LPG

[warpspeed]

Hey everybody, i don't proclaim to be an expert although i am qualified to convert vehicles but i thought i'd start a thread on LPG to try and answer any questions and try and dispell some of the myths surrounding it especialy as a performance fuel, so fire away and i'll try and do my best :) i'm assuming a few of you will have seen Emma's 5 at Mallory and may be curious as to how it stacks up against petrol. We are currently helping PPC mag to do an article as a performance fuel which hopefully should be out in the next couple of months so i thought i'd try and get some feedback as to the most common or unusual questions you all have, thanks for your time :)

[THE MASTER]

as lpg is a very dry fuel. is there any mods that need doing to the top of the engine as in valves etc :)

[warpspeed]

as lpg is a very dry fuel. is there any mods that need doing to the top of the engine as in valves etc :)
most engines that run on unleaded will run on lpg without problem, lean burn engines such as the ones in honda cr-v's don't like gas due to the 5%or so heat increase, on those engines we use what's called flashlube which drips a lead replacement type lubricant into the inlet manifold and have no problems after that :)

[Adey aka Ewok]

are there any performance benefits to running lpg?

[warpspeed]

are there any performance benefits to running lpg?
OH YES!!!! straight out of the pumps the octane rating is 107ron :D although the calorific value is lower and it burns slower it is far more resistant to det which means more boost and more ignition advance is possible and the fact that it's half price helps :D

[Ian S]

So does that mean it's better for lower reving longer stroking engines?

[ROB C2GTT]

New poster! (less than 10 posts)

My 4.6 range rover is running on gas and every now and then i get backfiring through the inlet manifold. Its enough to blow the air filter off sometimes! any ideas? it is an old system on it and it injects the gas into the intake of the plenum. Anything i can do to try and stop it?

[warpspeed]

So does that mean it's better for lower reving longer stroking engines?
to a certain extent yes allthough i am looking into developing liquid injection kits, and that would change things as the problem with vapour injection systems is that you start to run out of injector duration over 7-8000revs depending on the engine used. Another advantage with liquid injection is that you get a chargecooling effect when the liquid lpg leaves the injectors i.e it tries to freeze! which could reduce cgarge temperatures by 100deg celcius! :D The only prob is the solenoids in the injector bodies creates heat which in turn causes the lpg to boil, not good!!!!

[warpspeed]

New poster! (less than 10 posts)

My 4.6 range rover is running on gas and every now and then i get backfiring through the inlet manifold. Its enough to blow the air filter off sometimes! any ideas? it is an old system on it and it injects the gas into the intake of the plenum. Anything i can do to try and stop it?
Does it have a large alloy ring bolted on just in front of the throttle body? if it does it's a closed loop system which works well within a particular operating window, the problem with rover v8's is you get a lot of negative pulses in the intake system at idle in particular which in turn blows your gas mixture backwards. i suspect it's running slightly too ritch at idle, have a look at your reducer/vapouriser that converts lpg to a vapour, there should be two screws on it, try turning the smallest one clockwise by half a turn and the try driving it. If you not confident with that it can be set up with a four gas emissions tester but you must remember that the mixture for gas is 15.5:1 not 12.5:1, hope that helps.

[ROB C2GTT]

New poster! (less than 10 posts)

Cheers mate that sounds about spot on as it seems to be when i pull away from idle that it does it? It has the system that your describing, so ill get it on the gas analyser at work and have a look. Cheers:)

[warpspeed]

New poster! (less than 10 posts)

Cheers mate that sounds about spot on as it seems to be when i pull away from idle that it does it? It has the system that your describing, so ill get it on the gas analyser at work and have a look. Cheers:)
Nae bother :)

[ROB C2GTT]

New poster! (less than 10 posts)

One other thing if ya dont mind? If it running rich could it do the same as petrol and wet the plugs up? Its just the other day i ran down to work in it (1/2 mile) on gas and it cut out as i got in the carpark and wouldnt start agian. I went to it a couple of hours later and it fired up straight away? It did smell of gas when it cut out.

[Sparkie]

to a certain extent yes allthough i am looking into developing liquid injection kits, and that would change things as the problem with vapour injection systems is that you start to run out of injector duration over 7-8000revs depending on the engine used. Another advantage with liquid injection is that you get a chargecooling effect when the liquid lpg leaves the injectors i.e it tries to freeze! which could reduce cgarge temperatures by 100deg celcius! :D The only prob is the solenoids in the injector bodies creates heat which in turn causes the lpg to boil, not good!!!!

could you not get around the 7-8000rev limit by fitting extra injectors? or would the control of them become an issue?

im thinking that flashlube would be a good idea on the gtt, as the piston rings are really only lubed by splash from the crank, and by taking away potential lubrication from the fuel, might make the rings/liners wear out quicker- especially at engines with larger turbos that need the revs to make power. is that possible?
(if you need an example of this try adding 1 litre of diesel to your normal petrol next time you fill up, car revs alot more freely)

[warpspeed]

New poster! (less than 10 posts)

One other thing if ya dont mind? If it running rich could it do the same as petrol and wet the plugs up? Its just the other day i ran down to work in it (1/2 mile) on gas and it cut out as i got in the carpark and wouldnt start agian. I went to it a couple of hours later and it fired up straight away? It did smell of gas when it cut out.
Yeah it can flood in a similar way although not as bad as petrol, check your plugs to see what they are and what the gap is compared to standard, ONLY run copper cored plugs with lpg and close the gaps up by about 20% over standard, the reason behind this is that spark plug needs about twice the voltage to ignite the gas and also closing the gap advances the ignition slightly, if you ran purely on gas you could advance you ignition timing by 16degs easily which would give you better performance than on petrol :) another reason for running copper is that due to the voltage required platinum/iridium plug no matter what brand or how much you payed for them will break down within 5000miles and i would put money on that! Once platinum/iridium plugs start breaking down they CANNOT be cleaned up at all! unlike copper whereby you simply close the gap slightly each service, you should get between 10-15000miles that way.

[ROB C2GTT]

Cool cheers buddy youve been most helpful i shall regap the plugs tommorrow. I know it has NGKs in it at the moment.

[warpspeed]

could you not get around the 7-8000rev limit by fitting extra injectors? or would the control of them become an issue?

im thinking that flashlube would be a good idea on the gtt, as the piston rings are really only lubed by splash from the crank, and by taking away potential lubrication from the fuel, might make the rings/liners wear out quicker- especially at engines with larger turbos that need the revs to make power. is that possible?
(if you need an example of this try adding 1 litre of diesel to your normal petrol next time you fill up, car revs alot more freely)
Well i'm having to drill out the injectors for my pulsar engine, they started of as 'c's which are 3.8mm int dia and i'm taking them out to 4.8mm to give you an idea Emma's car is running on 'c's and that's making 170HP just now.
flashlube will work fine on a gtt and the worst that could happen is that youemissions would be a touch higher, but that doesn't matter as gas emissions are about 5% of a petrols in general. something modern car owners don't realise is that if you run a brand new car on gas you can chuck your cat away and the car is then tested on the 1974 emissions test but you must tell the tester it'sw on gas!
Yes using extra injectors and/or reducers is fine but even mappable gas ecu's won't control extra injectors so it needs to be aftermaket ecu's capable of running low impedance or 'peak and hold' injectors and using the petrol pump power supply to open the solenoid as legally we aren't allowed to open them using the switched live in case of an accident. i.e. our valves must shut if the engine stalls

[Adey aka Ewok]

so is the lpg fired in as a gas or as a liquid?

[Adey aka Ewok]

the omex 600 ecu (that i use) can run low impedance injectors if used with balast resisitors

[warpspeed]

so is the lpg fired in as a gas or as a liquid?
systems just now can only supply it as a vapour at around 1-1.5bar, liquid is the way ahead but nobody except Nicolson Mclaren have any experience with it and the only reason they didn't start selling kits were because they would have to make loads of different parts and they didn't think the market was big enough for them, i have spoken to them a few times and they have been helping me with injector design. I firmly beleive that liquid injection is the only way forward for the lpg industry and we are actively pursuing it. The person i spoke to at Nicolson Maclaren reckoned that a 3ltr v10 f1 on liquid lpg would produce around 1500HP! There is a company in australia that has made liquid injection kits but they wouldn't be suitable for my ideas, however on a totally standard v8 (they never did any mappig at all)they made 20% more power.

[warpspeed]

the omex 600 ecu (that i use) can run low impedance injectors if used with balast resisitors
In that case yes you can run on gas, i'll try get a price worked out for you in the next day or so

[Adey aka Ewok]

my itbs are open at the ends, bar small sock filters, what stops the gas floating away at idle?

[warpspeed]

my itbs are open at the ends, bar small sock filters, what stops the gas floating away at idle?
The gas is injected, so there isn't really any excess floating about :) The only time that would happen is with a closed loop system such as that fitted to Rob's range rover and the reason is that the mixer ring is like a cooker gas ring turned inside out and fitted into a venturi so the airflow pulls the gas in, however if the pressure at the reducer at idle is set too high the gas kinda floats out and then when you put your foot down you have a rich mixture which then ignites in your intake system, hence BIG backfires that can and will blow an airbox apart with spectacular result (wish i'd taken photo's of some of the airboxes i've seen over the years! :eek:)

[Sparkie]

systems just now can only supply it as a vapour at around 1-1.5bar, .

ok, so correct me if im wrong.... if you are running about 1.5bar of boost, then the gas won't have enough pressure to inject itself into the engine?

unless you convert to a Gordini turbo style suck through the turbo style system?

[warpspeed]

ok, so correct me if im wrong.... if you are running about 1.5bar of boost, then the gas won't have enough pressure to inject itself into the engine?

unless you convert to a Gordini turbo style suck through the turbo style system?
Sorry should have made it a bit clearer, reducer runs above manifold pressure :)

[Adey aka Ewok]

what sorta mpg do you get on an average 2.0ltr engine running pure lpg?

[warpspeed]

what sorta mpg do you get on an average 2.0ltr engine running pure lpg?
As long as you can advance your ignition timing to re-claim the power lost by the slower burn time your mpg should be about the same :)

[Chris Hebden]

I've been doing some research into running duel fuel system (for someone else).

Whats the constraints on installing the injectors into the inlet manifold along side the standard injectors? Is thier specific places that they need to be installed? Whats the legalities of installing the system your self, does it have to be installed by an "approved" person? One more, my understanding is on a duel fuel system the petrol starts the car off and after a certain RPM the LPG system takes over, is this the case? If not and you can manual choose to run LPG only is their anything you need to do before the switch to get any excess fuel out of the plenums?

Thanks very much for answering questions, i have found the read extremely helpful!

[stuTHC]

Great thread Scott :agree:
Some really good info on here, nice one :)

[warpspeed]

I've been doing some research into running duel fuel system (for someone else).

Whats the constraints on installing the injectors into the inlet manifold along side the standard injectors? Is thier specific places that they need to be installed? Whats the legalities of installing the system your self, does it have to be installed by an "approved" person? One more, my understanding is on a duel fuel system the petrol starts the car off and after a certain RPM the LPG system takes over, is this the case? If not and you can manual choose to run LPG only is their anything you need to do before the switch to get any excess fuel out of the plenums?

Thanks very much for answering questions, i have found the read extremely helpful!

The injectors should be as close to the valves as poss, same as petrol injectors really. You can fit a system yourself and have it certified by an approved installer for around £100, i personally wouldn't as there are a lot of parts of the system that i can't see without removing a lot of parts in most cases, particularly with an injection system(hope that makes sense! :))
older closed loop systems can be started on gas if you want but in general modern systems switch over automatically once all the system parameters have been checked and met by the ecu, you simply get in and drive.

Glad to be of help :)

[warpspeed]

Great thread Scott :agree:
Some really good info on here, nice one :)
Nae bother :)
There's a lot of myths out there about lpg and even i find it difficult getting answers from people that have been in the industry for years! It's also in my interest to let people what i know about lpg as better informed people can make better choices about lpg which in turn should help get rid of some of the myths! :D

[warpspeed]

OH YES!!!! straight out of the pumps the octane rating is 107ron :D although the calorific value is lower and it burns slower it is far more resistant to det which means more boost and more ignition advance is possible and the fact that it's half price helps :D

I have to correct myself here as the calorific value of lpg is actually 10% higher but it is 20% less dense so if you could get the fuel to be more dense i.e. keep it as a liquid, we would get more power.

[Woznaldo]

I know that cylinders are used for tanks but, can 3 or 4 slim cylinders be linked together to fit in the original tank space?

I don't recall much detail about the tank used for Emma's car in the PPC article?

[EmmaB510]

I know that cylinders are used for tanks but, can 3 or 4 slim cylinders be linked together to fit in the original tank space?

I don't recall much detail about the tank used for Emma's car in the PPC article?


Yes tanks can be linked, when Scott is converting the American motorhomes thats how it is done :)

my car had a round tank that fits (almost) where the spare wheel was, we had to lift the boot floor slightly to allow for clearance at the bottom. :D

on bigger cars like range rovers etc the round tanks fit nicly in the spare wheel well ;)

[Woznaldo]

Thanks Emma, love the car.:cool:

[6FOOT6]

I was looking at doing a LPG conversion to my BMW V8.

Cost of conversion is around £2K give or take 500 quid.
Doing around 6 to 8K miles a year , the conversion would take around 4 years to pay for its self in the money I would save in fuel bills.:cry:

If I was back doing 30 to 40K a year it would pay for its self way sooner, but im not so its good old 95/99RON for me.:cooter:

[ROB C2GTT]

I know that cylinders are used for tanks but, can 3 or 4 slim cylinders be linked together to fit in the original tank space?

I don't recall much detail about the tank used for Emma's car in the PPC article?

My range rover has a round tank (75L) in the spare wheel well and another 100L tank behind the back seat. Can go to the moon and back if i fill them and fill with petrol too.