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[TheBoy]

Not my car.....

Live data, when idling on LPG, short term fuel trims tend to go up to 15-20 on each bank. Flick back to petrol, and it starts to drop back to 0.

Hold revs at 2k rpm, long term fuel trims go up in to teens (short term stay around 0) on gas, again tend to settle nearer 0 when on petrol.


Is this just the LPG calibration being out?

[JamesV6CDX]

What size are the manifold nozzles TB?

[Kevin Wood]

Is this just the LPG calibration being out?

Yep. I find mine wanders around a bit more on LPG than petrol. Does sound like that's got a consistent problem though.

Kevin

[Lazydocker]

Is this just the LPG calibration being out?

Yep. I find mine wanders around a bit more on LPG than petrol. Does sound like that's got a consistent problem though.

Kevin

I'd agree... We noticed mine wandered a bit IIRCC

[TheBoy]

Speaking of calibrations, Mr Wood, I may need to borrow your good self up in the lakes for half an hour, suspect mine needs recalibrating/tweaking (based on its done a couple of thousand now)....   ....and the firmware is about 4 version out of date

[Kevin Wood]

No problem. 

Will try to remember to install the latest version before I leave.

kevin

[feeutfo]

its my car, thanks TB, so i guess raise the Vap pressure half a bar at a time and re calibrate until lpg fuel trims match petrol ? should be able to do that with elm cable etc.

I need to fiddle with it as it bogged badly at the end of my road, hot weather caused early switch over to gas just as i hit the pedal to pull out into a gap in the traffic, not good.

[Lazydocker]

its my car, thanks TB, so i guess raise the Vap pressure half a bar at a time and re calibrate until lpg fuel trims match petrol ? should be able to do that with elm cable etc.

I need to fiddle with it as it bogged badly at the end of my road, hot weather caused early switch over to gas just as i hit the pedal to pull out into a gap in the traffic, not good.

Interestingly, I've dropped my vap pressure to 1 BAR for an experiment and it seems better, although I had the early switchover and bog down issue whilst in Yorkshire... I put the main problem being that I had next to no LPG in the tank (I'd run out on the way in the previous evening) and the early switch meant that the car's ECU was still applying enrichment which isn't needed when running on LPG. It actually stalled and was not a convenient time, travelling uphill! It did smell very strongly of petrol when it re started for a few seconds too!

Still... I wish we could get to the bottom of this niggle because it's getting very frustrating!

[feeutfo]

its my car, thanks TB, so i guess raise the Vap pressure half a bar at a time and re calibrate until lpg fuel trims match petrol ? should be able to do that with elm cable etc.

I need to fiddle with it as it bogged badly at the end of my road, hot weather caused early switch over to gas just as i hit the pedal to pull out into a gap in the traffic, not good.

Interestingly, I've dropped my vap pressure to 1 BAR for an experiment and it seems better, although I had the early switchover and bog down issue whilst in Yorkshire... I put the main problem being that I had next to no LPG in the tank (I'd run out on the way in the previous evening) and the early switch meant that the car's ECU was still applying enrichment which isn't needed when running on LPG. It actually stalled and was not a convenient time, travelling uphill! It did smell very strongly of petrol when it re started for a few seconds too!

Still... I wish we could get to the bottom of this niggle because it's getting very frustrating!

it is indeed frustrating, some input from Tilo needed by now surely, i think between us we've tried enough settings to conclude we cant get rid, just move it about under certain conditions.

Had about 1/3 of a tank when it bogged setting off to Ashridge meet.
....and of course i mean .05 of a bar at a time, not "a" Bar at a time.

Trouble is i have no idea what to do with this mapping business. Calibration seems accurate and easy enough, but the last few tweeks while driving....plus i need a decent driver if i'm play on the lappy.

[Lazydocker]

its my car, thanks TB, so i guess raise the Vap pressure half a bar at a time and re calibrate until lpg fuel trims match petrol ? should be able to do that with elm cable etc.

I need to fiddle with it as it bogged badly at the end of my road, hot weather caused early switch over to gas just as i hit the pedal to pull out into a gap in the traffic, not good.

Interestingly, I've dropped my vap pressure to 1 BAR for an experiment and it seems better, although I had the early switchover and bog down issue whilst in Yorkshire... I put the main problem being that I had next to no LPG in the tank (I'd run out on the way in the previous evening) and the early switch meant that the car's ECU was still applying enrichment which isn't needed when running on LPG. It actually stalled and was not a convenient time, travelling uphill! It did smell very strongly of petrol when it re started for a few seconds too!

Still... I wish we could get to the bottom of this niggle because it's getting very frustrating!

it is indeed frustrating, some input from Tilo needed by now surely, i think between us we've tried enough settings to conclude we cant get rid, just move it about under certain conditions.

Had about 1/3 of a tank when it bogged setting off to Ashridge meet.
....and of course i mean .05 of a bar at a time, not "a" Bar at a time.

Trouble is i have no idea what to do with this mapping business. Calibration seems accurate and easy enough, but the last few tweeks while driving....plus i need a decent driver if i'm play on the lappy.

I didn't re-map mine last time, just calibrated it and went for a run, checking the map as I went.

It's still lagging slightly, but more like we got on yours in Essex, with just a slight hesitation instead of the full blown (albeit brief) loss of power.

As for Teilo... I've not really tried to get hold of him lately. In fact, I've not really had chance to get on here much either due to other commitments

[Kevin Wood]

its my car, thanks TB, so i guess raise the Vap pressure half a bar at a time and re calibrate until lpg fuel trims match petrol ? should be able to do that with elm cable etc.

Don't need to touch the vapour pressure. It will just be fine tuning of the map that it needs. 

Do another auto-calibration if you like, just for good measure, clear both curves in the map display, collect a curve on petrol and then one on LPG, adjust until they match.

Kevin

[Kevin Wood]

Or.. Disregard the mapping screen in the AC software and tune it for minimal fuel trim using the OBDII display.

Kevin

[Lazydocker]

its my car, thanks TB, so i guess raise the Vap pressure half a bar at a time and re calibrate until lpg fuel trims match petrol ? should be able to do that with elm cable etc.

Don't need to touch the vapour pressure. It will just be fine tuning of the map that it needs. 

Do another auto-calibration if you like, just for good measure, clear both curves in the map display, collect a curve on petrol and then one on LPG, adjust until they match.

Kevin

It seems that the maps drift more than I expected over time... I had mine spot on last time and when I looked the other day the LPG map had drifted North a little... Still well within the 10% deviation line but had drifted none the less.

[Lazydocker]

Or.. Disregard the mapping screen in the AC software and tune it for minimal fuel trim using the OBDII display.

Kevin

Now that would be an interesting approach... I'd be interested to hear the results of tuning it that way.

[Kevin Wood]

It seems that the maps drift more than I expected over time... I had mine spot on last time and when I looked the other day the LPG map had drifted North a little... Still well within the 10% deviation line but had drifted none the less.

I think it's not an exact science mapping against the measurements in the LPG ECU. Different weather, road conditions, etc. during calibration will affect it.

Also, if you rely on the petrol curve that has built up over time that will have mostly been collected during warmup and, probably over the little bit of pottering around you do after each startup before hitting the open road, so it's always a good idea to clear that, do a run on petrol and then lock the petrol curve before looking at the LPG curve.

Also - you are mapping in 2 dimensions only. Injector duration versus manifold vacuum.

I suspect that, for each combination of the two, there are several driving conditions that can reproduce them, with slightly different calibration requirements which is where you are relying on the main ECU to trim the fuel.

I will have to look at mine sometime. At the lakes if not before. Mine literally hasn't been touched since a couple of weeks after I converted it.

All I know is that the fuel trims have stayed within reasonable limits, so it can't be that bad.

Kevin