I don't know of anyone on this forum that is claiming LPG to be a catalyst. There have been multiple links to websites that are making all sorts of claims, but the claims have been dismissed as sales hype. Here is a preveious post of why I am interested in the dualgas conversions.

"David, I agree with everything you said. Some of the claims appear to be not credible, hype if you will. For example, I do not believe the claim that a diesel engine only burns 75-85% of the fuel and that the addition of another hydrocarbon fuel will some how increase the burning of the remaining 15-25% of unburnt diesel. Doesn't work that way. Perhaps if I was overfueling and then introducing NOX, then I could believe it.

I try to run my engine lean as it is. I have a turbo that runs 9 psi at full boost. My boost compensator stops adding fuel at about 6 psi, therefore I am just adding extra air at 9 psi.

I'm looking at reducing my diesel/biodiesel consumption. If I can substitute some gas into the engine for the diesel, then I would like to try it. The gas presently is selling for much less than diesel (although not as low as homemade biodiesel).

I've already mentioned on this forum that when Peak Oil hits that I want an engine that can burn just about anything. Being able to substitute LPG into the engine is another step in that direction. The fact that gas is presently fairly inexpensive is a bonus.

If I can substitute 20% of my fuel with LPG, then I have just picked up further range on my diesel fuel. On my last bush trip I got 8.6 litres/100 km. If I was using the diesel/gas combination, then that would translate into 6.9 litres/100km on the diesel.

The availability of liquid fuel is going to be a real problem in the near future. We WILL have petrol/diesel rationing, it is probably only a few years away. If I can 'stretch' that ration by another 20-25% by using gas, then I want to have that option.

Australia does have large gas reserves which will continue to produce fuel for a number of years after the liquid oil runs out. The addition of gas into engines now, will extend the period of transition into the Post Peak Oil paradigm. That may lessen the impact of the crisis we are in and perhaps give us some more time to come up with some alternatives. - It will at least give me more options."

When I was looking at Australia's oil production several years ago, the production of oil (for petrol) was going to drop off, however the production of 'condensate' from gas wells was to remain constant for a much longer period of time. Propane is the major component of condensate.

When I first heard of dual-gas systems I had assumed that it was and 'either/or' type of system. That is, because of the different burning rates of the fuels you either ran petrol/diesel and then switched over to the gas. This is true of petrol systems, however the diesel systems can run a 'fumigation' system in which a small percentage of gas is introduced into the cylinder to supplement the amount of diesel fuel that is used.

A diesel takes in a full cylinder of air during the induction cycle. It is the amount of fuel that is added to the cylinder that determines the power output. It is very easy to increase a diesel's power output by dumping in extra fuel. It does reach a point where there is no more oxygen to burn and any extra fuel is not burned. Thus, we have turbo/super charging to add more air to the cylinder.

The dual-gas system on a diesel engine allows the engine to run both fuels at the same time. If the fuel injection system remains unaltered, then the extra gas being introduced produces more power (up until the oxygen is consumed). It appears than many people have gone to this type of system in order to increase the power for towing or carrying heavy loads up hills.

Another approach is to back off the injection pump volume and to replace the diesel with gas. Using this approach the engine will continue to make the same power as before, but with a reduced diesel consumption.

In both cases, if the gas runs out, the engine will still continue to run. In the first case the engine will still have the same power as before the conversion. In the second case the engine will have a reduction of power to the extent that the diesel volume was reduced.

I am more inclined to take the second approach. Perhaps decrease the pump volume by 10% and then increase the gas to say a 20% of the available hydrocarbons. This way I can stretch my diesel economy by around 20%, I pick up a bit of power when I decide I need it, and if the gas runs out the vehicle is still driveable.

There is no free lunch - although the Government is offering this 'freebie', the fact is we are still paying for it through taxes. If someone is going to receive the benefit of my tax money, I would like it to be me.

I am looking at this modification to my patrol. Google "Diesel Gas" and it will bring you to the relevant website for your state or area.

They claim a 46% power increase and a 21% economy increase. Big claims in my book and I want to take one for a drive before I spend a few thousand to have it fitted....

Hello Milhouse

Just below that it says on the same website:
"A small amount of LPG is introduced into the engine via the air intake system. This gas acts as a catalyst to increase combustion, ensuring all of the diesel injected is burnt. Most diesel engines have a burn rate of 75-80%, with the remainder of the diesel being burnt in the exhaust system or blown out as black smoke. With the Diesel/Gas Australia system, the burn rate goes up to 95-98%"

This is ALL absolute rubbish.
If they are knowingly posting a totally false description of what happens in the engine how can you believe anything else that is written on the site?
I am sure if you look hard enough they will claim it makes your teeth "Whiter than white" too.

Tilly

Dieselgas also wants $4,000 to install one of their systems.

I have been in contact with a fellow in the Sydney area who will be providing kits that can be installed as DIY and then the system will be checked and commissioned by a registered gas specialist. The kits are the fairly standard type that use an airflow sensor to determine the amount of gas to be added. These type of units have been around for decades.

As more information comes in, I'll post it.

Hi Tilly (and everyone else here) Hope you don't mind a Pom butting into your forums but hit them by accident, and as it happens we've just been discussing LPG fumigation on a Rover forum in the UK.

In answer to your question about more power from a fuel with a lower energy content, it's not a case of getting more power from the diesel but a case of using more of the air that the engine breathes.

Just about all diesels run with excess air in the mixture (no intake throttle) and rely on the amount of fuel injected to control the power. But if you put too much diesel in you start getting incomplete combustion and blak smoke BEFORE all the available oxygen in the air is being used.

LPG fumigation helps this in two ways. First, it's a fuel itself so as it burns it uses some of the excess air to release its own energy. Also, the fact that it's in there and burning helps to encourage better combustion of the diesel so you can run slightly higher fuelling without too much smoke. You're absolutely right that it's not acting as a catalyst - it's just that the flame it produces tends to ignite any diesel that is trying not to burn!

Possible power increases do seem to be around 20%, and the extra economy is caused by the fact you can drive with a lighter foot. Of course, the 20% better economy they talk about is only "diesel economy" - you have to put the LPG in on top of that - but the overall effect is a saving. At least it is at UK prices of around £4.10 ($10A) a gallon at the moment!

Doesn't give a big saving with homebrew bio, but it's a nice fix for extra power

As for fed & state governments actually SUBSIDISING people who want to use alternative fuels - if you lot ever vote 'em out can you put 'em on a boat over here please?????

Joe