Range Rover 4.6 on LPG needs re-map

My 110, with a 4.0 and weighing 2.5 tons, only does 12mpg on LPG. What were you getting on petrol?

If that were the case, I'd expect it to have gone into limp mode, usually with the engine check light on the dash illuminated as well.

Dan, as I understand it, the Thor engine IS using the Gems (SAGEM) management system, the earlier versions of 4.0/4.6 using MEMS and 3.9 using Lucas 14CUX. Contact them direct and confirm.

Allegedly. You don't get something for nothing, in my book. The main reason for the re-map is to preserve engine life by correcting the over-lean light throttle cruise condition. Badger.

On or around Fri, 10 Jun 2005 23:54:52 +0000 (UTC), "Badger" enlightened us thusly:

Mine used to get about 11 on a good day with a knackerd 3.5. However, the disco, with a decent 3.5 (and a manual box, FWIW) gets a bit more'n 13.

Are you on open or closed loop? I'm still thinking about closing the loop on mine - at best I've got 13mpg but its normally about 11.5. 3.5 carbed pre emission control rangie.

My 4.6 does just under 12mpg, but that's almost all town work (with wife driving). Much better on a run nearly 17mpg on LPG. I'm using OMVL sequential.

On or around Sat, 11 Jun 2005 12:14:31 +0100, "Andy Warner" enlightened us thusly:

All mine have been open loop.

Danny> Hello folks: I have a '99 4.6 HSE which is LPG converted, Danny> but I only get 11.2 MPG on LPG (OK - I know it's a really Danny> big heavy car).

What do you get on petrol? Are you getting a big power difference on petrol/lpg? And what kind of LPG system do you have fitted?

Danny> RPi engineering do it for the earlier GEMS EMS but not for Danny> the THOR. Danny> Apparently they get 15% better power and economy too.

Only on petrol, though they don't go out of their way to point that out!

I think you need to look to the setup of the gas system first....

OOps, wrong way round! Thor is Motronic system, not SAGEM. Sorry. Badger.

Not strictly true Andy, if you are running a modern SGI gas system, the pulse that initiates gas injection is taken directly from the petrol injector harness, ie it comes from the petrol ECU. So, if the fuelling output signal of the ecu is altered, this results in an alteration to the injector pulse-width, this is picked up by the SGI control unit which in turn fires the gas injector for a correspondingly longer pulse also. Any alteration to the petrol ecu is seen at the gas ecu when running on gas. If you were referring to older standalone gas systems, then you are perfectly correct, BUT those older systems would never get installed on a Thor anyway, due to the complexities of the management system.

Agreed.

Hi Badger,

Any point retrofitting closed loop control to a 101 3.5 V8 ? Thanks. Steve

There are good arguments both for and against. In theory it might improve the fuel consumption by 2 or 3 %, so in that respect no, it isn't really worth the time and effort I'd say. However, an added benefit is the closed loop maintaining lambda and preventing the engine from running lean - with potentially disasterous consequences for the pistons. In that respect, yes, I'd say it was worth doing. If you stick a CO meter up it's bum regularly and you know the CO is ok, then I'd leave well alone if running ok. If you tend to adopt a style more akin to "reactive maintenance" (Oh shit, it's bust, best I react by fixing it) then I'd say fit it. Just remember to fit the lambda probe as high up the downpipe as possible, and to the rear to protect from direct water splashing. If a hot probe gets a sudden drenching with cold water, it tends to cease to function! FWIW, I'd fit the AEB Leonardo (OMVL Millenium) closed-loop system if it were my decision, bear in mind you'll need a throttle position sensor as well, shouldn't be too difficult to fit a std EFI one onto a bracket and rig up a drive from a carb spindle. Good luck, let me know how you get on if you decide to go for it.