DIY conversion of X5 using second hand Prins bits

[LPGC]

I seem to remember a thread along those lines (subject), does anyone else? I couldn't find it.

Just had a customer here - Can I have a quick look at his LPG system and tell him how to switch it on?

The switch lit as it should when waiting to switch-over to LPG but it doesn't switch over.. I found because the reducer heating circuit isn't plumbed in and the ECU wiring hasn't been completed The 4 hole tank is just thrown in the boot totally unsecured, no vent piping or bulkhead fittings, tank gauge reads 95% full, filler loose in the boot colour coded for a different coloured vehicle, poly reducer gas feed run straight past the exhaust manifold, ECU loose, wiring to ECU runs between rubber bonnet seal and bonnet, blue silicone vacuum hose runs to the reducer (wouldn't expect this system to even have a vacuum connection), suspension pump relocated to the boot and self tappers used to loosely fasten it to boot interior trim.

Customer reckons he bought the car in good faith as LPG system working and fitted by a pro but it's obvious the system was removed from another X5 (bracket to secure Keihin's atop the engine same as those I've seen made by a certain Prins installer - whom I'm sure didn't fit it on this vehicle!) and only half fitted by someone who didn't know what they were doing. It may be coming back next week for me to complete the wiring and front end plumbing, told him there's no guarantee the system is in 100% working order, if it works I'll be making sure it's safe.. I advised the customer accordingly of course, so if it's going to cost too much to put right he should at least have me take the system off.. but I reckon it'll work, just needs properly fitting etc.

Simon

[kayble]

Was it my conversion of an E38 740i to LPG using 2nd hand Prins VSI 2.0 gear? If so, I''ve got some happy news to report on my coversion - only from today, will update the thread momentarily, but short news is - it works!

[LPGC]

It could have been your install I was thinking of - but I'd thought it was on an X5 or L322 and the OP didn't seem as clued up as you!

Simon

[kayble]

Is it the x5 4.4v8? Is it VSI 1 or VSI 2 gear?

If so, engine essentially identical to the 4.4v8 in my car - subject to changes like introduction of vanos, use of electronic throttle body, rather than manual TB with cables, more sensors, etc

That blue silicone vac hose - is it not reducer pressure relief being plumbed to the intake manifold somehow? Reason I ask is the pressure relief outlet on my reducer isn't plumbed in to anywhere (wasn't plumbed on the donor car either). Strictily speaking does it need to be vented to intake, or can I leave it - or run an outlet hose down into the front passenger wheel well for example, to vent out underneath the car?

[LPGC]

VSI1 and struggling to remember but reckon it will have been the 4.4.

Vanos doesn't really make any difference from an install point of view... unlike Valvetronic. Don't remember ever seeing an X5 with cable operated throttle, thought they were all electronic.

Not much doubt on this install that the blue silicone hose will have been fitted due to the installer's (DIYers) misunderstanding of Prins.

Different schools of thought on over pressure relief valves - Most don't connect a pipe, very rarely seen and then only usually on systems where reducer connects to manifold vacuum (as connecting the relief valve then only involves an extra vacuum T and short bit of pipe from one part of the reducer to the other), only a very small minority run a pipe to somewhere out of the way like under the car and even fewer then seem to have put much thought into where vent gas would exit. Unlikely the valve will ever open, but if it does and it's plumbed to the manifold the engine might stall or not run properly due to overly rich mixture... and then be difficult to start because instead of getting fuel and air the engine gets fuel and more fuel (manifold flooded with gas). Picture the scenario of a broken reducer allowing very high pressure in the vapour lines to injectors and the relief valve venting - driver might think it a good idea to shift the car to somewhere out of the way but he can't do that if the engine won't start, while manifold flooding with gas with a stalled engine will probably see gas exiting the air filter anyway. Then again, gas venting to manifold and causing a drive-ability problem (or stalling) might serve to indicate to the driver that something is wrong - As broad as it is long really, probably isn't an ideal place to route over pressure relief valves to, best place would depend on the extent of the venting and the situation the car/driver were in at the time. Tank valves in any case vent to wherever the tank valve is or to wherever tank external venting pipes (i.e. overshield pipes containing pipes running to internal tank) exit the vehicle... Wheel arch is a good place for reducer PRV pipe to run but wouldn't be if some future owner allows the brake pads to become so worn there's metal to metal contact leading to sparks (might be wishing hadn't connected a pipe in that case). Some reducer designs such as KME have an internal connection between a relief valve and reducer's vacuum reference, thus connecting the relief valve to manifold by default.

Simon

[kayble]

VSI1 and struggling to remember but reckon it will have been the 4.4.

Vanos doesn't really make any difference from an install point of view... unlike Valvetronic. Don't remember ever seeing an X5 with cable operated throttle, thought they were all electronic.

Not much doubt on this install that the blue silicone hose will have been fitted due to the installer's (DIYers) misunderstanding of Prins.

Different schools of thought on over pressure relief valves - Most don't connect a pipe, very rarely seen and then only usually on systems where reducer connects to manifold vacuum (as connecting the relief valve then only involves an extra vacuum T and short bit of pipe from one part of the reducer to the other), only a very small minority run a pipe to somewhere out of the way like under the car and even fewer then seem to have put much thought into where vent gas would exit. Unlikely the valve will ever open, but if it does and it's plumbed to the manifold the engine might stall or not run properly due to overly rich mixture... and then be difficult to start because instead of getting fuel and air the engine gets fuel and more fuel (manifold flooded with gas). Picture the scenario of a broken reducer allowing very high pressure in the vapour lines to injectors and the relief valve venting - driver might think it a good idea to shift the car to somewhere out of the way but he can't do that if the engine won't start, while manifold flooding with gas with a stalled engine will probably see gas exiting the air filter anyway. Then again, gas venting to manifold and causing a drive-ability problem (or stalling) might serve to indicate to the driver that something is wrong - As broad as it is long really, probably isn't an ideal place to route over pressure relief valves to, best place would depend on the extent of the venting and the situation the car/driver were in at the time. Tank valves in any case vent to wherever the tank valve is or to wherever tank external venting pipes (i.e. overshield pipes containing pipes running to internal tank) exit the vehicle... Wheel arch is a good place for reducer PRV pipe to run but wouldn't be if some future owner allows the brake pads to become so worn there's metal to metal contact leading to sparks (might be wishing hadn't connected a pipe in that case). Some reducer designs such as KME have an internal connection between a relief valve and reducer's vacuum reference, thus connecting the relief valve to manifold by default.

Simon

Correct re: throttle operation - my point was that earlier versions of the engine in other cars, 5 & 7 series, had cable operated throttles and no vanos - 'simple' one might say.

So I could essentially leave the pressure relief outlet unplumbed - that's one thing of the post-install task list.

[LPGC]

So I could essentially leave the pressure relief outlet unplumbed - that's one thing of the post-install task list.

Most do, unusual to see one with a pipe connected.

For future reference for connecting a vac pipe to these engines (if fitting a different LPG system)... Can seem a bit difficult knowing where to find a good position for a vac signal on them as the whole accessible part of the manifold seems to be where there's an inlet runner rather than the plenum, or on other versions where it seems you can drill into the plenum that might not be a good idea because there's variable inlet tract length gubbins in the plenum.. Inlet runners not the best place to tap for vacuum reference because the pressure in them pulses as the respective inlet valves open and close leading to inaccurate readings and accelerated wear of the reducer diaphragm, the closer to the port the greater the extent of the pulsing. Instead can drill and tap the flat section on top of the throttle body itself - not too close to either side as you'd be drilling through a TB securing bolt. Don't drill too deep, you only want to drill through the outer section, drill will contact an inner section less than 10mm after drilling through the outer section. The inner section which you can't see is round (bit wider than TB airflow diameter), so although you don't want to drill too close to either side of the TB you don't want to drill in the centre of it either, as there will be less depth between the outer flat section and inner round section closer to the middle... Needs to be enough depth for to drill, tap and fit a spud and for the spud not to seat against the inner round bit. I drill around an inch in from the driver side edge of the TB. Original vac pipes connections on these manifolds are situated mostly around the rear end but it's better to have LPG vac reference close to the throttle body.

Simon

[LPGC]

Update on the DIY X5..

Seems the only part of the install done properly was the mounting of the LPG injectors on the inlet manifold and even then the spuds in the manifold are fitted high up the runner. I expect the only reason the injectors were mounted OK to be because the retro-fit DIYer re-used the original fit installer's bracket here.

The Prins system is incomplete, missing both of it's 4 injector emulator/switching units. The vehicle only runs without those fitted because whoever attempted the wiring hadn't even cut any of the petrol injector wires, they had connected some of the petrol injector cut loom wires (those that run to the petrol ECU side of the cut) but not all of them and some of those were connected to various sensor wires etc instead of to petrol injector wiring. Cyl1 wiring not connected at all, probably because on this V8 X5 cyl2 through cyl8 petrol injector earth wires are brown with various coloured stripes but cyl1 is unique in using an unstriped orange wire for the earth... seems enough to have thrown the DIYer but would have been easy to find the correct wire even without an X5 wiring diagram by simply removing the cover hiding wiring to the actual petrol injectors...

After I'd connected the Prins reducer to the heater circuit it leaked coolant, probably explaining why the reducer wasn't plumbed in even though T's were fitted with reducer end of pipes just crimped off.. One of the T's in any case fitted in incorrect pipe on the outlet side of the heater water flow control valve - I noticed and corrected this before plumbing the reducer in and finding it leaked.

Told the owner about all the above and reminded him of the options - he decided to have me remove the Prins system to fit a known working second hand AEB based system along with new injectors, maybe for the best because if we'd gone the route of completing the install using this Prins system there'd still be the chance it wouldn't work even with new injector emulator/switches and reducer repaired and it was all so poorly fitted it would be just as easy to start afresh. I'll also be making it safe by fitting the rear end properly.

Back to my original post, now seem to remember there being a thread where someone was asking about Prins reducer water connections and Prins wiring - may or may not be the seller of this X5, if not then a coincidence. Whoever sold my customer this car struck a dodgy deal, telling him it was converted to LPG and had been running well on it though it's obvious this vehicle has never run on LPG. I asked the customer if he'd fitted the system, down to earth type bloke says this was the condition he bought it in.

Simon