qcar

I'm going to the track on Sunday in my stock 03 S55 for the first time. My friend recommends using a half tank of 100 octane.

I've heard racing fuel may slightly improve performance, but my question is, can it do any harm to my stock engine?

Thanks,
qcar

vinnyz

race fuel burns slower and prevents knock in the engine .. put it in day before running at track so ur ecu gets use to the higher octane ... but as far as hurting it no it wont just mix the 100 with some 93 u will be fine

Quadcammer

the car won't get used to anything at WOT.

It will serve no benefit (unless you are currently detonating) and may even cause a power loss.

Stick with good 93 octane and you should be just fine.

Carl Lassiter

Your sig doesn't say where you are but if you're in Cali then for sure mix about a quarter tank of 100oct with the 91. All stock high performance cars are meant to run on 93 so if your state offers that then I wouldn't bother with race gas. Just don't get it from Arco.

Quadcammer

Not true anymore. Many cars are tuned for at least 91 octane from the factory

Carl Lassiter

Are you sure? I know they can run on 91 with no problems but it was my understanding that in cars like the V10 M5 around 2% power is lost as the car would prefer 93.

Thericker

IDK why you are so insistent on denying this? I have run my SL w/high octane repeatedly, the SOTP & power delivery charcteristics are changed dramaticly over 91 ****, I also have documented gains on Dyno as it adapted to 95 mixure (91 mixed w/Torco or straight 100 from pump in LA) during back to back runs EZ 20 rwhp to be had on otherwise stock forced Induction car.


Stop blurting your flawed opinions as FACT, ask ANY prof tuner if High octane will show true perf gains on Dyno or @ 1/4 trk.

vinnyz

thank you .. cars from the factory are only tuned for 91 octane cause of west coast . but running higher octane only increases hp .. my car is almost 30 hp difference

Juice1979

On more than one occassion I have run my car on the same day at the track with 93 and then a 93/103 mixture. After the fuel mixed thoroughly every run with the high octane mixture was faster. do i have dyno proof no...but improved track times and trap speeds are enough for me to keep doing it when at the track.

Thericker

Yes I have NO doubt 25-30 hp can be had, just pointing out @ very least 20 hp is readily attainable... I know it would be hard to feel 20 rwhp on a 500+ BHP benz but the reality is driving character/power delivery is noticeably different.

ESP is muted almost entirely w/100 mix burnouts are literally uninterrupted vs straight 91 octane, power is cut w/ESP intervention almost instantly (even w/ESP OFF)

vinnyz

i feel the difference with 93 and 100 .. car gets very aggressive with 100 in it . plus like the way it smells lol

Quadcammer

ok, can any of you experts explain to me how the car gains power with the high octane fuel.

An internal combustion engine develops the most power on the fuel octane that is just high enough to avoid detonation, otherwise you end up with a lot of unburnt fuel. If you have your timing based on 93 octane, you run 93. If you have timing based on 100 octane, you use that. Its that simple.

Given that the car does not read from the 02 sensors during WOT, it has absolutely no idea what fuel is in the tank.

Its very possible that the car is pulling timing due to active knock sensors due to a combination of high ECT, IAT, or other factors, and that when you add the race gas, the detonation no longer occurs. (which is 100% consistent with my statement above).

For a car that is not detonating, race gas will not improve power. This is not something that can be argued.


Instead of all this "well real tuners know x, y, z", how about you show me some data. I've owned and datalogged cars that make the average e55 look like an E320, and none of them, if tuned for 93 made more power on 100, unless the knock sensors were active (which they shouldn't be with a decent tune).


Considering your argument, why stop at 100 octane? Why not 109? Why not C16? More octane means more power right?

Stop reading bull**** from all the expert tuners that can't seem to get a simple forced induction car to run properly and actually think for a minute.

AgSilver

Glad to see someone knows what their talking about. Only if it were all that simple.

Quadcammer

another thing I thought of.

Since the stoich a/f ratio of race gas is different than pump gas, its possible that the commanded a/f on the race gas would actually be a bit leaner, which should develop a bit more power so long as it doesn't detonate.


If someone shows me a datalogs of a car including a/f (properly set up for the fuel run), timing, knock sensor voltage, IAT, and rwhp/rwtq (to confirm its not detonating) for the same car on a 93 octane tune that is run on 93 and 100, and the 100 octane runs produce statistically significant improvements on a consistent basis (i.e. not one run where power is higher by like .5%), then I'll eat crow.

Hammer Down

Here is what you want to do. Go get some Sonoco 100 Octane 5gal then go and get 5gal of Cheveron 91 Octane and then put in a bottle of Techron and reset your ECU. You will need to do this about a week before you go to the track to give the car time to adapt to the 95 Octane that you are now running. You will have to drive the car fairly hard during this week before the track. When you go to the track make sure that you have no more than 5gal in your tank. You may have to get a 5 gallon container to keep some extra 100 on hand so you can do a 50/50 mix at the gas station after you run.

You can take my word for it or you can take it with a grain of salt but I am stock on drag radials and my car runs pretty good!

Carl Lassiter

Oliver, no one is saying there are gains to be had going from 93 to 100 unless specifically tuned for that. My point was clear and was that stock high powered cars in California suffer from 91 being the best available gas. They can cope with 91 without knocking etc but they are optimized to run on 93.

Forrest Gump 9

To the op, make sure the 100 octane gas you're getting is unleaded. Leaded race gas can ruin your O2 sensors.

As far as race gas will help you gain power, probably not. If your car tuned for 93 octane, and the only octane available is 91 from pump, then yes, adding 100 octane will help you regain the loss. But if your car is tuned on 93 octane and you just want to add 100 octane in there then that would be a waste. That money will be well spend on a couple bags of ice to help cool your car down.

Quadcammer

Carl, I think thats exactly what they are saying. They seem to think the car can adapt to race gas somehow.

As to your 91/93 argument, if the car is pulling timing due to pre-ignition or detonation, then yes, adding octane will help. If the car is not exhibiting any signs of detonation or pre-ignition on 91 octane, more octane will not do any good.

Hammer Down

I guess we are all entitled to our own opinion, what may work for me, may not work for you! On 91 Octane I went 117.7 and since I started mixing 101 & 91 I have trapped 118.61, 118.65, 119.22, to 120.15 and a best of 121.18!

Quadcammer

Sir, I think you are missing the CRUX of my point.

Your car may have very well been pinging or detonating in an imperceptible way (to the driver anyway), and once you added the higher octane gas, you gained back some power. That said, you are restoring power that is lost from stock, not making any more.

If you logged your car during these runs, and your knock sensors were never active, you may have a point. If you did so, please post the logs as I'd like to see them.

Marcus Frost

I agree with Oliverk except with one caveat: 100 octane will make more power than poor quality 91 or 93 octane fuel. This is again, assuming a tune that is either stock or done for a pump-fuel octane level with no ability to adjust itself higher (which, the 55k ME does not seem to do) I do not think straight 100 octane is ideal, rather for the way our ECUs are programmed there looks to be a "ceiling" around 94/95 octane. I, obviously, cannot verify that however it seems to be what I've seen.

I don't think there's enough data on the V12 platform to argue whether this also applies there. I have not run high-octane in my SL to verify/contradict this theory, so I cannot comment there.

-m

skratch77

im curious to see what 100oct will do,I am getting a retune for the 82mm tb soon,after that is done I will add 5 gallons of 100oct to our 93oct we have.

Ill drive it around for a day and then redyno,why do I get the feeling that it will put down more power once its adapted?hammer is trapping 6mph faster than most stock and even modded e55s,the gas has to be adding power

bassn_07

I totally agree with you on this Marcus. As you know I data log many different parameters during my trips to the track including AFR's and timing. I tried a blend of 100 and 91 to try and reproduce a 95 blend. Keep in mind this was Sunoco oxygenated gas. My timing advance 2.5 degrees and my AFR leaned up .3 at redline. I thought to myself "wow I'm going to try straight 100 octane", to my surprise I produced almost similar results but with AFR's .5 leaner....confusing. The next trip out I tried 104 and witness identical results as the 100 octane tune. My conclusion, after 95 octane unless tuned for the specific octane is a waste of time. All though there are some good gains to made from 91 to 95 IMO and through what I've experience. Just my $.02.

Hammer Down

Skratch do you have 91 instead of 93? With 93 you will be up around 96.5 Octane, you may be ok but if you can mix 91 with the 100 you may be better off. What octane rating is your car set to?

AgSilver

Octane ratings are also based on a specific AFR. The long and short of it is being consistent. You want to determine where you make the most HP on the lowest octane blend which is not so easy to do . . . too high an octane number and you will start losing HP as it burns too slow - - - sort of like driving just slow enough to win.