To LPG or not to LPg

eightinavee said:

Are you a politician ? Seems you are unable to give a straight answer to a question,then quote the usual dribble that you trawled up off the net.Do you not realise the reputation of RPI,they sell chips.And the funny thing is they will not warrant the engine against liner issues,"the damage had already been done"

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eightinavee said:

Btw it would be alot easier to change your viscous coupling and keep the advanages of the BW box,if you do that I would also advise that you pull out the rear output shaft and inspect the splines for wear.But then I'm sure you already knew that.

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TWEETS said:

Hmmmm, a bit over my head all that so I'll explain my problem

I've only had my 1999 4.0 V8 Discovery two to three months and I have suffered a power loss..... she is ok at the start of the journey but the longer the journey lasts the more power she loses, if I slow down or stop I need to accelerate harder to build up speed, also at this point she seems noisier. she seems ok to drive on petrol but I aint drove her any great distance to find out (I will wednesday though)

Have had it into the LPG/Land Rover specialist and they sniffed the exhaust and say she is fine on petrol however on gas she is also giving the correct readings at idling speed but as soon as they increase the revs to cruising speed she gives readings as being too lean, they have assured me a tune up would sort my problem however I'm having difficulty tracking someone down in my area that knows about kits supplied by Tinley Tech...

if a tune up doesn't sort my problem then is there any thing else I can check??

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hippolover said:

Personal experience of LPG cars has been poor. Misfires, uneven running, in fact I'd never fit it even on a small car. LPG may be cheaper than petrol per litre but the fuel economy isn't as good so it's not really beneficial especially when you write in the cost of a conversion. Range Rovers are supposed to be smooth running luxury cars. Point to note, not all mechanics are willing to touch an RR which has been fiddled with in case they get blamed for making it worse!

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Zaphod said:

Sorry slipped/cracked liners ARE due to excessive combustion temps due to excessivly weak fuel maps. TVR and Marcos only suffered it till they binned the fuel maps and later the entire system. Plenty of later engines have been fitted to SD1's and normaly with carbs. OK nothing like as efficent, but also interestingly NO cracked/sliped liners.

Gems is not that great. Mixer systems bad press is due mostly to a moronic persuit of improved economy by weakening the mixture. As for the water loss, that can just as easily happen to a standard engine (or are you implying that a heater hose more likely to leak if attachd to a vaporizer?)

As it happens I do have a dyno for a 3.9 both prior to and after conversion with a mixer ring.. not a Range rover though but an SD1.

189 BHP at 5200 on petrol
178 BHP at 5100 on LPG

Interetingly it it also shows improved torque and power from 2000-3450 on LPG and that was a purely mechanical system with no lambda probe. But it was correctly setup erring on the rich. The car still returned 28MPG on gas.

I have seen a number of engines 'killed' by lpg, and in nearly every case it was a mixer system fitted. Some of these had lambda feedback systems fitted but these had the stepper valve replaced by a manual valve 'Becuse it used less fuel'. And I am certain the manual systems had the gas turned down for 'economy' Only reason SGi systems have not suffered this is because its almost impossible for the owner to do it, they do however suffer a reputaion for being less economical (in fact they are slighly better than a mixer system when both are correctly setup)

Yes SGi systems are better, but a properly setup Mixer system can deliver much better results than many will have you belive. The lambda systems only lack in ultimate power compared to the SGi systems.

The 3.9 I have now has a very basic system, and has covered 79K with it so far. although it is currently out of use due to a viscous unit problem

I have run LPG sicne 1996, and always converted my own cars apart form the 3.9 mentioned above! and had very few probelms. And yes the LPG was less powerfull, ultimatly it always will be thanks to a lower calorific value in the fuel (this is also why converted cars use more LPG than petrol) More recently I have been playing with Megasquirt but using LPG injectors inplace of petrol injectors

Stewart

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