Omega Owners Forum
Chat Area => General Car Chat => Topic started by: Diamond Black Geezer on 27 September 2016, 14:40:10
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Has anyone ever compared live data of their motor on supermarket fuel, then given a week or two on 'super fuel', and compared the results? Quick question from me, this time. :y :D
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Has anyone ever compared live data of their motor on supermarket fuel, then given a week or two on 'super fuel', and compared the results? Quick question from me, this time. :y :D
Er no.
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If the car is working properly, they will still be 0% (DBW) or 127 (non DBW).
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Ahh, Perhaps I've misunderstood the internal workings of the engine, then. The knock sensors are supposed to detect a higher/lower octane/superfuel, and advance/retard the ignition accordingly, and I thought this affected the trims? Read on another forum this was the case (different car/engine) ???
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Knock sensors affect the ignition timing, lambda sensors affect the fuel trims. They are two independent systems.
With super unleaded, all you are changing is a few trace additives in the fuel to control its' knock characteristics. The mass of fuel required for the correct mixture will be the same, so the fuel trims will remain the same.
Knock control is more a safety mechanism to save the engine if it's fed with dire quality fuel. The mapped ignition timing isn't extreme enough for any "learning" to take effect in normal circumstances. I've never seen an Omega data log with any knock retard active unless the knock sensor has been misbehaving, so I wouldn't expect that to make any difference either.
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Many thanks, full, and clear description :y Sorry, I know I sometimes bucket questions on here, but as I've said before, big thirst for knowledge, don't learn if I don't ask. Thanks again all :)
So are you suggesting that the knock control can be 'taken down a peg' for poor fuel, but not 'up one' to take advantage of higher quality/octane? If so, I assume an engine remap would be able to do this, though?
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I think the knock sensors only retard the ignition not advance it so there`s no point in putting expensive fuel in as it probably won`t make any difference, it would only benefit if the knock sensors were retarding the ignition on 95 ron, then you would reap the benefits of 97 ron fuel.
A remap would help with this but benefits on the Omega won`t be great, maybe 10% at best.
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I think the knock sensors only retard the ignition not advance it so there`s no point in putting expensive fuel in as it probably won`t make any difference, it would only benefit if the knock sensors were retarding the ignition on 95 ron, then you would reap the benefits of 97 ron fuel.
A remap would help with this but benefits on the Omega won`t be great, maybe 10% at best.
Yup
Used to sort out pre ignition caused by low octane / dodgy foreign fuel ;)
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Another thing to consider: just how beneficial is the small increase in octane rating? Exactly how big is Ron anyway ;D
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Oddf they didn't factor in at the design phase that a higher octane fuel would come into existence. I appreciate at the time of design, (late 80s) they were just changing over from 4-star, but a shame.
So perhaps that's my question then - is there any scientific way of knowing that the engine does, or does not take any advantage of a higher octane fuel?
I stick in the Tesco Ultimatum for its 'detergent' properties, and frankly minimal difference in price, certainly cheaper here at 112.9p than much standard unleaded I've seen elsewhere in the country/motorways. Not wanting to turn this into a standard vs. superunleaded thread, just seeking a definitive answer as to the V6s being able to make use of, or not, the higher octane fuels.
And the next question after that - who does remaps? ;)
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The basic requirement of an engine for fuel of a certain octane rating comes from the compression ratio or, for forced induction, a combination of the compression ratio and boost pressure.
If knock occurs, retarding the ignition timing and/or reducing the boost pressure allows the engine to run without damage but sacrificing power and economy.
On older engines, this was more of an issue, but a reasonably modern design of combustion chamber doesn't need particularly aggressive ignition advance to produce its' best power output so, for sane levels of compression such as are used in the Omega, there is plenty of margin before knock starts even on standard 95 RON unleaded.
You can't change the compression ratio, so you need a knock retard strategy to cope with very poor quality fuel, the likes of which probably doesn't get sold in the UK.
Forced induction changes things and some turbo/supercharged cars probably do reduce boost on 95 RON fuel.
If you wire up the engine with instrumentation as is done during development then yes, you can get a picture of what's happening in the combustion chamber by recording when the peak pressure occurs during combustion and checking for signs of knock with more sophisticated equipment than a standard knock sensor.
Without increasing the compression ratio, I doubt a V6 would respond to higher octane fuel - even if you remapped it, because an engine with a pent roof chamber and 10-ish :1 compression probably still has a good margin against knock when the ignition has been advanced to the point where you get no improvement in power.
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Has anyone ever compared live data of their motor on supermarket fuel, then given a week or two on 'super fuel', and compared the results? Quick question from me, this time. :y :D
not that but on my old 2.5V6 i did the same stretch of motorway every day on cruise and compared the fuel consumption by resetting the trip computer. over a series of days, when the traffic was light enough that i could safely stick on cruise between a couple of junctions, i got about 10% more mpg on super. i'd expect the 2.6 improvement to be less as the compression is lower.
that's my experience anyway
(http://www.777icons.com/libs/smile/fear-icon.gif)
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I would also say similar migmog, thank you. However, Ive not been able to scientifically do it as well as yourself, I've had to basically say 'well, my mpg isn't worse' which isnt much help! :D
From week 1 of driving Pissy, where old stale fuel and supermarket whatever gave me a week's average of about 18mpg, now she's doing 21.8 on superunleaded, with 2 years of miles on her, plus various enginework (all as-factory, we're talking thermostat, oil change etc..) Before the service a few weeks ago she was strugglign to get above 20mpg in town traffic. Very much apples and oranges, of course. But as I say, it's not making the engine worse. :y
Kevin, thank you for the detailed response, that's a bit more knowledge about engine design added to the grey matter. :y
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Whereabouts is the knock sensor on the the V6? :y
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Has anyone ever compared live data of their motor on supermarket fuel, then given a week or two on 'super fuel', and compared the results? Quick question from me, this time. :y :D
not that but on my old 2.5V6 i did the same stretch of motorway every day on cruise and compared the fuel consumption by resetting the trip computer. over a series of days, when the traffic was light enough that i could safely stick on cruise between a couple of junctions, i got about 10% more mpg on super. i'd expect the 2.6 improvement to be less as the compression is lower.
that's my experience anyway
(http://www.777icons.com/libs/smile/fear-icon.gif)
Fuel consumption is another issue. We're talking about differences in the live data.
It's possible that different fuels have different calorific values, meaning the energy density changes and so does the fuel consumption for a given work done. The most likely mechanism for this to change from one brand or type of fuel to another is by the level of bio ethanol in the fuel.
You need half as much ethanol again in terns of volume to get the same energy as in petrol, so added ethanol is effectively "watering-down" your petrol. :o
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Which has been raised as an issue (as you're no doubt aware, of course) with regard to Tesco Ultimatum. I have found it can contain as much as 5% ethanol, as little as 0%. It's mixed in the tanker/tank, not at the refinery. BP Vanden Plas+, or whatever it's called apparently does not use ethanol, instead adding detergents as well as a 'lubricant' to help the pistons slide up and down easier. there is argument that Tesco's Superfuel with ethanol is in itself a cleaning agent. But as you say, strangely, for a 'superfuel' it may in fact be 'watered down' :)
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Whereabouts is the knock sensor on the the V6? :y
One either side, about a third of the way back from front and halfway between head and sump. Bank 1 is down from cable tray to ecu loom and Bank 2 is just behind the alternator iirc :y
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:y Good to know :)
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Whereabouts is the knock sensor on the the V6? :y
One either side, about a third of the way back from front and halfway between head and sump. Bank 2is down from cable tray to ecu loom and Bank 1is just behind the alternator iirc :y
Corrected due to Left/Right confuddlement :-[
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Whereabouts is the knock sensor on the the V6? :y
One either side, about a third of the way back from front and halfway between head and sump. Bank 2is down from cable tray to ecu loom and Bank 1is just behind the alternator iirc :y
Corrected due to Left/Right confuddlement :-[
Thanks Al. :y
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tesco say the max ethanol in their fuels is 4.8% (law allows 5%). https://www.tescopfs.com/our-stations/faqs
their independent report (millbrook) shows up to 3.95% better fuel consumption with their super unleaded over their normal fuel.
back to the original question, doesn't that mean that using normal unleaded will require up to 4% more mass of fuel to be fed into the engine? perhaps not if the fuel mass is the same its just power output that is down but if yes then wouldn't the trim figures be different on superunleaded?
anyway doesn't ignition timing data show up on a cheap scanner? i'd expect it to be advanced under super unleaded compared to normal (if not then there would be no increased mpg).
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That raises an interesting question, yes. :)
Thoughts, gentlemen? :)
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tesco say the max ethanol in their fuels is 4.8% (law allows 5%). https://www.tescopfs.com/our-stations/faqs
their independent report (millbrook) shows up to 3.95% better fuel consumption with their super unleaded over their normal fuel.
back to the original question, doesn't that mean that using normal unleaded will require up to 4% more mass of fuel to be fed into the engine? perhaps not if the fuel mass is the same its just power output that is down but if yes then wouldn't the trim figures be different on superunleaded?
anyway doesn't ignition timing data show up on a cheap scanner? i'd expect it to be advanced under super unleaded compared to normal (if not then there would be no increased mpg).
I`m not sure the Omega ECU has the capability to advance the ignition depending on fuel.
I remember reading an article years ago when the V10 M5 first came out and this was when the 98 and 99 ron fuels were coming more readily available.
EVO magazine did some dyno testing using five cars but only the new M5 and Golf GTi could take advantage of the higher ron rating.
I`m pretty sure the Omega falls into the category that can`t take advantage of it, only way to be sure is to get it on the dyno.
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Thanks :y SO if we play the odds and say the Omega is just too old to make full/any advantage of newer octane fuels ...
I know it's been both said yes, and no, but I still would like to know what a remap could / would do? Surely it would make a difference? I fully appreciate what's been said in that because of the combustion chamber design there wouldnt be knock and 'within margin', but nevertheless surely moving that said margin along a bit, to the new optimum point (using the different fuel) would help? In essence do on a rolling road/etc what a newer engine with better knock sensors does by design automatically.
I mean a remap was always on the cards anyway, irrespective of whether superfuels even existed; but the old 'chip' company which was recommended doesn't seem to be around any more, and I know that there are good and bad remaps out there, and it's best to go recommended.
Suppose I'm looking at a little more into the science of 'electronic' engine fettling, really. :)
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I`m not sure the Omega ECU has the capability to advance the ignition depending on fuel.
I remember reading an article years ago when the V10 M5 first came out and this was when the 98 and 99 ron fuels were coming more readily available.
EVO magazine did some dyno testing using five cars but only the new M5 and Golf GTi could take advantage of the higher ron rating.
I`m pretty sure the Omega falls into the category that can`t take advantage of it, only way to be sure is to get it on the dyno.
page 216 of the manual
"Octane requirement (RON)
95
98 (2)
(2) Knock control system automatically adjusts ignition timing according to type of fuel used (octane number)."
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Forget all the waffle.
Go to garage fill up with your fuel of choice drive car report back,Then refill car with super duper 97/99 from your retailer, drive car report back.
Easier than page after page of waffle.
We all know car runs better on super fuels, also helps clean cats on 2.6/3.2 and according to tests done by all fuel companies' there are gains.
. thankyou and goodnight.
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Mr BG. Um....that's great, but that doesn't take into account the 'placebo' effect, or the human factor, that "We all know car runs better on super fuels" which does make the driver somewhat preconditioned to an opinion, and hardly impartial.
I do, however, thank you for your kind and constructive words.
PS Thanks Migmog, (I don't have a manual, by the way, so that's appreciated :y)
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Don`t forget that the knock control only retards the ignition not advances it, and at the end of the day if you want proof of what is going on put it on a dyno :y
For what it`s worth my MV6 gave no better or worse MPG regardless what fuel I used.
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Many thanks Mr Gav.. only retards it, then. And it's Dyno-only :) Fair enough.
I was hoping that a Tech 2 would be able to give date, as it can with the trims (which I've now learned it totally unconnected! :D)
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Many thanks Mr Gav.. only retards it, then. And it's Dyno-only :) Fair enough.
I was hoping that a Tech 2 would be able to give date, as it can with the trims (which I've now learned it totally unconnected! :D)
If you want concrete evidence of what is happening with each fuel then you would need to dyno it, that's the only scientific way you`re going to get results.
As you say there`s the placebo effect to consider when doing your own test so they`re not really worth while.
A remap would probably make a worth while difference (and it already sounds like you`ve made your mind up :D ) so get it done and enjoy it and forget about a couple of mpg difference, after all you don`t get a large saloon with a big V6 engine and worry about fuel consumption ;D
If you`re wanting a bit more go then the best single mod you can do is get a 3.7 ex plod diff, better acceleration through all the gears and not too much of a hit on mpg ;)
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Many thanks Mr Gav.. only retards it, then. And it's Dyno-only :) Fair enough.
I was hoping that a Tech 2 would be able to give date, as it can with the trims (which I've now learned it totally unconnected! :D)
If you want concrete evidence of what is happening with each fuel then you would need to dyno it, that's the only scientific way you`re going to get results.
As you say there`s the placebo effect to consider when doing your own test so they`re not really worth while.
A remap would probably make a worth while difference (and it already sounds like you`ve made your mind up :D ) so get it done and enjoy it and forget about a couple of mpg difference, after all you don`t get a large saloon with a big V6 engine and worry about fuel consumption ;D
If you`re wanting a bit more go then the best single mod you can do is get a 3.7 ex plod diff, better acceleration through all the gears and not too much of a hit on mpg ;)
Haha, ta again.
I suppose you could say I've made my mind up, yes, but at the same time it's a long way off, yet. I really try and do things in an order, so the bodywork is still a state, but that all waits, as with various mechanical bits like the back wishbones I want to refurb, simultaneously doing the handbrake/rear calipers, then arch and sill rust before it gets 'critical'... only then will I properly start to look at the twiddly nice bits, so fully expect the new year, at the earliest.
The 3.7 diff will give more punch round town, but as I recall raises the revs a fair bit on motorway, yes? - this is, I assume, where the extra fuel consumption comes from you warn me about? :y Thanks for the useful info
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Don`t forget that the knock control only retards the ignition not advances it
page 216 of the manual
"Octane requirement (RON)
95
98 (2)
(2) Knock control system automatically adjusts ignition timing according to type of fuel used (octane number)."
Note the (2) is next to 98 (super unleaded) not 95 (ordinary unleaded)
DBG pm me your email address I happen to have my manual in pdf format.
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Whereabouts is the knock sensor on the the V6? :y
One either side, about a third of the way back from front and halfway between head and sump. Bank 1 is down from cable tray to ecu loom and Bank 2 is just behind the alternator iirc :y
(http://homepages.nildram.co.uk/~aholter/DSCF0742.jpg)
(http://homepages.nildram.co.uk/~aholter/DSCF0743.jpg)
The knock sensors are just above the engine mounts in these pictures.
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Many thanks Mr Gav.. only retards it, then. And it's Dyno-only :) Fair enough.
I was hoping that a Tech 2 would be able to give date, as it can with the trims (which I've now learned it totally unconnected! :D)
If you want concrete evidence of what is happening with each fuel then you would need to dyno it, that's the only scientific way you`re going to get results.
As you say there`s the placebo effect to consider when doing your own test so they`re not really worth while.
A remap would probably make a worth while difference (and it already sounds like you`ve made your mind up :D ) so get it done and enjoy it and forget about a couple of mpg difference, after all you don`t get a large saloon with a big V6 engine and worry about fuel consumption ;D
If you`re wanting a bit more go then the best single mod you can do is get a 3.7 ex plod diff, better acceleration through all the gears and not too much of a hit on mpg ;)
Haha, ta again.
I suppose you could say I've made my mind up, yes, but at the same time it's a long way off, yet. I really try and do things in an order, so the bodywork is still a state, but that all waits, as with various mechanical bits like the back wishbones I want to refurb, simultaneously doing the handbrake/rear calipers, then arch and sill rust before it gets 'critical'... only then will I properly start to look at the twiddly nice bits, so fully expect the new year, at the earliest.
The 3.7 diff will give more punch round town, but as I recall raises the revs a fair bit on motorway, yes? - this is, I assume, where the extra fuel consumption comes from you warn me about? :y Thanks for the useful info
At motorway speeds the revs aren`t that much higher, around 250rpm IIRC but if you like to press on a bit then it`s worth the sacrifice :y
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The standard ratio for V6 manuals is the 3.7 and is higher geared than the standard V6 auto box which is a 3.9 so with a auto box, it will be slower off the line ;)
If you insist on keeping the slushbox, fit a 4.22 which will raise the revs at speed but improve pickup (and noise)
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Think the 2.5 is shorter than the 3.9 in the 3.0 :-\
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Certainly thinking a 'town diff' is on the cards... :)
Thanks all.
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Certainly thinking a 'town diff' is on the cards... :)
Thanks all.
Piss take / banter aside for a minute J .......
Seriously mate, a thousand questions on various subjects and I and I suspect quite a few on here are wondering what you are trying to achieve with your car ?
Performance ?
Economy ?
Drivability ?
A mixture of all three ?
Just playing around / experimenting and maybe wasting money ?
Just asking like :P
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Fair point. and, again, joking aside, genuinely serious/sombre/sober...
I'm bored! That's the primary reason. I'm basically approaching the end with my job, we're planning a move down tot he midlands, Bekki's got in at Cov uni, but unless I can sort some work down there, ad well as all those other little things like somewhere to live, that sort of scuppers it.
I'm sat at this desk all day, with frankly little in the way of proper hard work - not like plenty of here do (present company included) I like to graft, get stuff done, not vegetate in front of a computer screen all day. The nature of the job has changed drastically in the last year or so. I'm no longer/not in the career path I wanted to be on (boo hoo, that'll change, I keep optimistic)
So, re: the above comp screen, my mind runs at a million miles a minute, 20% is devoted to my job, while the other 80% thinks about mainly car-related bits. Overthinking, looking for problems that aren't there. Also knowing, with more than a little frustration, that I don't get the time in the evenings to do half of what I want... the stuff I've spent all day thinking about. Notice that I basically never post on the evenings - too busy. All my posting occurs during mon-fri 9-5pm.
Like I say, it's overthinking, really. I appreciate your question, Steve. In lieu of actual work on my car, I think the theoretical work ends up becoming 'surrogate'.