LPG worries

[liquid079]

Right, after finding a relativley cheap Lpg kit on ebay I thought I'd go for it and have a go at converting my car myself.

Speaking to a mechanic in the pub the other day, he told me that cars don't run on gas very well at all and I would be looking AT LEAST at a 20% loss in power he also told me that the engine would be short lived as the extra heat from the Lpg would burn the valves and other parts which would make the engine scrap, something to do with the engine running lean all the time.

This chap also told me I should be using platinum plugs, which I wasn't to worried about. Could anyone give me the true facts on lpg?

Thanks, Dan.

[Brianmoooore]

There isn't one thing in that list that has any truth in it at all!
With a venturi system, there will be a small power loss, which most people can't notice at all (I can't).
With a vapour injection system there will be no power loss at all (if fitted correctly).
In both cases, if the original fuel injectors are past their best, or there are other issues with the petrol system, you could actually gain power.
LPG combustion produces LESS heat than petrol, although the actual flame temperature is slightly higher. The valves on my M20 have lasted 8 years/100,000 miles + on LPG with no deterioration so far. A few makes of engine, with poor quality components (think Ford), can have valve problems, but these can be prevented by fitting an upper cylinder lubricating system.
If the engine is running lean, then it will melt pistons, etc., the same as it would on petrol. The kit has to be set up properly, otherwise of course it could run lean or rich or whatever.
As for general wear on the engine, that is greatly reduced because a) LPG does not contaminate the oil like petrol does - the oil comes out of the engine a similar colour to what it went in when you change it, instead of the black gunge that results from petrol running, and b) LPG does not require enrichment for start up and cold running, so there is no washing of oil off the cylinder walls, which is when about 80% of engine wear occurs.
You must certainly not use platinum plugs! LPG doesn't like those at all. Some engines with marginal ignition systems run better on iridium plugs, but there's no problem at all with any BMW engine.
One thing you will find, is that MPG decreases by around 20%. This is simply because LPG is about 20% less dense than petrol. Weight for weight, the mileage will be about the same.

[toby]

A few people on the forum run on LPG with no problem or noticeable loss in power.

[toby]

So how many miles do you get from a full tank Brian and what does it cost?

Ant is going to able to fit these soon so seriously considering it.

[liquid079]

Ok thanks Brian and Toby for confirming that, I must admit I took everything he told me with a pinch of salt as it went against everything that I had previously heard about Lpg and he did then tell me that my car would probably be ok without platinum plugs.

Brianmoooore I'm hopefully removing an LPG kit out of a jeep cherokee this weekend, it's a single point Leonardo system with 175 on the ecu. Are there any special tools or procedures I should follow while I'm removing this kit?

Thanks, Dan

[Brianmoooore]

No special tools or procedures required, unless there still LPG in the system. There are solenoid valves on the tank (some early systems only had a manual shut off valve), another solenoid valve on the filter under the bonnet, and a third one on the vapouriser. This means that there will be two sections of pipe containing LPG that are sealed off, and LPG, when released expands around X 400, IIRC. There should also be more trapped LPG in the filler pipe, so crack off any joints with caution, bearing in mind that escaping LPG, as well as being flammable, can also cause frostbite. Depressurise in the open air if possible, and definitely not near an inspection pit, as LPG is heavier than air.
If you need to release the LPG in the tank for any reason, do it in the middle of a field, using a 12 volt battery to power the solenoid open, and make sure the battery (and any sparks) are upwind.
Make sure you get all the Leonardo wiring loom, including the bit that goes back to the tank and 'aquire' the lambda senor as well, if you can.
I have wiring diagrams for DIY Leonardo/laptop leads, and the software, although someone recently posted an online free download site for the software.
Don't worry about removing the 6mm plastic pipe from the back to the front of the jeep (but get the ends), as it should be renewed.,

[liquid079]

Great, thanks for that info.

I'm travelling up to wales on Sunday morning to remove the kit although the chap says he's going to remove as much of the kit as he can.

I'll report back

[Pete-M]

I've run a fair few cars with LPG over the years and have to agree with Brian - the mechanic is talking crap. If you're using a modern multi-point LPG setup, you'll be very unlikely to notice any power drop at all. Maybe a slight loss of bottom end torque, but nowhere near 20%.

I used a '00X plate Vauxhall Wrectra with LPG to do a fair few miles earlier this year - even driven with complete disrespect for the car (I despise Vauxhalls) it'd do a 500 mile round trip for £25.

[Globulator]

So what is the most cost effective way to LPG an E30?
Will any 2nd hand kit (of a 2.5litre capability) work ok?
Does the cab need a special tank?

[Brianmoooore]

Most cost effective way is to buy the bits off ebay, or to buy a ready converted car with suitable kit on it, remove the kit, and sell the car on, hopefully at a profit.
Helps of course, if you know what parts you need.
E30s work fine with a venturi type kit, so I wouldn't really recommend the complexity of an injection kit on one.
2nd hank kit will be fine for a few bits, as long as it has a tank of suitable size, otherwise you will just be buying a vapouriser and filter/solenoid.
Tanks come as cylinders and toroids (to fit in spare wheel well) of varying sizes. A trade off between losing luggage space against the convenience of the amount of fuel you can carry.

[oze30]

I'm still trying to find someone to fit mine!

[Brianmoooore]

I'm still trying to find someone to fit mine!

Get your hands dirty! Can be done in several easy stages, without having to take the car off the road for more than a couple of hours at a time.

[kam-325i]

Is there a reason why cars dont use LPG cylinders like you get on the back of a Fork Lift ?

[handpaper]

Is there a reason why cars dont use LPG cylinders like you get on the back of a Fork Lift ?

Three reasons I can think of, fuel supply rate, duty and convenience.

The cylinders supply LPG as a gas at a fairly low rate. The gas is vaporised by ambient heat (surrounding air etc.) and the cylinder will get cold in use. If you tried to run a car like this either the tank would rapidly cool to the point where the LPG wouldn't vaporise and you'd have to wait until it warmed up before you could continue, or it simply wouldn't be able to supply gas fast enough and the engine would run lean.
This is why a car has LPG supplied to the engine bay as a liquid under pressure where it is vaporised by a heat source.

Current duty on LPG for automotive use is about 8p a litre, set to rise to 10p in 2010. This is the only legal way to purchase LPG for road use; the gas in a cylinder has no duty on it and will get Customs and Excise annoyed at you

Much as I'd love to 'fill up' by changing cylinders (50+ litres of fuel in under a minute!), not everyone can lift them!

[kam-325i]

well thats answered that question then...!