Engine/Transmission (1994 - 1998) AFC setting and fuel economy

[JGheen]

I have a question about the AFC star wheel and fuel economy. Ever since I installed my #10 plate and gave the AFC wheel about 30 clicks, I get a decent amount of smoke on take offs and it clears up after the revs and boost pick up @ about 1700-1900 rpms. The get up and go from a complete stop is great but a little too much smoke when I stomp on the throttle. My question is if I back off on the AFC wheel a bit to reduce that pre-boost smoke, my fuel economy should go up a bit, in theory, right? Also, how much get up and go will I loose by reducing that pre-boost fuel?? I know I can figure it out from trial and error but I have little time during the day to mess with the rig for testing the different AFC wheel settings, so I thought I would ask the experienced if they had noticed any difference in power and mileage.



Thanks, Joe

 

[Joe G.]

I doubt that the AFC setting will have any affect on your fuel mileage. It only deals with fuel delivery before boost comes up.

 

[Rams-n-Hogs]

The only thing I ever noticed by adjusting the star wheel back was a little more turbo lag, and a little less smoke. If it does affect mileage, it isn't noticeable.



Jim

 

[JGheen]

Yeah, that was my thought on the mileage being it is only pre-boost fuel and doesn't have a big effect on cruising fuel delivery @ like 10 lbs. of boost.

I can also understand the lag of the turbo due to the decreased fuel before boost builds, being that the more fuel burned is more energy top turn the compressor wheel. But on that note, is there ever too much pre-boost fuel, for example if one were to remove the AFC springs or just turn the wheel as far as it will go for maximum pre-boost fueling?? I am not going to do that but I thought I would ask just for the knowledge of what happens. I would think the EGTs would climb extremely fast due to the massive fueling before boost, from what I have heard before.

 

[Joe G.]

The star wheel is a fine tune adjustment. The coarse adjustment is moveing the housing in the screw slots. If the AFC is completely disabled the truck will smoke like a forest fire when you get on it.

 

[JGheen]

Originally posted by Joe G.

The star wheel is a fine tune adjustment. The coarse adjustment is moveing the housing in the screw slots. If the AFC is completely disabled the truck will smoke like a forest fire when you get on it.

Thats what I heard about gutting the AFC... ... too much smoke for me, and I'm sure the EGTs aren't very pretty also. I was under the impression that the more coarse adjustment was adjusting the fuel plate and the position of the AFC housing would determine amount of maximum rack travel for the governor lever.

 

[Joe G.]

The AFC and fuel plate (aka: full load throttle stop) are both throttle stops. The AFC is out of the action after boost comes up. The fuel plate takes over as the throttle stop after that. Positioning the AFC house sets up AFC throttle stop starting position.

 

[JGheen]

Ok, I see, that cleared up a few things. So, would you agree it is best to have the housing bolted down full forward so that you get as much pre-boost fueling as possible to aid in quicker turbo spooling?? I think that is correct... ...

 

[Joe G.]

That's the way I have mine. However, mine is a one truck smog alert if I stand on it from a stop.

 

[JGheen]

I'll second that, so does mine. Once the clutch is engaged and I stomp on the go pedal, it smokes pretty good, ******* the people behind me off as well. Hopefully none of them are environmentalists that have a good memory for remembering license plates..... But then again with all my smoke I doubt they could get a good look at it.

 

[Cooker]

Originally posted by JGheen

So, would you agree it is best to have the housing bolted down full forward so that you get as much pre-boost fueling as possible to aid in quicker turbo spooling??

FWIW - TST Installation instructions recommend to install the AFC housing full forward. I recommend full forward for maximum fueling.

 

[Howard Durand]

The AFC will affect the fuel economy to some extent if most of your driving is short trips.

It is worth it though, I like the way it gets going.



When the AFC was in stock position there was quite a lag between throttle application and vehicle movement.

 

[Texas Diesel]

Originally posted by Joe G.

... mine is a one truck smog alert if I stand on it from a stop...

:-laf