Water injection has been around nearly as long as the diesel engine has been in existence. Instead of intercooling, injecting water into a diesel engine can be used to control combustion and exhaust gas temperatures through a phase change. Known as the latent heat of vaporization of a liquid, when water turns to steam it sucks heat out of the air, which in a turbocharged diesel engine can be quite hot.

Scheid Diesel’s water kit is a lot simpler than many other units, and it’s also a lot more powerful. Where other pumps will run at 200-300 psi, Scheid’s runs at 400-600 and can be turned up even more if warranted.
Before the water injection kit was installed, we needed a place for the nozzle in the intake. Many aftermarket intake horns have provisions for this, but since Cole Dow had fabricated an intercooler delete pipe for the occasion, one needed to be welded in.
After whipping up a piece of aluminum on the lathe, Cole’s brother Cory TIG-welded it onto the engine’s intake piping.
Scheid recommended we place the nozzle close to the intake, so the bung was welded, drilled, and tapped and placed right before the v-band for Dow’s dual-feed intake.

As the horsepower per liter of an engine increases, it creates more and more heat. In stock applications, intercooling and proper turbo sizing can control exhaust gas temperatures without any issue, but if you’re the type of person who can’t leave well enough alone, temperatures can become a major issue.


Cole Dow has a very quick 9-second diesel race truck that was having EGT problems. With the amount of nitrous he was using (0.063, 0.085, 0.087, and 0.110-inch jets on a Nitrous Express progressive controller) he was seeing exhaust gas temperatures that were off the charts. His 1,600-degree pyrometer would be buried just after launch, and at the far end of the track the needle had wrapped all the way around back to the “0” mark. Not only were EGTs off the chart, Dow also would only get a few runs in before he would melt the center out of the turbo housing, melt the exhaust wheel, or both. Since replacing turbos every few runs wasn’t in his maintenance budget, he decided to do something about it.


Normal diesel water injection kits run around 200 to 300 psi and are usually marketed with methanol in mind as a power booster. Since Scheid Diesel’s main business is sled pulling, the company took a different approach and built a mammoth electric water-injection kit designed to cool between 800 and 1,400 horsepower at the flywheel on pulling trucks. With 12-nozzle/1,000psi mechanical injection kits being drastic overkill for most applications, they decided the electric kit would make a good gap filler for those who wanted to cool their charge in high-horsepower applications. In Dow’s case, adding water injection also meant that the nitrous could be ramped up quicker for better 60-foot times, and about 150 pounds of intercooler, piping, pump, and water tank could be shed to save weight.


The Scheid water injection kit’s main objective is to keep things cool in a full-throttle application, which made installation rather painless. The kit includes a tank and pump assembly, a single large nozzle, line, and a Hobbs switch that’s triggered at a specific boost level. Also included is a bottle of cutting oil that is mixed with water to help keep the pump lubricated. Since Dow already had nitrous bottles and a lot of other things going on in his bed, he chose to mount the pump on the floor of the truck beneath the passenger seat.

The water injection system is triggered with a Hobbs switch that senses boost pressure and then makes an electrical connection. Since Dow launches at 20 to 30 psi of boost, the switch was adjusted to 40 psi by using an air compressor and multi-meter so the water would come on right after the truck left the line.
Dow found a free spot at the back of the P-pump’s AFC housing to boost-reference the pressure switch. Once set, a rubber plug was installed on the set screw to ensure its trigger point remained the same.
Cory told us that most race car (or race truck in this case) problems come with wiring, so he crimped and soldered all connections to the water system before installation.
Cole drilled a hole in the firewall to run the water system’s high-pressure line to prepare for the installation of the tank/pump assembly. A rubber grommet was also installed to protect the high-pressure line from damage.
Since Dow already had a fuel cell and twin nitrous bottles in the bed, he chose to mount the tank and pump assembly on the floorboard of his truck. In the meantime, the extra line was looped in the cab until the owner could get to a hydraulic shop to shorten it.

Pump installation only took a couple of hours, with the majority of the time being spent adjusting the pressure and tuning, as well as welding an extra bung into the intake for the water nozzle. We verified the system was working by spraying it in the air (which is good fun), and then with the pressure maxed out we hit the track.


The previous round of testing had left Dowwith a new turbo to try, a 75mm S400 turbocharger with an undivided housing and 96mm turbine wheel. The big turbine ameant the truck was now harder to spool and needed an additional jet of nitrous (0.030-inch) just to get off the line. With exhaust gas temperatures at 1,200 degrees at the starting line, we knew the water injection had plenty of heat to absorb.

The hard-wiring for the pump was installed in order to test it. Once triggered, a single solenoid opens and sends hundreds of pounds’ worth of pressurized water into the engine.
Did we say water? Well, it’s almost that. Water is mixed with a cutting agent that creates a milky substance to keep the pump lubricated.
Cory jumped the leads on the pump to activate the system while Cole held the nozzle, the result of which was a pretty impressive spray that we felt was bound to cool things off a bit.
After we made sure the kit worked, Cory went about wiring in an activation switch on the dash. Things are quite busy on the inside of this truck, which meant Cory had to get creative.
With the water system installed, it was time for some late-night testing, first without nitrous, then with everything on kill.
With the nitrous activated, the truck hit more than 80 psi of boost, enough to blow off the intake pipe right into the radiator. For next day at the track, Dow welded on a strap and clamp to keep the intake from blowing off again.
At the drag strip, the Dodge ran a 9.74 at 139 mph and cut a 60-foot time of 1.39 seconds, which is a new best for the truck. Best of all, it still drove onto the trailer after a number of hard passes.

The nitrous hit immediately off the line just like before, but this time there was a smaller flame, and no turbo-part sparks coming out of the hood stack. The truck still made plenty of heat, but with the water on it built much more slowly. The gauge still swept past 1,600 degrees, but this time it was pointed more down rather than all the way around. Dow estimated his EGT at the end of the track to be in the 2,000-degree range rather than the 2,200-2,400 degrees that was so hard on his turbos. While the truck still ran hotter than he hoped, he made nearly a dozen test passes with no turbo failures, and ran 139 mph back to back, which has been the Dodge’s best speed so far.


We talked to Dan Scheid, owner of Scheid diesel, after testing to get his thoughts on the matter. He advised us that bumping the timing a few degrees more (up from 22 degrees) might help, and that we could also drill the water nozzle out to .030 inches if we wanted, which would provide less pressure but more flow. At the track, with the wastegate wide open, the truck hit a scary 86 psi, which is pretty high for a single turbo. At that point, we decided to halt testing until Dow could get the boost to manageable levels with a larger 66mm wastegate. But with a number of fast passes under his belt and no melted turbo parts, we’d have to say using the Scheid water injection kit was a success.DW




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