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April 2015 Top Diesel Tech Questions

You've got questions? We've got answers!

Jason Sands
Mar 20, 2015
Photographers: Jason Sands
Welcome to Top Tech Questions. One of our favorite forms of reader communication is tech questions. Our Top Tech section is a place where you ask what’s on your mind, and we answer. Send us an email at dieselpowertech@enthusiastnetwork.comand ask away!
Question: One Headlight, What Gives?
Question: My son gets your magazine, and I have a question about some photos you’ve run. I’ve seen more than one truck with its headlight missing, and I’ve wondered why that is. It’s not something I normally see when driving down the street, so I was just a little puzzled.
Cathy Hauer
Waucoma, Iowa
Photo 2/4   |   Removing the headlight in order to draw fresh air from outside the truck is a trick that’s most often seen on sled pullers or drag racers, but rarely on trucks with license plates.
Answer: If you’re looking for a common thread between the missing-headlight trucks, we’re willing to bet that most of them are on the dragstrip or on a sled-pulling track. During competition, engines can get very hot, and they create a lot of underhood heat. The goal is to direct outside air into the turbocharger, as cooler, denser air will almost always help make more power and lead to cooler exhaust gas temperatures. One of the easiest ways to accomplish this is to remove a headlight on one side and duct outside air into the turbocharger.
Now, you may be wondering, does this really work? After all, how much of a difference can a few degrees make? Well, we’ve actually had some experience on a chassis dyno with the only variable being air temperature. One run was made during the heat of a summer day, when it was about 95 degrees outside, and the truck registered 540 hp. The truck was left on the dyno untouched overnight, and another run was made when the ambient temperature was about 60 degrees. With no other changes, the truck responded with 564 hp, a 24hp increase. While the difference in our case was ambient air temperature, the difference between underhood temps and outside temperatures can easily be 20 degrees or more. In addition to that difference, having a forward-facing inlet for the turbo can also create a ram-air effect at speed. At 100 mph or more, even a 1-psi gain (pre-turbo) can lead to 3 to 5 psi more boost going into the engine, which will again lead to more power.
One thing to remember, however, is having this type of ram-air setup without an air filter (which is most of them), can lead to disastrous results if something enters the turbocharger. We’ve seen chunks of dirt, rocks, or parts get scooped up by an air inlet and destroy very expensive turbochargers. In the end, while this modification is good for track use, we definitely wouldn’t recommend it for the street.
More Power Stroke Swaps!
Question: It seems like whenever I see a diesel swap, it’s always a Cummins engine. Surely, there are other options out there, even older mechanical ones. Why don’t we see more Power Stroke swaps?
Ryan Jones
Las Vegas, Nevada
Photo 3/4   |   We saw this cool Power Stroke-equipped Lightning at the NHRDA World Finals in Ennis, Texas. The Lightning was running in the 11.90 Index Class, although it has been much faster with the aid of some nitrous.
Answer: There’s no denying it, the Cummins 6BT is the small-block Chevy of the diesel universe, and it’s been installed in virtually everything—from passenger cars to monster trucks to rat rods. However, it’s not the only engine out there; Ford’s 7.3L Power Strokes don’t need all that much wiring to run, 6.0Ls are easy to find for cheap in semi-running condition, and 6.4Ls are absolute powerhouses when turned up.
The reason Cummins engines are chosen most of the time over these other powerplants is a matter of a few important factors. First, since most people opt for the extra power of a turbocharged diesel, the inline arrangement of the Cummins four- and six-cylinder engines make them very easy to plumb, turbo-wise. The “V” arrangement of engines like the Power Stroke means extra exhaust piping is necessary, as well as up-pipes that can be prone to exhaust leaks. And attempting to install one in a non-Ford truck can also present packaging issues. The fact that the turbo is in the valley on Power Stroke engines, and placed quite high, presents another difficulty to overcome. While the engine fits fine in a large truck, trying to shoehorn everything into a smaller vehicle can cause instant hood clearance issues.
There’s also the matter of electronics. Even the 7.3L engines have electronic injectors and need computer tuning to run. And, as dealing with wiring isn’t typically a “desired” aspect of engine swaps, trying to install a 6.0L or 6.4L could become extremely frustrating (there are a lot more sensors, sending units, and wires associated with these engines).
There are a few folks we know of who are working on some pretty serious swaps. There’s a few 6.4L-powered rigs in the works, and one enthusiast who’s building a very serious Mustang and has gotten around wiring challenges by installing an eight-cylinder (mechanical) P-pump on the engine. As older Ford trucks become more affordable thanks to rust, wrecks, and mishaps, we wouldn’t be surprised to see the number of Power Stroke swaps on the rise.
OBS Ford Heating Up
Question: I have a ’95 Power Stroke-powered Ford F-250, and I am looking at keeping my exhaust gas temperature a little cooler while towing. The truck is non-intercooled, so I know adding an intercooler will help, but I was also looking at water injection. Any advice on which one I should buy, or should I do both?
Ryan Gauge
Princeton, California
Photo 4/4   |   While air-to-water intercoolers are often seen in high-horsepower sled pullers, smaller versions from companies like Frozen Boost can easily be adapted to older non-intercooled trucks.
Answer: The water injection versus intercooling debate has been going on for some time now, in virtually all aspects of diesel performance, from towing to racing. We’ll concentrate on your particular application, however, which, since it is older, was non-intercooled from the factory.
For starters, an intercooler should definitely help, as there’s a reason why virtually every modern diesel has one. Cooler air in the engine means lower exhaust gas temperatures, and in non-intercooled towing situations, air temperatures can reach 300 degrees or more. An intercooler will drop these temps to a mellow 100 to 150 degrees, which helps keep the engine happy under load.
Water injection also takes heat out of an incoming air charge, but instead of heat dissipation, it relies on the phase change of water that’s superheated to remove heat from the air. One thing water injection can do that intercooling can’t is add power by itself, as mixing 20 to 50 percent methanol in the water can result in a nice 30 to 50hp increase, without having to upgrade the turbocharger, programming, or injectors. The downside to water injection is that a lot of water has to be injected in applications of even 300 to 400 hp to keep things cool.
For the do-it-yourself kind of guy, either water injection or intercooler systems can be made, and plenty of early Ford owners have adapted eBay intercoolers and later Super Duty intercoolers to their early trucks. If you’re considering buying something, however, intercooler kits for the older Fords are very hard to find. In fact, Banks Power and Hypermax are virtually the only companies we know of that still advertise them. If you’re just concerned with exhaust gas temperature, we’d say go the intercooler route. If you’re looking for a bit of extra power, too, water-methanol might not be a bad idea. Either way, your truck will definitely be ready for increased performance, if you ever decide to upgrade it further.