Is Smoking Bad for You?

[houdel]

Now that I have your attention, I am actually wondering how exhaust smoke afffects fuel mileage. Here is my situation - when I first brought my Deuce home from the DRMO, the engine was hard starting, had all the balls of a neutered poodle (it would only get up to 2350 RPM in 5th on a level road), and would not blow any smoke out the exhaust at all.

I recently turned the fuel adjustment up 1/6th of a turn (two flats on the adjusting nut). The engine fires up right away now and seems a lot more peppy. A few days ago when my wife took the Deuce for a spin (yes, she DOES like to drive it too) I noticed a light smoke plume from the exhaust as she was going through the gears driving away. I also notice a very light haze of smoke as the deuce is idling.

I don't plan on playing with the fuel adjustment any more until I finish hooking up my pre-turbo pyrometer (hopefully I will get that done tomorrow). I want to see what my EGT is doing before I mess with the fuel adjustment again.

But since exhaust smoke is unburned carbon, i.e., unburned fuel, does this mean I am hurting my fuel mileage? Before turning up the fuel, I was getting excellent (for a Deuce) mileage. After 300 miles of easy rural driving, at 40-50 mph, I got about 12.5 mpg.

If I crank the fuel up any more, is my fuel mileage going to go to pot? I was planing on cranking up the fuel till I got a max EGT of around 1100 degrees (to stay a bit on the conservative side) on a long, hard hill, but how will this affect my fuel economy? Will my fuel economy stay about the same as long as I continue to drive conservatively, or is that black smoke wasted money blowing out the exhaust?

A second question - I had my truck at an auto show recently, and had a long conversation with an Army truck mechanic. He stated that turning up the fuel was good for the engine as the excess diesel helps lubricate the cylinder walls. Any thoughts on that claim? Seems to me the excess carbon ends up in the oil, which is not good for the rest of the engine.

 

[JDToumanian]

Hi Lee,
I think what turning up the fuel will do is give you the ABILITY to worsen your fuel economy... Your actual mpg's will depend on whether you can keep your foot out of it! After all, you haven't changed the injectors, so at lighter throttle applications the truck ought to be the same as before.

I bet you can't resist putting the hammer down though, so expext 8-10 mpg like the rest of us get!

As for additional fuel acting as a cylinder lubricant, I'm afraid I am going to have to disagree... unburned "wet" diesel fuel will actually run past the piston rings and dilute the oil which causes scoring of the cylinder / destruction of the honing. This is partucularly a problem at idle.

Regards,
Jon

 

[JDToumanian]

Hi Lee,
I think what turning up the fuel will do is give you the ABILITY to worsen your fuel economy... Your actual mpg's will depend on whether you can keep your foot out of it! After all, you haven't changed the injectors, so at lighter throttle applications the truck ought to be the same as before.

I bet you can't resist putting the hammer down though, so expext 8-10 mpg like the rest of us get!

As for additional fuel acting as a cylinder lubricant, I'm afraid I am going to have to disagree... unburned "wet" diesel fuel will actually run past the piston rings and dilute the oil which causes scoring of the cylinder / destruction of the honing. This is partucularly a problem at idle.

Regards,
Jon

 

[JDToumanian]

Hi Lee,
I think what turning up the fuel will do is give you the ABILITY to worsen your fuel economy... Your actual mpg's will depend on whether you can keep your foot out of it! After all, you haven't changed the injectors, so at lighter throttle applications the truck ought to be the same as before.

I bet you can't resist putting the hammer down though, so expext 8-10 mpg like the rest of us get!

As for additional fuel acting as a cylinder lubricant, I'm afraid I am going to have to disagree... unburned "wet" diesel fuel will actually run past the piston rings and dilute the oil which causes scoring of the cylinder / destruction of the honing. This is partucularly a problem at idle.

Regards,
Jon

 

[houdel]

Thanks, Jon. I get the point. But I think just a single reply would have been sufficient sufficient sufficient. I DO try to keep my foot out of the throttle, I just wonder how much $$ that smoke is costing me. I remember in the old days when diesel trucks spewed smoke like a battleship at all ahead emergency, nowadays you hardly ever see smoke coming from the stack of a modern diesel. Maybe I just need a bigger turbo with more boost to get more air into the cylinders so all the fuel is burned, but oh my, I just LOVE to hear that "C" turbo whistle! Any ideas on how to increase the boost on a "C" turbo? Mine maxes out at about 7+ PSI, which really sucks. Dr. Foster is selling his super turbo kit for something like $1000-$1200, but that is out of my price range and they don't whistle anyhow. What I need is a whistler that puts out 10-15 PSI. Anyone ever try a dual "C" turbo mod? Now THAT would be a real trip!

 

[cranetruck]

If you are looking for more boost, install a "D" turbo. I can easily achieve 12-13 psi with mine. Have to watch the EGT, though.
You shouldn't have any smoke if you "work" with the IP when driving, shift gears at the right time.
If you are concerned about fuel in your crankcase oil, have it analyzed...

 

[houdel]

Bjorn - I upshift around 2000 RPM, downshift around 1500 RPM. Is this appropriate for conservative driving? I am hoping to keep this engine running until I am no longer able to drive the Deuce, which I hope is a couple more decades (I just turned 60 years young (I have 6, 8 and 10 year old sons at home with me) 3 days ago). How low a RPM would you consider "lugging" the engine? The smoke I am seeing is a very light haze, not a dense cloud of smoke like you and I remember from the "good old days". 12-13 PSI would be nice, but I like to hear the turbo whistling. Does a "D" turbo have a silencer ring which can be removed to make it whistle?

BTW, glad to see you made it home safe and sound after your great western adventure! I'm happy to see the return trip was without any of the "excitement" you experienced heading out west! Got to hear more about your XM757, sounds like you scored a rare find!

 

[cbvet]

"Expect 8-10 MPG like the rest of us"?
My deuce starts instantly, runs great & smokes quite a bit.
But 5 MPG is it when travelling at 50-55 MPH.
Eric

 

[cranetruck]

Sounds about right Lee, with the open top it's easy to monitor the exhaust too as well as to listen to the engine.
5th gear most easily gives you the smoke when loaded down and the EGT pops right up along with the boost.
These gauges are a "must" and I haven't even turned my fuel delivery up!

I don't know how high the boost will climb, since at 12 psi, the egt will reach 1,200°F and I ease off.

As far as driving slowly on the interstate, somebody askead about it, no problem. The minimum is usually 40 mph and when I go below that, the flashers come on.
The truckers are the only ones that care, it seems, and they have no problem with a vehicle going too slow if the flashers are going.
I sometimes even passed trucks on long inclines where they got bogged down too after running out of speed.
Needless to say, I used the 4-way flashers a lot when towing the 8x8 or the laundry trailer, probably totalling hours every day.
Got about 7 mpg towing, much better when "empty". The truckers I spoke with talked about fule milages of between 4 and 5 mpg for their big rigs.

 

[WillWagner]

Lee, did you change the fuel filters? If they're plugged, it can cause hard starting and low power. Also, is the in tank pump running?

 

[Pinkie]

Normally turning up the IP you are turning up the MAX fuel delivery, not the mix on other diesels I have worked on. ( I usually work on Internaltionals and John Deeres and some Cats). Turning up the IP will decrease fuel mpg and increase black smoke. Black smoke is unburnt fuel. You also run the possibility of washing out the cylinder walls. This risk decreases with a turbo because you are driving more air for the fuel to be burned more completely. The modern diesels hardly smoke at all, this is true, computers control the air intake and the fuel intake to the engine making adjustments as the motor works. This leads to a more efficient deisel engine, meaning little to ne smoke. I have a 3208 cat that is turned up to max smoke without a turbo. That engine smokes like a frieght train, but it does have A LOT more power than it did. The other thing to think about is alot people do not understand diesels and the more smoke they see from the stacks the more they do not like them due to environmental issues the people may have. I hope this helps.

 

[houdel]

Will - In tank fuel pump is working well, I replaced all three fuel filters, did not improve starting at all. As soon as I cranked up the fuel the first 1/6th turn (one flat of the adjusting nut) starting was markedly improved, with 1/3rd turn (two flats) the engine starts immediately without using the accelerator pedal. Very impressive, compared to what it had started like before.

 

[JDToumanian]

Hi Guys,
Sorry about the duplicate posts, I had a major meltdown and was offline for a few days.



I remember reading somewhere (maybe here on SS?) that the fuel injectors in a multifuel, with their two-hole tip design, were not designed for optimal efficiency... Rather, they were designed to reliably inject fuels of varying viscosities and caloric values. That may explain why our trucks tend to smoke some, compared to a modern design.

Eric - My truck likes to go 52-53 mph at 2400 rpm. It's possible to go faster, but my fuel economy goes to crap, and my foot is pretty close to the floor all the time. From reading posts from others here, I know I'm not alone... That extra 2-3 mph really costs you! Try going a little slower and I think you will get the 8-10 mpg that seems to be very common. Failing that, I might check for dragging brakes or parking brake, and check my air filter.

Regards,
Jon

 

[cranetruck]

Jon, your deuce doesn's smoke running all out (55mph) on the way to Barstow.
Did you get the transfer case problem fixed?

 

[ken]

Lee, what color is your smoke? White/gray is unburnt fuel. Black is burn't carbon. And blue is oil. When we set up a ship's engine we look for black under acceleration only. If your black while crusing, you've gone too far. If it's gray/white before the engine is warm then maye you have a dribbling injector? But after you get your guages installed you'll be able to tune it in.

 

[FSBruva]

Lee-

I trust your judgement on whether or not it's oil (blue haze). But, for those members who are reading this, wondering about their blue smoke, I have an interesting factoid.

I was reading the 1992 version of the -34 manual, and if engine smokes under normal operation (idle, cruising, accellerating) you should to monitor the oil consumption. The test procedures are to make sure your dipstick says you're full for oil, then take the beast out on the road and run it. Check your oil level periodically, and note how far you drove before you were 1 quart low, by the dipstick. If you drover farther than 60 miles, that is "acceptable oil consumption." So, for everyone who has a little bit of the blue haze, it's natural.

Matt

 

[JDToumanian]

Jon, your deuce doesn's smoke running all out (55mph) on the way to Barstow.

Hi Bjorn,
Thanks for the pic! That was a lot of fun... My first "convoy"!

Once up to speed, my deuce doesn't smoke... it's only on acceleration. Even then, it's not too bad... but enough that I can see the smoke's shadow on the ground. I've never seen any blue or white smoke.

As for the transfer case problem (popping out of gear on deceleration), I adjusted the linkage and the problem seems to have stopped. I don't doubt there's still a problem with that unit - the stack of tiny washers on the shifter detent's plunger was the giveaway - but if it's an infrequent problem I'll wait until it gets worse. I don't feel like pulling it out again any time soon!

I'm amazed that adjusting the shift linkage "solved" the problem... I had never seen the shifter hit the passenger seat - which must be how it was getting popped out of gear - there was "plenty" of space there. But although those resilient mounts for the transfer case don't look very "resilient", they must have been allowing the transfer case to move enough for the shifter to hit the seat.

Whatever, I'm just glad the problem went away!

Regards,
Jon

 

[SETOYOTA]

I never realized fuel mileage was such as concern for M35 owners. When my truck is empty I put put more fuel in it. By the way I think I hold the stock deuce land speed record of 66.33 MPH

Chuck

 

[clinto]

I never realized fuel mileage was such as concern for M35 owners.

That's the primary reason why I bought mine…….

 

[rdixiemiller]

No more than I drive mine, fuel economy is not a real issue. I will be making the trip to Aberdeen this next year, so I am saving up my pennies. I do get between 9.5 and 10.5 mpg, depending on speed and front flanges on/off.