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I'm in the process of building a 2.2L stroker 4G63 for circuit/time attack. The pistons that come with the stroker kit will give about 9.1:1 CR and the car will run only on E85.
Would it be better to run a piston like the JE Ultra Series which will be more like 9.5:1 - 9.75:1? Would the gains be worth the extra cost of going to a specific/custom piston rather than the off the shelf kit?
Has anyone got any opinions on the new JE Ultra Series pistons?
If you're talking on compression ratio only and not other piston design differences (Ring thickness, skirt length etc) It really comes down to how competitive you want to be and how much money you're happy to spend to get every last bit from it.
In my experience of tuning a large amount of high powered 4G63 Engines the gains you will get going from 9.1 to 9.5 will be minimal. They will be there in forms of quicker spool and more torque/power although not a massively noticeable gain. If you were wanting to go something to 10:1 or higher then it could be more worth it. But once again this comes down to how much you're wanting to spend to be on top.
We are talking gains of around 1-2% I would imagine and not 5-10%.
If you've already got pistons in the kit, and there's no reason to think they won't be up to the job, you're also spending some money that may be better spent elsewhere - better charge cooler, for example. On the other hand, what can you sell the supplied pistons for?
One thing to check on, though, often stroker kits use pistons made with a reduced pin-deck height so, if you do go for an alternative, check that is going to be the same for both. Witht he supplied pistons, you're also stuck with what they supply and they may be less tham optimum. On the other hand, the JE pistons have several design features that may make them worth using, even if the torque/power gains are minimal, like the surface coatings, material strength, ring material, lateral gas ports, etc. If you give them a call, they may be able to make a higher compression version for a nominal cost?
I have used Mahle, Manley, CP, JE pistons on 4g63 and 4g64 with 88, 94 and 100 mm stroke- did not notice any difference. If the tune is correct they all are up to the job.
Thanks guys. Going to stick with the JE pistons included in the Nitto stroker kit.
As the kit already uses JE pistons, you may have the option of the upgraded piston - worth a call if not already ordered/purchased.
Pin-deck height may be an issue, though?