My P38 early on in its life had a single point LPG system fitted, according to one of the previous owners it used to backfire through the manifold and ruin the MAFS

I have an intake pipe that has been blown apart, which is odd.

My question is, can you make a Thor V8 run on a single point system?
It ran ok sometimes but not always. Allegedly.

She now has a multipoint system on her.

My other question is.

Is it right for an 84 litre tank to give only 150mi range?

Surely i should be able to get more?

Cheers gents.

I've got a 95 litre tank which used to click off at 80 litres from dead empty. Worryingly, it no longer clicks off but I stick about 80 litres in when I get down to empty and it's fine. Anyway, with a rather tired GEMS with single-point I'm getting roughly 200-240 miles to a tank, although today I got well over 280 miles. Must be magic gas or something, I was genuinely wondering WTF the engine was running on by that point.

An 84 litre tank ought to hold 70 litres, give or take, so for the same sort of fuel consumption that mine's got I'd expect about 175 miles or so.

Back in the days when LPG parts were much more expensive, if someone wanted a P38 converting installers would usually quote for both a single point system and at higher price a sequential system.

The advantages of the single point system were less expense for parts and less expense for fitting, engine can start from cold on LPG. Advantages of a sequential system are switching fuels automatically, supposedly a bit more power and fuel economy, no chance of a backfire.

The number of parts to convert any engine using a single point is similar regardless of number of engine cylinders (ok might need an extra emulator with more cylinders costing maybe £30 back then). Used to be that single point systems cost less than parts to convert a 4 cylinder engine using a sequential system, while parts to convert a V8 using a sequential system used to cost about £500 more than parts to convert a 4 cyl using a sequential system.

Would think whether or not fuel economy/range is correct depends on the type of driving you do and how mpg on LPG compares to mpg on petrol.

My tank takes 65 litres to fill and I get anything between 180 (around town) and 220 (long run) miles out of a full tank. You'll use more if you are constantly stopping and starting as you need to use a lot more fuel to get 2.3 tonnes of car moving than you do in keeping it moving.

As for singlepoint on a Thor, I wouldn't consider it. I'm running a singlepoint on a GEMS but the Thor has a much larger volume inlet manifold so a lot more gas/air mixture to go bang in the event of a misfire. I've had a couple of pops, mainly due to iffy ignition (one was caused by me not putting a plug lead back on properly) and the worst I've seen is the mesh grille in the MAF getting blown off and ending up in the air filter box. However, on a Thor, the bang will be bigger and the MAF is a lot more expensive so not worth risking it.

A question about the mesh grille, are they available anywhere? Mine is torn. How important is it that it's intact?

I don't think it is that important, the car still ran perfectly OK with it completely missing. As it's part of the MAF housing, it can't be bought separately.

When I drove her it was mainly M5 motorway work.

The LPG system has packed up now.

Needs some work.

Her MAF is in need of a replacement.

The PO said it backfired so bad it blew the intake trunk apart and took the centre out of the MAF lol

A Thor will do when running a singlepoint, there's a hell of a lot of gas to explode. Much like when people tried to put a singlepoint on the Ford Explorer. 3 litre V6 engine with a plastic inlet manifold. One little misfire and the entire manifold became little bits of plastic spread around the engine bay, it would literally blow it to pieces.

If your MAF needs replacing, the mixture on petrol will be wrong, probably going into a fail safe rich mixture, which will make the mixture on LPG rich too.

Thanks.

I think she needs a few new things!

Thanks for the answer on the mesh grille. I should probably tear it out completely so I don't ingest it someday.

Probably a good idea, it could cause you a bit of a problem when it tries to find it's way past the throttle butterfly......

I'd give Gilbert's posts above on this thread a like if this forum featured a like button, agreed.

What's wrong with your LPG system Strangerover? One I fitted?

Hiya LPGC it was installed by a place called Profess Autogas, based in Hengoed (15 miles north of Cardiff).

The indicator just flashes on the dash.
I ran it to empty once and it never worked again!

I used to hear an audible click from the tank when it switched over, doesn't do that anymore. Lol.

It has £30 of Gas in it which is annoying lol

StrangeRover wrote:

it was installed by a place called Profess Autogas

Now there's a name that used to be slagged off regularly on the LPGForum. Not surprised it doesn't run right, probably never has.

Ahh.

Right.

So they're carp?

It is an AC Stag system. Apparently. Lol

Yup, that's all they ever fitted, whether it was suitable for the car or not. They were what became known as one of the done in a day merchants. Fit a system in a day, don't bother to set it up and when the customer complains that it is down on power/MIL keeps coming on/doesn't give the economy expected, he gets told that it is perfectly normal for an LPG conversion (which it isn't).

Throttle response was carp MPG was pitiful. And tbh on petrol it was a different engine lol.

So the reputation holds true lol.

I bet the injector nozzles are in the upper inlet manifold and not down near the petrol injectors like they should be. That'll give you poor throttle response.

Profess try to get owners to buy an interface cable for the LPG software from them, they're told that the LPG system can be serviced remotely using a special facility of Stag software which allows Profess to diagnose and calibrate the system remotely. The 'special' facility is just Windows remote desktop access which any installer could use to diagnose/calibrate any LPG system remotely... But a better idea is to fit the system so it won't break and calibrate it properly so it will run properly without needing 'tweeks', not by a visit to the installer and not by using remote desktop access.

Profess may have set the service interval facility in Stag settings to disable the LPG system (won't switch to gas) if you haven't had it 'remotely serviced' by them within a set number of hours of the engine running. If they didn't set the service interval thing there must be a problem, perhaps just a solenoid / sensor / etc. The fix shouldn't take much doing regardless, but like Gilbert says Profess aren't noted for great installs.

That is interesting.
Thanks both.

The LPG system just quit, no real reason so it's possible it is service related.
Rather odd.

I should note the injectors are in the upper part of the manifold, nowhere near the injectors.

And throttle response was pants above 4k on gas the engine struggled it felt like it had 1/2 the power, on Pez it pulled like a train.

Range as I said above was 150 which was a best for me.
90mi was the worst, lol.

The system if from 2013 so not that old.

I think she's had LPG since new.
Not entirely sure though.

Is it possible to find out when she was registered as a dual fuel?

Cheers

H

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