A while back extensive tests were done with the same vehicle on 7 different types of chassis dynos. And They varied By a 33% in HP from the lowest to the highest Readings.
Also Tests were done on an engine from fly wheel dyno to chassis dyno and the engine lost a supersizing 106 hp, which is a loss of 40 percent between the engine dyno and the chassis! but overall the engine suffered from an average loss of over 36 percent across the powerband from 4,000 to 5,500 rpm
Test:
Small-block Ford 357 ci in a ’63 Mercury Comet with an AOD automatic, a 9-inch rear, and a 3.50 gear.
Difference
Flywheel Power....rear Wheel...loss..%loss. HPloss w/o fan
RPM......... TQ HP TQ HP -HP -HP% -HP -HP%
2,500 384 183 - - - -
3,000 410 234 - - - -
3,500 420 280 270 180 -100 -26 - -
4,000 426 325 304 230 -95 -41 85 37
4,500 413 353 297 254 -99 -39 83 32
5,000 389 371 277 265 -106 -40 88 33
5,500 344 361 254 266 -95 -36 76 29
Avg. rear wheel loss 99 hp 36.4% and running without the fan 83 hp loss 32.7% A 19 HP gain from just removing the fan!!
This test was repeated with other engines and the average loss was 40 % through the accessory's and drive line I did these tests on my own but never got 40% the Highest on my equipment was closer to 30% always pretty close to 30 % about 1/3 and that's what I subtract from an engine dyno sheet I read any more 1/3 when converting to rear wheel HP!! Also a change to low OHM plug wires over from High OHM made gains of 10 to 20 HP The Packard gold strand and copper core wires gained over 25 HP, Copper core non resistor pluge more then 5 HP gain, Putting a shut off switch on the alternator for racing gained up to 10 HP, Thinner oil had significant gains, These guys with 100 pound oil pressure readings are losing gobs of HP and Torque, Change the pressure spring to 40 Lbs and gain back that HP and torque their throwing away, 50 WT. oil to 30WT. another big gain! 50 wt off road oil isn't needed in a drag car many only run 5 wt.!! ETC, ETC,
I'm not suggesting any one change what works for them , just pointing out a few things that bring back lost HP and Torque:thumbup: A clutch fan will only consume about 5 HP even a flex fan uses more then that! Most of these gains mean nothing on the street but at the drags 10 HP or 15 LBs torque could be your edge !
Jester (Chris)
That test I posted looks great on the edit page and my original post before being sent but looks like crap on the thread its all mashed together and will be hard to read
:drunk:
Sorry for that