Thread: isuzu & LPG

Originally Posted by Dougal

That is the crux of the problem, you can't change the injection timing of the LPG. It's there in the cylinder and will ignite as soon as the charge gets hot enough. Which I've shown it can on a cold engine at idle.

If LPG could be injected at the desired time with it's own injector, there would be no detonation issues regardless of rates. The only downsides would then be the install cost and having two tanks to refill.

The question for today is:
Does LPG fumigation have a lower rate which below no detonation occurs or does it simply drop the evidence below our detection methods of noise and vibration?

To try and answer your question on detonation, I offer these observations:
When the engine I tested yesterday was cold, I let a quantity of LPG flow into the manifold of the stationary engine. When I started it there was a CLEAR AND OBVIOUS DETONATION EVENT. So yes excess LPG will detonate in a cold engine. Next test: applying LPG fumigation to a cold engine under load produced smoke/shaking but no obvious detonation. So ditto my comments on running fumigation only in a warm engine. Next test was on the road with the engine at operating temperature, fumigation on. Power level increase as noted. On reaching governor controlled revs the diesel delivery drops right off and the LPG DID NOT NOTICEABLY DETONATE. Boost pressure dropped rapidly and combustion was quiet. It would indicate that any possible LPG-only detonation was minuscule and unlikely to damage the engine under these conditions.
I am not arguing that CONTINUOUS use of the extra power is not harmful to the engine, various posts indicate that this likely to decrease engine life. It would of course help if someone thrashed their d-gas engine consistently hard and then dismantled it. How long will be long enough to detect these signs? I am the wrong person to ask.

Originally Posted by PAT303

... ZZZZZZZzzzzzzzzzzzzzzzzz.Maybe what I'll do is continue to drive my D/Gas Tdi and enjoy the experience. Pat

Good keep going, nothing to see here...

This thread is finally getting somewhere. The unstated assumption that an engine is undamaged until it breaks down is apparent in this thread. It has been stated multiple times, "My motor goes fine, therefore, detonation is isn't happening..." or similar.

We are finally getting down to the crux of the issue... is detonation happening? Is detonation measurable? Very interesting stuff despite the misconstrued posts and statements from all sides and the history of "disagreements past".

An interesting read on fumigation I just dug up:

http://www.mrsharkey.com/lpg.htm

Emission test of fumigation

http://dnr.louisiana.gov/sec/execdiv.../i/dsl-i60.gif

Originally Posted by bee utey

An interesting read on fumigation I just dug up:

http://www.mrsharkey.com/lpg.htm

Emission test of fumigation

http://dnr.louisiana.gov/sec/execdiv.../i/dsl-i60.gif

Thanks for that, haven't looked at his site for a couple of years. Did you see the jackknife Golf?

Originally Posted by Dougal

Camera methods don't work particularly well in diesels, the lens soots up and your measurements are no longer worth much. I've watched a video of combustion inside a diesel, they had about 5 burns before not much could be seen.
This is why no-one else has suggested it as a method suitable outside a lab.

Is yours a tdi or td5? Your mention of fumigation as an alternative to a diesel chip suggests it is a td5, yet you refer to it as a tdi.

Imagine your enjoyment of having even more power and torque without the hassle of two different fuel types.

Mate is was taking the ****,everyone seems to be trying to outdo one another with fancy words and quotes,trouble is NONE of you have gas fitted and what you say should happen is not happening to people who DO have gas fitted. Pat

Originally Posted by windsock

Good keep going, nothing to see here...

This thread is finally getting somewhere. The unstated assumption that an engine is undamaged until it breaks down is apparent in this thread. It has been stated multiple times, "My motor goes fine, therefore, detonation is isn't happening..." or similar.

We are finally getting down to the crux of the issue... is detonation happening? Is detonation measurable? Very interesting stuff despite the misconstrued posts and statements from all sides and the history of "disagreements past".

One of the mechanics at a well know LR workshop has had gas fitted to his personal Tdi for 10 years,still going strong,as I posted mine now has 30K on gas,still going.That is a loooong time for an engine that has detonation problems.I do agree with you on one piont,there is nothing to see here.Just a bunch of blokes argueing over something they don't have and have no idea about. Pat

Originally Posted by bee utey

To try and answer your question on detonation, I offer these observations:
When the engine I tested yesterday was cold, I let a quantity of LPG flow into the manifold of the stationary engine. When I started it there was a CLEAR AND OBVIOUS DETONATION EVENT. So yes excess LPG will detonate in a cold engine. Next test: applying LPG fumigation to a cold engine under load produced smoke/shaking but no obvious detonation. So ditto my comments on running fumigation only in a warm engine. Next test was on the road with the engine at operating temperature, fumigation on. Power level increase as noted. On reaching governor controlled revs the diesel delivery drops right off and the LPG DID NOT NOTICEABLY DETONATE. Boost pressure dropped rapidly and combustion was quiet. It would indicate that any possible LPG-only detonation was minuscule and unlikely to damage the engine under these conditions.
I am not arguing that CONTINUOUS use of the extra power is not harmful to the engine, various posts indicate that this likely to decrease engine life. It would of course help if someone thrashed their d-gas engine consistently hard and then dismantled it. How long will be long enough to detect these signs? I am the wrong person to ask.

Can you expand on the "governor controlled revs" part? Does this mean you're running the engine to the rev limiter?
How are you determining detonation or the lack of?
Why would a cold engine detonate but a warm engine not?

Please note that we aren't discussing extra wear due to extra power, we're discussing damage due to detonation. The indicator appears to be extra metals showing up in oil analysis.
Isuzu make B series engines (4BG1T marine) which are factory rated at 200hp. Wear due to extra power is not the concern here.

Mr Sharkey makes a few statements which are in contradiction with observations and published data. Like this statement:

Originally Posted by MrSharkey

Propane by itself resists self-ignition inside a diesel-fuel compression-ignition engine due to it's high flash point and narrow fuel-to-air ratio. During the compression stroke, the air/LPG mixture is compressed and the temperature is raised to about 400°C, not enough to ignite the LPG, which has an ignition temperature of about 500°C.

Adiabatic compression at 17.5:1 gives compression temps of ~650C. LPG's autoignition temp is 468C according to shell's MSDS.
http://www-static.shell.com/static/a...s/lpg_msds.pdf


Pat, do you know your engine isn't detonating or are you just assuming that because you can't hear it and it's not shaking around it's okay?
By the time you can see or hear a diesel under load bouncing around, there's some extreme banging going on inside.
Ignorance is bliss.

All I can say Dougal is the Tdi must be the strongest engine ever made if it can withstand detonation for 30,000k's.Every single thing you have posted is based on no real life experience,I have friends that are accademics,they base everything they know on theory. Pat