Spark plugs and LPG

Bluesman · May 8, 2018

5 hours ago, ColinBarber said:

This isn't really true. Heat is released more quickly so cylinder head temperatures are higher with LPG compared to Petrol, hence why plugs don't last as long, especially non-iridium ones.

Sorry Colin don't agree with that.

My thanks to, Go-LPG Research - VSR for the following info.

Running Temperature of the Valve Heads and Seats

The most common misconception you'll hear about LPG is that it makes an engine run hotter than Petrol. This is no more than a myth.

LPG has only 85% of the calorific value of the same amount of petrol, so it is impossible for it to create more heat. It can only make 85% as much.

There is one factor missing though - The cooling effect that squirting wet petrol mist into the cylinder has on the valves. The evaporating petrol mist will cool the valves very slightly but that cannot happen when injecting a gas that has already been vaporised before injection. When running on LPG the gas does not have quite as much cooling effect on the valves. As a result of this difference you'd expect to see LPG operation showing slightly higher valve temperatures, but overall that isn't the case. We just established that LPG can only produce around 85% of the heat that petrol can, the lost benefit of petrol mist cooling on the valves is cancelled out by the cooler combusion temperatures of LPG - in short, both fuels end up roughly even when considering valve temperatures during operation.

Even if valve temperatures were to end up slightly higher, that would only present more risk of VSR if the valve seats were too soft for the job (Go back to the Blacksmith analogy in 'Brinelling' (factor 1). Engines that suffer the most are some of the Ford and Honda engines, ALL Jaguar V6's (actually a Ford engine) ALL Subaru engine variants etc. although over 90% of engines made today are just fine.

This is in no way intended as a comprehensive list of unsuitable engines and it would be wise to check with both the manufacturer of your engine and your LPG installer before conversion to find out if your engine has suitably hard valves. The UK LPG website has a list of engines known to have soft valves on a 'Caution' list, but this is not accessible to the general public. In that case it is neccesary to contact your installer prior to booking a conversion so they can check for you. If you are going to have your car converted by us then we'd be pleased to check on that for you

Bluesman · May 8, 2018

8 hours ago, ls400lpg said:

Hi Bluesman

I wanted my MK4 converted to LPG. Was thinking Profess gas but heard mixed reviews. Could you enlighten me on your experience.

I wouldn't go anywhere else and I live 125 miles from where they are. They fitted my LS400 8 years ago and its never missed a beat. I know of several others who had their cars converted by them and there has not been a single moment of trouble.

ls400lpg · May 8, 2018

how much do they charge for LS400 conversionn do you know

Bluesman · May 8, 2018

2 minutes ago, ls400lpg said:

how much do they charge for LS400 conversionn do you know

Give them a ring they won't bite.

ls400lpg · May 8, 2018

good idea lol

Hadrian · May 9, 2018

On 07/05/2018 at 9:24 AM, Malc said:

is it now that plugs have a 60k or maybe 100k miles lifespan and the age they are in situ, that makes them challenging to remove do you think ? everything seizes-up !

In olden times when plugs were changed every 12k miles or at each main service, and when a set of plugs cost about £2/10/6d, that it was an easy job to do .

Just reflecting a little I'm afraid

Malc

Strewth they saw you coming Back in the 60's when I had an Austin A40 I used to change the spark plugs every year. You could get 4 spark plugs for £1 for quite a few years. Petrol was four gallons for £1 .....Nostalgia isn't what it used to be. Then again as an apprentice I was probably earning less than £10 a week.

Malc · May 9, 2018

my memory told me that i thought spark plugs cost that much .... sorry

Malc

dendonc · May 9, 2018

The austin A40's seem to average 3.5k these days, some a lot more, awful things but OKish in their day

https://www.carandclassic.co.uk/list/3/a40/

Hadrian · May 9, 2018

8 hours ago, dendonc said:

The austin A40's seem to average 3.5k these days, some a lot more, awful things but OKish in their day

https://www.carandclassic.co.uk/list/3/a40/

I learn't to drive in a Mk. 2 1100cc A40, then bought as my first car a Mk.1 948cc 469 MKP Funny how you remember these things.

The only major thing I had go on it was the crankshaft. Cost £40 to get that fixed. With the back seat folded down it would carry a lot of gear.

It did suffer (as did many cars of that era) from the dreaded wire worm.

dendonc · May 9, 2018

The early to mid 1950's A40's were more of a comfortable 'family saloon' car, never went in one but I remember them when I see pics of them.

ColinBarber · May 9, 2018

20 hours ago, Bluesman said:

Sorry Colin don't agree with that.

You don't have to agree but it is a fact.

Quote

NGK - The combustion of gas results in higher temperatures. Conventional electrode and housing materials wear out more quickly. That is not the case with iridium

Quote

From Go-LPG

Although LPG produces less total heat ( it has a lower calorific value) that heat is released in a shorter time. The reason for this is that LPG is a 'perfect' gas at ordinary atmospheric temperatures whilst petrol vapour is liquid that has been forced to vapourise. 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, although the difference may not be large enough to show on the temperature gauge. Only the cylinder head temperature (CHT) will increase significantly

Bluesman · May 9, 2018

3 hours ago, ColinBarber said:

You don't have to agree but it is a fact.

We will have to agree to disagree.

My thanks to, Go-LPG Research - VSR for the following info.

Running Temperature of the Valve Heads and Seats

The most common misconception you'll hear about LPG is that it makes an engine run hotter than Petrol. This is no more than a myth.

LPG has only 85% of the calorific value of the same amount of petrol, so it is impossible for it to create more heat. It can only make 85% as much.

dendonc · May 10, 2018

Another thing about LPG, which needs to be kept in mind if relevant, is that you are not allowed to take them through channel tunnel.

sorcerer · May 10, 2018

11 hours ago, ColinBarber said:

You don't have to agree but it is a fact.

8 hours ago, Bluesman said:

We will have to agree to disagree.

I think this is very much a 'horses for courses' argument.

@ColinBarber quotes NGK and @Bluesman quotes Go-LPG.

NGK are a manufacturer of spark plugs and have spent millions of pounds in their research and development department to produce the best product they can for a given job. That is where their strengths lie and it's what they do best. They know the processes, the chemistry, and everything that goes on to ignite fuel in a cylinder.

Go-LPG are installers of LPG fuelling systems into (usually) petrol-driven cars and that's where their strengths lie - how to do a neat, safe and tidy job, and how to match the LPG system to the demands of the car.

Bluesman · May 10, 2018

I have quoted Go LPG Research written by Steven P. Sparrow BSc (Hons) and he states "LPG has only 85% of the calorific value of the same amount of petrol, so it is impossible for it to create more heat. It can only make 85% as much." Given the mans BSc (Hons) background I cant see how anyone can say something which is the opposite of what he says bearing in mind his BSc (Hons) background.

sorcerer · May 10, 2018

1 hour ago, Bluesman said:

I have quoted Go LPG Research written by Steven P. Sparrow BSc (Hons) and he states "LPG has only 85% of the calorific value of the same amount of petrol, so it is impossible for it to create more heat. It can only make 85% as much." Given the mans BSc (Hons) background I cant see how anyone can say something which is the opposite of what he says bearing in mind his BSc (Hons) background.

Oh dear, do you mean this Steven P. Sparrow:

http://www.lpginfo.co.uk/golpgcourt.html

sorcerer · May 10, 2018

Apologies folks - that link above does indeed provide some info but the link below is the one I actually meant to post but now that I've spotted my error above, it's too late to edit that post.

This is the one I should have posted http://www.lpginfo.co.uk/golpg.html

Bluesman · May 10, 2018

Oh dear, will soon have the noose around my neck. What you refer to happened 10+ years ago and the primary complainant ended up setting up a web page to defend Mr Sparrow. Its just a rather upset customer who like alot of people do start issueing threats of legal action and start writing stuff up to the internet all of which may well be unfounded. No one can quote any further on this case as none of us was there. I am sure if you work for a company they could testify that the same has happened to them many times as well.

One thing that cant be dissmissed is has a BSc (Hon) qualifications and may well have a really indepth knowledge of LPG and I wouldnt be comfortable arguing against what he says. The other thing is that we dont know that Mr Sparrow actualy did the work.

The other thing to bear in mind is that as you know there is a lot of jealousy out there in the LPG world with many LPG companies who havent an honest bone in their bodies actualy sit there and review other LPG companies with terrible reviews in the hope it will put off future customers from using them.

Finally I will state that all I am discussing is that "LPG has only 85% of the calorific value of the same amount of petrol, so it is impossible for it to create more heat. It can only make 85% as much."

sorcerer · May 10, 2018

Goes to credibility M'Lud.

I think I'd rather trust a multi-national company with an R&D budget of millions and qualifications coming out their ears than one person with a dubious reputation, BSc (Hons) or not.

dendonc · May 10, 2018

13 minutes ago, sorcerer said:

think I'd rather trust a multi-national company with an R&D budget of millions and qualifications

What your posts do illustrate (literally) is the importance of finding & using a respected installation company.

That said, a lot of care & a tad more than a quick one off google search for names of instillation technicians, maybe good research is really the key to success & a willingness to travel distances with a view to the long term benefits.

ColinBarber · May 10, 2018

13 hours ago, sorcerer said:

@ColinBarber quotes NGK and @Bluesman quotes Go-LPG.

Well I also quoted Go-LPG where they state cylinder head temperatures are higher. This what can damage non platinum and iridium plugs.

This is kind of moot though, Lexus vehicles will typically have those two types of plugs and so LPG will work fine with what comes out of the factory. Just don't fit cheap basic plugs, but then I wouldn't recommend them even if you weren't using LPG.

@Bluesman I'm really not sure why you give any special credibility to having a BSc (Hons) degree. What subject was it in, what grade and when was it obtained - it could be in a completely irrelevant field or too long along to provide any value to the discussion in hand.

Not sure anyone is disputing that fact that LPG only contains 85% the energy of petrol, but that isn't the only factor that affects the environment the plugs are subjected to. The speed of burn is relevant.

Bluesman · May 10, 2018

We will just have to agree to disagree.

I do agree that it's important to make sure that whoever you get to do the conversion that they know what they are doing of. Make sure there are no horses tied up outside. Don't get carried away with a company that says they are recommended by UKLPG, as they are just a company who set themselves up to give you the impression they are the government appointed body over the LPG industry. Nothing could be further from the truth if you were an LPG conversion company you could become a UKLPG recommended garage just by handing over money to them by way of a joining fee annually. Some of the horror stories that have been on this forum and many other forums were systems that were installed by companies who were UKLPG recommended.

I have always chosen Profess to do my cars over the last 8 years X3 cars and all have given 100% good service without a single problem. I also have had friends who have also had their cars converted by Profess and all have given 100% fine service. There are also forum members who have had their cars converted by Profess without any problem. All cars were converted in a day and they were given a courtesy car so you can go off and enjoy some good food and a look at the wonderful Welsh countryside.