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Location:
carlingford
Registered:
February 2005
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piston compression ratio
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Tue, 26 July 2005 05:42
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ok i just got my4agze motor rebuilt using mahl 7:9:1 ratio pistons and also the head was port n polished. im still running the supercharger at 10psi which used 2 make 95fwkw. being that lower comp pistons have been used snt there a great chancce that the motor will make less power due to the lower compression only running mild boost
help appreciated, michael
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Location:
Brisbane
Registered:
June 2003
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Re: piston compression ratio
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Tue, 26 July 2005 05:59
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you probly wouldnt want to go much higher comp pistons. As this will cause pinging at that sort of boost. Id either get a bigger blower or install a turbo if you arent happy with your current figures.
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Banned by his request
Location:
moved to tamworth
Registered:
July 2002
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Re: piston compression ratio
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Tue, 26 July 2005 06:23
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V8_MA61 you lost me?10psi you could go 10-1 comp with good charge cooling.
mick,yes you will have less power with the lower comp but not a huge amount.are you changing to turbo? i ask as you dont need that low a comp with a sc12 as max boost will be 14psi or there abouts from them. on one of my 4agte motors i have the comp at 8-1 so i can run 30psi on the track.
mick
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Location:
carlingford
Registered:
February 2005
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Location:
Perth
Registered:
January 2005
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Re: piston compression ratio
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Tue, 26 July 2005 13:44
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Hi,
Just for the record. I'm running 18psi with an SC14 supercharger into an internally standard 8.0:1 4AGZE. At 18psi I'm running 20 degrees of advance and about 0.75 - 0.8 lambda on 95 Octane fuel.
I'll admit thats it too much boost, and I can't rev it past 6K on the 365cc injectors (I need 440 for redline!) and I don't sustain the high boost for very long - I'm gonna cut it down to 15 psi soon for reliabilitys sake.
The point is you can DEFINITELY run higher boost with that comp if your fuelling and spark are o.k. I'd get a bigger crank pulley for a start -say around 170mm that should give you more like 13-14 psi, should make the car lots more fun.
Check out my acceleration vid on bottom of this web page :
http://www.e-wire.net.au/~nrparker/MR2/NewEngine/n ew_engine.htm
Regards, Nick
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Banned by his request
Location:
moved to tamworth
Registered:
July 2002
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Re: piston compression ratio
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Tue, 26 July 2005 22:22
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with a charger on it, you wont even notice it.very small change in hp.
mahle pistons are exellect.
have fun with it.
mick
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Location:
carlingford
Registered:
February 2005
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Re: piston compression ratio
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Tue, 26 July 2005 22:26
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k thnks mate
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