When One CP3 Is Not Enough

There comes a time in every modified common rail diesel’s life when the stock high-pressure pump can’t keep up with the fuel pressure needed from higher fuel demand. This is what happened with the 6.7L Cummins in our ’02 F-350 swap truck. If you recall from the May 2013 issue (the six-part swap series ran from the December 2012 through the May 2013 issue), the stock CP3 on the 6.7 could only feed enough fuel to power the truck through the Smarty Tuner’s TNT Level 1. On Level 3, fuel pressure dropped 5,000 psi and power dropped with it. At any level above 3, power and fuel pressure dropped precipitously… all the way down to 12,000 psi in Level 7, the highest we tried. A measly 12,000 psi ain’t on the roadmap to horsepower, that’s for sure.

We predicted some issues, but hoped to make it past Level 1. You could say, “That’s what you get for having expectations,” and we couldn’t disagree. So what to do? There are a couple of ways to go. You can go with a built single pump or dual stock pumps. Several companies make a souped-up, high-volume/pressure CP3 with which you can replace your existing unit. These do the job well for most people, but you may be working that single pump pretty hard. Also, there are a lot of those reworked pumps on the market and wide ranges of workmanship in those modifications. We’ve heard complaints of short life on some of these pumps.

Our truck owner wanted reliability and longevity, so was attracted to the idea of a dual CP3 system. Two pumps share the work, but can double the output and maintain pressure when high flow is required. There are a few companies out there doing these kits, but Pacific Performance Engineering’s (PPE) Dual Fueler kit is a well-thought-out product from a company that has a sterling reputation. Joe at PPE was eager to have us put one on the “Fummins.” Because this is a Cummins engine in a Ford, we had a few adaptation issues but they were minor. PPE makes kits for all common rail Cummins and Duramax applications. Both the Cummins and the Duramax use a similar CP3.

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The PPE kit starts with a new CP3 and includes a bracket kit, drive pulley, idler pulley and longer belt so the pump can be operated by the accessory drive. All the pieces needed to plumb the kit are included as well as a solid metal pipe to reroute the upper radiator hose around the new pump. A wiring harness and Dual Fuel Controller connect the kit to the existing electronics. What’s the yellow tape all about? No, it wasn’t a crime scene. The Dual Fueler was installed at a University of Northwestern Ohio open house event. Prospective students, parents and interested parties can tour the facility over several days. Each of the school’s clubs had an area where they could showcase what they do. The Diesel Club’s area featured their pulling truck (the engine of which has been featured in several DW articles) and the Dual Fueler CP3 installation.

The heart of the Dual Fueler is the second CP3. The part number on it shows it’s intended for a Duramax application. There isn’t much difference between a Cummins and D-Max application but one of them is inlet pressure. The D-Max CP3 is sensitive to inlet pressure, so if your lift pump is set at a high pressure, you may get surging as we did. The D-Max pump is calibrated for a max of eight psi inlet pressure and ours was set at 30 psi. Adjusting the AirDog down to seven psi cured this problem.

After you’ve disconnected the batteries and drained the coolant, you need to remove the fan and fan shroud so you can gain access to the belts and pulleys.

Loosen the tensioner, remove the belt and the fan/water pump pulley. From here, we diverted from the standard 6.7L Cummins instructions because our engine has been adapted from the standard Dodge configuration.

In normal operation, the PPE Dual Fueler is calibrated to divide the fuel flow equally between both pumps. The less hard these pumps work, the longer they last. When high flow is needed, they work together to divide the load, but with the output of two pumps, you aren’t going to run out of fuel. The two pumps aren’t going to supply more fuel than the engine ECM requests, so overfueling is not possible. If one pump fails, the PPE controller will shift the load to the working pump. Certain PPE Dual Fueler kits carry C.A.R.B. E.O. numbers and are emissions legal.

Kurtis Reichley, the master tech who did the Cummins conversion in the first place, also did the CP3 installation. In addition to working for various shops on the side, Kurtis is a diesel technology instructor with the University of Northwestern Ohio so he utilized that facility and the willing helpers from the school’s Diesel Club for the installation and testing of the Dual Fueler. UNOH Instructor and Head of the Performance Division, Randy Lucius, was our Dyno King for both rounds of tests and used the school’s Superflow eddy current chassis dyno.

Dyno Results

We ran the truck on the same dyno as our initial tests. Full disclosure compels us to relate that the dyno had undergone an overhaul, recalibration and software upgrade between our first and round of tests. Likely the second numbers are more accurate, but we don’t know by how much, if at all.

“In normal operation, the PPE Dual Fueler is calibrated to divide the fuel flow equally between both pumps. The less hard these pumps work, the longer they last. When high flow is needed, they work together to divide the load, but with the output of two pumps, you aren’t going to run out of fuel. The two pumps aren’t going to supply more fuel than the engine ECM requests, so overfueling is not possible.”

That said, on Smarty TNT Level 1, we saw a big jump in power and torque with the Dual Fueler installed. Our previous peak on Level 1 was 424 hp @ 2,900 rpm and 861 lb/ft @ 2,400. That’s with fuel pressure barely holding at 24,000 psi. In the later tests, Level 1 yielded a best of 509 hp @ 2,400 rpm and 1,166 lb/ft @ 2,300 rpm (rpm on all runs rounded). That’s both a significant boost in power and torque, but notice how the peak rpms changed. Fuel pressure was holding rock steady at 26,000 psi for all the second round of tests. What a difference 2,000 psi makes!

Because the Fummins had been equipped with an AirDog 165, the fuel lines have been changed over from the stock 3/8-inch size to ½-inch and the stock fuel filter eliminated. Normally, you would install the brass tee on the left to feed both pumps. Kurtis had to adapt for the larger lines. The AirDog kit includes a larger inlet fitting for the CP3 but we didn’t have a second one for the second CP3. PPG does offer a similar fitting so if you have an AirDog, or a similar fuel delivery system, opt for the high-flow inlet fitting. We didn’t see any issues feeding the second CP3 on the stock 3/8-inch line nor any drop in rail pressure but we think big line should feed both pumps. By the time you read this, the second line will have been adapted to the larger ½-inch hose.

The mounting bracket mounts on the top of the head using three bolt holes that already exist.

Oops! We found that the new CP3 wouldn’t mount with the new Shibby intake elbow installed. There wasn’t anything the intrepid crew could do quickly but, fortunately, a late model intake was located and installed and now you will know why something looks a little different in the later shots. It’s hoped the Shibby can be machined and be reinstalled. Who knows how much horsepower we lost with it out of the equation?

We then bumped the Smarty up to TNT Level 5 (we bypassed Level 3 because dyno time was limited). Fuel pressure held at 26,000 psi again and power jumped to 525 @ 2,500 but torque actually dropped a little to 1,123 @ 2400. We then began to see lots more smoke and signs this engine wasn’t getting enough air. Bumping to level 7 proved this idea by delivering about the same power and torque as Level 5, (527 hp @ 2,500, 1,136 lb/ft @ 2,400) but the smoke level was radically increased and EGT went through the roof (1,900 degrees). Level 9 was even worse and showed a big drop in peak power and torque (519 hp @ 2,500, 1,112 lb/ft @ 2,400) and the smoke was so bad it set off the smoke alarms in the building and sent UNOH Safety Services scrambling.

Yep, it’s pretty clear this 6.7L needs more air so the owner is looking into a compound turbo setup. If that flies, we will be able to give you the final answer for our quest for Fummins power.

Summing Up

It’s crystal clear that the PPE Dual Fueler can maintain fuel pressure no matter what. PPE claims that the Dual Fueler can support up to 2,000 hp and we see no evidence to dispute that. The extra fuel flow opened the door to some extra Fummins power even in the Level 1 configuration where we thought our fuel pressure was holding adequately. Most importantly, it can supply enough fuel to feed much higher power levels and not have to work the CP3s excessively hard doing it. This is pretty much a must have above a certain power level with any common rail system that uses this type of HP pump. DW