Home brewed cheap Dyno

[Alain Marchildon]

At 08:56 AM 5/3/97 -0800, you wrote:
>

First I read all the posts for the past week and I understand the need for
comparing the runs on the same road and doing it both ways to remove the
wind factor and also keeping the speed down as to not have too much drag in
the calculation or do a cost down but you could also factor in the CX of
your car but this does not matter in my opinion since I want to know if
what I have done to my car was good or bad and when playing with EFI you
don't just want the peek HP of your car but you what it at different Rpm's.

I don't care if my car does 200 corrected Hp at 5500RPM but I do car if it
did  -15hp at 2000prm
-14hp at 2500prm
-13hp at 3000prm
-13hp at 3500prm
-10hp at 4000prm
on my last modification.

Is it not what we are all looking for? 
Net results and nor SAE corrected HP?????????????????//

>Seems to me that either you are missing some data here, or I am missing
>your point. 

Sure I am missing data actually there is no data in what I said I just thew
an idea up in the air obviously the data would have to be sorted out and
the formulas written.

>
>You have managed to acquire the vehicle speed, and the engine rpm. You
>have no data on the engine load.

Engine load could be calculated from the mass of the car and the accleration.

>
>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. 

I don't care for steep grades I will not attempt to test my car on a 10%
grade anyway.


>
>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 problem I suggest that you get the G-curve, I did a few years ago and it
is very well explained.
Or go and see Bruce Bowling's formulas on the web. 
>
>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. 
>
Exactly


>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 don't want max HP I want it at different rpm's and it is a lot easier to
get what you want in second gear in a standard trany.

>
>I have a need for a homebuilt dyno - so straighten me out if it's me
>that needs it!
>
>


// marchildon at usa.net                                            //
// Alain Marchildon                                              //