[David1]

All the higher octane does on a stock car is maintain what you have. The ECU has preset parameters and does not learn higher octane values. Now if you are tuned and playing with timing, etc, then is a different ball game.

[ried]

Originally Posted by ajvdh

And the M2 is one of those cars, hence BMW recommending 98 (RON)/93 (AKI), and requiring a minimum of 95 (RON)/91 (AKI). You will lose power if you use the minimum grade, and, depending on other factors (altitude, temperature, relative humidity), you may fatten up the torque curve a small amount if you go higher than recommended.

I would love to believe that. Do you have a source? What's the actual, measurable difference in power between AKI 91 and 93? Or even higher octane, using the stock ECU, if your source provides that info?

[ajvdh]

Originally Posted by ried

I would love to believe that. Do you have a source? What's the actual, measurable difference in power between AKI 91 and 93? Or even higher octane, using the stock ECU, if your source provides that info?

FTOM (page 165) "If you use gasoline with this minimum AKI Rating, the engine may produce knocking sounds when starting at high outside temperatures."

When an engine detects knocking, it's going to do something to compensate. Generally pull boost or timing.

This might provide useful information:
https://en.wikipedia.org/wiki/Octane_rating#Effects
and
https://en.wikipedia.org/wiki/Octane...nal_variations
Scroll down to the bullet item about the US, and pay particular attention to the sentence about turbo cars being forced to run 91 instead of 93.

[gingiman]

so far inconclusive
any chance for consensus?

[ried]

Originally Posted by ajvdh

FTOM (page 165) "If you use gasoline with this minimum AKI Rating, the engine may produce knocking sounds when starting at high outside temperatures."

When an engine detects knocking, it's going to do something to compensate. Generally pull boost or timing.

This might provide useful information:
https://en.wikipedia.org/wiki/Octane_rating#Effects
and
https://en.wikipedia.org/wiki/Octane...nal_variations
Scroll down to the bullet item about the US, and pay particular attention to the sentence about turbo cars being forced to run 91 instead of 93.

That's a pretty roundabout way of saying "I'm not sure."

We're already very familiar with octane and how it impacts knocking, timing, and horsepower. This is the M2 forum, after all. I asked if you had any specifics about this particular BMW engine. Seems like aside from a generic "most turbocharged vehicles are unable to produce full power, even when using the "premium" 91 AKI fuel" Wikipedia answer, we don't yet.

As a practical example, I'd like to know if a bone stock M2 in California running 91 is going to be measurably slower than the same car in Washington State running 93.

I somehow doubt it.

[ajvdh]

Originally Posted by ried

That's a pretty roundabout way of saying "I'm not sure."

We're already very familiar with octane and how it impacts knocking, timing, and horsepower. This is the M2 forum, after all. I asked if you had any specifics about this particular BMW engine. Seems like aside from a generic "most turbocharged vehicles are unable to produce full power, even when using the "premium" 91 AKI fuel" Wikipedia answer, we don't yet.

As a practical example, I'd like to know if a bone stock M2 in California running 91 is going to be measurably slower than the same car in Washington State running 93.

I somehow doubt it.

Believe what you want. I've owned turbo cars for 30 years. All of them were sensitive to octane. I don't think BMW has invented a magic process which makes the N55 immune from physics and chemistry.

[ried]

Originally Posted by ajvdh

Believe what you want. I've owned turbo cars for 30 years. All of them were sensitive to octane. I don't think BMW has invented a magic process which makes the N55 immune from physics and chemistry.

Who said they did? I just asked if a bone stock M2 in California running 91 is going to be measurably slower than the same car in Washington State running 93.

You seem to know the answer, so let's hear the details

[zenmaster]

Originally Posted by ried

Who said they did? I just asked if a bone stock M2 in California running 91 is going to be measurably slower than the same car in Washington State running 93.

You seem to know the answer, so let's hear the details

Yes, it should definitely be measurably slower, and possibly noticeably slower. We can see on the instrumented dyno runs (bone stock) that the top end suffers timing pull on 91. And that's simply what you'd expect from an aggressive tune - be it from factory or aftermarket.

[Nine Lives]

Here's a video excerpt from Fifth Gear testing different fuels on a Golf GTI @ 0:30 in.

There is a difference,make your own minds up...

[ried]

Great video, Nine Lives. Everyone else, jump to 5:20 for the raw data from the dyno. Total is 1-2% difference in whp for premium fuels in the UK. Note that they were comparing the cheapest with the most expensive pump fuels.

I wonder how much BMW's turbocharging will affect the results? It may widen the delta as ajvdh pointed out.

Another factor to consider is how much the ethanol content of our American fuels might impact performance.

[zenmaster]

Originally Posted by ried

Great video, Nine Lives. Everyone else, jump to 5:20 for the raw data from the dyno. Total is 1-2% difference in whp for premium fuels in the UK. Note that they were comparing the cheapest with the most expensive pump fuels.

I wonder how much BMW's turbocharging will affect the results? It may widen the delta as ajvdh pointed out.

Another factor to consider is how much the ethanol content of our American fuels might impact performance.

I'm guessing at least 5whp using 93 at stock 15psi boost levels. To put that into context, if an East coast M2 had a bunch of crap in it, increasing its weight by around 100lbs, it would still be just as fast as a West coast M2. Or to put it another way, carbon fiber roof (-13lbs) and drive shaft options (-15lbsx4) for the M2 still wouldn't offset the power difference due to octane.

[pz619]

Adding higher octane fuel will not increase power. When BMW says their cars adjust to the fuel they aren't saying power will increase with better fuel. All they are saying is that the car will begin to pull timing once knock/pre-detonation is detected. Typically this is due to lower quality fuel. If BMW says the car makes 265 hp on 91 octane, it's going to make 265 hp on 93 octane, 265 hp on 100 octane, etc.

[zenmaster]

Originally Posted by pz619

Adding higher octane fuel will not increase power. When BMW says their cars adjust to the fuel they aren't saying power will increase with better fuel. All they are saying is that the car will begin to pull timing once knock/pre-detonation is detected. Typically this is due to lower quality fuel. If BMW says the car makes 265 hp on 91 octane, it's going to make 265 hp on 93 octane, 265 hp on 100 octane, etc.

Incorrect.

[pz619]

Originally Posted by zenmaster

Incorrect.

Disagree, but you are entitled to your opinion.

There are numerous articles, in the hundreds, that show you won't get more performance using higher octane gas on stock motors. Dyno tests back this up. Furthermore BMW rates and designs their motors at 91 AKI. Stock motors aren't scalable to the octane rating you put in the tank. Otherwise dumping C16 into your tank would give you a substantial HP increase.

[zenmaster]

Just like the GTI, the M2 will make more power going from 91 to 93 octane. Since the M2 has a more aggressive tune, with already known N55 boost levels, I'm guessing at least 5hp more. Believe what you want, but try doing a little research next time.

[pz619]

Originally Posted by zenmaster

Just like the GTI, the M2 will make more power going from 91 to 93 octane. Since the M2 has a more aggressive tune, with already known N55 boost levels, I'm guessing at least 5hp more. Believe what you want, but try doing a little research next time.

I've done my research. My advice to you is the same.

[pz619]

Originally Posted by ajvdh

FTOM (page 165) "If you use gasoline with this minimum AKI Rating, the engine may produce knocking sounds when starting at high outside temperatures."

When an engine detects knocking, it's going to do something to compensate. Generally pull boost or timing.

This might provide useful information:
https://en.wikipedia.org/wiki/Octane_rating#Effects
and
https://en.wikipedia.org/wiki/Octane...nal_variations
Scroll down to the bullet item about the US, and pay particular attention to the sentence about turbo cars being forced to run 91 instead of 93.

In fairness, the last bulletpoint's source was Sunoco. I believe they have an interest in selling you a more expensive fuel.

[ried]

At this point we're all just pissing in the wind. At the end of the day, we're talking 1 or 2% whp difference, if any at all. Ethanol might even play a bigger role than that.

[playitfunky]

I'm not sure why anyone would spent a tidy sum on a high performance car and then fill it with a low grade fuel but each to their own.
V-Power all the way for me!

[335BOY]

Originally Posted by zenmaster

Just like the GTI, the M2 will make more power going from 91 to 93 octane. Since the M2 has a more aggressive tune, with already known N55 boost levels, I'm guessing at least 5hp more. Believe what you want, but try doing a little research next time.

Is ANYONE going to notice 5hp? That would be virtually un-measureable.
I wonder what the HP tolerance from the factory is? Probably around 5hp......

[AlpsRider]

Originally Posted by playitfunky

I'm not sure why anyone would spent a tidy sum on a high performance car and then fill it with a low grade fuel but each to their own.
V-Power all the way for me!

I'm just wondering, what is the VPower octane level you guys get in the UK?

[Nine Lives]

Originally Posted by AlpsRider

I'm just wondering, what is the VPower octane level you guys get in the UK?

It is supposedly 99 RON now.