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..lee.. View Drop Down
Vanorak
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    Posted: 14 Nov 10 at 22:03
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Originally posted by ..lee.. ..lee.. wrote:

ooooooo. ive had an idea.
 
 
 
 
 
 
 
 
                                          tdiThumbs Up
 
 
 
 
 
 
.
 
The bastard, he always has the best ideas.
 
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Originally posted by ..lee.. ..lee.. wrote:

ooooooo. ive had an idea.
 
 
 
 
 
 
 
 
                                          tdiThumbs Up
 
 
 
 
 
 
.

Thanks! Thumbs Up

Nah, I like the 2.1WBX, despite its various quirks. If I wanted a cheap to run, reliable and practical van I'd buy a T4 LOL
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ooooooo. ive had an idea.
 
 
 
 
 
 
 
 
                                          tdiThumbs Up
 
 
 
 
 
 
.
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Originally posted by ..lee.. ..lee.. wrote:

seb i think you have got it the wrong way around.

Quite possibly! Tongue

However, this is what happens from cold startup on petrol: the lambda output at idle is essentially steady for, I dunno, a while (Aidan reckons 30 seconds but it seemed a bit longer than that to me, though I didn't time it) until the engine starts 'listening' to the lambda and cycling the afr to keep the exhaust somewhere between just lean and just rich. At that point the lambda output suddenly changes to the curve you'd expect. 

Of course the afr will vary a bit anyway, but surely it can only cycle between 0.1 and 0.9v if the fuelling is actively being changed, whether that's because of throttle position off idle or because the ecu is varying fuelling at idle? If there isn't that constant cycling of afr then the output voltage from the lambda will be a steady 0.x v, where x varies according to throttle position and engine load.

My lambda changes output voltage with afr as you'd expect. But it only cycles when it's running on petrol. That seems right to me.

At least, that's how I understand it. But I could well be wrong LOL Will look into it some more...
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seb i think you have got it the wrong way around. the lambda influences the afr according to what is already pre programed in to the fuel map in the ecu. its an add on. and not the main controll. oxygen in the exhaust gas is dependant on how complete a burn the combusion chamber produces. the oxygen content in the exhaust gasses varies very slightly even without a closed loop lambda system its just with that type of system there is no lambda correction.
if you connected a lambda probe to a non lambda system you would see it vary voltage as the oxygen left over from the burn varies.
it should do the same with gas i belive. the posts on you tube seem to confirm this.
if the afr is optimsed on the gas and the oxygen levels in the exhaust gas are correct i can see no reason why the lambda should not behave and produce a variable voltage of between 0.1v and 0.9v. if the oxygen level goes outside of the lambda`s tolerance then it will flatline. thats what will cause the fuel system to play up when you switch back over.
i dont think it should flat line on gas. "again i`m no expert but the video`s on you tube show voltage variance on gas. check it out"
 
i think if you hanen`t allready done it check the lambda readings on petrol and also as you switch over to gas and let us know what the readings were at idle and at say 2500 rpm.
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Originally posted by Beaker Beaker wrote:

probably difficult to do effectively as the signal lead is only running less than 1v and low amps and is screened to prevent interference because of that, relay would probably cause interference itself

and yes it does a system check on start up and after 30 secs, if no lambda it'll go to default map, that's why when they fail and you get the overfuelling and black smoke undriveability if you stop and turn off and disconnect lambda when you restart it's ok

Shame really, because if you could switch the lambda via a relay I would've thought you could wire it up to the fuel switch so it'd be automatic...
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Originally posted by ..lee.. ..lee.. wrote:

think you have to confirm that the lambda probe is flat lining first. then the question, why? needs to be asked. possibly get in touch with bosch technical and see what there take on lambda with gas is.??
there`s a few posts on youtube about gas and lambda. looks like the lambda is switching with their systems.

No mystery. The lambda simply responds to the amount of oxygen in the exhaust gases. On petrol the ecu is constantly tweaking the mixture between just lean and just rich (at idle, anyway, I'm not quite clear what happens under load?), hence the lambda's variable output. On an open loop gas system the only lambda variation is with throttle position IIRC. There's no attempt to vary the mixture second by second on any given throttle position and so only a constant output from the lambda. It's behaving exactly the way it should.

Next step up would be to have an lpg ecu hooked up to the lambda, engine temp and (and this is the problem with the SS and MV engines) the throttle position switch and controlling a stepper motor to vary gas mixture accordingly, a bit like the way the system works on petrol. Only there isn't a TPS on these engines Confused
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think you have to confirm that the lambda probe is flat lining first. then the question, why? needs to be asked. possibly get in touch with bosch technical and see what there take on lambda with gas is.??
there`s a few posts on youtube about gas and lambda. looks like the lambda is switching with their systems.

Edited by ..lee.. - 14 Nov 10 at 14:05
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probably difficult to do effectively as the signal lead is only running less than 1v and low amps and is screened to prevent interference because of that, relay would probably cause interference itself

and yes it does a system check on start up and after 30 secs, if no lambda it'll go to default map, that's why when they fail and you get the overfuelling and black smoke undriveability if you stop and turn off and disconnect lambda when you restart it's ok
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Originally posted by Baxter Baxter wrote:

Connect the lambda sensor through a relay do its disconnected during use on LPG?

I wondered about that too, but I wondered if the ecu will only recognise the lambda on startup? if that's the case it wouldn't solve the problem...
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Connect the lambda sensor through a relay do its disconnected during use on LPG?
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Originally posted by Baxter Baxter wrote:

Originally posted by SebRogers SebRogers wrote:

And another one, if I'm feeling particularly flush: 

5. - try a Bosch lambda in place of the Beru. Seems to work for Aidan...
I can't see that making a shit of difference TBH.

Yeah, I know it doesn't make any sense, but it seems to work for Aidan. Otherwise either my gas setup's wrong (don't think so - Steve checked it, twice, and it runs beautifully with about the right mpg and the right emissions), there's something else wrong on the petrol side, or trying to get open loop lpg to play nicely with closed loop petrol is just asking for trouble. Trying a different brand lambda is the only thing left I can think of.

Quote I think if you bought a Lambda meter thing and drove around with it you would be able to physically see what was happening.
Didn't Silver bullet build his own?
Theres a thread on 80-90 I think.

Yep, I thought of that. Might be a bit more faff than I'm prepared to get into, not sure yet.
 
Quote The fault could work the other way, the gas could be very rich, and the lambda sensor is telling the ECU to lean right off, then you flip to petrol and the ECU is supplying next to no fuel, engine throws a wobbler.

Yeah, thought of that too. The weak link in all this is the gas side doesn't make use of the lambda and the petrol does. So taking the lambda out of the equation is one way to make it work...


Edited by SebRogers - 14 Nov 10 at 12:02
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thought so
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Originally posted by ..lee.. ..lee.. wrote:

sime in box full.
On purpose!
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Originally posted by SebRogers SebRogers wrote:

And another one, if I'm feeling particularly flush: 

5. - try a Bosch lambda in place of the Beru. Seems to work for Aidan...
I can't see that making a shit of difference TBH.
I think if you bought a Lambda meter thing and drove around with it you would be able to physically see what was happening.
Didn't Silver bullet build his own?
Theres a thread on 80-90 I think.
 
The fault could work the other way, the gas could be very rich, and the lambda sensor is telling the ECU to lean right off, then you flip to petrol and the ECU is supplying next to no fuel, engine throws a wobbler.
 
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sime in box full.
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Well, I learnt something....
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thats the bumf  its only hc so doesnt matter much when setting up.
 
said it was a while ago.


Edited by ..lee.. - 13 Nov 10 at 23:01
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Assess the colour of the exhaust smoke.

2. Exhaust Gas Analyser Test

Follow the analyser manufacturer s

instructions and carry out the full test

procedure to determine the proportions of

carbon monoxide (CO) and

hydrocarbon (HC).

On LPG vehicles the HC result obtained must

be divided by the PEF

(propane/hexane equivalency factor) marked

on the analyser to obtain the

figure required to assess the test result. Some

machines do this automatically.

Residual hydrocarbons, which are indicated

by the analyser when it is sampling

clean air, must be deducted from the HC

reading for the vehicle.

If a vehicle meets the CO requirement at its

normal idling speed but fails the

HC check, recheck the HC level at a high idle

speed of 2000rpm. If the HC

reading is then 1200ppm or less, the vehicle

will have met the CO and HC

requirements. Light pedal pressu
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