LPG Conversions

[andyborris]

I have only a limited understanding of LPG conversions for carb'ed engines and as I'm toying with the idea of buying a very thirsty car (16 mpg!!), that uses Stromberg CD carburetors, I'm wondering if this might be a solution?


So, how does a conversion work, pros and cons, best type of system, etc. please.


Thanks.

[ChasR]

Plenty of pros and cons. I would go into detail, but this will cover it for now.

Pros:
-Cheap
-Oil life improved

Cons:
-Valve seats, even on unleaded cars can take a beating due to hotter temperatures and less lubrication from LPG that petrol provides
-Most 'certified' conversions IME aren't worth the paper they are written on.
-IME the stations are now disappearing ; I've lost two in my area
-If you give your car to a garage, they are more likely to break things on the LPG side than if it were a normal car. Most kits are generic items and really need to be installed in certain ways to make them work well, despite what others say.
-Going 'cheap' on an LPG system isn't the best way, but you can be reasonable. For example, some tanks can take over 10 minutes to fill (no joke!). With the right valve, a decent take can take less than 3 minutes

I've had 3 cars on LPG now, maybe more, and have converted more than that : my dad and I used to convert them for a living, and deal with other people's issues

How many miles will you do and what car is it? It may devalue it and not be worth the hassle from the above.

[stealthstylz]

I was quite "pro" LPG till I started building engines and saw how many came through the door needing repair. If it was just some throwaway banger I'd use it but on something nice it's not worth the cost of conversion + engine repair costs.

[kevins]

I've got 2 cars on LPG, a tr7V8 on su's and a range rover classic on flapper efi. The range rover was converted when I bought it but I had to sort out several issues and replace the vaporizer which was way to small, it now performs very well doing around 14mpg comparred to 16 on petrol.

I converted the TR 20 odd years ago, starting takes a few cranks on LPG, but otherwise it works well, both use omvl r90e vaporisers and Blos variable mixers.

The biggest issue is if you can get LPG, I drive past a shell station which sells it every day but if this closes the nearest is 15 miles away so it wouldn't be viable.

[bmw2101]

My mate has run is cars on it for the last 15 years, loves the stuff..

His current car is a home build 1700 turbo engine using megasquirt.


So my advice is to build a LPG Lada turbo, and move to Bulgaria!!!

[comfortablynumb]

IME the hassle involved makes the return not worth the effort. Had a V8 rrc on a Weber, never ran properly, I fitted the kit myself, and then when I couldn't get it to run right I went back to the supplier, only to find that having fitted the kit I knew more about it than he did!
A mate has a 110 landy with 4.6 v8 on injection with£2000 worth of LPG, when it runs it's fine, but sometimes it won't run on it at all, on a recent trip to France he put it on the ferry (apparently LPG isn't allowed on the tunnel?) And when he got in it in France to drive it off the ferry it wouldn't start on LPG. He spent the whole week driving on petrol, every time he switched to LPG it died. Put it on the ferry home, gets into it in Dover, it starts straight up on LPG!
It just doesn't like France! The fitters have tried to sort it, but every Time he gets it to them it won't show a fault.

[rallyboy]

The biggest issue is availability in your area. Some areas are well served, some not at all.
Can't comment on the carb side as my Octavia is injection but I love it 'cos it's so cheap to run - had a BRC kit fitted 11 years ago at 55,000 miles with Flashlube kit to ensure no valve seat problems (for the money, why wouldn't you fit one) - it's now done 252,000 miles - the only issues have been a failed temperature sensor and a loose wire.

Yes, LPG not allowed on the tunnel - apparently because they forgot to put it on their insurance form when they started up and can't be bothered to change it.

[comfortablynumb]

Aug 9, 2019 7:44:55 GMT rallyboy said:

Yes, LPG not allowed on the tunnel - apparently because they forgot to put it on their insurance form when they started up and can't be bothered to change it.

Seems absolutely ludicrous to me, you can't have a properly fitted tank, but an old gas bottle rattling around in the front of a fibreglass caravan is fine......😬

[kevins]

Forgot to add on carb engine the change from petrol to gas is a bit of a fiddle as well, you have to switch it to the centre position which turns both fuels off and wait until the petrol in the float chamber runs out (which can be a mile or 2) then flick it to gas after which it will run lumpy for a few seconds until the remaining petrol has completely gone, going the other way is not too bad as it only takes a few seconds to fill the float chamber.

In all but the coldest days Mine starts Ok on LPG anyway, as my mixer is a long way downstream from the carb it takes a few seconds of cranking so a decent battery is needed but it then goes fine.

[rallyboy]

Aug 9, 2019 8:08:18 GMT comfortablynumb said:

Aug 9, 2019 7:44:55 GMT rallyboy said:

Yes, LPG not allowed on the tunnel - apparently because they forgot to put it on their insurance form when they started up and can't be bothered to change it.

Seems absolutely ludicrous to me, you can't have a properly fitted tank, but an old gas bottle rattling around in the front of a fibreglass caravan is fine......😬

If you think about it, it's worse than that - you can't have a proper (certified) LPG tank but you can have a completely uncertified & not built to any recognised standards petrol tank you fabricated in the shed at the bottom of the garden.

[comfortablynumb]

Yeah absolutely mad, the mate I referred to with the 110 thought his LPG tanks looked a bit rusty, system has been fitted for almost 10 years, so he thought he'd better get them checked.
Apparently tanks are supposed to be retested every 10 years anyway, but when he looked for someone to do the test the response he got was ' don't know about that, we've never done one!'

[ChasR]

Aug 9, 2019 8:08:18 GMT comfortablynumb said:

Aug 9, 2019 7:44:55 GMT rallyboy said:

Yes, LPG not allowed on the tunnel - apparently because they forgot to put it on their insurance form when they started up and can't be bothered to change it.

Seems absolutely ludicrous to me, you can't have a properly fitted tank, but an old gas bottle rattling around in the front of a fibreglass caravan is fine......😬

Aug 9, 2019 17:16:41 GMT rallyboy said:

Aug 9, 2019 8:08:18 GMT comfortablynumb said:

Seems absolutely ludicrous to me, you can't have a properly fitted tank, but an old gas bottle rattling around in the front of a fibreglass caravan is fine......😬

If you think about it, it's worse than that - you can't have a proper (certified) LPG tank but you can have a completely uncertified & not built to any recognised standards petrol tank you fabricated in the shed at the bottom of the garden.

Well, yes and no .

The tanks are certified, yes. But think of this another way. the valves on them aren't and neither is the installation of a valve onto them. Any monkey including either you ore me could put a crappy valve on and get it to work. At least with the Calor barbeque tanks, they are certified, and installed by trained personel at Calor Centres (I should know, I used to work there). Also, you generally exchange Calor cylinders or FloGas items, so again, there is a form of monitoring.

And as I said before, the certificates for the conversions aren't worth the paper they are written on. I've had to solve quite a few certified setups, and some 'home ones' where 'certified fitters' tried to take them to the cleaners. I've also come across some pretty dangerous conversions, and that's from a certain bloke (who I won't name) that goes on a number of Facebook groups that really should know better.

[stealthstylz]

I think the difference is a LPG tank is tested to hold pressure whereas a petrol tank isn't.

[dodgerover]

Aug 9, 2019 17:21:55 GMT comfortablynumb said:

Yeah absolutely mad, the mate I referred to with the 110 thought his LPG tanks looked a bit rusty, system has been fitted for almost 10 years, so he thought he'd better get them checked.
Apparently tanks are supposed to be retested every 10 years anyway, but when he looked for someone to do the test the response he got was ' don't know about that, we've never done one!'

That's changed as there was nowhere in the UK that could recertify them! It's just a visual check now, sensibly with underslung tanks you should regularly check the mountings.
We are still running one vehicle with an ullage valve rather than the 80% full cut off, that tank is coming up to 30 years out of test!!!

I love LPG, other halfs Lexus is coming up to 225k of which 125k had been done on lpg, we have had zero issues with it.
My transit has now done about 40k on lpg now, I had to get hardened valve seats fitted to the old pinto but other than that the issues have been down to me getting it set up correctly. MPG is 16 on lpg or 18(best) on petrol.
Lpg got a bad name early on with fly by night converters chucking on any old gear, the defender above obviously need to go back to an installer who knows what they are doing!

[comfortablynumb]

^^^I think the defender owner has fitted new tanks now, mainly for his own peace of mind, who wants to drive a potential bomb?
Biggest problem with the installation is that every time he gets it to the installer, the fault has 'cured' itself, and with all the will in the world, who can cure a problem that isn't there?

[dodgerover]

Aug 12, 2019 5:56:16 GMT comfortablynumb said:

^^^I think the defender owner has fitted new tanks now, mainly for his own peace of mind, who wants to drive a potential bomb?
Biggest problem with the installation is that every time he gets it to the installer, the fault has 'cured' itself, and with all the will in the world, who can cure a problem that isn't there?

I've never seen a tank yet that looks weakened by rust they are very thick but I get what you are saying, the straps usually go way before!

I think the bomb thing is very misleading and again from the early days of lpg misinformation - the explosions you can see on YouTube are as far as I am aware caused by deliberately stopping the tanks venting in a controlled fashion in the event of a fire.
lpg is heavier than air so if it does leak it will fall to the ground so not so much of an explosion risk. I have read a post about a transit being driven into a building with a massive lpg leak at a flo gas depot, such a big leak it stopped the engine but it didn't go up and the driver got out (and ran quickly I imagine).

With that defender the installer I know would have had it back and run it until the problem occurred when it could be diagnosed.

[comfortablynumb]

Having seen a diving cylinder explode without any combustion I'd stand by my bomb statement, ANY pressure vessel can explode.
Your testing suggestions is fine in an ideal world, but having worked in the motor industry for many years, the workshops I have found that would keep a vehicle on site until an unknown fault reappears I could count on the fingers of one foot, not to mention the fact that most customers want their vehicle back yesterday, if not sooner.
Still, each to their own eh?

[kevins]

A diving cylinder is around 3000psi and a propane 300psi so quite difference, Ive never heard of a propane car exploding, has this ever happened?

[dodgerover]

Aug 12, 2019 20:53:58 GMT kevins said:

A diving cylinder is around 3000psi and a propane 300psi so quite difference, Ive never heard of a propane car exploding, has this ever happened?

Only when people have done it deliberately or tried filling an LPG cylinder with CNG as far as I know.

Aus has a much higher % of lpg vehicles including pretty much every taxi, you don't get this fear of lpg there.

Set a cylinder on fire and a lead plug melts venting the gas in a spectacular jet of fire. Myth busters did a show trying to get them to explode too, I think they managed to do it in the end with armour piercing and incendiary rounds.

[comfortablynumb]

I don't think it's fear, the publicity for LPG and conversion thereof is practically non-existant, I expect the average man on the Clapham omnibus hasn't even heard of it, maybe aus is just better at advertising it, or maybe the environmental benefits (allegedly) are outweighed by the profits to be made from the tax on regular fuels, cynical I know, I have also seen a sewage tanker split, and they only run at about 20psi, it's not pleasant in any respect, and I'm glad I was some distance away when it happened.
Myth busters is a great program, but even they will admit their ' failure by any means' approach