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.”
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.
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 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.
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
Power Driven Diesel
Total Performance Diesel