Fitting LPG to an M20b20?

[320Touring]

Way back in the mists of time, I aquired an LPG kit off of Ziggy on here..

Fast forward a few years, and I'm back to using the 320i as a daily driver- doing a minimum of 1250 miles a month . The car is a 1988 320i touring, with stock engine.

As such, LPG is looking like the way to beat the rising costs of fuel

However, I'm clueless as to what kit I have, what else I'll need, and where everything mounts (the AFM and TB mounted plate seem obvious!)

I've got pics of everything I have, so could you folks running LPG give me an idea of what, where and why?

Thanks


Neil

[Ilkorin]

Right, quick overview then:

What you have is most of the kit (although I can't see an ECU or control valves/stepper motors).

Tank (pics 1&2) has a mutivalve (pic2) with a filler (pic3) input and LPG output. The liquid LPG from the tank goes from this multivalve LPG output along a copper line to the engine bay, where it goes through another valve and into the vapouriser(pic4). This should have a coolant in/out which needs to be connected to the engine cooling system. From the vapouriser, the liquid LPG coming from the tank expands and turns into a gas which comes out of the vapouriser and to the mixer plate (pic5) via a stepper motor (for control). That mixer plate should be installed in your airbox or in the path of airflow. Here's pics of my old airbox assembly:





For these mixer systems, you need a backfire flap (pics 7,8,9) so if/when the LPG in the intake catches light, the pressure wave doesn't get to the AFM and cause damage.

The vapouriser, stepper and valves should be controlled with an LPG ECU of some sort, so i'd be interested to see what electronics you have with this kit... Also the tank is quite old (green) so if you want it certified you may need to find a new one. Apart from that, some copper lines, fittings, LPG hose and you've got a pretty complete kit.

[Brianmoooore]

Pic 5 shows the mixer plate. Mount this on the inlet side of your AFM, preferably inside the top of the filter box, with the gas pipe coming out through the side, although the angled pipe shown on yours won't be ideal for this. Alternatively, mount it between the box and the AFM, although this makes the assembly longer.
Pics 7 and 8 are an AFM with 'cat flap' backfire valve attached. This goes where it is shown. Either use the AFM in the pic if it's the correct one and good, or detach it (three grub screws) and fix it to you existing AFM, with some sealant to prevent air leaks.
In the event of a backfire (inlet plenum full of gas mixture instead of just fresh air), the flap protects the AFM door and the explosion dissipates past the large rubber band.
The convoluted air hose to the throttle body fixes on to the outlet side of the flap (leave the hose clips a little slack as added backfire protection), and the air filter mounts will need a little modding, since the box will be pushed forwards.
Pic. 4 is the reducer or vaporiser, with a filter attached directly to it. This receives liquid propane direct from the tank at high pressure, at converts it to a low pressure gas, which feeds via a large rubber (LPG resistant) hose to the mixer.
It requires a considerable amount of heat to vaporise the liquid propane, and this is provided by two 16mm hoses from it which are normally connected by 16mm tee pieces into the heater hoses. Cut into the middle of the hose from the back of the head to the bottom heater stub on the bulkhead, and into the heater connection of the 'tee' hose right beside it. Alternatively, you can disconnect the electric heater valve, so that the heater flow never turns off, and connect the vaporiser in series with the top heater stub and the 'tee' hose.
The vaporiser should be mounted (usually low down on the LH side of the engine bay) so that the axis of the large round part (the vaporiser diaphragm) is across the car, not fore and aft.
You have two tanks shown in pic.1, both of which are more than ten years old, (colour changed to black in 2000, IIRC) and no longer certified, but I wouldn't worry too much about that.
The round one is designed to go into the spare wheel well, and the cylindrical one is best suited to a saloon boot. This particular toroidal tank will need a hole cut in the side of the wheel well, to allow the multivalve to protrude through.
No part of any gas pipe or fitting is allowed inside the car without being vented downwards to the outside air. This will all be outside anyway with this toroid, but the cylinder needs the airtight box around the valve, and all the 32mm ducting to enclose the pipes and wires going between the filler and the tank and the front of the car.
The black plastic bit in pic.6 is for fitting to through the boot floor to vent a 32mm pipe downwards.
Pic. 3 is a recessed filler point to connect to the gas pump at a gas station. This can be fitted anywhere to the exterior of the vehicle, within the plan view of the vehicle, as long as it is more than 200mm from the exhaust. (This applies to all parts of the system carrying gas.)
Popular places to fit the filler are in the RH boot compartment on a touring, on a towbar, somewhere in the rear bumper, or behind a hinged rear numberplate on a saloon. On a touring, the filler sits neatly behind the petrol filler, if you remove the locking motor for the flap and cut a hole there. A bracket can be fitted from the seam between the two halves of the inner wheel arch to the rear of the filler to stop the panel flexing under the weight of a UK filler nozzle.
In all cases, if the rear of the filler is inside the car or boot, it needs to be enclosed in an airtight boot, and then the filler pipe fed inside a 32mm vent hose, either downwards and out under the car, or two the airtight box on the tank, which is then vented to underneath by a a second 32mm pipe from the box.
The filler pipe is either 8mm copper, or a suitable high pressure flexible hose, depending on the fitting on the back of your filler.
There also needs to be some kind of adjustable valve fitted near to the mixer, in the rubber gas hose. This is just a simple screw valve in basic systems, which it looks like you have, or an electric stepper motor in systems which use a lambda sensor in the exhaust to control the mixture, such as the popular AEB Leonardo system and its clones.
Also missing from the pics is a switch to control the system, which also should have something which automatically turns off the gas solenoids (on the tank valve, the vaporiser, and usually the filter), if the engine stops.

[Ilkorin]

Wow, good timing! Loads of info here! Brianmoooore is the man for all the LPG regulations and getting it right!

Also I don't know what pic 6 is - looks like a water pump?

[320Touring]

Thanks very much fellas- starting to make a bit more sense now..

I believe the kit is the older style without the stepper motor, so sounds slightly less complicated to set up.

I believe I have a bag with the Loom/sensors and switch for controlling it- I'll need to ferret it out.

Where is the best place to mount the vapouriser in the engine bay- Was thinking somewhere near the servo as it needs connected to the heater in/outlet?

[Brianmoooore]

I've mounted E30 vaporisers on the chassis rail in front of the suspension turret, and also on a diagonal bracket welded between the chassis rail behind the suspension turret and the rear of the turret. On my E34, it's mounted up where the battery tray would be on an E30, which I would have thought was inviting air locks and filling problems, but it works perfectly in practice.

[Ilkorin]

Mine was where the battery used to be, mounted diagonally, but then you need a battery in boot kit :p

I guess it's a case of manually adjusting the fuelling then? No lambda sensor to worry about either, but I'd definitely recommend an upgrade if the budget allows!

[320Touring]

I've mounted E30 vaporisers on the chassis rail in front of the suspension turret, and also on a diagonal bracket welded between the chassis rail behind the suspension turret and the rear of the turret. On my E34, it's mounted up where the battery tray would be on an E30, which I would have thought was inviting air locks and filling problems, but it works perfectly in practice.

Excellent- I'll investigat if anything needs moved for that to happen- and see what I can create

[320Touring]

Mine was where the battery used to be, mounted diagonally, but then you need a battery in boot kit :p

I guess it's a case of manually adjusting the fuelling then? No lambda sensor to worry about either, but I'd definitely recommend an upgrade if the budget allows!

Touring, so no batteries in the boot

As for "upgrading"- If I get my finger out, the upgrade could be paid for within a month or so, as I'm doing circa 2500 miles a month..

[Ilkorin]

haha you say that, mine is a touring, and battery is in the boot! I take my hat off to the previous owner because I didn't think that was possible either!

[Brianmoooore]

Lambda feedback system doesn't necessarily mean better economy, as a well set up basic system can be adjusted slightly lean, whereas a lambda system will always keep it spot on.
Lambda system will keep it always in tune though, even with varying gas mixes, and allows you to program things in like fuel cut off on over run.

[gareth]

LPG fed white tourings FTW

This will be so much easier to fit without a M30 in the bay so i expect it to be completed before work next week

You may well want to get a roll of new copper pipe and a bag of crush olives ready as it's so much nicer working with new stuff. Tinley tech have always been great when supplying me

[320Touring]

Lambda feedback system doesn't necessarily mean better economy, as a well set up basic system can be adjusted slightly lean, whereas a lambda system will always keep it spot on.
Lambda system will keep it always in tune though, even with varying gas mixes, and allows you to program things in like fuel cut off on over run.

So although "rudimentary", the system should be ok for running on? Car mainly sees motorway driving- so lots of fixed throttle positions

[Brianmoooore]

IF it's set up right, and stays right, then it can be fine, but there's no feedback system or fault warning system, like the Leonardo has, so the first you'll know of a lean mixture is when a piston melts, although engines are much more tolerant of an incorrect gas mixture than a petrol one.

[gareth]

I'd say so yes. And with the fuel savings from the first week, invest in a closed loop controller for an upgrade later on

If you do go this way, avoid £13 budget oxygen sensors as LPG exhaust temperatures kill them in no time. Bosche/NGK/NTK all the way

[e301988325i]

LPG fed white tourings FTW

You may well want to get a roll of new copper pipe and a bag of crush olives ready as it's so much nicer working with new stuff. Tinley tech have always been great when supplying me

I'd personally reccomend using flexible polyflex hosing from tinley tech as it's so much easier to route than bending the copper pipe which work hardens, the price difference is neglible.

[gareth]

Good call

I've not tried the flexible stuff but if i do it again,. that's what i'd use

[DanThe]

Thread revival!

Id be interested to see pics of single hole tank fittings, I believe they are the slowest to fill due to the small bore fill pipe? Ive got a single hole tank but I think im missing a few bits

[Brianmoooore]

http://www.tinleytech.co.uk/acatalog/Ta ... Boxes.html

Early ones won't have a solenoid valve on the outlet.

I have single hole and four hole tanks in use and can't say that the single hole ones are significantly slower. I'd say the pressure of the delivery pump is more significant along with the type of pipe between your filler and tank. The flexible rubber hoses have a much greater internal diameter than 10mm copper pipe.

[Morat]

Neil, where are the "as installed" pics? It's time to get all this knowledge into the Wiki.... If you can get pics, we can hack Brians wall of text into manageable chunks and get it all reviewed before sticking it into the Wiki.

[DanThe]

http://www.tinleytech.co.uk/acatalog/Ta ... Boxes.html

Early ones won't have a solenoid valve on the outlet.

I have single hole and four hole tanks in use and can't say that the single hole ones are significantly slower. I'd say the pressure of the delivery pump is more significant along with the type of pipe between your filler and tank. The flexible rubber hoses have a much greater internal diameter than 10mm copper pipe.

I will have to take it apart and see whats what, the tank im using at the moment is a 4 hole and has the large flexi fill pipe, takes up to 50 litres quicker than most other cars taking half the amount from what ive seen at the gas station.
Is 10mm bore the standard for fill pipe Brian? Or would an adaptor to large flexi pipe be beneficial? Obviously depends on the valve size I expect

[e301988325i]

No fill difference here between our 4 hole and single hole tanks on the same pumps, seems to take bloody ages in the freezing cold!