does the G-Tech work to measure horsepower?
Here's my few cents worth;
The G-tech can't replace a good dyno for tuning. A good tuning dyno is able to provide a steady load on the vehicle and then hold that load anyplace in the powerband. Many dynos are not good dynos and provide the same info you can get from the G-tech.
Many Dynos are simply large rollers of a known mass connected to a computer. Your truck applies maximum power to the rollers and the computer measures how quickly your truck accelerated these rollers. The computer also keeps track of your RPMs so it can tell where, in the power band, the most rapid acceleration took place. How quickly did your truck accelerate these rollers of a known mass (weight)? That's how much torque you truck produced at full throttle, your hoursepower is then
calculated. These dynos can't apply a specific load at a specific engine speed for real time tuning.
The G-Tech is very similar to this type of Dyno. By using a very sensitive accelerometer it also measures how quickly you accelerate a known mass (the weight of your truck, you need to weigh your truck with you in it). It also keeps track of your RPMs so it knows where, in the power band, the most acceleration and torque took place. Your horsepower is then
calculated.
Both of these are only useful for getting a baseline and comparing the changes a modification made. Both can give you a printout of your torque and HP curves.
The big difference is the controlled environment the dyno lives in. The G-tech instrument itself is very accurate and repeatable. In order for the G-tech to be useful you need to control the environment as much as possible. Use the same stretch of road each time. Make a run in each direction, average the readings to cancell out the uphill/downhill variable. Keep the weight of the truck the same. Try for similar weather conditions.
The G-tech is likely to give you a lower power reading because it also has to deal with wind resistance and rolling resistance which aren't present with a dyno. It's like combining a dyno and a drag strip.
The downside of the G-tech is the environmental variable. The upside is it's yours to use as often as you want. It will be at least as accurate as a run at the drag stip in comparing vehicle modifications. Combine it with a data logger such as EFIlive and you will get a ton of real world tuning information whenever you want.
kw