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.
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.