8:4:1

[rod]

This is the compression ratio for a Stock 2L isuzu...

i know that urve gotta hav 8:1 or below too run a turbo
BUT
Wats the go with the '4'?

And wat does these terms mean?

[Gene FJ20DET]

buy a shim from like auto barn. fuck it will be worth it. u will drop the compresion nicly and will beable to run more boost safly

there like a metal gasket about 1mm thick. i had one in myold gem. i think it cost $60
_________________

[Adam]

You don't have to have equal to or less than 8:1 to run a turbocharger, it really bugs me when nonsense like this gets passed off as a 'fact'.

[QldRobbo]

Yeah, 8.4:1 is low enough to run a turbo, especially when you are only going for 7-8 PSI aren't you rod?

I wouldn't worry about it... only do worry about it if after you get it running it pinks, then do something about it.

[martin]

you can run whatever bloody compression ratio you want and turbo ya car

it just wont last to long if you boost it to hard

think about it...

if you have a really high compression ration on a naturally aspirated (ie. no turbo) engine, then its more likely to be prone to detonation

you can think of a turbo as a way of increasing your compression ratio by blowing more pressurised (compression/pressure see the connection air into the cylinders

so if you have a lower static compression ration (ie. 7.5:1) then you can put more pressurised air (up the BOOOOST!!) into the cylenders and there is less chance of detonation (you have to make sure there is enough fuel going in, even distribution, engine running correct temp blah blah blah)

i only know this shyte cause i've read up on it and played with my old cordia so like i said below have a read and all your prayers will be answered my son! praise be alah

[rod]

oh ok sweet, ill ask autobarn for a shim than.
cheers

[DrIFtA]

As Martin and Adam stated, any comp ratio can be run with a forced induction set-up. The key factors for avoiding a time bomb engine are pretty much 1) tuning, 2) fuel (supply and RON) and 3) support to run your desired boost (gaskets, o-ringing etc.) Yes, i know o-rings dont reduce detonation, but they do aid in the sealing process in case of detonation.
I know this is wildly different from your desired boost and power figures but take for example the HKS R33 GTR....
This engine produces approx 1300ps and 1100nm of torque. Now with the advice you've been given, you'd assume that it's comp ratio would be damn loooooooooowwww to support the kind of boost needed to create that kind of raw horsepower. Surprise surprise it's not...
How does 9.8:1 comp ratio with 2.4 bar (35 odd psi) of boost sound ???
They have built the engine internally to handle this and most importantly TUNED it to not explode on the 1st stab of the loud pedal.
Now in your case on a G161/200 or what have you, anything under 10 psi should be fine as long as you have a decent fuel supply, 'possibly' an intercooler (or some type of support to reduce heat), and have the thing tuned professionally to accept forced induction. I think it was Elky or maybe it was someone else here, they are running approx 18psi and have been for a couple of years without a hitch.
My advice would be to talk to a different engineer about what you are chasing in terms of forced induction.

[Pete]

yea i had a pvan once, corolla ke70. i had a mate who did exhausts. we literally got some pipe, bolted a turbo to the new exhaust manifold, ran it through an old 180sx intercooler that we screwed to the front of the car and then into the top of the carby. pulled the cholk out and thrashe the shit out of it! : )

it spooled, that was really all i wanted. a $1500 car, $200 on the conversion and 3 weeks of fun in the sun.

[rust3]

if the car is tuned right you can run both, high compression and boost