Advice please!

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LPGC
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Re: Advice please!

#341 Post by LPGC » Wed Dec 02, 2020 6:15 pm

Pinger wrote:
Wed Dec 02, 2020 1:17 pm

As far as I can ascertain my petrol fuel trims haven't deviated to the point of being problematic (it starts promptly on petrol) and I don't want to lose that.
If utilisation of the grey wire(s) is helping this should I consider just tagging the AFR meter to one of the O2 sensor wires?

This:''The mixer system may hold lambda voltage above 0.5v above 4000rpm,'' is a feature of mine. If not the 4000 rpm threshold then a (configurable) TPS threshold. That is one of the things I want to monitor (and tweak) with the AFR meter.
Worth considering leaving the grey wires connected but connecting the LPG system in the 'normal' way without the grey wires might not affect starting etc and even if it did you could easily go back to having the grey wires connected. Same regards the 4000 rpm threshold, the petrol ECU might switch to open loop before 4000rpm anyway... But if it remains closed loop above 4000rpm, and if grey wires are not used, then since the LPG system intentionally holds mixture rich above 4000rpm the petrol trims for above 4000rpm will eventually go fully lean (which may be better than fully rich but unless you've seen what trims are already and confirmed they've gone fully lean above 4000rpm already the car could drive a bit flat above 4000rpm on petrol if grey wires are disconnected).

However you wire in the LPG system, if you wire in an AFR meter it will need to connect directly to lambda signal voltage - But usually an AFR meter (at least if it's wide band) will need it's own (wide band) lambda sensor. Your truck's current lambda sensor must be narrow band if the mixer system connects to it. Some AFR meters allow you to replace the vehicle's narrow band sensor with AFR meter kit's wide band sensor, the AFR kit can then output a narrow band equivalent voltage for the petrol ECU and Millenium etc to connect to (as if a narrow band probe is still fitted).
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Pinger
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Re: Advice please!

#342 Post by Pinger » Sat Dec 05, 2020 2:05 pm

Gilbertd wrote:
Tue Dec 01, 2020 7:03 pm
It'll be branded Millennium and will have Millennium firmware but if you look at the circuit board, it's still an AEB175, so quite what the other pair of wires are doing is anyone's guess. Can you pull the boot on the plug back and see where the extra pair of wires are connected?

Moulded on the back of the ECU box it has TIPO: AEB 175, Leonardo, Regmatic, Millenium. Previously, I identified it by the Regmatic and Millenium stickers on its front.

As for the wiring. There's a small bundle (within their own conduit) that goes to the four pins (in square formation) next to the smaller fuel level gauge/dash switch plug that has four wires coloured purple, white, orange and blue.
The other purple wire is in the middle of the plug and sits beside the only grey wire. Presumably then that grey wire is branched into two somewhere between the AEB ECU and the GM ECU but without taking the loom apart I can't confirm this.

Pinger
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Re: Advice please!

#343 Post by Pinger » Sat Dec 05, 2020 2:26 pm

LPGC wrote:
Wed Dec 02, 2020 6:15 pm
However you wire in the LPG system, if you wire in an AFR meter it will need to connect directly to lambda signal voltage - But usually an AFR meter (at least if it's wide band) will need it's own (wide band) lambda sensor. Your truck's current lambda sensor must be narrow band if the mixer system connects to it. Some AFR meters allow you to replace the vehicle's narrow band sensor with AFR meter kit's wide band sensor, the AFR kit can then output a narrow band equivalent voltage for the petrol ECU and Millenium etc to connect to (as if a narrow band probe is still fitted).
My AFR meter is designed to run from the existing narrowband probe.

LPGC wrote:
Wed Dec 02, 2020 6:15 pm
Worth considering leaving the grey wires connected but connecting the LPG system in the 'normal' way without the grey wires might not affect starting etc and even if it did you could easily go back to having the grey wires connected. Same regards the 4000 rpm threshold, the petrol ECU might switch to open loop before 4000rpm anyway... But if it remains closed loop above 4000rpm, and if grey wires are not used, then since the LPG system intentionally holds mixture rich above 4000rpm the petrol trims for above 4000rpm will eventually go fully lean (which may be better than fully rich but unless you've seen what trims are already and confirmed they've gone fully lean above 4000rpm already the car could drive a bit flat above 4000rpm on petrol if grey wires are disconnected).
I think I want to leave the grey wires connected - not least as far as I can ascertain it has been OK configured thus (more on that in a moment).
GM fuelling strategy AFAIK is to go open loop not at pre-set rpm but at threshold TPS value after a period of time. Thus, sufficiently out of kilter to make preserving the grey wire worthwhile?

The AEB has both purple wires (but only one grey) and I'm assuming it better to leave it like that.
The obvious place to connect the AFR meter then is to tag it to one of the purple wires coming from a Lambda sensor heading for the AEB ECU. But for the concern any voltage emanating from the meter will be detected by the AEB ECU.
If I (initially) get the truck running and connect the lap top to it such that I can see the AEB activity ie, Lambda and stepper activity, if I then bring the AFR wire to the purple wire any untoward effects will immediately show on the Lambda and stepper activity - yes? If nothing untoward I can hard wire it. Any reason not to?

If that works, I can periodically switch to petrol running with the AFR meter and see where the mixture is ie, fuel trims. If they are wayward, I can consider the alternative wiring arrangement (run the Lambdas direct to GM ECU, tag them for the AEB ECU, tag one of them for the AFR meter and delete the grey).

Does this make sense?

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Re: Advice please!

#344 Post by LPGC » Sat Dec 05, 2020 5:02 pm

The AFR meter can't show a very wide range of mixtures if uses a narrow band probe because narrow band probes can only measure a very narrow range of mixtures near stochiometric.

Whether you connect the grey wire or not shouldn't have any effect on how it runs on gas but can have an effect on how it runs on petrol when you've first switched back to petrol. You may think if it ain't broke on petrol don't change it.

The AFR meter obviously has to see raw lambda signal, which is the same signal the AEB175 has to see. The AFR meter and AEB175 shouldn't pull the voltage on the lambda signal wire (unless they go wrong) but some petrol ECU's do pull voltage on the lambda signal wire in certain conditions by design, this implies another potential positive for using the grey wire. For example, some (older) ECU's will pull their own lambda voltage input to 0.5v during open loop, fault conditions, or warm-up. It's easy to imagine the ECU designers thinking that they could program the ECU to ignore lambda readings during these conditions but that might take a bit of coding and the ECU might be a bit short of memory... Or they could just wire in a simple on/off output which when on (during open loop, warmup or fault conditions) connects 0.5V through (say) a 1K resistor to the ECU's own lambda signal input. Since the ECU is probably programmed to increase fuel trims for anything above 0.45v and decrease for anything below 0.55v holding voltage at 0.5v means the ECU doesn't change fuel trims. If we disconnect a lambda sensor from many vehicles that have 0>1v lambda sensors and measure the voltage on the ECU's lambda signal input wire there's around 0.4v, which might beg the question why not 0v.

Yes any untoward effects should be visible because you can use one reading to check the other. You could even use a digital multimeter or oscilloscope to check if connecting either/both AFR/AEB175 effects readings, all voltage readings should agree same as if you'd connected 10 digital multimeters / scopes and connecting/disconnecting such component shouldn't effect the reading.

Makes sense.
Last edited by LPGC on Sat Dec 05, 2020 5:14 pm, edited 1 time in total.
Full time LPG installer
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Pinger
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Re: Advice please!

#345 Post by Pinger » Sat Dec 05, 2020 5:11 pm

Thanks LPGC. It will be done as described and we'll see if it works (or not).

Pinger
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Re: Advice please!

#346 Post by Pinger » Tue Jul 13, 2021 5:41 pm

Bit of an update - but first the inevitable question!
Background first. Changed the inlet manifold gaskets and when I put it all back together it wouldn't start (on petrol) but soon found that it would if I opened the throttle very slightly. So, adjusted the throttle stop screw (normally a tamperproof screw but someone had been at it before me). It then started without throttle but preferred a tickle when cold. Then it threw a wobbler and almost didn't start. It was ultra sensitive to throttle opening. None and it would offer but not catch. A touch more and it wouldn't even offer. Finding the exact opening between those two points was hair-trigger. On the advice of the Chevy forum (wind the throttle stop screw out and let the IAC valve do its job) I now have a lower idle speed (welcomed) and good cold starting. But, the changeover to LPG is erratic (hot and cold).
Question: if I extend the 'injectors remain on time' (currently at 0.4s IIRC) will this help? I'm guessing the reduced throttle opening isn't enough for air and LPG vapour and the motor is dying before the LPG can get there (my changeover is on decell). Plausible?

Truck is running well. AFR gauge is working and swings around - the more so since.... the fuse for the O2 sensors and MAF sensor was found to be AWOL (during post inlet gasket change no-start) and re-instated. The improvement in O2 sensor is welcome but is nothing compared to the improvements in the transmission with a now functioning MAF sensor.
Previously it was slow to change up at big throttle inputs, schizoid kicking down (far too eager and compounded the hanging in gear issue) and suffered really hard part throttle upshifts. All remedied now. Up-shifts are smooth (now the ECU doesn't assume every up-shift is at WOT and ramp up the line pressure) and I can control shifting with my right foot and spend most of a day in top gear and let the V8 torque work its magic - bliss!
A bunch of other stuff also done but as not LPG related (ATF and PAS fluid changes, etc) I'll skip - unless anyone wants some practical advice on how-to while it's still fresh on my mind.

So, back to my question. Extend injector on-time and if so, by how much?
TIA - and thanks everyone for the help in getting my truck to a set-up that I'm really enjoying. Much of my concern about mixer size adversely upsetting transmission was in fact due to the MAF sensor being out of action. That concern has now gone.

Gilbertd
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Re: Advice please!

#347 Post by Gilbertd » Tue Jul 13, 2021 8:43 pm

It may be you need to increase the changeover delay but how is it being controlled at the moment? The Leonardo has a pair of yellow wires connected to an internal relay which are closed when running on petrol and go open circuit when switched to gas, the idea being they can be used to disconnect the power to the petrol injectors. The switching is delayed and this is what is altered by the setting in the software. However, most petrol injection ECUs object to seeing open circuit petrol injectors so Pitagora injector emulators are used instead. These are wired in line with the petrol injectors and triggered by the blue wire (the one that switches the solenoids) to cut the circuit to the injectors but put resistors inline instead so the petrol ECU doesn't know that aren't there any longer. The Pitagora has it's own built in delay so you would need to adjust it there rather than through software.
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93 Range Rover 4.2LSE, Lovato LovEco, sold
97 Range Rover 4.0SE, multipoint, sold
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Re: Advice please!

#348 Post by Pinger » Wed Jul 14, 2021 9:43 am

Thanks Gilbertd. It's as well I asked as by the looks, what I intended would have made no difference but I would have believed I'd made a change.
I have the emulators. Two of them, each of them dealing with four injectors IIRC. But I haven't seen (or noticed at least) any adjustability - what am I to look for?

Is the issue I've encountered the likely reason why the throttle stop screw has previously been adjusted? What I've been told on the GMT400 forum (by a very knowledgeable guy) is that these screws are fitted with tamperproof heads, never need adjusting, and when they have been moved it is usually to mask another problem. His advice to screw it back out and let the IAC do its works seems like good advice - and has improved the cold starting on petrol and reduced the idle speed to something more sensible already.

Would adjusting upwards the changeover rpm help? My technique is to blip to above changeover rpm and the changeover occurs as the rpm drops on a closed throttle. My thinking here is that it would give more time for the changeover before the rpm decayed to zero.

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Re: Advice please!

#349 Post by Gilbertd » Wed Jul 14, 2021 11:41 pm

Delay on the Pitagoras is adjusted with a pot that can be seen from the plug side between the two pushbutton switches (don't change them)
96 Saab 900XS, AEB Leo, sold
93 Range Rover 4.2LSE, Lovato LovEco, sold
97 Range Rover 4.0SE, multipoint, sold
98 Ex-Police Range Rover 4.0, AEB Leo, daily motor
96 Range Rover 4.6HSE Ascot, AEB Leo, my spare


Proud member of the YCHJCYA2PDTHFH club.

Pinger
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Re: Advice please!

#350 Post by Pinger » Thu Jul 15, 2021 1:36 pm

Don't change the switches - correct?
How sensitive are the screws, in which direction is extending the overlap? How much should I turn them at a first attempt?

Gilbertd
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Re: Advice please!

#351 Post by Gilbertd » Thu Jul 15, 2021 6:49 pm

No idea, according to the AEB documentation, they are initially set for 0.4 seconds so one way or the other. I would suspect, and this is purely a guess, clockwise would increase the delay. But it may be anti-clockwise......
96 Saab 900XS, AEB Leo, sold
93 Range Rover 4.2LSE, Lovato LovEco, sold
97 Range Rover 4.0SE, multipoint, sold
98 Ex-Police Range Rover 4.0, AEB Leo, daily motor
96 Range Rover 4.6HSE Ascot, AEB Leo, my spare


Proud member of the YCHJCYA2PDTHFH club.

Pinger
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Posts: 325
Joined: Tue Feb 11, 2020 5:08 pm

Re: Advice please!

#352 Post by Pinger » Fri Jul 16, 2021 1:16 pm

Thanks Gilbertd. I found the screws and decided that before I go messing with them I'd give it another chance as the changeover thing was last week immediately after I'd adjusted the throttle stop on the driveway after a longish run.
Started up and switched over OK today - but the idle on LPG was a bit iffy. After a short run it seems to have sorted itself out. All of this I suspect is rooted in the IAC valve making adjustments but it seems to have found a setting (the inlet manifold gasket change put its nose out of joint for some reason). I'll know better next week after a 150 mile work trip.
At the very least, I now know that emulators can be tweaked - which I didn't before. Cheers!

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