Smoke Control

[907DAVE]

Is it just a function of the MFD map?

Or is it the Low Boost Fueling map, PW, etc.?

What is the most efficient way to reduce smoke?

[cleatus12r]

Originally Posted by 907dave

Is it just a function of the MFD map?

Or is it the Low Boost Fueling map, PW, etc.?

What is the most efficient way to reduce smoke? Leave it stock.

Poor (or less than highly efficient) combustion efficiency and the amount of fuel per amount of air are big contributors.

If your program is designed to give you a certain PW at a certain RPM/APP/ICP (obviously there is no map for this, but it all comes out in the wash ) then one fix is to command less PW (multiplier) at that certain RPM/APP/ICP.

Increasing ICP will result in less commanded PW (unless the PW map has been changed...not the PW multiplier map) because the PCM will account for a mass fuel desired difference with the higher ICP and automatically lower the PW.

The low boost fuel maps are a MFD limit. They limit the actual MFD desired to whatever the value is for a given MAP vs. RPM. If you were to lower the low boost fuel to say, "30" across the board, you'd get a total MFD of 30 and have a gutless pig.

Setting the LBF map to an acceptable range while driving like a normal person (it would take some trial and error) and only allowing higher MFD under really high boost conditions would help.

[907DAVE]

<---- thats a good one, thats what I am like everytime I think about this stuff.


If you use the PW Multiplier, it appears you can only reduce PW about 1ms at operating temps. Is that enough?

Or is that value not MS?

More like PW X 1.5 or whatever?

[cleatus12r]

It's a multiplier.

It "basically" takes the desired PW for a given ICP/MFD (in the pulse width map) and multiplies it by the value in the multiplier.

So by all rights, you can either jack up the values in the straight pulse width map to reflect what you want the PW to be for a given MFD/ICP that is not based on EOT so you can really churn out the powah upon first startup on a -10F day........

OR

You can calculate (within fairly close reason) what the actual PW will be if you do some math. The PW multiplier map allows injection pulse width changes based on EOT instead of just allowing a ton of fuel while the engine is cold.

[907DAVE]

So to simplify things a guy could change the PW map to get desired results on a warm engine, then do a little math and apply those changes to the multiplier map? Or would it be just as easy to do this with the multiplier?

[cleatus12r]

You know, for aftermarket injectors that flow significantly different from stock (especially those with larger nozzles) that's probably the direction I would take. Either that or just leave the multiplier map alone and just drive normal until the engine is warm. The base PW map should be changed anyway for large injectors just to get the idle right.

[907DAVE]

Whats the deal with the Adder to PW multiplier?

[cleatus12r]

Well, in it's stock form, the "adder" becomes a "subtractor" to cut back pulse width at high boost levels. "Defueling" anyone?

It starts cutting .1 (I assume ms) at 14.5 PSI at 1400 RPM.
At max, it cuts .7 ms (again assuming) at 23.2 PSI at 2600 RPM.

Some tuning changes that all to "0" so no fuel subtracting is taking place.

[907DAVE]

Could this map be used as an opposite, like subtract (PW?) at low boost?

Or is that what the LBF map is already doing indirectly?

[907DAVE]

Here is an interesting post Charles made on the Nation a while back.

Can you go too lean? As much as we all got a kick out of poking fun at the wizzer on his glorious "lean out" run....

Over the past year or so I have noticed something, and I've made reference to it a few times before. If you pull fuel, you MUST pull timing/icp all else constant. It goes WITHOUT FAIL in my truck, that a simple drop of say 1ms of pw, will result in utter violence from the engine, and the sound of advanced timing. At one point recently I was down to 0 degrees of timing, and 2200psi at WOT just to try and stop it. Couldn't be done. The engine was NEVER happy like that. Running clean as a whistle, and making probably mid 500's, but very, very noticeably less happy.

Back when I was running Jonathan's stuff without alteration on my own, I always noticed that the "hot" file would ALWAYS be much, much smoother than the midrange program. Just smooth as silk in the full on program leaving smoke as far as the eye could see, and rough and ragged in the midrange program running clean as a whistle, and making 50 or so less hp. Working with him on those files a bit, I know for a fact that the ICP/Timing was the same on them.

That taught me two things....

First, more fuel will "soften" an engine out once you crest the smoke limit.

Secondly, less fuel down low will light the FUK out of a charger. As was the case, where my midrange program would blow the tires off just nailing the throttle at times, and zip right up, while the "hot" program would smolder, and smolder and finally light off. Smooth, but sluggish.


Those are basic facts of life with a diesel IMO. Too much fuel at spoolup.... and you get bad sluggish response. Too little fuel after spoolup, and you get ragged, unhappy performance.... that I have NO doubt would kill and engine in short order if left unchecked.



So............. why?

Well, since I can't crawl inside the cylinder and see for myself. All I can do is hypothesize (figured I demonstrate correct usage )

IMO, the spoolup issue is simple. You inject too much fuel and you put the fire out, and get smoldering sh*t going down the line to try and light the charger. Rpm won't come up, power won't come up, and you've got nothing to spin up the charger but cold smoke. That one's easy....

As to needing more fuel up top at full power...

Here's what I've gathered to date. If you think about the likely scenario playing out in the cylinder, you have fuel being injected, heating, begining to burn, and once the burn commences, it can easily burn rather quickly if the stage is set appropriately. Far TOO quickly if you don't watch your ***.

If you just shoot a tiny little spurt of fuel in the cylinder, it will start to burn, and then flash off rather quickly without much issue. No real pressure to speak of, and no real power either because the BMEP will be very low considering the limited crank angle through which it exerted good cylinder pressure. Okay fine. We'll call this a mild program.

So what if you inject say, twice that much fuel now. Well, now you've got the same flashing off, except there is twice as much fuel once it starts to flash, and the injector has also turned off about this time, so there's no more cold fuel (relative to the cylinder temp) being injected that needs a moment to heat before combusting. So? BAM! It all just pops, and flashes off reeeeal quick. When I get in this range with my truck, I call it "crispy". You have to REALLY watch your *** here. A bit too much of ANYTHING and you can create some scary cylinder pressures with modest fuel quantities, and as I said, insanely LOW timing/ICP values. Obviously pulling enough timing would stop it, but now you're pissing away power, and creating heat with this all flashing off late.

So? Add twice again more fuel...... And it STOPS!

That's right. Dowse it down with fuel, and the "extra crispy" bs stops. Immediately, WITHOUT FAIL.

I personally believe this to be due to the fact that you have a constant flow of incoming fuel that will not ever allow the fuel to "flash" off and "round the corner" where it's still in the meat of the cylinder temperature/pressure (near TDC) when you cut the injector off. If you turn the injector off while it's still flashing hard the fuel pocket just EXPLODES, and tried to send your heads into the hood. You can feel it if you've played with timing and cylinder pressure a bit. It is not good.

Trying to pull fuel has proven to be IMPOSSIBLE for me. The only way to calm the truck is to pull boost. That allows me to alter the burn RATE, not the quantity/time. And as such, I'm not really sure how to make good power, without smoking and not be putting extra stress on the engine.

I'm going back to laying fuel down on the ground at WOT and using water to control the EGT.

We'll see.


But I ABSOLUTELY believe that too little fuel/ too much air can and will cause very substantial problems for a diesel engine in certain scenarios.

I see it everyday. If you start burning every drop of fuel, you better make sure you've got the tune SPOT-ON, or I expect you would hurt things in a hurry.

And mattr66's version

what happens to a cutting torch when you go from the proper flame and start taking away the acetelene while leaving the oxygen flow the same.........POP!

Very interesting stuff..........but is defiantly throws a stick in my spokes.