Correct Fuel...?
Discussion
LewisScoob said:
Here's my 2p worth... 
The manuals may state 95 or 98 for WRX and STI repectively but a vehicle maketed in the UK must be able to run on 95 fuel.
If a car is run on 95 from day one then the ECU will have corrected timing, ignition etc to suit and start its learning process from there. Throw 98/99 in a car thats been ron on 95 all its life and it will start performing a little better and the ECU continues to learn the new setup for new fuel. Conversely, if you take a car thats been run on 98/99 all its life and run it on 95 then you run the risk of det which as Simon rightly stated, puts holes in pistons. Maybe not stright away but thats dependant on driving 'style' more than anything IMO.
Finally, to the OP. It wouldnt be running 95 and cruising that kills your car but cruising at 120 on a std top mount intercooler almost definitely will. These cars were not designed with sustained 000 speeds in mind and the limited airflow a standard scoop can draw in will not be sufficient to cool charge temps and before you know it your throwing hot air in the inlet and pop!
The learn process is an algorithm not a creature that grows and learns a gains experiance. The manuals may state 95 or 98 for WRX and STI repectively but a vehicle maketed in the UK must be able to run on 95 fuel.
If a car is run on 95 from day one then the ECU will have corrected timing, ignition etc to suit and start its learning process from there. Throw 98/99 in a car thats been ron on 95 all its life and it will start performing a little better and the ECU continues to learn the new setup for new fuel. Conversely, if you take a car thats been run on 98/99 all its life and run it on 95 then you run the risk of det which as Simon rightly stated, puts holes in pistons. Maybe not stright away but thats dependant on driving 'style' more than anything IMO.
Finally, to the OP. It wouldnt be running 95 and cruising that kills your car but cruising at 120 on a std top mount intercooler almost definitely will. These cars were not designed with sustained 000 speeds in mind and the limited airflow a standard scoop can draw in will not be sufficient to cool charge temps and before you know it your throwing hot air in the inlet and pop!
It will run the same algorithm now and when new whether you run it on 95 or 99.
The ecu is usually reset all learnt data every service when they disconnect the battery.
Driving your scoob for extended periods at 120mph doesn't do the car any harm so long as you give it plenty time to cool off as you slow down when getting nearer to your destination. Your car is more than capable of sustaining those speeds without ill effect all day if it needs to.
Same principle as when on a track and you do a cool down lap or two depending how hard it's been driven. Track work is a lot harder and hotter on the car than travelling at steady state on the motorway at 120mph, on part throttle, and a very little way into your boost parameters, just a few psi.
It doesn't matter what fuel you're using, if you have to slow down right down/stop straight after those speeds, AIT and engine temps rise very quickly coupled with shedloads of TMIC heat soak from the turbo and that can lead to some serious detting, sometimes just pulling away under light loads you will get low level det and your car will cough and splutter when it's really bad. I've seen this lots of times, specially when mapping in very hot weather having just been in a queue for 15-20mins.
I've got a temp sender in my TMIC right at the point where it joins to the throttle body and it's fair to say the scoop does an incredibly good job on the move, even at 30/40mph. At 120mph the cooling effect through the scoop will be massive and keep intake air temps properly right down. Airflow outdoors is completely different to airflow on a garage rolling road so where you might see high IAT's on the rollers, even with a massive fan at full chat, you won't see those temps outdoors and on the move, even on a hot day.
Same principle as when on a track and you do a cool down lap or two depending how hard it's been driven. Track work is a lot harder and hotter on the car than travelling at steady state on the motorway at 120mph, on part throttle, and a very little way into your boost parameters, just a few psi.
It doesn't matter what fuel you're using, if you have to slow down right down/stop straight after those speeds, AIT and engine temps rise very quickly coupled with shedloads of TMIC heat soak from the turbo and that can lead to some serious detting, sometimes just pulling away under light loads you will get low level det and your car will cough and splutter when it's really bad. I've seen this lots of times, specially when mapping in very hot weather having just been in a queue for 15-20mins.
I've got a temp sender in my TMIC right at the point where it joins to the throttle body and it's fair to say the scoop does an incredibly good job on the move, even at 30/40mph. At 120mph the cooling effect through the scoop will be massive and keep intake air temps properly right down. Airflow outdoors is completely different to airflow on a garage rolling road so where you might see high IAT's on the rollers, even with a massive fan at full chat, you won't see those temps outdoors and on the move, even on a hot day.
I believe it's the case that all cars marketed in the UK have to be able to run on 95 octane. You will note the Subaru handbooks state that higher octane fuels are recommended to get the full performance from the engine. Running on 95 should not damage them, they just won't give full power on the lesser fuel. Having said that, I'd only ever use Vpower in my Subaru except in an emergency. I also use it in my non-turbo cars because of the good detergent package.
Why? The fact is 95 octane will not harm an unmodified car. My Subaru manual says for turbo cars 'use an octane rating of 95 or higher' despite the fuel filler flap specifying 97 only.
The seems to be some confusion between what fuel will give the best performance and whether 95 RON will cause any damage. It won't unless your car has been remapped and the map doesn't allow for it. But you will lose performance.
End of story.
The seems to be some confusion between what fuel will give the best performance and whether 95 RON will cause any damage. It won't unless your car has been remapped and the map doesn't allow for it. But you will lose performance.
End of story.
rovermorris999 said:
Why? The fact is 95 octane will not harm an unmodified car. My Subaru manual says for turbo cars 'use an octane rating of 95 or higher' despite the fuel filler flap specifying 97 only.
The seems to be some confusion between what fuel will give the best performance and whether 95 RON will cause any damage. It won't unless your car has been remapped and the map doesn't allow for it. But you will lose performance.
End of story.
The general consensus from all respected people who work on these cars is 97 or above.The seems to be some confusion between what fuel will give the best performance and whether 95 RON will cause any damage. It won't unless your car has been remapped and the map doesn't allow for it. But you will lose performance.
End of story.
JollyGreen who has actually posted on this thread is one of the most respected engine tuners out there and has said as much and thats good enough for me.
For me it a bit of a no-brainer what to do.
Indeed. I agree with you. I always use Vpower. But my point is on an unmodified car it will not damage it to use 95 ron as the manufacturer states. That doesn't mean it's desirable to use it on a regular basis. But if you are caught short have have to use 95 ron you're not going to hurt the engine.
I'm pretty sure it is a legal requirement that all UK-marketed cars have to be able to to this. If I could be arsed to look I'd dig it out but inertia is kicking in.
I'm pretty sure it is a legal requirement that all UK-marketed cars have to be able to to this. If I could be arsed to look I'd dig it out but inertia is kicking in.
Edited by rovermorris999 on Monday 8th October 09:59
I think your previous post of 'I give up' was the correct one. There's only so many times you can keep banging your head against a wall before you cause permanent damage. 
If people want to keep using 95RON in their cars, and they won't be persuaded otherwise that it isn't the best idea in the world then that's up to them. More work for the likes of API and ScabbyClinic, and tuners thereafter.
For the cost difference of a pound or thereabouts per tank it's going to be a fair few tanks worth before said tight arses have saved enough money for a rebuild...lol...
What makes me laugh is that some people seem to think that as tuners we're talking things up to make more money from providing remap services when actually what we're doing is trying to get people using the right fuel to avoid having to spend money having their cars remapped, avoid spending a small fortune in rebuild costs, and avoid all the grief that comes with a very sickly subaru!!
They should make a spaghetti western out of this thread......
"For a Few PPL More"
"The Good, The Bad, and the 95RON",
"A Fistful of Pistons"
"For a Few Bearings More"
"I am 95RON, Your Angel of Death"
"A Reason to 99RON, A reason to 95RON"
The list goes on and on.....
If people want to keep using 95RON in their cars, and they won't be persuaded otherwise that it isn't the best idea in the world then that's up to them. More work for the likes of API and ScabbyClinic, and tuners thereafter.
For the cost difference of a pound or thereabouts per tank it's going to be a fair few tanks worth before said tight arses have saved enough money for a rebuild...lol...
What makes me laugh is that some people seem to think that as tuners we're talking things up to make more money from providing remap services when actually what we're doing is trying to get people using the right fuel to avoid having to spend money having their cars remapped, avoid spending a small fortune in rebuild costs, and avoid all the grief that comes with a very sickly subaru!!
They should make a spaghetti western out of this thread......
"For a Few PPL More"
"The Good, The Bad, and the 95RON",
"A Fistful of Pistons"
"For a Few Bearings More"
"I am 95RON, Your Angel of Death"
"A Reason to 99RON, A reason to 95RON"
The list goes on and on.....
Work of art!! Nicest looking Rover V8 lump i've seen in a very long time.
Last year i worked on one of these running a Megasquirt in a Dax Rush. Didn't like 95RON at all, even using shots of Lead Replacement. Started using 99RON and shots of lead replacement and it made all the difference although still not the same as running 4* or 5* in the good old days.
The engine was designed to run a minimum of leaded 4* petrol which was rated at 98RON or you could/should use 5* at 101RON.
95RON unleaded makes it run like a bag of s
te regardless of what you do with fuelling and timing.
Last year i worked on one of these running a Megasquirt in a Dax Rush. Didn't like 95RON at all, even using shots of Lead Replacement. Started using 99RON and shots of lead replacement and it made all the difference although still not the same as running 4* or 5* in the good old days.
The engine was designed to run a minimum of leaded 4* petrol which was rated at 98RON or you could/should use 5* at 101RON.
95RON unleaded makes it run like a bag of s
te regardless of what you do with fuelling and timing.Edited by ScoobieWRX on Monday 8th October 21:56
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