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rod tinkerer
Joined: 14 Apr 2003 Posts: 380
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Posted: Fri May 30, 2003 1:03 pm Post subject: 8:4:1 |
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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? |
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Gene FJ20DET hod rodder
Joined: 06 Oct 2001 Posts: 9163 Location: brisbane
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Posted: Fri May 30, 2003 1:31 pm Post subject: Re: 8:4:1 |
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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 _________________
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Adam Site Admin
Joined: 04 Oct 2001 Posts: 682
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Posted: Fri May 30, 2003 1:34 pm Post subject: WHAT A LOAD of BS |
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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'. |
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QldRobbo tinkerer
Joined: 11 Apr 2002 Posts: 455
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Posted: Fri May 30, 2003 8:50 pm Post subject: Re: WHAT A LOAD of BS |
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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. |
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martin backyard mechanic
Joined: 04 Oct 2001 Posts: 900
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Posted: Fri May 30, 2003 9:13 pm Post subject: Re: WHAT A LOAD of BS |
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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 |
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rod tinkerer
Joined: 14 Apr 2003 Posts: 380
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Posted: Fri May 30, 2003 11:04 pm Post subject: Re: 8:4:1 |
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oh ok sweet, ill ask autobarn for a shim than.
cheers |
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DrIFtA tinkerer
Joined: 13 Mar 2003 Posts: 246
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Posted: Sat May 31, 2003 12:46 am Post subject: Re: WHAT A LOAD of BS |
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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. |
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Pete backyard mechanic
Joined: 05 Oct 2001 Posts: 502
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Posted: Sun Jun 01, 2003 4:15 pm Post subject: Re: WHAT A LOAD of BS |
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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. |
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rust3 backyard mechanic
Joined: 04 Feb 2002 Posts: 971
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Posted: Sun Jun 01, 2003 6:50 pm Post subject: Re: WHAT A LOAD of BS |
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if the car is tuned right you can run both, high compression and boost |
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