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compression ratio help?!

Old 11-29-2018, 04:59 PM
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Exclamation compression ratio help?!

hi guys,
Ive got a JR M45 SC to go on my mk1 1600, I'm planning on rebuilding my spare engine while I run my high mileage one until it breaks. the question I have is whats a good compression ratio for a supercharger setup? The engine will have a light head skim, ported and polished, heavier valve springs, my Mazdaspeed high lift cams (cant remember the profile), arp head studs, arp main studs, Manley rods etc...

I know the rule of thumb is lower compression for boosted setups, but that's only really for high boost which my M45 isnt going to make. im looking for as close to 200whp as i can get. the setup will be Inter-cooled, dual throttle bodies, bmw TPS etc... im just looking at piston options and i can only find low compression (8.5:1) and high compression (10.6:1) if im right the import mk1's had a factory ratio of 9.4:1. I know i dont need a fully forged engine for a SC setup as they dont make massive power but ideally i'd like the setup to be able to take a turbo too, because if and when i get bored of the SC I might want to go down the turbo route (only a TD04 maybe 250WHP), unless i fall into the V6 engine swap trap . not sure if its possible to get forged pistons closer to 9.4:1 as that would probably be best to support SC and Turbo setups.

Anyway any help is massively appreciated
Thanks
Kyle
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Old 11-29-2018, 05:03 PM
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Put it on your stock motor. Sell spare 1.6 motor for scrap. Use that money to buy a 1.8. Start there if you are going to sink a single penny into a built motor.
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Old 11-29-2018, 05:30 PM
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truth has spoken
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Old 11-29-2018, 06:01 PM
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what is your projected boost psi and what fuel will you be using?
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Old 11-29-2018, 06:42 PM
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The M45 blower is literally incapable of producing enough airflow to put a stock engine in any danger. Do not waste your money on a built 1.6L.
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