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      10-05-2012, 10:45 PM   #1
GIdriver
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100 octane with ESS tune

So I will go to a 1/2 mile event in December and since I have availability of 100 octane Sunoco race fuel was wondering if it will make any difference going higher than 93 AKI. I'm hoping for a 130-135mph top speed at the 1/2 mile.

As my signature says, I have the ESS Akra Evo tune. ESS told me that the tuning file is adaptive from 91 to 95 AKI. From what I've read our cars stock won't gain much above 95-96 AKI.

My questions are (given my tune):

1. Will going above 95 will hurt the engine?
2. Will going above 95 will hurt performance in any way?
3. How about meth?

Thanks in advance.

PS: I know there will be much more faster cars at the event (for example there will be two Alpha 12 GTR's . Going just to enjoy my car in a safe environment and have fun with some friends.
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Last edited by GIdriver; 10-05-2012 at 11:01 PM.
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      10-06-2012, 01:56 AM   #2
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As far as I know I don't think anything above 95 will damage your car. In terms of performance I don't think you will feel a noticeable difference either with the 100 octance. I could be wrong though. We have 95 standard at the pumps here in South Africa and I add octance boosters every now and then, and honestly I cannot feel a huge difference. Granted your car will run better on the 100, so you might get a little bit more out of it than you would on standard gas. Good luck and enjoy the event
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      10-06-2012, 01:58 AM   #3
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yes, it will improve performance. not dramatically but it will. you already have 93. the biggest jump is from 91-96. 93 to 96 blend is not as big.

there's a huge difference on california 91 octane vs. half 100/half 91... low end torque improves a lot, as does smoothness when first starting off on a drive...
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      10-06-2012, 03:52 AM   #4
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OP think of high octane fuel as protection..the tendency is for people to think high octane fuel makes more power..the reality is high octane fuel is used in performance applications where you want to take advantage of higher ignition and intake mapping and avoid detonation..thats it in a nutshell..if you dont have the proper ECU mapping to take advantge of the higher octane fuel it doesnt make more power..all it does is provide added protection against detonation, knocking, pinging etc

There is slight headroom for improvement on stock ECU..up to about 95 seems to be the max
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      10-06-2012, 04:28 AM   #5
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Quote:
Originally Posted by GIdriver View Post
So I will go to a 1/2 mile event in December and since I have availability of 100 octane Sunoco race fuel was wondering if it will make any difference going higher than 93 AKI. I'm hoping for a 130-135mph top speed at the 1/2 mile.

As my signature says, I have the ESS Akra Evo tune. ESS told me that the tuning file is adaptive from 91 to 95 AKI. From what I've read our cars stock won't gain much above 95-96 AKI.

My questions are (given my tune):

1. Will going above 95 will hurt the engine?
2. Will going above 95 will hurt performance in any way?
3. How about meth?

Thanks in advance.

PS: I know there will be much more faster cars at the event (for example there will be two Alpha 12 GTR's . Going just to enjoy my car in a safe environment and have fun with some friends.
This all depends on the ECU programming. Here's the "basic 101" version of how it works:

The fuel octane content will affect the oxygen content of the exhaust gases. This translates to voltage changes from your oxygen sensors. These signals are sent back to the ECU. If your ECU program allows for it, it will advance the ignition timing resulting in more power. A more sophisticated ECU program (which one would hope is in a high performance car) will be based on increasing detonation thresholds as the octane increases. It will sense the changed output from the oxygen sensor when high octane fuel is used, interpret this as a higher detonation threshold, and allow for ignition timing advance. This creates more power.

There are other factors, but this is the bulk of it. Most of the high end european performers will make more power up to about 95-96 octane. Beyond this, there is no more timing advance regardless of the change in oxygen sensor voltage output.
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      10-06-2012, 10:52 AM   #6
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bpencilgeek did a dyno, 30whp from 91 vs. ~98 octane without a tune. one of the local bay area guys art did it as well, dynoed over 400whp with N/A bolt ons whereas he got a lower dyno reading on 91.

as the posters above said, benefits start to diminish around 96ish octane

i have personally tried it with great results, several tanks of it. as stated earlier, better response in lower RPMs and smoother take off when engine is cold. higher rpm, hard to notice without a stopwatch but the difference certainly isn't as great as it is down low. most people complaining about low end torque are from california, probably because there are a lot of m3's in california but also likely due to the lower fuel quality.

this car adapts fairly quickly. e46 m3 would take almost a tank to adapt to 100 but this one seems to realize the benefit by about 1/8 to 1/4 tank.
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      10-07-2012, 01:05 PM   #7
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Thanks for the replies. I've decided to mix in order to get ~95.

I'm afraid I have a far more serious problem now; I can't stop thinking about getting a 575 ESS kit
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      10-08-2012, 01:34 AM   #8
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high octane is good. High ocatane will not negatively affect engine or performance. It will increase performance depending if your tune adapts to conditions, which im pretty sure they all do
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      10-08-2012, 10:41 AM   #9
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The ECU will adjust to take advantage of higher octane fuel up to 100 AKI unleaded and will provide added safety. Best result I have found for the dollar is a mix of about 4-5 gal of 100 with 91 or 93. This will get you max performance without overspending. The car is very happy with anything over 94 AKI.
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      10-08-2012, 11:00 AM   #10
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Quote:
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The ECU will adjust to take advantage of higher octane fuel up to 100 AKI unleaded and will provide added safety. Best result I have found for the dollar is a mix of about 4-5 gal of 100 with 91 or 93. This will get you max performance without overspending. The car is very happy with anything over 94 AKI.
Thanks for the input. I thought I should not go above 95 AKI due to the tuning. Thanks for clearing that up.
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      10-09-2012, 09:37 AM   #11
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Will the car still benefit from 100 octane even without a tune?
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      10-09-2012, 12:40 PM   #12
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See Post #6.
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      10-09-2012, 02:47 PM   #13
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Quote:
Originally Posted by LarThaL View Post
This all depends on the ECU programming. Here's the "basic 101" version of how it works:

The fuel octane content will affect the oxygen content of the exhaust gases. This translates to voltage changes from your oxygen sensors. These signals are sent back to the ECU. If your ECU program allows for it, it will advance the ignition timing resulting in more power. A more sophisticated ECU program (which one would hope is in a high performance car) will be based on increasing detonation thresholds as the octane increases. It will sense the changed output from the oxygen sensor when high octane fuel is used, interpret this as a higher detonation threshold, and allow for ignition timing advance. This creates more power.

There are other factors, but this is the bulk of it. Most of the high end european performers will make more power up to about 95-96 octane. Beyond this, there is no more timing advance regardless of the change in oxygen sensor voltage output.
Taking advantage of higher octane fuel has nothing to do with the O2 sensors or the oxygen content (the addition of oxygenates, ethanol, methanol, etc. has the effect of increasing octane rating but it don't allow timing changes to be affected by the O2 sensor circuit) of the exhaust gases. Timing is controlled by the knock control circuit!

The Knock control circuit will monitor knock and allow the DME/ECM to advance the timing of the engine to the highest allowable value until knock occurs or until the target timing in the software is reached. The stock timing targets of the S65 are quite high so any fuel below ~ 96 octane never allows the timing advance targets to be reached hence the engine makes more power up until the octane rating of the fuel allows the max timing advance target to be reached.
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Last edited by BMRLVR; 10-09-2012 at 02:55 PM.
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