Omega Owners Forum

Omega Help Area => Maintenance Guides => Topic started by: Kevin Wood on 06 April 2010, 12:58:07

Title: Fitting LPG - Commissioning and calibration
Post by: Kevin Wood on 06 April 2010, 12:58:07

Having completed installation of an LPG system, care must be taken in checking correct operation of the system and calibrating it to suit the engine before it is used.

The following is a suggested procedure for commissioning a Stag system installed in an Omega. It assumes as a starting point a completed installation which has not yet been filled with LPG and where the LPG system has not yet been powered up.

1) Check the vehicle still runs on petrol.

With the vehicle completely assembled but the LPG system 12v permanent supply not yet connected (remove the fuse, for example), try to start the engine.

The engine should run exactly as it did before installation, on petrol. If there are any problems at this stage the following should be considered:

• Have all items disturbed been re-connected correctly? (hoses, electrical connections, etc)
• Could an air leak have been introduced into the induction system during removal of the manifold?
• Have the LPG nozzles been connected to the LPG injectors? (otherwise there is an air leak!)
• Have the petrol injector piggy-back connections been made correctly? (no injector signals swapped between cylinders and all injectors connected)
• Have the connections to the Petrol ECU been made to the correct pins and are the cable colour codes as expected?

If anything is wrong, back-track your work until you find the problem. If there is a problem running on petrol there's no point proceeding further with the LPG setup until it is resolved.

Now is also a good time to check for leaks in the plumbing to the vapouriser, to ensure that the vapouriser gets hot to the touch, indicating healthy coolant flow, and to top up the coolant level if required.

2) Install the diagnostic software and connect a PC.

The Stag "AC Gas Synchro" software and USB driver should be installed on a laptop. It is better to download the latest version from http://www.ac.com.pl than to rely on the CD that is supplied with the kit. Note that the software version required depends on the exact ECU model fitted.

Connect the diagnostic cable to the 4 pin connector that emerges from the Stag loom, and plug into a USB port on the laptop. Allow the driver to find the USB device.

Load "AC Gas Synchro" software.

Insert the fuse or connect the permanent 12v supply to the LPG system (there may be a small spark due to the inrush current).

Switch on the vehicle ignition and then attempt to connect to the LPG ECU using ACGasSynchro.

At this point, the latest firmware can (and should) be installed onto the LPG ECU.

3) Check the LPG controller configuration using ACGasSynchro.

The ACGasSynchro software should be showing a screen similar to the following:

(http://i173.photobucket.com/albums/w63/kjwood/LPG%20Conversion/settings.jpg)

Note that the above shows the parameters for a Stag 300 ECU. Other variants such as the Stag 300+ and Stag 4 will have variations but the basics (which is all we're currently interested in) are the same.

Set the Car Parameters to suit your vehicle. In all Omegas converted according to this guide, the settings shown will suit, except that the Number of Cylinders and Number of Cylinders for coil should be set according to the number of cylinders on the engine.

The LPG Controller Settings shown should be a good starting point except to note that the Calibration Parameters are automatically set during calibration and should not be edited manually.

Ensure that the Injector Type is correctly set for your LPG injectors. The Valtek Type 30 injectors with red coil housings normally supplied in Teilo's kits should be configured as "VALTEC/RAIL/AC 3 Ohm". Other injector types will require different settings and damage can result from an incorrect setting!

4) Start the engine on petrol and check live parameters using ACGasSynchro.

Verify that the engine still starts and runs normally on petrol.

Check the live data displayed on the right hand side of the screen when ACGasSynchro is running and connected to the LPG ecu.

With a fully warmed up engine running on petrol the following typical values should be displayed:

Parameter	Typical value
LPG Pressure	Not Important
MAP Pressure	Around 0.30
Injection Time (all cyls)	Around 3 ms
LPG Temp	should match ambient temperature of engine bay
RED Temp	Should match coolant temperature
Lambda Voltage	Should cycle between 0 and 1v (0 and 5v for X20XEV)
Battery	13-14.5 volts
RPM	Should match engine RPM

If the temperature and pressure readings are incorrect it could be that the ECU is configured for the wrong type of sensors. Open the Settings tab and check these match the sensors supplied in your kit.

Injection time should be visible for each of the cylinders in the engine. On a V6, it should be obvious that the injection time for the two banks are varying independently (for example, if the 1,3,5 bank is connected to channels 1,2&3 of the ECU, these should be showing the same duration whereas channels 4,5&6 will be slightly different). This can be useful in identifying injectors that have been cross-wired by mistake.

If the engine RPM is wildly inaccurate check the setting for Number of Cylinders and RPM Signal.

Make sure that any issues are resolved before proceeding further.

Title: Re: Fitting LPG - Commissioning and calibration
Post by: Kevin Wood on 07 April 2010, 13:05:19

5) Precautions for working with LPG.

The first thing to mention before filling with LPG is that the LPGA COP11 chapter on the properties of LPG should be read and understood before the potential of coming into contact with it exists.

The salient points are that, whilst LPG is dispensed and stored as a liquid, it is a gas that is more dense than air at room temperature. It has a boiling point of -42^oC and a vapour pressure at room temperature of around 7.5 BAR (110 PSI).

Liquid LPG will therefore either be at a high pressure, or, if spilled, will remove heat energy from anything it contacts until it either reaches -42^oC or evaporates. It can cause severe frost burns if it contacts skin after leaking from an installation so, if contact with liquid is possible, wear insulating gloves and clothing, and eye protection. If liquid is observed leaking from a system, avoid contact with the liquid or any parts it may have been in contact with, as they are likely to become extremely cold.

LPG as a vapour has a strong stenching agent added so its' presence is easily detected by smell before it reaches a dangerous concentration. However, because it is heavier than air it has the potential to pool in lower lying areas where there is little ventilation. If it reaches a sufficient concentration it can cause suffocation and present a risk of fire. For this reason, when commissioning a system or carrying out work requiring disconnection of LPG lines, it is best to work in an open, well-ventilated area and to avoid working near drainage systems and garage pits, for example.

This information is not necessarily complete or definitive so please satisfy yourself that you will be safe before proceeding and, if in doubt, have your system commissioned by an experienced LPG professional.

6) Perform first fill and check filler connections and tank valve for leaks.

I would suggest that the permanent supply fuse for the LPG system is removed before filling to prevent the system switching to LPG before it is calibrated and checked for leaks.

Take care filling the system for the first time. As soon as the LPG pump starts dispensing fuel, the pressure in the tank and filler pipework will rise quickly to 8 BAR or more, and any leaks will quickly make themselves known. It is probably advisable to dispense only 5 litres or so in the first instance. Keep an eye out for leaks around the filler or obvious strong smells of gas that might indicate that gas is venting from the valve box.

Having added a small amount of gas to the system, my preference is to drive immediately to a remote layby and check the system over. Whilst an escape of LPG in a well-ventilated area will not likely be dangerous it will be made obvious by the smell, and has the potential to cause concern on a crowded garage forecourt. ;)

The filling process will leave liquid fuel in the filler pipe and tank so any leaks will be obvious for some time after filling as the fuel boils off.

Use a soap solution in a plant sprayer or a leak detector spray to detect any leaks around the connections to the rear of the filler, then open the tank valve airtight box and check the valve connections and for leakage around the rim of the multivalve. The unlikely event of a leak in the latter location will be a problem if the tank has been completely filled, hence the advice to only add about 5 litres of LPG so, in the event of a leak around the valve that cannot be easily rectified, only a relatively small amount of gas will be vented.

Once you are happy that the filler and tank valve present no leakage problems, it is safe to fill the tank and check that filling is stopped at roughly the 80% fill level.

Return to the forecourt and fill until the pump cuts off. The pump should rapidly cut the delivery at the 80% level. If the flow gradually slows to a trickle this is a sign that the tank valve is not limiting the fill level.

Check that the tank contents gauge is indicating roughly the 80% mark and ensure that the total volume of liquid dispensed is about 80% of the tank capacity.

Bear in mind that, because the fuel density varies with temperature, forecourt pumps can indicate slightly less or more than the actual delivered volume of liquid. The fuel is effectively sold by mass and not volume. For this reason, allow perhaps 5 Litres either side of the 80% volume before becoming too concerned. The most important thing is that filling stops sharply and completely at the prescribed level.
 
In the event that a tank does become overfilled it should not generate a hazardous situation because the relief valve will vent to atmosphere should the pressure in the tank become excessive. Bear the possibility of venting in mind when parking the vehicle, in this case. Leave the vehicle in a well ventilated area but out of the sun and away from drainage systems and pits, ensure the airtight valve box is closed to prevent injury from escaping gas and consider draping the tank with wet towels if it is likely to get hot. Burn off the excess LPG by using the car once the system is fully commissioned, and, once the tank is empty, investigate the valve problem that caused overfilling.

Title: Re: Fitting LPG - Commissioning and calibration
Post by: Kevin Wood on 07 April 2010, 14:41:05

7) Start the engine on petrol, warm up and try LPG Auto Calibration.

With the engine warmed up, reinsert the LPG supply fuse and connect the ACGasSynchro software to the LPG ECU.

Start the engine, select Autocalibration and start the calibration procedure. The system will switch between LPG and petrol a few times during this procedure.

If there are signs of a serious gas leak anywhere in the system, stop the engine.

If the calibration fails take heed of the error message. It might, for example, indicate that the vapour pressure is low or that one of the injector circuits is open.

Generally, errors that the nozzles are too small or too large can be ignored at this stage.

8) Check LPG installation for leaks.

While the calibration is running, make a check of the fuel supply connections from the multivalve to the vapouriser and the vapour connections through the filter and measurement tee to the injectors for leaks.

9) Check and, if necessary, adjust vapour pressure. Repeat Auto Calibration

Once the calibration has finished, I would suggest clicking the "B/G" selector in the bottom right of the screen to select LPG as the fuel, then checking the LPG vapour pressure while the engine is running on LPG. This should be set to 1.1 BAR as a starting point. Often vapourisers are shipped set to 0.8 BAR which is too low.

The vapour pressure can be set by turning the allen headed plug in the centre of the vapouriser front face using a 10mm allen key. It may be necessary to remove the sticker from this face. Screw the plug in clockwise to increase the pressure.

Once the vapour pressure has been set to 1.1 BAR, perform the AutoCalibration procedure once more.

10) Perform manual calibration adjustment on road and check performance.

The AutoCalibration provides only a starting point for correct calibration of the system. In particular , it is limited to running the engine at idle speed only, so it is vital to perform manual adjustments to the calibration on the road.

This requires, ideally, a passenger with a laptop connected to the diagnostic connector of the LPG system and running ACGasSynchro.

The cable can normally be temporarily routed out of the bonnet by the scuttle and into a front window for this purpose.

Select the MAP tab on the ACGasSynchro software, as shown:

(http://i173.photobucket.com/albums/w63/kjwood/LPG%20Conversion/map.jpg)

Press the B/G button on the bottom right if required to switch the car to running on petrol, Press the blue Petrol Erase button and drive off on a calibration route that will hopefully allow a number of engine operating conditions to be used from slow and fast cruising to full throttle acceleration and climbing and descending hills.

The software will build up a number of points in the map graph area which will eventually be joined up to form a curve, as shown. This is a representation of how your petrol injector duration varies with engine load.

Once a distance of 5-10 miles has been covered, switch the car to LPG briefly and check that the engine pulls happily from light to heavy throttle. Watch the crosshairs on the fuel map as you do so. They should closely follow the curve drawn while on petrol. If there is an obvious, large error in any area of the curve, the orange line on the map needs to be moved to correct the LPG calibration. Click on the yellow dot closest horizontally to where the issue was observed and drag it up if the cross hairs were too low, or down if they were too high. Switch back to LPG and try again until the curve is followed closely.

Avoid running on LPG for too long while the map is a long way out of calibration as this will result in the fuel trim adjusting, meaning you have a "moving target"!

Once the calibration looks reasonable, return ideally to the start of your calibration route, switch to LPG, press the green lpg Erase button and drive the whole route on LPG, collecting dots on the graph, which will be green this time.

Once a green curve has been drawn based on the injector duration when on LPG, you can compare the lines and ensure that they overlay each other accurately as shown above. If there curves do not overlay well, the LPG calibration needs to be adjusted by moving the orange line once more as described above.

Finally, try a full throttle acceleration run over the whole engine speed range while watching the signal from the lambda sensor(s).

The scrolling graph of values at the bottom of the screen is useful here. The outputs from the Lambda sensors can be seen cycling between low and high in the above screenshot. This is normal during cruising or idling. Ensure, however, that the Lambdas indicate 0.8-1v solidly through the whole range of engine RPM at full throttle. This step is vital to ensure the engine is not running lean under full throttle acceleration at any point.

Running lean at full throttle can cause piston and valve damage due to excessively hot combustion. It also causes poor power output.

Title: Re: Fitting LPG - Commissioning and calibration
Post by: Kevin Wood on 07 April 2010, 16:14:09

11) Perform tank level indicator calibration.


The LPG/Petrol switch button panel has an LPG level indicator consisting of 4 green LEDs and a red LED. These show the level of liquid in the LPG tank based on the signal from the float sender in the tank.

If an accurate indication on this panel is desired, there are two steps to calibration that are required:

Selecting the correct sensor type

The correct type of sensor can be set by pressing the Gas Level Indicator button on the parameters page of ACGasSynchro. The four choices of sensor boil down to the resistance of the potentiometer in the sensor and whether the resistance rises or falls with the fuel level.

Since several different types of multivalve and also 4 hole tank arrangements exist it is best to get your supplier to indicate which setting is required. However, sometimes the resistance is stamped on the body of the level sensor. In addition, its' behaviour can be checked using a multimeter on an Ohms range before fitting to the tank.

Adjusting the sensor calibration

It is best to use a few tanks of LPG following commissioning before final calibration of the level gauge. This is because it is easiest if you have a feel for the total mileage that is normally covered on a tank of gas.

One way to calibrate is to divide the total tank mileage by 5, and after each fifth of the tank has been burnt, connect ACGasSynchro and make a note of the voltage at the sensor output while the vehicle is on level ground. This gives you the approximate threshold voltages for the LED indicators.

Another way to calibrate is to have someone watch the voltage in the level sensor calibration screen while the tank is being filled. (Note: the ignition switch needs to be on to achieve this.)

Divide the usable tank capacity into 5 "sectors". For example, on an 80 litre tank the usable capacity will be a little over 60 litres, so have an assistant fill the tank from empty and shout out the level every 60/5=12 litres. Set the LED indicator thresholds to the displayed live level value at each interval of 12, 24, 36 and 48 litres. This should give a reasonable starting point to the calibration.

Fine tuning of the calibration can be carried out once a few tankfulls of LPG have given the driver a "feel" for how the gauge is behaving.

Title: Re: Fitting LPG - Commissioning and calibration
Post by: Kevin Wood on 13 April 2010, 11:01:28

12) Initial use on the road

Over the first 1000 miles or so, try to use the vehicle on LPG as much as possible and be on the lookout for issues that were not present when running on petrol.

The LPG kit components will "break-in" over this period. Injectors that seemed rattly to start with often quieten down noticeably. Sometimes minor leaks may become apparent, so be wary of the smell of gas and investigate where required.

In general, the car should drive exactly as it did on petrol. Any misfires or hesitation might indicate ignition troubles or a need to adjust the calibration. The only exception to this is when changing up at maximum RPM which does cause a hesitation on most Omegas, the cause of which is currently under investigation. A way to avoid this completely if it is found to be annoying, is to, for example, set the system to switch over to petrol at over 5500 RPM.

Sometimes it is necessary to tweak the switch over to gas parameters due to lumpy running after starting in some scenarios. The default settings allow a switch over to LPG only a few seconds after a "hot" start, and this can cause a lumpy idle if the car is not started and driven immediately. It might be found necessary to increase this parameter to 15-20 seconds.

Generally, vapouriser temperature to switch over to LPG can be set as low as 20-25 degrees C without any issues. The switch over to LPG while the car is being driven should not be noticeable to the driver at all on a properly configured system.

After 1000 miles it is advisable to check and, if necessary, adjust the vapouriser output pressure back to the value used during calibration. Ideally, the calibration and mapping of the system (Steps 7 to 10) should also be repeated at this stage, and the system double checked for leaks.