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2.5 petrol on lpg

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the ginger princess

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Post Options Post Options   Thanks (0) Thanks(0)   Quote mrhutch Quote  Post ReplyReply Direct Link To This Post Posted: 15 Sep 10 at 11:01
geees, thats some length there fella!  Wink

so it is an open loop system??  really easy and fairly cheap to convert to closed, then you don't get as much of an issue with the vap hose length as long as the stepper is close to the mixer..

what shuts off the injectors ?  does the OMVL 90e have that built in?
T3 1981 Westy Vanagon - thinks lubricant is a fuel
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Post Options Post Options   Thanks (0) Thanks(0)   Quote silverbullet Quote  Post ReplyReply Direct Link To This Post Posted: 15 Sep 10 at 11:16
Don't I know it now! This is what I was sold by a well known T3 lpg expert Ouch I wanted closed loop injection, but when I went to collect the reasons/excuses for fitting an open mixer system came thick and fast...he didn't want to pull the manifolds off, basically.
The injector feed is interrupted by a relay fixed to the firewall just in front of the plenum. I guess that the coil on top of the 90e is something to do with that, unless the control switch does it all?
Have I missed anything?
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Post Options Post Options   Thanks (0) Thanks(0)   Quote mrhutch Quote  Post ReplyReply Direct Link To This Post Posted: 15 Sep 10 at 12:48
sounds a bit odd...  I've used open loop systems a few times, and the first time I fitted and drove a closed lambda system I was converted (see what I did there?)

the beetle has an emulator box that plugs into the fuel injector loom that fools the ECU into thinking all is good, but not firing the injectors..  this is signalled by one wire from the leonardo system

I much prefer the closed loop systems, it just makes so much more sense, having a small ECU monitor the exhaust gasses, and moving a stepper valve to compensate gas input, along with a reading from the throttle pot to work the whole stuff out!

IMHO i wouldn't go for an injection system on our types of engine..
I run LPG for economy, there is VERY little power loss with a lambda feedback system, and I need the reliability and simplicty of the system.

Injectors wear out, filters need changing, MUCH more to go wrong on a multipoint inj system on the electrics side, more piping needed etc.. etc...  as you have metal inlet manifolds then stick with the mixer system
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Post Options Post Options   Thanks (0) Thanks(0)   Quote mrhutch Quote  Post ReplyReply Direct Link To This Post Posted: 15 Sep 10 at 12:49
does your ecu not need some kind of feedback from the injectors then?? or is it mechanical like on the porsche 924 engines?
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Post Options Post Options   Thanks (0) Thanks(0)   Quote mrhutch Quote  Post ReplyReply Direct Link To This Post Posted: 15 Sep 10 at 12:51
you've probably seen this but thought i'd post it anyways..  this guy also has some screenshots of closed loop as well

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Post Options Post Options   Thanks (0) Thanks(0)   Quote silverbullet Quote  Post ReplyReply Direct Link To This Post Posted: 15 Sep 10 at 13:03
Thanks for the link! That is pure gold! If only I'd known about it before. Hey Ho. 
The 2.6 SA doesn't have a lambda, it works from throttle angle/resistance, engine speed and air temp. Really simple Motronic ecu with batch-fired injectors. It's like an early T4 2.5 petrol as far as I can tell, just without the feedback from the exhaust.
Here's my el cheapo lambda set-up. Couldn't be simpler, really. If it gets below 0.2v it's too lean, need to aim for the magic 0.45 (just about impossible in the real world) so will settle for 0.7 as the response curve just starts to level out, before it goes too rich. Thanks for the advice about injection, I'll stick with the mixer and move up to closed loop once it's reliable again...
 
This is what is interrupting the injector signal, looks like a basic relay to me:
 


Edited by silverbullet - 15 Sep 10 at 14:02
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Post Options Post Options   Thanks (0) Thanks(0)   Quote silverbullet Quote  Post ReplyReply Direct Link To This Post Posted: 16 Sep 10 at 10:11
Hey Hutch, I've managed to wind things down quite a bit and the old girl still goes like a good 'un, only ever goes lean on the overrun, so no air leaks I guess Smile according to my voltmeter 0.9 - 0.95 volts all day long with idle dancing either side of 0.2 / 0.8 so nice and clean there.
My test run results from Weds night http://forum.club8090.co.uk/viewtopic.php?f=3&t=75070
Still has idle falter/stall/changeover when hot and pulling up to the lights on a closed throttle. Think the coil may be past its best after all?
P.S. What's the purpose of the little knurled knob on the tank valve? Could adjusting this help the system stability at idle?


Edited by silverbullet - 16 Sep 10 at 10:13
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Post Options Post Options   Thanks (0) Thanks(0)   Quote TransPorscher Quote  Post ReplyReply Direct Link To This Post Posted: 16 Sep 10 at 10:31
Interesting stuff ! Especially the Lambda monitoring. My problem seems to be with the K jetronic petrol metering flap. I've found a company in Bristol who said they can convert this system.I'll report in the SA T3 section asap. 

The knurled knob on the tank valve is to isolate/shut off the tank. You should have been told this by the installer,it's a very basic safety procedure!!!! Useful for emergencies,longterm storage or travelling through the channel tunnel !! Wink
Charlie

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Post Options Post Options   Thanks (0) Thanks(0)   Quote silverbullet Quote  Post ReplyReply Direct Link To This Post Posted: 16 Sep 10 at 12:16
While I was checking out the tank valve for loose wiring I found another horror...picture later.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote mrhutch Quote  Post ReplyReply Direct Link To This Post Posted: 16 Sep 10 at 12:41
eeeeekk!!!

it's all fun ain't it !!

Right question for Charlie and Mr Bullet (or anyone else who knows a bit about the workings of injectors....)

would it do an injector any harm to be fired without pressure in the fuel rail  - i.e. firing but nowt to inject??

reason is that with the GTi conversion panel van which is next to be gassed I can see a simple way of stopping the petrol by switching the fuel pump off via a relay, rather than messing with the wiring to the injectors...




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Post Options Post Options   Thanks (0) Thanks(0)   Quote mrhutch Quote  Post ReplyReply Direct Link To This Post Posted: 16 Sep 10 at 12:47
I'm going for the AL820p Advanced Universal Lambda Control System 
system from wtv 



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Post Options Post Options   Thanks (0) Thanks(0)   Quote ELVIS Quote  Post ReplyReply Direct Link To This Post Posted: 16 Sep 10 at 12:49

I thought there had to be pressure in em to keep injectors wet/working/clean whatever you want to call it. Idea behind emmulator (or mateys relay in pic) cut earth/signal to injectors so they dont open but are still pressurised/'wet'.

Surely firing an injector with no fuel is going to fuck it up pdq.
 
 I dont know of anyone who has done it this way but must be a reason as to why all kits/manufacturers do it this way.


Edited by ELVIS - 16 Sep 10 at 12:50
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Post Options Post Options   Thanks (0) Thanks(0)   Quote ELVIS Quote  Post ReplyReply Direct Link To This Post Posted: 16 Sep 10 at 12:54

If this helps anyone have a read. Used it on me 110 3 or 4 years ago and worked pretty well as  i didnt have an analyser to check. (saved onto word from another site so excuse copy n paste)

OK - Here is a little guide to the very basics of a vapouriser and basic tuning.

Assumptions:

Your timing and things are set reasonably OK.  I'm not going to argue over whats the best timing as every engine is different.   6° to 8° BTC should be enough to get you firing.
You ignition circuit, sparks and leads are all in good order.   No spark - No bark.


The Vapouriser

Based on an OMVL R90 vapouriser, and ignoring how it changes the liquid state LPG into gas, the part of the vapouriser that meters the amount of gas to the engine looks similar to this:



The big diaphram gets pulled ( downwards in the piccie ) by the suction from the manifold.  This then pulls on the arm.   In turn at the other end of the arm, the arm controls a little cap covering the main large outlet of the gas.     The more the arm is pulled by the diaphram, the more the cap opens up the hole and the more gas you get. 

How much the arm moves in relation to the vacuum is controlled by the spring.  The larger of the 2 adjuster screws puts preload onto the spring that the arm has to push against. The more preload, the more vacuum required for a given amount of gas delivery.     

The second smaller screw directly contols the opening of a smaller vent hole supply of gas to the engine.   This supply is given regardless of the position of the arm / manifold vacuum.   So even at idle with the throttle body all but closed over and no displacement on the arm ( and thus no opening of the main supply ), this vent will allow a steady flow of gas to the engine, and thus its called the idle bypass.   

The smaller idle bypass adjustment screw is magnitudes more sensitive compared to the tension adjustment screw.   Its in the range of 1:6.   Supposedly 1 turn of the idle bypass screw will delivery the equivalent of 6 turns of the tension adjuster.

For both adjuster screws:

Turning the screws clockwise towards the the body of the vapouriser will reduce the gas supply.   Turning them anti-clockwise will increase the gas supply.




Enough already - Just tell me how to adjust it all . . . .

[ If the engine doesn't run atall on LPG, then goto the bottom section to get some hints / ideas. ]

First of all, get the engine upto normal operating temperature.
Assuming the engine runs on gas, just not very well, then:


Open up the max power adjuster on the gas feed pipe that runs to the manifold.  On the large rubber tube, there should be an adjuster valve which can close the diameter of the feed pipe.  Turn this so that its fully open and is not restricting the flow of gas.

With the engine idling...
Turn the tension adjuster ( the large one ) outwards a lot to make the diaphram really slack.  This will mean that plenty of gas is supplied to the engine when it sucks.
Then slowly turn the idle adjuster clockwise all the way in so it fully closes.   If you find the engine is stalling, then unscrew the larger one to reduce the diaphram tension to keep it idling.

[If you cant do this without fully stalling the engine, then stop screwing the idle bypass inwards - leave it at a point where the engine just manages to run ]

Now with the idle bypass closed off, slowly start to the increase the tension on the diaphram by turning the 10mm adjuster clockwise and inwards. 
Eventually, you should see the engine start to slow drastically down as the gas supply is cut off. 
Stop when the engine is faltering under the normal idle speed, but still managing to run.
Now to get the engine back upto a normal idle, unscrew the smaller 8mm idle bypass adjuster . . . SLOWLY . .  . this is a sensitive adjustment so do it a little at a time
On mine, after about 1 1/2 turns, the engine speed will pick up and start to return to a normal idle.
Adjust the idle screw until you reach a smooth idle speed.   On mine its idles at about 800 - 900 rpm.

Now what you have set is the idle is controlled by this bypass adjustment, but if there is anymore demand from the engine ( by the throttle body being opened ) then the diaphram will immediately move and start to supply the additional gas.

Next step is to adjust that max-power adjuster that you fully opened at the start ( you did remember to do that didn't you? )   The max power adjuster just clamps and sets a limit to the top amount of gas flow that is given at the higher revs and loads.

To set this, get someone to rev the engine to about 3000rpm and keep it there.   With the person holding the pedal steady, screw in the valve until you hear the engine start to slow slightly ( with the person still keeping the pedal still ). 
Then unscrew ( open up ) the valve 1 complete turn.
Now you have set a limit that you know the engine will run at high revs with enough gas, but that you won't be letting an excessive amount through.


Then go back and re-do the 2 vapouriser screw adjustments just to be sure that the max-power adjustment hasn't upet the vapouriser setup.

And that should be enough to get you going reasonably well.   



Naah - its no working and its peeing me off . . . .


If its simply not running atall, then you need to double check all the other parts.   To think of the main ones . . .

Are all the LPG solenoids clicking open OK.
Are the manual shut off valves ( if fitted ) on the LPG tank outlet opened up?
Am i definietly cutting off the petrol fuel supply?
Is the diaphram properly sealed and seated?  Normally 6 screws on the back of the vapouriser - are they all tight?
Is the arm connected properly to the diaphram?
Is the diaphram in good condition and not torn.
Is the tension spring putting a good adjustable range of tension on the arm?  ( Mine wasn't so i had to adjust the spring's length a little )


My settings for my 3.5 carbed V8 are as below.  You may want to try to set your screws to a similar setting as a starting point....
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Post Options Post Options   Thanks (0) Thanks(0)   Quote ELVIS Quote  Post ReplyReply Direct Link To This Post Posted: 16 Sep 10 at 12:58
Originally posted by silverbullet silverbullet wrote:

The injector feed is interrupted by a relay fixed to the firewall just in front of the plenum. I guess that the coil on top of the 90e is something to do with that, unless the control switch does it all?
 
 Is it a black relay on top of the vaporiser your on about ? If so its a safety cut off solenoid.
 
 
 What sort of AFM does the SA buses run ? Is it 'hotwire' type or flapper ?
 
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Post Options Post Options   Thanks (0) Thanks(0)   Quote mrhutch Quote  Post ReplyReply Direct Link To This Post Posted: 16 Sep 10 at 13:01
SUPERB!!

cheers fag-master
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Or_GazM Quote  Post ReplyReply Direct Link To This Post Posted: 16 Sep 10 at 14:31
F*CK ME.......Elvis knows how to cut and paste....can't be as big a w*nker as he pretends to be!!!!!
(Or he wouldn't be able to use both hands on the keyboard....Oh just realised, he probably uses the mouse!)
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Post Options Post Options   Thanks (0) Thanks(0)   Quote silverbullet Quote  Post ReplyReply Direct Link To This Post Posted: 16 Sep 10 at 15:41
Originally posted by ELVIS ELVIS wrote:

Originally posted by silverbullet silverbullet wrote:

The injector feed is interrupted by a relay fixed to the firewall just in front of the plenum. I guess that the coil on top of the 90e is something to do with that, unless the control switch does it all?
 
 Is it a black relay on top of the vaporiser your on about ? If so its a safety cut off solenoid.
 
 
 What sort of AFM does the SA buses run ? Is it 'hotwire' type or flapper ?
 
No AFM at all. Uses air temp sensor (plugged into the air intake rubber elbow) throttle angle pot (integral idle switch for the idle air valve) and engine speed from low voltage side of ignition, as far as I can tell...it's really simple, even more basic than the old 4CU system you may be familiar with on your Landy. Works well enough for ~25mpg on petrol if you don't drive it like a maniac.
PS those generic set-up instructions are ok to get it running (seen before on several sites) but only got me 16-17 mpg on gas, where it was doing 21 before the exhaust swap.
There's a variation that technique at DIY-LPG.com
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Post Options Post Options   Thanks (0) Thanks(0)   Quote mrhutch Quote  Post ReplyReply Direct Link To This Post Posted: 16 Sep 10 at 15:54
c'mon, where this picture of the tank then chap?

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Post Options Post Options   Thanks (0) Thanks(0)   Quote silverbullet Quote  Post ReplyReply Direct Link To This Post Posted: 16 Sep 10 at 15:57
Ok gimme 5 and I'll run out to take a pic and show you what I got...
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Post Options Post Options   Thanks (0) Thanks(0)   Quote mrhutch Quote  Post ReplyReply Direct Link To This Post Posted: 16 Sep 10 at 15:59
* waits for tank-porn *
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