Fuel Delivery Rate Pin: Where Is Yours at?

[R.E. Miller]

Hey guys,

I was just wondering for those who have played around with the pin, where do you run your truck? I just changed mine over to the most aggressive profile, and kind of like it, but my truck will actually make boost unloaded I don't understand why it is doing this, and was just looking for some input.

Thanks,

Russell

 

[formula]

Russell,



The adjustment you're talking about is actually the Aneroid Fuel Control (AFC) eccentric. This eccentric controls the travel of the fuel delivery rate pin which in turn controls how much fuel you get at a particular boost level. (just to clarify). I also have my AFC eccentric set at the most aggressive profile. The smoke screw is backed way out and the star wheel has been turned clockwise about 1 turn. These adjustments make for great throttle response without lots of part throttle smoke. As for making boost while free-reving, I'll make about 4psi at 3100rpm. I don't think there is any problem with this. Seems to be due to the smaller housing and the engine blowing lots of air at that speed which causes the turbo to make a little bit of boost.



Sean

 

[Old Smoky]

I hope you would be making boost unloaded with your 12cm2 exhaust housing. I am assuming you mean while cruising, steady throttle. I see about 2-3psi cruising @ 55-60 mph with 16cm2 housing.



You are making more boost because when you turn the eccentric pin, you allow the pump to flow more fuel. This increases fueling earlier, and overall. You should notice more smoke, and higher peak boost. If you feel you have too much smoke, you can tune some of it out by adjusting your star wheel. But, this will slightly hurt the responsiveness, but not overall fueling.



Oh, mine is set to “max. ”



Mike

 

[Old Smoky]

Well, I see you beat me to it Formula. Maybe if I hadn't stopped for a potty break I would have beaten you. Oh, well.



Mike

 

[formula]

hehe..... I was hoping to get Philip for the air filter thread...

I'll take my potty break now



SP

 

[Philip]

You got me on this one formula. I had company show up.



I see 3-4 PSI boost at 60 mph with an 18cm housing.



I have no idea where any of my settings are.

 

[R.E. Miller]

Thanks guys! Actually, the boost I am talking about is seen while reving my engine, this makes me wonder, I thought that this is not suppose to happen. Something else might be up with my injection pump, I might have it gone through when I take it off to replace my tappet cover gasket. My milage has been off, but serious, I have no smoke Reason for no somke is most likely the radical star wheel setting I am running of two full turns tighter (I forgot which way that was CW or CCW?) I am afraid to loosen the spring tension on the star wheel in light of watching more milage slip. I don't know, more tinkering is in order. BTW, my max fuel screw is about 1. 75 turns in. Oh yeah, sorry brain is slow, my egt's seem to "hover". What I mean is they do not shoot up and fall off real quick, they seem to go up quick under fuel, but when I let off, they drop slow???



Food for thought

Thanks,

Russell

 

[BushWakr - RIP]

R. E.



If you see some boost surge when you pull RPM in "N" that is normal. It takes a few seconds to have it build but it will. Maybe a valve check is in order, when was that done last?



Your full fuel screw sends fuel to the entire RPM band with a larger portion of the 'increase' being directed towards low-mid range. This can often cause some smoking. In the older posts, mostly in the "archives" it was noted that some pumps just do not respond as much as others to the full fuel screw adjustment.

The starwheel, if adjusted CCW will result in more boost being needed to trigger fueling. The AFC spring holds the "cone" from dropping until you get that boost needed to overcome the spring tension.

A good baseline with a stock pump is to set your AFC diaphram to max, then smoke screw to "neutral", starwheel down 1 turn and drive. You can tweak the full fuel screw as needed, and the starwheel as needed for low boost smoke.

Watch your temps at all times...

Bob.

 

[JLEONARD]

While formula was in between potty breaks this weekend he helped me make some adjustments to my pump.

We rotated the eccentric 90 deg clockwise, turned the starwheel

1/2 rev clockwise, and decided to leave the power screw alone because it looked as if it only had 3/4 turn left.

What a difference! Max boost is up 1 1/2 psi to 26, but also comes in faster and at much lower rpm. I can a really feel the truck pull now. . bye,bye turbo lag.

I get a little smoke when my foot is on the firewall between 1000 and 1500 rpm, then it prety much disappears.

EGT rises faster, but has not really changed much.

Traction is now an issue at times.



I will try the neutral rev and see if I get any boost.

 

[formula]

Originally posted by R. E. Miller

Thanks guys! Actually, the boost I am talking about is seen while reving my engine, this makes me wonder, I thought that this is not suppose to happen. Something else might be up with my injection pump, I might have it gone through when I take it off to replace my tappet cover gasket. My milage has been off, but serious, I have no smoke Reason for no somke is most likely the radical star wheel setting I am running of two full turns tighter (I forgot which way that was CW or CCW?) I am afraid to loosen the spring tension on the star wheel in light of watching more milage slip. I don't know, more tinkering is in order. BTW, my max fuel screw is about 1. 75 turns in. Oh yeah, sorry brain is slow, my egt's seem to "hover". What I mean is they do not shoot up and fall off real quick, they seem to go up quick under fuel, but when I let off, they drop slow???



Food for thought

Thanks,

Russell

Russell,

What kind of mileage reduction are you seeing? A little bit of reduction, 1mpg or so, doesn't seem much of a reason for concern. This always happens to me in the winter months when the diesel mix gets changed. Make sure you check/change your air and fuel filters. What is your EGT running? As far as the EGT taking a while to come back down... ... . does this happen if you romp on it real good and then push in the clutch while slowing down? If so, that's because the engine isn't pushing much air at low rpm and will take longer to cool off. The no smoke is most likely related to the increased AFC spring tension because you're going to need more boost to get full fuel, but by that point you've already got the boost to burn the fuel cleanly. This will also decrease your throttle response and make you have to get on the throttle more to accelerate. You might want to try and set the star wheel back down 2 turns to start and see what happens.



SP

 

[JLEONARD]

5 psi boost in neutral at about 2000 rpm, engine not totally warmed up (maybe 140* F)

 

[R.E. Miller]

Thanks a lot guys!

Really, I appreciate the insight here. The milage issue is really a different story, but might be related too. I mean that the mileage fell off before I modified the turbo and fuel. I went from seeing consistent 16-18mpg towing and around town with a best long trip mileage of 23mpg, to now a consistent 15-16mpg all of the time. I might try setting the star wheel back down and just check what happens



Thanks again, and the profile I have it on now rocks



Russell