XT660 & Fuels
 

This info may be of no interest to anyone but I thought I would share my finds anyway.

I have been doing some testing with different RON fuels to see the effects on the XT660 Motor A/F ratio & was quite surprised with the results.

I loaded a zero fuel map in my power commander & built a custom made fuel map running my bike on 95 RON fuel the recommended fuel octane for the XT660 & set the A/F ratio at 13.2:1 across the whole fuel map.

After building the custom fuel map for the 95 RON fuel I then switched to E10 10% Ethanol 91 RON fuel, I found my bike ran leaner by 4% across the whole fuel map, compared to the 95 RON fuel.

I then ran my bike of 98 RON fuel using the same custom map for the 95 RON fuel & found it ran richer by 3% then using 95 RON fuel.

So the morel of the sorry is if you dyno tune your bike on 95 RON fuel for example you need to use this grade of fuel all the time, otherwise your A/F ratio will be to lean using 91 RON fuel or to rich using 98 RON fuel.

The XT660 is supposed to run on 95 RON fuel, so the boys worried about running your bike lean should use 98 RON fuel as it will run richer by 3% then using the recommended 95 RON fuel.

My XTX does run on 91 RON fuels but I had to build a custom made fuel map to get the A/F right, I would not run it with 91 ron fuel long term, the bike did not ping after I made the custom map.

You have far to much time on your hands...






:family:

I love to know the fundmentals of motors, all this type of stuff interests me.

By doing these types of tests I have been able to tell which fuels the XT likes & why the motor seems to run better on certain days.

I've found my motor seems to run better on warm days, more smoother.

very interesting reading.
I take it you ran your tests without O2 sensor.
What would be interesting is also running it with the sensor. I wonder if the close loop fuelling will compensate for the different grade.
I know the XT's don't have a knock sensor so no auto timing adjustment. Would be interesting to know if 98 gives any power gain?

very good info. thanks

Tests carried out with a 01 ECU with no O2 sensor. With a O2 sensor I would expect the O2 sensor to lean the A/F ratio out 14.7:1 when it is in the closed loop circuit.

One thing I have also found using the same fuel grade, is my mapping is getting richer & richer the colder the ambient air temp becomes. The difference between 20 degrees C & 10 degrees C is 2% richer @ 10C.

I take it this is at normal running temperatures.
I expected the mixture to be the same once up to temp irrespective of ambient; but maybe this is common practice unless again it goes back to not having the O2.
Don't know if 2% is significant enough to make a noticeable change.

The 01 ECU does not have an O2 sensor Only ECU's 10 & 11 have O2 sensors.

A well written fuel map should have the same A/F ratio once the engine is at operating temp, the 01 ECU mapping does seem to change with ambient air temp with the motor at operating temperature. The 2% does not really make much difference, it was just really an observation.

Thanks for that info, Kev. I was very interested to read about your fuel results. I've long thought that various engines run better on particular fuels. I tried 98 in my Tenere, and thought it felt woolly, so I went back to 95.
My TTR250 runs like a bag of p** on 98, better on 95, and best on 91. Seat of the dacks, of course, imo and all that.
My '96 model Tenere was noticeably slower running 95 rather than 91. Odd, but it you have made my thoughts reasonable.
Good work, mate.