Some three years and 50,000 miles ago, we installed some performance improvements from BD Power on our '01 Chevrolet Duramax test truck (June '03). Nearly all the mileage this truck gets is towing. Going down the highway means 20,600 pounds-yep, a real load.
Just to refresh your memory, we had added the BD air-intake system and a complete exhaust system, which we later found on a dyno to make about 20 more rear-wheel horsepower. We also opted for the BD exhaust brake, in which an air cylinder controls a butterfly valve, which, when activated, virtually shuts off the exhaust from escaping, thus building backpressure. It works so well when towing that only on the steepest grades do we ever touch the truck's brake pedal, and that's very seldom.
To keep track of engine performance, we mounted up BD's excellent X Monitor gauge package to the window's A-pillar to give us exhaust gas temperature (EGT), turbo boost pressure, and exhaust backpressure readouts.
Diesels thrive on fuel delivery. The more fuel delivered at the proper time, the more power developed. The installation of the Amp Box from BD allowed us to program four different power levels by altering the injection delivery timing and opening duration. Keep in mind that diesels operate without a butterfly-type throttle, so engine speed and power are regulated by the amount of fuel delivered to the injectors, and with a turbocharger, airflow is augmented by how hard the turbo spins due to exhaust flow. So it all comes down to more fuel, more air, more power.
The biggest drawback is that the program was designed for those trucks with the more common Allison automatic transmission, not the six-speed manual that we have. We leave our Amp Box set at the third power level and closely monitor our EGT. To change the power level, we have to locate an Allison transmission-equipped truck, plug in our Amp Box, and follow the instructions. OK, it's only a 20-minute job, but it's still a pain to locate another truck.
First, the Good ...
Thanks to BD, where driving conditions allow, we can cruise at 75 mph. While we can now usually pull most grades in Sixth gear, we'll grab Fifth gear even if not needed, just to reduce the gear and clutch load.
The power gain is phenomenal! Forget about the slow lane on the hills. The only problem is that we have to monitor our exhaust temperature and usually have to back off on long grades to prevent turbo meltdown. But even at reduced throttle, we're towing faster than most people drive without trailers. If we had the Amp Box set on "1," as BD recommends when towing, then we most likely could keep our foot down, but naturally with less power.
As to the air filter and exhaust, there is a slight increase in engine intake and exhaust noise. BD claims the two let the turbo run cooler and enhance the power output provided by the Amp Box. While I can't directly prove it, I'd have to agree.The best fuel mileage has been 22 mpg without a load, and our pulling average is 12.3 mpg. Not bad considering the speed, weight, and wind resistance involved.