Engine/Transmission (1994 - 1998) Preboost Screw Adjustment

[Dave Remillard]

I'm pretty certain I need to adjust my pre-boost a little. I know with the #4 plate,(see sig) smoke will happen, but if I can get the boost up a little quicker, maybe I won't see the middle finger salute from folks just coming out of the cloud. . What is the process to adjust the screw, and how much at a time? Thanks

 

[rjones]

If you dont like the smoke so much you should back the star wheel off a little to where your happy with the smoke and the power... ... ... ... ... Rick

 

[Dave Remillard]

Thanks Rick, but I have backed it off some. Didn't want to go to far and start losing some power. I'm not certain, but I thought that the pre-boost screw could help with a little earlier spool up. Please someone correct me if I'm mistaken.

 

[bighammer]

What's the pre-boost screw? (haven't heard of that one)

 

[rjones]

Originally posted by no-strokin

Thanks Rick, but I have backed it off some. Didn't want to go to far and start losing some power. I'm not certain, but I thought that the pre-boost screw could help with a little earlier spool up. Please someone correct me if I'm mistaken.

I does but you will get more smoke at take off until the turbo spools,atleast mine does I have mine turned in 3 turns per Piers advice.

 

[rjones]

Originally posted by bighammer

What's the pre-boost screw? (haven't heard of that one)

Theres a screw on the back of the AFC housing that regulates how much pre spool up fuel the engine gets. If you do a search theres other threads that will explain better... ... ... ... Rick

 

[JohnE]

Piers told me a little secret on setting your AFC. DON'T slide it all the way forward. Only go ¾ or a little more forward. That will give you much better fuel (smoke) control in low boost. Of course, an AFC spring kit from him will give you full fueling once you're boosted.



I haven't adjusted the pre-boost setting after installing the #4 plate, in the conservative rear position. Only did the AFC setting per Piers, defeated the wastegate, and a few clicks on the wheel (no spring kit, yet).

I get very little smoke on a normal takeoff. I get a small grey cloud when nailing it at most any rpm and low boost, but it clears quick as the boost hits.



diesel on

-John

 

[Dave Remillard]

Thanks for all the replies as it has helped alot. I'm still a little fuzzy on one thing however. I've done a search first to see if I could find the answer, but no luck. If I understand correctly, by plugging, blocking, etc. the wastegate, I will have more boost at take off. If this is correct, what is the best way to defeat the wastegate, and is there a problem leaving it that way all the time. I did read that a shut off valve can be installed to go from defeated to normal operation of the wastegate. Is this the recommended way to go? It seems that having more boost at the low end should help with more power and less smoke. If I'm wrong here, someone please tune me up. Thanks

 

[Lightman]

Pluging the waste gate will not do anthing for low end bost it takes more fuel=more exust flow to turn the turbo. pluging the waste gate helps on top end bost, but to much bost with out fuel is a waist.

 

[JohnE]

<blockquote><em>no-strokin asked:

<b>&quot;I did read that a shut off valve can be installed to go from defeated to normal operation of the wastegate. Is this the recommended way to go? &quot; </b> </em></blockquote>



Dave;

You have that confused with the valet switch. The valet switch is an on-off solenoid valve that goes in the AFC boost sense line. If the AFC doesn't have a boost signal it will not allow the governor lever forward which limits fueling. Then the valet parking attendant doen't play with temptation.



I sent you an email to better explain the AFC actions.



diesel on

-John