oufan2929

Just like the title says. I'm curious as to how high of a compression ratio I can have to still be able to use pump gas on a daily basis. I was guessing 11.5:1 or so. Is that too high?Thanks--Andy

LS1_PNYTAMR

iTrader: (1)

i heard it was more like 10.6:1 or 10.8:1.. even then i heard u still may have to run 95 octane or some octane booster to keep it from knocking. i could be way wrong though, cuase i see an awful lot of ppl running 11.x:1's on here.

GuitsBoy

iTrader: (4)

A large cam will bleed off compression, even though youre actual ratio is high, youre compressing less air because of the overlap.

Race Car Driver

11:1 is the consensus.

SAM98WS6

I am 11.7:1 on 92 octane...but with a large cam.
I think 11:1 is the consensus too.

TigerFan187

iTrader: (1)

I was just asking the same thing. I just put a LS1 in my truck and Im running the truck heads and intake. My comp ratio is 11.2 and I wanted to make sure I was ok. I run nothing but 93 octane and I dont have any audible knock and I will be scanning this weekend. I did a cam swap in my 4.8 a week before I blew it so I used the same cam for the LS1. Its the comp 212/218 .522 .529 114LSA. The truck heads are completely stock and the mods below are current. I really need some opinions on this. Also If it would be safe to go ahead and use some octane booster which should I use and are there any negative affects from using it. Thanks for the help.

jz06man

You can run 11.5, but as stated with a large cam or cam with an overlap of 50 or higher...

If your'e not running a large cam, you can compensate with coatings on the pistons, valves, etc... You need to run a cold air intake as a min and change the thermostat to a 160... For every 10 degrees of water temp below 210, you can add .1-.2 compression...

You can forget about these octane boster- they are a waste of money...

black_z

iTrader: (4)

Overlap of 50. A TSP 233/239 only has 12* of overlap. And thats a fairly large cam.

jz06man

I'm calculating it at advertized duration.. You can calculate at at advertized or refer to ASA which is what you speaking of...It's the same, except from a differance point of view.. From your point of view, you are correct, then i would look for a cam -4 to 4.. A 224/224 with a LSA 114, is 224+224/4=112-LSA114=-2*2=-4.

A cam with an overlap/ASA of 12 is a fairly large cam and will rock or idle roughly.

A Z06 cam has an ASA of -28 and it's a nice cam- As least of a stock Z06 or LS1's looking for a nice upgrade..

jrp

iTrader: (16)

my SCR is 12.02 and i plan to run 91.

git_sum

iTrader: (10)

Last i heard you could run a lot of compression like 12.5:1 and up and still run pump gas with the help of somethign called a timing tuner.

hellbents10

iTrader: (10)

Right it just become non benificial after you start taking to much timing away to stay away from detonation. Peak downward force on the piston is not taking place at the optimal time. With a good 25 degrees of overlap. Like the t-rex you could run up to 11.5:1-12:1 with good cold air and coolant. There was guys in the engine masters challenge running more then 12:1 with 92-93 oct. Good reading. Lots of coatings and polishing the combustion chambers to stay away from hot spots. The proper cam selection. A lot of them were detonating and still making good power.

Eye

I run 11.5 to 1 with a stealth 2 cam.I run a tech line coating on the chamber.I have no detonation even though i still have the stock ss exhaust in place. Thats with sunoco 94 though.

TigerFan187

iTrader: (1)

I have the CAI and the 160 stat and will have the LS1 fans on soon. The cam I have in the LS1 is the same cam I had in the 4.8 for a week before I killed it(the 4.8) so i know there is plenty of room for a bigger cam. What is the overlay on the cam I have( 212/218 .522 .529 114LSA)? So I should be cool on 93 octane correct? So booster is a waste? Thanks for the good info!

Bill's 02 Z-28 SS

Hi Folks
I am running 11.2:1 CR on 93 without a problem. I have raised the timing during WOT to 29 and still not seeing the Knock sensor. Would it run better with higher octane gas, probably would but it OK the way it is.
Bill

jz06man

I have the CAI and the 160 stat and will have the LS1 fans on soon. The cam I have in the LS1 is the same cam I had in the 4.8 for a week before I killed it(the 4.8) so i know there is plenty of room for a bigger cam. What is the overlay on the cam I have( 212/218 .522 .529 114LSA)? So I should be cool on 93 octane correct? So booster is a waste? Thanks for the good info!

__________________
Your overlap is 212-218/4-114*2=-13 ASA. You fine !!! What i your compression?? I'm at -10 with my cam and 11.21 compression and i run 93 octane.. Do not expend/waste your money on octane booster.. instead use a fuel/head/valve cleaner every oil change or 3K miles, too fight off carbon deposits.

TigerFan187

iTrader: (1)

What brands do you recommend on the cleaners? Thanks for the help!