Fuel
 

Hi all
I'd like to know what petrol everyone uses I.e normal unleaded or the dear stuff super unleaded. My dealer says just normal unleaded but the book says otherwise.

I use normal unleaded, however I know someone who used the expensive (more so) stuff and the ten didnt like it. It caused chugging and spluttering. When he changed back to normal fuel his ten was fine!

No idea if anyone else has found this though....could just be a one off, you know dirty fuel or something.

95 Octane...
 

I was under the impression that the XT660 engine is designed for minimum octane rating of 95.

I run mine on 98, (BP Ultimate) and it gives no problems. I have heard of people having problems with Shells premium petrol, something along the lines of it being designed for cars and not bikes?? Never tried it myself...

Kev might be able to help you with more specifics. Cheers, Boneman...

The mapping on the XT660's have been designed to run on 95 RON fuels.

I once did A/F ratio testing between the different fuels RON ratings using the same brand of fuel & could see that the same bike running on 98 RON ran a bit richer than on 95 RON, the 91 Ron A/F ratio was leaner than using 95 RON.

There is a post in the modification index.

Engine & performance mods

19/ Different RON Fuels

I use 98RON (or accasionally 99RON from Tesco) and find it to pull a little bit more cleanly between 2000 and 3000 rpm; less stuttering! The difference was apparent both before and after fitting a Kev mod and DNA filter and top. I'd guess that (as Kev indicates) that it runs a tad richer on 98 and it might help richen the closed loop fuelling a smidge?? Could be the placebo effect though! ;) Interestingly my V8 Land Rover runs like a pig on 98RON, and my BSA likes 102RON (98 + octane booster).

As for bad fuel, it may be the case, I had a really bad tankful from my local Esso station (not a supermarket) two weeks ago (in the Land Rover) and it felt like the HT side of the ignition was breaking down, ran on any number of cylinders from 5 to 8 up to quarter throttle and ticked over like a lawnmower!

Whatever's cheapest. Normally just 95RON. It's a big single donk, not a high performance engine. I'd run it on chip fat if I could :)

The reason manufactures recommend a fuel rating is the engine was tunned for the that specific RON rating, the ignition/fuel/compression ETC map was built to run on that rated fuel.

It is of no use building a fuel map on 98 & then run your bike/car on 95, the A/F ratio will be out.

i use 98 bp ultimate

I went for a Dynorun some time ago.
The guy asked me to put higher octane in beforehand.
I'm assuming this was to get a better HP 'score', and that I'd have to put the same, more expensive fuel in from then on.

.... Just curious.

As I always just put the cheap stuff in.
When I go for my long overdue next dyno session I'll be putting the cheap stuff in, as I'm not worried about my HP on the dyno just the correct A/F bit.

Question: If using PC, would there be any HP gain from tuning a bike to run higher octane fuel - compared to a bike tuned to run on the cheap stuff?

I use 95 octane caltex, I have found the bike surges if I run it on Shell 98 V-Power. If BP ultimate 98 was sold out my way I would give it a try. I had a 2001 2.7 4x4 Hilux a few years ago and found I got best economy using 95 octane, it drank 98 octane and 91 made it lack power and returned poor economy.