Quote:
Originally Posted by frankchn
I can't find any recent sources, but according to a C&D test of 87 vs 91 done back in 2001, the E46 M3 with the S54B32 suffered a 6.6% drop in "track performance", but that is running with gas 4 points below the minimum requirement (I believe S54 has the same minimum 91 requirement as the current M5).
So I am guessing (without any real evidence) at worst horsepower will drop 5% or so perhaps? Not sure my butt dyno is accurate enough to measure that on the roads  |
This is the point I am trying to make. NA cars and FI cars are already a night and day in terms of how they are affected by octane (FI much more sensitive). But the latest FI cars are highly sensitive as they are tuned for more boost and timing to make the more powerful outputs we see today (and requisite performance). They are tuned for optimal performance on 93. The latest GTR's which added boost from the CBA 09-11 cars of 10.5 psi to 15 psi for the latest DBA cars is an excellent example as Motortrend tested the car many times in Cali and the results were so poor they started to add octane booster (to the Porsche's as well). For those trying to save some money on fuel - I suggest not buying these FI cars as you won't get the performance they are capable of. As to "evidence" - I would suggest asking any experienced Tuner who builds quick and fast cars. I have been racing for 30 years - and this is a very well known, basic concept. All of my cars tuned for street on 93 would ping if I got into boost on 91 - even with ECU adjustment. It's a big difference with the more powerful/higher boost FI cars. That said - if you are getting a new F90 M5 and don't think it's an issue - it is your car to test that theory with.