Fuel octane rating, and other stuff

[a5678]

In the back of Driving Ambition, the suggested fuel octane rating for the McLaren F1 is 95-98 RON unleaded. What I want to know is how often do you come along gas stations that offer octane ratings higher than 93 ? I assume 98 is the recommended octane rating.

[cabrio92]

Hello,

I am not a specialist and it is hard to explain in english, it seems that it exists RON (Research Octane Number) and MON (Motor Octane Number).

The "real" Octane number would be the adition of these two numbers and divide by 2 like this :
(RON + MON)/2

In France for example :
RON = 95 and MON = 85 ==> octane 90
RON = 98 and MON = 88 ==> octane 93

I hope that is true if I am wrong please correct me.
Maybe in USA, 93 is the real octane number ?

Ciao
Phil

[drPhibes]

when it is listed that a car requires a specific octane rating, it's the RON that's referred to.

[drPhibes]

btw, the us is known to have lower quality fuel than e.g. europe, and as far as I know (I haven't lived in the us for 12 years) octane ratings are generally lower than the ones commonly used in europe. an american engine will thus not be able to run the same compression ratios as it's european equivalent without adding some form of octane booster to the fuel.

[a5678]

What happens if you can't find a gas station nearby with 95 and higher octane gas ? Do you put 93 RON in the F1 ?

[drPhibes]

if you run a fuel with too low octane rating, without using some kind of octane-booster, and the engine managment doesn't have some kind of knock sensor (or if you don't have an engine managment system at all - as in a carburetted engine), you will get what is commonly known as engine knock, meaning that the fuel ignites due to high compression before the spark plug fires, resulting in some quite heavy damage to the engine (I've seen everything from cracked valves to completely destroyed pistons - a complete engine rebuild will often be needed).

if the engine managment system has a knock sensor incorporated, the ecu will decect it, and reduce the amount of fuel and air injected to the cylinders, saving the engine from damage, but the power output is reduced quite a lot.

[Stratoraptor]

do the AmeriTech F1 have a knock sensor in its ECU?

[Peloton25]

The ECU in the F1 was built and programmed in house by McLaren - known as TagTronic. There's absolutely no way that it was replaced with something different in any of the Ameritech F1s. I'd be willing to bet that it has a knock sensor as well as every other useful sensor you can think of.

>8^)
ER

[Stratoraptor]

so what is the MON octane rating for an F1?

[a5678]

I'm just curious. Is that 93 RON he's putting in LM 3 ?
So the LM has a knock sensor, but like drPhibes said the power output is reduced.