all Scoobs CAN run on 95 octane,you are all dumb
13 January 2003, 12:42 PM
#31
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I tend to always run SUL or Optimax, but carry a can of Octane Booster with me just in case I can't get it. I travel to the east cost quite a lot during summer where it is very difficult to SUL
I have had no problems with mine on 95 however, but I don't use it often anyway
I have had no problems with mine on 95 however, but I don't use it often anyway
13 January 2003, 01:40 PM
#32
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I am not an engine expert but the way it was explained to me was that the petrol should ignite when the piston reaches the top of the cylinder obviously to push it back down. If you use to lower grade fuel for the ignition timing then the fuel ignites before the piston reaches the top. So the piston is coming up but also being pushed back down at the same time. This would generate heat which eventually would melt the piston over a period of time.
The ignition timing use the knock sensor to determine the timing to be used.
On the imports the ignition timing cant be retarded enough to cope with 95 RON fuel so the engine stands the risk of pinking/dettings until the piston melts and the engine goes.
On standard UK cars (normal turbo) the ignition timing can be retarded to handle 95 RON, apparently. This means though if you reduce the ignition you are down on power. Always safe to run good fuel though IMHO as it protects the engine and gives more power/better running.
Please correct me if I wrong as I am always willing to learn.
Cheers
ChrisP
[Edited by chrisp - 1/13/2003 1:49:38 PM]
The ignition timing use the knock sensor to determine the timing to be used.
On the imports the ignition timing cant be retarded enough to cope with 95 RON fuel so the engine stands the risk of pinking/dettings until the piston melts and the engine goes.
On standard UK cars (normal turbo) the ignition timing can be retarded to handle 95 RON, apparently. This means though if you reduce the ignition you are down on power. Always safe to run good fuel though IMHO as it protects the engine and gives more power/better running.
Please correct me if I wrong as I am always willing to learn.
Cheers
ChrisP
[Edited by chrisp - 1/13/2003 1:49:38 PM]
13 January 2003, 03:52 PM
#33
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it reads to me " eariler combustion transfer maximum energy to the piston , the crankshft and road wheels " , therefore more power/energy is applied to the piston , crankshaft , = working harder ,,,,
Thats NOT the same as saying higher RON gives bigger bang
which is, of course rubbish 
Earlier combustion reads to me as more ignition advance, ie earlier spark in combustion cycle. Which is what I said higher RON allows.
Sure, more energy = working harder, never said it wasn't.
Doh...People who question posts questioning posts should read more carefully
13 January 2003, 04:08 PM
#35
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Chris - thats not quite right.
The best power will be created if the spark ignites the air/fuel mix just before TDC (top dead centre) The actual timing is dependent upon a lot of things - flame front characteristics, head design, revs, etc.
Fuel air ignition is not a simple instant bang, so ideally you want it to start before TDC and be discharging maximum energy at or fractions after tdc (may be wrong on this exact point)
Higher ron fuels burn in a more controlled fashion and are less volatile at the top of the compression stroke hence the spark can
be advanced to provide more efficient and powerful cycle.
As I have said above (and had questioned) higher ron petrol does not necessarily provide a bigger bang, just a more controlled and less volatile one.
Run too much advance and you get the scenario you described which is very bad. You'll also get that happening in some cases as lower ron fuel which is less stable can pre ignite before the spark under high compression and exposure to heat - albeit in pretty extreme circumstances.
It has been commented on here that STI7s UK22b's etc will det like mad on 95 Ron fuel. Probably due to insufficiuent ignition advance control/knock protection. But then Scoobs never had the highest of tech engine management.
D
The best power will be created if the spark ignites the air/fuel mix just before TDC (top dead centre) The actual timing is dependent upon a lot of things - flame front characteristics, head design, revs, etc.
Fuel air ignition is not a simple instant bang, so ideally you want it to start before TDC and be discharging maximum energy at or fractions after tdc (may be wrong on this exact point)
Higher ron fuels burn in a more controlled fashion and are less volatile at the top of the compression stroke hence the spark can
be advanced to provide more efficient and powerful cycle.
As I have said above (and had questioned) higher ron petrol does not necessarily provide a bigger bang, just a more controlled and less volatile one.
Run too much advance and you get the scenario you described which is very bad. You'll also get that happening in some cases as lower ron fuel which is less stable can pre ignite before the spark under high compression and exposure to heat - albeit in pretty extreme circumstances.
It has been commented on here that STI7s UK22b's etc will det like mad on 95 Ron fuel. Probably due to insufficiuent ignition advance control/knock protection. But then Scoobs never had the highest of tech engine management.
D
13 January 2003, 04:10 PM
#36
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Claude -
probably because the ECU's are not the best out there and the maps could be better.
Or more likely because the ignition advance parameters are two narrow. Earlier Scoobs did not run knock sensing and ignition control on a cylinder by cylinder basis, if I recall correctly. It is a pretty basic set up.
[Edited by Diablo - 1/13/2003 4:14:15 PM]
probably because the ECU's are not the best out there and the maps could be better.
Or more likely because the ignition advance parameters are two narrow. Earlier Scoobs did not run knock sensing and ignition control on a cylinder by cylinder basis, if I recall correctly. It is a pretty basic set up.
[Edited by Diablo - 1/13/2003 4:14:15 PM]
13 January 2003, 04:42 PM
#37
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As I have said above (and had questioned) higher ron petrol does not necessarily provide a bigger bang, just a more controlled and less volatile one.
)To get the bigger bang as you say, you'd need a higher calorific value, which would be the case of SUL vs Optimax, SUL having a higher CFV, Optimax simply changing the flame front and enabling igition advance, creating higher cylinder pressures.
13 January 2003, 04:46 PM
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Claude -
probably because the ECU's are not the best out there and the maps could be better.
Or more likely because the ignition advance parameters are two narrow. Earlier Scoobs did not run knock sensing and ignition control on a cylinder by cylinder basis, if I recall correctly. It is a pretty basic set up.
probably because the ECU's are not the best out there and the maps could be better.
Or more likely because the ignition advance parameters are two narrow. Earlier Scoobs did not run knock sensing and ignition control on a cylinder by cylinder basis, if I recall correctly. It is a pretty basic set up.
I would change the ECU on a scooby or probably any car for that matter, for reliability reasons alone!
13 January 2003, 05:37 PM
#40
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My01 wagon, unmodified runs as well on NUL (or better) than Optimax. And NUL gives no worse mpg when I tried it. Now done 11000 miles to to ill effect Dealer (Noble in Pencuik) even advised to use NUL rather than SUL or Optimax.
All a load of tosh - Oil companies suceeding in ripping off all those who believe the stories that you should use SUL in my humble opinion.....not that I can contrivute to the technical angle, but from a user point of view that's what I found.
All a load of tosh - Oil companies suceeding in ripping off all those who believe the stories that you should use SUL in my humble opinion.....not that I can contrivute to the technical angle, but from a user point of view that's what I found.
13 January 2003, 10:13 PM
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well, send your mail to Andrew Frankel, C/O letters@thetimes.co.uk - i got a reply of him today which read
IMO this porsche of his has been driven too carefully for its makers' intentions
Dear Mr Holliday,
Your e-mail to the Sunday Times has been forwarded to me for reply.
So far as I am aware, all modern cars with sophisticated engine management are capable of coping with this condition, indeed I cannot remember when I last drove a car which was designed to run on 98octane which was not also permitted to run on 95. I also have personal experience of this, in that I drive a 1995 Porsche 911 3.8RS which I have run on 95 octane for the last four years and 30,000 miles. The drop off in performance is negligible, it is used primarily on race-tracks and has, to date, yet to go wrong, let alone suffer catastrophic engine damage.
Many thanks for your enquiry.
Andrew Frankel
Your e-mail to the Sunday Times has been forwarded to me for reply.
So far as I am aware, all modern cars with sophisticated engine management are capable of coping with this condition, indeed I cannot remember when I last drove a car which was designed to run on 98octane which was not also permitted to run on 95. I also have personal experience of this, in that I drive a 1995 Porsche 911 3.8RS which I have run on 95 octane for the last four years and 30,000 miles. The drop off in performance is negligible, it is used primarily on race-tracks and has, to date, yet to go wrong, let alone suffer catastrophic engine damage.
Many thanks for your enquiry.
Andrew Frankel
13 January 2003, 10:39 PM
#43
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My '98 M3 EVO has a sticker on the dash stating "98 Octane fuel only", I may be guessing but I would have thought that the BMW ECU was reasonably "sophisticated".
I have not yet tried running on 95 RON, but I'll consult the handbook and see what it says....
Darren.
I have not yet tried running on 95 RON, but I'll consult the handbook and see what it says....
Darren.
13 January 2003, 10:44 PM
#44
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Go to the frst link to understand 100Oct.
http://www.gtr.co.uk/forum/upload/showthread.php?s=&threadid=6346&highlight=octane
Happy reading.
[Edited by Mycroft - 1/13/2003 10:47:41 PM]
[Edited by Mycroft - 1/13/2003 10:48:31 PM]
http://www.gtr.co.uk/forum/upload/showthread.php?s=&threadid=6346&highlight=octane
Happy reading.
[Edited by Mycroft - 1/13/2003 10:47:41 PM]
[Edited by Mycroft - 1/13/2003 10:48:31 PM]
01 December 2003, 06:53 PM
#45
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so says the Sunday Times.A journalist called Andrew Frankel has listed his top ten motoring urban myths.This is n.o6
Cars that demand 98 octane fuel cannot run on anything less
Nonsense.Many sports cars come with warnings that say owners must use 98 octane fuel-the purest available-but this is really to only to obtain the maximun performance from the engine.It is perfectly safe to use 97 or 95 octane fuel in these cars.The only effect will be that the performance suffers slightly.
However,no damage will be done,even if the lower quality quality fuel is used for long periods of time
feel free to bambard him with emails.I can't because on a technical basis I know nowt apart from the fact you guys would possibly have a different opinion.
no damage will be done,Andrew Frankel says so.
[Edited by dba - 1/12/2003 6:53:38 PM]
Cars that demand 98 octane fuel cannot run on anything less
Nonsense.Many sports cars come with warnings that say owners must use 98 octane fuel-the purest available-but this is really to only to obtain the maximun performance from the engine.It is perfectly safe to use 97 or 95 octane fuel in these cars.The only effect will be that the performance suffers slightly.
However,no damage will be done,even if the lower quality quality fuel is used for long periods of time
feel free to bambard him with emails.I can't because on a technical basis I know nowt apart from the fact you guys would possibly have a different opinion.
no damage will be done,Andrew Frankel says so.
[Edited by dba - 1/12/2003 6:53:38 PM]
01 December 2003, 07:50 PM
#46
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Any UK subaru that is NOT modified can run all its life on 95 RON without problems and very likely without det
[Edited by chrisp - 1/12/2003 7:51:42 PM]
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