Now, from the subject line of this post, you may be thinking I am talking about when to convert your car from Petrol (GAS) to LPG.  But I’m not.

More and more people are converting their vehicle to be Dual Fuel. That is, having both Petrol and LPG.

Of course, there are two types of LPG delivery.  Using a standard mixer, or using gas injectors. You can use either system, and we might go into more detail in a future email, but at the moment we will assume that you are using a standard gas mixer for the gas delivery, and fuel injection for the petrol.

So, what is the best way to make sure your vehicle is as hassle free as possible, while you still reap the benefits of using LPG?

To begin with, you want to start the vehicle on Petrol.  This gives the best starting and cold running.  Then you will want to switch over to LPG at a specific engine condition, where you will not notice the changeover.  The colder the environment, the more important this is.

And finally, you want the engine to stop nicely when you turn it off.  You don’t want your engine to run-on, or “pop” when you turn off the ignition.

Let’s Begin:

The best way to set this up is to have 2 maps.  The primary map is for Petrol, and the secondary map is for LPG.

Set up the ECU so the engine starts on the primary map (Petrol).  Then, you want it to change over only when there is some heat in the engine.  But not only that, you want it to change over when the engine is decelerating, so if there is any fluffiness caused by the changeover, the driver does not feel it.

I would set the temperature changeover to be somewhere around 40 to 50 degrees C.  The engine should achieve this with just a couple of minutes of running time.

I would also set the changeover to happen below 5% throttle, and above a specific RPM.  Now, this RPM will be very much dependent on the type of engine.  On a big 6 or 8 cylinder engine, you may have this set to 1500 RPM, but on a small 4 cylinder engine, you may have this set at 2,000 RPM.  You need to set this so you don’t have to rev the engine too high, but also that it is high enough so on a rev-down there is a second or two for the changeover to occur.  This is more important when using a standard mixer, than when using gas injectors, but the same general theory applies.

Now you have this set up and the engine is now running on the secondary map, running LPG.

There are some stories of particular LPG setups where there can be problems with the remaining LPG in the manifold “popping” when the engine stops due to manifold heat.  If you have this problem, you can use the turbo timer, and configure the ECU so that when you turn off the ignition (the turbo timer takes over) the ECU switches back to Petrol while the turbo time is counting down.  If you want, you can set the turbo timer to run for only 5 or 10 seconds, which is plenty of time to purge any gas out of the intake manifold.

This eliminates any LPG in the intake manifold and avoids that embarrassing “pop”.

There you go.  We have run setups like this on various installations with great success, so it means you can too.

Until next time,

For specific advice on your LPG injection system (current or future) and how you can use your V500 ECU to get these, and many other systems setup on your vehicle you can contact us at wolfemail@wolfems.com.au.