Blueplasticsoulman visited today.

Initial findings - Fuel trims at idle on petrol were close to zero (bank 2 trims a bit higher than bank 1), fuel trims at idle on LPG went a bit more negative on B1 and a bit positive on B2, No entries were made in LPG mapping screen (only autocal would have been done regards mapping), reference pressure set at 1.2 bar but actual pressure was 1.7 bar. Ginj was 4.5ms at idle which is a bit low duration for these spec injectors to work properly at, so at this point I anticipated the need to turn down reducer pressure.

I could correct the bank trim discrepancy at idle quite easily using a positive bank 2 trim figure and entering a slightly negative value in the idle area of mapping to get both banks trims very close to zero when running on LPG. The LPG ECU didn't support switching individual cylinders back to petrol, which would be a way of checking each engine cylinder's response when running on petrol or running on LPG (*later on I temporarily fit another Tartarini ECU that does have this facility). The ECU did feature sequential fuel changeover and the smoothness of changeover between fuels told me injector wiring / plumbing was correct (so input of petrol injector pulse for a certain cylinder results in gas injector pulse to the same cylinder).

Under the bonnet the Tartarini injectors (very similar to V30's) were quiet. The reducer vac reference pipe was simply hanging below the reducer, disconnected from the vac T, and the vac T had the missing pipe connection blanked. I checked the reducer vac pipe for gas leakage, it was fine, sucked on the pipe still fine and gas pressure went down when I sucked as it should. Reconnected the reducer to manifold vacuum and now reducer pressure was near the reference pressure of 1.2 bar - two problems sorted already (autocal wouldn't have worked well with 40% over reference pressure situation and gas injectors wouldn't have worked well pulsing at less than 4.5ms with colder gas).

At this point it would idle a bit more smoothly on LPG than on petrol, also pulled slightly more vacuum at idle on LPG than on petrol, confirmed by slightly lower MAF readings in OBD2 live data on LPG compared to petrol - If any difference at all it should need a bit more airflow to idle on LPG than on petrol with stoch afr. This points to a minor issue with the petrol system such as a dodgy petrol injector...

We went out and calibrated the LPG system, trims on petrol were all decent, matched trims on LPG to trims on petrol and confirmed by Pinj figures staying the same when switching between petrol and LPG. The original calibration won't have been right (as said the original calibration had only had autocal done), I had to enter figures that shifted within a range of around 20% from the autocal figures, it was previously running rich at idle and lean off idle, at least after I'd connected the vac pipe to the reducer, and won't have been running right with the vac reference not connected to the reducer.

The engine still idled better on LPG than on petrol. *I now disconnected the Tartarini ECU and connected another Tartarini ECU which allowed switching of individual cylinders back to petrol (easier to temporarily fit an old Tartarini ECU than a new say King ECU as the old system uses the old Tartarini style switch which other AEB systems are not compatible with), I only roughly mapped this ECU and only for idle conditions. The slight bank trim issue on LPG remained present, thus helping confirm a few things such as issues wouldn't be LPG ECU related. When I switched any cylinder back to petrol (except for what the LPG system sees as channel C on bank 1) Pinj remained the same. When I switched channel C on bank 1 back to petrol PINJ on bank 1 increased, meaning bank 1 ran leaner when this cylinder was switched to petrol. There is no need for the LPG system to be wired so that what the LPG system sees as bank 1 is the same as what the petrol ECU sees as bank 1, but earlier notes (comparing fuel trims to pinj readings) had confirmed that the installer in this case had wired the system so that the LPG's bank 1 is the same as the petrol bank 1. As long as the installer had wired the system so that channels ABCD ran from A at the front of the engine to D at the rear (which they will have) this would mean that channel C on bank 1 would be the engine's cylinder number 5, the 3rd cylinder from the front on the drivers side. Since fuel trims are more negative on bank 1 on either fuel, accentuated when running on LPG, and LPG vapour pressure isn't lost when running on petrol, this could imply that the petrol injector on cylinder 5 is constantly leaking a bit of fuel into cylinder 5 or that airflow into cylinder 5 isn't as high as on the other cylinders (valvetrain issue). Given the poorer idle on petrol compared to LPG it seems more likely that the petrol injector is a bit dodgy and leaky, else if it was a valvetrain issue would expect idle to be worse effected on LPG. It doesn't seem to be burning any oil etc. Chris is thinking about fitting new rocker cover gaskets, I suggested while the manifold is off he could swap pinj5 with one from the other cylinder bank, a test to see if the bank trim situation when running on petrol is reversed. If it is reversed then the real fix would be to sort out the dodgy petrol injector, but while a dodgy injector is fitted on the opposite bank the LPG calibration and bank trim should be adjusted to suit, I advised how to do this.

With hindsight there was one test that we didn't do - could have swapped the Ginj that feeds cylinder 5 with another Ginj (swapping both electrical connectors and both pipes). Perhaps we didn't do this because Chris had already been here for a long time, all seemed pretty conclusive, we were packing up anyway, and my dad's old best mate who's had several strokes and I haven't seen for a couple of years arrived unexpectedly wheel-chaired by his daughter just after we'd done the checks with the second LPG ECU. If the trims on petrol on B1 were not more negative than on B2 on either fuel then this is a test I would have done anyway, but given all the above I'm very confident this wouldn't have revealed a problem with ginj5 and that everything points to a dodgy pinj5. As said the 2nd ECU was only temporarily fitted to allow the injector test, there was no need to sell Chris any parts, all his LPG components seem in good working order and his system is calibrated much better now.

Simon

Some 4mm pipe will squeeze onto 5mm fittings but not as easily as 5mm pipe will squeeze onto 6mm fittings. The V30's usually have 4mm or 6mm outlet fittings, not always interchangeable... some of those that come with 6mm fittings have a wider diameter machined hole in the rail for wider diameter thread nozzles.

SImon.

Blueplasticsoulman PM'd asking me to read recent posts here. I agree it seems the LPG system needs calibrating, it is also likely to need some LPG injectors if this is an old system and it must be at least a few years old being Tartarini. I'd get to the bottom of it.

Au revoir Gilbert, have I ever mentioned my sister is a French teacher, brother in law is French... and I can just about remember Au revoir? Lol.

Simon

Just quickly scanned through recent posts, seems to me there's a problem with your LPG system.

I'm just South of Pontefract in case you want to come sometime ;-)

blueplasticsoulman wrote:

a bit over my head mate i'm afraid. i'm muddling through and trying to fault find using the advice given.

Tartarini made various types of LPG system, some earlier advice is only relevant to the newer type of Tartarini system which uses pulsing LPG injectors. If you post a pic of your engine bay we can tell you which type of LPG system you have.

Simon

Might need to slow down / backtrack a bit.

I may be wrong but I don't think I've seen a pic of this install and if it's Tartarini it could be a none sequential system such as Etagas / Tec97 / Tec95? Those three systems do need lambda connection - and if purple wire is disconnected (if grey wire is connected) this will break the connection between lambda signal by default. Edit.. If it has black striped purple and grey wires it could only be sequential or Etagas.

In certain conditions some models can read around 0.4v in diagnostics regardless of actual lambda voltage. Such conditions can include cold open loop and fault open loop... but such fault might not actually be a lambda problem and it would be a coincidence if both lambdas broke in a way that made them both output a constant 0.4v. Some petrol ECUs can even output around 0.4v to the lambda signal wire under such conditions, it is the way some older type ECUs fool themselves into seeing a lambda voltage that holds stft's at zero, a sort of lambda emulation built into the petrol ECU. On such systems the only way to read actual lambda voltage with the fault present is to cut the signal wire between the petrol ECU and the lambda and put a multimeter directly to the lambda signal wire.

If it's Etagas and grey wire is connected, the Etagas may be programmed to deliver constant 0.4v on the grey wire.

Simon

blueplasticsoulman wrote:

I literally did my throttle cable today. It was slack. I reckon about 4mm of adjustment. Tightened it up and honest, the car picks up much better. I was only saying before how I thought my other p38 felt faster/sportier or whatever. Can't believe the difference a couple of mm has made. (said no woman ever!) lol

With slack cable you'd have to press the accelerator further to open the throttle the same amount, might not even be able to get to WOT, and with these models having long throttle pedal travel a bit of slack might make for a fair bit of difference to how far you have to press the accelerator to open the throttle valve the same extent. Can't affect TPS though because that sits on the same shaft as the actual throttle flap.

Simon

Agreed with Aragorn on autoboxes / TC's. The TC in my car (Grand Voyager) locks up in top (4th), will lock in 3rd if it's been sat in 3rd for a long while or if the shifter is set to 3. It will lock up in 2nd if the gearbox temp gets very high... When TC's slip they generate heat, too much heat is very bad for autoboxes. I thought about fooling the box temp sensor to make the box lock in 2nd at the press of a switch, would probably help prevent box getting hot when pulling the caravan up that steep incline on the A30... But I'll probably use the ML for towing instead lol, finally reserved a bit of time to work on it and it passed it's MOT the other day.

Engine load figures are fairly abstract - Is 100% load at the red line with full throttle, or is it at full throttle at rpm where the engine makes most power (which could be below red line rpm), or is it at torque peak rpm (which is well below red line) with full throttle? Then there's part loads e.g. 50%, is this at half throttle at the red line, or at full throttle at half red line rpm, or both? Because they place very different demands on the engine, fuelling and ignition timing won't be the same between them... The load figure cannot be used directly for ignition timing or for fuelling. Some LPG ECU's calculate engine load but there is always the disclaimer about it's abstract nature. Some allow you to set a change back to petrol after a certain engine load, but you'd be hard pressed to guess what combinations of rpm and throttle position would set the switchback condition.

A lot of OBD2 compatible cars with MAF sensors show g/s in live data, I take this to be grams per second...Can confirm if grams / seconds interpretations are near correct... An engine of around 1.6litres generally reads around 3g/s at idle when warm, which would equate to 10800 grams per hour, 10.8Kg. Given stochiometric ratio of 14.7:1 for petrol this would equate to 0.74Kg of petrol burned per hour and since petrol has a density of 0.77Kg per litre this equates to around a litre per hour (0.22 gallons per hour) which won't be far off for warm idle for a 1.6. A car with this engine might do 40mpg at 60mph which is 1.5 gallons per hour, thus using 6.8 times as much air (20.4g/s) and fuel to cruise at 60 than sat at idle, which also makes sense.

Simon

Your Bigas injectors will use 4mm internal diameter pipe, V30s usually come with the nozzles to suit the same diameter pipe but can come with nozzles to suit 6mm internal diameter pipe - make sure you stipulate V30s with nozzles to suit 4mm internal diameter pipe and 10mm gas inlets when ordering. Also order a combined inline gas temp sensor / pressure take off like this (http://www.lpgshop.co.uk/12mm-omvl-inline-temperature-sensor-with-pressure-out/). This is listed as 12mm but is more like 11mm and most 10mm pipes will fit, but ask if they can sell you a 10mm one instead before buying. Tinleytech is more likely to be able to supply a 10mm one.

There is another way of going about it - buy V30s with 12mm inlets, use 12mm pipe, use a 2 entry 2 outlet 11mm pipe fitting filter. 10mm pipe then runs between reducer outlets and filter, 11mm pipe between filter and injectors.

4mm Pipe, similar electrical properties, similar injector response and similar physical dimensions were reasons I suggested the V30s.

Simon

Partly off subject but I recently bought another Grand Voyager. I'm in Yorkshire, the seller was in Derby, I only went to view because my son was going to London that day so could drop me off en-route, and I could catch the train back if I didn't buy. I sussed the misfiring was due to the jetwashed plug leads (nice electo-storm display peaking under the partly closed bonnet), that it needed a drivers side front wheel bearing and that the heater zone control was stuck to defrost due to broken teeth on the heater box.. I paid half the asking price which was already half the going rate and nursed it home like that, next day had it all running perfectly because I already had the parts to chuck on it from another car lol.

Simon

No probs mate, yes get in touch if you want to bring it in.

If you're going to download software from AC you should go for V11.2.0.7, it's the only PC version on Stag's site that should work with your system.

If this software connects it will probably ask if you want to update firmware, don't update firmware.

No point the installer giving LPGShop control over your PC if the problem was the physical connection between your PC and the LPG system lol. £90 to give the installer the opportunity to demonstrate their incompetence.

Simon

Possible you have a dodgy injector, in which case would most likely be on bank1, but neither is by any means certain.

I suppose you could do the stethoscope test, bit of narrow pipe in ear while holding open end to each LPG injector in turn, see if any injector(s) make a different noise to the majority of injectors, not a conclusive test but can give some insights about condition of injectors. / Swap injectors on sides of the engine, see if what's happening with trims now goes the opposite way after moving them.

Simon

Thanks to those who've mentioned me above... Dazer, I'm the Simon mentioned.

Stag software I keep installed are V11, V10, V7, V2, V1 and Qbox V0.16, with those versions can connect to any Stag labelled sequential system (and Stag clones, and other systems that use an interface with compatible pinout). All of the later versions should connect to ISA2, would start with V11 and go back through the versions I listed if you have problems connecting but if you get to V7 on my list you might as well give up trying with the lead you're using.

This is one of the best Stag compatible interfaces (http://www.lpgshop.co.uk/ac-stag-usb-ftdi-diagnostic-interface/)

Simon

Unlikely I know, but a dodgy TPS would have potential to mess up both gear changes and fuelling..

Likely that the connection issue is as Gilbert said, wrong cable, or the installer might have tried to use wrong Stag software. Some installers that recently started fitting Stag may only have Stag Qbox software, or installers that dabbled with Stag in it's early days may only have older Stag software, neither of which are compatible with ISA2, Some connection issues can be sorted as easily as pulling the LPG system fuse and putting back in. If the installer didn't know what cable or software to use for such a common system I wouldn't be very confident of their abilities...

A lot of installers who fit Stag hardly bother to address pressure and nozzle size. For any type of injectors selected in software the Stag will suggest a minimum allowable pulse duration, sometimes this can mean running rich at idle and during over-run (but the real issue in the case of a P38 would be pressure / nozzle size). Most installers who fit Stag don't bother to do a proper manual job of calibration, instead they rely on the system's auto-tuning facility... This doesn't work well in the best of circumstances but if the vehicle develops a fault (like a broken lambda) the autotune can really mess up calibration if left enabled.

Simon

Yeh, in simple terms the higher pressure compensates for smaller nozzles, if you look at it in a bit more detail it should change the shape of the map in the low load area more than the high load area - but would have been best to re-calibrate anyway when fitting new injectors.

Simon

I know they will be far more familiar with Yank stuff, but not sure if they'd balk at the thought of rebuilding a German autobox.

Reckon you'd probably only really need 3rd gear on a 3spd auto in most muscle cars, top speed only maybe 110mph in 3rd due to gearing even then. I used to love the Hill St Blues opening scene with a line of police cars all burning rubber out of the station, smoking tyres in every gear. My mate used to reckon he had the fastest car in town until I took him out in my Cosworth years ago... but he told me about the time he tried to race a TransAm from the lights...#

I've converted plenty 500ci engines, plenty torque in them!

Simon

Hate to say it but there might be more info on an American website.. In the UK autoboxes are considered a black art but in the US many home mechanics will have a crack at rebuilding them, probably because the info on autoboxes is much more readily available, there are chain stores of autobox rebuilding firms etc... just pop into a shop any buy a rebuild kit for a gearbox. I've delved into building them myself but it's a lot of faff and there are very specific tolerances.

Simon

With the injectors you've got I'd expect optimal pressure to be between 1 bar and 1.1 bar, but the installer probably left pressure set at the Bigas standard of 1.2 bar.

3mm Nozzles will flow 1.44x as much gas as 2.5 nozzles, since even V30 injectors will be working within spec at 4.5ms I would set pressure at 1..6 bar and adjust from there if necessary... but 1.6bar will work and the Bigas twin reducer will go to above that pressure.

Calibration will need a tweak anyway following fitting different LPG injectors, especially of a different type with a smaller nozzle size. If you left the old LPG injectors in place and they were working OK, fuel trims while running on LPG wouldn't be effected by changing petrol injectors - though it is possible to cause problems if fuel trims are very different when running on LPG versus running on petrol. I've never tried to look up info on specs of P38 injectors versus K series injectors, they'd have to be a fair match for petrol trims to be anything like correct when running on petrol and tbh I think they won't be that far wrong.

Simon

Yes it will mean 3mm nozzles.

In which case you could still fit Valtek type 30 rails but would need to increase reducer pressure and do a full recalibration. There are two allen sockets, one on each side of the reducer, alternate adjusting them in turn while watching pressure readings in software because you want them both to be fairly equally matched. If pressure from the individual reducers isn't well matched what happens is one reducer does all the work until it can flow no more (when you put your foot down) and then actual pressure suddenly falls to the setting of the lower pressure reducer.

The V30s are still a decent bet for a cheap no hassle fix because they're available with outlets to suit 4mm pipe (Bigas has 4mm outlets) and have very similar open/close time characteristics to Bigas. If your Bigas injectors had 2.5 stamped on them you could probably have got away with doing a straight swap without even connecting a computer and it would run at least as well as with the old injectors. .

Not all types of Bigas injector are available anymore (I still have some working ones of each type but they're old), the V30s are a better match for your Bigas injectors than the newer type Bigas injectors. New type Bigas are £100+vat for 4, you need 8, V30s are £35 including VAT for 4 but you will need to add a combined inline temp sensor / pressure T (easily fitted into piping) which is about £10 and will need the interface to recalibrate.

Simon

Orangebean wrote:

Now this is where the current job has the potential to get silly. Idly sitting planning my day- the thought creeps in...
" Really should drop the sump to clean all the crap out. When the sump's off and heads off it would be really easy to pop the pistons out and re-ring them, and of course with conrods out a new set of big end shells would be great preventative maintenance. If I did big ends, may as well do mains".
I'm my own worst enemy sometimes!

Might as well take the block out at that stage too OB, re-hone the bores, gearbox rebuild etc.. lol