I did the AFC mods including grinding the barrel and grinding the foot flat and set the AFC full back with the preboost screw loose. I set the rack travel with compressed air. The tightest I could get it was full travel at 30PSI or the spring would bind up and I wouldn't get full travel. I tried an old governor spring but it was way too tight.

I've had to turn the screw in at least a couple of turns to get any kind of low end power. I've been adjusting it 1/8 turn at a time. I get a good puff of smoke off idle but it's still pretty sluggish until it hits about 8 lbs of boost which takes about 3-4 seconds.

My torque converter stall speed is 1900RPM and the tranny loves to stay in 3rd gear unless I come almost to a complete stop. I have to shift it into second manually to get any low speed performance which is a pain in the butt.

I'm wishing I hadn't ground the foot flat as the taper would have let the gov arm come forward a bit with the RPM's coming up. Any ideas on how I can tune this thing a bit better?

 

I ended up having to slide the AFC forward a bit and tightening the starwheel 10 clicks. Much improvement in throttle response. It smokes less. I guess I didn't have enough fuel to light the turbo. I can tweak it from here.

 

A long time ago I found an AFC kit with a softer spring that had more usable travel of the AFC, this made tuning trucks with big injectors much easier.

I found that leaving the "hook" on the AFC was really beneficial, because at low RPM the engine does not really have a good volumetric efficiency, meaning you need a good bit of boost to get the same amount of air into the cylinder that you would get at no boost about 500 rpm higher.

As you already found by sliding the AFC housing, you will need 2 parameters:

A. The AFC has to be able to limit fuel (be behind the plate profile at low boost)
B. The AFC has to be able to get out of the way when there is enough boost.

Another thing you should check for driveability reasons is the throttle valve cable. If it is too loose for your tuning the tranny will like to stick in too high gear and lug the engine.

HTH

 

Thanks for the tips. I'm going to try to find another AFC foot and just grind the barrel down. I'll try a softer spring as well.

I move the TV cable sheath back towards the firewall to tighten it up, right?

Thanks

 

With the stock rack plug you can leave the afc barrel alone, it gives you enough travel to clear a reasonable plate for a single turbo.
You will need a lightter spring with a shorter lenght when it blocks, so basically thinner wire.

I prefer to preload the afc spring so that it starts to move at approximately 3-5 psi, and obtains full travel (meaning the flat part of the foot is behind the plate)at about 15 psi.
Then I fine tune with the starwheel.
I prefer quite a bit of pedal movement for a little power in the low power range and only getting aggressive power with the foot really heavy on the pedal. (For city driving, snow etc)
I usually use the TST kit, a whopping 35 US$ for a well sorted kit.
http://www.tstproducts.com/tstafcspringkit.aspx

The automatic tranny knows of your speed, and assumes your intentions from the throttle valve cable.
So tuning the engine to be very aggressive on the first 1/8" of pedal travel leaves the transmission unable to see if you jut want to putt around or if you want to pull houses along the dragstrip.

For the TV cable I like to adjust it so that it has no more travel on the transmission side at WOT, easily achieved by having a helper push the pedal to the metal and fixing the throttle valve lever to the WOT position (bailing wire) and then adjust the TV cable with the pushbutton adjuster to zero play.

Then remove the bailing wire and the helper, discard or recycle according to your regional regulations.

 

Great Info. Thanks

 

The TST kit is on the way. Should I be trying the light or medium spring first?

Thanks

 

I'd try the medium spring first.

 

Will do. Thanks

 

The reason is that with a DTT TC you will have lower stall and more load at low rpm.
So with the medium spring you will have to push the go pedal more at low boost, causing a downshift, and having a better takeoff with less smoke.
Please note how the AFC adjustment influences the shifting of the transmission.
All in all it is necessary to get the engine and the transmission to work together correctly for your driving style and use of the truck.

 

Thanks. I really appreciate all of your help.

 

I ended up getting the kit from a Canadian vendor as TST's price including shipping and exchange was getting close to $100. I tried the light spring first as the medium spring is the same wire size as stock, just longer. It was too smoky with the light spring. Switched to the medium spring and the truck is much more responsive. thanks again for the help.

 

Pleasure to be of help.

Please do not stop tuning now. I think that you are in the ballpark at the moment, but nowhere near bulls eye ( mixing metaphors, I know)
Keep notes on how clicks in this or that direction, movements on the TV cable etc affect your truck.
Only change one parameter a time, and check if it goes in the right direction.

The result of your patience will be a truck that exceeds stock hp and has more usable hp than a new truck no expenses spared, and will fit you and your driving style.

 

I have to bring my governor arm down as it hits the plate about 1/2 way up the ramp with the engine running. I've got the plate 0.070" back from full forward. EGT's top out at 1250. I've tried to get the screws out of the cover before with no luck. I've removed the fuel filter and tried a 3/8 drive screwdriver bit and a ratchet. Any tricks you know of that I can try?

 

It usually helps if you let some good penetrating oil (not WD40, but something like Kroil, LiquidWrench etc) soak for some days.
Then I take a really good screwdriver ( needs to fit perfectly) with a light dab of valve grinding compound on the blade. (Makes it hold and not cam out when you apply torque)
And then, while applying torque, I tap the screwdriver with a hammer to shake the bolts lose.