going with larger pistons in an F20 rebuild to gain HP

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11-18-2018, 11:42 PM

#11

s2000Junky

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Quote:

Originally Posted by hecash

That's exactly where I have my fuel cut off set on my KPro for my supercharged F22.

Its a good compromise. Where id recommend, if longevity of the motor is appreciated. I put approx 80k on an f22 revving to 9k, half of which were supercharged miles and I never had a rod failure, but I think I did prematurely develop some ovalization in the bores from all the added side loading and I did start to develop cylinder scoring and eventual loss of compression. Some of that I think was attributed to a less then idea tune though.

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11-19-2018, 10:33 AM

#12

nipponS2000

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Quote:

Originally Posted by s2000Junky

Its 100% pnp, no problems. The F22 due to the stock cams only really is worth revving to 8400-8500 rpms and drops off in power too drastically after that, which is good in a way as its easy to tell when to shift, unless your supercharged, and then it doesn't matter. But there are times on the track where having the over rev is certainty beneficial. In my experience the f22 will take 9k rpms reliably, but it cant be great for longevity compared to stock rev limit. Norule that says you have to bounce it off the rev limiter every chance you get just because you can. 8500 rpm in the f22 is the equivalent piston speed of the f20 at 9k just fyi.

Thank you for the infos!So you think with ap1 f20c cams in an f22 there is a possibility to gain some more hp at higher rpms(8600-9000)?

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11-19-2018, 11:10 AM

#13

s2000Junky

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Quote:

Originally Posted by nipponS2000

Thank you for the infos!So you think with ap1 f20c cams in an f22 there is a possibility to gain some more hp at higher rpms(8600-9000)?

Yes, in theory. Surprising a lack of data on this though. Some say the best combo is to leave the exhaust cam in and just run the f20 intake cam. But I have yet to see a dyno on either.

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01-22-2019, 04:01 AM

#14

SpoiledAP1

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Increasing the bore size can also get messy since our deck clearance is actually negative (the piston sticks out of the block) so if you go much bigger than the .25mm over the head will probably need to be machined.

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01-22-2019, 06:32 AM

#15

starchland

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Everyone is talking .25 over, but is this a reality? I only see one company making these and I don't see anyone using. Them

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01-22-2019, 06:48 AM

#16

s2000Junky

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I had a sleeved engine built with 89mm CP pistons with stock head. I guess there is enough room in the head combustion chamber.

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01-22-2019, 09:43 AM

#17

SpoiledAP1

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I'm going to take some measurements today but I had read somewhere that our CCs were only like 87.5mm wide. I want to run an 89mm bore myself but don't want to have to machine the head for it as the quotes I've gotten for it are really high.

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