View Single Post
      03-25-2019, 06:53 PM   #5

Drives: '18 M2 6MT
Join Date: Mar 2018
Location: California

iTrader: (0)

Originally Posted by Nezil View Post
Hi nioh_lbbm2, thanks for referencing my original thread.

I'm currently running OTS 91 Stage 2 with similar mods to you. I'd like to start capturing some logs again, but haven't had time since that original thread sort of fizzled out around October last year I think. I'm also thinking that it's important to get logs in the winter as well as summer, when IATs will obviously be higher, which is why I'd not really put much priority on it.

I'm happy to hear that your gas is equally as bad as that in the Bay Area, even if that's bad news for all Californians! I remember I once got a message from Halim@HCP after looking at my logs saying that it's the worst gas he'd ever seen, far more similar to 89 than 91 in his experience (see below for why this is relevant).

I'm also pleased to see Halim@HCP is considering an ACN OTS map. There was talk of this before, but I'm not sure if he ran out of time, or I ran out of time to gather logs, but it just didn't happen.

I'm still interested in doing a more thorough investigation into CA gas. I can't believe that there is some conspiracy and we're all getting less than 91 AKI within tolerance, but I do suspect that our gas is:
a) On the low side of the allowable tolerance
b) An unfavourable balance of RON & MON (I believe MON is more important than RON, and ours may be high RON, low MON to achieve the 91 AKI
c) Lower than even BMW expects, since even the stock map results in pulled timing!
The Wikipedia page for Octane has some interesting points about alternative octane ratings that could be eye opening...

Observed Road Octane Number (RdON) is a rating based on real world multi-cylinder engines on a dyno.

Aviation rich octane rating corresponds to the octane rating of a test engine under forced induction operation, just like modern turbocharged engines like ours.

My feeling is that the AKI rating found at pumps doesn't give enough of an indication in determining the quality of fuel for turbocharged engines... there may be better ways to test than just RON and MON, and therefore AKI.

Finally, I watched this YouTube video a few months back where the owner complains about his M4 GTS and all of the problems that he's had. The M4 GTS is interesting because it's a more aggressively tuned S55 than stock, and even includes water injection to reduce IATs. Our N55s with aftermarket tunes, FMICs, DP etc. are in the same way attempting to reduce IATs and tune more aggressively. It's not apples to apples I know, but what's interesting is the comments at 7:57 where Alejandro talks to the owner talks about how even BMW accused him of buying low octane (89) fuel! I bet he didn't, and CA fuel is just worse that BMW even realises!
Wow...I hope something can change and california get's some decent gas but i highly doubt it considering the people that live here. What concerns me is that our 91 is even really 91 oct but a bastardization and seems like car manufacturers don't know that which is really concerning when a stock car with pump gas can develop knock