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      04-11-2013, 05:28 PM   #23
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Originally Posted by meyergru View Post
Two more differences that I know of:

1. seats differ in the lower area (US model is like standard E9x).
2. among the different codings, US model is adapted to lesser fuel and has more restrictive M dynamic mode (only if you have the M button, which it seems is not the case).

And yes, US models start in S3 while EU start in D2 (numbers mean setting, not gear). That is not a coding thing, car has to be reprogrammed to have that changed. As far as I know, there is no coding possibility to change this (I have a EU-spec E92 and would like D3 at start).
Is it really true that the US version is "adapted to lesser fuel"? The difference between European Octane and US Octane is the method used to calculate octane. The average octane available in both countries is pretty similar if I understand correctly.

If there is a tuning difference, it may have more to do with emissions or other governmental regulation?

Research Octane Number (RON)

The most common type of octane rating worldwide is the Research Octane Number (RON). RON is determined by running the fuel in a test engine with a variable compression ratio under controlled conditions, and comparing the results with those for mixtures of iso-octane and n-heptane.

Motor Octane Number (MON)

There is another type of octane rating, called Motor Octane Number (MON), or the aviation lean octane rating, which is a better measure of how the fuel behaves when under load, as it is determined at 900 rpm engine speed, instead of the 600 rpm for RON. MON testing uses a similar test engine to that used in RON testing, but with a preheated fuel mixture, higher engine speed, and variable ignition timing to further stress the fuel's knock resistance. Depending on the composition of the fuel, the MON of a modern gasoline will be about 8 to 10 points lower than the RON, however there is no direct link between RON and MON. Normally, fuel specifications require both a minimum RON and a minimum MON.

Anti-Knock Index (AKI)

In most countries, including Australia and all of those in Europe, the "headline" octane rating shown on the pump is the RON, but in Canada, the United States, Brazil, and some other countries, the headline number is the average of the RON and the MON, called the Anti-Knock Index (AKI, and often written on pumps as (R+M)/2). It may also sometimes be called the Pump Octane Number (PON).

Difference between RON and AKI

Because of the 8 to 10 point difference noted above, the octane rating shown in Canada and 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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      04-11-2013, 09:08 PM   #24
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Thanks agin

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Originally Posted by TVMA Doc View Post
Is it r
Thanks for providing detailed information. How about mechanical? is there underneath the hood and chassis?
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      04-12-2013, 03:27 AM   #25
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I know that the RON used in the EU and AKI in the U.S. differ, which is why many people think that US fuel is worse due to the lower numbers. But that was not what I was referring to (and I did not write anything about it). I also know of the difference between U.S. BHP and EU PS, which makes up for the difference in figures of 420 PS and 414 BHP, both of which are figments of imagination, BTW:

The engine was developed to put out 400 PS (like the N54, which was the other possible alternative at that time), but when it arrived, Audi already had their 4.2-liter V8 with 420 PS, so that BMW chose the same number. It is a known fact that few S65s actually develop 420 PS (if at all, only with one of the later software updates).

I already quoted the TOP TIER gas initiative, which was formed by BMW, General Motors, Honda, Toyota, Volkswagen and Audi, who "recognize that the current EPA minimum detergent requirements do not go far enough to ensure optimal engine performance", read all about it here.

I also cited the numerous N54 high pressure fuel pump failures, which have been mainly observed in the U.S. Matter-of-fact, BMW was forced to raise the warranty timelime for that part to 10 years, but ONLY in the U.S.

And, as a matter-of-fact, these are the coding settings for my EU-spec M3's ECU (MSS60):

Code:
MILANSTEUERUNG
	wert_01
MSA
	aktiv
IGR_CODIERUNG
	aktiv
KRAFTSTOFFAUSLEGUNG
	wert_01
MDRIVE_MSS
	aktiv
MODELLJAHR
	wert_06
CKM_CODIERUNG
	aktiv
OELWARTUNGSINTERVALLMSS1
	wert_01
M_BUTTON
	nicht_aktiv
As you can see, the value for "KRAFTSTOFFAUSLEGUNG" (which translates to "fuel adaption") is "wert_01", which is for EU. "wert_02" would be for US-spec vehicles, so there has to be a difference.

Thus, I tend to believe that - apart from TOP TIER fuel - U.S. fuel is generally worse than, say, fuel sold in Germany.
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