520,500 newtons - everything goes fine. Unless in the rally you don’t hammer somewhere on the ground. Here is the connecting rod that went from the 2008 hatchback, a little denser, loaded up to 600 newtons. After - already there were damages. That is, in general, you can put a mark up to 600nm. As for the piston. The piston does not suffer so much and there are a lot of examples when 500,600 NM forces were reached on stock pistons and it still holds. The question is again the same roulette, that is, reliability. The higher we have, the greater the load on the combustion chamber and the higher the temperature. Consequently, this piston simply cannot pass for so long, but it will withstand it. That is, the contingent of drivers is different. There are people who instantly use loads and do it very carefully. They can ride stock piston and 500 NM forces without question. I personally went by myself, without problems. And those people who feel less of this line and constantly load the motor - of course, they are worse off. Stock is not for them. Well, back to the previous questions - the forged piston has a skirt that allows you to use a reinforced connecting rod. H-shaped, I-beam, etc. And the stock piston - you can’t just put a reinforced connecting rod on it. Probably so. The higher we have, the greater the load on the combustion chamber and the higher the temperature. Consequently, this piston simply cannot pass for so long, but it will withstand it. That is, the contingent of drivers is different. There are people who instantly use loads and do it very carefully. They can ride stock piston and 500 forces without question. I personally went by myself, without problems. And those people who feel less of this line and constantly load the motor - of course, they are worse off. They have this stock piston does not move anymore. Well, back to the previous questions - the forged piston has a skirt that allows you to use a reinforced connecting rod. H-shaped, I-beam, etc. And the stock piston - you can’t just put a reinforced connecting rod on it. Probably so.
Fierce Grandfather: And what can you say about the 257 motor on the dry or wet sleeve. Does it withstand high power? The sleeve, as I understand it, is quite thin?
Expert: Like 257, they are equally fine. That is, the threshold of 350 forces and 550 torque is no longer valid. There are many more processes going on. So its another story
Fierce Grandfather: Then we are baptized and just pray, that is?
Expert: It depends not only on the block. Thermal output is high. The cooling system is overloaded, there are problems and there are problems in the heads, and we begin to seethe and boil, and so on and so forth, but also the famous cut near the 4th cylinder! Where there is the thinnest sleeve. A little warm - it can burst.
Fierce Grandfather:Well, roughly speaking, 350 forces and no more? Ceiling. Well, it's weird. That's all, actually, thanks for answering many pressing questions
That's all, perhaps! Thank you for reading to the end! If you have questions or topics on which you would like to receive more information - write to the club's telegram chat https://t.me/sticlubsu and ask them there! We will definitely find answers to them!
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