Lpg Spark Plugs

[oliver261]

since ive fitted ngk LPG specific spark plugs i feel that my economy has dropped on gas.

trouble is i jumped in too early and did it almost straight after the conversion, so didnt really get to know the system on the standard plugs. it quickly became the norm, but i did the maths the other day and at 70-80mph motorway drive im only getting 23mpg. lower than ive seen reported on this site.

ive moved since so am miles away from the installer so not convenient to just nip in and have a chat about it.

done some googling but anyone got any experience with them, or do you just stick to the standard denso's?

[Bluesman]

since ive fitted ngk LPG specific spark plugs i feel that my economy has dropped on gas.

trouble is i jumped in too early and did it almost straight after the conversion, so didnt really get to know the system on the standard plugs. it quickly became the norm, but i did the maths the other day and at 70-80mph motorway drive im only getting 23mpg. lower than ive seen reported on this site.

ive moved since so am miles away from the installer so not convenient to just nip in and have a chat about it.

done some googling but anyone got any experience with them, or do you just stick to the standard denso's?

you could always give the installer a ring. Mike

[oliver261]

yeah ive had a phone chat with them but them a couple of times. (2 different lads there). the one who seems to do most of the spanner work is always mad busy so in a rush said the mileage was about right for a 30mpg car on petrol.

other, whose more the salesman, said he'd had feedback from a couple other customers saying they didnt think much of the lpg spark plugs.

seemed a bit inconclusive. as did googling info on other cars. i know conversions are popular on here, so was wondering if anyone on here had experimented with them.

came about as when i picked the car up after the conversion the fella asked when the last time they were changed as lpg needs a particularly strong spark, and it will help economy. i didnt know offhand, but when i looked in the docs they were due, so i changed them. meaning i only did one major journey with the standards, im sure i remember gettign 320miles on my odometer though. now im rarley getting 260.

[brendangeorge]

Hi Oliver

I used to average 22MPG on petrol, in my LS430, (for 120K miles car computer – not accurate but not far off) doing mixed high speed motor way and short runs – all with a heavy foot and taking no prisoners (the cops did once or twice though). My wife could get 32 MPG on the motor way.

I had a BRC LPG conversion fitted and in the summer average 250 miles on the 65 useable liters in my tank – this is about 17.4 MPG on LPG. LPG has about 80% of the energy of petrol so this works on the back of my fag packet.

My consumption went to hell just before Christmas and the MoT. I had an intermittent engine warning light and swapped the Lamda sensor on bank 2 cat – the real problem was a pin hole in the exhaust just in front of the sensor. I had it welded up and the beast passed its 11th MoT at 204K.

I have not changed anything on the car since the conversion – I am not sure why you would need different spark plugs (I know LPG burns hotter). I fitted a Flash Lube kit because my mate had valve oil seal problems and needed a head rebuild (£5K at Lexus £2.5K at Toyoda) and I lost my bottle. I am not sure if Flash Lube is effective but is not expensive.

I just checked my last two fill ups and I am averaging 15.4 MPG on LPG – this does not surprise me because it is winter and I have also been doing a lot of short trips.

No matter how “nicely” you drive a two ton car it will burn a lot of fuel so LPG is the only option

Good luck

Bren

[Bluesman]

yeah ive had a phone chat with them but them a couple of times. (2 different lads there). the one who seems to do most of the spanner work is always mad busy so in a rush said the mileage was about right for a 30mpg car on petrol.

other, whose more the salesman, said he'd had feedback from a couple other customers saying they didnt think much of the lpg spark plugs.

seemed a bit inconclusive. as did googling info on other cars. i know conversions are popular on here, so was wondering if anyone on here had experimented with them.

came about as when i picked the car up after the conversion the fella asked when the last time they were changed as lpg needs a particularly strong spark, and it will help economy. i didnt know offhand, but when i looked in the docs they were due, so i changed them. meaning i only did one major journey with the standards, im sure i remember gettign 320miles on my odometer though. now im rarley getting 260.

This is the first time I have ever heard of having special spark plugs because of running on LPG and I have been using LPG now for the past 16 years. Mike

[brendangeorge]

yeah ive had a phone chat with them but them a couple of times. (2 different lads there). the one who seems to do most of the spanner work is always mad busy so in a rush said the mileage was about right for a 30mpg car on petrol.

other, whose more the salesman, said he'd had feedback from a couple other customers saying they didnt think much of the lpg spark plugs.

seemed a bit inconclusive. as did googling info on other cars. i know conversions are popular on here, so was wondering if anyone on here had experimented with them.

came about as when i picked the car up after the conversion the fella asked when the last time they were changed as lpg needs a particularly strong spark, and it will help economy. i didnt know offhand, but when i looked in the docs they were due, so i changed them. meaning i only did one major journey with the standards, im sure i remember gettign 320miles on my odometer though. now im rarley getting 260.

This is the first time I have ever heard of having special spark plugs because of running on LPG and I have been using LPG now for the past 16 years. Mike

Marketing BS I suppose Mike - hey I bought a Flash Lube system :) I did like the LPG needs a stonger spark comment - I think that guy is missing his spark.

Bren

[Bluesman]

yeah ive had a phone chat with them but them a couple of times. (2 different lads there). the one who seems to do most of the spanner work is always mad busy so in a rush said the mileage was about right for a 30mpg car on petrol.

other, whose more the salesman, said he'd had feedback from a couple other customers saying they didnt think much of the lpg spark plugs.

seemed a bit inconclusive. as did googling info on other cars. i know conversions are popular on here, so was wondering if anyone on here had experimented with them.

came about as when i picked the car up after the conversion the fella asked when the last time they were changed as lpg needs a particularly strong spark, and it will help economy. i didnt know offhand, but when i looked in the docs they were due, so i changed them. meaning i only did one major journey with the standards, im sure i remember gettign 320miles on my odometer though. now im rarley getting 260.

This is the first time I have ever heard of having special spark plugs because of running on LPG and I have been using LPG now for the past 16 years. Mike

Marketing BS I suppose Mike - hey I bought a Flash Lube system :) I did like the LPG needs a stonger spark comment - I think that guy is missing his spark.

Bren

Hi Bren.

I have never had a Flash Lube system either and have never had a single problem. Mike

[messi]

From what the company Mint Lpg tell me only the Lexus rx need a flashlube. The Ls models dont as the valves are hard not soft.

[ManicMark]

From what the company Mint Lpg tell me only the Lexus rx need a flashlube. The Ls models dont as the valves are hard not soft.

The GS 300 needs flash lube aswell or the six cylinder 3.0 lump.

I did 60k in my 400 no flash lube my mate did 160k no problems.

[messi]

Mark

Did your ls have a flashlube?

[Bluesman]

From what the company Mint Lpg tell me only the Lexus rx need a flashlube. The Ls models dont as the valves are hard not soft.

So how does it run on modern petrol? Mike.

[RayKhan]

My GS has flash lube

[Bluesman]

Modern engines all have hardened valves and valve seats to run on non leaded petrol and running on LPG is no difference. The flash lube systems were pushed in the early days of LPG when lots of engines still hadn't been modified to run on Non leaded petrol but there is no reason for them today. Mike

[ManicMark]

Mark

Did your ls have a flashlube?

The installers insisted on fitting flash lube but when the bottle was empty I didn't refill it, as I knew the 400 didn't need it.

[John N]

My LS430 is the third car I've had converted to LPG. I was getting 20 mpg on petrol, mostly in town traffic. on LPG it has dropped to 16 mpg which is a 20% reduction, about the same as I expected, and the same as a lot of people report.

My previous car was a Merc S320 (the most unreliable car I've ever had) and I fitted it with Denso iridium spark plugs which did improve the LPG running slightly. They have a fine tip which makes it easier for the spark to form under difficult conditions.

But the Denso iridium plugs are a standard fit on the LS430 and I don't think there would be anything to gain from changing them as the car runs fine.

John N

[John N]

My LS430 is the third car I've had converted to LPG. I was getting 20 mpg on petrol, mostly in town traffic. on LPG it has dropped to 16 mpg which is a 20% reduction, about the same as I expected, and the same as a lot of people report.

My previous car was a Merc S320 (the most unreliable car I've ever had) and I fitted it with Denso Iridium spark plugs which did improve the LPG running slightly. They have a fine tip which makes it easier for the spark to form under difficult conditions.

But the Denso Iridium plugs are a standard fit on the LS430 and I don't think there would be anything to gain from changing them as the car runs fine.

John N

Forgot to mention I threw my Flash lube away as everything I've read says the LS doesn't need one, I've never had one before, and covered over 100K on LPG.

John N

[Patrykard]

Oliver, 23 mpg sounds reasonable. It's a petrol v8 and consumption will vary depending on many factors including weight of your foot, outside temperature etc. remember this is 4 litre 300bhp engine! Come on!

[brendangeorge]

Modern engines all have hardened valves and valve seats to run on non leaded petrol and running on LPG is no difference. The flash lube systems were pushed in the early days of LPG when lots of engines still hadn't been modified to run on Non leaded petrol but there is no reason for them today. Mike

I am with you on the hardened valve seats - I need to talk to my pal when he is back from the US about what happened to his 430 - I believe the problem was the valve oil seals. I saw posts from others saying they don't bother to fill up their flash lube bottle - I forget half the time as well. Like most replying to this thread I think it is probably a waste of time.

Bren

[oliver261]

all sounds normal then. cheers for all the replies.

[abs66]

Slightly off topic but having fitted iridium ngks and new ht leads which haven't cured my lpg misfire, I'm fitting new coils in the next hour or so while its not raining.

If anyone has any notes on fitting or notes of caution for that matter, I'm all ears.

Cheers me dears.

[Patrykard]

Abs, one thing to mention - have your lpg injectors and the vapourator checked. Injectors should be replaced every couple of years rgese are not too pricey. If it misfiries in cold, could be temperature trigger switch point that needs adjusting. If the installation is old, have the lpg ecu changed to some recent one with common usb interface

[abs66]

Thanks for that, I will certainly get these things re looked at by the lpg installer. He is convinced my coils are the culprits and to be fair at 15 years old and 50 quid to replace they are worth a try.

I will however not let him off the hook if there is no improvement.

[Bluesman]

Slightly off topic but having fitted iridium ngks and new ht leads which haven't cured my lpg misfire, I'm fitting new coils in the next hour or so while its not raining.

If anyone has any notes on fitting or notes of caution for that matter, I'm all ears.

Cheers me dears.

Pete, when you have the bonnet up on your car with the engine ticking over is there a ticking noise coming from the injectors, maybe one or a couple of them? Mike

[abs66]

Yes they tick. I've never heard a gas injector that didn't though. Why?

On another note. Me being the optimist thought, just unscrew those 4 screws on the coils and they will come right off..........prat !!

Screws show no sign of moving and every sign of chewing. So here I stand with new coils and no damn way to fit them! To top it all off the weather's turning nasty again!

[abs66]

Well back to trawling Google for a coil removal tutorial. There must be one some where with pictures as I suspect I will have to remove brackets and then drill out the screws if all else fails.

The driver's side (UK) seems like I might be able to remove/drill the screws in situ but the passenger side has virtually no access to two of the screws from above and I can't find a way to see what its screwed to underneath!

Very frustrating.