View Poll Results: what compression ratio are your running with boost?
8:1
8
2.92%
8.5:1
44
16.06%
9:1
55
20.07%
9.5:1
69
25.18%
10:1
66
24.09%
11:1
32
11.68%
Voters: 274. You may not vote on this poll
High static compression and forced induction
09-15-2007, 08:37 PM
#1
Launching!
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High static compression and forced induction well guys I have a local shop buddy running well into the 9's localy and was wondering how safe it is to actually run high compression and boost. I know the general rule is to lower compression and add more boost but hes running 10.5:1 compression N/A and running about 9 lbs of boost through his 426. its running low 9's now and looks as if it has more. yes hes running race fuel i believe 110 but nuthign out of the norm that we cant get at any track around here. I was just wondering if there are any high compression engine out there ont eh street running boost at all? and maybe if you guy can post up your compression ratios that would give me a resonable answer.
09-15-2007, 09:39 PM
#2
If a boosted engine will use only race fuel, then a higher compression
build will always make much more power.
You just have to be VERY conservative with the tune when running
pump fuel on the street.
My old setup was a 10-1 355 SBC with a Procharger at 10psi.
Be prepared to pull some timing under boost to make a high static comp.
live on the street under boost.
build will always make much more power.
You just have to be VERY conservative with the tune when running
pump fuel on the street.
My old setup was a 10-1 355 SBC with a Procharger at 10psi.
Be prepared to pull some timing under boost to make a high static comp.
live on the street under boost.
09-15-2007, 09:59 PM
#3
Launching!
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Very true I understand pulling timming is a must when using hih compression, I dont mind pulling timming either if im gona be ale to run it tho. You can still make awsome power on 94 tho I would imagine no?? Im looking at running 10.5:1 with about 10 psi MAX at the track ona 427 storker.
09-16-2007, 06:52 AM
#4
If you have the ability to make more boost you should run lower compression, because the small amount of power increase that you get from 2 points of compression is nothing compaired to adding say 5psi
09-16-2007, 08:22 AM
#5
9 Second Club
Of course, a lot also depends on what sort of FI....
if turbo, keep the CR safe, as adding boost is so easy....if a CF blower, go that bit higher on the CR.
if turbo, keep the CR safe, as adding boost is so easy....if a CF blower, go that bit higher on the CR.
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09-16-2007, 08:37 PM
#10
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I was all ready to go 8.8 SCR, but not sure now, thanks guys 
.
What would be optimum SCR for a 408 S91 T6 setup? Cali only has 91 octane here but I was going to run meth on the street (very limited street duty) and race gas at the track. Looks like 9.5 might be a better choice?
.What would be optimum SCR for a 408 S91 T6 setup? Cali only has 91 octane here but I was going to run meth on the street (very limited street duty) and race gas at the track. Looks like 9.5 might be a better choice?
09-16-2007, 08:53 PM
#11
ya I might not even have the choice now since my builder had to rehone it for the lower compression but not sure where he's at. I only have 91 here to but whatever I go I guess it won't be that big of a deal since I am not going all out race. Plus I also have a meth kit if I want to use it.
09-17-2007, 11:55 AM
#14
LS1Tech Co-Founder
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I'd go 8.x:1 for a car that is largely street driven. Race cars run higher compression and run $10 a gallon gasoline. Even stuff like some NMRA SSO cars are between 10 and 11:1, but they run C16 or VP Import.
09-17-2007, 02:10 PM
#18
oh i understand that but this guy said 95% street.....unless he is running DRs all the time...he aint hooking anything else so no need to be able to run 15psi on pump gas if he is on street tires. Now if he is street with a lot of track like Mightymouse and I than maybe different. just my 2 cents
09-17-2007, 02:39 PM
#19
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my car is only a street car it will see the track maybe 1 time a year....I only run 93 octane and we were able to make some good power with a safe tune and I'm at 9:1..with no meth....
09-17-2007, 02:41 PM
#20
I never thought of it this way before until you mentioned it and its a great point for sure. For the street to be more efficient with less boost but than again shitty pump gas and high compression isn't a great match but its all in the tune.
Either way its gonna make more power than I'll need for the street but when he pointed out the efficiency and low end power gains it just makes more sense for my application. Everyone is different though, I can't see myself using 15psi on the street
Either way its gonna make more power than I'll need for the street but when he pointed out the efficiency and low end power gains it just makes more sense for my application. Everyone is different though, I can't see myself using 15psi on the street