You've won me over. If I can pay Gordon Brown one penny less I willOriginally posted by Russ ....and consequently less tax[/B]
You've won me over. If I can pay Gordon Brown one penny less I willOriginally posted by Russ ....and consequently less tax[/B]
Russ said:f you want to learn i'd suggest wheelie school rather than wreck your own bike
Mike O said:I'm not quite sure why you seem to be getting bent out of shape about this. I know that I get significantly better mpg when I use Super Unleaded - I wouldn't use it otherwise. I'm happy for you to believe what you will - 86k miles in the last 2 years using a variety of fuels has provided me with the evidence I need.
Mike
TerryM said:Please just ride it and leave the physics to those who have some idea.
Russ said:The GS is fitted with anti-knock sensors ...
Greg Masters said:Russ was there first:
Most people would accept that if you retard the ignition, the power and efficiency would be reduced. Readvancing the timing would restore the lost power and efficiency.
The 1200GS, fitted with anti-knock sensors, will retard or advance the ignition timing such that the burning fuel will not knock or pink. If the engine is run on a fuel with a lower than optimum octance rating (however measured), it WILL produce less power and efficiency (ie mpg).
I don't know what the optimum octane rating for this engine is, but with the last petrol car that I used that had anti-knock sensors, the effect of using super-unleaded was very clear.
The R1150GS and R1100GS do not have anti-knock sensors. I can't explain why they perform differently with super-unleaded.
Greg
I didn't say that I objectively measured the effects of super-unleaded -v- 'ordinary' unleaded, but since you ask, the car (a 1990 Vauxhall Cavalier GSi) improved it's fuel consumption from 32.1mpg to 35.0mpg when measured over 1,000+ miles.TerryM said:Greg,
What precisely was the effect of using super unleaded in the car , and how did you objectively measure it?
Did you find the motor more responsive when wound tight, which would perhaps be expected and may be measureable by stopwatch?
Or on a long straight where you could max it out did you find that the attained revs in top gear were measureably higher with the higher octane fuel? That would also be understandable.
But then what was the objective effect of higher octane on fuel consumtion, and how was the level playing field established?
I'm not sure whose definition that would be, but engine bench tests when I went to college showed that you can get 'knock' at virtually any throttle setting if the fuel quality and timing were inappropriate!TerryM said:As the knock sensors (engine management) only effect advance when knocking commences, and that, by definition, only happens under full throttle...
The question contains an untrue premise. With most modern ignition maps, the timing will change even if there is no other change than the throttle position (ie the engine load). As you roll off the throttle, the ignition is likely to advance towards the MBT (minimum best timing) - the lowest value of ignition advance that produces maximum power.TerryM said:what increase in efficiency due to the non-existent change in ignition advance at less than full throttle do you expect will contribute to the lower fuel consumption experienced by others and perhaps by you also?
No.TerryM said:Was the thing so much quicker and responsive to throttle that the enhanced fuel consumption was due to the driver/rider rolling it off in fear at the huge power increase?
I'm pleased for you, but I'm not sure how this adds to the debate about ordinary -v- super unleaded.TerryM said:My personal experience of tweaking a air cooled Porsche engine management system for the road by remapping and a more open inlet/exhaust arrangement was a estimated 30bhp at the top end giving about 10mph increase flat out and a noticeably more responsive mid range above 4300rpm where the cam on the Carrera kicks in. It made no significant difference to fuel consumption at all and I used the usual unleaded 95RON, it ran 10.3 litres per 100kms before and after.
Greg Masters said:I didn't say that I objectively measured the effects of super-unleaded -v- 'ordinary' unleaded, but since you ask, the car (a 1990 Vauxhall Cavalier GSi) improved it's fuel consumption from 32.1mpg to 35.0mpg when measured over 1,000+ miles.
Swapping to super-unleaded, empirical evidence was that the car was more responsive.
I'm not sure whose definition that would be, but engine bench tests when I went to college showed that you can get 'knock' at virtually any throttle setting if the fuel quality and timing were inappropriate!
Quite so, but who would deliberately set up the engine management to yield that result? So knock is for all practical purposes apparent under full load(throttle)as distinct from max revs or power.
TM
The question contains an untrue premise. With most modern ignition maps, the timing will change even if there is no other change than the throttle position (ie the engine load). As you roll off the throttle, the ignition is likely to advance towards the MBT (minimum best timing) - the lowest value of ignition advance that produces maximum power.
I think not,for the answer ignores the fact that the limit for advance shift to MBT is prescribed in the mapping, and cannot deviate outside that limit. That, at least, is what I thought a reader would deduce. Hence the premise is reasonable.
TM
No.
I'm pleased for you, but I'm not sure how this adds to the debate about ordinary -v- super unleaded.
I had thought that it would be evident that with enhanced breathing in a similarly configured air cooled motor of like cylinder capacity and specific output, using a mildly tweaked map for advance and fueling, the minimised timing and effectively higher compression due to better breathing had been easily accommodated by the same 95RON unleaded fuel. And that in a two valve motor which might be expected to be less tolerant than a more modern four valve design, such as the 12GS.
The test route was 200kms round trip daily(Cologne-Dortmund-Cologne) with about 150kms on autobahn cruising regularly in the 120mph+ range and up to 160mph for short periods. That was my routine for 31/2 years.
So unless the CR was increased and the map adjusted if necessary, how would 98RON or super whatever improve matters? All the data I have seen for what amount to race fuels suggest a very modest(2/3%-ish)increase in top end power only. Even in quite highly tuned Jap fours said to be running CRs in the 13:1 range at 12/13k rpm. And it is apparent that such small increments can creep into inertia dyno tests due to operator variables and other factors far removed from the motor output. So how it would play out in our garden variety toys at under 8k rpm seems moot.
I would like to think that significant performance enhancements and 10% better consumption could be gained out of the pump/super lube. But so far the back to back testing is elusive.
When someone comes along with the free fuel/lube and is willing to pay for any damage to my toys in testing their product claims I may be tempted. For the moment I multiply all such claims by a credulity constant of 0.1.
TM
I am also at a loss to know quite what to do with the small power increase and the pence saved if the super whatever works! But I have a funny feeling that the manufacturer/vendor/G.Brown Esq. will resolve the latter for me
Greg
Dolphin said:Believe what you will, but the FACT is I do get more kilometers
I'm not quite sure why you seem to be getting bent out of shape about this. I know that I get significantly better mpg when I use Super Unleaded - I wouldn't use it otherwise. I'm happy for you to believe what you will - 86k miles in the last 2 years using a variety of fuels has provided me with the evidence I need.
Mike
Holy 15yr-old thread resurrection!!!!!
How do you think the petroleum company’s arrive at the price of the difference between unleaded and super unleaded,
You get slightly more mpg with super and pay more per litre which equals cost per mile, it. Works out exactly the same cost per mile with either and that’s why they do it , if it cost less using super then why make normal and if unleaded gave better value and no performance gains then why use it.