D-gas versus Dieselgas

[Wilbur]

Hi all,

Does anyone have any opinion on the relative merits of these two gas fumigation systems?

As I understand it, the Dieselgas Australia system is all electronic with lots of sensors to set up the appropriate quantity of gas, while the D-gas system is entirely manual and doesn't seem to have any way of adjusting the gas flow to suit throttle opening, speed etc.

Now I don't really like lots of electronics in vehicles, but I just wonder if the D-gas system works properly without all the inputs that the dieselgas system has?

I would be very grateful for opinions, as I plan to have one fitted next week.

Cheers all,

[p38arover]

Diesel Gas Australia or Diesel Gas Technologies? The latter is more sophisticated.

[DeeJay]

My understanding is that the D-Gas system is designed to deliver more power with marginal mileage improvements ie what diesel is substituted by cheaper LPG. They offer warranties on engine failures, so it should be reliable.
From what I've read of the Dieselgas it wrings more power and economy which- IMHO is asking just a bit much but thats only an opinion.
But I'm interested in other feedback, coz my knowledge is purely based on internet searches.
One other point is the D-Gas system will provide highest economy on engines running 2500 constant RPM - that is why Perth-Melb-Sydney trucks love that system possibly as good as Dieselgas economy in that application. The better economy goes downhill with load & speed variations. I think the D-Gas website is very honest.
Good luck
David

[Disco_owner]

Wilbur;

Some info I found on the web:

D-GAS system:

LPG vapour fuel is injected into the engine's intake manifold, homogeneously mixing to the engine's intake of atmospheric air. The liquid diesel fuel is injected into the cylinders as before.


Under the compression cycle, the air mixed with the LPG fuel heats to hotter temperatures due to the alternate fuel's higher 'heat of vaporization'. The increased temperatures during the compression cause the diesel fuel to stay in a gaseous state and forces more droplets of diesel
fuel to vaporize and volatize. Compression of the air/fuel mixtures never reaches auto-ignition, so pre-ignition is not a concern.

Ignition, as previously, is accomplished automatically as diesel fuel is injected into the engine.
In addition to the increased vaporisation and pre-combustion temperatures, the gaseous fuel, due
to its 'stoichometric flame speed' of 0.43 of LPG (propane), higher volatility and higher auto-ignition
temperature (high octane), causes a quicker and more spontaneous combustion resulting in increased power
and economy without engine modification.

The power increases are due in part to the increase in volumetric efficiency from the requirement for less oxygen in the air/fuel/alternate fuel mixture charge and maintains the engine's existing stoichometric ratios. Although the gaseous alternate fuel should increase the temperature of combustion of the fuel mixture over dedicated liquid fuel combustion, this has not been measurable and is believed to be negligible.

Since the diesel liquid fuel is virtually vaporised and volatilised pre-combustion, and since combustion is more rapid and complete, there is one explosion consuming the fuel and releasing its energy.
No 'combustion waves'. An audible quieting of the diesel knock can be verified with a stethoscope.
Since there are no additional explosions of the combustion wave, excess heat is not generated in after waves of combustion, reducing the formation of NOx and the engine's cooling system is not
strained dissipating the excess heat. Cooling system temperatures remain as before, because of thermostats, electronic cooling fans, etc. Engine oil temperatures can decrease by up to 20 degrees Celsius with the D-GAS system in operation. Exhaust with 'lower' hydrocarbons and NOx emissions is
released to the atmosphere.

As virtually no fuel is present in the exhaust gas, there is no after burn in the exhaust. Exhaust temperatures can decrease on vehicles fitted with the D-GAS system and an increased vapour content of the exhaust is observable, a further indication of more efficient combustion.

Additionally, the properties of the LPG gaseous fuel dissolves carbon and tar deposits in the combustion chamber after a period of operation. Combustion chamber deposits are responsible for significant increases in emission, heat generation and inefficient combustion. Dual fuel system operation cleans the combustion chamber even in older or high mileage vehicles and returns them to a cleaner more efficient condition.

Fuel savings are generated because the combustion is more complete with less energy being wasted to heat or turned into harmful emissions. Less liquid diesel fuel is required to maintain the same operation levels, yet torque is increased, providing more satisfactory engine performance, improved acceleration, and greater load hauling capabilities. In some manual fuel injection engines, a slight adjustment can be made to reduce the diesel liquid fuel to the engine.


Diesel Gas System:


High-pressure liquid petroleum gas (LPG) is converted to a low-pressure (just above atmospheric)
useable gas. The gas passes through a solenoid valve (or stepper motor) which is controlled by outputs
from the system’s computerised processor measuring precisely the quantity of gas required. This metered
amount of vapour travels through a hose into the vehicle air intake system and subsequently into the inlet
manifold as a mixture of air and gas.

The computer module (processor) controls the flow of gas optimising performance and ensuring safety. Manifold
pressure (via a MAP sensor) or throttle position (via a throttle position sensor) and engine speed are monitored.
The module then adjusts the gas flow depending on engine load and driver demand. The amount of gas injected
(or the ‘gas map’) is completely (and only) programmable by a laptop computer. This allows a large degree of
flexibility to adjust the system to suit your requirements.

The system does not allow LPG into the engine at idle and is programmed to limit the amount of gas introduced
at maximum load to prevent over-fuelling. The system shuts off gas flow when the brakes are applied or the driver’s
foot comes off the accelerator.
The system can be switched on and off (if ever necessary) via a dash mounted switch. If gas is unavailable or you
run out before a service station, it is not necessary to switch the system off. Instead you will notice a decrease
in performance as the gas runs out.

[Wilbur]

Thanks all for the info and ideas.

Ron, I wasn't thinking specifically of Dieselgas Australia or Dieselgas Technologies (I didn't realise there were two) but mostly I was interested in the benefits of the electronic ECU controlled type over the fully manual type.

Thanks Disco-owner and DeeJay for the run-down.

Has anyone here tried the manual D-gas system?

Cheers,

[p38arover]

I notice the DieselGas Technologies/Hunter Gas Sequent II system installs an exhaust gas temperature probe into the exhaust.

[Xavie]

I have been looking in to it also and Ron gave me some good info in another thread- thanks again Ron. The only thing I'd say is if you are interested ring as soon as you can because it is a 10+ week wait. The wait seems to be because of the gas tank and not having many around.

After looking in to it I decided to go with D.G. technologies at Kingswood (western Sydney).

They are hopeless on email and phone but they all seem to be so have your questions ready.

Xav

[Wilbur]

Hi all,

I have been told that D-gas have two versions, one for non-turbos that have throttle position sensors, temp sensors etc etc, and another for turbo engines that uses only manifold pressure to control the amount of gas injected.

I have mixed feelings. I am not a great fan of too much electronics in cars, but I wonder how effective that simple manual system would be? Has anyone had experience with the non-electronic systems, or any hearsay reports?

Cheers,

Paul

[p38arover]

When it comes to increasing power in a diesel with LPG, I'd want as much sensor information as possible to avoid damage to the engine. That's why I mentioned the EGT (see also LRHybrid100's thread on EGT D110 - TD5 EGT Gauge Temps).

I don't know if the DGT system displays EGT to the driver, it may only go to the control software and be visible on the programming software. I can ask, I'm going over to DGT this arvo.

[Iain_B]

I signed up for a D-Gas system this afternoon - $3800 fitted. I have to wait until 9th August - LPG tanks are in short supply. So after the $2000 rebate, it will cost me around $1800. Using the current price of diesel and gas and my present fuel consumption with the expected 20% better fuel economy, it will pay for itself in less than 70,000km - which is less than two years for me. Fine for me as I plan on keeping the car for a long time anyway.