Hi all!
The last couple of months Greece has been the only country (as I've heard, at least) in which BP and Shell distribute their new fuels: "BP Ultimate" and "Shell V-power Racing 99+".
BP Ultimate is 100 octane, and supposed to be environment friendly, plus cleans valves, valve seats, etc. Average price ~0.9 euro.
Shell VPR 99+ is, as name suggests, more than 99 octane (but less than 100!) and is also supposed to clean the engine, etc. Average price is ~1.0 euro.
I'm currently burning a load of BP Ultimate and after four days I can tell the following:
1. Funny smell when engine cold
2. Car (Renault Clio 1.4 16v) slightly more responsive
3. Apparently increased economy. No measuring yet, just that while driving the usual way, the fuel needle moves more slowly.
What surprised me is that with plain Shell V-power (98 octane unleaded) my Clio was more responsive than with BP Ultimate! But then again, maybe it was just a feeling...
Great economy with Shell V-power too.
Vagelis.
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I have an amplifier that goes up to eleven if you're interested.
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I have an amplifier that goes up to eleven if you're interested.
Lol - you just saved me the bother of typing out a lengthy post re this. Well summed up on one sentence ChrisR...
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Some guys need an amplifier...
some don't.
Vagelis.
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Clever comments apart, why wouldn't a higher octane be an advantage ? Given that the engine can take advantage, of course.
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I don't know if 100 octane could be handled by car engines. In the last war people could get hold of 100 octane (aviation spirit basically) but if used for overlong periods this would lead to valves burning out.(sidevalve engines). I wouldn't want to risk 100 octane in mine.
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Bah! 5 Star petrol was 100 octane years ago.
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Clever comments apart, why wouldn't a higher octane be an advantage ? Given that the engine can take advantage, of course.
The following is from:
www.mg-sportcars.co.uk/Motor_Oil_FA_Questions.htm
by "Martin Williamson (aka MartinW), a mechanical engineering graduate from Cape Town University, is a technical consultant and company director involved with industrial oils with an unhealthy interest in automotive matters!"
>>>"..Optimax offers the following because of a better burn capability and a higher RON number 98, compared to other super unleaded fuels of RON 97:
Better fuel consumption
Better power output (probably 5% max)
Better, cleaner emissions from the exhaust
Maintains a cleaner fuel system (pipes and injectors, as well as in the combustion chamber minimising depositing)
If you have a knock sensor that can adjust the engine management/timing, then you will see all 4 benefits. ....">>>>
--
{P} = advertising profile is ON. Backroom photos groups.msn.com/honestjohn/pictures
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Well, if I'm not wrong, higher octane fuel gives better combustion (it ignites in a more "stable" manner, if I may say), so modern engines can light the spark plug sooner and get more efficiency.
Of course it's up to the engine to take advantage of that. The clio takes 95 and 98 octane petrol, so I guess the (alleged) 100 octane of BP Ultimate doesn't offer anything more. Maybe it offers more economy by better combusting, but I'll wait till the tank empties to extract results.
Vagelis.
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Higher octane fuel will burn more easily but that statement should really be reversed.
Knock sensors do very, very little - they can retard the ignition very slightly if the fuel is of particularly poor quality and is causing a little pinking. Likewise, if higher grade fuel is used they may, over a period of time, advance the ignition slightly to benefit this. The difference will be negligible and the main benefit you'll notice is a better pickup during initial acceleration on an engine that hasn't been serviced recently. You may also notice a very minimal decrease in fuel consumption in the order of 2-3 mpg. Your average human being will have trouble noticing any of these changes. When a car is released to a market, it is released with the ECU programmed to accept a certain octane fuel. In the UK that is 95 octane on the whole with one or two being specifically tuned for 98. The ECU does not work far outside this at all.
Getting a nice noticeable increase in power (e.g. 5%) takes more than changing the fuel...
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I think you are underestimating the impact of fuel-quality on modern, high compression or turbo engines.
When the combustion chamber has reached its normal temperature, the high compression ratio of modern engines (10:1 and more) can cause the mixture to ignite gruffly when using low-quality (low-octane) fuel and make the engine knock.
Higher-octane (quality) fuels ignite in a more "smooth" manner, and thus enable the ECU to advance ignition a bit further.
I never implied that higher octane means more horses! They just enable modern engines to produce the highest work they potentially can.
HOWEVER, how would you comment a _25hp_ increase on a leon 20vt, when using BP Ultimate? (measured on a single-barrel dynojet)...
Vagelis.
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Well I'd love to be able to buy 100 octane fuel so I could retune my Rover 3500S with the 10.5:1 CR engine back to what it should be. Any chance of BP selling it here? I'd use Optimax if I had a petrol station that sold it near enough. One of the few downsides of living in the sticks.
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You can buy 100-102 octane fuel in the UK, as long as you are willing to fork out £4/litre!
Usually available at motor racing circuits and some bulk suppliers bulk as in 50 gallon drums).
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BP are putting up signs for BP Ultimate now and it's already in the pumps. (a friend tells me)
Anyone in Thetford will know this if they go along to their local filling station.
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Cor, the things you petrol boys will do to get a bit more economy and power.
There's another answer. Begins with "D"
:o)
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I don't want better economy, I just want more power!
By the way does the word beginning with 'D' end with ual-turbo?
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Hi all, thanks for your contributions!
Well, having tested BP ultimate, I conclude that for my car the results are not so great that would justify the price difference. I don't mean it's worse than normal unleaded, but not that much better either. My conclusions:
1. Funny smell - a bit like leaded fuel :-o
2. Engine running smoother, slightly more responsive
3. Somewhat increased economy. With foot to the floor, it lasted somewhat longer.
The other (alleged) advantage of this fuel is that it doesn't contain those additives that produce fumes very harmful to the environment, or if it does contain some, it is in very small quantities.
I guess I'll be filling up with BP ultimate every now and then, just to keep my environment-conscious self happy :-)
Vagelis.
PS: It would be very interesting to see the effects of this petrol on larger and more powerful engines, so looking forward to receiving feedback from fellow BRoomers!
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The other (alleged) advantage of this fuel is that it doesn't contain those additives that produce fumes very harmful to the environment, or if it does contain some, it is in very small quantities.
Wrong. You put hydrocarbons in and burn them (in the case of a petrol-driven car engine) rather inefficiently, you get all kinds of nasties out and you then have to deal with them. This kind of naive thinking is the reason why we have unleaded, catalytic converters, etc. in the first place, rather than a widely distributed alternative fuel like biodiesel (which is no saint either, I know) or hydrogen (also with its drawbacks). There is no such thing as a clean hydrocarbon-based fuel, except in the minds of the oil company executives and their shareholders.
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"You put hydrocarbons in and burn them (in the case of a petrol-driven car engine) rather inefficiently, you get all kinds of nasties out and you then have to deal with them."
Chemistry says that when you burn hydrocarbons you get CO2 and water. The additives are those that produce extra-nasty stuff. Leaded fuel, for an example, contained lead! Unleaded doesn't! Also, diesel-burners may be more efficient, but not that much more, otherwise we'd be all driving them now. They're more economical, but power-wise drag behind.
"There is no such thing as a clean hydrocarbon-based fuel, except in the minds of the oil company executives and their shareholders."
Agree with you completely. Never said that this BP ultimate is really clean.
Vagelis.
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Not accusing you of saying it was really clean. And you did actually quote me when I said 'burn them [...] rather inefficiently' so there's no need to quote the end result of a 'perfect' hydrocarbon burn--I know anyway. Imperfect combustion has very unpleasant consequences down the line, which is why we have catalysts. Sadly there are things in the catalytic converter that you wouldn't sprinkle on your chips, but there they are coming out of your tailpipe, bit by bit. I never mentioned diesel engines either: you were talking about petrol engines and so was I. But since you do mention them, I suggest you find out more about them and their relative performance--and I mean that quite sincerely: if you haven't tried a modern diesel then you should, definitely.
My real point was that this marketing stuff makes us do things that are not a good plan in the long run just so that we can have an easy life and not feel too guilty in the short run. Burning less is the only sure-fire way, inconvenient though it may be.
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"Sadly there are things in the catalytic converter that you wouldn't sprinkle on your chips, but there they are coming out of your tailpipe, bit by bit."
What are they? (Genuine question, not smart-&&&& comment)
V
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Mostly metals such as platinum and rhodium I believe--I guess that's why they are expensive. As the catalyst degrades these end up in the air and the soil--in quite high levels by the side of busy roads according to the govt. environmental agency I used to work for. The long-term effects of these metals is not known as there have been no long-term tests--until now, on you and me.
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Having worked on the development of new engines and engine management systems I find that a lot of people are a bit gullible when it comes to claims about higher octane numbers etc.
Octane number (which is measured in a variety of ways - RON, MON etc.) tells you about a fuel's resistance to knock.
Knock happens when the unburned portion of fuel mixture in the cylinder (the 'end gas') is exposed to the pressure and thermal radiation of the burning flame front, as it advances down from the spark plug. Ideally you want all of the mixture to burn smoothly - but sometimes the end gas suddenly explodes and causes intense pressure waves in the cylinder (and the cylinder resonates like a bell - the 'knock' sound).
The end gas suddenly explodes because petrol has some unstable hydrocarbon compounds in it.
There are two ways you can deal with this:
1. Refine out the unstable compounds to get pure 'petrol' - isooctane - which has a RON of 100 (this is expensive).
2. Put in an additive to 'damp' the unstable compounds from exploding - this is the route normally chosen.
Tetraethyl lead (TEL) was normally used, but now they use methyl tertiary butyl ether (MTBE) in 'unleaded'. Adding more MTBE raises the octane rating. Doing this does not necessarily give you more power (there is no more energy in a litre of high octane petrol).
Knock is pretty complicated and depends on a lot of factors, for example the amount of swirl in a combustion chamber, the chamber shape and flame path (e.g. 'twin spark' engines) and the inlet air tempaerature (knock is less likely if the mixture starts out cooler).
Basically if the engine is designed to run 98 RON and you put in 100RON, then all things being equal you are unlikely to notice any difference. You can advance the spark timing a bit (because the end gas can take more pressure before knocking sets in) - this increases the mean effective pressure in the cylinder, but the effect is quite marginal.
If you go for a full engine rebuild then you could raise the compression ratio, which would lift the overall thermal efficiency - but that's quite another matter of course.
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"Adding more MTBE raises the octane rating. Doing this does not necessarily give you more power (there is no more energy in a litre of high octane petrol)."
Agree with you Aprilia, but IIRC, petrol-engines efficiency is somewhere between 20% and 30%. Yes, there is no more energy in a litre of petrol, but if you are more efficient you can extract more from it!
Vagelis.
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No, you're not quite right there. The combustion efficiency of a petrol engine is around 95% - Diesel is even higher (about 98% - because they are inherently 'lean burn').
Of course a lot of the energy goes into the cooling system and out of the exhaust pipe - so you're left with only around a third of this to turn the wheels.
So you can see that raising combustion efficiency from, say, 95% to 97% isn't going to make much difference at the wheels.
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Couldn't then a "better" fuel combust in a "smoother" manner and reduce (to a degree) some of this wastage?
Smoother combustion -->
Better energy transfer to piston -->
More Work to piston -->
Piston acquires more kinetic energy -->
[...] -->
More energy to wheels.
That is, extract more energy from the combustion process rather than the fuel.
You are right with the combustion efficiencies.
Vagelis.
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What you call 'smoothness' is, I think, uniformity of burn. This is related to the homogeneity of the air-fuel mixture, which is in turn a factor of other parameters such as atomisation, degree of swirl in the inlet manifold and combustion chamber etc. etc. (you get the picture). I'm not sure how a fuel could be made to improve this - other by being a gas (e.g. LPG - which does burn smoother on acount of its excellent mixing properties).
Engine design is incredibly complex (which is why any one person claiming to have 'designed' an engine these days is an idiot - you need a team of about 250+ people!!) - so long as the fuel meets the minimum requirements it is not possible for it to improve performance by very much. Most performance aspects are set in concrete at the design stage.
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I really hope this isn't a windup as well. 5-star is just the thing I need to get my 3500S running on the fuel it was built to use. I'll still have to add a lead replacement dose but at least I can put the timing back to where it should be.
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You don't need a lead replacement additive. Check out the P6 Rover owners club forum for a discussion on this. The only reason Rover V8s needed LRP is for the higher octane, they are perfectly happy without lead for the lubrication, always have been.
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