12 Valve Engine and Drivetrain Talk about the 12V engine and drivetrain here. This is for 1994-1998.5 engine and drivetrain discussion only.

AFC springs

Thread Tools
 
Search this Thread
 
Old 06-06-2006 | 09:15 AM
  #1  
y22man's Avatar
Thread Starter
Registered User
 
Joined: Apr 2004
Posts: 169
Likes: 0
From: Utah
AFC springs

Well looks like my tranny is toast. I am going to replace it with a DTT. So time for the power mods. I am going with 3GSK and a #10 plate.

My question is, should I install the AFC springs too? I don't know anything about them besides it helps with smoke on the 215 pump.
Old 06-06-2006 | 09:33 AM
  #2  
displacedtexan's Avatar
Banned
 
Joined: Apr 2005
Posts: 3,337
Likes: 0
From: Place with no quail:(
They are supposed to help reduce smoke... But I don't know of anyone that has them. It is usually possible to get acceptable smoke without replacing the spring by just playing with the settings of plate/AFC/Starwheel and get it all balanced out. Which in my opinion is half the fun of a 12v.
Old 06-06-2006 | 09:47 AM
  #3  
Jetpilot's Avatar
Registered User
 
Joined: Apr 2002
Posts: 1,250
Likes: 0
From: Hershey, PA
The springs are a nice addition for lowend fueling. The cost is very reasonable and an easy install.

Doug Smith
Old 06-06-2006 | 10:13 AM
  #4  
displacedtexan's Avatar
Banned
 
Joined: Apr 2005
Posts: 3,337
Likes: 0
From: Place with no quail:(
Originally Posted by Jetpilot
The cost is very reasonable and an easy install.
I have thought about getting them for those two reasons... Just to see how well they work.
Old 06-06-2006 | 11:09 AM
  #5  
y22man's Avatar
Thread Starter
Registered User
 
Joined: Apr 2004
Posts: 169
Likes: 0
From: Utah
Ok, thanks for the replys guys. I always like more low end. So I will pick them up and see how they work.
Old 06-06-2006 | 11:20 AM
  #6  
vssman's Avatar
Registered User
 
Joined: Jan 2002
Posts: 445
Likes: 0
From: Naugatuck, CT
I have a set installed and they did both lower smoke and give me more low end snap. I can still blot out the sun if needed...
Old 06-06-2006 | 11:54 AM
  #7  
Lil Dog's Avatar
Chapter President
 
Joined: Feb 2002
Posts: 6,102
Likes: 2
From: Red Deer, Alberta Canada
The main benefit is the ability to more finitely adjust the AFC on the 215 pumps. The springs in these pumps are like train-car springs and one click is either on or off. Now its more of an easy adjustment. As with vssman, the sun can be blocked if need be.
Old 06-06-2006 | 12:50 PM
  #8  
y22man's Avatar
Thread Starter
Registered User
 
Joined: Apr 2004
Posts: 169
Likes: 0
From: Utah
ok with that said, Since I have a smaller pump. '95 auto, twill the AFC springs benifit me then?
Old 06-07-2006 | 11:37 AM
  #9  
vssman's Avatar
Registered User
 
Joined: Jan 2002
Posts: 445
Likes: 0
From: Naugatuck, CT
I found that when I turned up the pump I would have heavy smoke when just after starting out from a stop. To compensate, I turned the star wheel to minimize the smoke but it had to go back so much that I wound up with L-A-G. The spring kit is a softer but longer spring that eliminates the excessive lag but yet helps control the smoke. There's three main adjustments the AFC gives you:
1) Position - this is more of a gross adjustment. Move the AFC forward and the governor arm will move forward an equal amount regardless of spring adustment.
2) Star Wheel adjustment - Turbo boost pressure has to overcome the spring pressure to move the AFC lever out of the way. The stock spring is short and stiff. It will take a lot of boost to move it. The pump won't build boost as quickly because the lever is in the way holding the governor arm back. The AFC spring is lighter and longer. Thus it puts the governor arm back in the "stock" location with the AFC slid forward and yet moves with lower boost.
3) Pre boost screw - This is the screw that is the rear stop for the AFC lever or how far back it'll go.

Hope this helps.
Old 06-07-2006 | 08:06 PM
  #10  
Fueling around's Avatar
Registered User
 
Joined: Mar 2003
Posts: 1,629
Likes: 0
From: Northwest, Minnesota USA
vssman gave a great description of the often forgotten part of a 12 valve, AFC tuning.
Here's more to the story of 12 valve tuning.
If you want 3k GSK then advanced timing is really necessary to prevent popping at higher rpm.
The drawback to advanced timing is the low end lag. Low end lag is further worsened if you don't adjust the governor lever to drop into full fueling around 2,000 rpm.

I've got lots of timing advance, gsk, #4 plate with governor lever pretty good, AFC slid forward, star wheel forward & soft spring.

I would like a bit more smoke to reward those pesky tailgaters that ride my bumper when I haul the camper. I actually out accelerate most vehicles even when hauling the camper, but only run at speed limit. I guess that annoys them?
Old 06-08-2006 | 09:08 AM
  #11  
y22man's Avatar
Thread Starter
Registered User
 
Joined: Apr 2004
Posts: 169
Likes: 0
From: Utah
Thank you guys very much for this discussion.

In my 5 years of surfing TDR and DTR I have not read a thread about the AFC settings. And that could be me just blowing over the posts. I searched on AFC and I could not find anything like this.

Thank you again. If there are any other insights lets hear them.
Old 06-08-2006 | 11:54 AM
  #12  
TxDiesel007's Avatar
Registered User
 
Joined: Dec 2004
Posts: 3,411
Likes: 1
From: Laredo
Originally Posted by Fueling around
vssman gave a great description of the often forgotten part of a 12 valve, AFC tuning.
Here's more to the story of 12 valve tuning.
If you want 3k GSK then advanced timing is really necessary to prevent popping at higher rpm.
The drawback to advanced timing is the low end lag. Low end lag is further worsened if you don't adjust the governor lever to drop into full fueling around 2,000 rpm.

I've got lots of timing advance, gsk, #4 plate with governor lever pretty good, AFC slid forward, star wheel forward & soft spring.

I would like a bit more smoke to reward those pesky tailgaters that ride my bumper when I haul the camper. I actually out accelerate most vehicles even when hauling the camper, but only run at speed limit. I guess that annoys them?
Man that to me is the fun part of the 12V

Now here is a question i have, what is that screw behind the AFC? is that the smoke screw? what is its purpose? i have yet to tamper with that. Bein that i have enough smoke, i dont have a spring kit, but orderin it along with the overflow valve wouldnt be a bad idea....

Any ideas guys?

Rick
Old 06-08-2006 | 12:29 PM
  #13  
Lil Dog's Avatar
Chapter President
 
Joined: Feb 2002
Posts: 6,102
Likes: 2
From: Red Deer, Alberta Canada
The screw on the back of the AFC housing is also very important. Especially when you slide the AFC housing forward. That screw is the zero stop for the AFC cam when the pump is at "0" boost. So when you slide your AFC housing ahead, you would like to loosen that screw back (or at least I do) to reduce the off idle smoke you get on takeoff. I had it totally backed out for a while, but then found the lag from the stop to get going was a little big. So I have started screwing it in, I think I am in about 3 turns from totally backed off.

When you do the AFC spring upgrade the instructions say to adjust that zero stop to all the way out. When you just slide the AFC ahead you should notice that the smoke(fuel) off the line is pretty strong.

The balance of off the line fuel and then fuel rate vs. boost is all in the seat of the pants and the soot out the pipe. Of course its up to the user as to that balance. That is something you can not do with any electronic box!!!!! I love my 12V!!!
Old 06-08-2006 | 01:13 PM
  #14  
signature600's Avatar
Registered User
 
Joined: Aug 2003
Posts: 3,604
Likes: 0
From: Jeffersonville, Ohio
WOW!!! Really good discussion guys!!

Keep the tips coming
Chris
Old 06-08-2006 | 02:31 PM
  #15  
robert chilton's Avatar
Registered User
 
Joined: Aug 2004
Posts: 845
Likes: 0
From: Va Beach
Are ya'll talking about the set screw above the one used to adjust the gov arm? I have a cloud that I need to adjust out the happens at low RPM. Usually see it when the RPM is low going around a corner at 30 MPH in 4th.


Quick Reply: AFC springs



All times are GMT -5. The time now is 04:31 PM.