TheBoy wrote on 11. Apr 2011 at 20:08:


Perhaps you have... Not checked it.

Was in my sig until I lost my post count recently and couldn't have a link in my sig when I'd edited my avatar

I was talking to the guy that was servicing my BRC LPG set up last December in Oxford and he was saying that there is now an evolution of the LPG liquid injectors that were around a while ago, but that these actually work and he's fitting them to some BMW variants for testing in one of the touring car series.  The difference is apparently that the guts of the liquid injector (no vapouriser, no gas) are ceramic of some sort and work in a slightly different way to the old ones and don't have the membrane or something - I forget what exactly but that's 'cos I'm old - and so don't freeze, as they are essentially now the evaporator.  Anyway the point is stuff exists that means you can ditch one more part - the evaporator or vapouriser - and go direct liquid injection in much the same way as petrol.  I'm guessing that there is some cleverness going on in the gas ECU as it must have to know gas temp. and it probably can't due to there being no sensor nearby.

It might be worth having a chat with him.  www.oxfordautogas.com

Cheers

Paul

Yes, liquid injection has some nice properties. You lose the reduction in power completely because a liquid fuel doesn't displace as much air as a vapour.

I understood the tank-mounted pumps caused problems with them, though?

I would imagine it's also not easy to keep the whole fuel supply system liquid either, given underbonnet temperatures?

You could probably drive the injectors from the petrol ECU pretty much directly if the fuel pressure is under decent control and the injectors correctly sized. Gone is the need to compensate for vapour pressure and temperature. I guess it wouldn't need the same enrichments during warmup, though.

Problem is, it's not the cheapest solution, and everyone in the LPG supply chain is interested in supplying "cheapest possible" solutions to people whose only motivation is to save money hence we're only just starting to get away from god-awful mixer systems being the norm.

It's a shame, because I think LPG has potential to offer good performance benefits for those who care to put their hands in their pockets and build something a bit more optimal than a bolt-on kit on a standard engine.

Kevin