LPG fumigation in diesels

[Emporator Member Find all posts View Profile Close Emporator]

Hello all!

After reading about the Government's $2000 subsidy for LPG, I'm thinking about fitting LPG to my turbo-diesel Peugeot, purely for fumigation. Does anyone have any experience with LPG in diesel applications?

[zigparacingtadpole Senior Member Find all posts View Profile Close zigparacingtadpole]

Re: LPG fumigation in diesels

I havent done it myself, but a couple of guys I work with have hade LPG fitted to their diesel 4x4's and having sampled one of these cars both before and after, I can say it does make quite a noticable difference to performance. In both cases they have had small (30L) tanks fitted and inject the gas at a ratio of about 4parts diesel to 1part gas (both were after a more complete burn of the diesel so the mix ratio is low, increase the mix to say 3 to 1 and you make even better gains in power but use more gas).
I did a little bit of research on this and have discovered that a setup of this type in Adelaide would have cost around $3000 (depending on vehicle type and tank configuration) before the grant was introduced. Since the grant was introduced, the setup I was researching has now increased in price to around $4800 (less the grant). Of course there is no profiteering happening here is there people. Good luck trying to find an accredited installer that can fit your vehicle in the next millenium (a guy I work with has had his Commodore on a waiting list since early October, and is not looking like he is going to get LPG before mid to late Feb). This is in Adelaide, Sydney or in fact anywhere else in Australia might be different.

Ring around, see whats on offer, talk to the installers. Keep in mind that installation of LPG on diesel vehicles is a little more specialised than on a petrol vehicle and not every one does it.

[tillyfromparadise Senior Member Find all posts View Profile Close tillyfromparadise]

Re: LPG fumigation in diesels

LPG does not give a more complete burn of the diesel fuel

It gives more power by introducing more fuel

[Terry Syd Senior Member Find all posts View Profile Close Terry Syd]

Re: LPG fumigation in diesels

And the fuel is already in a vapor form, and the addition is uniformly mixed into the intake air (not a spray pattern) - and the addition is already at the beginning of the combustion cycle, not at the end (after top dead centre) as with the normal extended pulse of a diesel injector.

A 20% fumigation sounds reasonable.

I am waiting for a fellow from the Surf forum to get back from vacation. He is talking about LPG kits for $2500-$2800. I'll take a look at the outfit and get back to the forum.

[Emporator Member Find all posts View Profile Close Emporator]

Re: LPG fumigation in diesels

Sounds like a real winner!

I'll definitely be fitting it to the Pug! I know that I have to fit a donut tank, which unfortunately will increase the cost somewhat. Still, getting the $2000 grant will certainly offset the cost.

Speaking of which, is the grant difficult to obtain?

Terry,

I'd be interested to learn more about the kits for $2500 - $2800 you mentioned. Let me know when you hear more!

[Guest Close David]

Re: LPG fumigation in diesels

Hi Tom,

What particular benifit is it that you are looking to achieve by fitting LPG to your Car?

[Emporator Member Find all posts View Profile Close Emporator]

Re: LPG fumigation in diesels

Hi David,

I'm just looking to increase my range I guess. I like the idea of going 1500 km without going near a bowser! Well, that and I read that by using LPG it can reduce the consumption of diesel (or biodiesel) by about 13% or so. Don't know if it's true or not (perhaps someone out there can set me straight?) but 50 cents for LPG is cheaper than the $1.25 I pay for Volume Plus biodiesel blend!

Anything I can do to reduce consumption is a good thing I figure! Imagine going to Melbourne and halfway back before the need to refill - isn't that a cool idea!

If and when I do fit it, the Pug will have so many add ons! A Hydrogen genrator, LPG, water injection etc. I'll have to do a juggling act to maintain them all!

[Terry Syd Senior Member Find all posts View Profile Close Terry Syd]

Re: LPG fumigation in diesels

The recent fuel inquiry indicated that gas is going to the fuel for Australia in the immediate future. Australia has a fair bit of it, some 7% of the Earth's reserves.

To have a dual system installed will allow a person to be in a position to utilise the gas. Hopefully, this system I will be looking at will be capable of using CNG as a fuel, as that will be much more plentiful than LPG.

A 20% fumigation, in conjunction with an 80-90% reduction in fuel flow through the diesel fuel injection system would allow the diesel system to still run the vehicle if the gas ran out (albeit with reduced power). It also extends the range of your existing diesel/biodiesel.

If rationing of diesel fuel became mandatory (it will at some stage), then the percentage of fumigation could be increased with a further reduction of diesel. Some diesel/gas conversions run almost entirely on gas with only the idle circuit of the diesel injector pump running in order to trigger ignition.

I have read a few reports of idiots that love the increased torque of the gas and have bumped the gas flow way up. Lunching an engine because you like power is dumb. The gas is already in the cylinder when the ignition pulse starts. If you pump in too much, then if you have not retarded the ignition point, the pressure peak will occur too soon. This will not only increase the thermal load on the engine, but also mechanical loads.

The fellow who is offering the kits says that he has the donut tanks available.

[tillyfromparadise Senior Member Find all posts View Profile Close tillyfromparadise]

Re: LPG fumigation in diesels

Hello Emoerator

I suspect that if you replace 20% of the diesel you are using with LPG you should realize a reduction in Diesel consumption by a similar amount

[Emporator Member Find all posts View Profile Close Emporator]

Re: LPG fumigation in diesels

Hi Tilly,

That's exactly what I've heard - the gas that you use will displace a certain amount of diesel, as well as apparently giving slightly greater torque. It follows that the more gas you use the more diesel you displace.

There's other benefits as well supposedly - increased intervals between oil changes and a cleaner combustion chamber make for icing on the cake if you ask me!

Hi Terry,

I'm very interested in what you wrote - I hadn't thought about the bigger picture, ie long term. By the sounds of it, Australia has quite a bit of gas! Does a CNG setup differ from an LPG one significantly? You've made me curious now - I'm beginning to think CNG might be a more attractive option for the long term. Would finding a CNG outlet be a problem?

[Terry Syd Senior Member Find all posts View Profile Close Terry Syd]

Re: LPG fumigation in diesels

Some of the gas systems can use CNG, NG or LPG. The computer makes the necessary adjustments.

I have an LPG home heater. The same model of heater also came as a unit that would use NG. I understand that the difference is largely a substitution of jet sizes.

If such was the case, then a basic LPG system may be able to be converted to the use of CNG with a minium of work. I'm looking into that issue with this unit I am going to check out.

[Guest Close David]

Re: LPG fumigation in diesels

Hi Tom,

If Range and economy are your main aims, perhaps a good old fashioned WVO conversion may meet your requirements as well.

I looked at how CNG worked some time back and from my understanding, the system at the time worked by you leasing a compressor that filled your tank from your gas at home. As I understand it, Cng has to be compressed to extremely high pressure because in a car system it can't be compressed to liquid so to get any range the gas has to be pressurised right up. I seem to recall that relatively huge tanks like 200+L were needed to get a car 500KM or so. Apparently the power draw of the compressor adds significantly to the cost of fueling the vehicle besides the gas itself because it takes a lot of power to compress the gas to such high pressures.

As I recal, it takes something like 6-8 hours to fill a tank and range is pretty limited anyway. As far as I am aware, there are very few service stations where you can fill up on CNG, most filling points are privately owned.

It is some years since I looked into this so maybe things have changed but this is how I understand CNG systems to work.

[zigparacingtadpole Senior Member Find all posts View Profile Close zigparacingtadpole]

Re: LPG fumigation in diesels

LPG does not give a more complete burn of the diesel fuel

It gives more power by introducing more fuel

Direct quote from the sales brochure left pinned to the notice board at work by owner of one of the vehicles I mentioned.

Regardless of the sales pitch, it certainly work. Whether the net gain justifies the cost is something I would be looking at rather closely.

[Emporator Member Find all posts View Profile Close Emporator]

Re: LPG fumigation in diesels

Hi David,

I thought about a WVO conversion some time ago when I bought the Peugeot, but from everything I've read about SVO/WVO conversions and Lucas rotary pumps, I'm not game to try it! As much as I like the idea of using WVO as a fuel, I've not really been inclined to try it. Apparently, the Lucas pump on my model Pug does not tolerate WVO well at all. The Bosch pump, on the other hand, does quite well. I guess you could always swap the pump if you wanted to do it, but I'm not too keen on the idea of it for some reason.

Hmm, looks like the CNG is a no go! Sounds like far too much hassle and inconvenience. Looks like I might have to stick to the LPG conversion. Still, two thumbs up to those that do run CNG! I like the idea of being able to fill up at home!

[tillyfromparadise Senior Member Find all posts View Profile Close tillyfromparadise]

Re: LPG fumigation in diesels

Hello Adam

Yes, there is a LOT of inaccurate information available about how things work.
You can google Natural Rubber Biodiesel and find over 200,000 websites warning about the "Natural Rubber" fuel lines used in most pre 1993 vehicles.
Natural Rubber was NEVER used in automotive fuel system, petroleum products degrade natural rubber the same as biodiesel does.

You can go to many LPG web sites that will tell you that typically a Diesel engine only burns 75% of the diesel fuel injected, the rest goes out the exhaust. LPG Makes more of the diesel burn.
What a load of bunkum!
If a diesel only burns 75% of it's fuel then a petrol engine must be just as bad because we ALL know that diesel engines get better economy than petrol engines. That would only happen if petrol engines were pumping out lots of unburnt fuel like they claim a Diesel does.
How long would a catalytic converter (Diesel or Petrol) last if 25% of the fuel was going out the exhaust pipe unburnt?

In my mind, the correct answer has to do with the questions:
Why does a diesel engine typically get much better fuel economy and produce less power than a petrol engine of the same displacement?
Does a Diesel engine ever achieve "Stoichiometric Combustion" with injected diesel fuel or is it always running Lean?
If the answer is that a Diesel always run lean could a gaseous fuel such as LPG be included into the air to use some of this unused Air to produce extra power?
If you got rid of the injection system on your diesel and converted your diesel engine to run on 100% LPG (Spark plug required and probably lower compression) coming through the turbocharger mixed with air at the correct stoichiometric ratio, what do you think would happen?