Engine/Transmission (1994 - 1998) Smoke vs Mileage

[kenny61]

How much difference does turning back the star wheel (less smoke) make regarding fuel mileage?

 

[charlessmith]

Since black smoke is unburned fuel, less smoke will mean better mileage. Either turning back the star wheel, or in extreme cases sliding back the plate a bit will get rid of the smoke. Or a lighter right foot.

After "improvements", my '97 would outsmoke most everything else from a stoplight. I ended up needing to slide the plate back a little to really get rid of most of the smoke. That was worth several MPG for around town driving. Before I started the smoke reduction program, even a very light foot still made smoke.

After "adjustments" fuel mileage around town went from (maybe, as I can remember) about 13 to about 17. Another benefit, I stopped turning the corner of the camper black. You can see from the picture, the back right corner is a prime candidate to turn black from smoke.

 

[kenny61]

I dont smoke that much. it puffs when i normally go thru the gears however nailing it will result in blacking out the roadway... ..... For 4mpg I'll try turning it down and see what happens. I forgot which way that is on the star wheel. Should i bring the top of it towards the wheel well or towards the engine?

 

[hsmith]

If my memory serves me, toward the wheel well is the way you want to go to decrease tension. Someone correct me if I am wrong.

 

[tp0d]

hsmith: yep. .

standing over the drivers fender, turning towards the passenger side (clockwise) == more smoke. counter clockwise == less

-j

 

[bmoeller]

If my memory serves me, toward the wheel well is the way you want to go to decrease tension. Someone correct me if I am wrong.

You are close. Will actually INCREASE the tension, not reduce it. More tension= more required boost to increase the low boost fueling.

 

[kenny61]

Thanks Guys. .

 

[abranz]

Man am I in the same boat. After mild upgrades like ddp 1 injectors (50hp), timing set to 16 degrees, and a #8 tst fuel plate the truck will smoke horribly when taking off or shifting at low boost levels. I've messed the star wheel many times and have it smoking less but I'm not pleased and wish I would have never spent the money on these upgrades due to the large amount of smoke. I've had the entire intake system checked for boost leaks and there are none. The truck runs fantastic but I absolutely am not pleased with the smoke. I've had a diesel mechanic work on it and his response is smoke is normal with 12 valves when modified. I understand that, especially if I would of gone crazy with high hp/torque upgrades, but I didn't specifically so I could avoid the excessive smoke. Nobody's fault but my own. I'm slowly returning it to stock and can't figure out what I was thinking before I started this. Heck, it's lasted 13 yrs and done everything I've asked of it. Thanks for listening.

Tony

 

[WaynesWorld]

kenny61,

You may want to go a step further.

Turn the star wheel back & move the AFC housing back all the way.

It worked for me.



WAYNES WORLD

 

[kenny61]

I've had it with minimal smoke but the power is less, If turning it down will give me 4mpg I'll give it a try. $173. 50 to fill er up is killing me

 

[Forrest Nearing]

Man am I in the same boat. After mild upgrades like ddp 1 injectors (50hp), timing set to 16 degrees, and a #8 tst fuel plate the truck will smoke horribly when taking off or shifting at low boost levels. I've messed the star wheel many times and have it smoking less but I'm not pleased and wish I would have never spent the money on these upgrades due to the large amount of smoke. I've had the entire intake system checked for boost leaks and there are none. The truck runs fantastic but I absolutely am not pleased with the smoke. I've had a diesel mechanic work on it and his response is smoke is normal with 12 valves when modified. I understand that, especially if I would of gone crazy with high hp/torque upgrades, but I didn't specifically so I could avoid the excessive smoke. Nobody's fault but my own. I'm slowly returning it to stock and can't figure out what I was thinking before I started this. Heck, it's lasted 13 yrs and done everything I've asked of it. Thanks for listening.

Tony

how is your AFC set up? I had Dragon Flow injectors and an sps62 with no fuel plate on my '98. That's about a 200hp injector and NOT a "clean" one by any stretch. But I could set up the AFC so that the truck would not smoke at all.



the AFC setup is KEY

 

[abranz]

Thanks for the reply. I've turned the afc counterclockwise increasing the spring tension until the star wheel won't turn any further. Today, I loosened the afc 4 fasteners and slid the housing fully towards the rear. I still have smoke! However it did make a difference reducing the amount when I take off or shift. The truck makes 28 psi boost, has the elbow supplied by tst in the wastegate. All boost clamps and boots inspected and I cannot find any boost leaks. EGT's are fine (500-800). Timing was set by a very good mechanic at 16 degrees. I've put the original fuel plate back in which didn't make as much of a difference as sliding the afc housing rearwards. I really don't want to go back to original injectors since I've spent all the money on ddp's and tst-fuel plate. My original thoughts in changing the truck were to get a little more power for pulling our camper without decreasing my mileage to much. Any thoughts? Thanks. Tony

 

[abranz]

I just realized what I've done and apologize for hijacking this thread but I hope any gained information is useful for all.

Tony

 

[MMcCallie]

Tony, no worries. I don't think you want to get rid of your upgrades. Everything I've done to my truck has given me more power and better fuel economy. Under heavy throttle I have tons of black smoke with my custom ground plate, star wheel, and AFC housing all slid fully forward. But, I can drive around it all for the most part if I keep my RPMs up a little higher and accelerate lightly. The water injection cleans it up as well.

I am very curious to know if others have gained a few mpg by detuning their fuel pump. As I mentioned, everything I've done to mine has given me more power and mpg, twice getting a best of 17 mpg but averaging 15-16 mpg. This is compared to the old PSD 7. 3 that smoked about as much while making very little power and only got 11 mpg all the time.

Will it make a difference to just drive with a light foot so that you hardly ever see smoke vs. actually decreasing the amount of fuel? Seems to me if we drive more cautiously that we still have more power on tap at the same RPM driving lightly than if detuned. Having more power means less effort to get the same amount of work done and should mean better fuel economy because the engine has more capability than is needed. Am I way off base here? Probably only one way to find out.

 

[Forrest Nearing]

what altitude are you at? how's the weather? when did you install the injectors? still have the stock turbo?



surprised you have so much smoke. my current 98 will smoke a ton with DDP4's, custom plate, modded AFC, etc. but I can also drive it without any smoke if I hawk-eye the pass mirror



what gear do you start out in? what RPM do you usually shift at?

 

[abranz]

Wallace is @ about 2500ft, the injectors where installed two months ago, the turbo and rest of the truck is stock and I start off in 2nd. Where I notice the most smoke is when I shift to 3rd and again when shifting to 4th. I run the rpms somewhere over 2200 when shifting in attempt to not have the rpms fall to low when engaging the next gear. I think I should do a mileage check on a trip but with fuel prices I've been driving my vw tdi more and more. Interesting thought is that I upgraded the vw's injectors one size, bumped the timing to the upper acceptable limits and acheived what I was looking for which was more power, better mileage (53mpg if driven the same) and no increase in smoke.

Tony

 

[Forrest Nearing]

I'd rap it out to 2700 or so

 

[Vaughn MacKenzie]

abrantz something doesn't sound right with your truck. . . a #8 is a lot of plate for a 215 5-speed truck (not recommended on TST's site) but if it's still smokey with the stock plate something is a little out of whack. Did you have the #8 in the middle? Maybe try stock injectors with the #8 & see what that does (incase there is something up with the injectors but I've never heard of a "bad" set coming out of DDP). I've seen pretty strong trucks with stock 215 injectors & #10 plate with minimal smoke. My '98 auto with 300 injectors & #10 plate in the middle was pretty clean, a little haze at WOT and a puff if I stabbed the pedal.

 

[bmoeller]

After mild upgrades like ddp 1 injectors (50hp), timing set to 16 degrees, and a #8 tst fuel plate the truck will smoke horribly when taking off or shifting at low boost levels.

Where is the AFC sitting at? Full forward will cause higher fueling and more smoke. More timing will cause more smoke. Where is the plate sitting? Can slide it back some.

I've had a diesel mechanic work on it and his response is smoke is normal with 12 valves when modified. I understand that, especially if I would of gone crazy with high hp/torque upgrades, but I didn't specifically so I could avoid the excessive smoke.

The mechanic is correct. A modded 12v will smoke. With the mods you have, a better turbo will help. I'd get a HTT 62/12. Spolls quick and moves more air than a stocker.

 

[abranz]

Hey, thanks everyone for your ideas.

The truck has a 180 pump as I recently converted it to a manual. I spoke with Mark at TST and he reccomended either the number 5 or 8 so I chose the #8 thinking it was more conservative. #8 is the recomended plate for that pump according to his chart.

The plate is about midway in its travel where the original plate was. I slid the afc housing to the rear of its travel and increased the spring tension siginificantly by turning it counterclockwise if looking forward while standing by the drivers fender. Mabey I went to far without further mods such as a turbo, etc and as I said earlier I've got nobody to blame but myself. However, the manual conversion went great and I'm very pleased with that aspect. It's been a great truck for many years and I would like to keep it that way. I removed the #8 plate and put the original one back. I was ****** at myself for wasting the money but today I put just about the same in the tank, what a joke, $4. 80/gallon. Tony