Gizmo52

So in theory we can just put an adjustable boost elbow on the head where the boost reference line for the AFC housing is and control how much boost the AFC sees just like the boost elbow does on a waste gated turbo correct? Thus slowing the fuel rate at low rpms and clearing up smoke?

BC847

Yes.
- I used a source of compressed air, that was controlled by an adjustable regulator, including a gauge to see what the regulator was putting out.
- You will need a second gauge to see what the elbow is putting out.

With the above, I was able to supply the boost-elbow with 10psig (this represents low, just off idle boost) and adjust the elbow so as to put out 5psig. Then increasing the supply to 60psig (this represents full WOT boost) and adjust the elbow so as to put out 30psig.

UNDERSTAND: The Boost-Elbow that I'm using includes a vent-port that vents an adjustable percentage to atmosphere. This is needed as an elbow without amounts to a simple restriction to the flow powering the AFC. You need flow, in order to use a portion of it, and waste the balance.

Make sense?

Overall, this amounts to a 2/1 ratio. The Boost-Elbow reduces the input by 50% across the board.

It's a PIT@ to set-up, but works relatively well.

NOTE: If you're running twins and are pondering going this route, consider simply powering the AFC directly from the Primary. Rounding things off substantially, it represents about 1/2 that seen at the intake-log (Secondary output).

Gizmo52

Ok so I understand the concept I just don't understand why I need an elbow with an adjustable max. As long as I'm slowing down the flow to the AFC by half the flow why does it matter what the max is regulated at?

What elbow are you running? I assume its like a manual boost controller with an adjustable bleed vent?

Also im running a s363 single 63/68/12 so I should be ok. I just want to cut down on low to mid smoke and speed up my spool

BC847

In that context, it's assumed you're on your way to full throttle. In that sense, yes, simply delaying the signal is good enough.

But what if you're at part-throttle. In that sense, simply restricting (delaying the full signal) is not accomplishing what you set out to do.

At part-throttle, you need a part-throttle AFC function.

mknittle

This thread goes in that direction.
https://www.dieseltruckresource.com/...pgrade-323995/

Gizmo52

Ok wow not that makes total sense! Only thing I don't understand is I just made and adjustable boost elbow type like I was talking about before you brought up the MBC with the bleed off valve and I somehow gained like 10 psi of boost?!

Gizmo52

Could a small boost leak at the AFC line cause me to go from 45psi at wot in fourth gear to 55 psi? Or is the engine now burning the fuel better with the adjustable boost elbow half shut?

oliver foster

55 PSI!
How do you have your injection pump tuned?
Are you using head studs?

Gizmo52

I machined my own pin kinda like the m5 pin from m&h, got the m&h timing spacer, I'm at about 18.5* timing, smoke screw all the way out, star wheel all the way up, 3800 gov spring, 5x.014 injectors, mighty diesel head bolts, 3" crossover tube (non ic), Borg warner s363 (63/68/12), banjo bolts modded in my fuel lines, 60# valve springs, ported and polished my head and manifold, high idle screw removed, 4" straight pipe, Valair 600hp 1100tq clutch

Still no fuel system, in the process of making my water meth kit and traction bars. Axle shafts will be here Monday so I can put my posi in.

mknittle

I want to see some. pictures of your truck.

Gizmo52

Sorry been busy lately but here's some pics of the engine bay fuel pin and truck. Got my posi in finally too

ofelas

Gizmo - very nice !

93D250

This is what I came up with, not sure how it will work; I haven't tried it yet. Basically it's a needle and seat with an adjustable bleed right off the AFC top. There are 2 .045 holes between the needle/seat and locknut. Also machined the top so the fuel pin gets full travel. I'll report back here how it works but technically one could put a boost elbow off ebay etc in the same spot...

Made on a garage size small lathe.

BC847

NICE!

You might now consider doing something similar with the boost reference line that feeds the AFC. The end result would have you be able to control the ramp (if you will) of the AFC via the gizmo shown above. A restriction in the feed-line would make it so the feed-line can't overwhelm your gizmo.

Make sense?

93D250

I think replacing the oem hard line with nylon is a good idea in any case.

I started small with the bleed holes on the gizmo but they could be easily enlarged a lot to increase bleed. I definitely like your idea of a restrictor for the inlet line, the overall boost the diaphragm sees could then be limited. I think gizmo is a good name for this thing

Getting the thing to ramp right is probably going to take a lot of trial and error...