[SSandman]

Running higher octane (slower burning) gas can lead to unburned fuel fouling plugs. Running leaded gasoline, as it was stated his race gas is, is also not recommended in a stock LT1.

I never really got the idea that race fuel 'burns slower'. Higher octane resists detonation better than lower octane, that is what octane is essentially a measure of. But how does that have any affect on burn speed? I always figured perhaps this is flatout untrue, as octane rating itself, as defined, has nothing to do with burn speed, but maybe lead vs unleaded affects the burn speed?

 

[SSandman]

It does that by......ok.......ready for this.......burning slower .

KW

No, not necessarily. Could it be possible that a given fuel can resist spontaneous combustion at a specific compression level, thus being able to be used in a high compression motor; but have the same rate of 'burn' from start to finish as a lower octane fuel (when both are tested at the same compression, one that is within the lesser octanes fuels ability to resist detonation).

Being that 'octane rating' does not actually mean the amount of octane in a fuel, it only means how that fuel compares to a percent of iso-octane and heptane mixture in regards to how much pressure it can resist before spontaneous combustion, it seems that you can have a variety of different ways of making a say '105 octane' mix and because of this there could be varying characteristics in the rate of burn.

I don't really know that for sure, im just sayin. I would really like a chemists explanation. I might try to seek one out.

 

[SSandman]

I'm not smart enough to say that it's not possible.

But from all that I've read......I'll say that your supposition doesn't make sense.....since ignition and burn (combustion) rate is supposedly tied to octane rating.

KW

If octane rating somehow takes into account the 'speed' of the burn somehow, some way, then I am definitely wrong, but all I can find are generalized descriptions of how the octane rating system works and most of them just say something along the lines of 'a fuels ability to resist detonation as compared to mix of iso-octane and heptane'.

question is, can a distinction be made between the ability to resist detonation and the rate of burn or is it one and the same. Can you have two fuels that both resist the same amount of pressure before spontaneous combustion, but one burns faster or slower than the other? Or is the speed of burn the only contributing factor as to WHY the fuel resists a particular amount of heat/pressure before spontaneous combustion. I am in the same boat as you, I don't know nearly enough about chemistry to understand. I am curious though!
btw, when did you turn 90?

94SS man, to add to what KW said, I would also say that if your tuner tuned the car on a mix of race fuel and 94, and you are now driving the car on pump gas...that could be a problem in and of itself if your tuner didn't leave a lot of leeway for pump gas. There are plenty of unleaded race fuels out there if you wish to run it, it's just a little harder to find than leaded. I know my shop only sells leaded but shops that build a lot of imports may have a supply/supplier for unleaded.

 

[SSandman]

just to clear it up for some

pre-ignition is just that, the fuel igniting BEFORE ignition ever occurs.

detonation aka ping aka knock is when the fuel does not burn nicely in a cascading fashion with the oncoming flame front, but instead it starts spontaneously combusting as the flame front moves (i.e; lets say fuel at the end of the line starts to burn before it's turn). But this all happens AFTER the spark plug shoots spark.

detonation=bad
preignition=very bad


I think the bottom line of this thread is,

1)leaded fuel=NO GOOD FOR COMPUTER CONTROLLED CARS WITH 02 SENSORS
2)high octane WONT give you an increase in performance IF your car is tuned for a lower octane UNLESS you are seeing knock retard from an overly aggressive tune

that pretty much states it. It's pretty simple really. If you have an aggressive tune and a high compression motor, hook it up to a scanner when you run and see if you are getting any knock retard. Run the car with some high octane UNLEADED if you wish and see if knock count goes down and knock retard goes away. If so, using race gas is a benefit for you. For most of the guys on this forum I would gather, using higher octane fuel than what they are tuned for would be useless as most guys here aren't pushing the limits of pump-gasable dynamic compression or super aggressive timing curves.

If you aren't geting knock retard but you think you can get more out of your car by using race gas, put some in and have it tuned. If you can get more power before she pings with the race gas, then you've found a reason for it. But as many already know (but yet some MECHANICS I have met STILL don't get) putting high octane fuel in your bolt ons, stock motored car is going to do NOTHING.

 

[SSandman]

The thing with higher octane fuel is that it burns slower, which in hand burns more complete. Something how the higher octane fuel ignites faster and hotter than lesser octane fuels, which is how it burns more complete.

I can agree with wasting money, but as said, Slower more complete use of fuel can also help in fuel economy slightly. It also burns much cleaner than lower octane fuels as well.

you may want to read the last few pages of debate, along with the quote Bob with 3 B's pointed out from Hotrod magazine. The 'burns slower' thing may not necessarily be true. Maybe it is, maybe it isn't. But one thing we can all agree on is that race fuel WILL either A) burn more completely or B) give off more energy as Hotrod states it. But either way, I don't think anyone will see much of a gain from this on a street car with a tune that works on pump gas. Maybe if you're looking for every last half of a tenth it's worth trying though.