Petrol........

[tom_burnley]

Right chaps,
I have made an observation about my Elise..... until now I have mostly been using Optimax - which is supposed to improve my car performance... but after filling up with 95 RON - unable to find a shell station my car sounds a lot smoother, the growl is no longer tainted by what I only assume was the tappits..

I can only assume that the ECU was mapped for 95 RON and therefore it behaves better...

has anyone else noticed this - is it me - is there a good reason ( rather then me guessign why? )

Go on - enlighten me

[thub]

Yep, it's mapped for 95RON.
I tend to use Optimax every so often for its detergent properties. Can't say I notice any performance difference, though the car is a little 'fartier' when running it.

[Martin_S]

Purely in terms of octane rating, using higher octane fuel than what the car is set up for should make no discernable difference whatsoever, good or bad.

Using lower octane risks pinking and detonation (unless an engine has a knock sensor, in which case the ECU will simply retard the ignition until it finds a safe level, with the resulting loss of some power).

Different cocktails can burn differently enough for sensitive drivers to tell the difference though, so maybe your car just doesn't like Optimax.

[DanH]

I'm not convinced by optimax either. It sometimes causes my car to generate a petrol smell. Also not noticed any other benefits other than a lighter wallet improving performance.

[tortoise]

mmm, I put super unleaded in mine this afternoon for the first time and now the car refuses to idle (it sort of pulses between 400 and 1000 rpm then cuts out). Could be entirely unrelated to the fuel though as I was on a very wet track day at Bedford. Topped up with standard unleaded when it was half empty and it hasn't cured it so perhaps unrelated to the fuel type.

[Martin_S]

tortoise said:

mmm, I put super unleaded in mine this afternoon for the first time and now the car refuses to idle (it sort of pulses between 400 and 1000 rpm then cuts out). Could be entirely unrelated to the fuel though as I was on a very wet track day at Bedford. Topped up with standard unleaded when it was half empty and it hasn't cured it so perhaps unrelated to the fuel type.

I could be way off the mark, here, but that sounds more like a problem with the IAC valve or throttle pot. Check the wiring connections to these 2 components, as a start.