Noz Posted February 5, 2012 Share Posted February 5, 2012 Evening all. Was wondering what benifits having over sized pistons would give an engine. Stock 2JZ are 86mm, various companies sell 86, 86.5 and 87mm. Is there any benifit to this, aside from lowering the compression to reduce chances of det, the TT compression is fair low as it is, would increasing the piston size from 86mm to 87mm increase the cc capacity enough to make it an added feature? Thats clearly not the answer as it was a random out the box guess, any ideas? May be a silly question, just wondered.. Thanks Quote Link to comment Share on other sites More sharing options...
Scott Posted February 5, 2012 Share Posted February 5, 2012 If the stroke remains the same then the compression ratio will remain the same as I understand it. The only difference oversized pistons will make is increased capacity. Quote Link to comment Share on other sites More sharing options...
Noz Posted February 5, 2012 Author Share Posted February 5, 2012 Ok thanks scott. Quote Link to comment Share on other sites More sharing options...
Ricky49 Posted February 5, 2012 Share Posted February 5, 2012 I got told if you up grade to 87mm then it ends up been 3.1 litre. Quote Link to comment Share on other sites More sharing options...
JamieP Posted February 5, 2012 Share Posted February 5, 2012 I got told if you up grade to 87mm then it ends up been 3.1 litre. 3067cc Quote Link to comment Share on other sites More sharing options...
Noz Posted February 5, 2012 Author Share Posted February 5, 2012 Would there be any power difference with the increase in 0.067cc? i.e. is it even worth it Quote Link to comment Share on other sites More sharing options...
AndyT Posted February 5, 2012 Share Posted February 5, 2012 Would there be any power difference with the increase in 0.067cc? i.e. is it even worth it 67 cc mate not 0.067 of a cc Quote Link to comment Share on other sites More sharing options...
Noz Posted February 5, 2012 Author Share Posted February 5, 2012 From different sources it looks like the main reason is due to wear and tear and re-newing the engine bores. Quote Link to comment Share on other sites More sharing options...
Noz Posted February 5, 2012 Author Share Posted February 5, 2012 67 cc mate not 0.067 of a cc Mis-type!!! Thanks. Quote Link to comment Share on other sites More sharing options...
JamieP Posted February 5, 2012 Share Posted February 5, 2012 Would there be any power difference with the increase in 0.067cc? i.e. is it even worth it 70cc, stock 2jz is 2997cc "Theres no replacement for displacement" so they say, a big turbo can help though. I would have to check with Ryan but iirc mine did 270bhp on SRR as a NA, he mapped mine on zero boost when he started out on the latest map, thats a fully built, higher reving engine though. Quote Link to comment Share on other sites More sharing options...
j_jza80 Posted February 5, 2012 Share Posted February 5, 2012 70cc, stock 2jz is 2997cc "Theres no replacement for displacement" so they say, a big turbo can help though. I would have to check with Ryan but iirc mine did 270bhp on SRR as a NA, he mapped mine on zero boost when he started out on the latest map, thats a fully built, higher reving engine though. I take it the heads been flowed too? Is it still stock CR? Quote Link to comment Share on other sites More sharing options...
JamieP Posted February 5, 2012 Share Posted February 5, 2012 I take it the heads been flowed too? Is it still stock CR? Yes, SRD full race flowed, intake and exhaust manifold are port matched, head and block have been decked so compression will be a little higher. Quote Link to comment Share on other sites More sharing options...
Noz Posted February 5, 2012 Author Share Posted February 5, 2012 Is it possible to get 88mm pistons? I assume it gets to a certain point and the risk of the chamber failing becomes more likely. Quote Link to comment Share on other sites More sharing options...
add heywood Posted February 5, 2012 Share Posted February 5, 2012 As said I thought oversized pistons were just used when the bores have been re done due to wear... Your engine would have to be machines to accept the new pistons. It would cost £££ for very little gains, buy a big turbo instead Quote Link to comment Share on other sites More sharing options...
Noz Posted February 5, 2012 Author Share Posted February 5, 2012 Max recommended oversize pistons seems to be 87mm. 88mm wouldn't be worth the risk anyway I dont think. Yes a bigger turbo would be nice, but then it's best to understand all options and modifications and for what reason you are doing them as well as just replacing a big turbo and hoping everything else will be able to keep up with it. if i can get a little extra power purely on selecting slightly larger pistons its worth considering. looks like 87mm is the max. Quote Link to comment Share on other sites More sharing options...
AndyT Posted February 5, 2012 Share Posted February 5, 2012 There is a 3.4 litre stroker kit available. Lots of dollar though and serious power targets are a must to warrant the expense. Have a read of big power threads like JamieP, LeeP, Michel Lane et al. There are a lot of good references to follow up on for reasons to go down this route. Smaller rebores like 87mm are usually carried out to repair / renew big mile or damaged engines because it's cheaper than replacing the engine. A Supra engine has been proved reliable to over 600 bhp without modification to internals on a regular basis. Compression and leak down tests will prove your engines' health at a far cheaper expenditure. Then you can bung just about anything on it and be happy in the knowledge that it won't break. Quote Link to comment Share on other sites More sharing options...
Noz Posted February 7, 2012 Author Share Posted February 7, 2012 I've read a few places that 88m pistons are a bit risky, though I've found some CP pistons at 87.5mm with stock GTE compression 8.5:1: http://www.ebay.com/itm/CP-Pistons-2JZGTE-Supra-87-5mm-Bore-8-5-Compression-/360414930045 Doesn't give the weight, not sure if the weighted internals thread has these listed. Would 87.5mm be a bit risky, or would there be limitations? Clearly even with a re-build and new box I will be aiming for 600bhp. Anymore and I might as well just buy a TT lump. So 600bhp being the maximum, with a 9.1:1 compression ratio, would 87.5mm be ok? Quote Link to comment Share on other sites More sharing options...
mwilkinson Posted February 7, 2012 Share Posted February 7, 2012 I've 87mm pistons in my new build but this is due to wear and then a messed up rebore as I would otherwise have been 86.5mm. It was my understanding that 87mm was the max reliable rebore on the GTE block. The rebore was done for nothing more than safety and reliability. I would not rely on a rebore as a stand alone performance mod, unless, as stated previously, you go for a 3.4 stroker kit. But that's a completely different ball game. Quote Link to comment Share on other sites More sharing options...
Noz Posted February 7, 2012 Author Share Posted February 7, 2012 Most pistons are 86.5mm, so I will need a rebore whatever, plus I haven't opened it up to see what state the bores are even in. I don't want to stroke it, that's outside my financial bracket and can't justify it just for a little NA-T build. If I have to re-bore anyway then I might as well get oversize and have a little displacement, if I have to do it anyway then it's not costing anymore so worth a look Quote Link to comment Share on other sites More sharing options...
Noz Posted February 7, 2012 Author Share Posted February 7, 2012 Found this thread regarding mkIII supra's on supraforum: http://www.supraforums.com/forum/showthread.php?240760-Where-to-buy-.060-oversized-turbo-pistons I thought the 1jz block and 2jz were the same in width Quote Link to comment Share on other sites More sharing options...
Nic Posted February 7, 2012 Share Posted February 7, 2012 I've read a few places that 88m pistons are a bit risky, though I've found some CP pistons at 87.5mm with stock GTE compression 8.5:1: http://www.ebay.com/itm/CP-Pistons-2JZGTE-Supra-87-5mm-Bore-8-5-Compression-/360414930045There'll be very little material between the cylinders with There'll be very little material between the cylinders if you bored them out to 87.5mm and you'll run the risk of cracking. I'd go with 86.5mm if you can, 87mm only if you have to to get rid of any deep scores. I doubt you'll actually notice any difference in performance from such a small rise in cc's. Quote Link to comment Share on other sites More sharing options...
Hellstrom Posted February 7, 2012 Share Posted February 7, 2012 I have never heard anyone increase the bores for a incredible little performance gain. Most people dont have unlimited resources and rather increase the boost by 0.05 bar and get the same result in terms of power. Also increase the bores and want extreme hp/deplacement is not really à recomanded way to go. The more Boost the higher cylinder pressure and more stress to the cylinder Wall. Reason for OD things is as someone would say for people on a budget its not verry cheap each time you rebuild your "super" engine to get a new engine block. --- I am here: http://maps.google.com/maps?ll=57.729182,11.786052 Quote Link to comment Share on other sites More sharing options...
Noz Posted February 7, 2012 Author Share Posted February 7, 2012 Fair comments. More boost same displacement. Thanks guys! Quote Link to comment Share on other sites More sharing options...
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