e36 318i (m43) on LPG - MPG?

Post Tue Oct 27, 2009 12:01 pm

What MPG would anyone expect to get out of an LPG'd (sequential) E36 318i? Mostly decent length A-road runs.

It's clearly vastly cheaper to run than it would be on petrol, but I'm not convinced I'm getting the milage I should be. & I'm not about to fill up with petrol to find out what it'd do - I stay away from the expensive pumps these days!

Cheers

Post Tue Oct 27, 2009 12:31 pm

I was getting about 26-28mpg out of the iS on gas. And that was a single point which isn't as accurate. If it worse than 25 there is something that isn't quite right in my book.

Post Tue Oct 27, 2009 1:40 pm

Never less than 25, prob about the same as your iS tbh. I can certainly live with it, but I would possibly have expected a bit better... Not sure where to start with looking for potential issues though!

Post Tue Oct 27, 2009 1:48 pm

What management is it using? I know nothing of sequential setups and their software, but if you can find out what it is, usually it is downloadable.

Then try and find the comm port and plug a laptop in too check for any error codes etc. Once you have the software open you should be able to see it live in action and using the Lambda sensor tell if it is running too rich on different loads. Annoyingly it is a narrow band I suspect, but it should give you the right idea if it flicking between rich and lean like it should.

Interestingly if you fancy a drive to Salisbury one evening/weekend me and my brother have got a wideband lambda sensor with a bungied exhaust probe for on the road testing in different cars.

/Cough\Pikey/Cough\ This is the best way of working out what actual AFRs you have. I am not sure what AFRs LPG should run on, I am presuming it is roughly the same as a petrol-so around 12.5-13.5:1

Post Tue Oct 27, 2009 1:56 pm

I'll have to have an investigate... might well take you up on the wideband option - sure I can find out what it should be running & Salisbury's hardly a million miles away.

Post Thu Oct 29, 2009 6:38 pm

You've got to expect a 10% drop because LPG contains less energy per volume than petrol, then you're carrying a heavy LPG tank to. . . carrying a full tank of petrol won't help either.

I've found with my setup, that if it's running rich then there will be a lot of water coming out of the tailpipes, even when hot.