Improved Fuel Delivery Rate Pin Design

[Old Smoky]

I have been working on an improved fuel delivery rate pin design. After some modifications to my stock pin, I am working with a local machine shop on a whole new pin. The first one should be done the end of next week. I will do some testing to see if it’s what I want, and make some changes if need be. My current design produces a gain of 6psi boost over the minimum stock pin setting, and increases EGT’s 125* at max boost. I would have compared my results to the stock setting, but that wasn’t possible after it was modified, so I used minimum setting. So far it has been a great success. The new pin will be hardened, and be a quality piece. It shouldn’t be long before have a finished product. I will report back the results.



Mike

 

[Philip]

Sounds good.



Keep us informed.

 

[Old Smoky]

The test vehicle is a '92 with PW injectors, BHAF, 4" exhaust, tuned and timed pump, and 16cm2 exhaust housing. I don’t know if/how results would vary between setups.



Mike

 

[Philip]

If you need a almost stock test rig. PM me. Oo.

 

[Old Smoky]

O. K. Philip.



Mike

 

[hdm48]

And here I thought I was the only one who lays awake at night thinking about this stuff. This is why my race motors win races.

Right on, dude.

But now I gotta know everything. What is the adjustment? How easy is it to do? Can I do it with the pump on the motor?

You know, everything.



-dave-

 

[BushWakr - RIP]

Dave,



You are definitely not the only one who lays awake thinking about this stuff, and I don't think we're alone either...



Now, Old Smoky,



Are you referring to the pin or the cone ??



bob.

 

[formula]

I'm going to make a guess that it's the eccentric (attached to the diaphragm) that is being redesigned. A different profile will create a different fueling curve. A deeper maximum cut will also increase the maximum fueling setting when boost is high enough to push down the diaphragm.



I have a question about this though..... Is there a safe limit to the travel of the "regulator pin" that rides on the eccentric? Could any damage to the pump or the AFC unit result from it extending out too far?



Sean

 

[Old Smoky]

Yep, it's amazing what you can come up with laying awake in bed at night. When I say "pin" I am referring to the shaft and cone beneath the diaphragm in the AFC. I can’t remember the unit’s correct name. The shaft will remain the same, but the cone will be modified. It will actually no longer be a cone, but a "notch" or “cut” on the shaft. I will post pics when it is complete.



Once I have a finished product, the modification will be quite easy, and can be done with the pump on the engine. What will need to be done is to remove the TPS (automatics only), remove AFC cover, lift out diaphragm and the "pin" will come with it, remove rubber diaphragm and washers, reinstall on new unit with punch mark facing the same direction as the "notch", lubricate, and reassemble everything with the punch mark facing the front of the vehicle. It only takes me about 7min or so to do this.



I have been running the modified “pin” on my rig for a few months now. As with any fueling enhancement, EGT’s, smoke, and mileage depends on your right foot. I haven’t noticed a change in mileage. EGT’s will obviously rise faster with your foot to the floor, but not so much that it has been a concern to me. Smoke can be tuned by increasing spring tension with the star wheel, and/or backing out the smoke screw.



Mike

 

[Old Smoky]

Formula,

Good question. I HAVE driven a couple hundred miles WITHOUT the eccentric pin in the AFC (for testing purposes). The "regulator pin" as you call it, has a stop so it cannot extend too far. This needs to be pushed back in with a small regular screwdriver before the eccentric can be reinstalled if driven without.

 

[formula]

Mike,

Thanks for the clarification. What were the effects of running with the AFC disabled ?



Sean

 

[Lil' Dog]

Originally posted by formula

Mike,

Thanks for the clarification. What were the effects of running with the AFC disabled ?



Sean

Too much fuel and not enough air... SMOKE and high EGT's.



I reduced some of the mid range EGT rise by upping the spring pressure from what I was at. Same power but less smoke and lower EGT.



The one trick to also use is the shaving of the nylon stop washer on the pin. . Makes a little more travel on the deep part of the cone.



Interested in the results on this. .





J-eh

 

[Old Smoky]

I agree with Lil' Dog. Disabling the AFC will increase smoke and EGT's, defiantly on the low end. But for the most part it can be driven so that it won’t smoke any more than normal. Your right foot becomes the AFC. When the engine has enough rpm and boost, such as driving down the highway, acceleration is greatly improved. My boost gauge jumps to 33psi instead of slowly climbing. I wouldn’t, however, recommend running with the AFC disabled.



Shaving the nylon stop to get more travel does work. Just don’t go too far, or leave it out. There will be too much travel for what the pin is designed for, and you will loose power. It can actually be seen on the boost gauge. Boost rises to say 25psi, then drops to 23 or 24. This is how you can tell if you go to far.



Mike

 

[BushWakr - RIP]

I can't/won't confirm this but, I'm certain this has been worked on before.

The cone, which has a linear shape vertically, is modified so that it resembles something like a fuel plate in the newer trucks which has variable contour as opposed to a straight line up/down for the fueling pin.



The pin will travel out of its hole only as far as the shallowest part of the cone, up near its "neck" at the top of the cone proper.



There's more to this but I think that covers the basics.



Were are you getting and/or buying a new one to modify? How much are they?

Are you using "used" ones for this trial?



Bob.

 

[Lil' Dog]

As Ol' Smokey said you have to be careful shaving the nylon washer. I measured the depth of the pin travel on the cone and then how much I wanted it to go further up the pin. Then shaved the washer on emery cloth to get the required dimension. I only cut about . 020 off the washer and gained maybe about 1PSi. Not a big increase.



Like he said if you over cut the washer you will run too far down and the pin begins to have a taper the other direction near the top of the cone. This is where you would see the boost drop off.





Good point Smokey. .





J-eh

 

[Old Smoky]

BushWakr,

I wouldn't be surprised if this has been done before. These rigs are getting old enough that most of the tricks have been discovered.



As for what I am using right now, the "stock" piece. It took me a few days to build up the courage to fire up Mr. Dremmel(sp) tool. Especially since this is the innards of an expensive pump. I spent some time with a micrometer measuring depth, distance, etc. before starting. There isn't a real good grinding or cut off attachment to do this. It takes some time, and trial and error. The material is very hard, so getting it smooth after grinding also takes a while. Once the grinding and smoothing is complete, there is little material left attaching the eccentric to the rest of the shaft. That is why I designed a piece to be built from scratch.



I thought about buying a stock unit to modify, but Bosch parts aren’t cheap. Besides, the strength is compromised once altered. The new piece will start as round stock, be machined, and then hardened. It will be just like the stock piece, having a threaded stud in the top for the diaphragm and washers, and slots on the sides for a wrench.



One other thing to add... If you try shaving the nylon washer, and get it too thin, they aren't too hard to come by. That way you can experiment some to get the best size.



Mike

 

[Old Smoky]

Well, here it is:



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I forgot to install the stud in the top before taking pictures. I haven’t tested it yet, but it looks pretty close. I probably wont have the results until next week because I got a little excited with my hybrid turbo yesterday. I wasn't sure how much time I would have to work on it next week when the rest of the parts will be in. So I started disassembly, cleaning, port matching the exhaust housing to manifold, etc. I will be doing a lot of driving to break in the turbo, so I can test the new pin. I will compare the old modified pin to the new one to make sure that they have the same #'s.



Mike

 

[formula]

Mike,

The pin looks great Oo.

Is the profile curved or linear? I think I see a bit of a curvature.



Sean

 

[Old Smoky]

Thanks formula. You're right; it does look like there is a bit of a curvature. That’s an optical allusion though, it’s linear. Fueling at 0 boost will be darn close to the same, if not right on. After that there will be increased fueling across the board. So, stiffening up the spring may be necessary to limit low boost smoke depending upon setup and personal preference.



Mike

 

[KLockliear]

We actually used to make a kit (C101) that had a revised pin and different spring for the aneroid. While we don't carry them anymore, one vendor Dynojet, still has 15 on the shelf last I heard. Their part number was DPK90_93 I believe. You can get them at 800-992-4993.