In July of 2012 I bought a 2004 Chevrolet Tahoe to take to school with me at the University of Pittsburgh. I chose this vehicle for many reasons, mainly because the Tahoe that my dad bought new in 1999 hasn’t let him down in the 15 years he’s owned it. This new(er) Tahoe carries my friends and our gear, moved me from Denver to Pittsburgh (including all of my desks, chairs, bedding, bike, etc) in one trip, and thanks to the Z71 Off-Road Package can tackle the rough terrain of the Rocky Mountains when I’m home for the summer. This truck has it all: luxury, comfort, a big American V8 engine, and more than enough space to carry whatever I need (including 10 of my teammates).
Over the last two years, I’ve made a few changes to the vehicle that I’ve christened “Dallas” (due to the sticker on the inside of the driver door that says “Made in Texas, by Texans”). My personalizations include a set of bold black MB wheels, thick and meaty BF Goodrich off-road tires, and a bangin’ stereo with Bluetooth and a backup camera so that I can parallel park this beast on the narrow streets of Pittsburgh. Dallas was also much too quiet for my taste, so I threw an Aero Turbine performance muffler on it and as a result it’s now more effective to rev my engine than to honk my horn at pedestrians and other vehicles.
Eventually I decided what every 20 year old decides about his truck: it’s not fast enough. I’d already added a K&N cold air intake system, but the gains were hardly noticeable- Dallas still felt like a 5200 pound dinosaur lumbering about. After losing enough stoplight drag races to pretty much everything, I got serious about performance gains and decided that short of a supercharger (which is way out of a college student’s budget), a performance tune was the best money I could spend to get some more power out of the vehicle.
“Tuning” refers to altering the settings in a vehicle’s PCM (performance control module). The PCM is the main computer that receives input from many different sources and controls most functions on a vehicle. Vehicles come from the factory tailored with the settings that the manufacturer believes will satisfy the largest amount of people. This means that compromises have to be made in some areas so that others can improve, and as a result no one area is the best that it can be.
An example of this is GM’s torque management system, which reduces engine power during gear shifting in order to improve shift smoothness (more on this later). The main reason for tuning a vehicle is that you, as the owner, can decide which of these settings you want reduced, increased, eliminated altogether, and generally altered in order to maximize others on the car. Some prefer to maximize gas mileage, some to maximize power, and some a mix, but overall a tune improves all aspects of a vehicle.
In September, I found a company online by the name of Black Bear Performance. They’re a small company that offers in-person and mail order tuning services for GM vehicles that is well known and respected within the GM community. They travel around the country to places where there is high demand for their service, and Pittsburgh was due for a visit in April. As a serious car guy, I buy only the best for my vehicle and since I could not find a single negative review of Black Bear’s services, I decided to put down a deposit.
Over the winter I compiled a list of specific changes that I wanted Black Bear to make to my vehicle beyond their standard list of improvements. These included adjusting the throttle sensitivity, top speed limiter, and coasting more when going down hills.
When the day finally arrived, I met with a man named Justin at a place just north of the city. After introductions, he plugged his computer into my OBD II port and asked me what modifications I’d made to the truck. He could tell from his computer that Dallas hadn’t adjusted to the amount of air that the new intake was bringing in, and he made adjustments to the air flow sensor accordingly. This is one reason that in-person tuning services are vastly superior to off-the-shelf handheld tuners: traditional handheld tuners contain very general modifications designed to apply to a wide variety of vehicles, whereas Justin gathered data from my specific vehicle and made changes accordingly.
We drove around for a bit so that he could gather more data and determine my driving style. Every now and then we would pull over so that he could make changes on his computer, reset the truck’s computer to apply the changes, and start driving again so that I could decide whether or not I liked what he’d done. The entire process took about 45 minutes, and after all was said and done, it felt like I was driving an entirely different vehicle.
Justin tuned the vehicle for 93 octane gas and claimed that I’d gained about 25 horsepower, and you know what? I believe him. Before the tune, shift points at full throttle were set at about 5200 RPM, well below the truck’s 6000 RPM redline. They were set this way for safety and engine/transmission longevity, but at the sacrifice of speed and passing power. Justin raised my shift points to 5900 RPM so that I can stay in a lower gear and be in the power band for longer, meaning I’ll go faster. Since this will be my vehicle for the next ten years, Justin promised me that as long as I don’t hammer the throttle every time I accelerate, the longevity will not be affected.
There is another exciting result of higher shift points: highway passing power. Stoplight drag races are a lot of fun, but the average driver needs to accelerate quickly in the 45-75 range much more often than they do from a dead stop. Before the tune, if I punched the throttle going 75, the truck would shift down into third and slowly attempt to accelerate, but it would take a long time to pass a car because the RPM’s were too low to give enough passing power but too high for the computer to allow a shift into second.
With Justin’s adjustments, it now quickly shifts down to second, roars up to 5000 RPM, and flies by whatever vehicle is in my way (usually a Prius). This change actually saved me from an accident with a merging semi-truck on my drive home from Pittsburgh: stock Dallas wouldn’t have been able to get out of the way in time, but tuned Dallas accelerated past the truck that was invading my lane just in time to avoid an accident.
Justin reconfigured my air flow sensor so I gained even more power from the cold air intake that I thought I’d wasted money on. GM’s “abuse mode,” which doesn’t allow full engine power and reduces torque until roughly 2000 RPM, was completely removed, giving me more power off the line. My top speed limiter was also raised from 99 to 101. I didn’t completely remove the limiter because my tires are only rated for 99 mph and I don’t want the temptation of seeing how fast Dallas can truly go, but c’mon, who wants to have to say that their truck tops out just before 100?
I also don’t regularly tow anything, so Justin made my tow/haul mode into a “sport mode,” an all out performance mode with redline shift points, maximum power, and all GM “nannies” removed. However, my favorite change has got to be the removal of the transmission torque management system that I mentioned earlier. The stock tuning caused the transmission to sort of “slide” into gear, making for extremely slow shifts and a terrible city driving experience. It also couldn’t really make up it’s mind on what gear it wanted (and it’s only a 4-speed transmission… come on, GM).
Justin removed 75% of the torque management in normal mode and 100% in sport mode, meaning that I lose almost no time when shifting gears. He also adjusted the transmission tables so that there is no more gear hunting. It now shifts extremely firmly, throwing my head back a little bit because of the power. He made the torque management variable, too, meaning that under light throttle there is a little more regulation so that Mom is not thrown about when driving around town, but under full throttle it excites and drives like a race car.
No longer is Dallas slow and unresponsive. It now moves forward with confidence and passes on the highway with ease. There is more power throughout the entire rev range and it is an absolute joy to drive. Before the tune, if I could get from a dead stop to 60 in under 10 seconds I was lucky. Now it takes about 8 seconds. I even average about 2 miles more per gallon going from 15 before the tune to 17 after, with a mix of city and highway driving. I averaged 18.7 on the highway drive from Denver to the TFL Test Track, which is phenomenal for a full size truck that predates cylinder deactivation.
The drive to Pittsburgh was 1501 miles with a 4000 foot drop in elevation and I averaged 60 mph and 15.2 MPG. The drive home was 1524 miles with a 4000 foot climb, but I averaged 65 mph (meaning more air resistance) and 15.8 MPG. On flat parts of the drive I averaged 18 MPG @ 75 mph, but extremely windy roads all the way through Iowa and Nebraska (that were not windy on the drive to school) brought my average down.
Overall I am thrilled with the changes that Justin made to my vehicle and I will have Black Bear tune every GM product I buy. The total cost was $300, and Justin assured me that the vehicle will last just as long and be just as reliable. For those that live in remote areas, Black Bear Performance does have a service where they will tune your vehicle via mail, but nothing compares to the in person tuning service because you can have Justin make real time changes. I highly recommend that those of you who have the ability take advantage of Justin’s service do so.
Now if you’ll excuse me, I’m off to go scare some hybrids with my loud exhaust…
