Compression VS Boost
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On The Tree
Joined: Mar 2012
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Compression VS Boost Currently have an lq9 in my truck running a d1sc @ 8psi. Its time for a rebuild, which will just be a .030 over, forged pistons and gapping the rings for FI, otherwise it will just be freshened up. My question is what's the correlation between compression and boost? Will keeping the compression at 10.0:1 and running 10psi be essentially the same as say 9.0:1 and 12lbs? Or will the lower compression VS more boost create more power overall? Also what's safer? I'm in CA, with 91 being the best fuel I can get. Its daily driven, and see's about 20 passes a year down the 1/4 mile.
9 Second Club
Joined: Nov 2003
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From: Norn Iron
Go with 9.0:1
it will be mega safe and if you want more power, just add some boost...and again it will be mega safe.
Whilst there is a current fascination with high compression...largely it is just that. Dont think for one second that more normal CR's cannot go fast.
But if you never intend to use much more than 8psi, maybe go for 9.5:1.
But tjr higher you go, there will be more risk, and more chance of being knock limited because of the fuel.
it will be mega safe and if you want more power, just add some boost...and again it will be mega safe.
Whilst there is a current fascination with high compression...largely it is just that. Dont think for one second that more normal CR's cannot go fast.
But if you never intend to use much more than 8psi, maybe go for 9.5:1.
But tjr higher you go, there will be more risk, and more chance of being knock limited because of the fuel.
Joined: Mar 2007
Posts: 1,151
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From: Saskatchewan, Canada - where arguing "DA" is for the slow and weak...
Consider how your calculated dynamic compression ratio is going to be factored in with both the mass airflow and cam timing/events taken into consideration. DCR is more important than a static CR.
