I've been swamped with e-mails lately. Fellow owners having drivability problems, asking how to get the most from a stacked 3rd generation truck, or wondering why a particular "performance box stack" wasn't performing to their expectations. So, I thought I would try to cover the problems that I've seen owners running into and some common sense approaches to getting the most from a stacked 3rd generation HPCR truck. I've tested all but two lines of boxes on my '03 HPCR and I'll be using my current selection of upgrades as they cover some of the more popular choices. I don't endorse my current choice of modification but they'll serve as good examples.
A little background on myself and my vehicle. I've been thru a lot of "stacks" (or box combinations) on my 2003 Dodge Ram and never intended to take the truck to the levels that I have. However, after each addition or change I would start at the lowest available settings for the combination of performance boxes I was testing and slowly work my way up the ladder noting changes and reactions in the truck. Using this approach has made it quite easy to find my vehicles maximum capabilities without even the slightest damage to the truck. My last runs on a load dyno netted me three runs over 600 hp and 1170 to 1230 lb-ft of torque. The only box in my current stack that was on it's highest available setting was the VA C3.1 pressure box, the others were well below their maximum settings.
The vehicle: 2003 Dodge Ram, HO Cummins, 6 speed, 3.73 gears, Piers Diesel Research Twin Turbos, ARP headstuds, TST PMCR timing/duration box, Bullydog Downloader, van Aaken C3.1 pressure box and Formula-1 injectors.
First and foremost, the largest mistake I see owners make is attempting to stack boxes and run them at the max available levels. They assume that if a box has "X" number of levels that the top setting must make the most power, right? Read on and we'll see. The same goes for almost all boxes and downloader whether used in a "stack" or as a stand alone box. I can't say this strongly enough. If you want to get the most from your 3rd generation truck forget about what level your running your boxes on, period. People are far too hung up on what Power Level the box is set on instead of how much power they are actually making. Take the TST for example. If it came without level numbers and just had up and down arrows you would get on a dyno, turn it up until it max horsepower was achieved (or the power began to fall off), sit back, look at the graphs and say "WOW"! It wouldn't matter what unknown level you were on. The aftermarket has been kind enough to give us boxes that are capable of more than our fuel systems can support. This is rare in the aftermarket industry and the advertising is misleading at best. Remember this. Maximum settings don't necessarily produce maximum horsepower.
Below is an excerpt from one of the e-mail replies that I sent out to frustrated fellow owner. He had just installed twins and was having problems while trying to run at higher levels on items used in his particular stack. Each box used in his stack worked flawlessly alone or with one other box but caused problems when everything was "turned up". Following these simple guidelines helped him cure his stacking problems and achieve maximum horsepower. Hopefully they will help in your quest also...
Lift Pump: Everyone has their favorite in this arena and opinion run wild across a vast range of pumps. What your looking for in a lift pump is a unit that can maintain at least 18 psi at max load and rpm. This has been hashed over too many time for me to recommend a pump, however, a Fuel-Boss mechanical is my preference. A high pressure unit would be my choice in the electric lift pump arena.
Fuel Feed System: You really don't need to do anything fancy here. Add a Big Line Kit or Maximizer to get the fuel to the CP-3 high pressure injection pump from the filter. No real need to change the factory supply lines, just let them flow to their potential. I made my 600+ hp runs on factory stock lines with just a Big Line Kit and thru the stock filter with a fuel pressure of 18 psi.
TST (example only): Turn the Torque Enhancement setting down, and I mean WAY down. I run the old aggressive singles program and never turn the TE above 2. All the TE does is start draining the rail down low in the RPM range and when your running on the ragged edge the CP-3 never gets a chance to catch up. You can watch this on a rail pressure gauge if you have one.
Pressure Box: If your comfortable running one, add a pressure box that is strong down low to pick up the bottom end torque. This has two effects on the system and the drivability. One, it picks up the bottom end torque given up by lowering the TE settings on a duration box and helps spool the turbo (twins in my case). Two, it actually gives the CP-3 a head start on the run by building pressure earlier AND by not needing the additional duration down low for power. It's a win/win game for the CP-3. My choice for additional pressure is the van Aaken C3.1 over the EZ or other boxes and I have a good reason for this. When I sent my injectors in to be upgrade by Formula 1 they had ZERO signs of erosion due to pressure. At the time I had been running the C3.1 on the High setting for over 30k. Other injectors that had been run with various higher (stronger) pressure boxes were showing signs of erosion and damage when examined. The C3.1 stays within factory safe rail pressure levels and within the levels that are readable by the factory rail sensor.
Power Pup (or Triple Dog): Downloader's are a touchy subject. If your comfortable running one you have to make sure that your know what parameters each setting is affecting. On the Bully-Dog products there is no additional rail pressure added on the Tow setting. This allows you to stack a pressure box with them safely in the Tow setting only. On the higher setting they do add additional pressure and I wouldn't recommend adding a pressure box at all. High pressures and the cumulative affect of stacking two boxes that affect the same parameters is a recipe for disaster long term.
Injectors: Smaller is better. With the 3rd generation trucks rail pressure is everything. A smaller injector will help the fuel rail maintain pressure and atomize the fuel charge better. If you want to run larger injectors plan on having to turn the boxes down even further for the same achieved horsepower.
We're pushing our fuel systems to the ragged edge usually and you have to gain a little from everywhere. Nobody knows what settings your on when you blow past them at the track so forget about what levels your running on and listen to what the truck is telling you. My top runs were made with the TST at 5x2, PP on Tow, and the little C3.1 pressure box. I had enough rail pressure left to pull on level 6x2 but I was out of dyno time and so happy with my numbers that I didn't even think to make another pull.
So, start at the bottom on everything and work you way up. Start on say 3x2 (if using the TST), Tow (if using a downloader), and add whatever amount of pressure your comfortable running. Then step the HP setting up on the TST one level at a time and leave the TE at 2 or below (and I mean leave it there). You can creep the TE setting up later if you still have rail pressure available. Keep going up on the TST until you get a misfire, bursting, or high EGT's and back it down one level. That will put you at the max power level sustainable by your fuel system. As an example we stepped my truck up to 7x2 on the rollers and EGT's went thru the roof while I lost 139 hp at the same 60 lbs of boost. The smoke still cleaned up on the top end thanks to the twins but the rail was done at that point.
The truck will tell you when it can't give you anymore either by bursting (missing), as the Chevy guys call it, or by high EGT's. Yes, the Chevy guys ran into this 2 or 3 years ago, long before we ever thought of running a CP-3 dry.
Listen to your truck.