Monty- you’ve outdone yourself. Many thanks for your effort. It is GREATLY appreciated.<br><br>If I may continue. Taking your brilliant description of the fueling governor how does the AFC tie in? <br><br>Ultimately where I’m going with this is a better understanding of cause and effect from “tweaking” the pump and the pumps limitation.<br><br>Example 1: I have been told that turning up the full power screw effects the lower to middle throttle range more than the top end. Why?<br><br>Example 2: My stock AFC was set up for an engine to make 160 hp @ 2500rpm, max boost somewhere between 13-15 psi, timing around 1.25mm, stock injectors &amp; turbo. From the wear markings on my eccentric pin (factory set at about 20%)I know it has used the full amount of travel at the stock boost levels. With the Lucas injectors, timed at 1.35mm I was making 26psi. I recently set the eccentric to 70%, timed to 1.5mm and I’m only making 22psi but with more power.<br><br>Jay<br><br><br>

 

I sent this in an e-mail to a fellow who was looking at modifying his AFC. It refers to the pictures from the Bosch VE manual (which can be purchased on-line as a .pdf document from SAE for ~$15). I am guessing from the discussion on this thread that you all might find it interesting, despite its length.<br><br>. . . but I will re-hash my analysis of the pump operation here. (The figures in the manual on pages 22 (Fig. 1)and 37 (Fig. 7) will be helpful for the following discussion).<br><br>There are two adjustments that control the maximum fuel delivered by the pump. The first is the &quot;Full-load adjusting screw&quot; (Fig 7 # 10). It can also be seen in the upper right on Fig. 1 pg. 22. As far as I can tell, it rotates a static lever (fig 7 #11) around a fixed fulcrum. The top of the lever rides on the adjusting screw and the bottom has the fulcrum for the <br>&quot;tensioning lever&quot; (Fig. 7 # 12, but more plainly visible in fig 1).<br>Adjusting the &quot;power screw&quot; moves the fulcrum for the tensioning lever back and forth, and the position of the tensioning lever controls the slip collar on the piston, which controls when the piston spill ports open (ending fuel delivery for that stroke). Turning the screw in moves the tensioning lever fulcrum to the right (as pictured), and thus the slip collar to the right. This is why over-adjustment of the full-load screw results in high idle, and eventually erratic governor operation. The second adjustment is through the AFC. The AFC assembly controls the &quot;Reverse lever&quot; (Fig 7 #3) which acts as an adjustable stop for the travel of the &quot;tensioning lever&quot;. (the following references are to fig. 7) As pressure increases on #14 #8 moves down, letting #4 slide to the right, #3 rotate clockwise, and # 12, the tensioning lever, move further to the left (as pictured).<br><br>By changing the orientation of the &quot;Sliding pin's&quot; &quot;control cone&quot; you can change how far out into the AFC bore the &quot;guide pin&quot; extends, and thus the stop position for the tensioning lever. The further out the &quot;guide pin&quot; is allowed to extend into the bore, the more fuel you get. On my pump, I observed that with the &quot;sliding pin&quot; removed, the &quot;guide pin&quot;<br>would extend out farther into the bore than even the narrowest part of the sliding pin would allow, and that the pump would operate properly with the guide pin extended this far. Running the pump with the &quot;control cone&quot; set in the maximum fuel position, I find that I produce too much smoke at manifold pressures under about 3psi.<br><br>So, ideally I would have a &quot;control cone&quot; with a taper that started from no detent, and continued to a detent that was as deep as the guide pin will extend (with the sliding pin out, and the accelerator floored -- can be measured with motor not running).<br><br>I am not sure how much manifold pressure is required to cleanly burn all of the fuel delivered by a fully extended guide pin, but I would guess that it is at least around 10 psi. I know that once I get about 3psi of manifold pressure my smoke goes away. This makes me think that the AFC needs to<br>operate over a wider pressure range. The amount of travel possible for the sliding pin is limited by the flexibility of the diaphragm and the design of the AFC housing. So we can't<br>just make the pin slide further. However, if we had a steeper angle on the control cone, and a stiffer spring, then a specific pressure would result in less movement of the sliding pin, but the same movement of the &quot;guide pin&quot;, and the same fuel delivery for that pressure. Overall, it would allow for a<br>wider pressure range to have an effect on fuel delivery, with the same travel of the &quot;sliding pin&quot;.<br><br>I measured the spring constant of my spring, using a ruler and a scale. I cannot remember what I figured it to be, however, I remember deciding that the maximum travel of the sliding pin took place over a change in pressure of about 6psi, and that about .125&quot; preload would give me a starting point of about 2-3psi. so my max fuel would come in around 8-9psi. So -- my idea was to measure the maximum extension of the &quot;guide pin&quot; and the maximum travel I could get out of the &quot;sliding pin&quot; then cut a notch in a new piece of stock that was linear and ran from the outside edge of the stock to the depth that equal the &quot;guide pin's&quot; maximum extension. The notch would also have to be in the right place, obviously, and I thought<br>that using two nuts (one on each side of the diaphragm) might allow for fine adjustment. Then I thought that I could jam little rubber blocks into the stock spring, starting at the ends, until it was stiff enough so that maximum fuel would only be delivered with sufficiently high manifold pressure (that pressure to be determined by trial and error). <br>

 

[quote author=Bushy link=board=9;threadid=9951;start=0#95442 date=1043309687]<br>As I recall a similar conversation with Piers on this topic, he felt that the work/trouble to do the spring kit idea was more than it was worth. He felt that using the high idle method was pretty much, just a effective, and a 5 minute job in comparison. I have done the latter method, and now pull right up to 3000 RPM no problem.<br><br>What do you mean by the high idle method? I need to run at least 3000 rpm do to low gearing. What is the best way to achive this goal?<br><br>Thanks Neil<br>[/quote]

 

Neil,

You can increase the top end RPM by using what is called the
&quot;high idle screw&quot;.
It is located on the fender side of the pump, just under the domed AFC housing. It will have a stubborn tamper cap on it (if it has not been touched yet) that you need to remove.

I'd cycle the throttle open/closed a few times and watch the throttle lever motion. You'll see that at rest, one end will have a stop plate that contacts the normal idle screw end. At WOT the opposite (high idle) screw will be contacted by a stop plate on the throttle. It MUST make contact with the high idle screw when at WOT. If not, you won't get full RPM's.

Once the tamper cover is off, you'll see a long screw, just like the normal idle screw. This will have 2 locknuts on it, both are 10mm I believe.
Mark the screw somehow, and loosen both locknuts off. Once they are cracked loose, turn the screw out (counter clockwise when viewed from the firewall end) about 3 turns.
Tighten locknuts and test drive.
You may need to repeat a number of times depending on where it is now, and how sensitive the pump is.
Each test drive can be done in 1st gear WOT. Watch the tach, you'll feel the engine start to &quot;fall off&quot;, then, it will contiue to gain RPM much more slowly till it peaks and will go no further. That is your top end RPM, and the point were it falls off is your defuel point.
Right now, my truck will pull right up to about 2900, and creep to 3000 RPM.
Some do this test in &quot;N&quot; or &quot;P&quot; in the driveway (on auto's) but I personally like to have atleast some load on the engine when I run it up like that. Either way should work.

I've attached a pic to show you the layout. The correct one is labelled &quot;governor screw&quot;.

 

I wanted to say thanks to Monty and asilitch for their controbutions to this thread. <br><br>Great Job guys!

 

;D i have the utmost respect for piers, but i have to disagree with him on the 3000 governor spring. i tried the high idle method first. it would pull to 2900 plus but not very strong above 2650. the 3000 governor spring will make the engine as responsive as a gasser at low rpm and pull like crazy to 3000 plus. i would never go back. it is more than worth the effort to change. just to brag a little if you can believe the new diesel pickup 1/4 mile slips my 13 year old ctd will drive around all 3 brands of show room pickups. ps i cant touch nascar mark period.

 

Jughead,

If I read your post correctly, you're saying that the high idle allows you to pull up to 2950'ish, but that you feel a definite &quot;defueling&quot; prior to that??? Did I get that correct??
That is in contrast to the spring change which shows no sign of defueling until ???? when?? . This spring change has allowed you to have a governed speed of roughly 3000 RPM without 'high idle' adjustment???

BTW, what did the spring cost you, and how long was your install time?
I'm a bit concerned over this particular mod. The reason I say this is because, in recent reading up on the VE, there are some extremely close and interdependent tolerances inside. The cam ring, rollers, piston, idle arm lever, and more are extremely interconnected. Don't take this the wrong way, I probably need to dig a bit more into the workings but it seems that changing one item like that spring can effect other stuff like the governor counter weights and more. Thoughts???


Bob.

 

I have to concurr with Jughead. I have the same experience with the high idle method. I can still feel it defueling at about 2600. Where do I buy the spring?

 

I am like Bob on this one. To me, a higher tensioned spring would make the flyweights extend further out to create a state of balance with the gov. spring and flyweight at high fueling points (WOT etc.) thus, putting more stress on the flyweights and possibly making them run out. I dunno, im on the fence as well with this one.

 

[quote author=Bushy link=board=9;threadid=9951;start=15#98021 date=1043881825]<br>Jughead,<br><br>If I read your post correctly, you're saying that the high idle allows you to pull up to 2950'ish, but that you feel a definite &quot;defueling&quot; prior to that??? Did I get that correct??<br>That is in contrast to the spring change which shows no sign of defueling until ???? when?? . This spring change has allowed you to have a governed speed of roughly 3000 RPM without 'high idle' adjustment???<br>the governor spring made the truck come alive. it pulls to 3000 plus that is where i chicken out. it has been in there a year 10k mi. plus. 12 passes at strip. one missed gear. went to neutral from 2nd. dont know where tach went. dont know enough about pump to know what is happening just know it works great. good bad or ugly i love it.<br>BTW, what did the spring cost you, and how long was your install time?<br>I'm a bit concerned over this particular mod. The reason I say this is because, in recent reading up on the VE, there are some extremely close and interdependent tolerances inside. The cam ring, rollers, piston, idle arm lever, and more are extremely interconnected. Don't take this the wrong way, I probably need to dig a bit more into the workings but it seems that changing one item like that spring can effect other stuff like the governor counter weights and more. Thoughts???<br><br><br>Bob.<br>[/quote]

 

[quote author=Bushy link=board=9;threadid=9951;start=15#98021 date=1043881825]<br>Jughead,<br><br>If I read your post correctly, you're saying that the high idle allows you to pull up to 2950'ish, but that you feel a definite &quot;defueling&quot; prior to that??? Did I get that correct??<br>That is in contrast to the spring change which shows no sign of defueling until ???? when?? . This spring change has allowed you to have a governed speed of roughly 3000 RPM without 'high idle' adjustment???<br>i cant seem to get my posts in the right order. my reply is in the middle of my previous post. on puters on a scale of 1 to 10 i am less than 0. sorry about the mix up. [/quote]

 

Well, the spring vs. high idle method deserves a bit more investigation....
I have had the chance to do some reading, fairly in depth, since Okie's posts on the VE. I didn't realize just how complex and interdependant the internals were on this pump. Simple as it seems, it's not.
Once again, please don't take me wrong here guys... I'm just now coming to get a bare glimmer of a grasp on things like Okie mentioned such as 'state of balance' etc. Other things like RPM Droop.... ok, don't go there...
There are a couple things that I've come across that definitely warrant more investigation for performance reasons...now I just add the spring change to the list....

bob.

 

Changing the spring does not change the range of motion of the governor weights. (Though adjusting the AFC eccentric does).<br><br>For any given speed, there is a specific amount of centripital force required to keep the flyweights from spreading. This force is supplied by the &quot;tensioning spring&quot;. If there is not sufficent resistence in the spring, the weights spread and push the governor rod forward, moving the slip collar to allow less fuel delivery AND pushing the &quot;tensioning lever&quot; against the &quot;tensioning spring&quot; -- if there is not sufficient resistance in the spring, the tensioning lever will hit a stop on its pivot, and no fuel will be delivered by the pump.<br><br>If the spring tension is greater than the force of the rotating weights, then the tensioning lever will move until it hits the stop controlled by the AFC, and maximum fuel will be delivered.<br><br>The only thing that is changed by changing the stiffness of the spring, is the relative engine speed and accelerator positions that define these two events (no fuel and max fuel). No fueling and maximum fueling can happen at any engine speed.<br><br>Changing the spring does nothing but change the speed range over which the maximum governed speed can be set. All of the parts inside the pump move the same amount, etc.<br><br>As far as droop goes: If the system worked perfectly, then letting off on the accelerator a hair would immediately cause fuel delivery to be completely shut off for a moment until the engine slowed down, and vice versa, which would allow absolute full fuel to flow until the engine hit a specified RPM range (equalling a specific spring tension) and then no fuel at higer RPM's. The reality of spring technology and other intentional modifications for drivability, is that the governor tends to cut the fuel off a little bit gradually with increasing RPMs before it cuts it off completely -- spring constants aren't linear, and the range of motion between no fuel and full fuel is material . . .<br><br>That all said, one spec of dirt can be enough to ruin an open pump, which I find to be an important consideration in open pump surgery.

 

This is some great info. With my &quot;defueling point&quot; set at 2950-3000rpm, I can see the boost start to slowly fall off before then. This is consistent with my last dyno sheet that showed my max hp at 2420rpm. It will still pull up to the governor fairly strong, but slows about 2420 rpm when the boost starts to drop. So, I actually start to defuel there, and not at 3000rpm. This isn't as noticeable after the hybrid turbo upgrade. I guess it just masked the condition.<br><br>Mike<br>

 

Another thought - The P7100 has a high idle adjustment, right? If so, why are the GSK's so popular, and not adjusting the high idle screw? <br><br>Mike<br>