Best compression for street/strip car?

BlownStangGT

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#1

• Mar 13, 2004

• #1

What would you guys think would be the best all around compression for a street/strip car that might spray nitrous? Would 10.5-1 be good or even 11.5-1 or is that to muhc for a mostly daily driven car? Assuming that there is always 93 in the tank

 

BlownStangGT

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ttt

 

A

autoXr1

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#3

• Mar 14, 2004

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Whenever you combine pump gas and forced induction, you may be quite limited to what you can do with compression ratio. Typically, something around a stock (9.5-10.5:1) is about where you want to run. You may be able to run a bit higher IF you get a two program chip burned for the engine. Basically, it comes with a switch/button that changes the programs from one to another when you are on/off the spray. It is best to have a professional dyno tune it with a wide-band O2 sensor and laptop. Either way, if I were going to run boost, I'd get custom tuning anyhow, just for safety sake. Pay a little now, versus a lot later.

Just me....

 

5.0 HOtrain

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• Mar 14, 2004

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There is alot of varialbes, timing, cylinder head desing, ect... I'm at 11.25:/1 with the 418, that ran on pump gas on the dyno, ran great.

 

PURESTREET5006

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In the tech line for tear down"AGAIN"

Mar 14, 2004

#5

• Mar 14, 2004

• #5

11 to1 with aluminum heads and 10.5:1 with iron but it all depends on if your car is daily driven or not? and if your in stop & go traffic...I had 11 to1 on my GT40 (iron headed) motor 2 seasons ago and i would drive it around sometimes but i was never in stop & go traffic.

 

408stroker5.0

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Mar 10, 2004

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Mar 17, 2004

#6

• Mar 17, 2004

• #6

For a street car I wouldn't go any higher than 11:1 just to be on the safe side. I run 10.8:1 on my mostly street driven 408 without a problem. Having a Manual also helps a bit to. (Less chance of detonation or luging the motor)

 

The Communist

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The graveyard of tomorrow

Mar 17, 2004

#7

• Mar 17, 2004

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But doesn't higher compression create more toxic emissions such as carbon monoxide etc?

 

J

jjd975

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Mar 17, 2004

#8

• Mar 17, 2004

• #8

BlownStangGT said:

What would you guys think would be the best all around compression for a street/strip car that might spray nitrous? Would 10.5-1 be good or even 11.5-1 or is that to muhc for a mostly daily driven car? Assuming that there is always 93 in the tank

Click to expand...

Is this for your current motor or another one?

I wouldnt waste the time to pull the heads and mill them down for a point or two of compression on that motor. IMO it would be a waste. Not to mention it would keep you from being able to run much/any boost with those heads unless you spent some real cash on pistons.

 

stangboy

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Mar 17, 2004

#9

• Mar 17, 2004

• #9

Speaking of compression ratios. I'm about to put a set of AFR 165s w/58cc chambers on my stock shortblock. Anybody have an idea about what my compression will be when I put the heads on? I haven't done a compression check yet, but I was wondering what it might be. I'm gonna do a compression check before I take the stock heads off and after I put the AFRs on.

 

stangboy

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#10

• Mar 17, 2004

• #10

I noticed a couple of yall mentioning "if he puts boost(forced induction) on the motor"...nitrous isn't forced induction. Actually you get better results from nitrous with higher compression, but of course there are other variables to go along with that.

 

J

jjd975

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#11

• Mar 17, 2004

• #11

stangboy said:

I noticed a couple of yall mentioning "if he puts boost(forced induction) on the motor"...nitrous isn't forced induction. Actually you get better results from nitrous with higher compression, but of course there are other variables to go along with that.

Click to expand...

When I say boost I'm talking about boost, not nitrous. I might not have made that clear though, not sure.

I'm saying if he mills these heads down a bunch he will more or less ruin the chance to run a blower with them. I know he says he wants to just run nitrous but we all know how that goes. Never say never.

In the end I just dont think it will worth all the time and cost to gain a point or two with this motor.

 

stangboy

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#12

• Mar 17, 2004

• #12

jjd975 said:

When I say boost I'm talking about boost, not nitrous. I might not have made that clear though, not sure.

I'm saying if he mills these heads down a bunch he will more or less ruin the chance to run a blower with them. I know he says he wants to just run nitrous but we all know how that goes. Never say never.

In the end I just dont think it will worth all the time and cost to gain a point or two with this motor.

Click to expand...

I wasn't trying single you out, jjd975. I just thought I'd mention it because someone else mentioned forced induction also and the way he stated it made me think he thought nitrous was forced induction. I was just letting people know that nitrous isn't forced induction just incase they thought it was. It IS a power adder but its not forced induction like a supercharger or turbo charger.

 

M

matm347

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Aug 29, 2000

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Mar 17, 2004

#13

• Mar 17, 2004

• #13

Higher compression does not ruin the chance at a boost, just not as much of it. I'm seeing more and more cars run higher compression (11:1) with ~18psi instead of 9:1 with 24+psi. This has the advantage of having a better bottom end, and lets you run less boost(which is more efficient due to the heat/power it takes to make the boost). I’ve seen this on all out race cars running high octane, but on pump gas an 11:1 motor will run fine under 10psi, and would be quicker than a car with 8:1 with 14psi.

 

bmo37

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Mar 17, 2004

#14

• Mar 17, 2004

• #14

had my stroker built to 8.5:1 compression cause i plan on adding 10-12 psi of boost down the road, all depends though, n/a i'd say 10.5:1 is good for street/strip and 11:1 and up for strip only, not until they start selling 107 octane at the local pump.