I'd be interested to know how they handle the fuel pressure compensation on a standalone install.The piggy back LPG systems have a pressure sensor so they can calculate the injector pulse based on the converter output pressure.Most of the newer aftermarket ecus have several configurable analog inputs which I suppose could be connected to a pressure sensor and then mapped to achieve the same result?

The other option I had considered when I was considering the vapour injection route was just to disconnect the vacuum signal to the converter or reverse the spring so it would just run at max pressure all the time.The problem with that was that the output pressure (on the converters I could get info on) would've been very marginal once boost was taken into consideration and even with the biggest injector size, the duty cycle would've maxed out at lowish boost. I have since found there are boost suitable converters available with higher vapour output pressures, but tbh the advantage of vapour injection on a dedicated lpg car (especially a turbocharged one) is minute compared to using a liquid injection system.

I've been running LPG for approx 25 years now on various vehicles. The major point many get wrong is the advance curve for LPG.
There's three key points:
1. Ease of starting - you still need 5-10 deg. BTDC
2. Rate of advance - needs to come in very quickly, like 15-20 deg @ 1250 rpm
3. Max advance - far less than petrol, 21-22 max

Thats great Lpgo, thank you.

Here is some info I received you may find helpful, or already know:


Harley