All Members,
I like many others on this Forum have had our Cars Chassis Dynoed to see exactly what all those modifiations to our engines resulted in as far as gains. I like most was very disappointed at the results. (low numbers) I also assumed that the results were just a reality check Vs. Computer advertised ratings, part manufacturers, etc. After reading the acticles at the sites below, I am not so sure! Tell us what you think about what they are saying.
Dutch
http://www.pumaracing.co.uk/power3.htm
http://www.sdsefi.com/techdyno.htm

A chassis dyno is just another way of measuring horsepower and can't be compared to other types of dynos or evem another chassis dynos. You use a chassis dyno to evaluate the effects of tuning but you can only do that if you use that dyno and no others. To do otherwise invites invalid data. There are "conversion" formulas that people use to convert rearwheel horsepower to flywheel gross horsepower but to me, these formulas are little more than a way to take a scientific measurement and corrupt it to make yourself happy.

You can not compare one dyno to another, same type or not.

Gotta agree with GP's post. I am reminded of the Old Saying: A man with one watch always knows what time it is....A man with two watches is never sure." My best dyno is the seat of my pants feeling with my foot down

I am new to this forum, but thought I would weigh in anyway.

I believe that horse power can be measured every bit as accurately as amps, volts, water temperature, vacuum, RPM's, MPH, etc. Some gauges are more accurate than others, but the value in question can be measured. The watch example was a good one. They need to be recalibrated, or set occasionally and the precision of the chronograph can be determined. How much precision do you need? Do you need an atomic clock to get you to your appointments on time, or will your Timex suffice?

A good chassis dyno run by a knowledgeable operator should give you a measurement that is within 1-2% of another quality dyno run by a competent individual. I would really expect it to be closer to 1%.

Chuck