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Paul Maks
Guest
Guys, what is the difference between these petrols?? I know super is more expensive, but is it better for your engine??
Paul Maks
Paul Maks
Currently reading:
Unleaded or Super Unleaded??
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Anonymous
Guest
the difference is that super has a higher octane rating (more explosive. the normal stuff is 95 ron, super is 97 ron and optimax is 98 ron. the thing with shell optimax is that it doesnt seem to suit the fiat engines as has been discussed on here before. the best stuff ive found is texaco super unleaded or normal. the worst by a long way in my area is safeways stuff. put some in cos it was the nearest and i was running on fumes and it was awful...very jerky at low speeds and seemed to make the car kangaroo when u come off the power. super is really nice but i only really use it if im going to be doing most of the driving on that tank on backroads as its wasted on motorways. tesco on the other hand is ok as its just esso petrol. most are pretty good except stuff like jet etc.....and safeways!
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briang
Guest
Optimax
I think Optimax really suits the 5 pot engine, fill up with ordinary now and again, cos ive heard the electronic brain??? gradually adjusts to compensate, but then i again i could be talking complete sh*t
cheers
briang
I think Optimax really suits the 5 pot engine, fill up with ordinary now and again, cos ive heard the electronic brain??? gradually adjusts to compensate, but then i again i could be talking complete sh*t
cheers
briang
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Tom
Guest
Re: Optimax
Super unleaded actually burns slower than normal (I know, its not the way you'd expect) so unless your car is setup for running 98RON it will either have no benefit or will actually be worse.
Fiats and most ECU equiped cars are setup for 95RON fuel so running super will not get you any benefit. The ECU won't adjust for super as its set for normal. The time when the ECU will adjust is when you put some right crap in and it will change the ignition so that the engine won't suffer any damage. BUT... the ignition settings will only go back to the normal UL settings, no further.
You could get the ECU remapped (cue Nige) to suit super but then you could not run normal for more than a tankful or so as the ECU will think you've got **** petrol and it will run like a dog.
Super unleaded actually burns slower than normal (I know, its not the way you'd expect) so unless your car is setup for running 98RON it will either have no benefit or will actually be worse.
Fiats and most ECU equiped cars are setup for 95RON fuel so running super will not get you any benefit. The ECU won't adjust for super as its set for normal. The time when the ECU will adjust is when you put some right crap in and it will change the ignition so that the engine won't suffer any damage. BUT... the ignition settings will only go back to the normal UL settings, no further.
You could get the ECU remapped (cue Nige) to suit super but then you could not run normal for more than a tankful or so as the ECU will think you've got **** petrol and it will run like a dog.
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biang
Guest
thanks Tom
i do still think the engine is smoother and more responsive with Optimax, does what u say mean im merely imagining it and im and ad execs dream?
cheers
briang
i do still think the engine is smoother and more responsive with Optimax, does what u say mean im merely imagining it and im and ad execs dream?
cheers
briang
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Tom
Guest
Re: thanks Tom
Some super UL brands are better petrol and have less crap in it compared to normal (hence the cost) but if you put it on the rollers and get a BHP it would be maybe +/-1 or 2 different.
Some super UL brands are better petrol and have less crap in it compared to normal (hence the cost) but if you put it on the rollers and get a BHP it would be maybe +/-1 or 2 different.
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Anonymous
Guest
Re: Re: thanks Tom
having said that the optimax doesnt really suit my car...seems to make it run a bit oddly. the super sould be better because its a higher quality petrol with better additives...also, the manual says that its minimum of 95ron..maybe it doesnt ass to the performance, just that the engine hates less? i cant say for def as im not a petrochemical engineer
having said that the optimax doesnt really suit my car...seems to make it run a bit oddly. the super sould be better because its a higher quality petrol with better additives...also, the manual says that its minimum of 95ron..maybe it doesnt ass to the performance, just that the engine hates less? i cant say for def as im not a petrochemical engineer
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Tom
Guest
Re: Re: Re: thanks Tom
Some super is just normal with lots of added benzine to give it better octane. Others are actually better petrols.
Some super is just normal with lots of added benzine to give it better octane. Others are actually better petrols.
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Schumaniac
Guest
Re: Re: Re: Re: thanks Tom
I can tell you that the leaded petrol is best for our engines. Until last year leaded was still available in Malta and had been using it ever since i purchased my Fiat (after de-catting) which I think is responsible for the good form and efficiency of my 1.6. The engine used to be around 10% more economical, it ran smoother and used to rev better.
Leaded petrol also extends the engine life more because it is much less hard on the valves than the unleaded. As a matter of fact, leaded cars running on unleaded get their valves and rings used up in a blink of an eye.
To the dissappointment of most petrolheads here, the stuff is now gone (damn environmentalists!!)
I can tell you that the leaded petrol is best for our engines. Until last year leaded was still available in Malta and had been using it ever since i purchased my Fiat (after de-catting) which I think is responsible for the good form and efficiency of my 1.6. The engine used to be around 10% more economical, it ran smoother and used to rev better.
Leaded petrol also extends the engine life more because it is much less hard on the valves than the unleaded. As a matter of fact, leaded cars running on unleaded get their valves and rings used up in a blink of an eye.
To the dissappointment of most petrolheads here, the stuff is now gone (damn environmentalists!!)
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Anonymous
Guest
Re: Re: Re: Re: Re: thanks Tom
can u not get LRP in malta?
can u not get LRP in malta?
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chris
Guest
Tom: You talking referring to the ignition timing and the knock sensor.
higher octane fuel has a higher resistance to pre-ignition.
Are any cars manufactured for super unleaded?
higher octane fuel has a higher resistance to pre-ignition.
Are any cars manufactured for super unleaded?
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Craig
Guest
Re: Re: Unleaded or Super Unleaded??
it looks as though petrol is going up again soon.
according to itv news anyway.
it looks as though petrol is going up again soon.
according to itv news anyway.
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Tom
Guest
Re: Re: Unleaded or Super Unleaded??
Chris, please PLEASE get a clue before you post.
Chris, please PLEASE get a clue before you post.
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Tom
Guest
Re: Re: Re: Re: Re: thanks Tom
The difference is that leaded petrol, certainly in the UK, was made to a very high standard whereas UL is basically any old crap with whatever leftover benzine they have stuck in it to make it the correct octane.
Leaded petrol won't help one jot with the valve seats on modern engines, they all have stellite valve seats and stainless valves. It was requires for old engines with cast iron heads and plain steel valves.
The difference is that leaded petrol, certainly in the UK, was made to a very high standard whereas UL is basically any old crap with whatever leftover benzine they have stuck in it to make it the correct octane.
Leaded petrol won't help one jot with the valve seats on modern engines, they all have stellite valve seats and stainless valves. It was requires for old engines with cast iron heads and plain steel valves.
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Craig
Guest
Re: Re: Re: Unleaded or Super Unleaded??
i did wonder...
i did wonder...
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chris
Guest
Re: Re: Re: Unleaded or Super Unleaded??
WTF?
WTF?
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chris
Guest
Re: Re: Re: Re: Unleaded or Super Unleaded??
Think you read the thing i posted in the wrong way.
I wasn't being rude, it was a question.
Think you read the thing i posted in the wrong way.
I wasn't being rude, it was a question.
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Tom
Guest
Re: Re: Re: Re: Re: Unleaded or Super Unleaded??
Right, back to basics.
Pre-ignition and pinking are different things. Pre-ignition is when the air & fuel ignites before the spark (due to overheating of engine internals, bits of carbon etc..) and is ONE CAUSE of pinking.
Pinking is the effect of the combustion pressure reaching maximum BEFORE the piston has reached the top of its stroke. ie, while its still moving up. Basically the combustion pressure is trying to force the piston down when it still wants to go up.
Super cannot prevent or reduce pre-igniton. If something is wrong, such as VERY lean mix, and something in the cylinder (usually the plug nose or a bit of carbon) is glowing red hot it won't matter if its super, normal, leaded, 2 star, methanol etc.. it will pre-ignite.
OK, thats got that out of the way.
In order to get the maximum performance out of an engine, you need to time the spark such that the combustion pressure is at its highest a few degrees AFTER the piston has started going down again. If its too late you get bad performance, if its too early you will get pinking. This is the other cause of pinking, too much ignition advance.
Right, the higher the octane of the petrol, the slower it burns. This means for super UL you want the spark to happen EARLIER such that you get the maximum pressure at the right time.
Now, as most cars are setup for normal, when you run super UL the ignition timing will be unchanged and the result is that the maximum combustion pressure is reached later than with normal petrol. ie, the spark is not early enough as the ECU expects the faster burning normal petrol.
So, the ECU will sit there thinking 'everything is fine, no need to adjust the timing'. It knows no better.
Now, if for some reason your engine has a fault, maybe the crank sensor is out of line or its running a bit lean you may get ignition advance induced pinking. This is NOT pre-ignition though. This is where the spark happens too early.
If the ECU has a knock sensor it will go 'oh ****!' and back off the timing to stop the pinking.
In this case changing to super would help stop the pinking as super needs the earlier spark.
This pinking can also happen if you get a bad tank of petrol. The ECU will protect the engine from frying itself.
There are cars which are setup for super, a friends Turbo MR2 can only run super. In these cases the ignition timing is set correctly for super, not normal UL. Running normal UL will result in massive ignition advance induced pinking and as Matthew in his MR2 showed quite nicely it does not take long to burn a hole in a piston. I just wish I'd taken a picture.
Many years ago shell developed an 'easy starting' petrol. It had a lower flash point than normal petrol and was REALLY good for proper pre-ignition pinking. It was withdrawn after it destroyed several engines. Mostly Astras for some reason.
OK, the difference in flame speed between normal and super is quite small and most engines are setup such that they don't even make the most out of normal petrol (hence why chip tuners can get a few more BHP out of them) so changing to super won't really make any difference. As most people have noticed, there is quite some variation in petrol quality between the brands so the ECU has to be set for a compromise.
Right, back to basics.
Pre-ignition and pinking are different things. Pre-ignition is when the air & fuel ignites before the spark (due to overheating of engine internals, bits of carbon etc..) and is ONE CAUSE of pinking.
Pinking is the effect of the combustion pressure reaching maximum BEFORE the piston has reached the top of its stroke. ie, while its still moving up. Basically the combustion pressure is trying to force the piston down when it still wants to go up.
Super cannot prevent or reduce pre-igniton. If something is wrong, such as VERY lean mix, and something in the cylinder (usually the plug nose or a bit of carbon) is glowing red hot it won't matter if its super, normal, leaded, 2 star, methanol etc.. it will pre-ignite.
OK, thats got that out of the way.
In order to get the maximum performance out of an engine, you need to time the spark such that the combustion pressure is at its highest a few degrees AFTER the piston has started going down again. If its too late you get bad performance, if its too early you will get pinking. This is the other cause of pinking, too much ignition advance.
Right, the higher the octane of the petrol, the slower it burns. This means for super UL you want the spark to happen EARLIER such that you get the maximum pressure at the right time.
Now, as most cars are setup for normal, when you run super UL the ignition timing will be unchanged and the result is that the maximum combustion pressure is reached later than with normal petrol. ie, the spark is not early enough as the ECU expects the faster burning normal petrol.
So, the ECU will sit there thinking 'everything is fine, no need to adjust the timing'. It knows no better.
Now, if for some reason your engine has a fault, maybe the crank sensor is out of line or its running a bit lean you may get ignition advance induced pinking. This is NOT pre-ignition though. This is where the spark happens too early.
If the ECU has a knock sensor it will go 'oh ****!' and back off the timing to stop the pinking.
In this case changing to super would help stop the pinking as super needs the earlier spark.
This pinking can also happen if you get a bad tank of petrol. The ECU will protect the engine from frying itself.
There are cars which are setup for super, a friends Turbo MR2 can only run super. In these cases the ignition timing is set correctly for super, not normal UL. Running normal UL will result in massive ignition advance induced pinking and as Matthew in his MR2 showed quite nicely it does not take long to burn a hole in a piston. I just wish I'd taken a picture.
Many years ago shell developed an 'easy starting' petrol. It had a lower flash point than normal petrol and was REALLY good for proper pre-ignition pinking. It was withdrawn after it destroyed several engines. Mostly Astras for some reason.
OK, the difference in flame speed between normal and super is quite small and most engines are setup such that they don't even make the most out of normal petrol (hence why chip tuners can get a few more BHP out of them) so changing to super won't really make any difference. As most people have noticed, there is quite some variation in petrol quality between the brands so the ECU has to be set for a compromise.
C
chris
Guest
Re: Re: Re: Re: Re: Re: Unleaded or Super Unleaded??
thanks for the info. Was trying to learn about all this you see.
was under a few misconceptions (mostly incorrect naming) but now know correct.
cheers
thanks for the info. Was trying to learn about all this you see.
was under a few misconceptions (mostly incorrect naming) but now know correct.
cheers