Tune, Power and Smoke Question - Diesel Truck Forum - TheDieselGarage.com
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post #1 of 10 (permalink) Old 05-31-2006, 10:40 AM Thread Starter
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Tune, Power and Smoke Question

It seems that the higher power the tune the more smoke that is made. If smoke is unburned fuel, why is this necessary? It seems that is wasted fuel. Is it not possible (with today’s electronic controls) to put in all the fuel that is necessary to make the power and all that can be burned without putting in the excess that makes the smoke, or is it just something with diesel motors that they have to always have excess fuel to make maximum power? Just a curiosity question. I personally would prefer maximum power with very little smoke. Prefer not to call attention to myself any more than necessary, but rather have power with smoke than not have power. How about it all you custom tuners and any other knowledgeable members? Thanks in advance for any and all knowledgeable replies.
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post #2 of 10 (permalink) Old 06-02-2006, 11:11 PM
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Your question is a good one. I always used to think smoke meant wasted fuel, which meant less power, but I gave it some thought after reading your post. Imagine things at the molecular scale. And this is a huge over simplification, but it might help explain things (really, we need a diesel combustion expert that knows the theory of combustion wave propagation, etc....but for now its just us chickens).

For a certain engine set up (turbo, IC, etc.) and ambient conditions, you get a certain air charge per stroke. If you shoot just the stoichiometric amount of fuel, we can simplify that to be a table with equal numbers of white balls (oxygen) and black balls (fuel). To get combustion, a black ball and a white ball have to meet. Since your rate limiting ingredient is oxygen, to guarantee you burn every last molecule, by adding an excess of black balls (diesel), you further guarantee that each white ball will strike a black ball. That is, some additional power is possible with an excess of fuel. There are penalties though, like high EGT's, etc. How important this is, I don't know. Might be a 1% gain, in which case it is not worth the smoke and heat and pollution. But maybe it is 10-20%...in that case, for pure performance, it is probably worth it.

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post #3 of 10 (permalink) Old 06-03-2006, 02:28 AM
 
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RL is correct once again,
outside of serial dyno/track runs the only way to know your at saturation maximum white + black balls..is when the black balls start rolling out the exhaust....now that said with the SCT pro race software you could just keep increasing fuel incrimentally untill that point and back off a little....and then just tune your excess at wot so the normal driving stuff is clean....thinking outloud...
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post #4 of 10 (permalink) Old 06-03-2006, 04:03 AM Thread Starter
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Thanks for replies, what Ralpinnj said does make sense, and what Jschall said is what I was trying to get at. Get Hp up then back off fuel enough to get rid of smoke but not enough to cut power. With old mechanical controls that was not too accurate, but it seems that with these new electronic controls it could be done.
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post #5 of 10 (permalink) Old 06-04-2006, 02:32 AM
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That is Banks theory, and obviously it doesn't quite work. I have read in several places where a stock truck(Maybe intake/Exhaust) with a hot track SCT tune, has beat a Banks 6-Gun equipped truck on level 6, without any problems. The differance being the SCT will belch black smoke, and the banks will only maybe put a puff out. I think you always need excess fuel in a diesel to get the most power out of it, but hopefully one of the experts, like DJ will reply.

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post #6 of 10 (permalink) Old 06-04-2006, 02:41 AM
 
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Notice I said tune your excess at wot...:evil:
who's the expert...:
ok Eric's reading the thread and he is an expert...and will now make me look silly or stupid....
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post #7 of 10 (permalink) Old 06-04-2006, 04:52 AM Thread Starter
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Yea,Of course if you are racing, no one cares about smoke,just winning.
However, if you would rather be a sleeper on the street, and you could maybe give up 2-3% power for 40-50% reduction in smoke, I would prefer that. Maybe not possible, just wandering? Where are the experts?
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post #8 of 10 (permalink) Old 06-04-2006, 03:51 PM
 
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Fullservice,
I don't know whose tunes you are running or if you even have an sct but even with my fule system I can drive arround town without making much smoke untill I dig deep into the pedal...Im a huge fan of the whole sleeper work truck thing....
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post #9 of 10 (permalink) Old 06-06-2006, 03:56 AM Thread Starter
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Just 2000 miles on truck. Just got a SCT 9415, not happy, in process of converting to custom tunes (9400). Hope it is a lot better. Everyone says it will be.
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post #10 of 10 (permalink) Old 06-06-2006, 01:15 PM
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RL, I liked your analogy.

Here is a simple equation:
more fuel = black smoke = power

However, you should not be smoking under normal driving conditions. Only when you are on the pedal.

At first you will have smoke because the turbo has not started to spool and you will always have smoke at WOT.

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