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Working on a durable BUDGET OEM high-compression piston alternative

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defrag010

15+ Year Contributor
420
7
Sep 24, 2004
n/a, Alabama
I've pitched the idea to a few friends, but they mostly nay-say just because it gives them something to do, not because they know any better.

Anyways, I was looking at the big piston size book at work a while back, and I started to look at the 2JZ-GE naturally aspirated supra pistons. I was aware by trolling around on supraforums that these n/a 2jZ-GE motors are easily able to put down ~800whp safely in stock form with good tuning, and it just dawned on me that these could possibly be used as an extreme budget high-compression alternative turbo piston in wake of the n/a 4g63 pistons, which are pretty weak in stock form.

Digging a little deeper, I found out that these supra pistons are Pressure cast, which is why they are obviously putting down insane horsepower figures in stock form. I figured that if 6 pistons can safely manage 800 whp, that's 133 horsepower per piston, which one would assume that using that number, you could safely manage 533 horsepower out of four of them. This is all assuming that the rod is strong enough to withstand the power.

So I found a guy on supraforums to sell me a set of 6 pistons for 50 shipped, and I started to measure once I got them. The supra piston has a stock bore of 86mm (1mm bigger than a stock 4g63), and is short on compression height by .5mm. The ringlands are in the exact same spot as the 4g63 piston, and the wristpin is 1mm bigger on the supra piston (which would be the equivalent in size to a 2G piston).

The construction of these pistons are quite different, using compact skirts and a narrow body. The supra piston looks to be more structurally sound (I can assume this also by the amount of power they can withstand), while being lighter than the 4g63. I don't have a scale, but I can definately tell a difference.

As you can see in the first pic, the dish size is similar in size to the n/a 4g63 pistin pictured next to it. You can also see the similarity in the ring location/size, and the overall size and compression height of the piston.

The top profile of the pistons are different, and the supra piston gives adequate relief for the intake valves (which could come useful in a 4g63 for running a HUGE intake cam!).

I don't have dish measurements, because of the way the supra pistons's valve reliefs are. After alot of research, I found out that the 2jZ-ge cylinder head has approximately 47cc volume, which is close to a 4g63's 45cc. Since the 2jz-ge is a 10.2:1 compression ratio, the .5mm in added quench height (.5mm shorter compression height) from being installed in a 4g63 should equate to around 9.5:1 compression.

I don't really know where I'm going to go with this, but I'm just making this post as a long-term update to any progress and results I make with using these pistons in a 4g63.
I've been researching these pistons for about 4 months so far, and now it's time to start the phase of toying around with it.

So far, my plan is going to consist of using Cryotreated 1G bigrods with ARP hardware, pressfit to the 2jz-ge pistons as a turbo buildup alternative. The goal is not to succeed the stock 4g63 pistons in power output, yet present a higher compression OEM-form alternative to buying forged pistons. I have seen alot of people "overbuild" their engines, and use 9.0-9.5:1 forged pistons just so they can get more compression and not even come close to exceeding stock piston power level. Hopefully, this will allow people to get the compression they want and not have to spend tons of money when they aren't going to make mind-blowing power.

I realize that alot of people will say this is a dumb idea, but if there weren't people who thought outside the box and tried new things, we wouldn't have as big of a swap-database as we do today. This could turn out to be a good project, or it could turnout to fail miserably. Either way, I'm open to suggestions (not flames) that can possibly help me out along the way.
 
id say do it.if you can make em fit then id go for it.like you said,they look stronger and it *should* be ok if the ringlands are big enough.
 
Nothing to it, but to do it.....

1.8T VWs run high compression stock and are very responsive to bolt-ons.

Just do it, then post your findings for us all to see. Much better than speculation :thumb: .
 
sounds like you did some real research.I use to own a supra,and can tell you toyota knows what there doing,now incorporate that into a dsm,geez now we are talking.

I think that would be a sweet setup,run some 950s or bigger,and a nice turbo,with a good cam/head job combo,and it should show some damn good numbers
 
well, were gonna put it in my car as a test bed with a My GT45R with a 1.05 a/r ...... ill keep you guys updated.

-JP
 
99gst racer:

2jz-ge - 33.96mm
4g63 - 34.86mm

both are from my micrometer.

You could take off about .030" from the block's deck height and that will give the supra pistons about .050" quench.
 
haven't had the time or $$ to get any of the machine work done.
 
Stock DSM pistons are anything but weak. People have done solidly over 500whp on stock pistons. Many have run 10's and at least one person 9's on stock mitsu pistons.

Kevin
 
I would be a bit leary of using them, the dome shape is very different than the 4g63 pistons. They look like they could cause the flame front to get very turbulent, which can cause detonation. Also i know you don't wnat to hear this, but the n/t 4g63 pistons are in my opinion are just as strong as the turbo pistons. Currently my car has a n/t shortblock with the head decked .020, and i belive it works out to be like 9.3:1, this is my second motor like this ( the previous one died from a radiator failure) and neither have had a reliablility problem to speak of. The thing is you'll destroy a piston from detonation way before you will break it from two much power. You'll probably hammer out a rod bearing from detonation before you break a piston from two much power. As an example in the 80's Larry Owens had a turbocharged kz1000 drag bike. The class he ran in required that he use factory CAST pistons. He also ran 8.90's, the bike made well over 400 hp from like 75hp stock. The only time it had problems was if it detonated, other than that the piston held up fine. I don't know if you've ever seen a 1000 Kaw piston but they are pathetic our pistons look like goddamned tractor pistons compared to them. Any way I think that brand new topline n/t pistons are like under $100 with rings. I know what i will be using in my next rebuild.
 
Well in the end, it comes down to tuning. I am sure if you didn't tune a supra motor properly you can blow it even at 450 HP.
 
You all are right. I'm dumb for not being a lemming and doing the only things dsm'ers are programmed to when they build engines.

The keyword in this thread's title is Budget. I spent 50$ on six of these pistons, and I'm doing it because I am curious as to how it would work - not to set any records.
 
Hmm, sounds like a cool alternative to me. It'll be interesting to see how it works. Keep records of the total cost of getting the block modified to accept them and what cost is associated with modification needed to mount to the DSM rods. $50 for a set of pistions that could be more durable at high HP levels sounds like a great alternative.

In your earlier search for pistons, have you come across anything that is similar in size but with higher compression yet? Say 12:1 or more?
 
You would have to have a domed piston to get that high of a CR. A true flat top piston will yield about a 11-11.5 static compression ratio.
 
well you can look at it this way, a gasket set costs $100, and you'll probably pay $100 to get your rods machined, oh and a set of rings for those pistons probably $50. So now your $250 in the hole to find out that a set of $50 used pistons, wont really work any better than a set of factory style pistons. I'm not trying to tell you not to do it, but don't be surprised if it doesn't work for shit.
 
why would I need a gasket set if I'm just putting different pistons in the motor?

If you're talking about a new HG with a bigger bore, you're going to need that one no matter what pistons you use. If not, you're going to need a new headgasket anyway.
You're also going to need new rings for whatever pistons you use.
It would also cost the same to have the rods machined for 2G pistons because you would have to do the same thing to the 1G rods to fit the supra pistons as you would the 2G's.

So basically, I will need to do the same things ( nothing more ) and buy the same parts as if I was putting 2G pistons in my motor. the machine work will be the same, and the only thing is that I will be spending less on the actual pistons themselves vs. buying a new set of 2g's.

Have you even seen these pistons in person? I'm wondering what your experience with these are that you can form a judgment on if these will work or not? What's so different about the dish of these pistons vs. the 4g63 pistons that is going to cause a turbulent flame front? The valve reliefs are bigger, but what empirical evidence do you have to support that claim? The supras that use these pistons aren't having problems with them. What makes you think they will act any differently on a 4g63 than they would a 2jZ?
How much horsepower were you able to get out of your n/t shortblock?
 
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