Is any (black) smoke good smoke?

[tonydca]

My understanding of diesel smoke is:
- black = too rich, partially-burned fuel
- white = no combustion; starting problems or stuttering/too lean
- blue = engine oil

So my 6 year old was watching me fiddle under the dash while the engine was running. He asks: "Daddy? Can I Rrrummm the engine?". I think - she's in park, handbrake on, no problemo. "OK," say I, "Give it a little nudge on the gas pedal".

Naturally, he smiles with joy and proceeds to lunge with maximum effort onto the gas pedal with both hands. After a brief rev up to around 3900 rpms, followed by a quick explanation to him of the term "little nudge", I notice that the revving has produced a noticeable amount of black smoke.

The vehicle was fully warmed up, but I have just recently blanked off my EGR valve, so I'm wondering if my mixture is now too rich. My fuel economy is OK, but I notice that whenever I pull away hard from a stop, other drivers are loathe to follow too closely.

My question is: can revving the engine in Neutral/Park be used as a way to calibrate the fuel pump? i.e., if she's fully warmed up, give 'er the boot, and each time she smokes a bit, dial it back a smidge until it blows just the faintest hint of black.

Or is this something that needs to be done under load (with a rear-facing back-seat passenger watching for smoke).

Anybody with seat-of-the-pants diesel tuning experience out there? I have heard rumours of the evils of running too lean... Thanks,

Tony.

[jessef]

I do it both at idle and then under load looking out the mirror.

The only way to get rid of 100% smoke would be to run one of those particle nuclear reactor-looking canisters you see on the Fuso and Izuzu cab overs.

Some black smoke while heavy on the pedal is acceptable.

White/blue is not. You got the colors right

[Green1]

good, no, normal, probably.

you'll never get rid of all of it, especially in high revving, or high load conditions. That said, many people on the UK site have noticed significant smoke after blanking the EGR, the reasoning as I understand it is that the fuel mixture is tuned with the expectation that the EGR is there, blanking it changes things, and as a result you also need to adjust the fuel mixture to compensate.

[FalcoColumbarius]

good, no, normal, probably.

you'll never get rid of all of it, especially in high revving, or high load conditions. That said, many people on the UK site have noticed significant smoke after blanking the EGR, the reasoning as I understand it is that the fuel mixture is tuned with the expectation that the EGR is there, blanking it changes things, and as a result you also need to adjust the fuel mixture to compensate.

Hear. Hear.
I don't care what they say about you, Green... I think you're pretty smart.

Falco.

[mararmeisto]

Smoke, black or otherwise, is generally only good for getting that retard who won't let you into the lane to back off (I've used that one a couple of times). Usually the van won't accelerate any faster, but it's somewhat satisfying just the same.

Black is unburnt fuel in not enough air. It's little different than when you stomp on a gasser's pedal and that rich gasoline smell comes out the tailpipe - unburnt fuel. Big difference is you can see diesel, hence the 'dirty' moniker. This is the 'particulate' that is being looked for in the AirCare testing.

[tonydca]

good, no, normal, probably.

you'll never get rid of all of it, especially in high revving, or high load conditions. That said, many people on the UK site have noticed significant smoke after blanking the EGR, the reasoning as I understand it is that the fuel mixture is tuned with the expectation that the EGR is there, blanking it changes things, and as a result you also need to adjust the fuel mixture to compensate.

Although from thinking about it, the EGR is supposed to close under load at higher RPMs, so if anything, having a functioning EGR should require slightly *less* fuel and then only at lower RPMs when the valve is open (more exhaust = less O2 = less fuel needed).

And perversely, I was noticing tonight that the vacuum line to my now-blanked-off EGR was not coiling in a smooth circle. Turns out some bright spark in the far flung past had inserted the cutoff end of a nail about 2 inches up into the vacuum line, stealthily blocking it, so my EGR has never been working - unbeknownst to me. I guess the shaft seal finally gave way and started to leak.

But I digress - I guess I could always just plop a coupla washers on the wastegate actuator to bump up the boost and use that unburnt fuel a bit more, er - "productively"... Or does the fuel delivery keep increasing with increased boost up to the max setting on the rear of the pump? $%^&&^!!!!!

[FalcoColumbarius]

I just cleaned my EGR out not long ago (it was filthy, gunked). Now I'm going through fuel. The last time we set the IP the EGR was all gummed up ~ now it's not.

Falco.