I have been running the same AFC adjustment for a couple of years now -- about an 1/8" pre-load on the spring when you screw the cover down.

The truck definitely had a steep increase in torque around 1700 rpm, and was a real dog below that engine speed. I simply attributed this to the "negative torque control" mechanism in the injection pump governor assembly. Dave (wannadiesel) had suggested a while that I tweak the AFC a little more to help with the low-end torque -- I didn't think that it would make too much difference, since I figured I was getting max fueling at around 8 psi of manifold pressure, and I could get the manifold pressure up there at 1500 rpm . . .

Well, the other night I finally decided to take the AFC cover off, and turn the star-wheel down farther: not even a quarter turn and I was out of threads! So, I took the wheel out, and put the spring back in. This left me at approximately no pre-load on the spring. Now, below 1500 rpm under load, I have slight haze, then the turbo starts to spool and I get some black smoke until I get up to about 8 to 10 psi of manifold pressure, and then she clears up again. The torque curve feels much, much smoother below 1700 rpm, and it sure makes the shifts from 2-3-4 easier. Now all I have to do is take the nut under the starwheel out, and put the star wheel back in (and figure out how to keep the lock-springs in place) to increase the pre-load just a little bit more and cut down on some of that low boost smoke.

So, I am not done yet, but it really makes a big difference in low-end drivability!!

On another note -- I left my day job, and am no longer sitting in front of a computer plugged into the internet all day long -- so my apologies in advance if I miss and skip a lot more stuff.

 

you left your day job so you could spend more time with your truck? that's great! wish i could...

 

Thanks for the update, Alec! Every little bit of tweeking helps.

 

It's amazing what a little excess fuel will do for spoolup.

When you take the nut and ratchet spring out, try just running the star wheel to the bottom and see how it runs. With the spring pushing on the star wheel it will not tighten up on you. If you need to raise it a little, just drop some shims under it. It'll stay down.

Now go get a 3200 RPM spring and hack on the AFC lever while you're in there.

 

The star wheel was actually bottoming on the housing, not the nut that holds the locking spring in. I ground the bottom of the star-wheel off flush, and then removed the nut underneath it and ground it down so that it was flat. I'm about half a turn from bottoming out now, and seem to have all of the spool and almost no smoke. So, I am happy.

The only reason I am so smoke averse is the stupid people who think that diesels are worse for the environment than gasoline engines -- just because you can see soot but can't see most volatile organic compounds!!

I can't believe I drove around for a couple years thinking that I needed to change the torque control device when I could just squeeze that low end out of the AFC. The way I have it set up now, the truck really takes off smoothly from 11 to 1200 rpm (though there is noticible turbo lag until about 14-1500). Makes that 2-3 & 3-4 shift possible.

BTW: After installing the 4" exhaust I am now getting about 26-27psi max boost instead of the 23 I was seeing before.

Working on the truck at all Greg, or is it all house all the time?

 

3200 RPM spring!

 

''Working on the truck at all Greg, or is it all house all the time?''

Little bit of both---can't give up on everything fun! We've downsized the house to keep it affordable, but the good news is that I FINALLY got my hands on one of those slow-speed lister-style diesels, so I'm a Trace 3624 inverter and some batteries away from being off-grid! Oh yeah, and a gen head, hehe.

end hijack.