AC Stag 300 ISA2 on 3.5l Pajero/Montero/Shogun-calibration advice

[LPGC]

I watched the video, riveted to my seat like you said

If the plotted points and lambda readings are anything to go by (and they are a fair indicator) it seems calibration and fuelling was fine in the conditions of your run in the video.. looking a lot better!

You didn't click on 'clear the gas map' before the run so the plotted points and the line it draws between plotted points will take time to change during the run. Watching the position of the crosshairs at around 12ms it seems if the run were longer they would eventually match the plotted petrol points so I don't think you've overdone any adjustment you made at 12ms.

Throughout the test the engine was running in closed loop mode (or at least most likely was) because lambda flicks all the time during the test and engine rpm (and possible engine load / manifold pressure) probably isn't high enough for fuelling to switch to open loop mode. If you put your foot down at high rpm it will run in open loop mode, you should check/set multiplier to give rich but not too rich mixture under those conditions - You may find pinj increases to a bit above 12ms as the engine comes more 'on cam' at higher rpm, so you may have to change both the 12ms and 16ms multiplier points (and if you change the 16ms point it would be good practice to 'follow on' and anticipate/guestimate the shape of the line towards the multiplier point at 25.5ms). Going only on the video (haven't seen readings at higher rpm higher engine loads) might suggest dropping multiplier at 10ms by a point and at 12ms by a couple of points, but would be better to see higher rpm readings first.

The shape of the map now (in your video) is a lot more like the shape I guessed than the shape in your last screenshot above

What rpm correction figures do you have dialled in now (during the test)? Is temp correction still a flat line or did you adjust it?

At around 50seconds rpm is around 1100, pinj is 1.9ms, ginj is 3.5ms. The 3.5ms is a bit low for these injectors - During engine warmup from cold under no engine load conditions if you hold the engine at fast idle does it run OK?

Depending on answers might suggest seeing if you can turn pressure up a bit, though unless it's a MJ Extra reducer (usually adjustable up to 1.7bar) or a very recent MJ compact reducer (those produced in last few months have same range of pressure adjustment as Extra, earlier ones max out at around 1.35 bar) I expect it will already be set at just about it's maximum pressure.

When the engine is fully warmed up if you hold fast idle (1100) and switch between petrol/LPG, LPG/petrol does the 1.9pinj increase or decrease? Does lambda voltage hang low or high for a moment?

[disco stu]

Thanks for taking the time to watch that, greatly appreciate it.

I did see that as I shifted multiplier that it was becoming more and more pretty much exactly what you predicted-I was impressed by that! Obviously know your stuff.

One thing I forgot about (happening too much lately!) Was that I put the temp correction in that you recommended before leaving work the other day, and it was after driving home that the gas map had changed to lean above 10ms. That might have been cause of the change there, but not certain.

Rpm correction is what you recommended a while ago. I'll grab a shot of that tomorrow if you want.

The Pinj being 1.9ms and rpm at 1100 would have been me coasting down for a corner. Idle pinj is around 3ms so I must have been off the pedal slowing down, time fits with that corner also.

Engine runs fine at all temps at all rpm. Since drilling out the nozzles it also switches to lpg much smoother, used to lag and slightly miss just a wee little on switching and then smooth out. No longer does that and you can't even feel it.

I'm pretty sure I've had pressure on this reducer up to at least 1.5, maybe more. I know I had to drop it down is all I can remember. Reducer is Magic 3.

I'll check lambda and pinj changes tomorrow. Almost midnight here now.

Also, I did get video of switching between lpg and petrol under various loads this afternoon. I'm still going through the video to check, if it did change the pinj maybe raised a little on switching by around 0.7ms. All under load so pinj was like 8ms. I'll finish checking it and put some figures up. Not sure if I'll bore you with that one!

Thanks again, you've been a massive help

[LPGC]

All good

Another thing I'd suggest is when the engine is fully warmed up clear both gas and petrol map and drive around a bit on both fuels to see if the new plotted points and lines still match up.

[disco stu]

Cheers. Will do

Just going through the video. When manifold pressure and RPM stay fairly constant over the change of fuels, pinj time is increasing a bit. It will go from 6.0 to 6.3, 8.5 to around 9.2, if that gives some idea. There are other times where it doesn't change, much if at all. And given that I'm driving on the road I have to adjust to the road.

That sound like big enough difference that things need changing?

I'll check those other things soon

[disco stu]

Just checked Pinj with engine warm at 1100 RPM. On LPG Pinj is at around 2.7-2.8, switching to petrol Pinj goes to 3.0-3.1, RPM drops a bit also incidentally. Lambda drops down to basically nothing on switching over to both fuels, stays low for a second or 2, then goes back to swinging rich to lean

[LPGC]

What rpm correction figures do you have dialled in now (during the test)? Is temp correction still a flat line or did you adjust it?

[disco stu]

Temp correction is to what you recommended. Image of RPM and temp should hopefully attach below. Gas temp at calibration was 43deg, closest option was 45. Sorry, forgot to put these up earlier

[disco stu]

Just filled with lpg. Consumption on the last tank was 14.4l/100km, so it has dropped right down from the 18 where it was when O2 sensor was crook. With 12.5 on petrol it is now 14.4% higher consumption on lpg, which I gather is right on expected increase for a proper running system. Much happier with things now

[LPGC]

Seems you've definitely got it set up a lot better than it originally was now... both the engine / petrol system (by fixing the lambda sensor issue) and the LPG mapping.

You've said when you switch from petrol to gas the pinj reading increases from 6 to 6.3, 8.5 to 9.2. Would advise checking for any changes at other pinj points too - If pinj rises when you switch to LPG increase the multiplier at that point a little, but you should still expect the general map shape I advised. Worth saying though that when I advised that map shape I overlooked you have the V30 injectors fitted, they're a relatively unlinear injector, when injectors are less linear it can move the peak area of the map to the right a little and extend that peak a little further to the right... So you many find you only need to move the points starting at 6ms up a little but still check them all. If it's an auto (I forget) and you drop it in drive with the engine fully warmed up you may find that pink falls a little on gas compared to on petrol, we could dial this out using rpm correction but if this point seems in the right place when rpms are higher than idle it will be OK to leave the point where it is.

I asked if you'd entered the rpm correction figures because if those figures were all zeros it might make it seem you'd need to move the higher pinj load points to a higher position than you really do.

Just to explain that sudden rise in the temp correction chart at the extreme left (cold) end - The system wouldn't work properly with gas at -30degC anyway, but the most likely reason for a -30degC gas temp reading would be if the gas temp sensor were broken and open circuit. The sudden rise is there as a precaution, if you do ever get an open circuit gas temp sensor problem if the ECU continues to allow running on gas (doesn't force switch back to petrol due to noticing the open circuit temp sensor) at least the fuelling will still be fairly accurate instead of going around 12% too much toward lean fuelling

[disco stu]

Thanks, you've definitely got me pretty close.

I think I forgot to mention, this car is manual.

That rise in injection times was a trend, but it didn't happen every time. I wasn't sure if could just be due to slight changes in load from road angle changing or my foot on accelerator shifting slightly. From what you're saying, I'll go back through the vid I took and check at what rpm it does occur, increase multiplier a smidge in the areas it does happen.

You did actually explain that little tail on the temp correction, made perfect sense that being NTC thermister that failing it would read temp as low as it could go. Neat trick I thought

I'm about to head away with family, so I'll dial these things into it once I get back.

Thanks again, massive help