Thread: D-gas versus Dieselgas

I just want to ask,how would the system overgas?.I have had four LPG powered vehicles and each one had an overpressure valve that shut off if there was a sudden drop in system pressure.I think you all have to realise that this isn't a new thing,it has been around a long time and there isn't blown up engines lying around,trust me we would all hear about it.Wilbur I can't see how your engine would use oil because of D/Gas,it would be because it is working hard,you have said it yourself.It is a shame that you could not get it to work though. Pat

Originally Posted by Disco_owner

Wilbur;

....... Fail-Safe automatic override ,not sure if the Diesel-Gas sequent II system has this built in ? in case of a Sensors or microprocessor fail , and they can be done to switch off the system in mirco-seconds or even nano-seconds , Electronics can be designed to do this and they can be done to do so reliably.

Most electronic systems use a micro-processor to test data from various sensors and so calculate the appropriate amount of gas for any situation. They can also have provision to shut the system down in the event of a malfunction. HOWEVER, the gas is typically regulated (or shut down) by using a transistor to rapidly switch on and off a valve. The ratio of ON time to OFF time defines the amount of gas injected - much like any EFI system. If this transistor fails, or in fact the circuitry that controls it, no amount of argument from the microprocessor will stop an over-gassing situation.

You are quite correct, electronics can be designed to fail-safe in most (never all) possible fault scenarios. Automotive EFI systems rarely fail at all these days - but we are talking about systems that have evolved over many decades with the worlds best engineers doing the refining. The automotive industry doesn't take kindly to failures of third-party components, so only the best survive. When Bosch design a gas-fumigation system for a mainstream motor manufacturer, then I will trust an electronic system not to cause damage.

Having said all that, I must add that I know no details of the electronic systems available in Australia. For all I know they have double or even triple redundancy circuits and if so, the risk of a fail-dangerous situation is vanishingly slim. It would be a good question to ask of your supplier before fitting an electronic gas fumigation system.

Cheers all,

Paul

Originally Posted by PAT303

I just want to ask,how would the system overgas?.I have had four LPG powered vehicles and each one had an overpressure valve that shut off if there was a sudden drop in system pressure.I think you all have to realise that this isn't a new thing,it has been around a long time and there isn't blown up engines lying around,trust me we would all hear about it.Wilbur I can't see how your engine would use oil because of D/Gas,it would be because it is working hard,you have said it yourself.It is a shame that you could not get it to work though. Pat

Hi Pat,

In my case, I presume the jet fitted was too large for the pressure differential between the gas pressure and the manifold pressure. This is why it over-gassed. The installer just fitted the jet size specified by D-gas, and didn't test it properly. My car is pretty noisy and I didn't hear the extra noise - I went out and covered 400 k's as suggested by D-gas to test the gas ratio usage which turned out to be over 40%.

I don't know what is actually causing the extra oil usage. It has been suggested that the extra heat of detonation damaged the rings. It has always worked hard since I have had it, but only started using oil after I covered the 400 k's of testing with D-gas.

However, there may have been some other problem with my installation because other than increased noise, there was absolutely no change in performance and very minimal or no reduction in diesel fuel usage.

I am glad your system is working - I wish I knew the difference between your set up and mine!

Cheers,

Paul

Originally Posted by Wilbur

Hi Pat,

In my case, I presume the jet fitted was too large for the pressure differential between the gas pressure and the manifold pressure. This is why it over-gassed. The installer just fitted the jet size specified by D-gas, and didn't test it properly. My car is pretty noisy and I didn't hear the extra noise - I went out and covered 400 k's as suggested by D-gas to test the gas ratio usage which turned out to be over 40%.

I don't know what is actually causing the extra oil usage. It has been suggested that the extra heat of detonation damaged the rings. It has always worked hard since I have had it, but only started using oil after I covered the 400 k's of testing with D-gas.

However, there may have been some other problem with my installation because other than increased noise, there was absolutely no change in performance and very minimal or no reduction in diesel fuel usage.

I am glad your system is working - I wish I knew the difference between your set up and mine!

Cheers,

Paul

Have you had a compression test done since?

Originally Posted by Dougal

Have you had a compression test done since?

Good suggestion, Dougal, no, I hadn't thought of that. Although I don't have any 'before' figures to compare with, I would guess that it would be unlikely that if any damage has been done that it is the same on each cylinder. If there is a marked difference between cylinders, that would certainly indicate damage rather than wear.

I will investigate!

Thanks,

Paul

Paul is the top intercooler hose full of oil?,the turbo's do breath heavy if worked hard. Pat

Originally Posted by PAT303

Paul is the top intercooler hose full of oil?,the turbo's do breath heavy if worked hard. Pat

Thanks Pat, interesting question, will check on the weekend.

Cheers,

Paul

Originally Posted by Wilbur

It may not be that simple. If you are bowling along a noisy, corrugated road and your electronic system throws a wobbly and starts severely overgassing, you could blow your engine completely before you even hear it detonating. The noise made when my D-gas system was on was very slight, but now it uses oil......

I design electronic equipment for a living. I chose a non-electronic system for my car. It was a dud, but the point is I elected not to go electronic based on my professional knowledge. Unless the system is designed to be fail-safe (rarely done except in medical equipment) you just can't be confident.

According to the speal on Gas Tek (Sequent) they use self resetting fuses, system logging and automatic shutoff if there is a problem. The whole system is resin set making it water, dust and vibration proof.

If you want total reliability with no electronics stop 4WDing and start bushwalking.

To answer Ron's question I don't work for Gastek but I own one. After five minutes talking to the bloke who designed the system, Derek Watkins, you wouldn't go anywhere else. He'd be the top Land Rover mechanic in the country.

Thorne