Power Gains from shell optimax?
- Thread starter Swallow
- Start date
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K11_Dave
Guest
I use Sainsbury's Super Unleaded (gotta get my nectar points!) Noticed slight increase in MPG. Never tried Shell - too expensive around here 
goldstar0011
Ex. Club Member
bit off topic but is it better to stick to one type of brand, I been using BP unleaded standard for about 4 months
Yeah its cheaper to buy stainsbury's super unleaded than shell's standard unleaded around here!!
However i've just filled mine with standard unleaded and she seems to by flying at the moment! not sure whats different, but i have honestly noticed a difference in performance - I rag my car everywhere so its not a change in my driving
However i've just filled mine with standard unleaded and she seems to by flying at the moment! not sure whats different, but i have honestly noticed a difference in performance - I rag my car everywhere so its not a change in my driving
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Slim
Guest
i find BP standard works the best in my toyota
I've been using shell optimax for quite a little while now. On possibly the first tank full, the car doesn't feel much different... but after you have put a couple of tank fulls in, you can feel a difference in performance.
My K10 isn't quick at all, unless you rag the balls off it... but when I put the optimax in, it gives better throttle response at low RPM. The only dodgy thing about it is the price, but I'd say it's worth it for me for the amount of difference it makes.
-Elliot
My K10 isn't quick at all, unless you rag the balls off it... but when I put the optimax in, it gives better throttle response at low RPM. The only dodgy thing about it is the price, but I'd say it's worth it for me for the amount of difference it makes.
-Elliot
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Herr_spl1ff
Guest
Optimax is a higher octane rating so if memory serves you will see a difference on non cat engines after regular use. Won't see an immediate effect as you need to flush the system through a bit. I believe you can/have to also advance the timing to make better use of it but don't quote me on that...
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Slim
Guest
no you shouldnt. you should use normal 95 octane.
If your gonna use super unleaded in older cars like ours, you need to advance the timing by a few degrees to get the full benefit.
Asa rule, if your using a car that takes 4 start (97 octane) and runing on unleaded you retard by 3 degrees, so therefore you can crank your timing up 3 degrees and see a lot better running.
However = K10's dont like riunnnig more advace than necassary, it seems to promote smoking and bearing rumble.
If your gonna use super unleaded in older cars like ours, you need to advance the timing by a few degrees to get the full benefit.
Asa rule, if your using a car that takes 4 start (97 octane) and runing on unleaded you retard by 3 degrees, so therefore you can crank your timing up 3 degrees and see a lot better running.
However = K10's dont like riunnnig more advace than necassary, it seems to promote smoking and bearing rumble.
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Slim
Guest
there isnt really any point in using super unless yoru car's set up for it
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Jim
Guest
same here, on the inside of my fuel flap thing, it says "super 97". so surely, if that is what is recommended, that is what the car has been set up for?
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barry c
Guest
Actually high octane fuel will not give you a power boost at all. If you use it and get your ecu retuned you may see a fractional increase in performance. If you use a jap spec car here it will be slightly down on power unless you can find some 100 octane fuel. If you use a uk spec car with high octane fuel it wont make any difference because the ecu isnt tuned for it. As far as i know (cant remember everything from college) higher octane fuel allows you to andance the ignition more and get a better more efficient burn for the mixture.
James
Chairman
Backed up by something i found on the 106 Rallye forum:
[quote="Slik" from the 106 Rallye Register]Right then where do I start....
Octane as those of you who have chemistry will know is a molecule in itself (8 carbon atoms, 18 hydrogen).
Better fuel for burning has more multi branch molecules as these burn more stabily, and octane with branches I believe is considered the optimum for engines. Though it has been a few years since I have done organic chemistry or petrochemicals.
Octane rating hence determines the way the fuel burns. 95 ron has to have the ignition retarded as it is less predictable and reacts to hot spots in the chamber. Hence with higher octane rating you can run advanced timing and through this you can increase the power level cos you ignite the fuel closer to the top of the stroke, or thereabouts.
I would never use anything under 97 ron for turbo applications as due to the increased compression ratio they are susceptible to predetonation (pinking), usually down to a hot spot in the cylinder combined with the increasesd compression (like diesel petrol is more combustable when compressed). Indeed you will not be advised to run less than superunleaded on WRX or Cosworth or anything else.
And like the previous post sais, pinking causes the igniting fuel / air to push against the engines rotation putting strain on components.
Higher octane, more stable detonation, further advanced timing = more power.[/quote]
[quote="Slik" from the 106 Rallye Register]Right then where do I start....
Octane as those of you who have chemistry will know is a molecule in itself (8 carbon atoms, 18 hydrogen).
Better fuel for burning has more multi branch molecules as these burn more stabily, and octane with branches I believe is considered the optimum for engines. Though it has been a few years since I have done organic chemistry or petrochemicals.
Octane rating hence determines the way the fuel burns. 95 ron has to have the ignition retarded as it is less predictable and reacts to hot spots in the chamber. Hence with higher octane rating you can run advanced timing and through this you can increase the power level cos you ignite the fuel closer to the top of the stroke, or thereabouts.
I would never use anything under 97 ron for turbo applications as due to the increased compression ratio they are susceptible to predetonation (pinking), usually down to a hot spot in the cylinder combined with the increasesd compression (like diesel petrol is more combustable when compressed). Indeed you will not be advised to run less than superunleaded on WRX or Cosworth or anything else.
And like the previous post sais, pinking causes the igniting fuel / air to push against the engines rotation putting strain on components.
Higher octane, more stable detonation, further advanced timing = more power.[/quote]
Andrew
Club Member
Detonation is a little bit more serious than strain and pushing the wrong way... it's a violent explosion at the worst time of the cycle. It's what causes melted pistons, blown head gaskets and ruined engines.
If the engine is designed for 95 RON, there is little point in using 98 RON or higher and then advancing the timing... you won't gain significant amounts of power simply by doing this. Where it is useful is in high compression engines (e.g. a forced induction engine has a high effective compression ratio or a high tune NA) because increasing compression increases power greatly.
If the engine is designed for 95 RON, there is little point in using 98 RON or higher and then advancing the timing... you won't gain significant amounts of power simply by doing this. Where it is useful is in high compression engines (e.g. a forced induction engine has a high effective compression ratio or a high tune NA) because increasing compression increases power greatly.
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Beachboy
Guest
i have learnt that high octane fuel is less flamable than the lower octane variety. the additives of flame retardent create the stable chemistry.
