real time dyno?

[wmcgonegal at rr.etc.ncr.doe.ca]

>> > The strain gauge on the driveshaft sure seems like a interesting 
>> >way 

>You're torque will always be low unless you calc in all your masses 
>and wind resistance and frictions and try to calc out the lost 
>torque.
>As well as try to get a repeatable condition.  Up hill, down hill, up 
>wind, down wind, etc. etc. etc.

If you can manage to put a strain gage on you drive shaft and get it 
calibrated, you do not need to consider wind resistance, tire losses 
etc., if you are only concerned with power output from the 
transmission.  This value should not be much less then engine power 
output on a vehicle equipped with a standard transmission.  You will 
always be able to read the power being transmitted to the axle uphill, 
downhill, accelerating, steady state on windy or calm days.  Of 
course, constructing and calibrating such a monster is not a trivial 
task.

To measure acceleration is much easier, but then you must consider all 
the above mentioned power losses to get the actual engine power.  Most 
of the aerodynamic and friction losses can be determined by coasting 
in neutral and measuring deceleration.  Occasionally we have to do 
this type of coast down measurement when setting up vehicle road load  
for emissions testing on the chassis dynamometers.

It may take a while to find that perfect, straight, flat, secluded 
stretch of pavement to do acceleration/power measurements.  But maybe 
you just want to know if you can accelerate faster down the same 
stretch of road after a slight modification under similar weather 
conditions after installing a new performance part.  Sure better then 
the seatofthepantsometer.

Will McGonegal
Electrical Engineer
Mobile Sources Emissions Division
Environment Canada
wmcgonegal at rr.etc.ncr.doe.ca