The Truth About Fuel.

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5thGenLuvin

Senior Member
I have seen alot of people saying that you have to drop your comression ratio way down when doing a turbo setup... From research I have found this untrue, correct me if I am wrong. I am building a LSblockC1headTurbo and have been doing alot of research. It seems the only thing that higher compression ratio is going to do in a turbo setup is cause knocking in your firing chamber due to gas self-exploding prematurely during the compression cycle. But would raising your octane significantly, say to 98-100 range completely eliminate the knocking due to the fuel now being able to handle a much higher compression and allow you to go high compresion and hihg PSI together? Yes it's expensive to fuel 100 octane on a regular basis, but for a drag car as apposed to a daily driver would it not be worth it?

I thought this belonged in Engine Buildup category moreso for the fact that is my calculations prove correct, this could be an excellent thing to think of when building an engine. Imagine 15PSI 10:1Comp and Vtec working together. Oorah.
 
you are right...all a low cr allows for is easier tuning...
http://www.csgnetwork.com/octaneratecalc.html
http://www.vpracingfuels.com/vp_01_fuels.h...28825#specialty

i am planing on building my rex (track only) with 10.5.1+/- cr... the reason behind that CR is tthat i'll be turbocharging and implementing a 2stg nitrous system. and the fuel needed might beVP Nitro 100â„¢ or VP Nitro 85â„¢....

however this is just an idea i have, the funds needed for this type of application are huge for me at this time.....

but you're on the right track
 
well you drop compression to run pump gas. I don't know where your gonna find 100 octaine at a decent price. For a track only car then do it, if you plan to run on the stree then its not pratical
 
For a dd I don't think I would want to always go out of the way to get 100 octane gas all the time. Regular pump gas would be more practicle.
 
No KS...thats pushin it a bit aint it....hope your using an octane booster in every tank.
 
For an all-out drag car, it would totally be feasable. Check your local drag strip though, I've only seen 100+ octane in a leaded formula, and I'm sure about the regulations for using leaded fuel at the strip. I'm sure you'll be fine though. High CR + Boost = approaching F1 status as far as how engines get built. Just think you get the responsiveness of an NA engine with the higher top end of a turbo. I'm thinking of doing it to my acura once I have an other daily driver.
 
actually i think in ImportTuner they showed that the NOS octane booster gained 2-3 points in 16 gallons of gas.
 
its misleading, becuase yes it may add a few "points" but when expressed as octane it is only at most a few tenths. You know the whole x+y/z formula.

If you want to boost your octane level just add toluene :mrgreen:
 
there's a fine line....

when you go to a higer compression piston, you actually make the combustion chamber smaller, thus, letting less air in to mix with the fuel.

i'm still a firm beleiver in 9.5: for a street/dd car, and 10:1 for a drag car
 
i just called titan...they said that the most CR with high boost would be 10.5:1- 11:1....and using c16 fuel....
 
97CTR @ Oct 5 2005 said:
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reikoshea @ Oct 5 2005 said:
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hope your using an octane booster in every tank.
Click to expand...

you do know that octane booster is worthless right? it adds about a few TENTHS of a point on your octane level
Click to expand...

yeah off the shelf NOS crap doesnt do shit but Torco octane booster will turn 93 into 100+ depending on the concentration.
 
pissedoffsol @ Oct 6 2005 said:
Quoted post[/post]]
there's a fine line....

when you go to a higer compression piston, you actually make the combustion chamber smaller, thus, letting less air in to mix with the fuel.

i'm still a firm beleiver in 9.5: for a street/dd car, and 10:1 for a drag car
Click to expand...

Nope. When you increase the static compression ratio, you ARE decreasing the combustion chamber volume at TDC, but you are NOT letting in less air to mix with the fuel. The higher compression ratio creates more "suction" during the intake stroke, so you actually draw in MORE air than with a lower compression ratio.
 
Calesta @ Oct 9 2005 said:
Quoted post[/post]]
pissedoffsol @ Oct 6 2005 said:
Quoted post[/post]]
there's a fine line....

when you go to a higer compression piston, you actually make the combustion chamber smaller, thus, letting less air in to mix with the fuel.

i'm still a firm beleiver in 9.5: for a street/dd car, and 10:1 for a drag car
Click to expand...

Nope. When you increase the static compression ratio, you ARE decreasing the combustion chamber volume at TDC, but you are NOT letting in less air to mix with the fuel. The higher compression ratio creates more "suction" during the intake stroke, so you actually draw in MORE air than with a lower compression ratio.
Click to expand...

That isn't always the case either. It also depends on your cam timing settings. Sure, you are going to have a smaller pocket of air in the CC at TDC before the intake valve opens up, and so you will have less gas expanding as the piston pull at it on the downstroke, but chances are, you'll not be running stock cam timing on any turbo setup anyway. There are so many things to consider when building a race engine, that is why there are so many different teams all running different setups. No two are the same. 10:1 in a drag car is for sissies. :) j/p
 
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