Engine/Transmission (1994 - 1998) tune pre boost low end fueling

[LVJUNIOR]

I am trying to dial in my low end fueling. I can get the smoke heavy or light with the star wheel on boost. What I am having trouble with is the pre-boost fuel. If I tune it to a light smoke but still smokier than I would like it, it takes forever to light the turbo. If I move the AFC housing forward just 1/16" it lights quick but smokes enough to hide the car behind me.



What do I need to do to get it to start lighting the turbo quicker without getting a ticket for excessive smoke?

 

[biggy238]

Have you modded the afc and set it with an air reg? I did this on mine and it's reasonable with a 10 plate and stage 4 injectors.

 

[LVJUNIOR]

The only modding I know of is sliding it forward or back, moving the star wheel or changing the spring. It has the light spring it it right now. I don't know how to "set it with a regulator". do you know were I can get info on this. I have been looking through old posts for a week to no avail.



What size tires are you running and what is your fuel mileage. Mine sucks. I get 12 on the highway empty at 70mph 2000rpm and 10. 2 towing a little #4000 fifth wheel

 

[hsmith]

I run the same plate and sticks as you and towing my 14k plus fifth wheel my mileage is better than yours empty. Maybe it is the right foot.

 

[biggy238]

I get 18 with 3. 54s and 35's. sounds like your timing is odd if you're smokey and have that low a mileage.



I found what I did in this thread and it's links. Mod the AFC? - Competition Diesel. Com - Bringing The BEST Together



You can take an air regulator and a rubber tipped blow nozzel and tune the afc on a bench. I think mine really starts to kick out of the way around 18psi and is ful forward by 40 psi.

 

[LVJUNIOR]

Biggy238

I have 4. 10s and bfg mudders what are your 35's



I am sure of the timing as it was reset at 16. 5 before my last trip and the mileage didn't get any better.



I pulled the AFC and put it on the bench. The fuel plate was farther forward than I thought. I have no smoke on the top end at all. The AFC would travel full forward with my regulator turned down as far as it would go at 10psi 20psi would make it get there pretty quick and 40psi would just about snap it full forward. I have the light spring and the star wheel is just forward of center in the bore. At anything over 1500rpm I gan get it to slam to 42psi of boost very quick.

 

[charlessmith]

I've got a similar setup, with DDP2 injectors. Here's a pretty good discussion of AFC tuning, down in the middle of this thread:
Turning up a P-7100 pump - Dodge Cummins Diesel Forum

I adjusted the "smoke screw" on the rear of the AFC to let the AFC foot start at the rear of the AFC housing, then adjusted the AFC cover fore-aft position and the star wheel to get decent off idle acceleration without black-out-the-road smoke. Doing this seemed to limit my full throttle full boost power, I'm guessing because the AFC foot now can't get out to the way to let the fuel plate do the controlling of full fuel.

I figure I need to grind the front of the AFC foot so the diaphram can move it further forward to get it out of the way. Grinding the back of the foot will only make the smoke problem worse.

 

[RHestand]

Hey guys,

Thanks for this great thread and posts.

This is a huge amount of info. for me to absorb about the P-pump etc.

Now I've just got to get my printer up and running again.

Ray

 

[biggy238]

Tip to the wise, when you find a thread, save it to the a hard copy. Then you can print it for the rest of eternity.



I think charles hit on what you need, however I would grind the barrel and not the foot, and put a heavier spring back in, then tune the pre-fuel boost with the screw, and set your main spring to control your smoke and top end fuel with the air reg. It sounds like your spring just doesn't have enough tension to control the smoke show, even though it lights the turbo.



Also, I'm on 35 inch courser CT's. And keep in mind i'm no guru. Fulmer has one of the greatest knowledge bases you could tap for this subject.



I'm still on my HX35 and the smoke is controlable. I never touched the smoke screw. It will roll it though when I want.

 

[charlessmith]

When you put in high flow injectors, the throttle can become much more sensitive. Sure, black smoke can be controlled by a careful right foot ... but when on cruise control you can leave a trail of black smoke puffs, as the CC keeps stabbing the throttle and then letting off. Putting a restriction in the vacuum line to the cruise control unit will help with this, but it get's you thinking seriously about AFC adjustments.

 

[LVJUNIOR]

I can clean the smoke up except pre-boost. I leave the light with an egg shell under my right foot and still have a thick haze behind me. I have no bottom end unless I push the afc forward and make a thick smoke cloud.

 

[charlessmith]

On my truck, there is a *very* fine line between no bottom end and too much black smoke. And I'm still running the stock AFC spring. I had to slide the AFC cover just a little a little bit at a time.

I'd try a heavier spring in the AFC. Your light one may be letting a slight bit of boost push the AFC foot clear out of the way - thus the heavy black smoke when you build a little bit of boost. Try turning the star wheel to tighten up the spring pressure, and see if this helps.

Too much fuel (like real heavy black smoke) will keep it from building boost as quickly as it would otherwise.

I have been trying to keep the fuel mileage OK. Before the DDP2's I could get 23+ MPG at a steady 65 MPH ('96 2WD unloaded). After the DDP2's, I have got mileage almost back to where it was.

On my '97 4WD, stock injectors, I'm doing good if I can get 20 MPG at a steady 65 MPH.

 

[Mhannink]

The only modding I know of is sliding it forward or back, moving the star wheel or changing the spring. It has the light spring it it right now. I don't know how to "set it with a regulator". do you know were I can get info on this. I have been looking through old posts for a week to no avail.



What size tires are you running and what is your fuel mileage. Mine sucks. I get 12 on the highway empty at 70mph 2000rpm and 10. 2 towing a little #4000 fifth wheel

whats killing your fuel milage is the 4 inch lift 35 inch tires and the detroit locker and especially the truetrack front thats really gonna kill the mileage. take the lift off put 33's on and take the true track out and you'll go from 12 to 17 18 maybe even 20 depending on your rear gears. also is your speedo corrected for the tires? 70 and 2k rpm doesnt sound quiet right for any trans/ gear combo.



as for the smoke i ran an ii silver bulllet 62 i had 2 chips 150 horse sticks and an ats manifoild and it still didnt light. without tons of smoke.



i think part of the problem is your right foot is a little heavy. that creates a lot of smoke. you have to remember the turbo needs heat to wind up. only put enough throttle to it so that its a very slight haze at the most, and it will spin up as fast as its going too. if you want a better way to control it tighten the afc spring till it will only haze once it builds boost. this will probably provide a little too much smoke at the bottom end. however you will probably have to really mash it to get that level of smoke.



what you really should do though for good power and less smoke is put a smaller turbo on the 62 is just a tocuh to big for a dailey driver that you want to burn clean. something in the 57mm range will work much better. a cheaper route to go is to put a 12cm housing on instead of the 14 that will wind it up faster but make it run hotter. the best way to go is a 57/14 form htt and adjust your afc accordingly.

 

[LVJUNIOR]

Well I finally got the fueling tuned right were I wanted it (still have no power until 1500rpm). Was out on the final test run to check the last adjustment. When I laid into it and got it up to boost antifreeze blew all over the windshield. Parked it in the driveway and the cooland was at a rapid boil in the overflow. Shut it off and restarted it and made a nice white cloud.



Brand new ported head +haisly fire ringed gasket +brand new ARP head studs +white cloud = a lot of crying

 

[Mhannink]

yeah a blown head gasket is never fun. but heck its only about an 8 hour job to do.



i think i just found part of your problem though your looking for power below 1500 these engines from the factory make peak torque at 1600. i think your expecting more out of the engine then what it can do. all the cummins i have driven only make good pulling power between 1600 and 2200 rpm and for racing they do well form about 1500 to 3000.



it seems like maybe your trying to get the engine to provide nearly full power lower then it physically can. all these perforemance products increase power and some even increase bottom end power but they are talking 1400 to 1600 rpm and its only marginal improvements. the realy power boosters like what your running increase power form about 1600 up. in the engines orginal power band.



to increase the bottom end like what your thinking requires stroking the engine out. it needs more mechanical levearage to be able to build the power lower down.

 

[LVJUNIOR]

I don't want anywhere near full power or even towing power down low. I just want to be able to get going on rough terrain off road without mashing the peddle to the floor. If I could get it to leave the stop light as good as my bone stock 2003 I drive at work I would be completely happy. I hope the head gasket leaking coolant into the cylinders was causing my problem and it will be better when I get the. New head on.

 

[Mhannink]

what gears are you running? both in this truck and ur daily driver? what tires are on the daily driver?

 

[LVJUNIOR]

This Truck is my daily driver. I am running 35's and 4. 56 gears which I believe gives me the same rpm as stock tires and 4. 10's