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Diesel Tech Questions

You've Got Questions? We've Got Answers!

Jason Sands
Aug 23, 2015
Photographers: Jason Sands
Nitrous Q&A, and Results!
(Editor's note: Normally, we don't get to see what happens with our tech answers&mdah;they just go off to never-never land. But recently, a reader needed some last-minute advice for a dyno day, and we were actually able to see how our advice turned out! Enjoy.)
I have a couple questions for you about spraying nitrous oxide in a friend's truck for an upcoming dyno day. He has an '07 5.9L Cummins-powered Dodge Ram with 63mm and 75mm compound turbochargers, 100hp injectors, and dual CP3 injection pumps. The engine is fully built with ARP studs and bolts throughout and 12-valve rods. We're new to this nitrous stuff, and I was wondering how much we should spray (what size jets we should use). The truck has made 700 rwhp at only 38 psi of boost on a non-loaded dyno, and it sees 80 psi on the street. He has a Zex Pro Street diesel nitrous system (the one with the big AN -4 line and AN -3 end) and a 0.125-inch solenoid. Any advice you have would be great. Our ultimate goal is to crack the 1,000hp mark.
James McHaffie
Jefferson City, Tennessee
Photo 2/4   |   Nitrous oxide is something that can be dangerous but is also a lot of fun. We've seen trucks pick up more than 600 rwhp with multiple stages, but for a street application, a big, single solenoid usually works just fine.
Nitrous oxide is both tricky and simple at the same time. One of the biggest misconceptions about using nitrous is that jet sizes equate to specific amounts of horsepower increase. On a gas-powered engine, this is somewhat true. However, on diesels, nitrous works differently; it allows the engine to burn only the excess fuel that is already available to the engine. For example, we have seen power gains between 50 and 200 hp with a 0.080-inch nitrous jet, depending on how much unburned fuel the engine has available for extra combustion.
While there is such a thing as "too much nitrous," most engine damage while using nitrous occurs because of user error. The most common mistake is triggering a nitrous system too early, which can result in snuffing the engine out, a big backfire, or a whole bunch of timing rattle. All these things can damage an engine, so try to avoid them. You can also overspeed turbochargers, but if you're only seeing 38 psi of boost on the dyno, we doubt that will happen.
It looks like your engine is fairly built, and you've already said you want to hit 1,000 rwhp, so now isn't really the time to be conservative. With your combination, your injectors aren't really that big, and at 38 psi, it's obvious the dyno doesn't have much load on it. Keeping in mind that this is an aggressive approach, we would use the largest jetting possible in the nitrous kit, in this case a 0.125-inch jet. Also, make sure the bottle is full and pressure is somewhere in the 1,000- to 1,100-psi range. High bottle pressure is a must for maximum power. However, keep in mind the solenoid may not open if pressure is 1,200 psi or greater. As far as triggering goes, wait until the engine is at least at 20 psi of boost and climbing before hitting the giggle gas. It's hard not to get antsy on a dyno pull that lasts just a few seconds.
Results: We got on the dyno and had some pretty good results. The truck laid down 720 hp with 1,380 lb-ft of torque on fuel, and 960 hp with 1,778 lb-ft on nitrous. We went ahead and used the 0.125 jet. The boost was up 20 to 25 psi over the fuel-only run; it was around 45 psi on fuel and 65 psi on spray. I'm not positive about what the bottle pressure was because we didn't have a gauge, but we used a full bottle and the outside temperature was around 92 degrees. We triggered the nitrous system with a full throttle switch, and we went full throttle at around 25 to 30 psi and 50 mph. Max torque came at 2,600 rpm and max power at 2,900. I believe the truck is laying down more than 800 hp on fuel, but the dyno guy didn't get the truck loaded like he did on the nitrous pull. Thanks for the help.
James McHaffie
6.0L the Way to Go??
I keep hearing about how unreliable Ford 6.0L-powered trucks are, but it appears going fast with any diesel requires upgrading everything. Can you actually go fast with a 6.0L Power Stroke? It seems like Dodge and Chevrolet/GMC trucks need head gaskets and injectors and everything else just like the 6.0L Ford trucks do.
Caleb Marks
Salt Lake City, Utah
Photo 3/4   |   We spotted Vision Diesel's 6.0L-powered Ford Excursion making consecutive 11-second passes at a recent race, which leads us to believe that 6.0Ls can be both fast and consistent.
We really can't say much about 6.0L Fords about being nonperformance engines&mdah; especially after outstanding showings by Jesse Warren's and Jaran Holder's Super Duty trucks at Diesel Power Challenge 2015. Their two extremely strong 6.0L-powered Fords were definitely in the running for the title. Jesse's truck produced dyno numbers of 1,099 rwhp and 1,925 lb-ft of torque, a dragstrip time of 11.12 seconds at 130 mph, and sled pull distance of 290 feet. Jaran's F-250's 990hp dyno reading and 11-second e.t. is nothing to sniff at, either. Since DPC 2015, both of these rides have run low 10s in the quarter-mile, in a dragstrip-only configuration.
Even with only minimal modifications, 6.0Ls can be formidable performance platforms. A few years ago, Project Outcast made 538 hp at the rear wheels with relatively small 185cc injectors and an Elite Diesel Powermax-SSX turbocharger. What's more impressive is that it made these numbers with a stock transmission.
While building up any diesel to the level of 1,000 hp is an expensive proposition, the fact that a much maligned 6.0L can get there at all is quite admirable. We'd even venture to say the price point to get there is comparable to most other high-horsepower diesels, so if your bank account has enough zeros on the end of it, go for it!
Quick Allison Question
What does the "PK" stand for on my Allison transmission?
Larry Henson
via email
Photo 4/4   |   While Allison 1000 automatic transmissions vary slightly from year to year, their shifting strategies and basic design has remained the same&mdah;at least in pickup truck applications.
Since Allison makes its 1000 Series for a variety of different applications, the company has to designate where a transmission is headed after it is built. An Allison 1000 MH, for instance, is a common term for a motorhome application, and it includes a parking brake designed to hold the heft of a motorhome attached to the rear of the transmission. In your case, we think the "PK" simply means it is a model destined for pickup truck usage. Fortunately, we were able to get an answer straight from a friend of ours who works at Allison. Our insider says, "The 'PK' means it's a five-speed, 1000 Series transmission for a pickup that was built in Baltimore, Maryland, in either 2004 or 2005." Physically, there's virtually no difference between the PKs and most other Allison automatics, so your transmission should work and behave just like any other '01-to-'05 five-speed.

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