14 hp increase from a driveshaft swap

[Tmoose]

undoubtably an inertia dyno

http://www.coastdriveline.com/NEW_Mustang.htm

http://www.coastdriveline.com/Press...DriveShaft/Images/HiRes/MustangDyno_HiRes.jpg

The hi res hp/torque chart confused me. the HP and torque scales are shifted. The displayed values near 2500 rpm indicate a 30 lb-ft increase (the ad only takes credit for 16), and a 14-ish Horse Pressure increase, which is correct for 2500 rpm. That "torque increase" amounts to about 10%, so my first thought was the original 2 piece steel driveshaft inertia represents about 20% of the driveline inertia. I've started wondering if maybe an aluminum flywheel was added between dyno runs too

 

[evelrod]

I have a goodly number of dyno runs on my cars over the years. You really gotta be careful what you read into these graphs. I don't see accel rates in there either.
In my experience, lightening up the the rotating mass of the power train did not get me a lot of extra hp and tq, but sure made a big difference in accel and decel rates, big time.

As an aside, our Lotus Cortina came OEM with a two piece. I switched to a single and after only a few races switched back because of accelerated front 'U' joint wear. Never saw any change in power on the chassis dyno...NONE!

Rod

 

[Tmoose]

I would not expect any HP difference on a proper absorption type dyno. I actually think somebody may have been fibbing a little bit to the inertia dyno to get the results posted.

now I'm daydreaming about what might have contributed about your front U-joint wear

 

[evelrod]

I raced that car for 28 years and never had a front joint failure, outright. Normal replacement every twenty or so races, that's all. The one piece Cortina GT prop shaft failed within three or four races. I still have the original two piece, it's in a Toyota Corolla 2TC/Ford gearbox/Ford rear end. It has always been normal to replace the rear joint after only a few races, but never the front. I never dwelled on the why, I just went back to 'tried/true'.

Rod

 

[IceStationZebra]

In a steady state condition or absorption type dyno I would expect to see a VERY small difference due to the added bearing and CV joint friction.

ISZ