Corbzin

so i keep hearing different things with compression and turbo, some say the lower the better some say not so..... my compression is 9-1 right now with a 42. a/r 48. exhaust ball bearing turbo... i was talking to a guy at a shop about it and he said since i have a smaller turbo i could go a little higher compression 11-1 to make more power.

sounded iffy to me cause i thought higher compression was bad for turbo cars.

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Corbzin

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Fabrik8

You have a turbo. If you want more power turn up the boost, or get a bigger turbo, or make sure everything like the intercooler works as well as it should.

In general though, high compression ratios are pretty risky for turbo use, yes.

White Devil

Just as Fabrik8 said, especially about making sure everything is to specs. That includes all vac hoses, engine gaskets, spark plugs, seals, cooling lines, oil lines, etc..., as they are all integral to a properly running turbo. All this should be checked and/or replaced prior to tinkering with the turbo, no exceptions. If you start feeding more boost into a system that is only marginally at factory specs or worse, you will quickly develop additional problems like:

1: Overheating
2: Gasket failure (especially head gaskets)
3: Split/blown hoses or lines
4: Spark detonation from lean running mixtures or poor timing
5: Other engine issues all the way up to catastrophic fail.

erik02

Corbzin, you should pick up a copy of Maximum Boost by Corky Bell. A higher compression ratio will have higher combustion temperatures and make more power on the same amount of boost, however if combustion temperatures get to high you will get what is known as pinging. A lower compression ratio will be substantially easier to have tuned, and cheaper for you in the long run.

Mindless

Tune tune tune.

Corbzin

alright cool thanks guys, it wasnt the hp really it was the off the line power i was trying to get.

crasy87rexsi

+1
Its all about the tune, but with the right tune 10-11:1 is not bad for turbo. Just lower compression is safer, especially running pump gas. Keeping the compression up will help with off/low boost power, but like I said running on pump with higher than normal compression wouldn't be the best for boost.

laserspeeddemon

9:1 is fine for boost.

The smart way to tune is to log each run with a wideband A/F reading and monitor knock while adjusting boost, fuel trim and timing.

The easy way. Log a few runs turning up boost with each run, when you start to knock, turn back boost a little.