OMVL XXL ECU issues - workaround?

[himselfunknown]

I have an OMVL XXL system fitted on my 3.0 V6 Cavalier. After fitting the kit, I noticed a misfire on one cylinder. Following some initial attempts at diagnosis, today I took it to an LPG specialist, who determined that the problem was a lack of injector pulse from the ECU. The guy said that this is a common fault with the OMVL units.

I need to double check that I've got the wiring spliced into the car loom correctly (to make sure the lack of pulse isn't being caused by lack of signal from the car ECU). However, I'm 95% certain it's wired in right.

If this is the case, is it time for a new ECU, or is there a potential work around? I'm sure in the past I've heard of splicing into the lead to another injector that fires at the same time as the faulty injector (ie two injectors being fired off the same pulse from the ECU). Is this a potential work around, or a flat out bodge? If it's a legitimate work around to avoid the cost of ECU replacement, how do I determine which cylinder to take the pulse from?

I really want to avoid replacing the ECU if I can, as I've done a really good job of fixing it to the bulkhead and then burying it beneath lots of stuff as I rebuilt the car!

Any help or advice greatly appreciated please.

[rossko]

Dream XXI presumably.
Doubling up injectors on single output channel usually ends in tears.
There may be a way to use the unused cyl 7/8 channels, it depends if the firmware version in use complains about missing cyl "N" lower down in the order. Otherwise you could try paralleling the petrol injector input for N and 7, but there is a risk that the emulator will allow enough petrol drive through to mess up. That in turn could be circumvented by lifting the emulator resistor inside the ECU.

What does your kit supplier advise?

[LPGC]

I'm betting this isn't a particularly new system...

Older AEB ECUs (Dream XXI is AEB) only read petrol injection pulse from the first cylinder of both cylinder bamks anyway (the blue wires), then every LPG injector gets the same pulse period as the first LPG injector on that bank, only with pulses on other cylinders spaced according to engine rpm... So if you plugged LPG injector C into socket D, with an old enough ECU it will work anyway - pulsing the injector for the correct duration but with an incorrect pulse start time for the relevant cylinder (then again they get pulse start time wrong anyway).

As Rosko implied,. the above would only work on older AEB ECUs, and depending on firmware you might also have to disable error reporting.

Another point about these older ECU's - If you wire red, green, yellow petrol injector wiring to petrol injector positive by mistake, then it may still run OK on gas and petrol but you wouldn't necessarily be able to switch back to petrol - press the button you just carry on running on LPG until the engine is restarted!.

Simon

[himselfunknown]

OK gents, thanks for the replies. Sorry it's taken to get back to you, I've had other automotive woes beside this.

Rossko, the guy who did the diagnostic told me the system is running early firmware, which I'm assuming is a good thing for a potential work around for this.

I can see how I might be able to use the 'spare' channel to get a pulse to the injector, but I'm not 100% sure how to achieve it. Please bear with me here.

I have another look at how the system is currently set up. Here's a rough diagram:



So the signal for cylinder 2 is the problem; it's currently where it is on the injectors as I'd previously swapped it with the injector for cylinder 4 to rule out injector issues.

Now, are you saying that the ECU takes the signal from the car ECU from IP5 (the input from the petrol injector) and the whole Bank 2 is timed from this? So, will I be able to get away with plugging in connector B4 into the LPG injector for cylinder 2, and it will run OK?
Or do I need to disconnect IP5 from cylinder 2, and reconnect IP6 to cyl 2, IP7 to cyl 4, and IP8 to cyl 6, and B2>2, B3>4 and B4>6 respectively?
Or is there another way I need to wire it all in?

Just to note, Bank 1 has one additional wire (red&white iirc), that isn't present in Bank 2.

Sorry to be a pain, but I want to make sure I'm 100% sure what I'm doing before swapping things around, as I want to get it right first time as breaking into the injector loom is going to be a pain as it's an inlet job off.

Thanks again for the help and advice.

[LPGC]

Now, are you saying that the ECU takes the signal from the car ECU from IP5 (the input from the petrol injector) and the whole Bank 2 is timed from this? So, will I be able to get away with plugging in connector B4 into the LPG injector for cylinder 2, and it will run OK?
Or do I need to disconnect IP5 from cylinder 2, and reconnect IP6 to cyl 2, IP7 to cyl 4, and IP8 to cyl 6, and B2>2, B3>4 and B4>6 respectively?
Or is there another way I need to wire it all in?

Just to note, Bank 1 has one additional wire (red&white iirc), that isn't present in Bank 2.

It may be possible to simply swap gas injector B2 to the B4 plug without swapping any petrol injector wiring. Whether will depend on the age of the ECU. Since the installer told you it is running early firmware it would seem yours is an older ECU and therefore this should be possible. Sometimes when this is done, better results can be had by swapping gas injector plugs around to account for engine firing order / LPG injector firing order differences. Be advised that very often if one gas injector output channel is broken, another gas injector channel can also be broken, this due to the interdependent design of the injector driver circuitry. Also, just because you get a pulse at the gas injector and the engine runs like that doesn't necessarily mean the driver circuitry is working properly - If you struggle to get it calibrated properly following the above, it can be because the peak or hold component of the pulse is missing...

On later ECUs you would need to swap petrol injector wiring and disable error reporting. Even with this done you may find software shows constant zero Pinj and Ginj, but that won't effect the running.

In either you may find you need to disable sequential changeover and set changeover rpm to around 1600 in deceleration to prevent rough running on changeover.

Simon

[himselfunknown]

Well I've finally got around to looking into this problem. I did a continuity check on the loom and it checks out, so the problem is in the ECU. I think I'm going to plumb of r a replacement ECU as the car is to be my daily driver and I want reliability. I've been told that the AEB AEB2568D ECU is a direct swap for the OMVL ECU (and is £40 cheaper). Does anyone know if this is correct, or will I have to try and source an OMVL unit (out of stock most places).

[LPGC]

Could use any Bigas, Zavoli, Romano, Emer, King, AEB ECU as long as AEB2568 is on the back. All are produced by AEB and all of these 8 cylinder units will have AEB2568 on the back. King may be cheaper still than AEB.

Have you tried simply connecting gas injector plug D to gas injector B? On early AEB (including OMVL) systems this would at least give an appropriate length pulse to injector B, as the early units were not truly sequential - they only measured pulse length on channels A and E so BCD got the same length gas injector pulse as A, FGH got the same pulse length as E, regardless of number of cylinders set in software and BCDFGH wiring to petrol injectors. If this works (and it's a long shot because by D suffix ECU's i.e. aeb2568'D' the above might no longer be true), the thing that could still cause problems with fuelling on B is that gas pulses are still sequential (although inputs BCDFGH are ignored so the system cannot be called truly sequential, gas injectors are pulsed in turn according to engine firing order), so B might get it's dollop of fuel at the wrong moment if connected to channel D (a situation that can sometimes be improved by swapping gas injector plugs around). If no pulse on D, could try swapping channel B petrol injector wiring for channel D or wiring petrol injector wiring to B and D (and maybe H to F) in parallel. May need to select 8 cylinder install instead of 6 and/or disable error reporting and/or disable sequential changeover.

First double check B wiring is connected properly to petrol injector negative pulsing wire (as opposed to the positive wire), striped to ECU side, none striped to petrol injector side. Though having said that, I've had a few looms (both injector break looms and ECU looms) over the years where some of the striped/unstriped wires have been the wrong way around in the loom! Was a time when there were some looms around with a purple wire instead of one of the red wires, these seemed particularly likely to have incorrect wiring.. and injector 2/B is the red wires in AEB looms... Worth checking before buying another ECU...

On older ECU's, if you connected injector break wiring incorrectly (on any channels except A and E), you could end up with a situation where the engine would start and run as normal on petrol, would switch to gas and run something like OK on gas, but would then not allow you to switch back to petrol even by pressing the switch!

Simon

[himselfunknown]

Well I went and bought an ECU today, fitted it, and there's still a problem. It's failing to complete auto-calibrate, coming up with an injector error:





Based on what's been said, am I right in thinking that it's a wiring issue I have? Even though all the wiring it continuity checking OK, one or more wires are crossed over or something?

One thing I'm confused about, is that I used the function that lets you turn off individual gas injectors to individually turn off each injector in turn. Autocalibrate failed every time. I would have expected it to run right when I turned off the dodgy injector?

[LPGC]

Firstly, you didn't leave any petrol injector wiring or LPG injector wiring swapped about after fault finding with the other ECU did you? Just thinking there was talk of using a different ECU channel..

You may actually have a dodgy LPG injector rather than a wiring issue? Swap plugs between LPG injector 5 and another LPG injector to see if the fault moves with the injector or with the wiring. Injector 5 should be on channel E, so maybe swap E and F plugs around.

You're assuming that a channel (with a dodgy LPG injector or wiring) switched back to petrol won't still run diagnostics on that channel, and assuming that autocalibrate won't switch that channel to LPG anyway.. Been so long since I used autocalibrate that I'm not certain if either assumption is correct, it would seem at least the former is incorrect, I think the latter is correct. I seem to vaguely remember plugging in a known good injector (just loose under bonnet with no gas pipes connected) to prevent one of these ECUs picking fault with a known faulty injector coil even when that channel was switched back to petrol in diagnostics / injector check screen (to allow it to run on gas with diagnostics enabled with otherwise broken injector coil - I wanted diagnostics enabled because I suspected another component was broken on the same install).

Prevent the error causing switchback to petrol by disabling diagnostics (untick the 'enable diagnosis' box).

Maybe the original diagnosis was wrong - Recent info makes it seem likely the fault was always a broken LPG injector rather than lack of petrol injector signal.. If your old ECU didn't show petrol injector duration in diagnosis screen (your old ECU may have been too old to do this), did the installer (who advised lack of petrol injector signal fault) fit a more recent ECU for his diagnosis or use some other method to make the determination?

Did you swap LPG injector plugs around to check them with the other ECU fitted? Make sure there are no bent pins in injector sockets / plugs.

Simon

[himselfunknown]

Firstly, you didn't leave any petrol injector wiring or LPG injector wiring swapped about after fault finding with the other ECU did you? Just thinking there was talk of using a different ECU channel..

You may actually have a dodgy LPG injector rather than a wiring issue? Swap plugs between LPG injector 5 and another LPG injector to see if the fault moves with the injector or with the wiring. Injector 5 should be on channel E, so maybe swap E and F plugs around.

You're assuming that a channel (with a dodgy LPG injector or wiring) switched back to petrol won't still run diagnostics on that channel, and assuming that autocalibrate won't switch that channel to LPG anyway.. Been so long since I used autocalibrate that I'm not certain if either assumption is correct, it would seem at least the former is incorrect, I think the latter is correct. I seem to vaguely remember plugging in a known good injector (just loose under bonnet with no gas pipes connected) to prevent one of these ECUs picking fault with a known faulty injector coil even when that channel was switched back to petrol in diagnostics / injector check screen (to allow it to run on gas with diagnostics enabled with otherwise broken injector coil - I wanted diagnostics enabled because I suspected another component was broken on the same install).

Prevent the error causing switchback to petrol by disabling diagnostics (untick the 'enable diagnosis' box).

Maybe the original diagnosis was wrong - Recent info makes it seem likely the fault was always a broken LPG injector rather than lack of petrol injector signal.. If your old ECU didn't show petrol injector duration in diagnosis screen (your old ECU may have been too old to do this), did the installer (who advised lack of petrol injector signal fault) fit a more recent ECU for his diagnosis or use some other method to make the determination?

Did you swap LPG injector plugs around to check them with the other ECU fitted? Make sure there are no bent pins in injector sockets / plugs.

Simon

Simon, many thanks for the input. I'm pretty sure it's not a dodgy injector as one of the first things I did was to swap across the connector and hose between two injectors - the problem followed the connector and didn't stay with the injector.

Today I've been having a good look at the wiring and was beginning to suspect that in the past (this is not a new system), wires have been mixed up or marked up wrong as on bank 1 the connector with orange and black wires is in use, but on bank 2 is unused. Similarly on bank 2 the connector with black and red wires is used, but is unused on bank 1. Unfortunately I can't find a wiring diagram for the injector connectors anywhere, so am unable to confirm what colour wires should be going to each injector on each bank. I don't want to start randomly swapping connectors about as the possible permutations are endless!

[himselfunknown]

This is a screenshot of when it is running on LPG:



Swapping around the connectors makes no difference: the same error code still comes up.

[LPGC]

If that's with the new ECU then this points to fault being with the blue/blue with black stripe petrol injector break wires not wired up properly for channel E.

But also check where the red with white stripe (ignition on) wire is connected. If it is connected to the positive side of the same petrol injector where the blue/blue white wires (mentioned above) connect, move it to another petrol injector positive (in fact, move it straight to battery live first just to rule out the problem then move it to another petrol injector + , coil + or indeed ign +). A few vehicles are a bit quirky regards where the red/white wire is connected, early 4.7V8 Jeeps being one example.

The injector break looms will both contain a red with white stripe wire, of which only one or both may be connected at the engine (ignition on signal). But in the LPG ECU loom only the multiplug for channels ABCD has a corresponding red with white stripe wire... Connecting only the red white stripe wire in the break loom for ABCD (not connecting the red white in break loom for EFGH) would mean that swapping the multiplugs over would result in the LPG ECU not seeing ignition on so it wouldn't run on LPG (the switch wouldn't even light up). Connecting up the red/white in both ABCD and EFGH break looms would mean that swapping the multiplugs over the LPG ECU would still see ignition on, so the switch would still light and the engine would still run on LPG - but now the LPG ECU gets ignition on signal on the red and white wire on bank 2 EFGH... and if the red white on bank 2 is connected to E, this could be your problem. Still a long shot though.

Simon

[himselfunknown]

Simon, thanks again for the input. You've given me a few more things I need to check. I've already checked the continuity from the injector plug to the lpg ECU and it's fine. I'm pretty certain the white/red wire is going to the other bank, but I'll check this.

[LPGC]

I just edited my above post to be a bit more explanatory / useful.

Besides the highlighted error for cylinder A on bank 2 in your screenshot there's another thing that's striking - Most of the other numbers don't seem very similar to each other... Would expect ABC on bank 1 to be similar to each other and ABC on bank 2 to be similar to each other.

You have 2 ECU's now, do both ECU's allow you to see injector durations or just the later ECU?

Simon

[LPGC]

Another thing.. Select '2 banks' in MAP or Lambda screen (whichever of which you see the option).

Simon

[himselfunknown]

If that's with the new ECU then this points to fault being with the blue/blue with black stripe petrol injector break wires not wired up properly for channel E.

Yes, this is with both ECU's. I've checked that the blue/blue & black wire goes to cylinder 2, and that the right blue wire goes to the right 'side' of the cut injector wiring. I've also done a continuity check from the petrol injector connector to the LPG ECU connector - zero resistance.

But also check where the red with white stripe (ignition on) wire is connected. If it is connected to the positive side of the same petrol injector where the blue/blue white wires (mentioned above) connect, move it to another petrol injector positive (in fact, move it straight to battery live first just to rule out the problem then move it to another petrol injector + , coil + or indeed ign +). A few vehicles are a bit quirky regards where the red/white wire is connected, early 4.7V8 Jeeps being one example.

The injector break looms will both contain a red with white stripe wire, of which only one or both may be connected at the engine (ignition on signal). But in the LPG ECU loom only the multiplug for channels ABCD has a corresponding red with white stripe wire... Connecting only the red white stripe wire in the break loom for ABCD (not connecting the red white in break loom for EFGH) would mean that swapping the multiplugs over would result in the LPG ECU not seeing ignition on so it wouldn't run on LPG (the switch wouldn't even light up). Connecting up the red/white in both ABCD and EFGH break looms would mean that swapping the multiplugs over the LPG ECU would still see ignition on, so the switch would still light and the engine would still run on LPG - but now the LPG ECU gets ignition on signal on the red and white wire on bank 2 EFGH... and if the red white on bank 2 is connected to E, this could be your problem. Still a long shot though.

Simon

The red/white wire goes to the positive on cylinder 1 (the other bank), and pairs up with the 9th connector pin on the main loom. The red/white for bank 2 is not connected, but there is no corresponding pin on the main loom. Swapping the ten pin connectors around causes the car not to start at all.

[LPGC]

Two threads about same car on forum (this thread and thread in the link) http://www.lpgforum.co.uk/viewtopic.php?f=28&t=14053

Seen Himselfunknown today and sorted it! I was wrong about only taking 30 mins though, took me over 90 mins...

A few issues identified and totally sorted or identified and workaround effected (one issue seemingly caused by an internal fault of the original ECU, owner had a replacement ECU already but would rather return it, a workaround was effected using the old ECU).

1. System vacuum pipes connected to wrong side of heater water flow shut off vacuum feed solenoid, meaning the LPG system could only see actual engine vacuum with heater turned to full cold. Vac pipes re-routed to cure this issue.

2. Seems someone (before himselfunknown) had previously tampered with the loom between the LPG ECU and it's bank 2 multiplug, they had swapped the blue and blue with black stripe wires around so the system lost petrol injector pulse on bank2 channel A when running on LPG. The blue and blue with black wires were switched (again, near the multiplug this time) curing this issue.

3. With the new King ECU the system would now work entirely properly (though in need of full calibration) but with the original OMVL ECU fitted the LPG injector on bank1 channel C did not pulse or provide any gas for that cylinder. However, the OMVL ECU pulses bank1 channel D for the same duration as bank 1 channel C, so with channel D plug connected to LPG injector on channel C the engine runs on all 6 cylinders OK (*more on this below). With the engine idling nicely on LPG (LPG injector on bank 1 channel C connected to bank 1 channel D) I connected another injector to channel C without gas plumbing to listen to the injector to see if it was clicking as would expect (or wouldn't expect in this case expect). The other injector clicked but very quietly on channel C but when connected to channel D it clicked as expected - so either there is a problem with the LPG injector driving circuitry within the OMVL ECU for bank 1 channel C or there is an intermittent fault with the loom/wiring for channel C. There were some joints in the wiring for LPG injector output channel C which were cut out but still the injector didn't work properly when connected to that channel. I suggested we could further confirm the fault was within the OMVL ECU by again swapping in the King ECU but the results were already seeming pretty conclusive and Himselfunknown didn't want me to 100% confirm... and it does seem pretty conclusive that channel C LPG injector output on the old ECU is malfunctioning, even without checking with my oscilloscope.

4 (though more of a calibration issue than outright problem). The config of both ECU's was using a reference pressure of SP (standard pressure / 0.9bar) while actual pressure was 1.1 bar. At idle petrol injector duration was at around 2.8ms with same fuelling from LPG injectors at 4.5ms. Numbers in the maps were from around 160 at 3ms to above 200 at 4.5ms. I changed reference pressure in the fitted OMVL ECU to 1.2bar, so now numbers in map are more within the range that will give good results (130's etc) and increased actual pressure by winding the reducer up to 1.3 bar, bringing LPG injector duration down to around 3.6ms at idle. I asked Himselfunknown if he'd like me to go out with him in the car so I could calibrate the system but he chose to calibrate it himself based on my advice on how to do it. Without going for a drive in the car I set the map to something like what I'd expect to work, so as to give Himselfunkown a basic map that should work something like OK to use as a starting point.

*'More on this below' bit - The OMVL ECU (of this age / design / firmware) shows individual petrol injector duration in the diagnostics screen yet the LPG injector pulse durations are all calculated from only channel A petrol injector durations (per bank of cylinders). This is why connecting channel D LPG injector plug to channel C LPG injector still makes the injector work when there is no petrol injector pulse seen by the ECU for channel D and even though 6 cylinder engine is selected in software (on a 6 cylinder engine channel D petrol injector inputs are not connected and channel D LPG injector outputs are not usually connected, ABCD are used on both banks only on a V8 install). The later King ECU calculates LPG injector pulse for each individual LPG injector output channel based on each individual petrol injector pulse, so the King ECU will not pulse channel D at all because it will not see a petrol injector pulse on channel D. This means that with the King ECU fitted LPG injector plug C will have to be connected to LPG injector C, because if plug D is connected to LPG injector C the injector will not be pulsed and there will be a misfire on that cylinder...

The newer King ECU waits until it receives a petrol injector pulse on a channel before it pulses the corresponding LPG injector on that channel, furthermore each LPG injector pulse length is calculated from the pulse length of it's corresponding petrol injector. The older OMVL ECU only uses only the petrol injector pulse on the first cylinder of each cylinder bank to calculate only one pulse duration for all of the LPG injectors (all the LPG injectors will give that same length pulse), but it does attempt to pulse LPG injectors in same order and at same moment (in the injection cycle) as the petrol injection system.. E.g. On a 4 cylinder install with firing order 1342, although each LPG injector would get the same pulse length (based on pulse length of petrol injector on cylinder 1), the pulsing order of LPG injectors would follow the 1342 fuel squirting order and in theory (in theory because it doesn't wait to receive each petrol injector pulse before pulsing each LPG injector but rather spaces pulses out according to rpm) at the same moment in time as the petrol injectors would squirt. Given this, if we now imagine swapping LPG injector plugs C and D the fuel squirting order now goes 1432 instead of 1342... In effect we have advanced the squirt order for cylinder 4 by 1 injection sequence (180 degrees of engine rotation) but we have retarded the squirt order for cylinder 3 by 3 injection sequences (540 degrees of engine rotation). This wouldn't be a problem on a steady cruise with unchanging throttle position (and particularly not a problem at higher rpms where changes in engine load due to throttle movement are less different over multiple engine cylinders than at lower rpms) but at low rpm with quickly changing throttle position the petrol ECU may notice quickly changing engine load and give each cylinder a different injector pulse length to account for the changing load (amount of air entering the cylinder), and on more recent design engines that run 'emulated Atkinson cycle' (forcing some of the charge including fuel back out of the cylinder via the inlet valve during compression stroke instead of trying to trap all the charge)... probably won't be a problem for cylinder 4 but cylinder 3 may receive a fuel mixture which is too incorrect for that cylinder to fire properly, leading to drive-ability problems. I haven't looked into firing order of the Cav's V6 engine to find how connecting plug D to injector C will affect running, it may have an effect (good or bad) or may make an unnoticeable difference, but there will be a difference in the point at which LPG injector C on that bank pulses. Where swapping injector plugs about has a positive effect it is usually due to some other shortfall in the system - Such shortfall could be too long injector pipe lengths, bad calibration, the LPG ECU not following the petrol system injection sequence, or related to how the LPG system addresses enrichment in acceleration... Where an LPG system only reads petrol injector pulse from only one cylinder on a bank of cylinders it needs some way of compensating fuelling for the other cylinders during acceleration - Hence the 'enrichment in acceleration' slider in AEB software, which is a handle to control how much compensation is done. The slider is still present in recent AEB software / systems, but is now nowhere near as useful as it was on older systems because newer AEB systems are truly sequential (use pulse times measured from each petrol injector to calculate each relative LPG injector pulse duration). With a truly sequential ECU there is less need for such slider because by default it will give the correct amount of fuel to each cylinder during acceleration because it is following just what the petrol system would do. Points made above are also the reason why 'anticipate the injection sequence' box had to be ticked on older AEB based systems on 4L Jeeps to prevent harsh autobox gear changes and why misfires on Mercs (which on some Mercs quickly put the MIL light on and turn off all fuelling on the misfiring cylinder until after engine restart) would continue to run on the effected cylinder on LPG because even without a petrol injection pulse the effected cylinder would still receive LPG fuelling (as long as the misfire wasn't on the first cylinder on a cylinder bank, in which case none of the cylinders on that bank would run on LPG!) but when switched back to petrol the misfire would return.

Simon

[himselfunknown]

Thanks Simon for having a look at it for me and getting it going for me, I really appreciate it!

It went pretty well on the way back with the basic map you did for it. Still undecided whether to stick with the old ECU or put the newer ECU on it and benefit from all the additional functionality. Decisions decisions! But at least now it's running on all 6: a vast improvement!!

[LPGC]

Very welcome, I'm glad we got you sorted.

If you can get your money back on the new ECU and it runs as smoothly (including during acceleration) with the old ECU (with the dead channel) then you might decide to stick with the old one?

Whichever ECU is used it will need at least calibration checking - Method I advised during your visit and either with ECU lambda connection wired up or a multimeter wired to lambda.

Simon

[Tinleytech]

For info, the above description regarding the function of the 'enrichment in acceleration' slider is fundamentally wrong - please see below direct from the AEB software guide (apologies for the rather poor English), this also calls into question (as mentioned previously) Simon's persistance that the AEB ECU is not truly sequential - which it is and has been for many years :

4.6.6 Enrichment in acceleration
Many engine management units have transient enrichment of petrol injection, during
accelerations. Sometimes this causes jerking or hesitation, on gas. You can fix it with this filter:
· By default the filter is defeated, with its fader all the way right; in this position, the petrol
transient is copied to the gas injection, applying all the enrichment.
· As you move the fader to the left, the Dream XXI-N ECU will follow the petrol transient
slower and slower, thus applying less enrichment to the gas injection.
Whenever the enrichment is filtered, the box of the filter will glow in red, on the screen.