Diesel Dynamics Fuel Pin Update

[jbolt]

I pulled my pin after 1000 miles of use and I'm a dissapointed to find out the pin is not hardened. After only 1k miles there is enough significant wear that I will not put it back in.



See picture below

 

[Old Smoky]

 

[Philip]

Well that isn't good.



I used mine for around 10 miles them pulled it back out. I didn't see any difference in off idle power. The egt's were up 25 at mid range. The egt's were down 25 on WOT.



I put my stock pin back in. I set it for max fuel. I also shaved the washer a little to. I removed around . 020 off the waher.



But I'll hang on to this pin. Now I have one to grind on and play with.

 

[BushWakr - RIP]

I wonder if tempering never entered their mind, and the resulting wear, or... . maybe the overall shape/contour is the same all the way around because you'd have to keep turning it,,, either way, that's not cool at all.

I would consider tempering it prior to install. You can achieve a decent temper using home tools and an oil bath.



Bob.

 

[jbolt]

Originally posted by Philip



I put my stock pin back in. I set it for max fuel. I also shaved the washer a little to. I removed around . 020 off the waher.

When I had my AFC apart today I took some measurements. WIth the nylon washer removed the pin cannot travel far enough to have the shoulder strike the guide pin. When the pin is bottomed out the gap between the pin bore top edge and the bottom of the diaphramn is . 060"



Jay

 

[Wayno]

Hey jbolt , so what you are saying is that you can take the nylon washer off the stock pin and put it back in and it will work fine ?????????

 

[BushWakr - RIP]

Wayno, it is usually safe to remove at least 1/2 of the washer thickness. Some have removed even more, with the resulting smoke and EGT's. I believe even nascar mark ran WITH a washer that was tweaked a bit...



Bob.

 

[jbolt]

Let me be more specific

Wayno- based on the measurements I took on "MY" AFC & pin when the pin is bottomed out without the nylon washer there is a clearence of . 005" to the upper egde of the guide pin. Manufacturing tolerences may differ so your clearence may be more or less.



My nylon washer is . 144" thick. When the pin is bottomed out the gap where the nylon washer would be is . 060" so if you shaved the washer to under . 060" you might as well take it out if your pin will clear. Bobs advice on not going less than 1/2 the thinkness is probably sound as it would give you a . 010" - . 015" safety margin just in case.





FWIW- with the fuel screw to the stop collar the max guide pin throw at WOT on y AFC is . 194" My stock eccentric pin set to the max side will allow . 184" of guide pin travel. I haven't checked to see if adjusting the fuel screw in will change the guide pin travel yet.



Jay

 

[BushWakr - RIP]

I believe that the full fuel screw cannot impact on the components you mention ... . it will provide more fuel in general, which in turn will bring on more boost and boost quicker to some degree... but it cannot impact how far the AFC cone travels, or the depth the fuel pin travels since they have physical limitations based on washer thickness, min. throat diameter on the AFC cone's upper edge/shoulder.

Also, I do have a tendency to try and stay a bit on the safe side of the "line" so to speak... well... mostly



Bob.

 

[Case500D]

I got my pin in too

I put my pin in on Saturday. I think the throttle response is much better in the mid range, but up to 5 lbs of boost it is a dog. Max boost is down a pound. EGT are the same and I am unsure on the milage. I am kind of annoyed that the pin isn't hardened. I think I am going to put the stock pin back in with the DD spring for now. But sometime I want to file a bit on the pin and increase the low end boost and then get the pin hardened. Well there went $86 that would have been better off saved. Oh well, live and learn.



BTW, Bob, I was unable to find a good way to measure the DD spring. Once I do get it done, I will let you know. Jbolt has posted the best pin dimensions. My attempts were pretty sad. His CAD drawing is great!



Jeremy

 

[jbolt]

Originally posted by BushWakr

I believe that the full fuel screw cannot impact on the components you mention ... . it will provide more fuel in general, which in turn will bring on more boost and boost quicker to some degree... but it cannot impact how far the AFC cone travels, or the depth the fuel pin travels since they have physical limitations based on washer thickness, min. throat diameter on the AFC cone's upper edge/shoulder.

Bob.

Bob- I am referring to the guide pin travel, item #4 on page 37 of the Bosch manual. I don't know if manipulating the full load screw will effect the guide pins potential maximum travel since it moves the whole governor assembly.



Jeremy- How were you going to measure the spring rate? I'm planning on using the top half of the AFC (cap & diaphragm) and making a simple mock-up of the lower half. Then apply regulated air pressure and measure the pin travel with a dial indicator.





Jay

 

[Case500D]

Jay,



I was going to use a tool like they use to measure valve springs. It measures the pressure and the height of the spring at the same time. But it seems like everyone just replaces their valve springs anymore. I am sure I can find one somewhere.



Jeremy

 

[JLEONARD]

If you are going to heat treat, (or harden) the pin you should find out what material it was made from. Otherwise you will only be guessing.

Diesel Dynamics should be able to tell to that info.

An alternative may be chrome plating it make the surface hard.

If you find out the material I can suggest how to heat treat it... I work with a metallurgist that is really practical.

Jay

 

[BushWakr - RIP]

Jay,



Item 3 on the same page is the one that places physical limitations on the guide pin travel. I would think that regardless of the fueling settings, that thing can only travel so far based on the reverse lever dimensions and the opposing cast/metal part.

I do wonder how far past the narrowest part of the cone neck the pin will travel, and if at that max point there is any degredation of efficiency.

Is the the throat of the cone that size for strenght reasons?? for pin limitation/efficiency reasons?? etc.





JLeonard,



I wonder if there is a 'general' process for tempering the more "common" metal(s) that would be used in making things like the cone. For example, I'm wondering if mild steel was used, and if so, is there a 'basic' tempering process that will accomodate mild steel and whatever is slightly above/below this material.

I'm pretty surprised that "tool steel" wasn't used for this item though, or at least something with a decent Rockwell rating to minimize wear. On the up side, I'd much rather wear the cone than the guide pin. I think I'd rather repalce the cone assembly than pull the pump apart just to get at that pin. .



Bob.

 

[JLEONARD]

Bob,

"Tempering" is a metallurgical term usually used to describe a process that reduces hardness.

Reducing hardness usually increases metal "toughness".

Toughness is not needed here... there is no "shock" involved.

What we need is surface hardness.

We probably want a cone that is in the RC 20 to 45 range... . or a very shallow case hardness depth.

My guess by looking at the tapered pin that Jbolt had is that the material is dead soft... . bump it up a few "notches" and the pin will last forever. But knowing the material used will make that easy.

Jay