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Fuel for Track Days

 
Old 06-07-2019, 05:35 PM
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WELEPRO
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Default Fuel for Track Days

Both tracks Iíll be at this summer(VIR & Dominion Raceway) offer Sunoco Fuels. Specifically, Sunoco 260 GTX which is 98 octane and ethanol free.

The owners manual recommends 100 octane. Has anyone used the Sunoco 98 octane? Is this suitable?

Thank you in advance!
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Old 06-07-2019, 07:08 PM
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Newton06
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I've been instructing st VIR for some time, and run 93 octane in my 2018 Z06.

I will be instructing there for NCM later this month as well.

You won't notice any difference running Citco 93 octane for a $1 less a gallon down the road in Semora, than what you will pay at the Sunoco North Paddock pump.

I thought they have 100 and 110 there as well, (the latter is leaded I believe).

If not, even the 98 will be overkill, but if it makes you feel good... and it smells good too
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Old 06-08-2019, 08:49 AM
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Originally Posted by Newton06 View Post
I've been instructing st VIR for some time, and run 93 octane in my 2018 Z06.

I will be instructing there for NCM later this month as well.

You won't notice any difference running Citco 93 octane for a $1 less a gallon down the road in Semora, than what you will pay at the Sunoco North Paddock pump.

I thought they have 100 and 110 there as well, (the latter is leaded I believe).

If not, even the 98 will be overkill, but if it makes you feel good... and it smells good too
Greetings! The motivation for me researching the higher octane is due to some weird performance results from my last track day a few weeks ago. The car was noticeably pulling timing, particularly towards the end of the event. It was very hot that day, and the car did great with this exception.

I wonít make it to VIR for the NCM event unfortunately. Iíll be there for SCCA Track Night in July. If youíre around, Iíd love to say hi!
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Old 06-08-2019, 02:45 PM
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Hib Halverson
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I have run some octane "tests" with 1878. All this testing was done at near sea level in cool temperatures. I used HPTuners "VCM Scanner" application to log knock retard data during WOT runs uphill in fourth gear from 1500 to the 6600 rpm rev-limiter.

To run KR-free with that kind of air took about 96-octane fuel which I mixed using 91-oct pump gas and Rockett Brand 100-oct unleaded racing fuel.

With that in mind, I can understand why GM recommends 100-oct fuel for track use. GM makes the recommendation with tracking in hot weather in mind. On a hot day on a track doing successive laps which builds heat in the powertrain cooling systems, my guess is you'll need at least 98-oct.

Keep in mind that letting the E99s EST function control detonation with knock retard allows lower octane gas but all that knock retard makes the engine run hotter.

Bottom line: tracking in cool weather without knock retard needs about 96. Tracking in warm weather might need 98 and tracking on hot days could require 100-oct.
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Old 06-08-2019, 03:21 PM
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Originally Posted by Hib Halverson View Post
I have run some octane "tests" with 1878. All this testing was done at near sea level in cool temperatures. I used HPTuners "VCM Scanner" application to log knock retard data during WOT runs uphill in fourth gear from 1500 to the 6600 rpm rev-limiter.

To run KR-free with that kind of air took about 96-octane fuel which I mixed using 91-oct pump gas and Rockett Brand 100-oct unleaded racing fuel.

With that in mind, I can understand why GM recommends 100-oct fuel for track use. GM makes the recommendation with tracking in hot weather in mind. On a hot day on a track doing successive laps which builds heat in the powertrain cooling systems, my guess is you'll need at least 98-oct.

Keep in mind that letting the E99s EST function control detonation with knock retard allows lower octane gas but all that knock retard makes the engine run hotter.

Bottom line: tracking in cool weather without knock retard needs about 96. Tracking in warm weather might need 98 and tracking on hot days could require 100-oct.
That's great information. Thank you!
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Old 06-08-2019, 10:26 PM
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Originally Posted by Hib Halverson View Post
I have run some octane "tests" with 1878. All this testing was done at near sea level in cool temperatures. I used HPTuners "VCM Scanner" application to log knock retard data during WOT runs uphill in fourth gear from 1500 to the 6600 rpm rev-limiter.

To run KR-free with that kind of air took about 96-octane fuel which I mixed using 91-oct pump gas and Rockett Brand 100-oct unleaded racing fuel.

With that in mind, I can understand why GM recommends 100-oct fuel for track use. GM makes the recommendation with tracking in hot weather in mind. On a hot day on a track doing successive laps which builds heat in the powertrain cooling systems, my guess is you'll need at least 98-oct.

Keep in mind that letting the E99s EST function control detonation with knock retard allows lower octane gas but all that knock retard makes the engine run hotter.

Bottom line: tracking in cool weather without knock retard needs about 96. Tracking in warm weather might need 98 and tracking on hot days could require 100-oct.
I agree 100%. It's the hot weather that needs the high octane up to 100.
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Old 06-09-2019, 07:44 PM
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Originally Posted by Zjoe6 View Post
I agree 100%. It's the hot weather that needs the high octane up to 100.
There are probably fewer than 5 people on this board who are skilled enough drivers where this minuscule performance 'hit' would effect their lap times.

For HPDE events, unless you are eeking out that last 10th in the instructor run group, you are wasting your money on $9/gallon gas.

Ask Poor-sha (Sean) or Bill Dearborn if they run 100 octane...

Last edited by Newton06; 06-09-2019 at 07:47 PM.
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Old 06-09-2019, 09:20 PM
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Originally Posted by Newton06 View Post
There are probably fewer than 5 people on this board who are skilled enough drivers where this minuscule performance 'hit' would effect their lap times.

For HPDE events, unless you are eeking out that last 10th in the instructor run group, you are wasting your money on $9/gallon gas.

Ask Poor-sha (Sean) or Bill Dearborn if they run 100 octane...
I've actually tried 100 octane several times and never saw a difference in lap times. I also gave up trying to bring in enough gas from off site to the track for the ZR1. At a consumption rate of 11 gallons in 20 minutes you'd need a 55 gallon drum of fuel for each day at the track.

Last edited by Poor-sha; 06-10-2019 at 11:23 AM.
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Old 06-09-2019, 11:02 PM
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Originally Posted by Poor-sha View Post
I've actually tried 100 octane several times and never seen a difference in lap times. I also gave up trying to bring in enough gas from off site to the track for the ZR1. At a consumption rate of 11 gallons in 20 minutes you'd need a 55 gallon drum of fuel for each day at the track.
And cold reality rears its ugly head! I like the blue car, too.
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Old Yesterday, 10:27 AM
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Originally Posted by Zjoe6 View Post
I agree 100%. It's the hot weather that needs the high octane up to 100.
Spring Mountain runs 100 octane but it is pretty hot there and the field elevation is considerable.
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Old Yesterday, 11:22 AM
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I would run it but not for the extra performance but to keep the engine out of knock retard for longevity sake... It's not all that much more over a weekend HDPE event to run 100 than 93 octane...
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