On a reasonably modern multipoint injection LPG system, the gas injectors are driven from the signal usually sent to the petrol injectors, which is intercepted by the LPG ECU which applies some modification to inj timing to get the correct readings from the Lambda sensors.

Because the Petrol ECU thinks it is still injecting petrol it will still give an MPG reading. However the Petrol ECU does not know what the downstream LPG ECU is doing, nor does it know what the LPG gas line pressure is, so it has no way of knowing how much LPG is being injected therefore the mpg reading will be false.

HTH

Cheers

Jerry
 
jerrytlr said:
On a reasonably modern multipoint injection LPG system, the gas injectors are driven from the signal usually sent to the petrol injectors, which is intercepted by the LPG ECU which applies some modification to inj timing to get the correct readings from the Lambda sensors.

Because the Petrol ECU thinks it is still injecting petrol it will still give an MPG reading. However the Petrol ECU does not know what the downstream LPG ECU is doing, nor does it know what the LPG gas line pressure is, so it has no way of knowing how much LPG is being injected therefore the mpg reading will be false.

HTH

Cheers

Jerry
Click to expand...


It's not psychic then? :D:D:D
 
Agree Jerry.

However, it will change with your driving, and can be an indication off driving economically, or like a hooligan. But thats it.
 
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wammers said:
It's not psychic then? :D:D:D
Click to expand...

Well, I do wonder - the mpg reading on my Subaru is always within 1 mpg of the actual mpg (brim to brim measurement) when running on LPG.... spooky ;-)

I'm guessing it's similar psychic behaviour to that which enables the trip computer to know about aftermarket performance chips and tell the lucky owner that they are now doing 5 mpg more than before it was fitted ;-)

Cheers

Jerry
 
I am doing a 360 mile trip, soon, so i will brim the gas tank and zero the mpg and see how it compares to the actual, see how far out it is.
 
(4.6 motronics 1999 60,000 on clock correct air in tyres 3 persons, no wind or rain, saturday so very few lorries, set on cruse control as often as possiable)I went down near london 256 miles total round trip from Nottingham M40 Oxford then M1 cost was £60 calnt work it out fuel was £1.35 a litre. :D
 
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dougdotcom said:
(4.6 motronics 1999 60,000 on clock correct air in tyres 3 persons, no wind or rain, saturday so very few lorries, set on cruse control as often as possiable)I went down near london 256 miles total round trip from Nottingham M40 Oxford then M1 cost was £60 calnt work it out fuel was £1.35 a litre. :D
Click to expand...

By my count that is 26.1 MPG. You sure the wind wasn't at your back? ;)
 
borristherat said:
:hysterically_laughi:hysterically_laughi:hysterically_laughi:hysterically_laughi nice
Click to expand...

Forgot to mention tis also the speed where I no longer need to open the window to stick me arm out :eek::eek:

Lots of folk think that flapping door tops are a fault but what they don't realise is it's the result of LR's early experiments in variable aerodynamic stabilisation ;)
 
jerrytlr said:
Well, I do wonder - the mpg reading on my Subaru is always within 1 mpg of the actual mpg (brim to brim measurement) when running on LPG.... spooky ;-)

I'm guessing it's similar psychic behaviour to that which enables the trip computer to know about aftermarket performance chips and tell the lucky owner that they are now doing 5 mpg more than before it was fitted ;-)

Cheers

Jerry
Click to expand...


I rather think that is something written into the after market chips. You can't get more power without injecting more fuel. So getting another 40 BHP and using less fuel to do it, is an impossibility. You may get a slight improvement at constant cruise, but using your new found acceleration never.
 
I have got 32 driving super careful and upto 65 on the motorway over a 70 mile run.
typically I get 25 cross country and 20 in town.
 
26 to the gallon-f******* brilliant, someone has a really light foot, just proves it can be done. Mind you today fully loaded with passengers etc, got 22.5 on the road to hell (that's the A19, ask Chris Rea).
 
hi, just done 235 miles on lpg with 72 litres at cost of 69p per litre , in my 2000 4.6 v8 with 90k on clock and multipoint lpg sytem which is 3 yrs old and serviced regularly .. anyone want to work that out i.e. mpg cheers mozz
 
wammers said:
I rather think that is something written into the after market chips. You can't get more power without injecting more fuel. So getting another 40 BHP and using less fuel to do it, is an impossibility. You may get a slight improvement at constant cruise, but using your new found acceleration never.
Click to expand...

I hear what you say, Wammers, but peak HP gains aren't the full story with chipped motors. I had my E36 M3 'live' remapped in a full day's session on a dyno. The 'peak' HP gain was only 9 BHP, but it totally transformed the way the car drove. The gains in the midrange were pretty spectacular for a n/a motor - picked up another 38 BHP between 3-5000 rpm (yes, that IS midrange for an M3!) and made the car alot more 'willing' and driveable. As a result, I had to give it less throttle in the midrange to see the same (or even slightly better) results, and as such I picked up another 3 mpg on my previous average.

The same tends to ring true of most 'chipped' motors - you may use the extra power (and therefore, as you correctly stated, the extra fuel to generate that power)... But you aren't going to use it ALL the time, and with normal day-to-day driving you will almost certainly pick up a few mpgs in your overall average.
 
Clarky130 said:
I hear what you say, Wammers, but peak HP gains aren't the full story with chipped motors. I had my E36 M3 'live' remapped in a full day's session on a dyno. The 'peak' HP gain was only 9 BHP, but it totally transformed the way the car drove. The gains in the midrange were pretty spectacular for a n/a motor - picked up another 38 BHP between 3-5000 rpm (yes, that IS midrange for an M3!) and made the car alot more 'willing' and driveable. As a result, I had to give it less throttle in the midrange to see the same (or even slightly better) results, and as such I picked up another 3 mpg on my previous average.

The same tends to ring true of most 'chipped' motors - you may use the extra power (and therefore, as you correctly stated, the extra fuel to generate that power)... But you aren't going to use it ALL the time, and with normal day-to-day driving you will almost certainly pick up a few mpgs in your overall average.
Click to expand...

That totally depends where you do your everyday driving. I was talking diesels, petrol engines are a totally different animal. They can actually gain power by correcting an over rich segment. Diesels have to have more fuel to produce more power. It can't be done any other way without major engine mods.
 
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