Jeep Grand Wagoneer - Single Point System Advice

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Brynjaminjones
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Jeep Grand Wagoneer - Single Point System Advice

#1 Post by Brynjaminjones » Fri Apr 17, 2020 10:20 am

Hi Everybody,

I'm newly registered to the forum and looking for some general advice - I hope you don't mind me coming straight in with questions. Also, please let me know if this is the wrong place to post this.

I have an American imported Jeep Grand Wagoneer with a newly rebuilt AMC 360 V8, running a dual fuel carburettor/mixer open loop system. I've had it for 3 years and have struggled to get much insight on how to get it running at its best on LPG. It's also been pretty difficult to find a good place to get it set up right, but I'd always rather learn myself anyway.
The system was (I believe) installed in the Netherlands.


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I have a few questions:

1. Can anybody help me identify the components? I can't really seem to find any information on anything!

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2. It has always been slow/under powered on LPG. This is even more noticeable after the engine rebuild. It goes reasonably well on petrol but feels completely flat on LPG. It seems okay once you're higher in the RPM range (I don't think the kit is too small), it's just slow to get there!
Can anybody point me in the right direction of how to get it adjusted right?

3. The (original) air intake has a flap inside that redirects to suck warm air from above the exhaust manifold when the engine is warming up. Mine doesn't work, and has been rigged to permanently suck in hot air.
I recently undid this so that it sucks in nice cool air as it's supposed to, but the performance seems to have become even worse as a result!
Would I be correct to assume that it's now running a little lean?

Sorry for the bulk load of questions, I'm trying to learn how to work on it whilst there's plenty of time to do so!

Thanks,
Bryn

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Re: Jeep Grand Wagoneer - Single Point System Advice

#2 Post by Brynjaminjones » Fri Apr 17, 2020 10:21 am

Here are a couple more pictures just to help identify:
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Re: Jeep Grand Wagoneer - Single Point System Advice

#3 Post by Brian_H » Fri Apr 17, 2020 11:18 am

The 3rd and 5th pic shows what looks like one of these https://tinleytech.co.uk/shop/lpg-parts ... er-901504/ OVML R90e vapouriser to me, yours is probabbly the older version, should have two adjusters on it

The 4th pic shows what I would think are your power valves (used to adjust fuel mixture by altering the amount of gas flowing).

2nd pic shows your mixer by the looks of what can be seen

Gillbertd has detailed what the adjusters do in this thread - viewtopic.php?f=33&t=14355&p=111840&hilit=r90e#p111840 though this is with a closed loop system, yours being open loop doesn't have the lambda sensor to aid with adjustment.
Gilbertd wrote:
Fri Jun 08, 2018 7:39 pm
The smaller, top screw is the idle bypass which would normally be screwed fully home and the bottom, larger one is the main bias screw. Newer R90E vaporiser have two screws that are both 6mm hex and the other way round. The lambda controller should show lambda flicking from one end of the scale to the other when it is correct. If the leds in the display are different coloured, usually red is rich and green is lean. You need to set the vaporiser so that the lambda flicks at both idle and open throttle which is easier said than done with a lambda controlled system because changes you make may be adjusted by the controller.
Start with the basics first - you mention about the exhaust flap for the heater, the vapouriser needs a decent flow of warm coolant through it, so is it getting hot when the engine runs? if not you need to find out why and see if you can resolve that (can be blockage, or a plumbing issue depends how its connected, they can also get airlocked, particually if they are high in the engine bay). Not sure what to advise on the heat side of things, but the two could be related if there is a plumbing issue (you typically plumb the vapouriser parallel to the heater matrix, so one may provide an easier path for the other sometimes)

Theres a bit more info on the following site http://www.diy-lpg.co.uk/articles/files ... -loop.html - This is one of the members here (SimonHobson), though he doesn't appear to be active anymore unfortunately, it does detail whats involved and how to check its setup.

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Re: Jeep Grand Wagoneer - Single Point System Advice

#4 Post by Brynjaminjones » Fri Apr 17, 2020 11:32 am

Thanks Brian, some very useful information there. I will take some time to read and digest!

My only concern is that without a Lambda sensor I'm worried about messing something up horribly.


With regards to the air intake flap, it seems to me that it only affects the temperature/flow rate of intake air, rather than having an effect on the vaporiser.

The vaporiser actually seems to be nice and hot at all times. It has run well in the past even when cold-started in ambient temperatures below freezing.
The low power issue is always consistent, with seemingly no variation based on ambient or engine temperature.

I did read somewhere once about having to create a pressure drop in the air intake when using this type of system, but I haven't been able to find it since. Is there any truth to that?

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Re: Jeep Grand Wagoneer - Single Point System Advice

#5 Post by Brian_H » Fri Apr 17, 2020 11:38 am

Brynjaminjones wrote:
Fri Apr 17, 2020 11:32 am
Thanks Brian, some very useful information there. I will take some time to read and digest!

My only concern is that without a Lambda sensor I'm worried about messing something up horribly.


With regards to the air intake flap, it seems to me that it only affects the temperature/flow rate of intake air, rather than having an effect on the vaporiser.

The vaporiser actually seems to be nice and hot at all times. It has run well in the past even when cold-started in ambient temperatures below freezing.
The low power issue is always consistent, with seemingly no variation based on ambient or engine temperature.

I did read somewhere once about having to create a pressure drop in the air intake when using this type of system, but I haven't been able to find it since. Is there any truth to that?
The pressure drop should be handled by the mixer and power valve, You really need one of the members here that know the single point setup better than me, one of them will be sure to appear sometime soon and help out there, and may be able to spot a few other points to help.

Got what you mean regarding the flap now, that makes a bit more sense. Point taken on the lambda sensor, that was my feelings on it, there may be another trick one of them can share with you before starting to adjust it (besides the one Simon's site shows, which involves using a temporary one to see whats going on). Otherwise you might be looking at taking it somewhere with an exhaust tester and adjusting it there as a last resort, once you know what the adjusters do thats a bit easier obviously!

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Re: Jeep Grand Wagoneer - Single Point System Advice

#6 Post by Gilbertd » Fri Apr 17, 2020 11:48 am

Brian is spot on, it is indeed the ubiquitous OMVL R90E vapouriser on an open loop system with the manual power valves. Not quite sure why you have two as it appears that only the top outlet of the R90E is being used and the mixer appears to have only one gas inlet too. Unless it has a second one that can't be seen in the pictures. If you folow the guide Brian linked to, it not only tells you how to set it up but will also explain how it is supposed to work. As the Jeep has a carb I doubt it will have a lambda sensor but a good mod would be to add one in one of the downpipes and that will allow you to fit a closed loop controller such as this https://tinleytech.co.uk/shop/lpg-parts ... ol-system/ so the mixture will be controlled by that over the whole rev range. Set up properly (or using a lambda controller to constantly adjust it) and you should notice no difference in power between running on petrol or LPG.

The flap for drawing in warm air is there purely to stop carb icing in the winter. On a cold, foggy, day when the ambient temperature is just above freezing, the increased speed of the airflow going through the venturi in the carb, coupled with the moisture in the air, can cause ice to form in the carb. Manufacturers way of stopping this was to draw warm air in from next to the exhaust manifold until fuel injection started to appear which allowed them to fit a throttle body heater which did the same thing. It's one of those things that you will only find it a problem on maybe 10 days of the year when conditions are just right. The pressure drop in the intake will be taken care of by the air filter which will sit in the housing around the outside of the mixer, you'll only normally find it a problem if you remove the original air filter housing and try to use a K&N or similar free flow filter.
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Re: Jeep Grand Wagoneer - Single Point System Advice

#7 Post by Brynjaminjones » Fri Apr 17, 2020 12:15 pm

Thank you both for your help so far, this is really getting my head around it a little better.

There are a few things I should clarify:

Both power valves are hooked up. The hidden one goes to the bottom of the vaporiser. Both are hooked up to the mixer, the angle of my photo just managed to obscure that!


Thank you also for the explanation of the warm air flap. I do understand why it's there from the factory, running on petrol. The reason I'm so concerned about it is because a previous owner had added screws through the housing so that it was permanently in the warm air setting.
I removed these screws last week to allow cooler air to be drawn in, but I'm convinced it now feels less powerful on LPG. I've just put it back to how I found it temporarily to see if any power is restored!

My guess is that he couldn't get the vaporiser tuned right, so did this as a bad "fix". There are lots of questionable "fixes" done by previous owners on this car that I've slowly been removing!


Without installing a lambda sensor, is there really any proper way to adjust it at home?

Thank you again!

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Re: Jeep Grand Wagoneer - Single Point System Advice

#8 Post by Brian_H » Fri Apr 17, 2020 12:49 pm

I'd assumed the bottom one was being used, but a thought that now occours to me, is that one of the common bits of advice given on these is to check if the vapouriser needs draining of heavy ends. If your using the bottom outlet this shouldn't be a problem, but its easy enough to check it by removing the hose. Gloves recommended for that though, if it is full of gunge and needs draining you don't want the stuff on your hands as it stinks and will take days to go away by washing your hands if your not careful.

Don't know other than what I'd linked to on the sensor, maybe Richard or someone else (Simon?) can advise on that one?

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Re: Jeep Grand Wagoneer - Single Point System Advice

#9 Post by Gilbertd » Fri Apr 17, 2020 1:33 pm

It can be done at home, although ideally you need a lambda sensor in a bit of tube as a minimum as per the article linked to. You can get it pretty close by ear though. Start with the lower (idle bleed) adjuster on the vapouriser screwed fully home (not half a turn out as Simon suggests) and adjust as per his instructions. You should be able to get it something like just by ear. However, bear in mind that when the diaphragm in an R90E starts to fail the first symptom is going rich at idle. So you may end up in a situation where you can get it right at idle but lean at open throttle or correct at open throttle but rich at idle. This is another advantage of using a lambda controller, it constantly fine tunes to keep the mixture correct by using a stepper motor controlled valve instead of the manual power valve.
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Re: Jeep Grand Wagoneer - Single Point System Advice

#10 Post by Brynjaminjones » Fri Apr 17, 2020 1:52 pm

Brilliant, thank you.
I think I'll tackle it tomorrow when my girlfriend is home to help hold the throttle in the right position.

In all honesty, I doubt I'll make it worse than it is currently!

One more question in the meantime though: What do I do with two power valves? As they both go to a single mixer, do I just adjust them at the same time to the same settings?

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Re: Jeep Grand Wagoneer - Single Point System Advice

#11 Post by Gilbertd » Fri Apr 17, 2020 2:40 pm

Yes, try to keep them both the same, or at least close. The R90E can cope with an engine up to 6 litres but obviously if you only use one outlet that will restrict the maximum flow you will get from it. In saying that, I'm only using one outlet on both my Range Rovers, a 4.0 litre and a 4.6, without going lean at full throttle.
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Re: Jeep Grand Wagoneer - Single Point System Advice

#12 Post by Brynjaminjones » Fri Apr 17, 2020 7:04 pm

Perfect, that's what I thought. After being bored out during the rebuild it is now just shy of 6.0 litre, but I doubt it's making any more power than your 4.0 Rover.

Now, I have got a spanner to throw in the works:
I've just been for a good drive after fixing the intake flap back into the hot air position.
It's like a new car! All the missing power is back - I'd honestly say it's twice as powerful with that flow restriction in place.

Is there any explanation for this?

I mentioned earlier that I'd read about people putting in a flow restrictor. I've just found a forum post saying the same thing. Quoted from Landyzone:
On my 101, which had a high compression 3.5 on twin su's, there wasn't enough mixer depression to give me a good mixture.
I had to cut a restrictor plate, with about a 2" hole, and put it in the air box.

The standard 101 airfilter and pipe work was so free flowing, there wasn't enough depression to pull the gas through, so I had to create a little bit of restriction to get enough depression for the LPG evaporator to work.

Try putting a bit of a restrictor in your intake - see if you can get the mixture to richen up.

Sounds contrary, but unless you have a really hot tune engine, big intakes don't really help. Oh, and if you have a mechanical evaporator, make sure your intake doesn't point I to the incoming air, or you will run lean at speed.
Is there any truth to this?

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Re: Jeep Grand Wagoneer - Single Point System Advice

#13 Post by LPGC » Fri Apr 17, 2020 8:11 pm

There's truth in the quote in certain situations.

The reason you're getting more power with the intake in the hot air position is very likely because it causes more of a restriction to incoming airflow ('more depression') which causes the mixture to be rich enough (compared to less restriction causing a too lean mixture) / or because you're getting a 'ram air' effect if the pan type air filter intake points forwards in the cool air position. Ram air is an effect which can occur if the intake faces forwards because as the car moves forwards air is pushed into the intake causing the opposite to 'depression' (positive pressure), if there is positive pressure at the gas openings of the LPG mixer no gas will flow into the engine, in practice ram air doesn't cause no gas but can cause less gas.
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Re: Jeep Grand Wagoneer - Single Point System Advice

#14 Post by Brynjaminjones » Fri Apr 17, 2020 8:25 pm

Thanks Simon, that seems to make a lot of sense.

The air cleaner does point about 45 degrees toward the front so I suppose this could be what's happening, although it's lacking power even from a standstill so I guess it's more the restriction that's relevant here.

With that being the case, should I leave it as it is now, or change the intake to the cool air position and richen the mixture to compensate?

Thanks,
Bryn

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Re: Jeep Grand Wagoneer - Single Point System Advice

#15 Post by Gilbertd » Sat Apr 18, 2020 12:25 am

Up to you but while the theory says that cooler air going in is more dense so has more oxygen resulting in more power, under normal conditions the difference is likely to be so small you'll never notice it. Presumably the extra power was on LPG? I wouldn't have expected it to make any difference on petrol.
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Re: Jeep Grand Wagoneer - Single Point System Advice

#16 Post by Brynjaminjones » Sat Apr 18, 2020 10:40 am

Yes you're right, the power difference was on LPG. I've not tried it on petrol, but I can't imagine it would have made a difference as it always feels powerful on petrol.

I'm trying to decide now if I want to play with it at all, or not.

If this flow restriction is having this large an effect, do you think it will even be possible to alter the mixture enough to compensate?

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Re: Jeep Grand Wagoneer - Single Point System Advice

#17 Post by Gilbertd » Sat Apr 18, 2020 11:02 am

No idea but this is the one big advantage with a lambda controller. With an open loop system such as you have, you can set the mixture and it will be correct at that time. As soon as the air filter starts to get a bit clogged, temperature changes from mid-winter to hot summer, air intake flap position, etc, the mixture will no longer be correct. With a lambda controller it will adjust going on the signal it sees from the controller.

However, if it's working now with the intake flap in the winter position, leave it alone.
96 Saab 900XS, AEB Leo, sold
93 Range Rover 4.2LSE, Lovato LovEco, sold
97 Range Rover 4.0SE, multipoint, sold
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Re: Jeep Grand Wagoneer - Single Point System Advice

#18 Post by LPGC » Sat Apr 18, 2020 2:01 pm

I wouldn't be able to resist trying to improve fuelling with the air intake set to the cool air position but I'd be confident of being able to put it back to how it is now if adjustments had a negative effect...

If it effects the idle even when the vehicle isn't moving it will be the difference in restriction rather than ram air that's effecting things, so I'd have a play with the reducer's sensitivity setting.

Assuming you can switch between gas and petrol at any time and assuming mixture is good on petrol, a basic check for correct mixture on LPG by ear is to hold rpm at say 1500 while running on petrol, switch to LPG while keeping foot steady on the throttle and see if rpm falls or raises. If it falls it's most likely lean on LPG so increase reducer sensitivity a little until rpm on LPG matches rpm on petrol.

Still ram air may have an effect, so in the case the sensitivity adjustment made a positive difference at idle but there were still problems cruising at light throttle or when coasting I might make up a shield for the forward facing inlet to lessen any ram air effect.
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Re: Jeep Grand Wagoneer - Single Point System Advice

#19 Post by Gilbertd » Sat Apr 18, 2020 2:12 pm

LPGC wrote:
Sat Apr 18, 2020 2:01 pm
Assuming you can switch between gas and petrol at any time and assuming mixture is good on petrol, a basic check for correct mixture on LPG by ear is to hold rpm at say 1500 while running on petrol, switch to LPG while keeping foot steady on the throttle and see if rpm falls or raises. If it falls it's most likely lean on LPG so increase reducer sensitivity a little until rpm on LPG matches rpm on petrol.
For completeness, you screw the upper of the two adjusters on the R90E OUT (anticlockwise) to increase sensitivity and make the mixture richer.
96 Saab 900XS, AEB Leo, sold
93 Range Rover 4.2LSE, Lovato LovEco, sold
97 Range Rover 4.0SE, multipoint, sold
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96 Range Rover 4.6HSE Ascot, AEB Leo, my spare


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Re: Jeep Grand Wagoneer - Single Point System Advice

#20 Post by Brynjaminjones » Sat Apr 18, 2020 5:53 pm

Thank you both, I think you've given me sufficient confidence to give it a go tomorrow. It's just too tempting to resist trying, plus I don't think it's ever been set up using any other method than by ear anyway!

I will make sure to mark all the adjusters and count the number of turns on everything so I can reset if needed.

Hopefully I'll have something to report back with tomorrow!

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