Compression Ratio

[joncdeke]

What is the highest compression recommended for a street 914.

Thanks!

Jon

[Rouser]

For the street? I wouldn't recommend pushing anything higher than 8.2-9:1 compression.

You're looking at octane and timing considerations. Remember, even fuel injected 914's had a pretty rudimentary computer system, with no knock sensor, no electronic timing retard and rev limiting capability, no reprogramability, and little flexibility. A nice, well-placed knock & ping and you're sucking valves and pushrods like Coke through a straw.

Sure, you'll hear many pundits claim that with ZEN masters rebuilding techniques, massive head-to-barrel-to-block reconstitution, stress relief, and C-clamps you can make a 914 2.0L pull 2.5-3.0L and 11:1 compression running chicken droppings. That's true of anything; the bottom line is always MONEY.

[Conrad W Peden]

I put a big bore kit on my 1.7. Ported+polished, 2" exhaust, Delorto's, 10:1 compression, cam etc... It barely runs on pump 94 octane. Lots of go though. Motor lasted one autocross season and 50,000 miles.

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CWP/VIR

[Ian_G]

Well I jsut rebuilt my 2L with Euro P&C's and cc'd the head to ~9.4:1. After tweaking the FI when it runs no knock. But I run premium all the time now.

The trick is that you can run high compression AS LONG AS YOU DON'T GO TOO LEAN! Just drop in an O2 sensor and run her a towards the rich side of OK. Unless you go crazy with compression this works fairly well.

Ian