Power and smoke control in part two of Hot Rod RV’s fuel upgrades

Power and smoke control in part two of Hot Rod RV’s fuel upgrades

When we last left our Hot Rod RV project, it had just received a full complement of fuel upgrades, thanks to Power Driven Diesel. With new injectors, delivery valves, and governor springs, we’d be looking at another 150 to 200 horsepower beyond what we already had on tap. Unfortunately, adding fuel to this mechanically injected Cummins usually comes at the price of additional smoke, especially at low rpm. Unlike common-rail trucks (which can be computer-tuned) there’s little one can do about smoke on older mechanical trucks. Or so we thought.

How AFC Live Works

Power Driven Diesel (PDD) decided to tackle the problem of cleaning up older diesels with a new product called AFC Live, that’s designed for ’94-’98 12-valve Cummins-powered trucks. Using the Bosch P7100’s capacity to regulate fuel as boost rises, Power Driven Diesel was able to design a controller that allows fuel to be ramped-in gradually, avoiding low-end high-smoke situations. AFC Live can also be used to dial in the total amount of fuel available for a variety of activities, from towing (recommended peak EGT 1,200 degrees), to drag racing (1,600 degrees). Along with our Stage 2 AFC Live (which features a “full fuel” override switch), we also installed PDD’s AFC Max travel kit, which allows full, and finer adjustability when using AFC Live. Just as in part one of our article, the work was performed by Total Performance Diesel, in Santa Rosa, California.

Installation and Tuning

Installing the AFC Live controller and AFC max-travel kit was a fairly simple process that took about three hours. Probably the most nerve-racking part is grinding the AFC, but it’s something that’s been done hundreds of times before by Cummins enthusiasts, so we were OK with it. We also ended up coming up with our own hot-glue mounting for the AFC Live controller, as sticky tape and Velcro just wouldn’t support the box’s weight where we decided to mount it. Power driven Diesel’s instructions were very good and easy to follow if we had questions. For tuning once the kit was installed, we called PDD, and they suggested backing off both adjustments a few turns from bottoming out (clockwise on the front red knob, counter-clockwise on the bottom knob), then working on eliminating smoke from there. This turned out to give us a very good baseline.

“Unlike common-rail trucks there’s little one can do about smoke on older mechanical trucks. Or so we thought.”

Driving Impressions

When we first got the truck running with Power Driven Diesel’s 450/500hp fuel kit and AFC Live, the difference in performance was immediately apparent. Even with the 3,000-pound camper, the truck was clearly faster, and turned all the way up it was noticeably so. We also spent a good deal of time fiddling with the AFC Live, turning the knobs every which way, and tuning in the fuel curve. Although a tiny puff of smoke was still there if we hit the throttle hard, the rest of the powerband could be cleaned right up. Hitting the “override” switch at full throttle was also handy for situations like merging or passing on a two-lane road. We couldn’t wait to get the camper off, and do some 0-60 mph and quarter-mile testing.

Since we installed Power Driven Diesel’s fueling package along with its AFC Live and Max Travel kit, we already had the intake horn and injector lines removed. This gave Total Performance Diesel owner Drake Swett easy access to the AFC housing. Owners of trucks that are stock will have to remove the factory tamper-proof screw with a chisel, vice grips, or a screwdriver (basically any way you can remove it without damage). Ours had already been mangled, which led us to believe someone had already been in the pump.

Quarter-Mile Runs

To get both ends of the spectrum, we made two quarter mile passes with the fuel turned all the way down, then two runs with the fuel turned all the way up. We were a little nervous about running a full quarter mile with no EGT gauge, but based upon past experience, we decided to risk it. The last 12-valve we tested that was bone-stock ran the quarter in a yawn-inducing 19.2 seconds at 70mph, so we were pretty happy when we hit 18.28 at 82 mph, even with the truck turned all the way down.

With the AFC housing off, we found a #6 fuel plate, which would have boosted the factory horsepower from 180 hp, to an estimated 250 hp (at the flywheel). For Power Driven Diesel’s kit to work however, the fuel plate is (carefully) removed, and fuel control is performed instead through the AFC Live controller.

With the fuel turned up, the Dodge was a different animal, and was virtually traction-less through first and most of second gear. While the 9.00-second 0-60mph time wasn’t rocket ship-fast, after the converter locked at 70mph, the Ram started picking up steam. Elapsed time with the AFC Live on full tilt was a much quicker 16.57 seconds, at 88 mph. That result puts us squarely in the pack of new diesels; the 2015 Ram for instance clipped off a 16.3-second quarter, but at only 85 mph. We also weighed the truck, and at 6,420 pounds with driver and fuel, our 88 mph felt pretty impressive.

Final Thoughts

When people buy early Dodge trucks, most folks are astounded at how slow they are, to the point where they think something is wrong. In fact, 180hp at the flywheel (or about 140hp at the wheels) just isn’t going to get you anywhere fast in a 6,500 pound truck. But, with Power Driven Diesel’s Fuel Package and AFC Live, we were able to rocket our ’97 out of the slow lane, to where it can now keep pace with diesels that are nearly 20 years newer. Remember, this is all still with a stock 150,000 mile engine, factory turbocharger, and stock transmission and converter.

In our next installment, we’ll be on the dyno tuning, as there’s still a good amount of horsepower to be gained from cheap or free modifications like advanced timing, racked barrels, a Mack Rack plug, and lift pump. As of right now, we’re happy to be keeping up with the newer models, in our budget-built Dodge. DW

With the AFC housing removed, Swett set upon removing the AFC cover, which involved more tamper-proof screws. A chisel and some careful hammer tapping allowed us access to the inside of the housing.
Underneath the top of the AFC, a combination of flat and cupped washers and a spring connect to the AFC foot in the lower part of the housing. All of this will need to be removed in order to grind the AFC barrel and foot.
Power Driven Diesel supplies its own spring and washer package that allows for more travel, and finer tuning, and works with its AFC Live controller to provide very precise adjustments.
Next, Swett removed the AFC foot from the housing by loosening the retaining bolt, and then prying the guide rod assembly up with a screwdriver.
The AFC foot is then ground for maximum rack travel. While this sounds scary, it’s actually quite simple. First, 0.125 is removed from the guide barrel, then the foot of the AFC is ground flat.
The star wheel inside of a P7100 pump is another smoke control device, that is taken over by AFC Live. Accessed through a 8mm plug on the top of the pump, the star wheel is turned all the way towards the front of the AFC.
After these modifications were performed, the AFC housing was re-assembled with PDD’s AFC spring and flat washers.
During the final assembly, the smoke screw at the back of the AFC is loosened until it is basically flush against the inside face of the AFC cover. With PDD’s longer spring, the whole assembly still works and controls low-rpm fuel just fine.
The modified AFC and housing was then installed by Total Performance Diesel’s head tech, Anthony Asaro. The AFC housing has elongated mounting bolts, which allows it to be slid forward or backward. Installing the AFC housing “full forward” towards the front of the truck usually gives the most power, but can result in some pre-boost smoke. If this occurs, simply slide the AFC back slightly towards the firewall.
With the AFC installed, it was time to complete our fuel control package with the installation of AFC Live. The first step involved disconnecting the factory boost reference line to the AFC.
Next, Asaro ran the air lines provided in PDD’s AFC Live kit. We chose to bypass the factory wastegate line for maximum power and boost, although customers using larger injectors (or with a 215hp pump) should definitely install a boost gauge before deciding to disable the wastegate. Anything more than 36 psi is in the danger zone for the turbo, and anything past 42 psi is definitely risking long-term reliability.
After the EGR, air intake, and injector lines were installed, the engine was fired up and the idle was adjusted up slightly due to the new governor springs. Other than the air lines, all the fuel components on our ’97 Dodge still looked stock, yet power would be more than doubled.
With the air lines run through the factory rubber wiring grommet in the firewall, the AFC Live box was then mounted inside of the cab. The large red knob on the front is responsible for the amount of fuel provided, and the bottom knob ramps the fuel in. The switch on the side allows for “full fuel” at any rpm, and is great for racing or passing situations.
To see where we stood at our current “max power” level, we made a quarter-mile run on a GTech with the camper removed, and the AFC Live at its max setting. Our results of 16.57 at 88 mph indicated about 300hp at the rear wheels, or about 380 to 400hp at the flywheel. Stay tuned for some dyno tuning during our next installment where we find out for sure, and see if we can hit PDD’s 450/500hp rating.


Power Driven Diesel

Total Performance Diesel

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