1rareV1

I have a fully forged internal ls2 topped off with built top-end btr stage 3 pds blower cam. CNC ported ls3 heads and last but not least a aggressively hand ported Lsa blower with zl1 lid & 2.4” upper and 10% overdrive lower. WILL BE RAN ON E85. With my current pistons on the way calculations my ratio will be right at 10.0:1 but with just exchange and not extra cost I could change my compression ratio to 11.37:1.
My tuner said due to forged internals and e85 my ration being that high will not matter but I just want everyone’s opinion on what’s gonna give me the best results.

JoeNova

Either is fine honestly, although you need to consider any possible scenarios where the higher compression may become an issue, like needing to fill up on pump gas or whether or not your tuner is capable of getting the tune right.

ddnspider

iTrader: (26)

I'd go 10:0. If it were a centrifugal Id go 11.3 on E.

1rareV1

Yeah that’s what I’m thinking too but I’ve had one of my buddies that’s pretty sharp on boosted builds (this is my first) tell me that running the same exact boost and doing separate runs with both compression ratios would have around a 60-100hp difference. But idk personally

ddnspider

iTrader: (26)

Ive heard that 1 point of CR is worth 2-3% NA. Multiply the gain with boost and its possible you're in that range.....

bammax

I'd stay more conservative if you plan to run it on the street and go all out if it's living most of its life on the track. Building on the edge and then expecting it to be happy stuck in traffic on a hot day is asking for trouble. Building a track car conservatively and running a second slower on every pass will eventually drive you insane.