Gas Question, What effect?

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Coyote Jack

Coyote Jack

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I have a little better than 10.5 to 1 compression with my LA/Magnum hybred. I don't have any pinging with 16 init and 34 total timing running 91 octane. What I am wondering is, what effect would running 100 or even 112 octane race gas have on power? I'm not worried about fuel milage as the diffence in price would more than eat up any mileage savings.

Jack
 
Once the octane requirement of an engine is met adding more octane has no power advantage. Octane is not a power adder in itself. It will though, allow you to add more compression, boost, advance curve etc. which will add power. The octane rating of a fuel is nothing more than it's ability to deter detonation.

Plus there is lot more to a race fuel than just the octane rating. There can be multiple types of 100 octane race fuels from the same manufacturer. Some race fuels have a slower burn rate than others so if you put one of these slow burn rate fuels in your car without the components to support the slower burn fuel, your car could actually have less power than with the pump gas.


Chuck
 
If it doesn't ping on 91 it won't ping on 100............. and it won't make more power either.


Thats just how it works.
 
Actually you'd make less HP with high octane gas. The higher octane slows down the burn to stop detonation. It also slows down the burn during combustion, hence, less horsepower. If you aren't detonating with 91 octane you dont need anything higher. You might try 89. If it doesn't detonate you might make a couple more hp and save a few bucks to boot.
 
Those answers are to the point. I am no fuel scientist, that's why I asked. Looks like I will step down a grade and see what happens.

Jack
 
Coyote Jack said:
I have a little better than 10.5 to 1 compression with my LA/Magnum hybred. I don't have any pinging with 16 init and 34 total timing running 91 octane. What I am wondering is, what effect would running 100 or even 112 octane race gas have on power? I'm not worried about fuel milage as the diffence in price would more than eat up any mileage savings.

Jack
Click to expand...

That's exactly what I just timed my 9:1 '92 Commando 360/300 to. Funny, I used to hear that 36-37 total was optimum for these engines, but that seems just too much for mine. But I would think you'd get pinging with 10.5:1, unless you had aluminium heads. You sure you are not?
 
dartley,

Absolutely no pinging. Throttle response is very good. I have an all MSD ignition, 6al and dizzy if that makes any difference. The cam I have does bleed off some pressure so I would think that that would help. I also have very good quench with the magnum heads and 0 deck pistons.

Jack
 
Coyote Jack said:
dartley,

Absolutely no pinging. Throttle response is very good. I have an all MSD ignition, 6al and dizzy if that makes any difference. The cam I have does bleed off some pressure so I would think that that would help. I also have very good quench with the magnum heads and 0 deck pistons.

Jack
Click to expand...

Thanks for the info. Don't know what 6al or dizzy is though. Is the MSD really better than the Mopar Orange box?
 
On a low compression engine, or with a higher octane rated fuel you can actually advance the timing past the point of peak power without audible detonation.

Octane actually has no bearing on the rate at which a fuel burns. Octane is a reference hydrocarbon, and your "octane number" is an index which describes a fuel's resistance to detonation in a reference engine (a specific ASTM design in laboratory conditions) The actual percentage of octane in the fuel is in no way related to the octane number. Furthermore it is the caloric value of the fuel, that is the heat energy contained within it, which cause an increase or decrease in power. Some racing fuels are blended to make more power, for a given octane number.

Heck spend a couple bucks on the expensive stuff and see if it makes a difference. I wouldnt expect too much however.
 
C130 Chief said:
On a low compression engine, or with a higher octane rated fuel you can actually advance the timing past the point of peak power without audible detonation.

Octane actually has no bearing on the rate at which a fuel burns. Octane is a reference hydrocarbon, and your "octane number" is an index which describes a fuel's resistance to detonation in a reference engine (a specific ASTM design in laboratory conditions) The actual percentage of octane in the fuel is in no way related to the octane number. Furthermore it is the caloric value of the fuel, that is the heat energy contained within it, which cause an increase or decrease in power. Some racing fuels are blended to make more power, for a given octane number.

Heck spend a couple bucks on the expensive stuff and see if it makes a difference. I wouldnt expect too much however.
Click to expand...

Thanks for the info, but I was just surprised that he could run 34D @10:5 w/o alum hds. I do know that a big stick and better quench will help though, just as he mentioned.
 
C130 Chief,

I tried the mid-grade gas yesterday. It is 89 octane here, probably comparable to your 91 due to the diference in the way they are rated from country to country. Still no pinging and as you thought, I couldn't notice a change in performance.

Jack
 
All I know is my gas has the effect of making the wife run for the hills!!!!

:)
 
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