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LPG on K-Jet - Getting there!

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Wychall View Drop Down
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    Posted: 14 Nov 11 at 14:08

Having had my 2.5i 5 cylinder  converted to lpg I have had all sorts of problems due to the airflap gas solenoid no longer being available.  I  have been running for a while with a manual solution of either plugging or opening an additional air tract to allow tick-over on gas. These first two pictures show my concoction for dealing with this.


Air tract blocked


Air tract open and filtered.


This allowed the old gal to run on either fuel - so long as you didn't turn off the ignition! Restarting after running on gas meant waiting for an hour or more as the system was programmed to start on petrol then automatically switch to gas. Unfortunately, until all gas had dissipated from the manifold the petrol injection wouldn't work (don't ask why, I don't understand it either!) This has been overcome by replacing the switch with a manual one. I now control which fuel is used and when. Now a restart is possible when desired.

Now let's get down to the air tract problem. As the gas powered solution is no longer available I decided to look at an electrical solution. As it will need to be powered permanently whilst running on gas I could only select a very small solenoid like this -



This has about a 4w draw so wont hit the alternator too hard.

Now for lots of playing about to get it fitted. Due to space constraints in the airbox it was necessary to install it below the filter.



Now we need to extend the solenoid pin to reach through the filter and make contact with the airflap arm. To facilitate this, and to prevent it catching on the filter, I fabricated a support and tube for the pin to pass through.



Now when the solenoid is activated, the pin extends approx 10mm. This is enough to raise the flap.



Furthermore, there is now room to refit the filter leaving the pin poking through.



We're getting there.  Refit the metering unit and make sure the flap still closes correctly.



Now activate the solenoid..........

This where an electrical solution is sub-optimal compared to gas activated. The very nature of electrical solenoids is that they produce very little force early in their stroke. Certainly not enough to lift the airflap. However, powering the soleniod from the gas valve feed means that the flap is already open using engine suction as the solenoid is activated. At full stroke the solenoid then supports the flap in the open position as engine revs reduce to tickover.



Only a small opening but sufficient to give a regular tick over.

All now re-assembled and running fine. Now I've just got to hope that it is a permanent solution!


 
South African 1991 2.5i 5cyl Microbus - virgin, not campered - piloted by Brian.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote TransPorscher Quote  Post ReplyReply Direct Link To This Post Posted: 14 Nov 11 at 23:45
Looks good !!

 As I've discovered with mine, I think raising the metering flap/disc is more important for idling than the anti-backfire protection it also offers. As when mine backfired recently it just blew the big rubber boot off the top of the metering flap cone. At least the K jet system wasn't affected by this back fire and new plugs cured this problem !!  

Overall I'm happy with my 5 cylinder running LPG, especially as I do so many German trips in the summer. Miles of smiles at nearly half the cost of petrol !!!! But I still think the LPG mixer on the throttle body is restricting this lovely engine. I would really like to find a sequential LPG system with a free standing ECU. Still looking.............

Wink



Edited by TransPorscher - 14 Nov 11 at 23:47
Charlie

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Post Options Post Options   Thanks (0) Thanks(0)   Quote silverbullet Quote  Post ReplyReply Direct Link To This Post Posted: 15 Nov 11 at 10:45
Just who was responsible for this half-arsed conversion in the first place? There's far too many reports of bad work filtering through, for those that are brave enough to stand up and be counted. If the fitter can't do the work, they should say so and decline the job, not bodge it up and say "that's all I can do matey"Angry

On a more positive note...
Nothing available from Tinley Tech? The problem with 5 cylinder sequential is that you need 720 degree triggering i.e. a cam and crank sensor working together so it knows which cylinder is breathing. But there must be LPG'd T5 Volvos out there surely?
Mega Squirt can run full dual fuel/ignition maps according to Phil at extra-efi, but the lpg injectors need BIG power resistors as they are low-impedance.
It's a way down the project list right now...


Edited by silverbullet - 15 Nov 11 at 10:50
Have I missed anything?
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Vanorak
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Post Options Post Options   Thanks (0) Thanks(0)   Quote TransPorscher Quote  Post ReplyReply Direct Link To This Post Posted: 15 Nov 11 at 23:35
I've recently repaired a bodge on my system too !  A company in Bristol did mine with OMVL kit. The owner ( fitter LOL) stormed out of his workshop with his hands in the air last year when I returned my bus for a problem to be solved !!  Just before the "Cornered Rat" stormed out he uncovered a twisted wire joint under some tape right in front of me !!!  I politely turned to his collegue and said " This bus is not leaving this workshop until it's running on LPG !  "  Then I left................. under an hour later it was fixed !!!  


Charlie

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Post Options Post Options   Thanks (0) Thanks(0)   Quote mrhutch Quote  Post ReplyReply Direct Link To This Post Posted: 15 Nov 11 at 23:41
I'm assuming it was a basic open loop system?  


not you charles, the OP..
T3 1981 Westy Vanagon - thinks lubricant is a fuel
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Post Options Post Options   Thanks (0) Thanks(0)   Quote TransPorscher Quote  Post ReplyReply Direct Link To This Post Posted: 16 Nov 11 at 16:36
It's probably the same open loop as mine is.  Another thing to chat to you about Mr H when we hook up ? .........
Charlie

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Wychall View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Wychall Quote  Post ReplyReply Direct Link To This Post Posted: 17 Nov 11 at 18:10
Yes Mr H. It is the basic open loop system. I asked for a closed loop when it was installed but was told that was not possible due to no throttle position sensor.  Cry
South African 1991 2.5i 5cyl Microbus - virgin, not campered - piloted by Brian.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote mrhutch Quote  Post ReplyReply Direct Link To This Post Posted: 17 Nov 11 at 19:35
Originally posted by Wychall Wychall wrote:

Yes Mr H. It is the basic open loop system. I asked for a closed loop when it was installed but was told that was not possible due to no throttle position sensor.  Cry


yeah, heard that one before...  My GTi Panel has always run closed loop without having it's TPS wired in - it only gives certain gains, mainly on the overrun.  For a simple single point closed loop system you only need readings from the alternator(rpm) and lambda to get the mixture set right


T3 1981 Westy Vanagon - thinks lubricant is a fuel
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