Super Unleaded

alexs2

Well-known Member
trashbat said:
lol had a bad experience with super unlead once. because it burns quicker and fiercer the exhaust gases couldn't get out quick enough resulting in £80 for a new backbox and fitting and £100+ for recovery. Not good :devil:
I'd say your exhaust must have been in need of replacement for that to happen,as in terms of octane rating etc,it's the higher benzene content of super unleaded that's responsible,which if anything burns slightly slower than octane.
 

skap7309

Banned
just to everyone who took part in this post......just watched fifth gear and they did a test on optimax, bp ultimate and supermarket fuel on three cars:- a 81bhp clio, a 172bhp golf gti and a subaru impreza with 235bhp. They connected each up to a power/tourqe machine a did six runs for power increase only, each time resetting the ecu. Here are the results;
Clio- supermarket 81
BPU 81
Optimax 81

Golf-supermarket 172
BPU 174
Optimax 177

Impreza-supermarket 235
BPU 247
Optimax 249
As you can see, optimax is a winner but they did a tourqe test on the subaru to decide a clearer winner, optimax was well ahead of ultimate. (cant remember the exact figures) Thing is, looking at this your car needs to be powerful in the first place, as they pointed out if your car is geared to be economical a difference is non-existent. After 2 years of umming and arring wether optimax was better for my 1.6 90bhp xsara, its back to good old standard for me (although still steering clear of 'supermarket' petrol) the next time i fill up.
 

alexs2

Well-known Member
skap7309 said:
just to everyone who took part in this post......just watched fifth gear and they did a test on optimax, bp ultimate and supermarket fuel on three cars:- a 81bhp clio, a 172bhp golf gti and a subaru impreza with 235bhp. They connected each up to a power/tourqe machine a did six runs for power increase only, each time resetting the ecu. Here are the results;
Clio- supermarket 81
BPU 81
Optimax 81

Golf-supermarket 172
BPU 174
Optimax 177

Impreza-supermarket 235
BPU 247
Optimax 249
As you can see, optimax is a winner but they did a tourqe test on the subaru to decide a clearer winner, optimax was well ahead of ultimate. (cant remember the exact figures) Thing is, looking at this your car needs to be powerful in the first place, as they pointed out if your car is geared to be economical a difference is non-existent. After 2 years of umming and arring wether optimax was better for my 1.6 90bhp xsara, its back to good old standard for me (although still steering clear of 'supermarket' petrol) the next time i fill up.
Much as I said earlier in this post,but you'll notice that even the maximum increase amounted to less than 7% overall,with the most powerful of the selected cars,and also included an ECU reset to take into account the fuelling changes.

That alone could easily account for the increase,if the fuel/boost mapping was appreciably altered,which,looking at the results for the normally aspirated engines Vs the turbo,it very likely was.
 

The Dude

Distinguished Member
all they did was an ECU reset alex2...

ECU's learn as they go and adjust fuelling to the fuel/air in use, so the reset serves only to set everything back to default values and start the whole process again from scratch.

They didn't performance tune the ECU on the scooby to frig the results... :rolleyes:
I'd actually say the results if anything dis-prove your theory, and agree with the many posters who say they can feel the extra performance Optimax etc bring, in a variety of modern cars..

You think a 7% performance gain is a small matter, and just for filling up from a different pump??? :rotfl:

How many £100's would you have to spend on engine tuning to gain a 7% BHP increase, along with an extra 15% (approx) torque..!

:hiya:


The fact is that any car with a decent ECU is likely gonna noticably benefit from using higher octane (slower burning) fuel, whereby the ECU can achieve much greater control of the (pre)ignition process resulting in more power and torque, as proven by the fifth-gear dyno tests....

what is it you don't want to believe about the results, that ECUs have moved on a bit in the last 20 years? :D
 

markymark34

Well-known Member
i never noticed any difference in the performance of my car no mater what petrol i ran - only difference was in my pocket!

that was a MR2 Turbo with 230bhp. And i reset the ECU each time i tried a different fuel.

The 5th gear findings were interesting, would be good if they had done an mpg comparrison as well.


mark
 

alexs2

Well-known Member
The Dude said:
all they did was an ECU reset alex2...

ECU's learn as they go and adjust fuelling to the fuel/air in use, so the reset serves only to set everything back to default values and start the whole process again from scratch.

They didn't performance tune the ECU on the scooby to frig the results... :rolleyes:
I'd actually say the results if anything dis-prove your theory, and agree with the many posters who say they can feel the extra performance Optimax etc bring, in a variety of modern cars..

You think a 7% performance gain is a small matter, and just for filling up from a different pump??? :rotfl:

How many £100's would you have to spend on engine tuning to gain a 7% BHP increase, along with an extra 15% (approx) torque..!

:hiya:


The fact is that any car with a decent ECU is likely gonna noticably benefit from using higher octane (slower burning) fuel, whereby the ECU can achieve much greater control of the (pre)ignition process resulting in more power and torque, as proven by the fifth-gear dyno tests....

what is it you don't want to believe about the results, that ECUs have moved on a bit in the last 20 years? :D
I think you'll find that the mapping is held in ROM on the ECU,and I did say reset.....if as you suggest,it learns as it goes,then a reset would in any case be worthless.
Most ECU's,even motorsport ECU's do not so much learn as they go,but react to the conditions at the time,in terms of fuel pressure,throttle opening,air temperature,flow and in some cases barometric pressure etc,and use those to determine the duration of injector opening,and ignition timing to suit.
The fuel/air mapping is held in ROM as mentioned above,and the data held there is used by the ECUs processor.

If you have any doubts about that,I can give you a few names which may help,including one of the more advanced ECU manufacturers supplying the motorsport industry here and abroad.


As to how much you'd have to spend to gain a significant increase in power....with a previously unaltered turbo engine,as little as £100 would produce that with ease.

You should also note that I said the "maximum" increase in power was 7%,and that was only seen with the turbo engine,and not with the normally aspirated engines,where the best result was 2.9%.

I don't doubt the results obtained,nor that ECUs have come a long way in 20yrs(.....most cars 20yrs ago didnt have ECUs )but it is clear that the gains other than with turbo engines are small,and if you speak to any decent engine builder,they'll tell you that gains of less than 5% arent really noticeable by most users.
 

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