M40 LPG Conversion

[Partridge]

Time for my contribution to the zone. I’ve read plenty on here about LPG conversions and know there’s no guide yet of what to do. Here goes.

Car is a 1992 M40B18 Auto, converted for me from an M20B20 (the M40 suits the auto far better than the M20). Owner is an enthusiastic amateur mechanic, whose ambition knows no limits.

I want this finished before we use the car for a trip to France in mid August. I chose the LPG shop for the parts, mainly because they are near to home. On email before my visit, they confirmed they had a single point system available http://www.lpgshop.co.uk/aeb175-leonard ... ambda-ecu/ , as Brian recommends, but asked why I wanted a single point, when the car was running multi point petrol? I deferred to their knowledge and came away with an LPG Tech Tech One system, which their software lists for the M40.

I came home with this lot, plus a toroidal tank. The multivalve (tank outlet) and filling kit were out of stock and are arriving in the post. I intended to fit a lambda sensor, but Greg tells me it’s not necessary, this kit uses the signals to the original injectors to decide the gas output.




Very pleased with the quality of the parts, even if I do need to figure out what goes where myself. There are six different types of hose included, but it’s obvious what each is for. Instructions are basic, but only leave a couple of questions to be answered.




First job is to decide where the main components will be fitted. Initial thoughts are ECU in the car, near the original. Injectors, filter and sensor on the panel at the back of the engine bay that covers the heater. That leaves the reducer, which needs two water pipes, a high and low pressure gas connection and two sets of electrical connections. It’s not small.




It’s either under the servo, near the AFM on the redundant M20 relay mount, or behind the headlights. First one has to be the favourite, it’ll be a bugger to fit and make the connections down there, but that’s where the coolant hoses are and the finished job will be much neater.

All opinions valued ”“ particularly with component location.

[DanThe]

I would always fit the reducer where its accessible and in sight, its always the main culprit for leaks of gas or coolant, make it a git to get at and you will kick yourself further down the line

In your situation I would probably relocate the PAS reservoir lower down and fit it there

If the system can make use of a lambda sensor, then definitely fit one, it will run a hell of a lot better

[Partridge]

Thanks Dan, makes sense. I read through the set up guide on LPG Tech's website yesterday and it did occur a lambda would make it a whole lot easier.

She's away in the car this weekend, so no progress expected until next week.

[DanThe]

Still racing?

[Partridge]

Back again. Failure on the modern car stole my conversion time. Now back to it and would have finished but for.....

Year out from racing Dan - too many projects

[Partridge]

OK, thanks for your comments on the reducer location. Naturally, I ignored them.... but only because there are two lovely captive nuts in the suspension tower in just the right place. There's a bracket supplied with it, drilled one hole to align it neatly and a slight twist;



Fits well there, plenty of room and good access once the filter and AFM are out of the way. I thought I would have to move the PAS reservoir, but a slight twist and back it went. I'd prefer to remake the pipes a little longer, but that's for another day.

Next I ran the pipe from front to rear. Followed the fuel line, 'P' clips were supplied with the kit, originally tried to screw these under the plastic petrol pipe clips, but not enough room, so they're held in by the Phillips screws on the fuel and brake line holders. Tied the two wires (solenoid and level sender) to the pipe.

Then the tank went in. Not a nice day, don't like cutting holes in her The multivalve was a pain, tight to insert into the tank and not much room to make the connections. Torqued it down carefully, don't often use a torque wrench away from the engine, but guess this bit was important.

Now for the real fun, drilling the manifold for the nozzles. This was my first attempt.

[Partridge]

Unfortunately, although there is enough room there, the angles were wrong and the centre two foul the throttle position sensor. Quick Ebay purchase, thanks Platinum Auto Spares and attempt number two -



Having now connected the nozzles to the injectors, I'd like to have a third go and put the nozzles for 1 and 4 on the inside of the intakes, this will allow shorter pipes.

Borrowed a Dremel to grind down the nozzles, what a great device!



Next was the injectors. Their position is dictated by the nozzles, I have them on a grotty bracket bolted to the manifold support, but hope to redo once the third edition manifold is done

[Partridge]

Now the electrics. Taking interiors apart is not my favourite job, but has to be done. I taped the ECU to the heater, ran the engine speed wire, permanent live and switched live to the right, the first two into the engine bay on that side, engine speed wire going to the coil. LPG Tech have subsequently informed me they prefer the crank position sensor, but it'll stay on the coil for now.

Mounted the switch on a blank above the radio (more Dremmeling ) and ran all the other wires into the left hand side of the engine bay.

Two wires go to the solenoid on the reducer and then onto the tank, three to the level sensor, two to the reducer temperature sensor, then two large wires with pre-fitted connectors, to the gas pressure sensor and the gas injectors. Just the petrol injectors to do.

OK, we're nearly there. Last weekend I had a shitty time plumbing the reducer into the coolant circuit. I assumed the flow was from the plastic pipe out of the block, so cut the pipe to the radiator tank on one side and fed back into the heater outlet. I guess there is no flow through the heater matrix when the heater is on cold, so the heater pipes are no good?

Last but one, the low pressure gas pipe, struggled to make this neat, so is another 'work in progress' although I haven't had a better idea yet.

Finally, cut the loom

First issue, I have eight wires to connect into the injector wiring, which only has three wires.
Email to Poland, I know now Motronic is semi sequential, so connections for 1 and 3, 2 and 4 are joined. Negative for BMW here, why are the bloody injection wires in the loom all black After much checking, selected the correct two in the main loom by the bulkhead and cut them.

Oh, forgot one bit - the filler. Getting excited now, so I made a bracket to fit under the rear bumper bolt and hung it there. I was going to cut the bodywork, but I'd really rather not....other location suggestions gratefully received.

[Partridge]

Right, we're ready to go.

Fire up - runs on two, big problem. I've traced it now, there's a short in the LPG loom and two injectors are open circuit. I have excellent cooperation from LPG Shop in Leicester and LPG Tech in Poland, but there's no spares until Wednesday, so I'm dead in the water. I've filled the tank, that's fun (and cheap, 0.549 at my local BP), but I'm waiting for a replacement loom and ECU.

Hopefully back Wednesday. 2,000 miles to do next week, so it better arrive

To fill my time, I decided to connect up the cruise control that's been dormant since the M20 was removed. Where's that bloody green plug.......

[Sanchez]

Sounds cool. I just done 1100miles from Edinburgh and into France the other week and returned 33 mpg average for the whole trip. M20b25.

[Brianmoooore]

I assumed the flow was from the plastic pipe out of the block, so cut the pipe to the radiator tank on one side and fed back into the heater outlet. I guess there is no flow through the heater matrix when the heater is on cold, so the heater pipes are no good?

There's a 7.5A fuse fitted an inline fuseholder near the LH side of the heater box (follow the wire from the electric valve). Pull this fuse out, and the coolant will flow permanently through your heater matrix (and vaporiser).
If you find that the heater output on full cold is sufficiently cold, then this arrangement can be permanent.

I was going to cut the bodywork, but I'd really rather not....other location suggestions gratefully received.

Still cutting bodywork, but on a saloon or cab., you can fit a filler behind the rear numberplate. Cut a bigger hole in the plastic surround, and the number plate can be refitted flush, on hinges with a magnetic catch, solely by magnets, or even by velcro.
With the filler completely hidden, you can even use the tunnel to cross the channel.

[Partridge]

Back again,

Thanks for tips above Brian.

All is working well - with the LPG. My holidays in France were interrupted by this irritation



Just crossed the Millau bridge, I credit the LPG conversion with saving my cylinder head. The 'beep' on switching from gas to petrol (I assume as the water temp exceeded parameters) caused me to scan the dash and see the temp off the scale and charging light on. Be very grateful we're English and have ECP. Don't need parts in a hurry in France.

Anyway, new pump fitted. Running at a true 80mph returned 27 mpg. Bringing the speed down lifts the consumption to 30. I have a local BP that sells at 50 pence, with a discount card reducing each fill by a penny until down to 40p. Proper man maths calculates the running costs are the equivalent of over 70mpg on petrol, removing the biggest complaint with running an E30. Interesting that a 2.5 uses less, I must work mine hard.

This job hasn't been easy, there was a significant problem upon installation which was traced to faulty components.

However, it runs at least as well on gas. In the current weather it switches over within a mile of a cold start. There's a couple of issues I still need to iron out, just waiting for some spare time.....

[Brianmoooore]

Congratulations, and welcome to the world of truly economical and green motoring. There aren't many, if any, non hybrid cars out there, that can do a genuine 70 MPG on petrol!
The switch over from gas to petrol that alerted you would have been caused by lack of gas pressure from the reducer as the reducer became encased in ice as a result of insufficient heating from the reduced flow of coolant. I have experienced this myself recently (just two days before I went to France!), when the top hose connection of my E39's radiator decided to crack.

[Webby0121]

Brilliant guide! Im intreasted on LPG converting so ive been reading up and this is fantastic.
How much did it all cost in the end?
And where from?

Thanks

[Partridge]

All came from LPG Shop in Leicester. Total was about £350. It ran perfectly for a year (around 15K miles) but the ECU appears to have failed. I've had lots of contact with LPGTech in Poland, who have been excellent, although my current issue is perplexing them....

[miniblob]

So circa £350 for parts... anyone on here fit lpg for zoners?
Anyone have an idea what sort of cost would be involved with having this fitted somewhere???

(Sorry for being lazy, I need to look into this properly one day - gotta be a better idea than buying something crap just to save money on fuel!!!)

[Webby0121]

All came from LPG Shop in Leicester. Total was about £350. It ran perfectly for a year (around 15K miles) but the ECU appears to have failed. I've had lots of contact with LPGTech in Poland, who have been excellent, although my current issue is perplexing them....

Fantastic, what was the shop called?

And how did you calculate the nozzel angle?

Thanks