Can diesels pop and bang?

[dinkel]

Never heard it happen.

[bluespanner]

dinkel said:

Never heard it happen.

When the injectors were totally shagged on my tractor if you went flat out it used to pop, bang, backfire and blow bits of exhaust at you. It also shot impressive flames.

[dinkel]

I mean . . . a decent roadcar

[bluespanner]

dinkel said:

I mean . . . a decent roadcar

Hehe, i know

I dont think the low octane fuel and the methods of combustion (ie compression) allow it. I stand to be corrected though.

[Matthew C]

Since diesels run lean, even well into smoking, I reckon you could rig up a system to inject (insert fuel of choice here) into the exhaust for pops and bangs.

[mrandy]

i read the audi lemans car is eerily quiet

[mojocvh]

With the Audi v6 tdi it's normally the connecting rods coming through the block/crankcase.........

[bluespanner]

Ouch.

[TJW]

I doubt it, as deisle fuel as such a low octane rating, thus exploding in the piston without a spark, so there would most prob hardly any/if no fuel un burnt l8ike a petrol engine where the spark plug is needed to explode abnd not all fuel is burnt....

[Matthew C]

mungo said:

Matthew C said: Since diesels run lean, even well into smoking, I reckon you could rig up a system to inject (insert fuel of choice here) into the exhaust for pops and bangs. That is a very sad thing to do... Cars that crackle, pop, bang and flame on the overrun should only do so naturally

Agreed, but the question was, 'can they?'.

[TJW]

mungo said:

Indeed. I believe the diesel Audi Le Mans car is very quiet and unlike every other LM car ever made does not spit flames - That is the answer I think

THIS ANSWER?

I doubt it, as deisle fuel as such a low octane rating, thus exploding in the piston without a spark, so there would most prob hardly any/if no fuel un burnt l8ike a petrol engine where the spark plug is needed to explode abnd not all fuel is burnt....

[TJW]

mungo said:

TJW said: mungo said: Indeed. I believe the diesel Audi Le Mans car is very quiet and unlike every other LM car ever made does not spit flames - That is the answer I think THIS ANSWER? I doubt it, as deisle fuel as such a low octane rating, thus exploding in the piston without a spark, so there would most prob hardly any/if no fuel un burnt l8ike a petrol engine where the spark plug is needed to explode abnd not all fuel is burnt.... When I said "indeed" I was agreeing with Matthews reply to my previous post - I was trying to say if the Audi LM diesel doesn't spit flames no other diesel will I am not a technical expert but I would be very suprised if any diesel car would overrun popping and spitting flames >> Edited by mungo on Sunday 14th May 00:19

xatly........ a deseil care on overun with un burnt fuel... the deisel has such a low octane rating it doesnt need a spark to explode, thus most prob all the fuel exploding.../ thus thus; no overrun backfire overwise...?

[bales]

Dont quote me on this but because I have no idea whether it relates to cars, but when I have been watchin tractor pulling I have been in the pits when they have been starting up. The super stock ones with the heavily tuned diesel engines tend to have flames out of the exhaust on idle and pop and bang very very well with a bit of throttle.

However I think this may have more to do with 4 stage turbocharging, about 10 bar boost and perhaps 4000bhp.

[Pigeon]

A road diesel will never pop and bang because it never overfuels. On the overrun it simply stops injecting any fuel. A petrol car with a properly set-up fuelling system won't pop and bang either

Tractor pulling diesels are monstrous beasts that overfuel like buggery, so things are a bit different there

[DieselJohn]

Its all been said already but just to echo:

If you get a fuel/air mix into the exhaust manifold/turbo it could go off. There is no way for that to easily happen on a road car though. About 0.7 of stoich is about as rich as you will get and there is not really any way for the mixture not to go off in the cylinder.

I've only ever seen diesel miss-fire (no combustion) once but I can't say when I'm afraid.

I know nothing about tractor pulls but I imagine they run super rich ie stoich+ I guess there will be no oxygen in the exhaust system but excess fuel could go off on reaching the tailpipe exit.



Edit// Just thought: very late injection for the purposes of chucking fuel into the exhaust system so that it will burn in the DPF and thereby clear out the soot is one thing that does happen. Don't think it makes a noise though.

>> Edited by DieselJohn on Monday 15th May 19:41

[Parrot of Doom]

I've always wondered, on the overrun if it stops injecting fuel, how does the engine continue to run?

[bluespanner]

Parrot of Doom said:

I've always wondered, on the overrun if it stops injecting fuel, how does the engine continue to run?

The momentum of the car keeps it turning.

[dinkel]

. . . and slows you down, like a brake. I use it all the time. The D4D diesel has a bit more mass than the little 1.3 Civic though.

On overrun a carbed engine pops and bangs more than an engine with EFI, at least in my experience.

[Matthew C]

dinkel said:

. . . and slows you down, like a brake. I use it all the time. The D4D diesel has a bit more mass than the little 1.3 Civic though. On overrun a carbed engine pops and bangs more than an engine with EFI, at least in my experience.

I've got a carbed engine which doesn't pop and bang on overrun, in fact the only 'interesting' noises I hear are normally ones I don't want to hear.

[Pigeon]

dinkel said:

On overrun a carbed engine pops and bangs more than an engine with EFI, at least in my experience.

Yep... EFI can shut off the fuel completely, carbs can't.