Glenn

Has any one ever seen a dyno showing the difference in hp and tq going from reg 87 gas to 93 gas with out doing a tune or reprogram?

The Reverend

My dyno tuner said that the premium gas tells the computer to go into a higher table of some sort. There is a difference, I am guessing 5-10 hp.

Error404

without a tune, I wouldn't expect much of a difference. I have heard (only heard) that if you use an octane to much greater than what the car is tuned for, it's actually going to hinder the performance/economy a little bit. Not sure how accurate that statement is though.

Modular81

Running two points higher octane than what the car is tuned for shouldn't hurt anything. I would think it would ensure that your knock senors want pull any timing for bad gas since you're running say 89oct on a 87oct factory tune. This way you are always seeing your full amount tiiming that was intended.

LEO_06GT

It's not going to hurt your car to run 91 but I wouldn't expect a performance difference unless the car is tuned for it.

goldenpony

I have read that without a tune, preimum fuel is good for about 5 HP. Come to think of it, that's almost as much as UDP's.

metroplex

If no knock is detected, the spark is advanced by up to 2 degrees at the high end and if knock is detected, up to 5-8* of timing is pulled.

SlamMan02

Hopefully this won't come off bad, but that information is wrong. Without any tune, a properly running car will not see any difference running with a higher octane gas than is required in the car.

Error404

I think there needs to be proof of this. I was just stating what I had heard (and I mentioned that it might not be accurate). It sounds like you are sure of yourself, do you have dyno proof or some other type of evidence that shows this? I'm not trying to call you out, I'm just curious as to how you know this (and why you aren't mentioning how you have the facts?)

The guess that if the engine doesn't sense knocking it won't retard the engine, sounds plausable to me. Has anyone ever done dyno tests on this? My guess is that even if there is a difference, it won't be noticed. However, I wonder if there really is any difference at all, that an engine or chassis dyno could detect?

SlamMan02

Without the engine remapping itself to take advantage of the higher octane level there will be no increase of horsepower, IF the car is running properly.

LoL I don't know HOW I know this, but it might just be growing up being a third generation car guy.

metroplex

With the factory calibration, if no knock is detected, the spark is advanced by up to 2 degrees at the high end and if knock is detected, up to 5-8* of timing is pulled.

So theoretically you could gain up to 2-4 hp by running 93 octane if you used bad 87 octane gas.

Glenn

I have always heard its worth a few more hp to run 91 or 93 oct. People tend to get better mpg's with higher oct gas. Oh well just wondering if any one has done any testing of their own.

touring

i wonder how many threads are just worthless

SlamMan02

I wonder how many posts you'll make that are equally worthless

fordboy97f150

my f150 gets better millage and flat out runs better on midgrade but premium it has a negative effect

LEO_06GT

Glenn

I wonder how many of your posts are worth less..... well not really. I am sure all of them are

Glenn

hey I just said that

metroplex

I used to run 93 octane gas with a SCT 93 octane tune in my 00 Vic. All it did was waste my money. I got the worst gas mileage ever: 9-10 mpg in the city but highway was still the same (no higher than 20). With better tuning, I was getting slightly better gas mileage using 93 octane gas but after Katrina hit and the gas shortages/price spikes started, I switched to a 87 octane tune and started running 87 octane. I didn't get any hit in gas mileage, nor did I notice any loss in performance on the street.

Again, the biggest reason WHY some people get "more horsepower" by running 93 octane is because the Knock Sensors do not detect knock, thus the PCM advances timing by a pre-set amount resulting in a slight increase in performance.

93 octane is simply more knock-resistive than 87 octane. The way it was explained to me was that 93 octane burns more slowly than 87 octane. Gas quality has nothing to do with the octane number.

thump_rrr

My best run 100% stock was 13.651 @ 103.2 using 87 octane
Since getting my C&L intake I always run 94 octane.
One day I decided to do some back to back testing and these were the results.
The Density Altitude was comparable and even with 94 octane in the tank I was not able to equal my best time 100% stock.

http://forums.bradbarnett.net/showpo...63&postcount=6

"3 runs were done with each configuration.
1/2 hour cool down time between runs.
The MPH is always high at that track by 2.5-3 mph.

I actually did back to back to back testing.
Stock VS. 93 Octane Diablosport Canned tune VS. C&L Street Kit and 93 Octane Diablosport C&L Canned tune.

The results were

Stock intake and stock tune 2.094 ft. 13.757 @ 102.630 mph.
Stock intake and Diablo 93 octane tune 2.041 ft. 13.535 @ 104.577 mph.
C&L Intake and Diablo 93 octane C&L tune 1.954 ft. 13.274 @ 107.453 mph.

The car went on to run 12.95 @ 103 on the brakes with BFG Drag Radials later the same day during eliminations.