Unleaded or Super?

[jimmy]

What fuel should i be using in my new 4l 96(p) chimp, super or normal unleaded.? r James

[johnwilk]

Use super. It will only pink on lesser fuel or you need the timing retarded so far as to blunt the performance.

[fordy]

ive been using normal on mine for the last few tanks, it isnt pinking, and doesnt seem to have less power, but it is certainly running rougher when its cold - think im going to revert back to super next fill and see if the engine goes back to being smooth

[Don]

I always use Super 98 (or 97). Chim 450 runs great. Occasional tankfuls of 95 don't seem to make ANY difference, frankly...but I still keep pumping in the Super. My dealer (Hawthorns) told me to use Super but the odd tank of 95 in an emergency (i.e. tank nearing last quarter petrol station here but where's the next one?) wouldn't matter. And it doesn't.

[xain]

I don't think it's true to say that you lose performance *because* you retard the ignition with 95. It burns more quickly, which means it doesn't need to be as far advanced to get the same overall burn/ignition point (can't think of the right phrase) 98 has a little more poke by its chemical nature, but it's marginal I think. The reason for 98 mainly seems to be the fact that you can run higher compression ratios without risk of detonation. This can't be changed by modifying the ignition timing, as it's inherent in the fuel and engine characteristics. In fact I wonder whether in theory you get a little more out of 95 because it's more compressed when it's ignited (thermodynamics time) I did a lot of comparisons in previous cars that were designed for 98 RON and sometimes I thought I could tell the difference, mostly not. I did find though that if you back off the ignition beyond what's needed for your choice of fuel you lose a *load* of power.

[fish]

I've a 98R 4l Chimp. I've done 6500 miles in 6mths I normally fill up with 95ron and there is little noticeable difference to 98ron. I have no pinking or rough running. Although there is more burble with super on lift off. Whether mine is different to a 96P I don't know but there is no noticeable difference barr price!

[fordy]

So, all in all it seems there is no noticable power difference or idle/reving quality with the higher octane super - but if minor pre detonation is happening from the 95 Ron stuff, you may not hear it due to the high exhaust/engine noise anyway, but this minor detonation could cause long term damage to the pistons/vavles/bores,etc so its probably best to use super most of the time, as TVR suggest - although im sure the odd tank of 95 wont hurt.