Running on lpg

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Ruby Range

Ruby Range

Well-Known Member
Posts
338
Location
Sandwich Kent
was last on here a couple of years ago and then a daughters wedding ended up costing me thousands and my old P38. It’s now time to stop the hurt and purchase another. I’ve found a mint 4.6 vogue which I’m looking at on Monday which has lpg fitted and supposedly running. It’s got 110 k on the clock but in the last 3 years has only done about 2500 miles each year. My question is is the lpg a good thing to have running a 4.6 Thor on or not. I know it’s cheaper but will it do my damage in the long run and secondly is there obvious thinks I should look at with this system on. Comments by Monday will be appreciated
 
+1
My Previous THOR 4.6 did over 60K miles on LPG with me and never gave me any trouble until the end when the ECU started playing up. When I bought it it already had LPG fitted and had done 56K miles.
I sold it to a guy on here and he had it repaired and as far as I know, its still going strong.
 
thanks for your replys guys was just a little concerned as I know that lpg runs hotter than petrol and that's the last thing I think a 4.6 needs. o big shakes as will only be a weekend motor so if I had to run just on fuel I can live with it but for those few bigger trips would like the lpg option
 
Personally I dont like lpg on the basis of heat and valves burning out on an engine designed a long time ago BUT that is purely personal. Definitely cheaper but not by that much in this neck of the woods
 
Well I was a little worried about that but the mileage I’m going to do is minimal and over the last 4 years it’s done less than 10000 miles and with full LR service history the motor should be good, that’s just given it the kiss of death
 
For what it's worth, DON'T. 94mm RV8's (all except the original 3.5L) need high combustion chamber temperatures like they need a hole in the head.
Ask me how I know. On second thoughts, don't :(
This is a well discussed subject, I suggest you research it thoroughly.
 
The way i see it, you only burn valves if the mixture is lean, you also run hotter combustion if you're lean. The extra heat is an issue if your cooling system isn't up to scratch, but the main thing is, make sure it doesn't run lean, especially on lpg
 
Ruby Range said:
was last on here a couple of years ago and then a daughters wedding ended up costing me thousands and my old P38. It’s now time to stop the hurt and purchase another. I’ve found a mint 4.6 vogue which I’m looking at on Monday which has lpg fitted and supposedly running. It’s got 110 k on the clock but in the last 3 years has only done about 2500 miles each year. My question is is the lpg a good thing to have running a 4.6 Thor on or not. I know it’s cheaper but will it do my damage in the long run and secondly is there obvious thinks I should look at with this system on. Comments by Monday will be appreciated
Click to expand...


I have the BRC system on my 4.6 Thor. was fitted with about 1-0k on the clock, now up to 147k no problems at all. doesn't need valve lube kit on it. you'll go through a set of plugs a year or so, BPR6ES, depending on mileage, don't bother with the super duper LPG plugs at £60 a set, does no difference, last no longer than a set of BPR6ES at £18 a set

LPG makes the RR cheap to run ! my Cayenne has the same BRC system with valve lube and my L322 Supercharged the Landi-Renzo with valve lube
 
My 3.5EFi has been on LPG for years. IIRC I did the conversion in the late 90s.
Did a top end overhaul year before last & the valves & seats were in excellent condition. Had heard all the stories about how bad LPG is for them & was curious as to what I would find.
Bear in mind the ally heads have hardened valve seats & leaded fuel has been gone for years.
Or does everybody with a V8 use the 'additives' pedalled on ebay etc?
 
No, no issues running LPG. Not on the GEMS anyway and the Thor is pretty much the same.

Not sure if it runs hotter. There's certainly less lubrication for the valves so they might get hotter but the Rover parts can take it. The newer Jag engines need Flashlube or similar.
 
LPG has a lower calorific value than petrol It produces less total heat and therefore less peak pressure in the cylinder. Simply put lpg gives slightly less 'bang' per charge. LPG is slightly less potent than petol.

When people say it produces significantly more heat that is bull it produces the same as petrol - CHT will increase slightly but not enough to blow holes, unless it is wrongly set up, or the heads are made of cheese. ;)

The injection into the cylinder will create more heat for the valves as there is no cooling effect on the seats but the RV8 has very hard valve seats and it's not bothered.

On some engines a Vacuum oil feed can be fed into the valves to help cool the seats AJv8 a prime example.. ;)

A bad mix will cause more heat as the same with any fuel, the correct mix is essential

LPG is also very clean compaired to petrol it doesn't posess the impurities petrol contains so Engine oil lasts longer and sludge build up is reduced believe it or not.

so engine life is extended. :)
 
Last edited:
As @Henry_b
I was under the impression it burns cooler, but not sure now or why. So not going to get into it.
Calorific value of LPG is also higher:cool:

At the end of the day a good system fitted correctly is better for the pocket, air pollution, and as long as the engine/cooling system is sound and everything is maintained should be no problem.

We have a little “uncared for 2.0mpi” and it runs better on LPG than petrol. Even starts from cold on LPG.

You will also have to go some to fail an MOT emissions test on LPG:).

If you buy, get 1 with LPG fitted already as I think payback is a lot of miles. But I like it as a fuel.

J
 
marjon said:
As @Henry_b
I was under the impression it burns cooler, but not sure now or why. So not going to get into it.
Calorific value of LPG is also higher:cool:

At the end of the day a good system fitted correctly is better for the pocket, air pollution, and as long as the engine/cooling system is sound and everything is maintained should be no problem.

We have a little “uncared for 2.0mpi” and it runs better on LPG than petrol. Even starts from cold on LPG.

You will also have to go some to fail an MOT emissions test on LPG:).

If you buy, get 1 with LPG fitted already as I think payback is a lot of miles. But I like it as a fuel.

J
Click to expand...

The Clorific value of LPG is less that of petrol :cool: 70-85% can't remember the exact number.
The cooling effect of liquid petrol droplets is not present with LPG and the total heat is released more quickly. A greater heat spike is the result. The engine will run slightly hotter if the mixture is leaner although if set correctly the heat difference is negligable. Only the Cylinder head temp will increase slightly.
An engine will run smoother on it as the Octane rating for LPG varies between 105 and 120 less "knock" is the result.
 
Henry_b said:
The Clorific value of LPG is less that of petrol :cool: 70-85% can't remember the exact number.
The cooling effect of liquid petrol droplets is not present with LPG and the total heat is released more quickly. A greater heat spike is the result. The engine will run slightly hotter if the mixture is leaner although if set correctly the heat difference is negligable. Only the Cylinder head temp will increase slightly.
An engine will run smoother on it as the Octane rating for LPG varies between 105 and 120 less "knock" is the result.
Click to expand...

Yes, that makes sense. The LPG changes phase in the evaporator and takes its heat from the coolant. Petrol is a mist so phase change from liquid to gas takes heat from its surroundings and inlet valves will be first. You certainly get a few mpg less on LPG but you would because shorter chain carbon so less to burn into CO2.
 
Henry_b said:
The Clorific value of LPG is less that of petrol
Click to expand...

Don’t agree sorry.:(

Henry_b said:
Only the Cylinder head temp will increase slightly.
Click to expand...

I posted a link about this recently and got ****ed off.;)

Grrrrrr said:
The LPG changes phase in the evaporator and takes its heat from the coolant. Petrol is a mist so phase change from liquid to gas takes heat from its surroundings and inlet valves will be first. You certainly get a few mpg less on LPG but you would because shorter chain carbon so less to burn into CO2.
Click to expand...

But doesn’t that depend on the stoichiometric mix? LPG does just overlap in the carbon chain.

We all agree LPG is a dry fuel and lacks lubricants.

As I said earlier I am not going to get into it.

LPG is fine to run on a sound engine/system:) what’s the debate:)

J
 
My view is purely personal in fact once upon a time I fitted lpg systems and even had a classic and Disco on lpg.
 
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