building an engine for LP only

[treetrimmer]

Hello all! I have really enjoyed reading many of the posts here and have learned a lot about my Disco. I am starting a fairly major rebuild of a 95 D1 and need some advice. Since I didn't get a lot of hits on my "Propane or duel fuel" post, and since I pretty much want to do propane only, How should I build an engine to run only Propane? I am building a 4.6 on my 3.9 block. I know this is not optimal but it will be a mild rebuild and will not be abused. I have concluded from research and "professional advice" this would be acceptable (with studs of course) for petrol, would this change for propane only? Compression ratios, components, ignition, injection options, etc., anything anybody knows about this would be greatly appreciated! Also, how would engine performance compare to petrol only if the engine were set up to perform its best with propane? Even though the overwhelming reason for this is cleaner emissions, I would like to think I could get similar performance from propane if the rebuild is specifically for propane. The rebuild will be simple enough but some leads on propane specific components would be greatly appreciated.

Thanks,

Tim

[simonr]

Tim.

No problems with Propane / LPG only - lots of people do it.

You have to advance the timing a bit (to about 20 deg BTDC) and make sure the ignition circuit is in good order as it needs a GOOD spark to start from cold.

Set up well - you will have no problems!

Si

[treetrimmer]

Will the stock coil do? I am already running Magnacor wires and an RPI spark amplifer with the 3.9 chip. I just replaced the stock coil with a bosch replacement as mine died. Also, one major question is how far can I go with the compression for propane only?

Thanks,

Tim

[simonr]

Will the stock coil do? I am already running Magnacor wires and an RPI spark amplifer with the 3.9 chip. I just replaced the stock coil with a bosch replacement as mine died. Also, one major question is how far can I go with the compression for propane only?

Thanks,

Tim

No idea on the compression in absolute terms, however, the higher the pressure, the weaker the spark (takes more volts to jump a given distance). However, I doubt it will make much difference with the difference in compression you will achieve. If it does, you could go for one of the EDIS conversions or even CDI for a better spark. I would go for the compression you want and adapt the other bits to suit.

I found that a ballast coil works best. Most of the ones sold are non-ballast and tend to burn out fairly quickly. Certainly with the RPI box, ballast is best.

I also run Magnacore leads - and am impressed wih them.

If you are setting it up yourself, there was a thread I posted a while back called something like 'LPG tuning' which tells you what the different adjustments on the vaporiser do and the sequence for adjustment.

Si

[MarkieB]

Of course for a bespoke system there are options such as liquid propane injection; a few pennies for the injectors, although seems popular with high performance people so far

[isuzurover]

There is lots of good info on propane setup and components on www.outerlimits4x4.com . But in Australia we call it LPG - liquified petroleum gas (mainly propane, but also some butane).

Some threads I found in a quick search:

http://www.outerlimits4x4.com/PHP_Modules/...pic.php?t=61839

http://www.outerlimits4x4.com/PHP_Modules/...pic.php?t=40449

http://www.outerlimits4x4.com/PHP_Modules/...pic.php?t=33295

[treetrimmer]

Thanks all for the info and the links. I'll keep researching. I've had trouble with the search on this forum as most keywords I type in only bring up the "sorry" message.

Thanks again,

Tim