Re: Super unleaded
I very recently had my GTA remapped by Jano and had requested that it be mapped to run primarily on 95 octane since unfortunately in Ireland you can no longer purchase any higher octane than 95 (due to prohibitive tax that forced suppliers to pull out).
He told me that the primary map is now setup for 95 octane but that the ECU + sensors will still detect a higher octane rating should I actually use it and that this will be taken advantage of to some extent.
So it seems pretty clear that the GTA ECU can take advantage of higher octane when it is present.
I forgot to ask about an unmapped GTA, but I really can't imagine it would not be the case that the car would not use 98 octane more efficiently than 95. My GTA manual says to "use a minimum of 95 octane". Manuals I have seen for various cars with non adaptive CPUs clearly indicate that the car should be run specifically on 95 octane and that while they would accept 98 octane no additional performance would be achieved.
Previously my car was also mapped to be able to tolerate 95 octane and use 98 octane but I didn't think to ask this explicitly what the technical difference was between mapping for maximal use of 98 octane while also allowing fallback to safe usage for lower octane compared to my current mapping.
I have read the EVO article and a few things jumped out at me.
Higher octane in general is only going to provide a small performance increase for N/A engines, I would have guessed around 3%.
Obviously nobody is really going to notice this very easily for normal road use. However 3% is about the same increase as you get with an exhaust upgrade and will make a slight difference in extreme use like the track.
All these little increases add up!
About the EVO article:
They mention that BWM themselved had previously tested the M5 and obtained 15bhp more on Optimax than for 95 octane, but were confused by the fact that they only appeared to get a 3% difference in their own EVO tests.
Umm 3% of 500bhp is actually 15bhp, so I'm not too clear on what they were confused about.
The other thing is that the EVO article wasn't that detailed, it primarily considered the RON rating of the petrol and neglected to mention one of the most important characteristics of petrol which is the Calorific Value.
i.e. the energy that can be released from a unit of petrol.
I'm not a doctor - but I really do recommend braking later