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  1. #1
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    Member No: 75069 g57yle is an unknown quantity at this point g57yle's Avatar
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    7.5:1 CR

    Sorry accidently posted before forgetting to write!

    ok. i have a 1990 325i M20 2.7i with 7.5:1 Compression Ratio (Cut down eta pistons, eta crank and eta conrods). The block has been rebuilt with new main and big end bearings and piston rings. im using a hybrid T3/T4 .68 exhaust housing and a .50 compressor housing with .57Trim wheel. im also using a nissan GTIR intercooler mounted up front. what sort of boost and HP can i expect to run? and to run this boost wil i have to modify my head, fuelling (pump) and any other things? im still using a rising rate fuel pressure regulator and 735 injectors. the orange ones! shall i do away with this and buy something else for fuelling? i also bought a chip for my ecu claming 28hp and raising the rpm limit by 500 along with smoother idling. is it worth installing? any tips you have please let me know. by the way. since i installed new main bearings the oil pressure JUMPED through the SKY!!! thanks guysThanks in advance

    G 57YLE MOTORSPORT inc

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    Jami
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    Re: 7.5:1 CR

    Hi!
    That CR allows 2 bar boost in 2.0L M10 engine. So I'm thinking that in 2.7L with that tbo you'll be looking something like 1.2 - 1.6 bar as max pressure. CR-wise could run more but I think a larger tbo is needed? Also how high you are rew'ing? I think under 7500 rpms you're safe?! What sort of headgasget? If it's up to task then i assume 2 bar can be used.
    HTH Jami

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    Re: 7.5:1 CR

    im revving up to 6800 and using a standard head gasget and bolts. what about water injection or retarding the timing? do i need to do any of thatThanks in advance

    G 57YLE MOTORSPORT inc

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    Jami
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    Re: 7.5:1 CR

    Hi
    Std headg. may be good upto 0.5 bar. Look for Cometic's or something stronger to allow more boost. Water inj. is merely a way of coping with problem(s) - not solving it in the first place - I think. Seek for a oportunity to bench the car/engine in a place where they can run both fuel & ingn. maps to the Motronic-unit. Goes here for around 200 -300. Also you'll see if injectors or AFM or AMM are bottlenecks etc.
    HTH Jami

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