Compression and Pump Gas

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04-25-2011, 02:26 PM

oakley6575

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Compression and Pump Gas

Is 11.5:1 compression to high to run 91 octane pump gas in the summer heat of Las Vegas?

I'm running 408 LQ4 block with stock LS3 heads.

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04-25-2011, 02:34 PM

silverz28camaro

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Thats getting pretty close, I',m 11.6 on 93, but i have an aluminum ls2 with stock cu.in.

For cruzing around i don't see an issue, but if you were to go racing i would put a gallon or 2 or 110 in there just to be safe.

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04-25-2011, 04:15 PM

oakley6575

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It will just be a daily driver but I'm worried about the 115 degree days in vegas.

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04-25-2011, 04:22 PM

c0ncEpT

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Set it to pull timing as the IAT's go up and you will be alright.

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04-25-2011, 04:40 PM

s346k

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if you're willing to pull timing you could run 13:1 compression on 91 oct haha.

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04-25-2011, 04:42 PM

oakley6575

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Quote:

Originally Posted by s346k

if you're willing to pull timing you could run 13:1 compression on 91 oct haha.

The whole point of my question was can I run 11.5:1 without any knock retard.

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04-25-2011, 07:58 PM

MPFD

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Quote:

Originally Posted by oakley6575

The whole point of my question was can I run 11.5:1 without any knock retard.

A retard...you know like on Rainman

It will be fine, just don't beat the **** out of it for exended periods of time when its that hot...

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04-25-2011, 08:05 PM

Beaflag VonRathburg

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It will completely depend on the valve events of the camshaft and the tune.

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04-25-2011, 09:41 PM

DONAIMIAN

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Should be fine. Like the others said it comes down to a number of factors including heads and cam set up. With the elevation (and less dense atmosphere associated with it) you SHOULD be fine because the intake charge wont be as dense.

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04-26-2011, 08:31 AM

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jmm98LS1

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Quote:

Originally Posted by Beaflag VonRathburg

It will completely depend on the valve events of the camshaft and the tune.

This. I'm running 12:1 SCR and 8.7:1 DCR with 91 octane, but it takes careful parts selection and tuning.

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04-26-2011, 12:27 PM

#11

chrisfrost

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You can put a larger radiator in there and help keep it from pre-detonating . Good luck

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04-26-2011, 05:47 PM

#12

chrs1313

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Quote:

Originally Posted by Beaflag VonRathburg

It will completely depend on the valve events of the camshaft and the tune.

yup...static compression doesn't really mean anything...dcr is what you want to know...it takes the cam into account

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04-26-2011, 05:49 PM

#13

oakley6575

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Quote:

Originally Posted by chrs1313

yup...static compression doesn't really mean anything...dcr is what you want to know...it takes the cam into account

What DCR number do you keep it under to run 91 pump gas?

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04-26-2011, 05:58 PM

#14

oakley6575

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Looks like my DCR is 8.40........ What does that mean?

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04-27-2011, 05:19 PM

#15

chrs1313

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don't know about 91 oct...but I have pushed 9.0:1 on pump 93...some other things to take into consideration is the quench depth and how efficient the chamber is on the head...this will help lower knock too...

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04-27-2011, 05:25 PM

#16

Sales2@Texas-speed

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Quote:

Originally Posted by chrs1313

yup...static compression doesn't really mean anything...dcr is what you want to know...it takes the cam into account

It depends on more than DCR! Altitude and climate (density) play a HUGE part of this, and DCR ignores that.

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