1998 BMW 740i - DIY Conversion using Prins VSI 2.0

[kayble]

Hello,

My name is John and I'm converting my 1998 BMW e38 740i, using Prins VSI 2.0 equipment.

Firstly, about the car. It's an M62B44 non-vanos 4.4 v8 car - something of a project when I purchased it last year for less than a grand off a pitch in Manchester. It's in Mora Mettalic, which is a pretty rare colour and I'm only aware of 2 other 740is in this colour in the UK. Here's a picture of the vehicle:



One of the things I've always wanted to do is a self-completed conversion to LPG, an opportunity to do so came up recently when I became aware of a BMW 540i being broken for spares on one of the forums I subscribe to. That car had recently had a Prins VSI 2.0 installation completed, but was to be scrapped due to terminal rust. I was able to purchase the core of the front end kit for a modest price, which crucially included the intake manifold with injectors already mounted and tapped - a major shortcut. The engine in the 540i is essentially identical to the 740i so my operating theory was essentially to transplant the intake manifold and complete the front end install around it.

Here's the IM on the bench, I need to swap around the petrol fuel rail but it's essentially ready to go straight on the car:



And installed on the block in the car (gas injector wiring is temporarily looped on the top of the manifold as it wasn't wired when I took the picture):



The injectors are Keihin KN9 73cc injectors - which I understand to be a sufficient flow rate for this 286bhp engine.

I've kept the old manifold in the loft as a spare.

I've been able to locate the gas ECU in the cage for the vehicles petrol and transmission ECUs, which is in the top right of the engine bay and is sealed and climate controlled. This should make the front end install quite neat, and it also means I can use the original wiring & insulation runs for the petrol injector interruption wiring and the rest of the Gas ecu ancillary wiring.

To protect wiring that has to exit the car's original insulation runs within the engine bay, I'm using shrink wrapping to protect the full length of the wire that's exposed ( it also gives a slightly more original look to the installation):



The vapouriser is located on the frame holding the PAS fluid reservoir & oil filter assembly. I've made a bracket that allows the reducer to sit low down just behind the NS light cluster:



it's a B&Q corner bracket cut to size, holes enlarged and a notch cut out to suit the mounting point on the car. It permits this installation (please forgive the cable ties that are uncut - the installation is still in progress of course):


Closer focus on the vap:


I want to protect the 16mm ID vapour outlet hose as it travels around the oil filter housing - for the moment the rubber spacer on the hose is a temporary solution until I can find some appropriate pipe 'armour' - if there's a better word. I'll post up about

[kayble]

The tank is a 680/220mm Irene toroidal single hole, tank located in the wheel well. Having measured the available space I was sure this would be largest tank I could use, but it turns out I could have used a 240mm or possibly taller tank and still have had the boot carpet floor lay perfectly flat - ah well, live and learn.

Removing the spare wheel stub thread with a dremel - I was happy to see that I could use the resulting hole for inlet/outlet for the tank:



Preparing the well for the tank - mounting holes driled and some insulation applied to the side walls:



test fitting a number of layers of foam underlay (excuse the damage to the donut underlay section, I used it in a sandwhich of 4x 3mm underlay sections to give lots of lift of the floor of the well so as to clear the neck of the spare wheel stub thread aperture:



Tank installed:


Slightly irritated by the fact you can see a small amount of the insulation to the bottom left of the tank - will see to that if I have to remove the tank for whatever reason.

This conversion is still in progress so will post as I get on with it - more to come in a moment.

[scottyf]

All coming together nicely.
The inlet was a good idea. The tank I wouldn't worry about it being a little undersized. As you say live and learn. I am also not sure you would get away with additional packing foam on the base if it wasn't as undersized as you say.

[classicswede]

Looking good so far. If you have not gone too much further turn the tank around the right way

[kayble]

Looking good so far. If you have not gone too much further turn the tank around the right way

Hello - as it happens, I didn't know there was a right way for the tank to be installed - but it will only fit in its current orientation because the the mounting holes in the centre of the tank are 'off centre' so to speak, meaning that if its mounted the other way round, the edges of the tank chafe the wheel well wall. As it is, it fits very nicely and I can use the hole left by cutting out the spare wheel turret.

[kayble]

I've made some further progress on the intstall - although it's been slower of late owing to holiday and work.

Quick look at the LPG fuel line route, now that it's in.

As it comes down from the engine bay next to NSF brake line, there's some protective edge stripping to prevent chafing:



Through NSF inner arch towards NS underneath car:



Underneath NS - need to put another clip in just below the cross member:




NS underneath - towards petrol fuel tank:



Coming up to NSR arch beside the petrol tank - the hose is attached to the inner sill so the tank (god forbid) can come out if need be:



Hose then goes up and over the arch beside the gubbins for the tank breather:



and down towards the rear subframe:





It then travels across the vehicle to a central point behind the spare wheel well - attached to the vehicle body and well away from the exhaust, to emerge (using the existing heatshield - with some additional edge stripping to prevent chafing) and then travelling to the inlet/outlet for the tank:

[kayble]

And present condition of the engine bay - after vapour hoses and filter have been installed:



Not the best pic but all wiring comes out the original outlet on the side of the ECU box - the slightly loose black wire to the right of the shot is the trailing earth for the trickle charger hook up.

I now have a lot of solder joints to complete, then tank wiring and filler to install, at which point, likely round the end of October, I'll be ready to run gas (hopefully)!

Many thanks to Lukie for the kind message - looking forward to discussing the conversion further.

[Gilbertd]

I didn't know there was a right way for the tank to be installed - but it will only fit in its current orientation because the the mounting holes in the centre of the tank are 'off centre' so to speak,

Better re-drill the holes then. You've got the pickup at the front so when you're down to around a third of a tank of gas and you give it some welly, slosh will uncover the pickup so you'll drop back to petrol. Pickup needs to be at the back.

[kayble]

Better re-drill the holes then. You've got the pickup at the front so when you're down to around a third of a tank of gas and you give it some welly, slosh will uncover the pickup so you'll drop back to petrol. Pickup needs to be at the back.

Fixed this today:



Drilled another bolt hole for the re-installed tank (it actually fits better now than it did previously. I'll get a plastic blank to close of the hole that's not used any more. Also did some more soldering - but lots more still to do!

[kayble]

Hello chaps, can't quite believe it's been almost half a year since I posted on this thread; don't worry - still got the car and still working on it! In late July I also bought a Land Rover Discovery 3 tdv6 - which in the 6 months since I bought it in July needed new rear discs/pads/shoes, brake hoses, 2 front wheel bearings, full cambelt service and boots on NSF driveshaft... It's been up on ramps more than the e38 recently:



That said, it's a great car now that the bits left wanting at around 100k have been sorted.

Since my last update, I've made a few bits of progress worthy of note.

Next job was to install the filler. I knew from the start that I wanted a location on the bumper, rather than a hole in one of the wings. I am aware of the COP11 amendment suggesting a minimum height of 500mm so as not to be awkward. As it happens, the filler is in the bumper, readily accessible at 450mm height, on the offside - same as the petrol filler.

Tinley tech supplied a daunting looking core drill bit, and I bit the bullet. No pictures of the drilling in progress (too nervous to stop!) - but I went through the bumper and the plastic reinforcing support behind it - at a point where the support wouldn't be weakened and I could still install the necessary boot on the rear of the filler. Here it is installed:



Pipe work routed through the rear arch, and then on above the rear subframe:



At the closest point to the exhaust at the back of the filler assembly, there is, just, 250mm clearance to the rear of the exhaust back box, which is covered by the vehicles existing heatshied, what the picture doesn't show so well is that it's also in a corner of the bumper assembly and you couldn't get to the exhaust if travelling directly from the rear of the filler assembly. There's certainly enough distance, in a direct measurement to the exhaust tips at the rear of the car, enough that I haven't botherd to measure. I'll use some heat shielding on points of the filler and tank feed lines that travel closer to the exhaust around the rear subframe, where it isn't protected by the car's existing heat shielding.

At the moment, the boot on the filler is pulled back so I can get to the gear behind the filler, and the wheel arch cover isn't back in as I still need to do some wiring - but all of that will get done before it goes for testing. I should say that any pictures of the wheel arches, where you can clearly see the tank or filler lines aren't representative of the final product - of course both the factory arch liners will go back in when the car's finished.

Here's the filler line as it travels under wheel well into the tank area - some more edge stripping added to the vehicle heatshield to stop chafing:



What I do need to do is make up is some spreader plates for the tank mounting bolts - much bigger/wider than the standard washers. It was brought to my attention that the spare wheel turret is in fact only screwed/bonded in to the wheel well - so it's not a permanent part, meaning I need to spread the load around the bolts between the turret and the permanent bit of the well. That can wait till I'm a little further down the line though.

[LairdScooby]

You're certainly doing a nice job of it! Puts BMW to shame for effort and achievement!

Looking forward to seeing the finished article!

[LPGC]

Will need some more P clips under the wheel well, I think you'll know that.
Would've been a good idea to run tank solenoid and fuel sender wiring at same time as pipe to engine bay!
Some fighter plane wings are glued on but you do need bigger washers. Instead of washers, I sometimes use a length (or lengths) of flat bar... which could be bent and extended all the way around the well up to boot floor.

Simon.

[kayble]

Will need some more P clips under the wheel well, I think you'll know that.

Hmm I thought I had done enough in the wheel wells - but will take another look.

Would've been a good idea to run tank solenoid and fuel sender wiring at same time as pipe to engine bay!

Ah - well I have somthing of an admission to make in this area. I didn't like the idea of running wiring under the full length of the car. Instead, I've run wiring for tank sender/solenoid inside the car. I came out the rear of the ECU box inside the engine bay, where the LPG ecu is, through a factory grommet in to the cabin, down the length of an existing wiring run for the CD changer, nav hardware etc and in to the boot. I'll need to extend the wiring from there, but the plan is to go round the rear of the boot, out through another factory grommet to underneath the NSR arch in vicinty of the filler line, and then follow the filler line from the rear arch to the tank valve. Benefits were I could lay the wiring and the lpg lines as separate exercises, and avoid unnecssarily exposing the wiring to the elements.

Some fighter plane wings are glued on but you do need bigger washers. Instead of washers, I sometimes use a length (or lengths) of flat bar... which could be bent and extended all the way around the well up to boot floor.

Agreed - I plan to make up some large'ish spread plates - perhaps not as big as what you're suggesting, but certainly substanial enough to cross the turret and permanent wheel sections securely.

Incidentally - I hadn't written the height of the filler on the bumper in the last post. It's 450mm to the centre of the filler from the road, possibly a bit more/less depending on load in the boot. My judgment call is that it is sufficient, isn't awkward, and would therefore be acceptable for COP11 purposes - I'm interpreting the amendment as a suggestion rather than hard/fast requirement for min of 500mm clearance?

[LairdScooby]

That's a very good question on the 500mm "amendment" as a minimum height for a filler point. My Jeep has the filler mounted in the bumper end cap which to be honest i'm not wild about but it's there and i don't plan on moving it, at least not for the time being.
If the owner of the vehicle doesn't plan on selling it and is quite happy to have it at a "below minimum" height, how rigidly are the rules enforced?

[LPGC]

Wiring under cars isn't a problem, after all it's inside an outer layer of insulation which is plastic and weather proof but there's nothing wrong with running it the way you said.

Incidentally - I hadn't written the height of the filler on the bumper in the last post. It's 450mm to the centre of the filler from the road, possibly a bit more/less depending on load in the boot. My judgment call is that it is sufficient, isn't awkward, and would therefore be acceptable for COP11 purposes - I'm interpreting the amendment as a suggestion rather than hard/fast requirement for min of 500mm clearance?

Not worth worrying about! Many installs fitted by UKLPG members have the filler below 450mm. But then again, of course someone might consider it OK for them to do it, but not OK for you to do it, particularly if they're in a money making/grabbing frame of mind. May depend on whom inspects it (and when), yet we all know it's safe. Best advice - Save yourself the bother having it inspected, pay someone over the phone to register it on UKLPGs database if you need it to be on there, unlikely you do need it on there.

Simon

[kayble]

Hello all,

Been a long time since I updated on this project - but it's been lurching on slowly whilst life got busy at home and work. Couple of posts to come shortly with progress on tank and wiring

[kayble]

Delighted to say that since my last substantive post, my LPG conversion is complete and appears to be working!

Essentially, since the last post with pictures in it - I got busy at work again, and the car had to play second fiddle. There were a couple of tasks still remaining to get the conversion to a point where it should work, although I wasn't confident it would go swimmingly. Tasks were:

1. Complete tank sender and fill/outlet hoses on tank mulitvalve
2. Complete tank solenoid and sender wiring
3. Fuel injector interrupt wiring
4. Rest of main gas ecu wiring.

Made up a nice diagram for the injector interrupt wiring - shows engine cylinder numbering, gas injector numbering & wiring numbers:



Wasn't looking forward to all the soldering - but it turned out to be less of a task than expected. This is how I spent most of Saturday evening last week:



Remainder of gas ECU wiring was quite easy - fair few wiring groups not needed in fact (MAP, lambda, OBD, etc). Took RPM from cyl 7 coil signal wire (same as donor car) and 12v+ for petrol injectors off a 12v feed for vehicle MAF, ICV and engine ECU, amongst other things.

The finished tank multivalve area:



With everything wired up and checked, I nervoulsy reconnected batt -'ve and turned key to pos 1 - the first sign that things were on the up and up:



Tank was completely empty of course - but turned the car over to check petrol operation - no problems at the end of yesterday evening - excellent!

[kayble]

Following morning, I went to my local filling station somewhat nervously for first fill.

Slightly cheeky pic - as phone shouldn't be out on forecourt, but just to show the nerves involved - see the fire extinguishers at the ready!



The filler (not pictured as phone was put away before going near the pump) worked just fine, and at a perfectly usable height - had no problem at 2 different stations I filled at during the day.

After first test fill I turned the car over and there was no start - suspect because supply line was empty, switched to petrol mode then back to gas - and it ran perfectly! Left it idling for a few minutes whilst I checked for leaks with washing up fluid (minor bubbling on fill line multivalve union - nipped up tight) and took it for ~50 mile shakedown; it runs a treat!

Remaining tasks:

1. Reinstall boot interior trim
2. Make up/install spreader plates for tank mount bolts (existing large washers don't spread sufficiently between wheel well permanent floor and the bonded in bit for the centre turret.
3. some more p clips underneath spare wheel well to further secure fill and outlet lines.
4. Safety inspection and addition to UKLPG register (Simon?)

Whilst I'm at it, some pics showing finished filler boot installation (finished with jubilee clips at both ends) - and the tank wiring as it exits from the boot and goes around under the well to re-enter through the multivalve vent:

[LPGC]

Great write-up and well illustrated!

Not a bad idea but can imagine thoughts of others as multiple fire extinguishers are positioned beside the vehicle on the forecourt - What's up here then, risque fire breathing show perhaps...

Probably best policy not to switch to gas for the first time while on a forecourt - an oversight like not tightening a pipe leading to gas leakage could be alarming to others (who don't know that such leak will quickly stop after electro-valves shut-off), I tend to wait until I'm at a quiet layby or back at base just in case.

4. Safety inspection and addition to UKLPG register (Simon?)

Look forward to hearing from you

Simon

[kayble]

Great write-up and well illustrated!

Not a bad idea but can imagine thoughts of others as multiple fire extinguishers are positioned beside the vehicle on the forecourt - What's up here then, risque fire breathing show perhaps...

Simon

I parked up and went in to tell them it was my first fill (on this car - have had LPG before), and told them I wanted to move a fire extinguisher round the back of the car just in case. The chap who had queued up behind me had a chuckle and told me 'good luck' as I went to fill up; couldn't quite tell if he left the forecourt any quicker than he might otherwise have done after paying lol!

It didn't want to turn over to gas straight away in reality - the E38 has a behaviour whereby a single 'twist & release' will operate the starter motor until the engine fires - or after something like 10 seconds it will give up. I had 10 seconds of crank and then it gave up - so turned off gas ecu at the button and it fired on petrol. Took it over to a corner and turned gas back on; it gurgled slightly then switched over; I think this was because the supply line was empty, so a little while before liquid phase at the reducer could be turned to gaseous phase for the injectors.

I'm really surprised it appears to be working after transplant - I was most worried that I might not have used the correct tank sender for what the gas ECU had originally been set up for. When I purchased the used kit, I foolishly didn't buy the donut tank (had wanted a cylinder so I could retain the spare) - therefore I didn't know if the ECU had been set up for 0-90 ohm sender, or Prins hall effect sender (each has a different setting in the gas ECU. Had it not worked, it wouldn't have been a disaster - I'd just get the gas ECU reprogrammed; but it would have been a pain - so I'm glad it appears to have gone well.

Need to sort final tasks before safety inspection, and a filter change after a tank or two - and then relax!