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Adding 117 HP with Scheid Diesel’s Lightning Pulling Injectors

We’ve started building our ‘95 Dodge “Green Monster” Ram to run 10s in the quarter-mile and make 1,000 rear-wheel horsepower, but we knew we needed to walk before we ran. While P-pump Dodges have huge power potentials even in stock form, one thing that is holding us back is our stock injectors. In factory form on ‘94-’98 Dodges there are three different types of pumps, 160-hp, 180-hp. and 215-hp pumps. While each has their own specific traits, the 160-hp pump (which we have) is generally known to fuel the least compared to 180 and 215 pumps. We had to get more fuel in somehow to make more power, and injectors were the most obvious choice.

Brown’s Diesel tech Gustavo Quezada would be the mechanic performing our injector swap. He started by removing the intake horn to gain access to the injection pump lines.

Next, the injection pump lines were removed from the injectors and injection pump, one group at a time.

Sizing Things Up

Our ‘95 Dodge was built with injectors that had 5 hole nozzles at 0.009-inches in diameter (or 0.0095 depending on who you talk to) and were just fine for the factory 160 horsepower power rating. Larger injectors could see significant gains however, and we decided to step right past “larger” and step up to “big.”

When it comes to injectors, a small increase in diameter means that the total area of the nozzle is greatly increased. A set of 5×0.012 or 5×0.14 injectors would be considered a big step up. With our ultimate power goal in mind, we stepped up to 5 hole by 0.018-inch injectors from Scheid Diesel, which would give us a huge increase in the amount of fuel we could inject. Our overall fuel would still depend on factors like the AFC and rack travel, but trust us, these units put out some fuel.

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In addition to the added flow, Scheid’s injectors also have a slightly increased pop pressure, which results in more efficient power. Another lesser-known tidbit is that extra fuel drives the turbocharger harder, which is why you’ll see sled pulling trucks spewing so much smoke. It’s not needed for power, but it can make the overall boost double or even triple!

The return line, which is one piece and runs along the entire group of the injectors, was taken off next.

There are a number of different ways to remove the actual injectors, which are press-fitted into the cylinder head. Quezada used a simple and well-used $30 injector puller to do the job. The valve covers were removed for an unrelated head-bolt retorquing article (See Diesel World’s Feb. 2019 issue)

Once the injector is loosened, it can be pulled from the cylinder head. It may look grimy, but this is a pretty normal look for a 270,000-mile injector that’s never been out of the head.

Our factory injectors would be replaced with a set of 5×0.018-inch injectors from Scheid Diesel. These injectors, depending on the pump flow and turbocharger, are commonly used in 500 to 1,000-hp applications.

There are two sets of washers that were included with Scheid’s injectors. The thinner washers allow the injector to protrude further in the cylinder, allowing for more timing, while the thicker washers are for stock-type setups. Since we’d be bumping the timing in the future, we opted for the thin ones.

After some quick cleaning of the head, the Scheid injectors were installed and torqued down into the head.

New copper washers were included for everything, including the return lines.

Installation

The installation of the injectors is pretty straightforward, with an injector puller being the only specialty tool that was needed. Scheid also included new copper washers for the injectors and the return lines that would prevent leaks. The new injectors went in just like the old ones came out, and after leaving a couple injector lines loose on the truck, it fired right up. Right away there was a noticeable difference in power (and smoke) and these injectors didn’t have much idle haze, which we were pleasantly surprised about. The dyno would tell the real story, however.

Dyno Testing

We decided to clamp off the line to the wastegate and run as much boost as possible to get as much power as we could out of the stock turbo. Boy was that a mistake! Since fuel drives boost, we rapidly were approaching the limits for a stock charger. For an HX35, 35psi is a decently safe amount, and 40 psi is pushing the limits. On the first dyno run, boost rocketed up and hit 43 psi by 2,000 rpm! We immediately lifted and hooked the wastegate back up for the remaining pulls. Even set at 19 psi, the drive pressure on the exhaust side would blow through the wastegate, and the truck ended up at 38 psi of boost at 3,000 rpm. Just about perfect. Our initial baseline with no fuel plate was a stronger-than-expected 231 rwhp, so we were curious to see just how much the injectors would pick up. Remember, no pump modifications, just injectors. Once the next run was complete the result was an unexpected 348rwhp, or a 117rwhp gain! Torque was also well up, from 505 lb-ft, to a whopping 761 lb-ft. That’s a 256 lb-ft gain!

What’s next

Scheid Diesel’s injectors were definitely a good start, but we’re still on the hunt for more power. We’re looking at testing the limits of the stock turbocharger and 160 hp pump before we graduate to bigger and better parts, and we’ll also need to do some more engine upgrades (like head studs). We’ll also take the truck down the quarter with the factory ‘charger to see where we’re at. Keep checking back, because there’s definitely more to come!

The injector return line is a common source for leaks, so Quezada was careful not to over-tighten or cross-thread anything when installing it.

Next, the stock injection lines went back on. There are larger lines available, which we’ll be using when we switch to a 13mm injection pump.

The intake horn and boots went back on, and we were almost ready to fire up!

When first starting the truck, the injector lines must be loosened slightly in order to let any air out of the system.

Once the truck was fired up, boy what a difference! The Dodge picked up 117 hp and 256 lb-ft at the rear wheels, going from 231rwhp to 348rwhp, and 505 lb-ft to 761 lb-ft. Soon we’ll be adding timing and a lift pump, which should bump up the power even more.

Injectors for all!
While we’re using Scheid Diesel injectors on a P-pump 12v, that’s not their only set of injectors. Scheid makes injectors for everything from Bosch VE-pump Cummins engines, to common-rails, to mammoth DT466-based 5×0.039-inch (not for street use) pulling injectors. If you need stockers or 500-hp over swamp drainers, Scheid has it.

SOURCES

Brown’s Diesel
559.867.1111
BrownsDiesel.com

Scheid Diesel
812.466.7202
ScheidDiesel.com

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Surajpal Singh Bisht

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