Hi, everyone. Got the car custom mapped today. Mappers said that the ECU was adjusting timing straight away under any acceleration at all. Back to 11 degrees. He sorted it out great but it was still doing it a little bit at the top end.

We put this down to the fuel, Does it really make that much of a difference? It was half Tesco half Texaco standard petrol in the tank. I usually drive the car on Maxol E5 so it's a little higher octane. Will this improve it.

He didn't want to push it too hard because of this.

Ended up with 211HP @ 5500RPM and 240ft lbs torque holding at 225ft lbs right up past 4000RPM. So I'm delighted with that but just wondering is there anything else that would cause the knock sensors to kick in?

Sorry if it's a stupid question, it's something in which I don't have much of an understanding... :think:

Thanks

Michael

If it was pinking that bad then i would have not have had it mapped until problem was sorted,

I would start by putting it back to standard then checking fuel pressure as thats most common cause of pinking problems

Yes the fuel grade has a big effect. The ron number is a direct relation to it's resistance to det.

I'm really surprised he left it and although the knock sensor should cope the damage it can cause is huge

The E5 is 99ron but using ethenol reduces the calorific value of the petrol. Its better than 95 but not as good as say V power 98. Truth is that over here the maxol stuff is the best your going to get (at least readily available) Topaz is the same as maxol IIRC

Edited 23 January, 201313 yr by Frisco

At the point it was doing the above then the mapper should have stopped as something isnt right !!!! You can't map around a problem it will only cause issues

If it was pinking that bad then i would have not have had it mapped until problem was sorted,

I would start by putting it back to standard then checking fuel pressure as thats most common cause of pinking problems

Is it fuel pressure being too high or low? This would be pressure regulator related?

Once we confirmed the fuel in the car he was satisfied that was what it was. And I always use the E5 from Maxol just happened that last 2 fills were not there. will make sure that I fill there from now on.

The simple answer is yes, the fuel can and will make a big difference and if the ecu isn't happy with the amount of activity from the knock sensors then it will pull timing to try and save your engine.

There are many other things that can and do cause knock, but the fact you have mixed 2 not so great fuels, is the first thing to look at.

Cheers Cossie. That's what I assumed. I have been on the road at silly hours of the night the last few weeks and just had to get whatever was going at 4am. I think the fuel Tesco use in Ireland is pretty poor compared to the UK. It is back on E5 now anyway and seems to be running great. So hopefully just forget about it. It's a pity I didn't have the Maxol fuel in it for the rolling road.