I bought one of these on eBay for $120 shipped. I like it! I used it to measure my HP. Using G-Techs recommended weight estimation by subtracting 180 lbs for each of the 5 possible passengers from the GVWR I got 3,410 lbs. I then weighed my car at a local truck-stop weigh station and got exactly 3,400 lbs. Not a bad estimation! So when I did my 5 runs I just added my 195 lbs weight to the car's weight.

Temperature was 62-72 degrees and I used a variety of road surfaces that appeared flat. Later, I'll try doing consecutive runs on the same stretch of road.

My results were 164, 162, 160, 157, 154, and 157. If I discard the highest and lowest and then averaged the other 4 then my average HP is 159. Keep in mind that this is "true" delivered HP, not crank or even dyno HP. It takes into account wind resistance, etc.

Does this sound right to all you knowledgeable people out there? Is there any formula to calculate wind resistance? If not, no big deal. My main use for this is to measure HP before and after mods. If I can get off my lazy butt and put my stock airbox on again, I'll do some more runs. Then I can put on my Cattman Y-Pipe that's sitting in my garage.

Tony

 

Doesnt that thing get thrown off by little bumps in the road?

 

I don't know.

Tony

 

It does.



I found my G-tech HP #'s to be drasticly different on different days. However on the first day it was dead on. It said I had 218HP, I went to a real dyno a few days before and had 215 WHP. A few days later it said I only had 180 HP though

 

One of the things to keep in mind is that the cord might be bouncing around, which makes the actual unit bounce up and down. This is why I did several runs and will mess around a little more before I take the results to heart.

Tony

 

As long as you can get it to read consistantly, then you can measure relative gains. Say you are consistantly reading ~158, then you put on a mod and are now getting consistantly ~165, then you can safely assume you are getting more power from it. But if it's all over the place too much, then you may be screwed.

 

Just did another run today in 75 degrees. 158 HP. BTW...another thing to consider...automatics are more consistent than manuals. You 5 and 6 speed guys might be getting different readings from inconsistent launches. Just an idea.

Tony