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air/fuel/smoke questions

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If I understand it correctly, a lot of smoke is indicative of unburnt fuel, right? Low amounts of smoke at high-load or full-throttle applications would seem to indicate maximum efficiency or an ideal fuel/air mix. For me, that means "rolling coal" is a bad thing, so I want to minimize smoke production, even at high-load, full-throttle applications.

I'm trying to work out in my head how I can tweak for more power without wasting fuel and dumping my efficiency in the toilet.

Turning up the star wheel 'til you get smoke, then backing off a touch, that makes sense. If you get too much smoke, just back it off a touch more. I get that. But let's say I increase fueling by changing the fuel plate or installing bigger injectors and get a lot more smoke, does that mean that I need to provide the engine with more air? A more efficient exhaust manifold can help the turbo be more efficient, so I assume that provides more air. A better intercooler increases air density; does that let the engine use fuel more efficiently?

Once you get past those things, if I've already got a high-flow intake installed, does that then mean that you need to upgrade the turbo?

I guess I'd like to go as far as I can, efficiently, without changing the stock turbo. What kind of HP/TQ numbers could I see, maximizing fuel/air efficiency? Or am I completely wrong about this whole thing?

Opinions? Facts? All are welcome, and thanks. :yourock:
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Well that kind of a catch 22. Yes, less smoke means more efficency. But once you start adding fuel, you then develop power. I noticed better mileage after I started adding fuel, as long as I was easy on the go pedal. Some people claim that smoke is wasted fuel, and taht the motor isnt as efficient as it could be. And if your looking for more power without smoke, and use the same turbo. Your most likely going to be dissapointed at your max levels.

Is it possible to develop big power without excessive smoke, But tuning and additional airflow is a must.
 

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Discussion Starter · #3 ·
Well that kind of a catch 22. Yes, less smoke means more efficency. But once you start adding fuel, you then develop power. I noticed better mileage after I started adding fuel, as long as I was easy on the go pedal. Some people claim that smoke is wasted fuel, and taht the motor isnt as efficient as it could be. And if your looking for more power without smoke, and use the same turbo. Your most likely going to be dissapointed at your max levels.

Is it possible to develop big power without excessive smoke, But tuning and additional airflow is a must.
I'm really not in this for the power. If I can get 250-300hp out of a mildly-tweaked 12v, then I'll be ecstatic. My truck's a daily driver and needs to be a workhorse for another decade (it's only got 130K on the ticker). Big power's just not necessary for me.

BUT, I know that I can gain power and efficiency to a point. So, I'm okay with adding fuel, particularly by changing injectors, because I know that most aftermarket injectors are more efficient; thus better mileage plus more power. What I'm after is the best combination of efficiency (first) and power (second).

When you say "tuning" what do you mean? Are you talking about adjusting timing? What else is there to "tune" in a 12-valve? By "additional airflow", I assume you're talking about changing turbos. I don't think that's even on the table. If I have to change turbos to get the air I need for stage 1 sticks, then there's no way I can make the efficiency gains pay for the investment.

Little stuff (stage one injectors, exhaust manifold, maybe intake manifold, maaayybe intercooler, propane, timing adjustment, star wheel adjustments, fuel plate change) I can see paying for themselves in efficiency gains, with the increase in power being a bonus. Get much beyond that, though, and it starts looking like I DO need to add air/turbo, and I'm just not after those kinds of numbers.

I was just doing some thinking about where I want this truck to go, and that made me wonder about that balancing act of applying fuel but not air.
 

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Mileage

The first couple of mods I did the mileage went up almost 2 MPG. But then the next things I did and the way you drive it, well lets says pedal to the metal, not good for mileage.
4 inch exhaust and a BHAF will help, Go to 3.55's slow the motor down will help. My brother took out the dana 80 and put in a 70 so he could have a 3.08 ratio.:lol4:
 

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Discussion Starter · #5 ·
The first couple of mods I did the mileage went up almost 2 MPG. But then the next things I did and the way you drive it, well lets says pedal to the metal, not good for mileage.
4 inch exhaust and a BHAF will help, Go to 3.55's slow the motor down will help. My brother took out the dana 80 and put in a 70 so he could have a 3.08 ratio.:lol4:
If you'll look at my sig line, you'll see that I already have a BHAF and 5" exhaust... :doh: And yes, I did see ~ 1.5 mpg increase with those mods, as well as a slightly noticeable increase in response to the go pedal.

Back to our originally scheduled discussion of fueling and air flow... Anyone have any more input relevant to my questions?
 

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the I see it you can not make big power with no smoke bottom end before the turbo/turboes lite you will get smoke then it will clear up if tuned right, banks uses alot of nitrous while racing and it burns up the extra fuel, here is a vid of a truck from here in idaho and it shows a good tuned truck its a dmax though, which they have more tuning capabilities. http://www.youtube.com/watch?v=ZyzE...read.php?t=740&page=3&feature=player_embedded
 

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Discussion Starter · #7 ·
the I see it you can not make big power with no smoke bottom end before the turbo/turboes lite you will get smoke then it will clear up if tuned right
That makes sense. I'd be overfueling, but only 'til the turbo spools up. So it sounds like I'm on the right track: Smoke (on the top end) means you need more air. Beyond a few efficiency tweaks (manifolds, intake and intercooler), the only way to add air is with a turbo.

Now: Let's say -- on top of my current setup -- I put in stage 1 injectors, more efficient intake and exhaust manifolds, and a better intercooler, and tweak the timing (or give it a very small shot of propane). Is 300/600 (HP/TQ) a realistic expectation with that setup? If not, what kind of numbers would I be looking at?
 

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I'd think 300/600 would be definitely hit with that. Even though you have the 94, which is the lowest stock rated 2nd gen 12valve, the injectors, more air flow in and out and through the intercooler and the timing/pump tuning... should hit your mark for sure. Propane I've never tried, but thought of... just the kits are so expensive. I've always read that it is more a catalyst than performance because it makes fuel efficiency in the Cummins way better.
 

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Discussion Starter · #9 ·
I'd think 300/600 would be definitely hit with that. Even though you have the 94, which is the lowest stock rated 2nd gen 12valve, the injectors, more air flow in and out and through the intercooler and the timing/pump tuning... should hit your mark for sure. Propane I've never tried, but thought of... just the kits are so expensive. I've always read that it is more a catalyst than performance because it makes fuel efficiency in the Cummins way better.
Yeah, you're right about propane. It adds about 10% to your power numbers. I'm going to build a home-brew kit. Pretty cheap, and easy to do with the 12v (and it's almost identical to the kits you'd buy for a 12v; 24v and up is a different story). There's a LONG thread on here somewhere about it.

RE: pump tuning. Are you talking about star wheel? What else is involved in tuning the pump for a bit more fuel?
 

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Fuel plate, sliding the AFC housing forward, starwheel, and the pre-boost screw. Delivery valves might be a good choice for you too, even the stock 215hp pump ones, the 191s I believe.
http://www.cumminsforum.com/forum/94-98-tech-articles/922-turning-up-p-7100-pump.html
Here's an article on tuning up the pump, there's a lot than can be done. Truthfully, you could have the possibility of dumping TONS of fuel whenever you want, and keep the pre-boost and starwheel settings so that the fuel isn't crazy high until the boost is up, as well as keep your right foot out of it a little lol
 

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Discussion Starter · #11 ·
Fuel plate, sliding the AFC housing forward, starwheel, and the pre-boost screw. Delivery valves might be a good choice for you too, even the stock 215hp pump ones, the 191s I believe.
http://www.cumminsforum.com/forum/94-98-tech-articles/922-turning-up-p-7100-pump.html
Here's an article on tuning up the pump, there's a lot than can be done. Truthfully, you could have the possibility of dumping TONS of fuel whenever you want, and keep the pre-boost and starwheel settings so that the fuel isn't crazy high until the boost is up, as well as keep your right foot out of it a little lol
Sweet! Thanks. That's the first I've heard of the pre-boost screw.
 
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