how does compression effect power?
01-27-2007, 03:25 PM
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how does compression effect power with FI? I am in the process of a forged rebuild with an LQ9 370. my static compression will be 8.5:1 and I am running a D1SC setup. Basically I have seen results from guys running 9.0-9.5:1 compression and just want to hear some opinions on how 8.5:1 will react? Any advice?
Last edited by trey04gto; 01-27-2007 at 03:55 PM. Reason: Not specific
01-27-2007, 03:56 PM
#2
well, in simple terms, the drawback is that you'll have less power in N/A form but the plus to it is that youll be able to run more PSI on pump gas...and in race gas form too for that matter. But the results of half a compression pt. is minimal compared to a full point or more. So IMO, I would stick with the 8.5:1 and use the blower to make the power by cramming more air into it! 
01-27-2007, 04:40 PM
#3
I'm kinda in the same position. I had my iron 370 built, but i got different pistons then expected. So my target of around 9.2:1 compression dropped t about 8.6. I have been exploring other options like a smaller chamber t bump compression back up, but i was wondering if i should go with the lower compression since id like to run alotta boost on 93, and id like to spray a 100 or bigger shot at it. Though id be on a race fuel on spray. I'm wondering if such lo compression will kill my nitrous power though.
01-27-2007, 04:55 PM
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I already have a 3.85" pulley on my blower, but since my compression is going to be lower than I expected I am thinking about ordering a larger crank pulley to get some more boost. Can you make up for less compression with bigger cam? My main worry/question is my car being a dog in the lower rpms when boost isnt there.
01-27-2007, 06:19 PM
#5
BBB,
I wouldnt worry too much about running N20 on a low cr. BOOSTED engine.
Trey,
trust me, with 370cid I dont think its possible for it to be a DOG at low rpm's. You can get a bigger cam, but IMO, I dont see the purpose of running it when by 3k rpm's youll be in boost and having a cam to create higher cylinder pressure would be pointless then...Is this a street car?
I wouldnt worry too much about running N20 on a low cr. BOOSTED engine.
Trey,
trust me, with 370cid I dont think its possible for it to be a DOG at low rpm's. You can get a bigger cam, but IMO, I dont see the purpose of running it when by 3k rpm's youll be in boost and having a cam to create higher cylinder pressure would be pointless then...Is this a street car?
01-27-2007, 07:09 PM
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6tech...thanks for the info!! Yes it is a street car, an m6 gto. Think the larger crank pulley would help this out alot? I think with the 3.85 pulley I will only be making 8psi.