Sunoco GT100-octane for track day in M3?

[Sleeper519]

The reason I ask is last time I was at Road Atlanta for an event, I almost ran out of gas during a session, left the track driving right by that Sunoco race gas pump and barely made it to the Chevron down the road. I naively figured that it would harm my engine to put "race gas" in my street car.

My question is, could I do it in a pinch without harm? Would it actually boost my performance without ECU changes (tune) or not? I was actually thinking of a 50/50 mixture of pump 93-oct + Sunoco GT 100-oct (unleaded, of course).

I know this has been brought up before but I could not find it in my search.

Thanks.

[CICIO]

The M3 absolutely loves race gas. I was just up at Road A this weekend and filled it full of 100oct! Absolutely run some next time your up there. Safer on the engine as it burns cooler, and the ECU will add timing. You can mix it if you like too.

Hope this helps.

~Cicio

[m3heaven]

I actually like putting in like 5 gallons of 100octane fuel in my tank when going to the track.

[Sleeper519]

Awesome, good to know! I will def try some in 2 weeks at RA for the CCA HPDE. Got 4 new shoes today and I'm ret to go.

[BRDHNTR]

I am going to go really off topic and say I'm so jealous of you. It was -9 deg F on my way to work yesterday and the roads are so bad I don't think I'll have my M3 out before Spring.

The unleaded race gas certainly doesn't hurt, but in a N/A M3 you won't see gain worth the extra $'s. If you have an FI car w/ a specific map that you can load like a GT-R and a Cobb Accessport, well then, it's an entirely different (and very expensive) story

[Kyoshi71]

Fill the tank about 1/3 100 octane and the rest 93. That will give you a nice boost in octane that you can actually use. My understanding is that our ECUs are capped for a max octane of 96 and that everything above that is a waste. The difference in the way the car feels between 93 & 96 is noticable.

[Gearhead999s]

I have tried a partial tank of 100 a couple of times and I noticed a difference in response in the mid range but no more power up top as far as I could tell and no difference in speed on a 3/4 uphill straight.It was quite nice to pay 4 x the price of 94 octane also

[Richbot]

GT100 is very safe in catted vehicles, I've had to run it through my truck before to make it to the next gas station on the way back from the racetrack.

It's almost worth it for the smell alone. Seems like the diminishing returns start at 94octane on the M3 from the dynos that have been posted on the forums anyway.

The engine will run cooler on 100 octane which might be a benefit depending on your conditions, but running cooler can cause richer running which can eventually hurt cats if the car is already pig rich, but this car seems to be only "piglet" rich on the stock tune.

[JJM335]

Anyone else notice an oily film on the rear of the car after running hard (track) with high octane fuel?

[dcstep]

PencilGeek got around 30-hp out of a tank of 100-octane, in CA near sea level. Near Atlanta you should get similar results. As your altitude goes up the car can't handle as much octane. Here, in Colorado, at 5400 ft above sea level, I mix 91 and 100 to shoot for 95/96 octane and pick up only a few hp due to low air density.

[dcstep]

Originally Posted by TrackRat

^^^ You don't get any power increase with higher octane fuel unless:

1. The engine is knock limited with the existing fuel

2. The ignition map is recalibrated to use the higher octane fuel

3. The engine actually requires more ignition advance to reach peak power

More ignition advance (vs. the correct MBT ignition advance), does not = more HP

Exactly, and PG got 30 hp at the rear wheels on the dyno by going from 91 to 100-octane.

At 5400 ft above sea level you'll actually lose around 5-hp with 100% 100-octane. Blend fuel to get around 96-octane at 5400 feet and you'll gain around 5-hp.

Theory is good, but it doesn't beat back-to-back dyno runs for answering the question about power. The Sunoco is unleaded and 100% petroleum, so it'll not harm our cars.

[wwjd15]

I feel the car drives better on track. At least, I feel it.

[Sleeper519]

Originally Posted by TrackRat

dcstep-

You've missed the point. The OP asked about adding some 100 octane for use in his car at the track. He will not see any performance increase with 100 octane over 93 octane because his engine is calibrated for 93 octane and doesn't require higher octane to prevent detonation.

This ain't theory, it's reality... over ten thousand hours of engine dyno calibration reality. It's a fact that using higher octane fuel than required can actually lower HP depending on the fuel burn rate and ignition mapping.

Thanks, TrackRat, that is what I suspected. However, there is a definite dyno-able performance difference btw/ 91 (CA) and 93 oct, and consensus seems to be that it may top out at 96-ish or so, and above that would require ECU remapping and advancement to obtain benefit from 100 oct Sunoco gas and beyond. I'm just not sure what degree of "adaptation" our ECU undergoes with varying fuel octanes, and over what time frame.

So, my question was answered: I won't hesitate to put a "sip" of the Sunoco 100 at the very convenient trackside pump if I'm on "E" with a few laps to go.
And I will probably mix in a few gallons up front just for grins.

Thanks all.

[MaxL]

Originally Posted by TrackRat

dcstep-

You've missed the point. The OP asked about adding some 100 octane for use in his car at the track. He will not see any performance increase with 100 octane over 93 octane because his engine is calibrated for 93 octane and doesn't require higher octane to prevent detonation.

This ain't theory, it's reality... over ten thousand hours of engine dyno calibration reality. It's a fact that using higher octane fuel than required can actually lower HP depending on the fuel burn rate and ignition mapping.

Most modern engines are not calibrated to a very specific octane number. They ride the knock sensors with varying levels of aggressiveness to get the best out of what they got, within a certain range. Some cars even have specs for two different octane numbers, both safe to run, with one just giving less HP. So the question is valid. M3 appears to be more aggressive that other cars with this, and it's upper range of adjustment appears to be over 93 octane, as some dyno's show.

[dcstep]

Originally Posted by TrackRat

dcstep-

You've missed the point. The OP asked about adding some 100 octane for use in his car at the track. He will not see any performance increase with 100 octane over 93 octane because his engine is calibrated for 93 octane and doesn't require higher octane to prevent detonation.

This ain't theory, it's reality... over ten thousand hours of engine dyno calibration reality. It's a fact that using higher octane fuel than required can actually lower HP depending on the fuel burn rate and ignition mapping.

You seem to be the one that didn't understand the question. It was two-part, one being would it hurt the engine? No, so long as it's leaded and petroleum based. The second part gives you some difficulty.

Ok, then how do you explain the 30-hp increase that PG got in California and the 5-hp I get at 5400 ft, going with 96-octane? I've measured mine at 91, 93, 96 and 100-octane and the highest power was at 96-octane.

So, in your ten thousand hours of dyno calibrating E9x M3s, what happened when you put 100-octane in the car and ran it on the dyno vs. a baseline of 91 or 93-octane (state dependent). According to you, the hp should have stayed the same, or even gone down. Instead of spouting theory, cite some dyno numbers.


Dave

[1MORELAP]

Originally Posted by TrackRat

his engine is calibrated for 93 octane .

I do not think that is true. The M3 is most likely calibrated for 94/95 octane. It will adjust all the way down to 91 or possibly further.

You are right that IF the M3 was maxing out on timing at 93 octane, going beyond would not result in power increase. But your initial assumption is not correct.

Since we lack proof from a BMW engineer, we have to relay on tests that have been done and show gains to about 96/98.

Also, we can speculate that BMW optimizes the car to the highest Octane available in Germany, which I think is 95 US spec or 98 Euro spec.

If you can afford $10 per gallon, mix 100 octane at 1/3 of tank or so and you will see gains. Especially at hot temps.

Tomasz

[Jaypod]

Originally Posted by 1MORELAP

I do not think that is true. The M3 is most likely calibrated for 94/95 octane. It will adjust all the way down to 91 or possibly further.

[dcstep]

Originally Posted by TrackRat

...

If I had a dollar for every bogus dyno test/report posted on the internet I'd be a millionaire many times over. You are perfectly free to believe whatever you want but what I'm telling you is fact and can be confirmed with any experienced OEM car maker engine calibration engineer working in the automotive industry worldwide.

So PG and I are liars according to you? You're full of sh*t.

I published my dyno runs showing power decreases at 110 and 100-octane and continued to invest in dyno time to find the optimal mix (around 96-octane at 5400 ft above sea level). PG posted multiple comparitive runs also. Part of our objectives were to give readers some objective evidence, rather than pie in the sky theory from someone that obviously doesn't understand how the adaptive systems of this engine works.

Readers should research PG's dyno database on this forum for independent, objective answers to a few of the questions about the E9x's response to various mods. These are not tuner's pumped up numbers, but actual grass roots testing done by members of the forum. Look at the data and then read what TR alleges and decide for yourselves.

Dave