Euro 98 octane v 102 octane

[Tony B]

Does anyone have any idea of the likely power gain when using 102 octane fuel, versus the rated 98 octane (euro octane measurement not US)?

Assuming full ECU adaptation.

[Imran@Evolve]

Originally Posted by Tony B

Does anyone have any idea of the likely power gain when using 102 octane fuel, versus the rated 98 octane (euro octane measurement not US)?

Assuming full ECU adaptation.

Assuming your car is running stock ECU map:

If your car is hitting its stock ignition targets with 98 RON which it should do, I would not expect any power gains from using 102 RON.

[Tony B]

Originally Posted by Imran@Evolve

Assuming your car is running stock ECU map:

If your car is hitting its stock ignition targets with 98 RON which it should do, I would not expect any power gains from using 102 RON.

I am surprised! I thought the ECU was adaptive, and would advance ignition to the point of detonation. And that point should improve with higher octane.

Are you saying the stock ECU map stops the advancing at 98RON?

[VCMpower]

Spot on!

Originally Posted by Imran@Evolve

Assuming your car is running stock ECU map:

If your car is hitting its stock ignition targets with 98 RON which it should do, I would not expect any power gains from using 102 RON.

[VCMpower]

I have seen power loss running higher octane when the max targets were already hit on lower octane.

Originally Posted by Tony B

Does anyone have any idea of the likely power gain when using 102 octane fuel, versus the rated 98 octane (euro octane measurement not US)?

Assuming full ECU adaptation.

[pbonsalb]

A few years ago, someone in the US tested race gas against pump gas (the pump gas was 93 US octane, which I think is the equivalent of 98 Euro octane) and picked up something like 7% power. I am not sure of the octane of the race gas. The dyno database shows that 91 US cars average less power than 93 US cars and that 93 US cars tend to make less power than 94 US cars.

[VCMpower]

Without a tune for race gas?

Originally Posted by pbonsalb

A few years ago, someone in the US tested race gas against pump gas (the pump gas was 93 US octane, which I think is the equivalent of 98 Euro octane) and picked up something like 7% power. I am not sure of the octane of the race gas. The dyno database shows that 91 US cars average less power than 93 US cars and that 93 US cars tend to make less power than 94 US cars.

[Tony B]

Originally Posted by VCMpower

I have seen power loss running higher octane when the max targets were already hit on lower octane.

Can you define what you mean by "max targets"?

[VCMpower]

Timing/fuel. You would need to do live data to see this.

Originally Posted by Tony B

Can you define what you mean by "max targets"?

[Sam@Alekshop]

Originally Posted by pbonsalb

A few years ago, someone in the US tested race gas
against pump gas (the pump gas was 93 US octane, which I think is the equivalent of 98 Euro octane) and picked up something like 7% power. I am not sure of the octane of the race gas. The dyno database shows that 91 US cars average less power than 93 US cars and that 93 US cars tend to make less power than 94 US
cars.

Here you go:
Bone stock @ 91 Octane (95 RON):
http://www.s65dynos.com/showDyno.php?recID=16
Bone stock @ 100 Octane (105 RON):
http://www.s65dynos.com/showDyno.php?recID=13

In that test, 100 octain gained:
+11wtq, +28whp

[VCMpower]

What octane do you feel is the limit on a stock setup? Or do you feel more octane the better? We have 94 pump here, so 99ish RON, and we reached max with that. With 100% MS 109 we lost 2-3% across the board. Maybe it is something else that caused this, not sure. We immediately assumed it was the fuel in need of a tune.

Originally Posted by Sam@Alekshop

Here you go:
Bone stock @ 91 Octane (95 RON):
http://www.s65dynos.com/showDyno.php?recID=16
Bone stock @ 100 Octane (105 RON):
http://www.s65dynos.com/showDyno.php?recID=13

In that test, 100 octain gained:
+11wtq, +28whp

[BPMSport]

The car will only advance timing up to the full throttle ignition targets. Stock vehicles will see a max of 32 degrees at redline.

If fuel and conditions are good, the car will normally achieve this target. In hotter weather and with 91 octane, you might see it only hitting 27 or 28 degrees. In this situation the 100 octane fuel would be beneficial.

100 octane in ideal conditions would require recalibration to make max power, as the Ecu will not continue to advance past the full throttle timing table, even if there is zero detonation.

Yesterday in my M3 I was doing some logging in 70F weather at night with 91 octane. The car was consistently hitting 32 degrees (or more) ignition advance at redline. This is with 20k on the plugs. It's nice that this Ecu is very sophisticated in that its able to determine combustion quality instead of "listening" for knock.

[Dave07997S]

Originally Posted by pbonsalb

A few years ago, someone in the US tested race gas against pump gas (the pump gas was 93 US octane, which I think is the equivalent of 98 Euro octane) and picked up something like 7% power. I am not sure of the octane of the race gas. The dyno database shows that 91 US cars average less power than 93 US cars and that 93 US cars tend to make less power than 94 US cars.

I think that was PGs car, he never was able to duplicate that run I thought. His car ran like 365rwhp SAE on a dynojet bone stock with 100 octane.

Octane isn't everything, vaporization rate along with other properties of race fuel can help power output.

From my own experience once you go above 94+ octane there really is very little return.

[Imran@Evolve]

Originally Posted by Tony B

I am surprised! I thought the ECU was adaptive, and would advance ignition to the point of detonation. And that point should improve with higher octane.

Are you saying the stock ECU map stops the advancing at 98RON?

Here is the stock ignition map.



As you can see maximum ignition target at WOT and full load is 32 degrees. It will not advance further than that and on 98 RON you will be hitting your stock ignition targets. So to take advantage of the higher RON fuel the map would have to be adjusted accordingly.

[pbonsalb]

Does IAT affect ignition? In other words, could you run 98 RON and still not make the target due to IAT? These cars have a reputation for underperforming in hot weather. What could cause that underperforming?

[VCMpower]

Those coils are special!

Originally Posted by Mike Benvo

The car will only advance timing up to the full throttle ignition targets. Stock vehicles will see a max of 32 degrees at redline.

If fuel and conditions are good, the car will normally achieve this target. In hotter weather and with 91 octane, you might see it only hitting 27 or 28 degrees. In this situation the 100 octane fuel would be beneficial.

100 octane in ideal conditions would require recalibration to make max power, as the Ecu will not continue to advance past the full throttle timing table, even if there is zero detonation.

Yesterday in my M3 I was doing some logging in 70F weather at night with 91 octane. The car was consistently hitting 32 degrees (or more) ignition advance at redline. This is with 20k on the plugs. It's nice that this Ecu is very sophisticated in that its able to determine combustion quality instead of "listening" for knock.

[BPMSport]

Originally Posted by pbonsalb

Does IAT affect ignition? In other words, could you run 98 RON and still not make the target due to IAT? These cars have a reputation for underperforming in hot weather. What could cause that underperforming?

Absolutely. IAT is a huge factor here.

[Sales@Evolve]

Originally Posted by pbonsalb

Does IAT affect ignition? In other words, could you run 98 RON and still not make the target due to IAT? These cars have a reputation for underperforming in hot weather. What could cause that underperforming?

There are maps to retard ignition with IAT yes.

In hot weather you have a doubling effect which you really do begin to feel.

1) The retarded ignition timing
2) The physically hotter less dense air

Combine the two and you can get quite a drop in actual HP delivered.

[Tony B]

All interesting stuff.

The reason I asked the question was that I filled up with Aral 102RON on my recent Ring trip.

On the journey home, I had plenty of "autobahn moments" just like the journey out.

With the 102 fuel, I was amazed at how much quicker the car felt, all through the rev range. It was definitely not just in my head, but I suppose the only way to prove it is to get it on a rolling road. I was hitting 162mph (the limiter) quickly without even using full throttle.

Aral claim an extra 10% power, but I am not sure what fuel they are benchmarking against (they talk about Super on their website, which ought to mean 98RON).

My butt dyno suggests they might actually be making a reasonable claim.

[Sales@Evolve]

Tony,

which 98 octane do you use and are comparing this 102 octane to?

[Tony B]

Originally Posted by Sal@Evolve

Tony,

which 98 octane do you use and are comparing this 102 octane to?

As a rule, either Tesco 99 or Shell Nitro+ (which is 99 or 100, I think). My immediate back to back comparison was based on the fuel bought in Belgium, and to be honest I don't remember which brand it was. Might have been Shell, I could check receipts but am away from home currently.