Omega Owners Forum
Omega Help Area => Omega General Help => Topic started by: mathewst on 07 February 2011, 13:40:44
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Finally got the mig back from the lpg installers shop.
Must admitt they did a great job.
So was wandering now about one thing.
Average consumption on the trip computer, do the rest of you have it (probably Tunnie could share some light since his is 2.2)?
Mine is showing consumption still although it is increased ( it probably should be when it is working on lpg)
I never tried to figure out how the trip computer works but I was surprised this works on lpg.
Oh by the way lpg is BRC sequent
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ignore the trip computer now, it will be talking 'dangle berries' :D - Its calculations are assuming your running on petrol.
Infact MPG now your on gas, is not the way to measure economy, its pence per mile :y
LPG has less 'bang per litre' compared to petrol, so you need more (hence drop in mpg) So fill it up, zero the trip, and work it out the old fashioned way.
When prices where cheaper (i was paying 57p litre on my commute days) i could get cost down to 10.3p a mile on average, where as petrol was costing me 17p per mile.
:y
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ignore the trip computer now, it will be talking 'dangle berries' :D - Its calculations are assuming your running on petrol.
Infact MPG now your on gas, is not the way to measure economy, its pence per mile :y
LPG has less 'bang per litre' compared to petrol, so you need more (hence drop in mpg) So fill it up, zero the trip, and work it out the old fashioned way.
When prices where cheaper (i was paying 57p litre on my commute days) i could get cost down to 10.3p a mile on average, where as petrol was costing me 17p per mile.
:y
Or in your case Mathew, Lipa or Kuna per Kilometer! ;D ;)
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in day-day terms it saved me about £10 per day in fuel :o
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The Consumption both Instant and average should work on LPG, assuming it been installed correctly, it will probably read arround 10% lower than on petrol.
The bit that probably will throw a wobbly is the range display, as this will still read the petrol tank.
Chris:y
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ignore the trip computer now, it will be talking 'dangle berries' :D - Its calculations are assuming your running on petrol.
Infact MPG now your on gas, is not the way to measure economy, its pence per mile :y
LPG has less 'bang per litre' compared to petrol, so you need more (hence drop in mpg) So fill it up, zero the trip, and work it out the old fashioned way.
When prices where cheaper (i was paying 57p litre on my commute days) i could get cost down to 10.3p a mile on average, where as petrol was costing me 17p per mile.
:y
Consumption Computer works fine on mine, in fact its bang on when compered to an LPG brim to brim.
But as said before the Range bit gets confused.
Chris.
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Actuallly Zirk it is reading about 10% more than on petrol.
If my maths is still good I should be saving around 6 pounds per 100 km in town and around 2.7 pounds per 100 km on open road.
Tunnie thanks for a quick reply ("no wander you got that "Over active poster" title ;D
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MPG on the MID is calculated from engine ECU & injectors, it measures the consumption used compared to distance travelled. When LPG cuts in, its the LPG ECU doing the control, petrol no longer comes into it.
The mpg you get on the MID is from when its only running on petrol, and given that it only runs for a few mins on petrol, thats the mpg you see.
Mine says 29mpg but there is no way its doing that on gas.
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Actuallly Zirk it is reading about 10% more than on petrol.
If my maths is still good I should be saving around 6 pounds per 100 km in town and around 2.7 pounds per 100 km on open road.
Tunnie thanks for a quick reply ("no wander you got that "Over active poster" title ;D
Thats bigger saving than what I would get, my old 150 mile daily commute saved me £10-11 ish.
So you saving £6 per 62 miles? Thats damn good! :) :y
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The mpg you get on the MID is from when its only running on petrol, and given that it only runs for a few mins on petrol, thats the mpg you see
Actually this value is changing constantly, for instance if I start the car it consumes petrol and this is calculated, after it reachec certain temp it automatically converts to lpg and the consumption value is still being calculated all the way and it is different from the one calculated before the lpg (higher for some 12%)
Here gas is relatively cheap so that is the reason for bigger savings I guess
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Finally got the mig back from the lpg installers shop.
Must admitt they did a great job.
So was wandering now about one thing.
Average consumption on the trip computer, do the rest of you have it (probably Tunnie could share some light since his is 2.2)?
Mine is showing consumption still although it is increased ( it probably should be when it is working on lpg)
I never tried to figure out how the trip computer works but I was surprised this works on lpg.
Oh by the way lpg is BRC sequent
actually your petrol ecu is still thinking the car is using petrol ;D because lpg ecu uses petrol ecu signals to arrange its injection timing.. although not 1 to 1, still your lpg consumption is proportional to MID reading..
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MPG on the MID is calculated from engine ECU & injectors, it measures the consumption used compared to distance travelled. When LPG cuts in, its the LPG ECU doing the control, petrol no longer comes into it.
The mpg you get on the MID is from when its only running on petrol, and given that it only runs for a few mins on petrol, thats the mpg you see. Mine says 29mpg but there is no way its doing that on gas.
Wrong.
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MPG on the MID is calculated from engine ECU & injectors, it measures the consumption used compared to distance travelled. When LPG cuts in, its the LPG ECU doing the control, petrol no longer comes into it.
The mpg you get on the MID is from when its only running on petrol, and given that it only runs for a few mins on petrol, thats the mpg you see. Mine says 29mpg but there is no way its doing that on gas.
Wrong.
Then tell me, how does the engine/petrol ECU know how much gas is being used :-?
It can't, the MID tells rubbish when running on gas. Its designed for petrol use!
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Actuallly Zirk it is reading about 10% more than on petrol.
If my maths is still good I should be saving around 6 pounds per 100 km in town and around 2.7 pounds per 100 km on open road.
Tunnie thanks for a quick reply ("no wander you got that "Over active poster" title ;D
When you say more, do you mean more comsuption, that may be right on yours, cant remember now what Opels display on the MID, per litre, seem to remember its something like liters per 100 km which is the other way round to our miles per gallon (MPG).
On mine it reads about 10% less, ie if I criuse on petrol say 33mpg, switch to gas it drops to about 29/30 mpg, ie less mpg but higher consumption.
Chris.
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MPG on the MID is calculated from engine ECU & injectors, it measures the consumption used compared to distance travelled. When LPG cuts in, its the LPG ECU doing the control, petrol no longer comes into it.
The mpg you get on the MID is from when its only running on petrol, and given that it only runs for a few mins on petrol, thats the mpg you see. Mine says 29mpg but there is no way its doing that on gas.
Wrong.
Then tell me, how does the engine/petrol ECU know how much gas is being used :-?
It can't, the MID tells rubbish when running on gas. Its designed for petrol use!
Well, all I can say Tunnie is its works fine on mine, so guessing my LPG ECU must talk to the Main ECU.
If on a long run, while on Gas if I reset the average MPG, the Trip Millage and Trip Gallons its all bang on as it should be, and Im not talking about a few miles on Petrol before it goes to Gas on start up, Im talking about a 200 plus trip on LPG.
Chris.
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MPG on the MID is calculated from engine ECU & injectors, it measures the consumption used compared to distance travelled. When LPG cuts in, its the LPG ECU doing the control, petrol no longer comes into it.
The mpg you get on the MID is from when its only running on petrol, and given that it only runs for a few mins on petrol, thats the mpg you see. Mine says 29mpg but there is no way its doing that on gas.
Wrong.
Then tell me, how does the engine/petrol ECU know how much gas is being used :-?
It can't, the MID tells rubbish when running on gas. Its designed for petrol use!
Not saying its dead accurate, but it operates while running on gas giving instant consumption and the average consumption changes as well, over a longish run. Imo its almost as accurate or inaccurate on gas as it is on petrol.
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When you say more, do you mean more comsuption, that may be right on yours, cant remember now what Opels display on the MID
Yep Zirk more consumption, it shows an increase in consumption about 10 to 12% on lpg then it normally shows on petrol
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What the MID reads when on LPG is pure luck of the draw. In theory it should show the same as on petrol, i.e. it should show how much petrol you would have been using. It has no knowledge that the car is not running on petrol.
In practice, what it displays will depend on how the LPG system is calibrated. If it's calibrated slightly rich on LPG, it'll read higher MPG, and vice versa.
I don't bother to look at it on LPG.
Kevin
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But it isnt purely taking its readings from when it has run on petrol as Tunnie stated ?
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When you say more, do you mean more comsuption, that may be right on yours, cant remember now what Opels display on the MID
Yep Zirk more consumption, it shows an increase in consumption about 10 to 12% on lpg then it normally shows on petrol
Then thats about right then, it will use about 10 - 12 % more lpg than petrol per Km, when you go long run on lpg next time do a LPG brim to brim, ie fill up before and after preferably at the lpg pump, before setting off, reset the consumption, trip Km, trip litres on the MID and do a comparrision.
As said, the only thing thats not right for me, is the Range display, on a short trip it counts down to zero when on gas, on a long trip if I reset it calculates it correctly for petrol and stays the same ie shows my how much range is left on petrol, handy to know if you low on Gas.
Chris :y :y
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But it isnt purely taking its readings from when it has run on petrol as Tunnie stated ?
Nope. It doesn't know when you're not running on petrol. It works on the basis that you're running on petrol all the time. Range indication will always be a mess because it can't reconcile the petrol it thinks you're burning against the (unchanged) level in the tank - until you get down to 30 miles or less, when it just works on consumption so counts down the miles until it reckons you're on zero.
Kevin
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All of the fuelling is still being calculated by the fuel ecu - the LPG system takes it's fuel usage from the injectors directly.
When you're running on LPG, the injectors are still opening and closing, but there's no fuel going through them. The mpg is still, therefore worked out as if it were running on petrol at the time.
The LPG ecu just takes the petrol injector signals, fiddles with them a bit and connects them to the new LPG injectors.
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so in other words, the mid talks rubbish :D
Guess it would be more accurate if LPG had same burn factor of petrol, the inaccuracy is that you need to chuck in more LPG to get the same amount of power from the burn.
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Surely one of the ECUs must need to know how much LPG is being squirted in other wise how does my MID show Im using more gas than petrol when running on lpg per mile.
Chris. :-/
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ignore the trip computer now, it will be talking 'dangle berries' :D - Its calculations are assuming your running on petrol.
Infact MPG now your on gas, is not the way to measure economy, its pence per mile :y
LPG has less 'bang per litre' compared to petrol, so you need more (hence drop in mpg) So fill it up, zero the trip, and work it out the old fashioned way.
When prices where cheaper (i was paying 57p litre on my commute days) i could get cost down to 10.3p a mile on average, where as petrol was costing me 17p per mile.
:y
It seems tunnie is the one who is talking 'dangle berries'.
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Surely one of the ECUs must need to know how much LPG is being squirted in other wise how does my MID show Im using more gas than petrol when running on lpg per mile.
Chris. :-/
The LPG ECU's are quite basic, they just 'copy' what the petrol ECU does. When you calibrate it (on an hours drive say with mine) it just learns whats being done at various speeds, it then attempts to match that as close as possible.
My MID says 29mpg average, which is about right for petrol use. But on LPG its more like 25mpg.
But as mentioned at the start, MPG is actually totally irrelevant on gas. Its not quite half the price, it takes more LPG to get the same 'bang', so you really want to look at pence per mile, that indicates the true saving & economy :y
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Let's put this to bed then... As Kevin has already tried to explain briefly...
The petrol ECU supplies all the info for the Trip Computer. When running on LPG the petrol ECU doesn't know that the injectors aren't actually opening ;) The LPG wiring loom interrupts the signal to the petrol injectors and takes it through the LPG ECU, this (if you are running on LPG) then operates the LPG injectors as per the multipliers set up when it was calibrated the system :y
So, the trip computer is just giving a petrol equivalent. As for Zirk's reading accurately... You're LPG system must be very well calibrated :y :y
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As Kevin Wood says, and Albs hinted at, the MID will display a figure, even on LPG. How accurate this figure is depends on calibration, but I'd still expect it to read about 10% optimistically.
The MID is fed an injection duration signal from the petrol ECU. The LPG ECU is just an injector emulator, and drives the LPG injectors from the durations from the Petrol ECU (with a map applied (this is the calibration))
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Thanks. Often wondered how the MID "knew". :y
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Finally got the mig back from the lpg installers shop.
Must admitt they did a great job.
So was wandering now about one thing.
Average consumption on the trip computer, do the rest of you have it (probably Tunnie could share some light since his is 2.2)?
Mine is showing consumption still although it is increased ( it probably should be when it is working on lpg)
I never tried to figure out how the trip computer works but I was surprised this works on lpg.
Oh by the way lpg is BRC sequent
actually your petrol ecu is still thinking the car is using petrol ;D because lpg ecu uses petrol ecu signals to arrange its injection timing.. although not 1 to 1, still your lpg consumption is proportional to MID reading..
ehem.. ;D
-
Finally got the mig back from the lpg installers shop.
Must admitt they did a great job.
So was wandering now about one thing.
Average consumption on the trip computer, do the rest of you have it (probably Tunnie could share some light since his is 2.2)?
Mine is showing consumption still although it is increased ( it probably should be when it is working on lpg)
I never tried to figure out how the trip computer works but I was surprised this works on lpg.
Oh by the way lpg is BRC sequent
actually your petrol ecu is still thinking the car is using petrol ;D because lpg ecu uses petrol ecu signals to arrange its injection timing.. although not 1 to 1, still your lpg consumption is proportional to MID reading..
ehem.. ;D
Yep... You had covered it but I thought I'd give a more detailed description :y :y
Anyway... No-one was listening to you ::) ::) :D :D
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Finally got the mig back from the lpg installers shop.
Must admitt they did a great job.
So was wandering now about one thing.
Average consumption on the trip computer, do the rest of you have it (probably Tunnie could share some light since his is 2.2)?
Mine is showing consumption still although it is increased ( it probably should be when it is working on lpg)
I never tried to figure out how the trip computer works but I was surprised this works on lpg.
Oh by the way lpg is BRC sequent
actually your petrol ecu is still thinking the car is using petrol ;D because lpg ecu uses petrol ecu signals to arrange its injection timing.. although not 1 to 1, still your lpg consumption is proportional to MID reading..
ehem.. ;D
Yep... You had covered it but I thought I'd give a more detailed description :y :y
Anyway... No-one was listening to you ::) ::) :D :D
as usual.. ;D no problem ;D :) :y
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Finally got the mig back from the lpg installers shop.
Must admitt they did a great job.
So was wandering now about one thing.
Average consumption on the trip computer, do the rest of you have it (probably Tunnie could share some light since his is 2.2)?
Mine is showing consumption still although it is increased ( it probably should be when it is working on lpg)
I never tried to figure out how the trip computer works but I was surprised this works on lpg.
Oh by the way lpg is BRC sequent
actually your petrol ecu is still thinking the car is using petrol ;D because lpg ecu uses petrol ecu signals to arrange its injection timing.. although not 1 to 1, still your lpg consumption is proportional to MID reading..
ehem.. ;D
Yep... You had covered it but I thought I'd give a more detailed description :y :y
Anyway... No-one was listening to you ::) ::) :D :D
as usual.. ;D no problem ;D :) :y
Pardon? :-X :-X ;D ;D
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so in other words, the mid talks rubbish :D
Guess it would be more accurate if LPG had same burn factor of petrol, the inaccuracy is that you need to chuck in more LPG to get the same amount of power from the burn.
I think Tunnie you should base your comment's on a more personal experiences of your own Omega's rather than than an global indication of Omegas in general that you may read on the Forum, most of my posts are based on experience and are based on facts that I have encountered.
Maybe I'm repeating myself in saying my MID on lpg is spot on, may be I'm just lucky, or maybe you should take your lpg installation back back to the Installer and ask them them to re calibrate it properly.
Either way my MID does not read 'dangle berries's.
Chris
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One thing partially related to this.
A colleague of mine had an old Opel Kadett before (long before).
He was running it on lpg for a long time and never had any problems but one.
Fuel pump on his car went dead usually once a year.
Any problems with fuel pumps on migs that can be similar to this one with Kadett?
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One thing partially related to this.
A colleague of mine had an old Opel Kadett before (long before).
He was running it on lpg for a long time and never had any problems but one.
Fuel pump on his car went dead usually once a year.
Any problems with fuel pumps on migs that can be similar to this one with Kadett?
There's no reason for LPG to affect the fuel pump, except if it's driven with very low fuel level in the tank, because the engine won't stop if the fuel pump sucks air.
Kevin
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Thanks for the info Kevin :y
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Maybe I'm repeating myself in saying my MID on lpg is spot on, may be I'm just lucky, or maybe you should take your lpg installation back back to the Installer and ask them them to re calibrate it properly.
Either way my MID does not read 'dangle berries's.
Chris
I still don't see how it can possibly read spot on :-/ LPG produces less bang per injection cycle on a direct comparison, volume for volume comparison... Simple fact. LPG needs more volume to produce the same mass of fuel for burning, therefore it must use more LPG than petrol to produce the same bang :y
I just can't understand how the MID is 100% accurate... Something clever must have been done and I just can't work out what :-/
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Maybe I'm repeating myself in saying my MID on lpg is spot on, may be I'm just lucky, or maybe you should take your lpg installation back back to the Installer and ask them them to re calibrate it properly.
Either way my MID does not read 'dangle berries's.
Chris
I still don't see how it can possibly read spot on :-/ LPG produces less bang per injection cycle on a direct comparison, volume for volume comparison... Simple fact. LPG needs more volume to produce the same mass of fuel for burning, therefore it must use more LPG than petrol to produce the same bang :y
I just can't understand how the MID is 100% accurate... Something clever must have been done and I just can't work out what :-/
:y :y :y
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I still don't see how it can possibly read spot on :-/ LPG produces less bang per injection cycle on a direct comparison, volume for volume comparison... Simple fact. LPG needs more volume to produce the same mass of fuel for burning, therefore it must use more LPG than petrol to produce the same bang :y
I just can't understand how the MID is 100% accurate... Something clever must have been done and I just can't work out what :-/
It's just turned out that way due to a quirk of calibration, I think.
I'm sure it can't work by design. If nothing else, LPG is being injected as a vapour so you couldn't predict liquid consumption using injector duration in the same way that the MID does for petrol. It depends on the relative temperatures and pressures of the liquid and vapour as to how much liquid is flowing.
As I said.. Luck of the draw that the reading happens to coincide with LPG consumption for this particular setup.
I think every LPG car I've checked (from a quick check of the MID) it tends to read somewhere between petrol consumption and LPG consumption on gas, which is about what you'd expect. Engine load is slightly higher for a given output because the vapour injected displaces some air (hence petrol ECU is using slightly longer durations, hence MID reads lower MPG). Then there's an additional factor that LPG has a lower calorific value, which isn't accounted for at all.
By far the biggest unknown is probably the difference between individual system calibrations, though.
Kevin
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I still don't see how it can possibly read spot on :-/ LPG produces less bang per injection cycle on a direct comparison, volume for volume comparison... Simple fact. LPG needs more volume to produce the same mass of fuel for burning, therefore it must use more LPG than petrol to produce the same bang :y
I just can't understand how the MID is 100% accurate... Something clever must have been done and I just can't work out what :-/
It's just turned out that way due to a quirk of calibration, I think.
I'm sure it can't work by design. If nothing else, LPG is being injected as a vapour so you couldn't predict liquid consumption using injector duration in the same way that the MID does for petrol. It depends on the relative temperatures and pressures of the liquid and vapour as to how much liquid is flowing.
As I said.. Luck of the draw that the reading happens to coincide with LPG consumption for this particular setup.
I think every LPG car I've checked (from a quick check of the MID) it tends to read somewhere between petrol consumption and LPG consumption on gas, which is about what you'd expect. Engine load is slightly higher for a given output because the vapour injected displaces some air (hence petrol ECU is using slightly longer durations, hence MID reads lower MPG). Then there's an additional factor that LPG has a lower calorific value, which isn't accounted for at all.
By far the biggest unknown is probably the difference between individual system calibrations, though.
Kevin
Yep... But I'd love to know how! :y
Tunnie... I think it's your way with words that got the reaction, and understandably TBH ::)
I've met you in person and know that's just the way you are and that there's nothing else to it... Has Zirk? :-? I had a similar thing with another member a while back... Was just my poorly worded statement that came across wrongly ;)
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Tunnie... I think it's your way with words that got the reaction, and understandably TBH ::)
What can I say, i say what i think ;D
Maybe instead of "mid talks 'dangle berries'" it should be "mid will behave like a government, lie" ::)
In defence, that original comment was made to the OP who knows me well, and as far as I know took it the way intended :)
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I still don't see how it can possibly read spot on :-/ LPG produces less bang per injection cycle on a direct comparison, volume for volume comparison... Simple fact. LPG needs more volume to produce the same mass of fuel for burning, therefore it must use more LPG than petrol to produce the same bang :y
I just can't understand how the MID is 100% accurate... Something clever must have been done and I just can't work out what :-/
It's just turned out that way due to a quirk of calibration, I think.
I'm sure it can't work by design. If nothing else, LPG is being injected as a vapour so you couldn't predict liquid consumption using injector duration in the same way that the MID does for petrol. It depends on the relative temperatures and pressures of the liquid and vapour as to how much liquid is flowing.
As I said.. Luck of the draw that the reading happens to coincide with LPG consumption for this particular setup.
I think every LPG car I've checked (from a quick check of the MID) it tends to read somewhere between petrol consumption and LPG consumption on gas, which is about what you'd expect. Engine load is slightly higher for a given output because the vapour injected displaces some air (hence petrol ECU is using slightly longer durations, hence MID reads lower MPG). Then there's an additional factor that LPG has a lower calorific value, which isn't accounted for at all.
By far the biggest unknown is probably the difference between individual system calibrations, though.
Kevin
imo, there is a simpler way.. for a specific calibration (after its done) calculate the miles done and used lpg and compare with mid.. you will find some ratio which wont change highly with temp..
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...snip...
imo, there is a simpler way.. for a specific calibration (after its done) calculate the miles done and used lpg and compare with mid.. you will find some ratio which wont change highly with temp..
That's what I've done... I know that I can get about 300 miles to the tank in normal, mixed driving and 350-380 on a run :y :y
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I still don't see how it can possibly read spot on :-/ LPG produces less bang per injection cycle on a direct comparison, volume for volume comparison... Simple fact. LPG needs more volume to produce the same mass of fuel for burning, therefore it must use more LPG than petrol to produce the same bang :y
I just can't understand how the MID is 100% accurate... Something clever must have been done and I just can't work out what :-/
Well having read the posts on how the MID takes its info form the petrol ECU when running on gas, I don’t know why in that case it appears to read spot on, all I know is the MID is telling me that Im doing less MPG on gas than I am on petrol, around 10% less on a run. The trip distance and trip gallons used confirm this as well.
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I still don't see how it can possibly read spot on :-/ LPG produces less bang per injection cycle on a direct comparison, volume for volume comparison... Simple fact. LPG needs more volume to produce the same mass of fuel for burning, therefore it must use more LPG than petrol to produce the same bang :y
I just can't understand how the MID is 100% accurate... Something clever must have been done and I just can't work out what :-/
Well having read the posts on how the MID takes its info form the petrol ECU when running on gas, I don’t know why in that case it appears to read spot on, all I know is the MID is telling me that Im doing less MPG on gas than I am on petrol, around 10% less on a run. The trip distance and trip gallons used confirm this as well.
What system is it? Just looking for clues TBH ::)