When these big horsepower diesels really get on it they let out a huge mushroom of smoke. It looks cool and all, but isn't that unburnt fuel or??? Is this any way related to the fuel:air ratio like it is on a gasser. If so, in that regard would a more efficient truck not smoke much if at all?

My truck doesn't smoke much but I'm just curious what makes it smoke (not enough air?)...

 

As a general rule, black smoke =soot and white smoke=unburnt fuel. They are close, but the black/sooty smoke is just burned slightly more completely than the white smoke. Thats my take on it, could be slightly off.

 

Basically black smoke is too much fuel and not enough air.


White smoke is not enough heat (cold engine)


phox

 

Yes. But maximum efficiency and maximum power at the crank are not the same thing.

 

If you had an instantaneous response turbo you'd never have black smoke. But since the turbo needs some time to build up pressure, you'll always have black smoke when you mash on the throttle. Ford is experimenting w/ the variable vane turbo, which is supposed to make the turbo respond faster...from what I hear, their version isn't working so well!

 

the garrett variable vane turbo is more complicated than the holset version of the vgt with just a sliding collar in the turbine housing... i'd love a vgt for my truck once the bombing bug hits hard.... price is scarry though.

 

The variable pitch turbo idea has been out for a long time but has never been perfected to work. Kinda like the Ford Edsel, the Avrocar or my EX-WIFE.

 

There are several reasons that cause a diesel to smoke. I think what you are referring to is A/F ratio. A diesel will make smoke that you can see at around 16:1 A/F and keep making more smoke as the fuel increases. Diesels will continue to make power to around 8:1 A/F before the power starts to drop. It will be making a LOT of smoke at that condition. Now you add the turbo to bring the A/F back to above 18:1 and the smoke goes away and you add more fuel and more boost and the power keeps going up without smoke, until you go past the limits of the turbo, then it starts to smoke again. Then we add propane, water injection, more turbo's, more fuel and you get lots more power but with lots of smoke

 

when i rode in my teachers 05 Super Duty with the Torqshift, the truck didnt smoke at all from a dead stop. the turbo spooled right up.

 

A new truck isnt going to smoke much no matter how you drive it. Emission controls have them by the neck. At least it wont smoke till we get hold of it!

 

njoverkill, Doesnt look like you got the answer you were after. I also dont really know why you read that black smoke is unburned fuel which is supposed to be bad as equaling less power. I do know that it means there is more fuel than air to burn at the optimal combustion efficiency. Now that may not be what these big power diesel guys are after. Because I do know this; that diesels are not like gas engines, in that by letting in more fuel into a gasoline combustion chamber (running rich) you get cooler combustion temps. And if run to rich you get less power. Being what I just said does exclude serious power mods like blowers, NOS, ect since thats a whole different book of rules. BUT when you run a diesel rich you just get higher combustion temps and more power. What we call EGT's. So diesels are more like a furnace. The more wood you shove in there the hotter the fire as long as there is enough air to fuel the flame. I doubt this helped because I to am curious of the question you asked.

 

The black smoke is caused by lack of air so the fuel is burnt but not completely it is in gasser term running rich although gas and diesel engines do not compare if you put a holley Dominator 1150 cfm carb on stock small block it would just flood it out and die where a diesel will not stop building power no matter how much fuel you dump in it but it will cause excessive egt's. So what your seeing is a truck at wide open throttle with high flow rate injectors just dumping in the fuel now when the turbo catches up the smoke will reside. Even with a variable vane turbo I don't think that would ever stop the freight train exhaust just simply because you need exhaust to spool up any kind of turbo. I tried to answer question I hope you get some use out of it

 

The black smoke you see comming out the exh pipe is carbon particulates. It is a product of combustion. It is always present in diesel exhaust. At no load medium rpm it is running at around 75:1 A/F and the particulates are small and very light, you generally cannot see them. When you add fuel to make power the A/F decreases and the particulates go up. When it gets around 16:1 the particulates are getting high enough to see as smoke comming out the tail pipe. When the turbo packs enough air in to keep the A/F above 18 or 20:1 the particulates are kept down and you do not see smoke, and you keep making power. EGT's can be controled this way too but there is more to that issue.

 

Okay, now for another question...

Does increased smoke, and increased exhaust gas temperatures, cause a turbo to build up more boost faster? I know guys that swear the big-time tractor pullers need the unburnt fuel to raise EGT's to incredible levels, because hotter air has a greater velocity and spins a turbo faster. Is there any truth behind that one?

 

I'm getting a little out of my realm of experience on this question. My experience is more on R&D for production applications from the 80's. The smoke and hi EGT's are a result of high fueling and adding propane and sometimes water injection to a diesel motor to increase the expansion in the cyl and forcing it out the exhaust under pressure to spin the turbo to pump or boost more fresh air into the cylinder so you can add more fuel to it. Like I said before the lowest A/F you want to run at is around 8:1 A/F. If you can maintain that A/F ratio under extreme high boost and rpm's, you end up with a real SMOKIN FREIGHT TRAIN!!!!! that screams down the track. There is a lot of new technology that I am not familiar with that will control and maintain these paramaters very closely so you can run on the edge without grenading it before you finish. Old school was a manual 1/4 turn valve on the propane you adjusted while watching the smoke and turn on the water and bump the throttle to get the rpm's up to spool up the turbo's then let out the clutch and open er up and hope she holds together to the end. Now we have computers to do all that for us and new technology.