Home brewed cheap Dyno

eric schumacher e.schumacher at postoffice.worldnet.att.net
Sat May 3 18:55:30 GMT 1997


The load is the weight of the vehicle.  The rate at which it accelerates is
a indicator of power.  So with a know weight and known acceleration and
known RPM we can calcuate HP for a given set of onditions eg pitch of the
road, temperature, barometric pressure etc.

I like the tape recorder. wave file soundblaster thing very clever someone
out there.


>> After reviewing the home dyno software package available on the F-body list
>> it got me thinking that if you want an accurate home built dyno with the
>> least amount of money invested the best way to go would be similar to what
>> is already done but instead of calculating the vehicle speed with the trany
>> diff and tire ratios why not use the speed sensor that is buried the dash
>> of most modern cars, they give something like 2000 pulses at 60mi/h and
>> then get an inductive pickup to read the engine speed like the Dynojet
>> chassi dyno do except instead of reading the car speed they read the drum
>> speed.
>> The rest is pure math.
>> 
>> The home dyno records the pulse from the inductive pickup on a small plain
>> voice recorder and then feeds this to a sound blaster card to produce a
>> WAVE file then reads this file.
>> 
>> A stereo recorder could be used to record the inductive pickup and the
>> speed sensor one on the right channel and the other on the left to get two
>> distinctive pulse patterns and produce a WAVE file then read it and
>> calculate what we need to get car speed engine speed and the rest for HP
>> and torque.
>> 
>> Very cheep way to get a reliable chassi dyno.
>> Most of us have a inductive timing light, computer with sound blaster.
>> Only thing missing is a stereo tape recorder (a stereo camcorder would be
>> perfect)
>> And a few feet of cables and a few plugs and the big one the software to
>> convert the pulses in the WAVE file to readable format for you favorite
>> database program.
>> 
>> Any one interested in writing a simple bit of software to convert this?
>> 
>> // marchildon at usa.net                                            //
>> // Alain Marchildon                                              //
>
>Seems to me that either you are missing some data here, or I am missing
>your point. 
>
>You have managed to acquire the vehicle speed, and the engine rpm. You
>have no data on the engine load.
>
>To give an example - the objective is to calculate the power output of
>the engine, but it would be vastly different if we had 3000 RPM and 30
>MPH on the flat, versus the same numbers up a steep grade. 
>
>Some continuously variable transmissions might allow the calculation you
>want, if you had the proper torque/ratio curves, but I think that would
>be more complex than you had in mind...
>
>No way to assume it's flat, without detailed knowledge of the vehicle
>drag coeff. Of course you might get that by throwing the vehicle in
>neutral and recording how quickly you decelerate. 
>
>Our main interest is in Max HP - I'm having visions of a bizzare series
>of high speed accidents, that could wipe out the membership of this list
>;-)
>
>I have a need for a homebuilt dyno - so straighten me out if it's me
>that needs it!
>
Lotsa Luck Eric
85 GTI with VR6 power




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