Way to measure HP?

[Rob O]

I think through thorough dyno testing, VE compensation, etc... you could
come up with a reasonably close approximation based upon airflow.
Problem is, as you change something your compensation tables would have
to change and your results would get thrown off.

If you only want to do an A/B comparison you can record the number of
pulses from a cam or crank sensor (or an ABS wheel sensor or...) and
graph them against time. By keeping variables such as temperature,
degree of road inclination, etc... relatively constant you can determine
if the latest mod has increased the ability of the engine to accelerate
and know if your changes have been successful. 

There is a relatively inexpensive program (I think it's called road
dyno) that does just this and I can see it being a useful tool in the
same way a G-tech Pro is. You can't really expect exact accuracy from it
but if it is repeatable and consistent then you have a method of
comparison without spending the $$$ for time on a chassis dyno (which is
not exactly the most accurate thing anyway).

I guess I kinda wandered away from your original goal of instantaneous
HP readings but while that would be something "neat" to show off, has
limited usefulness for someone like me who's more concerned with getting
from point A to point B the quickest

Rob_O

Darryl & Karen Smith wrote:
> 
> ----- Original Message -----
> From: Bruce Plecan <nacelp at bright.net>
> To: <diy_efi at diy-efi.org>
> Sent: Saturday, December 09, 2000 10:55 AM
> Subject: Re: Way to measure HP?
> 
> >
> >
> > > How accurate would it be to measure the output voltage of
> > > a 0-5v MAF sensor to estimate engine HP output?
> > > Is HP going to be directly proportional to the airflow into
> > > the engine?  It seems that it would be.  Logging MAF voltage
> > > then would give you HP at any given moment, and if you logged
> > > rpm as well, it could give you both the HP and torque curves.
> >
> > .75 grams/sec.= 1 SAE HP when tuned *Precisely*
> >  calulated HP has never run a race.
> >
> > > You'd likely need to do a dyno run to calibrate the MAF
> > > readings, but once done, you could do a run on the street or
> > > highway anytime you want to check results of modifications.
> > > Do you guys think this would be very accurate?
> >
> > Again, all about the state of tune.
> > If you were using a WB and knew that you were in the nieghbor hood of
> > 12ish:1 then would be a fair guess, but why bother?.
> > Like I said calculated HP is an Ego issue.
> > Good for bench racing, and saying my dog is bigger then your dog.  that's
> > about all.
> > Bruce
> > >
> Also depends on the engine type,  some engines are more efficient at
> producing work from a given amount of mixture, compression, rod length, bore
> and stroke ratio,et al, all are variables to confuse the issue.
> 
> Darryl
> > > thanks
> > >
> > > --Dan
> > > houlster at inficad.com
> >
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