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Joined: Sep 13 2016
Posts: 469

So the P38 has an LPG kit on it. Its all quite old, and i'm not convinced its working properly. The vapouriser appears to be leaking coolant as well.

It has a BiGas SGIS ECU and the Vapouriser is an RI21 DOUBLE, and after some previous discussions on here when i got the car, i swapped the bigas injectors (which werent working properly) out for some Valtek Type-30's. Used the bigas software and managed to calibrate things and get it all mostly working. Its now perfectly drivable on LPG, and if you never switched to petrol you'd probably never have an issue.

So, the issues.

Recently i had a new exhaust installed, and afterwards was surprised that the car felt a lot snappier and more responsive. However it transpired it wasnt the exhaust at all. The car had simply run out of LPG, and was running on petrol. Having done 20-30miles on petrol before refilling the LPG tank, i realised that once on LPG it went back to how it was before.

Second issue, is that at WOT, the car seems to switch to petrol. It doesnt usually beep (though occasionally it does and switches the gas off), the petrol light simply starts flashing, which i believe means the LPG ECU has decided it cant meet the petrol demand, and switches back to petrol. This switch is also REALLY rough, especially if you lift a bit and it decides to switch back to LPG, you get a big jolt as the fuelling goes to shit in the transition. I dont see why 8 LPG injectors should be unable to meet the demand, given the woeful power output of these engines... The vapouriser is apparently rated to 375hp so that shouldnt have a problem either...

Yesterday, while driving on the motorway, i was sitting at 70 climbing a very slight hill, when the LPG ran out. First thing i realised was it felt like someone had opened the throttle about 30% more, the car immediately picked up and started accellerating without my foot moving on the throttle. As i thaught "WTF?" the LPG switch started beeping to say the gas had run out. That suggests to me that the LPG mixture was wrong, but also makes me wonder why, if the ECU could see the pressure dropping, why wasnt it compensating by opening the injectors more...

Clearly i need to sort the vaporiser leak, either by rebuilding the BiGas unit, or fitting something better. Perhaps the vapouriser is faulty or clogged up or something? I'm also wondering if the ECU itself is just too old and crappy and needs updated?

What are folks thoughts.... I often hear people saying the car should run just as well on LPG as it does on petrol, but thats clearly not the situation here!

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Joined: Dec 30 2015
Posts: 1386

It could be that your injector rail pressure is too low and your gas injectors are going above 100% duty cycle to meet demand. This is adjusted by tweaking the reducer - but of course it'll mean re-mapping throughout the range.
The reason for low pressure could be the reducer failing or just that it was poorly set up in the first place.

You really can't spot the performance difference on a well set up multipoint LPG system. Also, it doesn't matter how much power your engine makes - it's the amount of fuel it burns. As you know, that's quite a different perspective on the Rover V8 ;)

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Joined: Jan 16 2017
Posts: 465

Its possible for the vapouriser to leak gas into the coolant - and if yours is leaking from anywhere other than a hose connection (which doesn't sound like it is the case) then theres a good chance the vapouriser isn't keeping up with demand. This can be due to it being clogged up with heavy ends, but if its leaking it clearly isn't in a good state and in all likelyhood the diaphram isn't working as well as it should, which is what moves as the manifold vacuum changes to adjust the output pressure of the vapouriser.

As long as you used an injection vapouriser that can provide enough output for the engine, it doesn't have to be the same as what you currently have. Or as you say you could just rebuild what you have and see if it improves.

The real thing that will tell you whats going on is what pressure your getting out of it when its struggling - if its too low as suggested you just don't have enough time for the injectors to let enough out before they have to close as the inlet valve is closing. That can be down to nozzles being too small as well though (restrict the flow too much). Those are a balancing act between getting them too big (so too much fuel at idle as the injectors can't open/close fast enough) and not big enough (run out of time when demand is high). That said, the advice i was given for the omvl injectors on mine was to just remove the nozzles, that runs well now the ignition problems have been sorted, and when its in good order it does drive the same on both petrol and LPG. (thats a 4.0 in a Disco though, so a 4.6 shouldn't have problems with nozzles being too big at least as long as the pressure is somewhere in the right area). I've got the same injectors on a Focus and again, that doesn't behave any differently when driven on petrol or gas. It is worth having someone professional to do the mapping though (Simon in my case has done both of these, I've had other lpg cars where the kit was already installed by prior owners and they aren't always as trouble free, though given they were getting on a bit by that point its hardly surprising).

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Joined: Sep 13 2016
Posts: 469

The coolant just appears on the top of the case. It can only really be leaking from the seam in the unit, theres nothing else up there.

The rebuild kit from Tinley for the Bigas reducer is £40. Given new ones are around £100, i think thats a poor approach, i might as well just replace the vaporiser.

Clearly though, i'd like something decent and dont really know what to go for:

https://www.lpgshop.co.uk/300bhp-and-more-autogas-reducer/

The LPG chap on here (simon i think?) did suggest i might need to bump the vapouriser pressure up a bit when he suggested the Valtek injectors, but thats something i never did as at the time i just wanted it working and had other stuff to sort out!

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Joined: Dec 30 2015
Posts: 3329

The reducer you have is rated at 380 bhp so is easily capable of running your car so changing it for something else isn't going to give any benefits. What it will do is cause you lots of grief with pipes being in a different place whereas swapping in a new Bigas unit will be a straight swap. For the difference in price I would always suggest a complete new reducer over a rebuild kit. No struggling with seized screws and you know the mechanical parts are new too and not just the rubber bits. I'd say fit a new reducer and then calibrate the system (which may require a slight increase in gas pressure or just tweaking the map).

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Joined: Sep 13 2016
Posts: 469

The bigas would be a straight swap, but its a pretty shabby/untidy install and the bigas unit has some quirks that are annoying. Specifically the water inlets are 10mm (most use 16 and as a result my car has a horrible mashup of pipework feeding it), and similarly the gas outlets are 10mm, rather than the typical 11 or 12 which makes things awkward.

I've currently got 12mm barb on the injectors, an 11mm filter, and 10mm outlets on the vapouriser lashed up with 11mm pipe.

Its a prime opportunity to tidy it all up and try to make a neater job of it all!

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Joined: Dec 30 2015
Posts: 3329

That's true, didn't realise the Bigas was such an oddball. While you are at it, if you are changing the coolant plumbing, reroute the hoses so the reducer is in series with the heater matrix. Quicker warm up and a heater that will work at full tilt when needed.

Simon is the best person to advise which one to go for.

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Joined: Nov 16 2016
Posts: 711

A wide range of reducers suit P38s given the moderate power demand and lots of available under bonnet space... I've probably seen just about every type of sequential system reducer (and pairs of reducers in case of lower powered reducers) on P38s.

But I'd steer clear of reducers which don't have much range of pressure adjustment. Some otherwise decent reducers such as Zavoli Zeta S can be a problem if the narrow range of pressure adjustment doesn't suit the combination of engine and injectors... E.g. the Zavoli Zeta S really only likes to work at 1.5 bar, the older design of OMVL Dream reducers used to be widely pressure adjustable (between 0.8 bar and 1.8 bar) but with some messing about swapping out springs etc and some of the newer OMVL Dream reducers don't seem to like different pressure even if you swap internal springs. So even though a wide range or reducers can work on a P38 it's best to talk about those I'd advise given your injectors etc rather than just say anything goes... Magic3 high power, Romano HD, Emer Palladio should all fit the bill but they all have 8mm inlets, need external filter solenoids, use 16mm water hose and 12mm gas outlet.

I like the performance of the Bigas double reducer but it is bulky, heavy and is a pain regards plumbing. It really is just 2 reducers just stuck back to back sharing a common coolant channel so it has 2 pressure adjusters (1 for each reducer) and balancing their pressure output can be tricky.
The 2 gas outlets must be merged before feeding injectors to ensure both sets of injectors get the same pressure under all conditions...there'd be little chance of each set of injectors getting the same pressure over the engine's full load range if each of the reducers fed a separate set of injectors even if the reducers pressure was balanced properly at some points in the load range, the only condition where you get chance to balance reducer pressure is at idle unless on a rolling road. If you find your outlets are not merged (old installs would use a couple of Y connectors, one to merge, one to split back to separate feeds for the 2 sets of injectors) these days instead of using a couple of Y's you could just fit a H filter (2 inlets 2 outlets)
https://www.lpgshop.co.uk/h-2-inlets-2-outlets-filters/
Even when the outputs are merged, if one of the reducers is set to say 0.9 bar and the other is set to say 1.5 bar the one set at 1.5bar will do almost all the work until it's flow limit is reached at which point pressure will quickly fall to 0.9 bar before the other reducer even starts to do any work, so in this situation you'd effectively have a reducer rated at only 190bhp instead of 380bhp because a system set to work at 1.5bar will probably be approaching the point of switching back to petrol due to low pressure at 0.9 bar. OK if you get the pressure settings near enough balanced, say within 20%, they really are good for 380bhp probably more like 430bhp. To balance pressure first make sure outlets are merged, engine running, watch pressure in LPG software, turn one of the reducer's anticlockwise (increasing pressure) a bit and see if it made any difference to pressure reading, if not try turning the other reducer's pressure up a bit... you're trying to find the one with already highest pressure.. then if you turn the other reducer's pressure up until it just changes the reading on screen the pressure outputs will be balanced.. but confirm the results a few times by turning the pressure screws both ways on both while watching readings. You can perform the balancing the other way around (looking for lowest pressure) but it doesn't work exactly in the opposite way because the pressure reading at idle will obviously always reflect the higher pressure, so you'd be turning down pressure on the one with highest pressure until when you lower pressure a bit more the pressure reading on screen doesn't drop any lower and then pressure should be matched... provided you didn't turn the pressure down on the one you just adjusted too much lol.
Dunno how bad your water leak is. If your reducer just has a stain of coolant on the outside, water doesn't leak into the gas outlets and gas doesn't pressurise your cooling system it might not be bad enough to change or rebuild, though a different model reducer might make for neater plumbing.

AEB ECU's such as your Bigas ECU flash the yellow light on the switch and temporarily switch back to petrol (without any beeps) if they've determined that 1. The necessary gas injector pulse length (given the calibration settings and any compensation for pressure and temperature) is longer than the available window for gas injector pulse length, while at the same time 2. Pressure reading isn't low enough that it would seem you've run out of gas.
If the switch beeps it's because the system has detected low enough pressure that it thinks you've run out of gas, then the switch back to petrol remains unless you press the switch to manually switch back to gas (obviously if you really have run out of gas it will very soon beep and switch back to petrol again).

V30 injectors come in a couple of flavours, some have internal holes only 2.5mm diameter, some have internal holes 3mm diameter. The nozzles they come with also have 2 flavours, some can be drilled out to 3mm, some not quite to 3mm. There would't be much point in drilling nozzles to wider than 2.5mm if internals are only 2.5mm because it would be the internals not the nozzles that would be the limiting factor in terms of flow, but it wouldn't be a problem because 3mm nozzles on injectors with 2.5mm internals would just flow as much as 2.5mm anyway. For 2.5mm nozzles I'd initially set the reducer output to around 1.2 bar, for 3mm nozzles 0.9 bar. The reducers I advised early in this post are all adjustable for that range of pressures while not compromising bhp capability but so too is your Bigas twin reducer.

FIxed a P38 this morning and advised the owner to become a member of this forum... He intends to and I'm sure he'll have plenty to chat about with you all (he has a leaky matrix and other problems)! On the phone he said he had an OMVL Dream system but it turned out he had a Dream reducer and injectors but Stag ECU. His car hadn't run properly on LPG since he'd had the reducer changed at another LPG firm. Don't know what spec Dream reducer he had before but this one was the HP (high pressure 1.7 bar) version. The combination of 1.7 bar and his OMVL injectors with 2.5mm outlets flowed too much gas for good calibration to be possible, for proper fuelling at idle the gas injectors would only need to be pulsed for 2.5ms which is less than the minimum pulse length for these injectors for accurate metering. He'd got a few OBD errors for no lambda signal on one bank and duff probe on the other but I got it set up great after adjusting pressure to 1.2 bar and doing a full recalibration while the lambda probes were working and it was running closed loop (perhaps temporary lambdas working - I advised him to fit new probes but the LPG system is calibrated great now). I was a bit surprised to be able to turn pressure down to 1.2 bar (from 1.7) on this newish Dream reducer without having to remove a spring and without rendering the reducer incapable of flowing enough gas for flat out, an old Dream reducer would have handled it no problem, this is why Dream reducers are not on the list of those I'd advise.

Sorry I haven't been around for a few days.

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Joined: Sep 13 2016
Posts: 469

Thanks. Quite a lot to digest there.

The car currently has an H filter. When i got it it had the pair of Y pipes instead. There was a visible puddle of coolant on top of the reducer the other morning after a short run to move it around the driveway, so it really does want fixing. I suspect the coolants evaporating off when running, but the cold run meant it stayed there. The car also seems to use a lot of coolant, it may also be leaking elsewhere, it seems every time i fix a leak a new one appears!

The Romano HD and the Palladio both look decent. I note you mention external solenoids.

The palladio here appears to have an integrated solenoid:

https://www.lpgshop.co.uk/emer-omvl-palladio-350hp-high-power-reducer/

I also note there appears to be two different gas line sizes, 6mm and 8mm. I'll need to measure up, but if its 6mm line does an adaptor exist to allow it to fit the larger inlet?

I dont know what the internal size of the valteks i have is, but i do know i drilled the nozzles out to 2.5mm so hopefully thats fine.

I suspect it might benefit from a tune up by someone who knows what their doing as well. Just now its running the "auto calibrate" map and nothing more. But i guess i'll get the mechanical bits sorted first then go from there!

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Joined: Nov 16 2016
Posts: 711

Don't want to seem pedantic, yes palladio's are usually supplied with an external filter solenoid (Valtek type 37 or similar the same as Dream HP filter solenoids). The outlet of type 37 filter solenoids feeds gas to a central post with a nut at one end and either screw thread fitting (to attach directly to a reducer) or an M12 fitting to take 8mm copper pipe at the other end. The posts used on palladio's is supplied with the palladio, it has quite a unique thread, which means it would be difficult to connect anything other than that design post... which means a type 37 or similar is almost always used with palladios.. which means suppliers usually ship palladios with type 37's. But strictly speaking integrated would mean it was built into the reducer.

When using a palladio it's almost necessary to use a type 37 filter solenoid fitted directly to the reducer, which can be a disadvantage on some installs where space is tight. With the other reducers I mentioned you have the option of directly attaching a filter solenoid to the reducer (and wouldn't have to be a type 37) by using a common thread male to male adaptor, or fitting a filter solenoid discrete from the reducer with a length of pipe between them.

Adaptors exist. Particularly if your feed pipe is copper an inline adaptor/coupler with a metre or new pipe might be a good idea (even if you didn't want to step up/down pipe diameters)... you might need to extend piping when adjusting routing to get the gas feed to a different design reducer. You wouldn't need to step up pipe diameter for the Romano or MagicJet Extra reducer, they do have 8mm inlets but if you needed to feed them from a 6mm pipe you'd have the option of 6mm or 8mm filter solenoid regardless of whether you fitted the solenoid directly to the reducer... To fit a 6mm solenoid directly to the reducer you'd need to use an M12 to M10 male male connector with an inline 6mm to 8mm pipe connector / to fit an 8mm solenoid directly to the reducer you'd use an M12 to M12 male male connector and wouldn't have to use an inline 8mm to 8mm pipe connector unless you needed to extend the pipe. Similar story if you were fitting the solenoid remotely from the reducer, just that instead of the male male connector if you used copper pipe you'd need an inline adaptor to get from 6mm to 8mm between the solenoid and reducer if you used a 6mm solenoid or between existing feed pipe and the solenoid if you used an 8mm solenoid. Using Faro pipe between a remote solenoid and reducer can be a good idea particularly if you need to step up.down pipe size, both 6mm and 8mm end fittings are available for 8mm Faro pipe (as are end fittings to screw direct to M10 and M12 threads) along with the further advantage of Faro being flexible. You can't get 8mm end fittings for 6mm Faro pipe but can get 6mm end fittings for 8mm Faro pipe. M12 and M10 threaded fittings are available for both 6mm and 8mm Faro pipe but you might struggle to get an M12 6mm fitting. Use 8mm Faro if you intend on using Faro as a means of stepping up/down diameter.