Have No Fear, The Tuning Is Here

Throwing some tuning at a 2008 Duramax LMM

Published in the August 2008 Issue August 2008 Duramax

Black Smoke-one of the driving forces behind the new emissions standards for all 2008 and newer diesel pickups. Just a year or two back the U.S. Government and EPA released the new diesel engine emissions standards and we all assumed it would be the end of diesel performance.

This feeling was much like back in the 70s when the switch to unleaded fuel and stricter emissions standards killed the "Muscle Car" era. Restrict what an engine can breathe in and breathe out and you're going to have some damaging effects on performance. That's all there is to it. After the first few years of the unleaded fuel fiasco, manufacturers and aftermarket companies began to find ways to make big power while still working within the EPA requirements.

Just like back then, it was only a matter of time until aftermarket companies would dissect the OEM computer boards and fuel mapping to find a way to increase performance while still abiding by the rules set by the anti-black smoke EPA. OEM manufacturers have hundreds of computer gurus working on factory tuning that can comply with EPA regulations. Thankfully for us, there are plenty of these same gurus out there interested in improving upon those factory settings-taking us to the place we all want to be-the land of more power.

Wanting to see how these "rebel" computer tuners were doing, we walked into Custom Auto of Idaho Falls, ID, to see just what could be done with tuning changes on a brand new, bone stock 2008 GM 6.6L Duramax LMM.

With the factory intake and exhaust and just a little more than 200 miles on the truck, we backed it up onto the rollers to make a few passes to get a good reliable stock figure. The factory settings produced a very respectable 276 hp and 521 ft-lbs. of torque. Not bad for a box stock pickup right off the showroom floor. Especially when you consider that a chipped 7.3L Power Stroke would just barely make those kind of numbers.

We got a hold of the newest Bully Dog PMT with tunes built specifically for the LMM, along with the latest version of PPE's Xcelerator Hot tuner and tested both on the same truck on the same dyno on the same day.

After making the runs in pure stock form with the truck still strapped on the dyno, the crew spent an hour or so installing the new PMT on the truck and uploaded the first and lowest tune. Bully Dog refers to it as a towing tune. After the upload was complete they fired the dyno back up and on the first run the truck gained an impressive 48 hp, peaking just over 324 hp to the wheels. Not bad. Most surprising of all is still no smoke, not even a haze before the turbo spooled up. The tailpipe is still as clean as it was the day it came home from the dealer. Guess that particulate filter really works.

After a few runs in the tow tune-all netting a consistent 318-324 hp-it was time to bump the PMT up one more step. Time for the economy tune, the highest tune offered on this version of the Bully Dog PMT. Custom Auto had this version before Bully Dog had completed its extreme program, which has since been released. With the economy program uploaded, the crew pulled the truck up to speed on the rollers and laid into it.

Still, with no smoke from the trumpet-looking pipe GM calls a tailpipe, it laid down 384 hp to the wheels on the first pass. That's 108 hp over stock. We lost the tach signal on the engine during the run so no torque readings were recorded. After readjusting the tach signal on the truck another pass was made, this time producing 373 hp and 672 ft-lbs. of torque. That's 97 hp and 151 ft-lbs. over stock, still using the factory exhaust and intake. And no smoke with safe egts.

After making a few runs with the Bully Dog tuning on the truck we took a lunch break, giving the truck proper time to cool down before we made the same tests with the PPE tuner installed. Once we got back to the shop we removed the Bully Dog tuning from the truck and uploaded the lowest PPE tune from the Xcelerator tuner.

The first run netted a peak of 318 hp but again our tach signal lost contact and no torque readings were collected. The truck sounded crisp and clean and the tuning feels to be spot on. We made two more passes in this tow tune, which PPE says is a 40 hp tune, which, according to our dyno numbers, is dead on.

We then cranked the chip up into the High Performance tune on the Xcelerator and after three passes, none of which recorded any torque, our highest run was 328 hp. Just 10 hp over the tow file. PPE claims this program to be a 90 hp tune, but our numbers were only showing around 50 hp.

Finally we cranked the chip up to its third setting, the Race Performance file. After two more runs on the rollers of the Superflow dyno, our peak number was 356 hp-80 hp over stock. That's not bad for just some minor computer tweaks. We didn't run any of the higher tunes on the tuner since the truck still has the stock intake and exhaust bolted on.

You should take into account that the PPE tuner has the ability to go much farther after some modifications are made to the factory intake and exhaust systems. We've heard through the grapevine that some have been well past 400 hp with this same tuner.

So what more could a guy ask for? It was just a matter of time until the aftermarket companies began unlocking the secrets these engines had hidden away behind all those emissions controls. These are just two examples of a couple of tuners on the market for these new emissions-friendly diesel pickups. Up to 380 hp with nothing more than a programming change is impressive.

We're more than pleased with where these engines can take us in the performance segment and we think there is plenty of potential there. Big power with the emissions controls still intact-the EPA hasn't killed diesel performance yet.

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