I was just turned on to a local gas station which carries 100 octane racing fuel. Any fellow vette owners here who have put this high octane in their tank? Does this do any damage to the engine? I know this question has been asked before and I checked the search engine but didn't find any info? Any info would be appreciated!!!!

 

It's probable leaded which will ruin your cats. If it's not leaded, it won't do anything unless the car is retuned for 100, then you'll need to run it all the time. Not worth the effort in IMHO.

 

He's absolutely right. Chances are it is NOT leaded. But you won't gain anything unless you're tuned for it.

My other car is a turbo and I used to have to mix some 100 in with the crap California 91 (more like 89) just to keep from knocking.

San

 

Thanks!!! I'll stick w/ 91 and be happy. Living in the Mile High city, you lose HP because of the altitude.

 

If it's unleaded, you could add a gallon or two to a near full tank for a boost, but I wouldn't run it straight. BTW, Spinmonster is right there in your backyard. He can probable get you the proper tune and advise you on the petro.

 

I used to run 4 gallons of 100 and 12 gallons of 91 to yield a full tank, 16 gallons of 93 octane. Recommended for max performance. I gave it up as it was just too much trouble, and minimal if any real increase in HP.

 

I'll have to look him up, I went to the local corvette performance shop here- http://vettepieces.com and had a Vortex Air Ram installed. It made a little difference in the performance sucking more air in.

 

You'll want to monitor that intake closely. It has the worst reputation of any IMHO for sucking in debris and deforming under normal operating conditions. Better yet, have your shop check it periodically if they recommended it.

San

 

I wish they sold 100 octane at the pump out here.

 

Cylinder pressures are lower as you climb in altitude. 91 octane at my 6800 foot elevation runs a 94 octane tune from sea level. I was tuned to the line at sea level in NY. When i moved to Colorado my car ran 91 with no sign of KR. I was actually able to run 2 more degrees timing with the 91 than with the 93 tune.

Octane slows the burn rate. There are so many different variables to deal with to make such a simplistic comparison as I'm about to do but here goes: A slower burn rate will yeild less HP than a faster burn rate so the 100 in the mix here would likely produce less HP than straight 91. As I said there are a ton of variables so comparing company X's 91 to the burn rate of Company Z's race gas isnt accurate but the same company, same pump gas, 87 burns faster than 91 and its 91 would burn faster than 100 because ocatne is burn control or knock control. Powerlabs actually works with these forumlations as employment so he would be better to expalin it.

If you want a boost, get meth injection-single nozzle, and have it trigger at .48 engine load (Kits like the alky control one use a voltage signal from a MAP sensor to trigger; using a stock MAP for the voltage signal hits the meth for about 1/2 throttle) and it will be like running 116 octane and you retune for it. You will see 15HP and it costs 7 bucks a month if you use it. While at cruise on the hiway or idling at traffic lights, you arent burning high octane race gas. Meth kits with a downstream IAT sensor allow you to vary timing if the kit is spraying or not so a failure wont run more timing because the IAT's fall spraying the meth.

I set up nitrous cars this way.

 

Spin, I thought this was exactly the opposite. A slower burn rate is advantageous because there is more power to be made by a "controlled" rate of explosion and power made throughout the piston travel.

The way it was explained to me was that you could liken high octane to a rifle shot, in that the power was very controlled. Low octane could be likened to a shotgun blast, where it was very explosive but the blast was uncontrolled.

A high octane explosion would push the piston completely through the stroke due to the controlled and uniform (slow) burn. A low octane explosion would provide less power as it would burn too quickly and possibly pre-ignite.

If I missed something here please let me know.

San

 

When octane increases its less subject to accidental ignition....harder to ignite. With a given timing setting, the minimum octane to control the ignition of the mix produces the best power.

Different formulations can have more power than the next when ignited yet have the same octane rating.

As I said before there are far too many variables for such a simplistic explanation. Flame spread, flash point, octane, ect are all variables and affect potential energy independently.

I am not a fuel expert and can be wrong.....and I'm sure a guy or tuner who never starts threads of their own will be more than happy to chime in an correct the guy who always starts threads and tries to help because thats all some do. Sales being the number one post and the next best would be to make the competition look bad. They are the ones with 42,845 posts but only 3 threads started...heh. LOL, I posted once (not knowing that C6's actually can come with real chrome wheels) and 7 screen names I never saw before jumped on me to rear rape me saying the chromies are a dealer option. You never saw those screen names before and never will again until you take a chance on posting. Anyway, my info comes from the firefighting days with the Port=Authority Police when were training to put out jet fires and learned about the properties then went out to actually extinguish the fires started with the respective types of jet fuel. So I have my flame suit on for the harsh delivery of that guy or tuner that only posts to 'correct' someone with an overtone of 'Spin you idiot, thats not right'.


Joking aside: using higher octane on a car tuned to lower octane dyno's less. I see that all the time.

 

I think your above statements contradict each other. "Octane slows the burn rate". Agreed. Thus a slower burn rate (higher octane) produces more power than a faster burn rate (lower octane), right?

I think if your sentence in the above quote said "A slower burn rate will yeild MORE HP than a faster burn rate....." all of the above would make sense. Agreed?

San

 

No. I do not agree that slower burn rates make more power. (I dont know if the the term burn rate is even the right term) Its harder to ignite. If your Honda is optimized for 87 octane and you dump in a tank of 93 it dyno's less. I've seen it over and over again. It is harder to ignite. Is that burning slower (where I get the term burn rate). When we used the term in putting out jet fuel fires they said that the military fuel has a wild flame spread and low flash point making much more power. You could walk off the comercial jet fuel before the flame would spread to where you were standing (I actually did this with a fire entry suit on to put the fire out) and the military stuff spread faster than you could run. Fast spread = more power (JP4) and slower flame spread made less power (comercial jet stuff). I take flame spread to mean rate at which it spreads or burns and dont know if that violates the industry term for fuels. Why does the militatry use that and not the slower flame spread stuff.....because it packs way more power. Thats in no way implies faster burn and more power of the miltary stuff was higher octane....its actually lower.

Now I dont recommend it but I think if a puddle or 87 and a puddle of 100 octane were both on the ground and ignited, the 87 will burn up faster than the 100. Here's a question....which burns hotter? (I dont know) Hotter may be a better check on power and would be interesting to know. It could burn hotter but slower. Hotter would suggest more power and prove me wrong.

I want to reiterate that one company's 95 may very well make more HP than another's 91. There are other variables.

What caused the Honda test was that a friend's parents told their son to not use the 'cheap stuff' in the family's Honda. They thought cost = quality and I said the car is optimized for 87 they should use 87 and it didnt mean it was lower quality. When I said 93 in their car would result in less power since it was harder to ignite, they disagreed. Since Jr already filled up with 87, we dyno'ed the car at Lizzard in Long Island NY. 155HP, when it was used up, they filled up with 93--the good stuff, same dyno....146 to 148 on 4 pulls.

OK, I PM'ed Powerlabs and will go by his answer so I will let this one alone till he chimes in. Then you can say Spin is wrong cause Powerlabs said....

 

Hi guys,

First things first... My job is as an Alternative Fuels Research Engineer, so most of the work I do has very little to do with Gasoline. My educational background is also in Mechanical Engineering, not Chemistry, so I am by no means the authority when it comes to the finer details of fuel composition. I don't know what forum member glass_slipper does for a living, but he seems to know more about fuels than I do.
That said, Spin's answer to the OP's question is correct: That 100 Octane fuel is most likely not leaded (they sell 100 Unleaded at Sunoco stations around IL for example), but it will not provide any power gains on a car that is not tuned specifically for racing gas and may very well cause the car to lose power. Tuning the engine for racing fuel would open the door for power gains, but also make the engine dependent on race gas; it will detonate.

I will leave jet fuel out of the octane discussion, because Jet Fuel has no octane rating per se. Jet fuel is comprised mostly of Kerozene, which is chemically analogous to Diesel. You can, in fact, use many types of Jet fuel on Diesel Engines.
JP-1 is the common aviation jet fuel; it is 100% Kerozene. JP-4 is a mixture of Kerozene and Gasoline (50-50). Since 1996 modern military jets have been flying JP-8 which is also 100% Kerozene.

Now, understanding what the Octane Rating means: Octane Rating for Gasoline fuels is determined by running the fuel in a special engine called a CFR (Cooperative Fuel Research); that is a single cylinder variable compression engine; the simple explanation to how this works is that the compression ratio is raised as the engine runs by turning a hand crank, and the CR at which the fuel begins to detonate determines its Octane rating.
So, in other words, Octane is a measure of a fuel's ability to prevent detonation. That is why you can stand to gain power from high octane fuels; you can run more compression, more boost, leaner AFRs, and more Ignition Timing before knock onset.
What makes a fuel high octane is typically a higher proportion of large hydrocarbon molecules, which are more difficult to break apart; those fuels do typically have lower flame propagation velocities, but there are high octane fuels that have fast flame speeds; a lot of it can be controlled through additives.
Energy wise, high octane fuels are typically higher density, but lower specific energy. Case in point: 87 octane gasoline is about 125,000BTU/Gal and 100 Octane is 120,200. That is one reason why you can lose power running high octane fuels on an engine designed and tuned for low octane.

Hope this helps

 

On a very cold morning, when the c6 seems to have more power, throttle response in crispier and the exaust note in more agressive, that is what I experience with Sunuco 94 octane compared to 91 or even 93 octane octane in any brand. My car was tunen on 94 octane. The chemical reason for this, I have no clue, however the car is quicker, I can feel it and I can hear it. As an added note, it is on these cold mornings that my car, as Leon would say, rocks. At idle it will shake in cold weather.

 

To emphasize the fact that higher octane gasolines are slower burning, I had a friend years ago with a hotted up Ford V8 Flathead. He was able to get a tank of 130 octane AvGas, hoping to make more power, but unfortunately only burnt all his exhaust valves.

 

The drop in performance is enough to measure. I ran out of fuel at the track one time and had to use 100 octane (might have been 98) and my ET and trap went down. Add to that the fact that was 2x the price of pump gas, I no longer to try to save the last 20 - 30lbs by showing up with an 1/8 tank.

 

That is very interesting. I wouldn't expect it to be measurable like that.

 

You are right aviation gas is 115 or 130 and for the best part of it most
aircraft run 13.5:1 compression. That would make sense.I know JB is
big on the torco attitive to boost to 100 octane. I presume he tunes for it.