To LPG or not to LPg

Given the costs of fuel are going to continue to spiral maybe I should review the cost benefits of LPG on my 4.6 HSE.
I do almost no town driving just run from London to Wiltshire or Devon on weekends, say 10,000 miles a year.
Now the beast has 120k miles on her but seems to be ok and burns little oil etc.
RPI have a LPG do-it-your self kit on fleabay for someting like £800 odd. This is not a multipoint system obviously at that money.
Ok if not the best system it is cheap so a pay back won't be too long.
Pointers as to bunging on this system on an aged engine like mine would be appreciated.

general consensus is that they are a lot of trubble, unless yu want to get it done professionally, certificated, with warranty and someone to shout at .

I dont have a petrol engined P38 but if I did and I did want it LPG'd then I would go with a multi-point system every time, I've read lots and lots of stories of people with the single point systems who get backfires, destroyed MAF's and goodness knows what else.

If you MUST have LPG get it done by a professional and make sure its a multi-point system. Personally I wouldnt want to loose the spare wheel in the boot but I suppose that un-avoidable with an LPG setup.

Then of course theres the one other thing of making sure its all safe. A few months ago I bought something off eBay for my P38 and went to pick it up from the guy. When I asked him why he was selling all his stuff off he told me because his P38 had gone up in flames due to a fault with the LPG system. Apparently due to a faulty solenoid or something too much gas made its way into the engine resulting in a large gas build up, engine backfired and lit the gas. First thing he knew about i was when he was driving along and suddenly he got GEARBOX FAULT show on the dash and then a funny burning smell, he pulled over and was going to get out to see what was up when the engine died and the cabin started filling with smoke. Within seconds the whole engine bay had gone up in flames and in the end it completely wrote off the vehicle. He showed me the photos of the wreck and it was not a pretty sight, the side wings had practically melted into a puddle on the ground, it was just completely wrecked and not a nice sight.

So personally I would only let a pro install the system and make sure its fully checked over and certified if you really do want LPG. The combination of seeing this guy's photos plus loosing the spare wheel in the boot is enough to put me off LPG for good.

-Wills

With regards to the LPG fire.. Exactly the same thing can happen with petrol!.

The RPi kits are a HUGE ripoff, that Had alook at theor website and saw a Leonardo based system at £1089.. which will be costing them less than £250 to get in. You can get SGi sysems minus the tank for £600 buy it now off Ebay, add about £100 for a tank and your have the lot.

Mixer systems only backfire when set up by morons or have been fiddled with by owners to weaken the mixture in the mistake persuit of more economy. (the backfires are caused by weak mixture in the inlet manifold).

The conversion kits are easy to do yourself over a weekend, although you may feel drilling and tapping the inlet manifold for the injectos best left to another, Problem with the 'pros' is half of them have no idea about fuel systems, the certified 'pros' are no better. But fitting it yourself is not hard, just understand what you are tyring to do, make sure all the unions are good and it will present no promblem

Stewart

(Runing LPG sicnce '96!)

I have the RPi single point system fitted to mine, and although not as economical as a multipoint, it is fine. It was installed and certified by RPi along with an Optimax ECU chip (runs better on petrol as well), 50kV dual fuel ignition amplifier and a few other bits. Mine is also de-cat with a separate lambda sensor for the OMVL electrikery to work, tubular headers and stainless sports exhaust. On a high mileage engine it would be advisable to put a new timing chain on first.

Will Carado-Hodgkins said:

Given the costs of fuel are going to continue to spiral maybe I should review the cost benefits of LPG on my 4.6 HSE.
I do almost no town driving just run from London to Wiltshire or Devon on weekends, say 10,000 miles a year.
Now the beast has 120k miles on her but seems to be ok and burns little oil etc.
RPI have a LPG do-it-your self kit on fleabay for someting like £800 odd. This is not a multipoint system obviously at that money.
Ok if not the best system it is cheap so a pay back won't be too long.
Pointers as to bunging on this system on an aged engine like mine would be appreciated.

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hiya my 97my 4.6 hse had a single point system fitted when i bought it , it was bobbins , it was also proffessionally installed by the company you mentioned , when i rang for some advice i spoke to the most arrogant cretin you could imagine , so , off the lot came and i fitted a complete under bonnet sequential kit supplied by tinley tech , it knocks spots of the old single point gas ring kit !!!!!!!!!!!!!!!!!.
the cost of the under bonnet kit was £850.00 give or take a quid or two that included , ready made up injector harness , software to set it up on your laptop, and an interface cable to connect to the lpg ecu .
the choice is yours mate but i know what i would choose every time .
rick.

Tinley tech is the company I looked at.
Other members have their sytem fitted and have had great success, they can install the system for you


Tinley Tech LPG Equipment - LPG conversion kits, LPG advice, LPG parts

Will Carado-Hodgkins said:

Given the costs of fuel are going to continue to spiral maybe I should review the cost benefits of LPG on my 4.6 HSE.
I do almost no town driving just run from London to Wiltshire or Devon on weekends, say 10,000 miles a year.
Now the beast has 120k miles on her but seems to be ok and burns little oil etc.
RPI have a LPG do-it-your self kit on fleabay for someting like £800 odd. This is not a multipoint system obviously at that money.
Ok if not the best system it is cheap so a pay back won't be too long.
Pointers as to bunging on this system on an aged engine like mine would be appreciated.

Click to expand...

At 10,000 miles a year do you think it will pay for itself, and a diy fitting kit??, best do a bit more maths and research first, hate to think the kit is ****e, or you wont be able to get it fitted without help that wont be available, or that old saying we don't repair them we know nothing about those ones, and yer guarantee is written on an old bus ticket.

400 quid a year road tax and 25 quid a day in london fur congestion charge, personally I would burn it and buy a sports and have some fun wif the roof down.

I'm amazed that anyone considers fitting a cooker ring LPG system to a car with an adaptive engine ECU as complex as Gems on a RR.Simple fact is you may think its working OK and the car drives alright - but its not.I have never seen one that can accurately fuel a 4.0/4.6 v8.Let alone the restriction from the venturi of the ring itself.(The smallest bore I have seen on a 4.6 is 36mm - quite how 4.6ltrs is supposed to breath through that I dont know)
The later sequential kits can be very good but many are not set up properly as the installers either think the "autocal" from the LPG software is good enough,or they dont have the kit,time or understanding to do it properly.

eightinavee said:

I'm amazed that anyone considers fitting a cooker ring LPG system to a car with an adaptive engine ECU as complex as Gems on a RR.Simple fact is you may think its working OK and the car drives alright - but its not.I have never seen one that can accurately fuel a 4.0/4.6 v8.Let alone the restriction from the venturi of the ring itself.(The smallest bore I have seen on a 4.6 is 36mm - quite how 4.6ltrs is supposed to breath through that I dont know)
The later sequential kits can be very good but many are not set up properly as the installers either think the "autocal" from the LPG software is good enough,or they dont have the kit,time or understanding to do it properly.

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I am amazed anoyone thought and engine management that comlplex was needed, even then it does not work as it runs too lean and as a result the liners crack. As for the breathing dificulties with the mixers, can't say I have ever noticed a problem with a correctly setup LPG system. In fact the best one yet is the one on my 3.9 which ia a wholey mechanical system, only elctronic intervetion is to switch it over. If it drives alright it probbly is alright.

Stewart

what eight is saying is that single point is just to old tech for a modern ecu controlled engine.
the point he is making about the mixer is the restrictive design of the mixer reduces dramatically the amount of air that can be drawn into the engine , thus reducing the power output , if an engine could operate in an effieciant manner with such a restriction then why do manufactures spend millions on development of induction systems .
a single point system is acceptable on older engines i.e the classics but, they are rubbish on the p38`s .
also ive seen a good few so called "proffessionally installed systems" and they have been nothing better than a lash up !!!!.
lpga certification means bugger all other than someone has "attended a course" its certainly not a guarantee of competance or quality of an installation.
its not rocket science at all to fit an lpg system properly but, its a little more difficult to set it up correctly.
rick.

And excatly in what way is a p38 engine differnt to a Classic engine? its still a pushrod OHV V8, in fact the SAME pushrod OHV V8. No fundamental changes were made to it. It is still the '62 buick engine with some bigger holes, hardly high tech!

Stewart

Zaphod said:

And excatly in what way is a p38 engine differnt to a Classic engine? its still a pushrod OHV V8, in fact the SAME pushrod OHV V8. No fundamental changes were made to it. It is still the '62 buick engine with some bigger holes, hardly high tech!

Stewart

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cept the yank enjun versun had a downdraught carb and these ****e have complicated fuel injection. or have I missed somut.

And the yanks dunt care about fuel consumpion of 12mpg.

Spelling lessons by the look of your post.

Zaphod said:

Spelling lessons by the look of your post.

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I can let you know it took me years to get to that standard of ilitooracy

While the injection system is more complex than a carb, I'm sure you know it does the same thing, arranges the right amount of fuel for the air drawn in. Injection is more efficient most of the time (but not all the time!). But there is no reason the mixer LPG systems can't work on the later engines, and in many cases they do work. SGi is better, but don't write off the older systems as they can a do work well with these engines!

Stewart

Zaphod said:

While the injection system is more complex than a carb, I'm sure you know it does the same thing, arranges the right amount of fuel for the air drawn in. Injection is more efficient most of the time (but not all the time!). But there is no reason the mixer LPG systems can't work on the later engines, and in many cases they do work. SGi is better, but don't write off the older systems as they can a do work well with these engines!

Stewart

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Yep you are right, and I have not written them off, however it's a **** load of dosh for a DIY kit which might or not have any back up, and might be ****. and might not be cost effective long term on low mileage usage.

Don't know enough about Gas so it would be wrong to make a comment here, but remember that the ecu on the engine checks the fuel ratios and adjusts engine timing as well, so I would guess that an old system might have compatability issues.

As I said at the begining check the maths, and research the system, and that is not simply checking with the supplier, cos he's going to say it's fine probably, then fook off.

Zaphod said:

While the injection system is more complex than a carb, I'm sure you know it does the same thing, arranges the right amount of fuel for the air drawn in. Injection is more efficient most of the time (but not all the time!). But there is no reason the mixer LPG systems can't work on the later engines, and in many cases they do work. SGi is better, but don't write off the older systems as they can a do work well with these engines!

Stewart

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You are over simplfying the differences,the LP variants of the Rover v8,4.0/4,6 share few components with the original 215 Buick motor from 1954.As you say the main diff is the 94mm bore size,but dont forget the heads are different,inlet manifold,front cover/oil pump and the block is totally different too,with cross bolted mains,external webbing and a hole/plate arrangement for the crank sensor.
Both Gems and the later Motronic injected cars do a darn sight more accurate job - esp long term of fuelling and sparking the engine.Dont forget how poor the accuracy of a dizzy is,(esp with a slack t,chain) compared to the crank sensor reading a 36-1 flywheel.
You may think a gas ring LPG is doing OK,but dyno it and monitor what is coming out the back and you will see how bad it is.Lean mixtures and loss of coolant from vaporiser/hose leaks have killed loads of these engines - and the story about the lean mixture from the efi systems causing slipped liners is rubbish.The truth is that the 94mm bore leaves too little alloy supporting the liner.Hence the stepped liner conversion,which if done properly sorts the engine for good.
Even the sequential gas systems need careful tuning if long term fuel trims are not to be messed up,unfortunately this often does not happen.

eightinavee said:

You are over simplfying the differences,the LP variants of the Rover v8,4.0/4,6 share few components with the original 215 Buick motor from 1954.As you say the main diff is the 94mm bore size,but dont forget the heads are different,inlet manifold,front cover/oil pump and the block is totally different too,with cross bolted mains,external webbing and a hole/plate arrangement for the crank sensor.
Both Gems and the later Motronic injected cars do a darn sight more accurate job - esp long term of fuelling and sparking the engine.Dont forget how poor the accuracy of a dizzy is,(esp with a slack t,chain) compared to the crank sensor reading a 36-1 flywheel.
You may think a gas ring LPG is doing OK,but dyno it and monitor what is coming out the back and you will see how bad it is.Lean mixtures and loss of coolant from vaporiser/hose leaks have killed loads of these engines - and the story about the lean mixture from the efi systems causing slipped liners is rubbish.The truth is that the 94mm bore leaves too little alloy supporting the liner.Hence the stepped liner conversion,which if done properly sorts the engine for good.
Even the sequential gas systems need careful tuning if long term fuel trims are not to be messed up,unfortunately this often does not happen.

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Well there you are then exactly what I tried to say, I think, waste of time.

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