having issues tuning the pump

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dennhop

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Nov 10, 2008
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I went ahead today, and cut my afc foot, and replaced both washers with flat washer, in the diapragm. I sill have a few questions, due to issues trying to retune the pump now. First off, with the spring in the pump, I'm still having issues with getting the boost to push the foot full forward. I set my air compressor around 30 psi (estimated, just on the tank regulator) but I wasn't able to get the foot to go full forward, unless I bumped the pressure up to closer to 50/60 psi. That's with the starwheel all the way forward. I've got the preboost screw set to barely touch the afc at rest. When I took the truck out today, to test it, I'm smoking a ton if I hit it from a dead stop. I'm still building boost, up to about 35/40 psi, but my egts are rising twice as fast as my boost....I hit 1600 degrees easily, under full throttle.
My question is those of you using an air compressor to set the afc, are you using an external regulator, or am I doing something wrong. I don't think I should have to have the starwheel full forward, for 30 lbs of boost. Also, I thought I had read something to he effect of usig a stock gov spring in place of the afc spring? Would this help at all, or do I need to readjustment the starwheel again? I'm trying to maximize my performance, without creating giant clouds of smoke...plus, i think the way its set right now, I'm overfueling the turbo on the low end. Any help would be greatly appreciated.
I have read all the afc threads, so I understand how it all works together, just not sure if my end results are working as they should.
 
dennhop said:
I went ahead today, and cut my afc foot, and replaced both washers with flat washer, in the diapragm. I sill have a few questions, due to issues trying to retune the pump now. First off, with the spring in the pump, I'm still having issues with getting the boost to push the foot full forward. I set my air compressor around 30 psi (estimated, just on the tank regulator) but I wasn't able to get the foot to go full forward, unless I bumped the pressure up to closer to 50/60 psi. That's with the starwheel all the way forward. I've got the preboost screw set to barely touch the afc at rest. When I took the truck out today, to test it, I'm smoking a ton if I hit it from a dead stop. I'm still building boost, up to about 35/40 psi, but my egts are rising twice as fast as my boost....I hit 1600 degrees easily, under full throttle.
My question is those of you using an air compressor to set the afc, are you using an external regulator, or am I doing something wrong. I don't think I should have to have the starwheel full forward, for 30 lbs of boost. Also, I thought I had read something to he effect of usig a stock gov spring in place of the afc spring? Would this help at all, or do I need to readjustment the starwheel again? I'm trying to maximize my performance, without creating giant clouds of smoke...plus, i think the way its set right now, I'm overfueling the turbo on the low end. Any help would be greatly appreciated.
I have read all the afc threads, so I understand how it all works together, just not sure if my end results are working as they should.
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When does the foot begin to move?

When you say forward do you mean towards the front of the truck or forward towards the firewall?
 
The foot will begin to move almost immediately, but I can't get it to push full forward, unless I up the pressure on my air compressor. The starwheel is full forward to the front of the truck.
 
dennhop said:
The foot will begin to move almost immediately, but I can't get it to push full forward, unless I up the pressure on my air compressor. The starwheel is full forward to the front of the truck.
Click to expand...
That's excatly what you don't want. Your flooding the charger with fuel before boost is reached.

You don't want the foot to move till 15 psi or so. Worry about the bottom before you start trying to get full fuel.
 
Ok, so now I'm confused. I thought the starwheel adjustment was supposed to allow the foot to go full forward with the corresponding amount of boost? So if set up correctly, the spring tension should allow the foot to be all the way forward with a sustained amount of boost...ie 30 lbs?
If the way I have it set right now, assuming my line pressure is accurate, at 30 psi, I'm only getting approximately half travel of the rack. I think I might go get a cheap boost guage from vatozone, and see if my pressure gauge on the compressor is accurate, and try to reset the afc starwheel accordingly.
 
On my 98' with 180 pump, the stock spring takes about 20 psi to get full travel.

A few days ago, I played around with a stock governor spring from my 180 pump and it takes 48-50 psi to go full travel. This is with the starwheel set to full loose, least amount of preload, or screwed all the way toward the front of the truck.
 
dennhop said:
Ok, so now I'm confused. I thought the starwheel adjustment was supposed to allow the foot to go full forward with the corresponding amount of boost? So if set up correctly, the spring tension should allow the foot to be all the way forward with a sustained amount of boost...ie 30 lbs?
If the way I have it set right now, assuming my line pressure is accurate, at 30 psi, I'm only getting approximately half travel of the rack. I think I might go get a cheap boost guage from vatozone, and see if my pressure gauge on the compressor is accurate, and try to reset the afc starwheel accordingly.
Click to expand...
Starwheel placement is fine, you can adjust it tighter to increse spring psi but after so far you cause spring bind which will limit full fuel.

You want a stiffer or longer spring so the foot doesn't move till desired psi.

If I'm understanding you right your foot is moving as soon as it sees boost. That's what you don't want.

Are you verifiying full fuel without the spring?
 
bsmith said:
Starwheel placement is fine, you can adjust it tighter to increse spring psi but after so far you cause spring bind which will limit full fuel.

You want a stiffer or longer spring so the foot doesn't move till desired psi.

If I'm understanding you right your foot is moving as soon as it sees boost. That's what you don't want.

Are you verifiying full fuel without the spring?
Click to expand...

Correct. When I apply air pressure from my air compressor, as soon as the air hits, the foot is moving. Now, assuming that I have 30 psi, the foot is only moving about halfway on the rack. When I bump the compressor up to around 50 psi, the foot will travel the full length of the rack.
That all being said, I'm a bit leery about what the actual pressure is coming from the tank-I'm guessing I just need to go pick up the boost gauge and see what my actual pressures are, before going too crazy.

I did make a few adjustments to the afc tonight, and here's what I did, and the results.
I slid the fuel plate towards the cab a smidge (tried to eyeball about a quarter of the way back, so a smidge is probably the closest unit of measurement that accurately describes just how far back it really is, lol)

I went ahead, and messed around a bit more, trying to get an accurate read on the psi coming out of my air compressor, and tightened up the starwheel a couple of turns...not sure how many to be exact, but I'd guess about 2 full revolutions, give or take.

Also readjusted the preboost screw, so that it's barely touching the foot at rest. Threw it all back in the truck, and went for a test drive. Egts didn't hit 1600, and also didn't seem to climb as fast. Throttle response seemed a bit crisper at speed (if I was already driving and hit the gas, it seemed to respond a bit quicker)
If I hit the gas from a stop, I still got a pretty large cloud of smoke, and a second or two of lag, before the turbo actually spooled, but it did run to around 30 psi pretty quick. I also noticed that the turbo wouldn't break 30, whereas before, if I hit it, it would peak anywhere between 35-40, and then drop down to about 30ish. Now they peak at 30, and hang around 25, until I hit lockup.

I'm a little unclear as to how to test for full fuel, without the spring. Do you mind talking me through the process?

Also, maybe I'm just being retarded, and expecting too much, but can I realistically expect full travel with a stock hx35, no injectors, a mild plate, and gov springs? Or am I pretty much running where I should be right now?


EDIT: BTW, I do know its the stock spring, due to the fact that I've had to modify/break every one of the tamperproof screws on the AFC housing, so I don't need to worry about the AFC spring being a different one.
 
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Ok if your all stock id tighten the star wheel some more so your foot doesn't move as soon.

You can expect full travel. But don't expect to use all the fuel at full travel with your stock charger
 
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