Quote:
Originally posted by southbeachmach1
I haven't gotten a clear answer on this yet.
Technically when you step up your gears from say 3.55 to 4.10's your putting more torque to the rear wheel right? So wouldn't that increase your torque and HP on the Dyno?
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HTH...
I found this on IMBOC.com;
QUESTION:
A car having 3:27 rear end gears is placed on a DynoJet chassis dyno and
has a dyno performed. Then this same car is taken off the DynoJet
chassis dyno and has the rear end gears changed to 4:10. The car is then
placed back on the DynoJet chassis dyno and another dyno is performed.
Will the second dyno show a loss of horse power caused by the 3:27 to
4:10 gear change?
ANSWER:
Yes. This has been a long standing debate among car enthusiast, so I
recently emailed DynoJet and asked this exact question. Below is the
response I received.
"The 4:10 gear will show less horsepower than the 3:27. The reason is
due to rate of acceleration changes. The rate of acceleration is quicker
with the 4:10 because of torque multiplication being increased to the
rear wheel. The horsepower will show less because the targeted RPM is
met before the horsepower has a chance to overcome the rotational mass
(dyno, drive line, etc.) or moment of inertia in speed. Because the
speed is decreased and the RPM is met faster, the horsepower never has a
chance to catch up with itself, so to speak. The overall ratio of 1:1
will always produce the most horsepower on the chassis dyno. Having said
this, a similar problem can occur with horsepower loss when the rear
gear is too high. The horsepower is being absorbed in just trying to
keep the rotational mass spinning. Please keep in mind that your
engine's horsepower never changes but what gets to the dyno or drive
surface does. If you have any further questions please don't hesitate to
ask. Thank you."