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Diesel Tech Questions

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

Jason Sands
Aug 2, 2015
Photographers: Courtesy of Manufacturers
Programmer Request
I have a '13 Mercedes GLK 250 diesel, and I'm wondering if there is a suitable tuner available for this model. Thank you for your help.
Pat Carroll
Kamloops, British Columbia, Canada
There are actually a few options for your Mercedes, although using one might take a bit of out-of-the-box thinking. In the United States, there are very few tuners available for the Mercedes GLK. And finding something for a vehicle as new as a '13 model is also a challenge, thanks to advanced electronics, DPFs, and urea injection. But it's not hopeless. Being from Canada, your 'Benz's ECU might not be the same spec as the U.S. models, so there's a chance pressure boxes such as those from Brabus (brabus-usa.com) or Burger Motorsports (burgertuning.com) will work. These pressure boxes raise injection pressure, which adds fuel and increases power. If you do decide to go the electronic route, we strongly recommend calling around to make sure these boxes are compatible with your year, make, and model.
Photo 2/4   |   Water-methanol injection is an easy way to raise the power level of any diesel engine. The methanol burns as extra fuel, which makes power, while the water mixture (normally about 50 percent) helps resist pre-ignition. Normal power gains are anywhere from 25 to 100 hp, depending on engine size and application.
If you don't want to manipulate the engine-management system, water-methanol injection or nitrous oxide can also add power to your diesel, independent of any computer tinkering. Although we've seen gains from nitrous, for a mild application such as yours, we suggest you go with water-methanol injection. The mixture will help increase power and control detonation. In some cases, it may even reduce diesel smoke and actually improve emissions levels.
VP44 or P-Pump?
I want to know whether buying a truck with a P-pumped, 12-valve Cummins engine would be a wiser, more reliable choice than going with a VP44-pumped 24-valve. I will be living in Mexico where diesel is of lower quality and parts are harder to come by. Is one more reliable than the other?
Spencer Ross
San Diego, California
If you're going to be running questionable fuel, looking at an older diesel is a good choice. By the time you replace the pump, injectors, lines, and everything else, a common-rail-injected diesel can be anywhere from 5 to 10 times as expensive as a mechanical one. Either a '94-to-'98 12-valve or '98- to-'02 24-valve Dodge Ram will be able to run on today's modern low-sulfur, high-sulfur, or even somewhat contaminated diesel fuels. Still, both the 12-valve and 24-valve trucks have problems that need to be addressed before going off to Mexico.
Photo 3/4   |   Industrial Injection is one of the best known suppliers for replacement VP44 injection pumps, which are available in either stock or hot-rodded versions.
We've heard tales of 12-valves running on everything from used motor oil to transmission fluid for years, so the 12-valve's injection system is pretty forgiving. What does need to be addressed on these engines is a problem known as "the killer dowel pin." Inside the front gearcase on a 12-valve is a locating pin that goes into the block. Over many years, this pin can work itself loose and fall into the engine's geartrain. Since the pin is steel, it often gets shot right through the aluminum gearcase by one of the engine's drive gears, which will create a huge oil leak. In rare cases, the pin can even jam the engine's gear drive system, resulting in huge amounts of damage. Either way, the killer dowel pin is definitely a reliability issue you should address before heading off to Mexico.
With or without lower quality fuel, injection pump failure is relatively common for the 24-valve engines in '98 1/2-to-'02 Dodge Rams. Injection pumps for these trucks aren't cheap (around $1,200, plus labor), but they are plentiful, thanks to the VP44's high failure rates. These pumps usually last around 150,000 miles or more before they die, so many VP44-equipped trucks have already had their pumps replaced and should be good for another 150,000 miles or more.
Whichever route you decide to go (12-valve or 24-valve), you're probably choosing two of the more reliable diesels out there, and either choice should suit you fine when you're across the border. You might also want to consider adding a good fuel filtration system to whichever truck you buy to protect your investment against possible contaminants that may be in the diesel you use over there.
Bring on the Torque!
I have an '04 GMC 2500HD with the Duramax LB7 engine. I would like to pick your brain about what would be the best and most reliable way to squeeze more torque out of the engine. I'm not craving horsepower, I'm in it for torque because I pull a 35-foot camper a lot. My truck now is completely stock and has 149,000 miles on it.
Eli Lawson
via email
When discussing horsepower and torque, one of the first things to keep in mind is they're both closely associated with each other, probably more than one would think. Horsepower and torque curves will always cross (the numbers will be the same) at 5,252 rpm. The reason diesels have such high torque numbers is because they'll rarely reach this engine speed. In fact, they usually make peak power at around 2,500 to 3,500 rpm, which means the engine's torque-to-horsepower ratio would be nearly two to one.
Photo 4/4   |   If you're the type of person who wants to be fast and legal, Banks Power offers a full line of Duramax products that are 50-state legal yet can still add more than 100 hp at the wheels on certain applications.
Fortunately, the way diesel engines operate makes it very easy to increase torque in most cases, simply by turning up the fuel. Adding fuel not only increases power, it also spools the turbocharger at a quicker rate, again, raising the torque. In factory form, an LB7-powered truck makes roughly 250 rwhp and 510 lb-ft of torque, which are values that can easily be bumped up with a tuner. Even in emissions-overconscious California, there are tuners for LB7s that can add more than 100 hp and 200 lb-ft of torque, which should give you that torque boost you're looking for.
If you're in an area with relaxed emissions laws, or if you own an engine-swapped truck or a competition vehicle, max-effort race tunes of up to 490 rwhp and more than 900 lb-ft of torque can be installed. At this point, the truck's stock fuel system, turbocharger, and transmission will all be tapped out (oddly enough, all at about the same point), and they'll need to be upgraded. So, whether you decide on just a mild programmer or an all-out power tune, adding an extra 200 to 400 lb-ft of torque to your Duramax should be no problem.

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