adjustable ECU/Optimax - BP Ultimate
Discussion
Doesn't it need a knock sensor to fully adjust to the type of fuel? Not sure it has one?
I've not run my 94 400 on regular 95 unleaded, but am convinced of the following:
- Regular super unleaded 97 RON - runs a bit rough
- Shell Optimax 98 RON - much smoother and happier
- BP Ultimate 97 RON - smoother still with loads of low down torque
- Tesco Super Unleaded 99 RON - similar to Optimax but with more top end power than any of the fuels and, strangely, makes the car even louder!!!
In my opinion, BP Ultimate works best for my car as the engine runs really smooth and provides far more torque than the other fuels, especially at low revs. Currently using Tesco 99 stuff (very cheap at moment!) and even my girlfriend thought the car sounded louder!
Try a few tanks of one of the fuels and see what you think.
Of course, all this could just be in my head!
>> Edited by jsr on Friday 6th January 12:39
I've not run my 94 400 on regular 95 unleaded, but am convinced of the following:
- Regular super unleaded 97 RON - runs a bit rough
- Shell Optimax 98 RON - much smoother and happier
- BP Ultimate 97 RON - smoother still with loads of low down torque
- Tesco Super Unleaded 99 RON - similar to Optimax but with more top end power than any of the fuels and, strangely, makes the car even louder!!!
In my opinion, BP Ultimate works best for my car as the engine runs really smooth and provides far more torque than the other fuels, especially at low revs. Currently using Tesco 99 stuff (very cheap at moment!) and even my girlfriend thought the car sounded louder!
Try a few tanks of one of the fuels and see what you think.
Of course, all this could just be in my head!
>> Edited by jsr on Friday 6th January 12:39
No, not in the sense that you mean.
If you use higher octane petrol then you can usually afford to advance the ignition slightly, which can produce slightly more power. But this means getting the spanners out and swinging the distributor, it is not controlled by the ECU and not something that is driver adjustable.
If you use higher octane petrol then you can usually afford to advance the ignition slightly, which can produce slightly more power. But this means getting the spanners out and swinging the distributor, it is not controlled by the ECU and not something that is driver adjustable.
i used to run opti max in my evo and my tvr and found i notice little difference in both- though i swore by them for race days. after reading an artice this month (i think its in evo) i was shocked to see bp ultimate getting such a good write up! i have switched and am delighted! there is a noticeable difference low down in the rev band and top end rev band. My evo being an import is ment to run on high octane anyway but showed 6bhp more with 98 than 95 (cant remeber if it has millers additives too though) so there is a difference.
jsr said:
Doesn't it need a knock sensor to fully adjust to the type of fuel? Not sure it has one?
Quite so, and none of the TVR engine management systems use a knock sensor, IIRC it did appears on some of the very late LR V8s fited with the GEMS8 FI system but this totally different to the 14CUX engine management (and predecessors) on factory spec TVRs. The 6BHP gain, which equates to around 2% on the EVO is probably what youd expect with a small octane change and is probably all but impossible to detect, although it depends at what point in the power curve this is coming in to be fair.
Well I've just filled my Griff up with Tesco 99 and its a marked improvement over Optimax/Ultimate. It idles better from cold, has noticeably more bottom end torque, pulling a lot more readily in the higher gears at low speed, and with a lot less of the usual shunting that it did.
My Supra runs better on Ultimate than Optimax, but I've stuck some Tescos in that to see if it makes any difference. It probably won't be so noticeable as the Griff, unless I give it a lot of stick, and it's not really the weather for that at the moment
My Supra runs better on Ultimate than Optimax, but I've stuck some Tescos in that to see if it makes any difference. It probably won't be so noticeable as the Griff, unless I give it a lot of stick, and it's not really the weather for that at the moment
Shake me up judy said:
........Placebo effect?
Very possibly, this is one mother of a powerful effect that should never be underestimated! Maybe someone will come up with a straight set of comparative dyno figures on the different fuels available, on a well set-up, standard Chim / Griff, just to add a smidge of objectivity
tahiti450 said:
........Placebo effect?
Very possibly, this is one mother of a powerful effect that should never be underestimated! Maybe someone will come up with a straight set of comparative dyno figures on the different fuels available, on a well set-up, standard Chim / Griff, just to add a smidge of objectivity
Don't think so,
Filled up with the tesco stuff, because it was cheap and I was there doing a shop...
Had a nearly empty tank, and was very surprised about the difference, for the next month. even my wife noticed an improvement... For the record my griff, for some reason hated optimax, just kept stalling, revs dying to nothing when changing gey on the MOTORWAY !!!!
A friendly hijack from the griff forum he he....on reading the evo petrol article the one piece of advice I reckon is of most value is to make sure you use petrol from a busy forecourt...and that it can be better buying standard unleaded rather than ultimate/optimax that has been sitting around for a few days. And more importantly what affect this has on our assesment of the affect petrol has on our cars!! I just wonder what percentage joe public actually puts the better fuel in their cars anyway? Suppose it depends on how affluent the area is or if it's a motorway stop?
laz11 said:
.......And more importantly what affect this has on our assesment of the affect petrol has on our cars!!......
quite... like I said. If I ever get the opportunity I'll do this excercise on the rollers. Theoretically at least unless you have an adaptive ECU and knock sensors (which TVR RV8s dont),which will automatically advance the ignition in response to higher octane fuel then its hard to see how there would be any performance gain, since all the higher octane (decreased ignitability) does is permit higher compression ratios and more advanced igntion settings, both of which will produce more power but in our TVRs both are anything but automatically adjustable. Whatever differences may be apparent, without altering ignition timing at the least, must be due to other factors, about which one could only speculate.
>> Edited by tahiti450 on Monday 9th January 18:54
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