When I had my '01 S4 I used to run 100 Octane fairly often. It had a program optimized to run the fuel which made a HUGE differnce in power, but it also ran better using 100 octane in "stock" mode.

Sooooo...I was thinking, wouldn't the JCW engine benefit from running 100 octane fuel? Any personal experience from anyone would appreciated.
Just to be clear, I'm not talking about mixing fuel grades...just straight 100 octane.
Thanks

 

Are you tuned and running higher boost? If so it would definitely help. Otherwise I think 93 octane should be enough to prevent pre-detonation if that's what your goal is.

You would feel a difference by running pure gas, and by that I mean gasoline without added corn (ethanol).

Neither 100 octane or ethanol free gas is easy to find though, at least not in my area.

 

No, I am not tuned at this point. I will be looking into it shortly.
100 octane can be had around where I live.

 

Running an higher octane will not net you much of a benefit unless the computer is pulling timing or knows to change programming with the higher octane fuel. If it is not designed for it, it will not have enough benefit vs cost imo. A tune and higher boost with higher octane I can understand.
Sounds like the Audi was pulling timing and the 100 octane was keeping the tune happy by negating nock and timing pull.

 

So the car is a 2012? No tune available yet.

 

Be very very very careful running race gas in your car. It is not required to be unleaded and leaded gas will poison your oxygen sensors and catalytic converters in about 6000 miles worth of driving.

 

And no AV Gas either.

 

Yeah, you got that right; 100 LL (low lead) AV gas actually has more lead than leaded auto fuel does (or did)...

As an aside, I once worked with a guy who owned a First Generation Firebird (I think it was a '67) with the 400 cu. in. engine; he ran 100 LL through that thing all the time and it was happy as a clam! Of course, the engine was made to use leaded fuel too...

 

The R56's lovvvvve as much octane as you can give them. It was always my feeling that our crap AZ 91 octane is not enough for them, especially when it's 100+ degrees out. You'll hear completely stock ones pinging.

So yes, 100 octane is great but as you know it just gets pricey!

Better option: meth injection....ie Aquamist. A must here in the desert....

 

104 octane and lower is unleaded FYI, they do have standards is race gas just like pump gas.

 

what about the octane boosters you pour into the tank?

 

Running water/meth injection increases your octane number by 1 or 2 points, depending on your mixture. That's based only upon the octane number of meth, not water. Water's octane number is effectively infinite, so not sure how the water affects the octane number, but I know for sure that water aids greatly in knock supression

 

Just a general note for folks to keep in mind: higher octane does not automatically equal more horsepower; all an octane rating provides is a relative measurement of the anti-knock properties of a given gasoline blend. As the compression ratio of an engine is increased, gasoline with a lower octane rating becomes more and more prone to pre-detonation (very bad); which is why those kinds of engines require higher-octane (i.e., premium grade) gasoline.

So, unless one is increasing the compression ratio of their engine to something higher than factory stock, there's nothing to necessarily be gained from increasing the octane rating of the fuel being used to more than what's commonly available at the pumps (91 octane or better, according to the Owner's Manual). You won't hurt anything by using 100 octane unleaded auto fuel in your JCW, but you might not get any benefit (or horsepower increase) from it either -- unless you're already getting engine knock or pre-detonation with the octane grade being used (which shouldn't be happening if the engine has not been modified, or isn't malfunctioning for some reason)...

 

IE increasing boost. Your MPG will also fall with higher octane fuel.

 

Yes, that's one way; you can also mechanically change the compression ratio with, for example, a different piston stroke; or by changing the piston or heads. Point is: using higher octane fuel doesn't necessarily buy you anything unless you're upping the compression ratio... It's going to depend...

 

Oh yes it does, how technical would you like to get regarding this subject ?

Our ECU is self adaptive to many variable engine load parameters, and one of these is the introduction of timing advancement, the ECU takes a load signal from the 1 knock sensor for all 4 cylinders, and temperature readings, these include cylinder firing temperatures, which affects cylinder pressures! And the use (in this case) of 100 octane will reduce the chance of pre ignition, and the ECU will read this and advance the timing sooner, than it would using a lesser octane gas, this in turn gives the placebo effect of more power, but actually your engine simply utilises all the readily available power (timing advancement) to it's full potential.

That quick explanation is a very brief outline, there is far more to understand, regarding burn temperatures, flame kernels, oxidation properties of fuels, fuel used to cool the cylinder charge, etc etc etc, but for now that should do.

 

I agree that there would be a theoretical point (which could actually be an 'band' or 'range' with a local 'maximum' when using an adaptive ECU) where fuel of a certain octane rating would burn optimally for an engine of a given compression ratio, thereby providing peak horsepower and extracting the most energy per unit of fuel. But gasoline is gasoline, so to speak. Higher octane gasoline does not contain more energy per unit of fuel; higher octane gasoline is just less likely to pre-ignite in a given engine with a given compression ratio. All an adaptive ECU has the ability to do is shift (as best as it can) the timing to the theoretical point of peak efficiency for the octane rating it senses. One is not so much seeing a horsepower gain (although I agree that it could vary a bit within the so-called 'band' or 'range' due to any number of variables) as they are seeing relatively consistent engine output efficiency.

Beyond the point where the ECU can adapt, you will not see any horsepower gains -- and could actually see a horsepower loss when using fuels with higher octane ratings because of incomplete fuel ignition. The ECU can't infinitely vary the engine timing to compensate for all theoretical octane ratings; there will come a point where the engine is mechanically limited or the ECU programming reaches an endpoint. Once all the variables reach that point, fuel with a higher octane rating will not do anything but hinder engine performance.

So the JCW engine may, for example, have its 'sweet spot' with 91 octane fuel; and the ECU may be able to adapt for anything from 87-95 (just guessing). Fuel with a lower octane rating would have a tendency to pre-detonate, thereby robbing horsepower (as well as potentially creating other problems); fuel with a higher octane rating would not burn completely (because it is even more 'resistant' to detonation), also robbing horsepower. Fuel with ratings beyond the 'adaption range' will only perform worse than the endpoint rating.

Now: is 100 octane unleaded past the point where the MINI's stock ECU programming can adjust the engine to take advantage of it...? I don't know. I guess anyone with access to that type of fuel is welcome to try and find out. But unless one increases the compression ratio and/or alters the ECU programming to handle it, one is not likely to be gaining anything either...

 

I'll say it again...the R56 can benefit greatly from increased octane, whether it be JCW or Cooper S. I think people are forgetting that even though the JCW has a half point lower compression...it is still 10:1 which is rather high. Even in stock form they will overboost up to 19-20 psi. You will see benefit and GAIN with 100 octane...trust me. It's just a matter of if you want to spend the $ on it or not.

 

In 2010 here in the UK we were lucky enough for a short period of time, to purchase pump gas with a 102 octane, (£2.50 per litre) I used this in my road going MCS Clubman, while it was available, and found after a days driving, a couple of hundred miles, the ECU had managed to self adapt to this wonderful fuel, I not only recorded cooler EGT's I got full timing advancement lower in the RPM range, where normally I wouldn't, plus my MPG increased slightly, not that the latter bothers me, so despite all you have said, regarding incomplete fuel burn robbing power, I in my testing of a regular pump gas offering a 100+ octane, found the complete opposite, The N14 engine absolutely loved it, and so did I while it lasted.

 

Higher Ron unleaded fuel = less tendency to pre ignite = Ecu self adaptation for altered advanced timing = More Power.

I own my Mini from new since 2007. Never used less than 100 Ron from day one. Currently using the Shell V-Power Racing which is known as a 102+ Ron fuel and as Czar said the results are lower EGT's and subsequently lowered combustion chamber firing temps, which can only lead to more power.
Now I also have done some testing with different kinds of fuel on a dyno at the same day so i have plenty of data logs to support my writings.

 

I never said 100 octane unleaded wouldn't work in the MINI; I said that I didn't know how well it would work. Given that you and others have first-hand experience using it, I'll have to defer to that empirical data. Perhaps the octane 'band/range' is wider than I'd initially suspected? Or my presumption that BMW/MINI had optimized the N14 engine for fuels with commonly-available premium octane ratings (i.e., 91-95) was erroneous...?

Nevertheless, there is a point where an increasing octane rating will not provide any benefit -- and will actually become a detriment -- without a mechanical change of some kind (i.e., an even higher compression ratio). Apparently, that point is somewhere above 102 octane unleaded for the N14 engine...

I think we're actually all in 'violent agreement' on this... But just to clarify (and granted, this is a subtle distinction): "more power" is a relative thing when it comes to octane. For a given fuel formulation, you can't increase the energy contained within it simply by boosting the octane. It's not the octane itself that's increasing the horsepower output; it's that in combination with the given engine design and ECU programming, which is working to optimize the engine output as best as it can. The overall system may end up more or less efficient with one octane rating compared to another, allowing you to extract more or less energy (in the form of horsepower) from a given unit of fuel. But the gasoline itself is not "more powerful" just because it's got a higher octane rating...

So to think of increased octane as a straight horsepower booster (which is the common tendency) is something of a misnomer; there's more to it than that. Just sayin'...

 

The stock ECU tune (program and maps) is not set up to take advantage of any octane over 91. The ECU could run more timing but its not in the stock map to do so by that much. Its tuned for the best performance but only second to meeting emissions standards. The proper tune could take advantage of the higher Octane fuel, with the stock maps the gains will be so low you could not feel them in the seat of your pants, well you could in the wallet when your MPG falls and after you forked out 8 bucks a gallon (over double in the US) for gas.

FYI for conversion from Euro to the US

the octane rating shown in the United States is 4 to 5 points lower than the rating shown elsewhere in the world for the same fuel.

 

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what about the boosters you add? any gains there? i know mine felt a lot better on 98 compared to 95 when it was stock.

 

This is a 2012 JCW - tune is still available. No tune for 2012 MCS with revised engine.