Question about lpg convertion and engine convertion

[markus_74]

Hello,

Need some info about lpg convertion as here lpg is very2 cheap, 1 GBP per 3 kilograms.

what I need to convert my m40 engine to lpg? are there any ready to use convertion there and how much price?

my m40 318i now is about 12 kilometer per liter combination route, does if use lpg is about the same? or more efficient?

also how to convert kilograms lpg into liters?

my other question, because I also like to change my engine into m20 b25 someday, does the convertion for M40 318i engine can be use for m20 b25 engine?

Thank you
Markus

[Brianmoooore]

Four types of LPG conversion;
1/ A simple 'first generation' mixer system with no electronics, which effectively replaces your fuel injection with a simple carb. Not as bad as it sounds, since LPG readily turns into a gas and mixes with air, unlike petrol.
2/ A 'second generation' mixer system, which still replaces the EFI with a carb., but fine tunes the mixture with feedback from a lambda sensor, and also usually introduces touches like over run fuel cut off and diagnostics. This is the type of system I ran on my red touring for over 10 years and 100,000 miles with great success.
3/ A multipoint vapour injection system. This mounts LPG vapour injector nozzles in the inlet manifold, close to the petrol injectors, which are normally controlled by the petrol ECU's signals that should go to the petrol injectors, modified by a second box of electronics.
This kind of system is far more complex than 1/ or 2/, and will largely eliminate the small power drop that you get with these more primitive systems, and can be fitted to E30s, although it won't perform as it was intended, since most E30s don't have any kind of feedback loops in their management systems, other than idle speed control.
If you have an E30 with a later engine with a plastic manifold (M50, 52, etc.) you will have to use a system like this to eliminate the possibility of a backfire in the manifold blowing it to pieces.
4/ A liquid LPG injection system. Still under development, or used for factory fitted systems on some makes. You won't be fitting one of these to an E30 any time soon.

LPG has a density of almost exactly 0.5, so 1Kg of LPG = 2 litres.

A type 1 or 2 system can usually be upgraded from M40 to M20 by changing the mixer and the backfire arrestor - around £40 for the two around here.
A type 3 system upgrade would normally need a change of gas ECU and extra injectors, plus a change of loom.

[markus_74]

Four types of LPG conversion;
1/ A simple 'first generation' mixer system with no electronics, which effectively replaces your fuel injection with a simple carb. Not as bad as it sounds, since LPG readily turns into a gas and mixes with air, unlike petrol.
2/ A 'second generation' mixer system, which still replaces the EFI with a carb., but fine tunes the mixture with feedback from a lambda sensor, and also usually introduces touches like over run fuel cut off and diagnostics. This is the type of system I ran on my red touring for over 10 years and 100,000 miles with great success.
3/ A multipoint vapour injection system. This mounts LPG vapour injector nozzles in the inlet manifold, close to the petrol injectors, which are normally controlled by the petrol ECU's signals that should go to the petrol injectors, modified by a second box of electronics.
This kind of system is far more complex than 1/ or 2/, and will largely eliminate the small power drop that you get with these more primitive systems, and can be fitted to E30s, although it won't perform as it was intended, since most E30s don't have any kind of feedback loops in their management systems, other than idle speed control.
If you have an E30 with a later engine with a plastic manifold (M50, 52, etc.) you will have to use a system like this to eliminate the possibility of a backfire in the manifold blowing it to pieces.
4/ A liquid LPG injection system. Still under development, or used for factory fitted systems on some makes. You won't be fitting one of these to an E30 any time soon.

LPG has a density of almost exactly 0.5, so 1Kg of LPG = 2 litres.

A type 1 or 2 system can usually be upgraded from M40 to M20 by changing the mixer and the backfire arrestor - around £40 for the two around here.
A type 3 system upgrade would normally need a change of gas ECU and extra injectors, plus a change of loom.

Thank you brian, I think I will go with system 2 that you have prove it good, mine is m40 with injector, do I must buy new carburetor?

or any company sell complete DIY conversion, and how much cost you to convert your red e30 into lpg?

thank you
markus

[Brianmoooore]

The parts I used to convert the red touring cost me around £600 GB many years ago, when the current resurgence of LPG had only just started, but the ones I've converted since have only cost a fraction of that, using a mixture of new and second hand parts.
The 'carburettor' that you will need is known as a mixer, and is just a single piece of alloy with no moving parts. For E30 applications, it's a flat plate, around 10 - 15mm thick that fits between the air filter box and the AFM.
DIY complete kits are available from a couple of places in the UK, and probably from many other countries around the world, although some places restrict their sales to registered 'professionals'.