BC847

If you're like me, you've got the fuel screw run in, a modded fuel pin, etc. I've got my star-wheel run all the way up just shy of coil-bind of the spring trying to clean up the low boost smoke.

OK.

My truck came stock with about 19psig max boost. I assume the AFC spring is selected with that boost figure in mind, and the star-wheel dials it in.

If we want to delay the AFC from adding more fuel till the turbo gets spooling, we need to change the spring to something that works with the new boost figure. . . . . . Right?

I've thought about how a spring could be cyphered and my head hurts.

If boost is boost, and air is air, . . .. and the AFC diaphragm/chamber is a pneumatic air motor just like the waste-gate actuator . . . . .

Why couldn't we just use a basic boost-fooler to better control the AFC using the existing spring?

JPR Ram

Well, because I do beleive a true "boost fooler" is an electronic device that changes the eletrical signal sent from the MAP sensor to the ECM. Correct me if I'm wrong, but I don't think 12 valves have MAP sensors or any electronical boost reading device. I think 1998.5 24 valves were the first to have such an animal......

BC847

Our PCM watches the crankshaft position sensor so as to tell the alternator the engine is running. . . . . .. and that's pretty much it.

The 1st gen VE injection pump's AFC is driven by basic boost air pressure working a mechanical actuator.

But thanks.

apwatson50

You know what this isn't a half bad idea! I believe the technical name for the device you want to install would be a ball and spring MBC (manual boost controller). And I happen to have one i'm not using. I just have to replace my hard line from the head to a flexible line to install.

I had always planned to install a valet valve, but just never got around to it, plus that would involve extra wiring.

BC847

Yup! "MBC" is what I was looking for .. LOL!

I've got one on my waste-gated exhaust housing.

Rampage1967

What about an adjustable bleed in the line??

91.5CTDBanks

Yep, Manual Boost controller. Been running them for years. I am not there yet to need one, but..... You bleed off the boost 'signal' before it gets to the AFC.

GO OVRIT

Sounds like a writup getting ready to happen.

unixcowboy

Yep, that's exactly what it does...
Bleed off the boost before it gets to the MAP sensor....Fools the PCM into thinking your running less boost than you are.

You could put one in the AFC line and it would cut back on the deflection of the diaphragm thus cutting back on the fuel. You could adjust where you wanted the fuel cut back.
ONE SMALL problem BC- - What are you going to do when you WANT all the boost to get to the AFC ?
I ran one on my LeBaron in 94..Told the MAP sensor I was running less than 10PSI, that's what Chrysler had the cut off set at. Then when the boost built the engine would start running lean and the PCM would give it more fuel...
OUR fuel isn't controlled by a PCM - it's controlled by the AFC. If you tell it we have low boost it will feed low fuel.

BC847

Y'all forget about a MAP sensor, it only adds to confusion.


A Manual Boost Controller (MBC) would allow us to alter when the AFC begins to move. Just like a MBC allows us to alter when the waste-gate on our turbochargers begins to move.

Mechanically, they are both the same.

In the case of my stock/OEM AFC, it's setup so as to provide full fueling at about 15psig(+/-) .. using the OEM spring. Adding a MBC should allow us to better adapt the OEM AFC spring to the much higher boost figures we commonly see with our modded trucks. We would still have to set the star-wheel for fine-tuning.


Again, the goal I have in mind is to substantially reduce if not totally eliminate the cloud of smoke the occurs when one stabs the throttle from idle. In my mind, I think I'm in essence delaying the function of the AFC pending a little turbo spooling action.



I must admit that I'm not 100% sure that this will fix the problem. It may very well be that since we all have our fuel screws run in way over stock, that at a no boost condition, there may already be too much fuel available to get around the smoke.


I've got a bunch of stuff going on with my heap right now so it may be two or three weeks till I can focus on this.

Another thing, this may end up being counter productive in the sense of drag-racing.



Hmmmmm . . ..

bgilbert

The afc cover can easily be drilled and tapped for 1/8npt, or if you want to put the boost elbow in the cylinder head (1/8npt) and build your own tubing that can be done.

Or get someone to send you a much tighter spring, like a complete silver colored one from a nonIC'd truck to try out.

Or try pipe plugging the afc reference at the cylinder head and see how that runs.

Fergavs

When I am blowing smoke just off idle I have no boost, thus the reason for the smoke. So lowering the amount of boost (already 0) that the afc is seeing wont help any. Now if the afc hits full fuel at 19psi then I can see delaying it to 25-30psi+ would help clean up some midrange smoke. If full constant control is wanted then a more expensive EBC is used instead. Then you could actually run 2-3 programs set for multiple uses. ie. drag racing/fuel economy/towing . Some thing like this would work and give you 2 settings,

http://cgi.ebay.com/ebaymotors/Elect...spagenameZWDVW

Now this would all be dependent on the AFC controlling fuel that much. I have never put a "valet" switch on my truck or ran with out the AFC so I'm not sure as to how much it effects driveability.

wannadiesel

I think if you used an MBC you would get all your AFC fuel as soon as the MBC opened, kinda like an on/off switch. The same thing could be accomplished with a hobbs switch added to a valet setup.

Alwaysworking

what i think makes me want to try it is the cost of a valet switch set up VS the cost of makeing a MBC,

BC847

It's my understanding that short of some bamboo under the nails, the Bosche folks ain't talking about spring specs. further, I don't know of an OEM application of a VE based engine running 30, 40, or more psig boost.

Anybody know of a range of springs available and the individual specs? Kinda like the breakdown of the governor springs?

That is perhaps more accurate of my thoughts. And you're dead-on regarding the 0 boost condition. I wonder if there's a lever/cam profile of the AFC linkage that could be altered to increase the overall range of the AFC yet still maintain use of the existing fuel cone/pin that's being worked by the boost/diaphragm.

I'm also thinking that a MBC type of deal could be implemented inexpensively with decent gains in fuel economy yet still allow getting on it when needed. Getting your cake and eat it to?

Dave I don't believe the MBC acts as a simple on/off type of control.

Consider the typical waste-gated exhaust housing. If I'm not mistaken, the waste-gate actuator doesn't necessarily go from completely closed to completely open at one specific psi. I think it's more of an start opening at this psi, and be full open at a higher psi. Maybe vaguely linear in it's stroke?

I think Fergavs is more inline with what the effect my be in that an MBC would effect part throttle/low boost conditions.

With the smoke screw typically fully withdrawn, you're stuck with that fueling which is obviously influenced by the main fuel screw.




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