Diesel engine running on gas

[chatelot16]

the pilot start is a bad example because it is very detonating even with a low compression ratio: therefore in a diesel even cold it pete before TDC and even if the injection pump does not inject anything

you just have to hear the horrible clicking that a diesel makes when it is swallowed too many start pilots at startup!

there is a simpler way to know if a pump is injecting: hold an injector pipe in your fingers: the shock in the pipes is very sensitive, and the shock is about the same as the dose of diesel is small or great because it takes the same pressure to reach the injector rating

at home it is clear when the engine is lnacé at a certain speed, and that I abruptly lower the speed control, the injection shock disappears completely, until the engine is lowered to idle speed

soon there will be images, with a piezoelectric sensor pinched on a pipe

I had already experimented with a piezo block of gas lighter and an oscilloscope, but it was before the digital camera and internet

now it will be with piezoelectric block, plugged into the microphone jack and recording by audacity

if you have already removed a direct injection cylinder head you can see that the combustion chamber is a hot spot! it may be made of refractory steel, it often happens that it deteriorates with heat!

part of this part is not cooled, because it has a piston side and a chamber side

there is also the glow plug which constitutes an uncooled rod therefore a hot spot: it is almost sure that the LPG will ignite during compression before pmh when the engine is hot

[Did67]

Are you talking about indirect injection!

What is your engine that cuts the injection ??? [as said, I do not doubt - my Xantia did, cut the injection; It's just to know ; and I'm still not sure that the old Lister or copies of Lister do; but I'm not sure the opposite either !!!]

[chatelot16]

I noticed this complete cut of the injection on different diesel completely different

CLM engine with centrifugal regulator in the engine and "mechanical precision" injection pump

vendoeuvre engine with centrifugal regulator in the engine and bosch injection pump: even easier to see because the control lever coming out of the regulator which controls the injection is visible: we can clearly see that it is capable of completely cutting the injecton

Perkins engine with indirect injection with bosch pump with pneumatic regulator: I have one on a GMC and I have seen others on tractors

the most recent engine I have is the citroen C35: by noise or by holding an injector pipe it seems that it cuts completely

to have a proof, I will bring out my thing with piezo block of lighter gas to pinch on a pipes

Citroen ZX is for me already too modern, maybe a minimum injection stop has been added for a question of pollution

downhill in extended engine brake, without mini injection the engine cooled, when it is necessary to inject again it risks smoking a little ... with a minimum injection we could better maintain the temperature? I find this reasoning bad, because injecting a minimum dose when there is no need is a waste, therefore wasting during all the descents, and all the deceleration, for a completely transient benefit to the power take-off seems to me bad ... but it wouldn't be the first bad thing we put in our engines for anti pollution reasons

[Macro]

A bosch VE type mechanical rotary pump does not inject anything if the load lever is in the slowed down position as long as its rotation speed has not gone back down to the slow down speed. (between 400 and 500 rpm of the pump shaft)

Some people tested the pumps on the bench with a drill at the end of the shaft .. It injected at the beginning then nothing ... They said my pump is dead .. But no but no ... It turns too fast for the position of the load lever ... In addition, the centrifugal regulator also influences the discharge of the advance cylinder ... Your "spark" is very likely not to be at the right time ... Bicarbs GO / GPL allow a saving of diesel but not to do without if the engine not deeply modified ...

[jonule]

what kind of modifications?

the pilot start is a bad example because it is very detonating even with a low compression ratio: therefore in a diesel even cold it pete before TDC and even if the injection pump does not inject anything

well I remember the start pilot on my 405 1.9TD makes the engine speed go up well without rattling ?!
I'm going to try with a propane bottle, well, I have to go get it at the station precisely; =)
that's for the practical part, for the theoretical part:
yes the combustion prechamber is a hot spot, precisely it seems to me; it also acts as a "mixer" with the air. on the other hand it would be interesting to know:
1) to what t ° C does the combustion prechamber rise?
2) at what t ° C does the gas self-ignite?

in any case, this could seem to be a serious avenue for explaining why certain experiments using HHO gas from electrolysers have not had results on certain engines?
...

[chatelot16]

same problem with hydrogen! hydrogen petera before pmh when the combustion chamber is hot

luckily the HHO throughput is quite low and it doesn't do much

and if there was too much HHO it would be rather harmful

[jonule]

what do you recommend?
the use of "air" type solenoid valves for gas injection at the right time?

[jonule]

to set the ignition advance? =)

[chatelot16]

for me in an indirect injection with this big hot spot I would only dare to put a fairly small amount of gas

just to make a saving of diesel, but doing a rather poor mixture difficult to turn, and not harmful to the engine in case he comes on too early anyway

let the regulator of the diesel injection pump do its usual job

put a piezoelectric sensor on an injector pipe to detect the duration of injection blow

electronic circuit which sends gas when the injection shots are too long

reduction of the gas flow when the injection stroke is too short

this is a system that could be used to consume a certain amount of methane to save diesel, but keeping diesel as their main energy source

[Flytox]

...
that's for the practical part, for the theoretical part:
yes the combustion prechamber is a hot spot, precisely it seems to me; it also acts as a "mixer" with the air. on the other hand it would be interesting to know:
1) to what t ° C does the combustion prechamber rise?
2) at what t ° C does the gas self-ignite?
...

The temperature of this or that organ is one thing, the functioning in condition another. On a positive ignition engine, the spark plug operates at a temperature> 450 ° while the ignition point of gasoline is lower (250 °). It is necessary to take into account the pressure, the temperature, the stirring of the gases, engine speed, load ... and the ignition delay etc ... In this story what matters is that the engine does not knock, for not kill him. There are a whole bunch of parameters that play with the temperature to reach the detonation.

From one engine to another of different technologies, I will not be surprised that one goes smoothly and the other detonates / breaks.

http://fr.wikipedia.org/wiki/Essence_%28hydrocarbure%29

http://fr.wikipedia.org/wiki/Bougie_d%27allumage

Due to the chemical reactions induced by the combustion of gases, the heat given off by the explosion and that generated by electric arcs, the electrodes must resist significant corrosion effects10. This is why they are generally covered with alloys composed of nickel, silver or platinum8. The nickel melting temperature is around 1 ° C while that of platinum reaches 450 ° C and iridium around 1 ° C770. They can be subject to excessive wear, or even melt when overheated. Electrodes that are too hot are likely to pre-ignite the engine, which can cause major damage to the piston2. The normal operating range of the electrodes is 450 to 850 ° C. The mixture ignites before the spark above 1 ° C.

Many deposits can also form on the spark plug electrodes, greatly reducing its capacities. Carbon deposits form during prolonged use of the starter, weak or delayed ignition when the compression rate is low or when the spark plug is too cold (below from 450 ° C).