Quote:
Originally Posted by bquatt
Look up the 320i compression ratio and then compare that to the 330i. I've asked tuners about this. They do not tune 320's to the same level as the 330 due to this.
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this was true way back when
In the B series engines (b46, b48) it's a bit complicated because the 20i had multiple different engines.
B48B20A (used ONLY in 20i and in SOME 30e hybrid setups)
B48B20B (used in 20i AND 30i identical hardware with different software tune)
The B48B20A has different hardware to the 20B and yes compression ratio is ONE of the things which sets the 20B and 20A apart.
If you have a 20i with a B48B20B engine, you CAN safely tune it in the same way as the 30i (with caveats) from a hardware perspective. The caveat being, if you use JB4/Racechip, you're going to be "knee capped" by certain settings in the 20i software tune which create a lot of trouble i.e AFR never targeting anything other than stoichemetric & hardcoded throttle closures (I know this because this is what I ran into).
If you have a 20i with a B48B20B and do a flash tune (BM3, MHD, Ecutek, etc.) you can unlock it's full capability by freeing up DME to target lower AFR which give you better timing and for all intents and purposes becomes identical to a tuned 30i.
If you have a 20i or 30e with a B48B20A unfortunately there's much lower headroom in what you can do because of the compression ratio and difference in other hardware around/in the engine.