Reading Dyno Printouts?

[Vipera Russelli]

Can anyone explain why it is often the case on before-and-after dyno printouts (before and after a performance modification, that is) that the “after” hp and tq curves seem to begin to print out to the right (higher rpms) of the “before” curves? Because many modifications to increase high end horsepower cause a decrease in low end torque, I would really like to see what’s going on at these lower rpms and can't figure out why in some cases the dyno printout doesn't indicate as much.

See, for example:

http://www.heffnersperformance.com/650%20dyno%20sheet.html

 

[opnwide]

I haven't really noticed such a shift. I'm sure it does occur, but probably under 3000rpms with most typical bolt ons. My dyno guy starts the run at 2500. Even when I put Bellangers on my 95, I saw a torque increase at 3000 (about 5ftlbs). At 1500-2000 rpms, it probably would've been different.
Plug a vec 2 into your car and see if you still see that shift. I doubt it. The vec I was famous for pumping up torque, and the vec2 should be even better.

 

[Jack B]

It just matters where he hit the throttle and when he engaged the computer. Another little trick is the torque, I can increase the torque approximately 50-75 ft-lbs when on the bottle by just starting the pull at 2300-2500, instead of my normal 3000