P-pump tuning advice needed

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Turbolover
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Aug 19, 2011
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I've been trying to tune my truck through trial and error for a while now. I have the mods in my signature and I'm trying to make my truck better for street use and to perhaps eek a little better mileage out of it. I had it tuned with a really tight afc and the no-boost fuel screw most of the way out. I had the fuel plate and afc housing slid all the way back as well. This made the truck smoke very little except for a moderate haze at WOT on the top end. This made the truck get good mileage in town but it sucked on the highway (18/19). Then I moved the afc housing and plate full forward, loosened the afc a bit and left the no-boost screw alone. I gained some top end and highway mileage, but lost city mileage. The most recent tuning I did was to make the turbo spool better, so I made the afc loose, put the no-boost screw about half way, and left the housing and plate alone. The turbo will light at 1500 rpm now, but I have to keep my foot at about 1/3 throttle until about 2000 rpm or it will smoke. It smokes like an old coal train on the top end.

I know 370s are notoriously smokey, but I don't understand why my turbo won't clean up the fuel charge more. I can hit over 40 psi, but I don't have studs, so I don't push it. Other than changing the turbo (which I plan to do in the future), is there anything I can do to clean the smoke up and keep spool-up quick?

Edit: At idle, if I rev my engine up quickly, it'll sound like it has a little bit of a miss or hesitation. It also seems to stall a bit at higher rpms in second gear. Is this because I have too much fuel for the stock DVs?
 
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Drat, I meant to add that. I haven't changed the timing, but I know it's near stock, so probably about 12.5*. The highest I'd probably go is 15.5*. Winter temps around here dip below zero, so cold starting is a necessity.
 
Yeah, I have stock pistons. I'll try changing the timing and see what happens. I don't have the timing tool though, so I might not be able to do that right away unfortunately.
 
in terms of mileage, the marine 370's have a different spray pattern which makes for a less efficient combustion of the fuel and mileage.
also have you messed with rack travel and the afc springs at all?
 
I have all the tools for timing. And I am in Evansville. 16* for timing is good all winter long. Altering the stock timing will make that poping and white smoke go away.

Call me sometime 307-262-0835 -Matt

Is your name Steven by any chance?
 
Hey, Matt, yep, I'm Steven. I believe I know you through facebook. That would be awesome!
 
Subscribed.. similar situation as you, but I get about 11mpg, regardless of city/hwy/towing/empty.

on the move...
 
I think timing plays into how smokey the 370s are too. I run really low timing since I do a lot of stop and go city driving. I do pretty good with these injectors.
If you have an auto, torque converter stall can play into that too. Making the motor lug isnt good for smoke. I think the most efficient spot in the RPM band is around 1800 or so.
 
With Matt's help, we advanced the timing to 16* and ran an overhead and it runs much better now. Low end is better and it's more responsive. I need to increase pre-boost fueling in small increments to increase spool-up, but I won't do that until I get a baseline for mileage from the aforementioned adjustments. I'll post my results after a fuel up or two.
 
set your afc up using regulated air, then make the pre boost just touch the diphram and go 1/8 turns from there till you get it right.
 
I'll try to run this down a little for you'll!

Stock pistons are designed for a 145 degree pattern injector, 370 are a 155 degree, why do we or why did we run them.....simple, cost!

Timing with this odd ball setup is best at 17 degrees or below, as stated 16 is just fine and will help you allot at low outside temps. At 17.5 you will be at the edge of the piston bowl. "it helps when you pull a head that has runs this combo for a few years"

370's are really not that bad but they pop at 3600 psi and that crates low end smoke, bump the pop's to 4200 and it all but goes away.

Pump: Plate is power, AFC is how long it takes to gets there! Use shop air to simulate boost so you know at X psi boost I have full fueling.

No Boost fuel screw is the: how much fuel do you want prior to boost moving the AFC arm out of the way screw. When you get to the point of creating lag on the bottom end due to not enough fuel, you have this one nailed!

Jim
 
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