Hey guys,

I went to a shop the other day and had my car put up on a chassis dyno. Now, I was suprised at the horsepower I was putting to the wheels, as in...severely disappointedly suprised...until I accounted for drive train loss and altitude (4500 feet here).

The tech told me that it's ideal to test the car in it's 1:1 gear since the lower gears have different gear ratios thus slightly different readings but since it was an automatic, they can't really do that becuase the car will shift down to 3rd when you put it to the floor (Or first from second as I found out). So we did it in first gear and then second... where it shifted when it hit near 4500rpm.

Anyway, in first gear I ran 92ft-lbs of torque an 114hp at 4250 RPM. IN second gear I ran 100hp and 125 ft-lbs of torque. I also found that my car stops revving at about 5400rpm...it just won't go any higher but it doesn't die either (such as if I had a rev limiter or hit valve float)..it just simply wouldn't go any higher.

If you account for about 20% altitude loss and another 25% of drive train loss, that puts me somewhere in the 170HP range...with my headers and new ignition, not bad for a 305 H.O. with 120k miles on it that was originally rated at 190hp at the flywheel.

Still, it seems that I might have gotten a better reading had I been able to start it in "drive" without it shifting like I could if i had a manual. do you guys know any way to do that or is there another way to dyno the car that I'm not aware of? Thanks in advance for any help!

 

Take off the TV cable and clamp it 1/2 way out with a vice grip. This will increase the line pressure so the transmission does not burn up and it will not down shift once it gets into third gear. Put the shifter in third and increase speed at light throttle until the car shifts into third gear. Then slow it down to the rpm where you want to start testing and floor it. It will pull through third gear without down shifting and it will give you good readings.