C/R vs timing

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Jun 9, 2004 | 03:20 PM

JZ'sTA

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From: Ft. Myers Fl

C/R vs timing

I still haven't figured this whole timing vs compression thing out yet.
My question is.......
When using 93 octane only how much compression is too much before you start to have to pull a ton of timing?

An example would be....... say you have 12:1 C/R and therefore you can only run 18-22 degrees of timing with 93 octane. If you were to run less compression and more timing would you make more power?
Ex 11:1 and 28-30 degrees of timing.
Is there a point when too much compression on 93 gas is a negative?

Thanks

Jun 9, 2004 | 03:23 PM

Mike TexaSS

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From: Wish I was in a boat fishing...

About 12 to 1.

My 382 stroker is about 12:1 and i can only run 19-20 deg of timing or i get knock on pump gas.

Jun 9, 2004 | 03:29 PM

gomer

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From: The Confederacy

I run 30* and a little over 11:1 on 93 without a problem. I also run an electric WP, cooler thermostat, and TR6 plugs. If I'm going to be running the hell out of the car in hot weather or going to the dyno.. I mix in a little 100 octane unleaded for insurance. I've ran this way for about 15,000 miles now without a problem.

Jun 9, 2004 | 03:45 PM

FEAR THE LS1

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From: Hot Rainy Humid +2000 DA South Florida

I used to run 28* of timing with 93 pump gas on my old motor, H/C with 11.1:1 CR. When at the track I would run 32* of timing with VP 103 with 0 Knock Retard. I never got to dyno the difference but the car ran faster with the higher timing and better gas. I wasn't able to get more than 29* before I got KR on pump gas.

Its amazing what some high octane unleaded gas will do for you at the track if you tune the car right.

Jun 9, 2004 | 05:54 PM

Linear Velocity

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From: Huntington Beach, Ca

Quote:

Originally Posted by JZ'sTA

An example would be....... say you have 12:1 C/R and therefore you can only run 18-22 degrees of timing with 93 octane. If you were to run less compression and more timing would you make more power?
Ex 11:1 and 28-30 degrees of timing.
Is there a point when too much compression on 93 gas is a negative?

Thanks

Jeremy, the way it was explained to me by some tuners here is that you would make roughly the same power with a 12:1 CR and 18-22 of timing as you would with 11:1 with 28-30 of timing; given everything else would be the same. Where you'd have the advantage of making more power would be with a 12:1 CR and 28* of timing and some 103 octane. My 388 was a 12:1 CR and we have crappy 91 octane out here, I ran a street and a race tune though; 16* of timing on 91 with no problems for the street, and 26* of timing with 103/91 mix with no problems for race/track applications; this was with a stock water pump, 160* thermo, and TR6 plugs. Hope this helps.

Jun 9, 2004 | 06:17 PM

JZ'sTA

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From: Ft. Myers Fl

Quote:

Originally Posted by Linear Velocity

This is more of the kind of answer I was looking for.
I guess I didn't word my question very well.
Basicially what I am trying to figure out is...... "when is higher compression too much?"
I am only talking about 93 octane fuel here. Pump gas
Let take a H/C car for example.
Say the car makes 420 to the wheels running 11.1 compression and 28-30 degrees of timing.
Now you pull the heads off and mill them to 12.1 compression. Put the heads back on and retune. Now you have to pull timing out because you are running Pump gas and are in the 18-22 degree area.
Will you make any more power due to the added compression but less timing?

My tuner wants a friend of ours to take his everyday driver NEVER track raced Z06 up to 12.1 compression.
I say it is a waste of time and money due to the fact you will have to pull timing canceling the added compression.
I just want to get other oponions.
Thanks