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Discussion and questions related to the course Practical Engine Building
Hey guys. Doing a build on a 4g63t. Aiming for 1000hp^. Car ran 9.5 on a 900hp setup looking to hit 9.0. The cp pistons did its job but it has to be retired. See attached photos.
I am currently going with the wiseco hd pistons now. Getting alot of varied responses. Some saying .0025" ptw and others with the regular .0035". For bigger boost levels they state increase ptw by .001". Trying to prevent blow by as the last setup was running proper no blow by excessive. My machinist stated he goes .0025 with the wiseco pistons. I just wanted to get a general opinion. I dont know if the heads could chime in on this for me
It depends a lot on the fuel you are going to use. On E85 you can get away with 0.0035 ptw clearance (I strongly recommend not to go any lower than that) whilst usage of race or pump gas would require a little bit wider clearance as much as 0.004 or even 0.0045. Blow by can be significantly reduced by proper piston rings breaking-in process...
Yeh we are going with ethanol. Hence the reason they say .0025" i believe bcuz its cooler temps. But i just wanted to be safe
Stay with 0.0035ish for ethanol fuel, don't go any smaller than that - this will give you a safety margine you need with that level of power
By the way, I made 9.5 with 700+ HP and 3500 lbs of weight. You definitely should be making low 9s with 1000+ hp
What ptw are you at right now?
My ptw clearance is 0.0045 for E90 and 50 psi of boost on 2.4 stroker with CP pistons.
.45mm? Or .0045"?
0.0045 )) I'm used to thinking in mm))
Don't know the nominal clearance, but - https://auto.wiseco.com/media/wysiwyg/Wiseco/Manuals/Wiseco_Piston-to-Wall_Clearance_Guideline.pdf
Does your machinist regularly build engine just like yours, with that power target and fuel? Does he agree to rebuild the engine, at HIS cost if it fails because of a piston picking up in the bore - which can take EVERYTHING out, if it's bad/
Personally, I'd be erring on the side of safety - might give up a small amount of power/torque but if it does pick up it means giving up everything, including a stack of money and time.
i ended up with .004" ptw and according to wiseco for my power and boost levels its bore x.008" for ring end gap