LPG kills Aircooled engines?

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LPG kills Aircooled engines?

Postby dugcati » 03 Jan 2010, 22:52

I had my van on the rolling road (at a renowned VW repair/tuning place) the other day and after telling him the rolling road test was to prove whether I LPG this engine or go for a 2.0L then LPG that was told by the mechanic not to bother with LPG'ing any Aircooled as after a couple of years it kills the heads/valve guilds/valves etc as they run too dry (LPG only).

This is the first time I have heard this kind of statement and was wondering on what grounds he could be basing this on - I personally have not heard of anyone having dead engines after a year or two on LPG - I'm pretty sure that Steve@Gasure would have long stopped converting Aircooled if this were true!


Can anyone come up with a reason as to why this guy was so set against LPG on Aircooled's? (the only thing I can think of is REALLY early, completely original bus/bug engines that could have issues?) :?
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Re: LPG kills Aircooled engines?

Postby kevtherev » 03 Jan 2010, 23:03

Why only Aircooled?
it's the same flat four engine which runs on unleaded as mine.. just mine has water.
unleaded fuel carries no "lubricant" (lead) for the valve seats so VW made them harder to take this lack of lubricant.

petrol is vaporised in the carburettor.. LPG is vaporised in the.. er vaporiser then sent to the carb

I think this fella has been misinformed
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Re: LPG kills Aircooled engines?

Postby dugcati » 03 Jan 2010, 23:32

Cheers Kev - that's pretty much what I thought re:unleaded - I didn't mention it to him as didn't want to come across as cocky/patronising to him

I wonder if he had to deal with a really knackered/badly set-up engine once that then dropped a valve or something and the LPG got the blame for it? :| :?
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Re: LPG kills Aircooled engines?

Postby Aidan » 04 Jan 2010, 09:46

there are some who run head lube systems on their engines and some installers insist on them for scooby wbx on lpg
there doesn't seem to be any evidence from the last five plus years of lpg installations on our engines suffering head problems, mostly they still die of seals and studs and oil pump weaknesses, well set up and in decent health they seem fine on lpg, but it does show up tired old engines quicker than petrol
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Re: LPG kills Aircooled engines?

Postby Red Westie » 04 Jan 2010, 10:19

I am wondering wether the softer valve seats on earlier air cooled heads (Pre mid 80's) when lead was taken out of forecourt petrol....has anything to do with this.
Volkswagen/Audi's of this era suffered from burning out valves until harder valve seats were fitted mid 80's onwards.

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Re: LPG kills Aircooled engines?

Postby Willoughby » 04 Jan 2010, 10:26

Onec the valves have been run on petrol they are fine to use with LPG.

After a re-build you need to run on liquid gold for a few thousand miles then it's cool to go back to LPG.

Steve will be along in a mo to put this to bed, sure his van has been on LPG for 10+ years

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Re: LPG kills Aircooled engines?

Postby tensilekid » 04 Jan 2010, 10:28

Hi,I converted a CU engine in my T2 using the oil to heat the vaporizer (no red hot exhaust near my gas!) and ran this for 5 years no problems as valve seat are hardened. The only thing was the need to warm the engine for 5 miles on petrol before changing to gas. I subsiquently changed form twin cabs to dual webber and this was a big improvment as balancing the (worn) carbs was a pain ! Also the engine oil stayed perfectly clean as LPG burns cleaner and a little hotter.

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Re: LPG kills Aircooled engines?

Postby Ian Hulley » 04 Jan 2010, 10:33

Dug, just speak to Steve Shaw. :wink:
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Re: LPG kills Aircooled engines?

Postby T'Onion » 04 Jan 2010, 11:33

Beardy Andy at the farm has been running his 2.0 A/C on LPG for years and has done 1000's of miles without problems , and I do believe that Steve runs an A/C'ed himself.
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Re: LPG kills Aircooled engines?

Postby 72BUG » 04 Jan 2010, 11:35

T'Onion wrote:Beardy Andy at the farm has been running his 2.0 A/C on LPG for years and has done 1000's of miles without problems , and I do believe that Steve runs an A/C'ed himself.

Indeed he does, and I believe it's done over 300,000 miles, much of which has been on gas. :ok
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Re: LPG kills Aircooled engines?

Postby silverbullet » 04 Jan 2010, 13:22

Aidan wrote:there are some who run head lube systems on their engines and some installers insist on them for scooby wbx on lpg
there doesn't seem to be any evidence from the last five plus years of lpg installations on our engines suffering head problems, mostly they still die of seals and studs and oil pump weaknesses, well set up and in decent health they seem fine on lpg, but it does show up tired old engines quicker than petrol

My local engine shop (with whom I regularly exchange work on a mutual basis) tell me that they see a lot of recent engines that have eaten their valve seats on modern LPG conversions. Maybe this is a symptom of botched cheapo installations, I don't know.
They also say that recently, OEM cylinder heads have been coming in fitted with very hard seat inserts (both mechanically as well as chemically hard) which give them untold greif 'cos they are so difficult to re-cut or grind. This is probably to counter the seat erosion problems that still seem to exist around LPG and it's use on the contintent. Maybe. Subarus do have comparatively "soft" seats when compared to others, it turns out.
The whole "if it's been run on leaded in the past its ok/lead memory" argument is a bit flawed. The lead bromide that used to be added to petrol as a detonation (pinking) supressant to allow higher compression ratios will protect the seats in the head for a while, but not that long. It will wear off.
Unleaded fuels have different chemicals (so-called lubricants) added to prevent the micro-spot welding of the valve seat faces, which cause the erosion problems which are seen most dramatically with iron head without seat inserts.
Which brings me to my point - do these valve lubrication systems for LPG conversions perform the same task as putting sodium/potassium additives in the petrol tank in the case of changing from 4* to unleaded? If they do, then fair enough. But why not just put some additive in the petrol tank that you've already got and each start-up will deliver the stuff before it switches to gas. You've got to deliver the protection to the valve seat somehow and it doesn't seem to be present (or possible) in Autogas.
Which burns slightly cooler than petrol, not hotter btw. Lower calorific value, lower volatility - why gas will stand more ignition advance than petrol. It burns slower. Not much, but enough to need a change in the timing which will also burn the seats out when on petrol and higher engine loads...
Sorry to go on, but there is a lot of flannel talked about what goes on in an engine and folks still don't seem to have grasped the half of it when it comes to fuel. Or am I getting something wrong?
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Re: LPG kills Aircooled engines?

Postby steve8090 » 04 Jan 2010, 13:33

Yes I converted Andy's Aircooled many years ago and he has never had any problems and as stated mine has done over 300,000 miles 2/3rds of that on lpg with out any problems, I have of course rebuilt the motor once in that period but you'd have to do that anyway and I know how to look after it too.
As for softer seats of the early 80's all of the vehicles had hardened valve seats from the early 70's onwards, bay, beetle etc and I've converted loads of these, if you are worried about the extra heat in the engine then have a flashlube system fitted, this lubricates the upper cylinders and takes the place of the liquid fuel. The flashlube system is fitted as standard onto anything japanese, american, . . or vauxhall because of inferior materials used in the engines compared to german and swedish engineered engines.
On the other hand and it is not just the Aircooled that burn out valves, if the vehicle is not in top condition, well serviced (and I don't mean plugs, air filter and oil changes every so often) I mean properly serviced by a decent garage that can foresee any problems and setup mixtures, balance carbs and have the correct diagnostic equipment then yes you will burn out any engine. LPG runs at a higher combustion temperature and if for instance the bottom tins have been removed from an Aircooled vehicle it cannot remove the heat efficiently and valve seat recession will occur, I can advise on that when I inspect your vehicle, similarly the water boxers, if they are not serviced correctly and have a tight valve or air leak at the manifold or tend to run weak because the mixtures have not been checked annually then yes it will burn out, but this applies to any engine.
Just a little more care and attention to the servicing needs of your vehicle will make it last many many years, mine is 30 years old this year and I cannot foresee it ever leaving me or scrapped, if you are in doubt please talk it through with your chosen installer first and of course I would be more than happy to answer any questions.
Sorry but some people talk a right load of crap about these conversions and it is pure ignorance more than anything, petrol or lpg if an air cooled does not have its tinware and is running weak then you will get valve seat recession, japanese motors do have hardened seat but the valves are crap so they stretch due to the extra heat, same with f.o.rds, vauxhalls are just crap material they just burn (and deservidely so :) ) so yes we are aware of the higher combustion temeperatures and now you are and you know now what to do about it, the flashlube system is the only system that puts the correct additive into the inlet tract, we also use the flashlube on non-unleaded engines so they can use unleaded fuel.
LPG is the only current modification you can do to your petrol engine to decrease its environmental impact dramatically, the only system that will pay for itself in an average years motoring and provide you with genuine fule saving thereafter, the only downside is tank location and the need to have the vehicle serviced correclty.

Edited for spelling
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Re: LPG kills Aircooled engines?

Postby silverbullet » 04 Jan 2010, 14:26

silverbullet wrote:Or am I getting something wrong?

Looks like I was wrong!
steve8090 wrote:The flashlube system is fitted as standard onto anything japanese, american, . . or vauxhall because of inferior materials used in the engines compared to german and swedish engineered engines.
LPG runs at a higher combustion temperature
Sorry but some people talk a right load of crap about these conversions and it is pure ignorance more than anything, petrol or lpg if an air cooled does not have its tinware and is running weak then you will get valve seat recession, japanese motors do have hardened seat but the valves are crap so they stretch due to the extra heat, same with f.o.rds, vauxhalls are just crap material they just burn (and deservidely so :) ) so yes we are aware of the higher combustion temeperatures and now you are and you know now what to do about it, the flashlube system is the only system that puts the correct additive into the inlet tract, we also use the flashlube on non-unleaded engines so they can use unleaded fuel.
LPG is the only current modification you can do to your petrol engine to decrease its environmental impact dramatically, the only system that will pay for itself in an average years motoring and provide you with genuine fule saving thereafter, the only downside is tank location and the need to have the vehicle serviced correclty.

Edited for spelling
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Re: LPG kills Aircooled engines?

Postby dugcati » 04 Jan 2010, 21:48

This is ace folks :ok You are all confirming much of what I either knew or suspected with regard to engines not dying on LPG - as I said I'm sure Steve et al would have stopped converting years ago if there were any problems with it.

I still suspect he had to deal with a few engines that were knackered and on LPG so that got the blame :wink:
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