Compression ratios HELP!

E28 technical advice asked and given! Troubleshooting, modifications and more.
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Dirtym30
Posts: 75
Joined: Jan 12, 2020 5:30 PM
Location: Toronto, Canada

Compression ratios HELP!

Post by Dirtym30 »

Hi m30 Gurus. I’m about to pull the trigger on a set of cp Carrillo pistons for my m30b34 in prep for a turbo in the future. The only thing is off the shelf I can get a set with all the oem specs except the compression ratio which would be 8.5:1 my understanding is stock is 8:1. Would I still be able to use these pistons before I turbo and on stock tune? I’m not financially ready to turbo quote yet but I would like to drive my car around in the spring. Thank you all. :rofl:
Mike W.
Posts: 26872
Joined: Feb 12, 2006 12:00 PM
Location: California Whine Country

Re: Compression ratios HELP!

Post by Mike W. »

Sure, those will work fine. You might need to run mid grade gas instead of regular. Maybe, not for sure, just keep an ear out. But 8.5:1 will still have a dish in it, just not as big a dish. You should notice a little bit of HP improvement, not a lot, but some. Fuel is controlled by the AFM mostly, with fine tuning from the O2 input, so that's covered. Timing will be plenty close enough. I would guess it would bump you up into the high 180s compared to the stock 182HP, but still below 190. Should be nice, just like stock, but with a bit more.
Dirtym30
Posts: 75
Joined: Jan 12, 2020 5:30 PM
Location: Toronto, Canada

Re: Compression ratios HELP!

Post by Dirtym30 »

Thank you Mike!
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