Black Smoke Question/Manual Transmissions VS Automatic Transmission s

[brandongarnold02]

I have a 94 K3500 converted to a mechanical pump. I have an NV4500 trans and the issue I am having is there is a puff of smoke pulling off from a stop but seems to be healthy but I also get some smoke at times when I'm in 5th gear at about 45mph and accelerate. I also see it at other times to but it's when I'm cruising at a low rpm speed and accelerate. I didn't know if this was a characteristic a manual transmission and having the capability to drive at low rpm and the trans won't automatically downshift on acceleration or if I need to make an adjustment to the fuel. I have messed with the fuel adjustment before and I had it set this high and turned it back down 1/8 but seems to loose a noticeable amount of power so I then turned it back up.

[Robyn]

Hi

Everything you describe sounds normal.

At a take off the turbo is not spooled up and there is slightly too much fuel, resulting in the puff of smoke.

The smoke when increasing speed from light cruising is the same thing.

The best setting is to get a clean stack when pulling hard or reasonably so.

If you are "Rolling coal" under hard load then the fuel setting is too high or there is not enough boost.

Get a boost gauge on the intake and a pyro in the exhaust manifold or cross over pipe at the outlet of the manifold.

You can then see what boost you are making and when, along with what the EGT (EXHAUST TEMP) is.

Max boost should be no more than 15 psi under hard load with the pedal mashed to the carpet and the engine loaded well.

Exhaust temp at the exhaust manifold outlet should not exceed 1000 F under hard load.

What sort of Waste gate controller are you using ???

Robyn

[brandongarnold02]

Thanks for the input. I have a homemade wastegate and I have a boost gauge but no pyro gauge as of now. I get about 10lbs of boost and I don't get a constant cloud of smoke when cruising. I just get some light black smoke swirl up and I can see in the rearview mirror with light acceleration from 1500 rpm or so as you said to be normal. Under a hard acceleration the boost shoots up and there really isnt any smoke that I can see from the mirrors anyway. Its hard to make out how much smoke is really coming out at times just by seeing it in the mirrors but I don't want to be the one smoking people put behind me but like I was saying it runs a lot better where the fuel setting is now.

[DmaxMaverick]

Sounds normal to me. Some smoke on acceleration is normal. If it clears under load, no worries.