hp spec...was Re: Motorcycle Horsepower Question

On Fri, 11 Jan 2008 17:10:08 -0900, "Robert Bolton"
<robertboltondrop@xxxxxxx> wrote:


"Turby" <turbosurfer@xxxxxxxxxxxx> wrote in message
news:pq8eo3d45laa68blehlf7t6ifml0qjp9oo@xxxxxxxxxx
On Thu, 10 Jan 2008 21:38:04 -0900, "Robert Bolton"
<robertboltondrop@xxxxxxx> wrote:

I found a reference that said net horsepower was used beginning of 1971
per SAE J1349. The same reference said J1349 was reissued (2004) to
close
some loopholes.

http://www.dodgetalk.com/forums/showpost.php?p=455579&postcount=1

Here's an interesting reference -
http://www.dmv.ca.gov/pubs/vctop/d03_6/vc9950.htm

California seems to require published horsepower to be net hp as defined
by SAE J1349.

Net vs gross still refers to the output shaft of the _engine_, not
rear wheel, which is where the big difference is, of course.

FWIW, I have access to all the SAE specs at work, but I'm off work for
a while, so it will be some time before I can post what they say.

Thanks. I for one would be interested in hearing the highlights of the
standard.

Yeah, it took a while. Not as long as the Moab pics, so my
procrastinating creds may be slipping.

J1349
Surface Vehicle Standard
Engine Power Test Code -
Spark Ignition & Compression Ignition -
Net Power Rating

The spec is 24 pages long - packed with formulas, tables, and
definitions, besides requirements. The 10 major section headings are:
Scope
References
Terms & definitions
Symbols, units, & subscripts
Reference terst conditions & corrections
Lab & engine equipment
Lab test procedures
Presentation of results
Transient vehicle testing
Notes

There are 3 types of "hp" per the spec:
Bp - Brake power
Fp - Friction power
Ip - Indicated power

Bp (c) = Ip(c) - Fp(o)

Where (c) means corrected to reference inlet air and fuel supply
conditions. I didn't convert the numbers, but I think that means an
"ISO" day - standard temp, humidity, & barometric pressure. And ref.
fuel just means regular, mid or premium octane (R+M)/2 gas.
(o) = data observed at the actual test conditions.

There are a bunch of other formulas for atmosphere correction, fuel
correction, etc.
The equipment on a vehicle is controlled in the sense that test
vehicles are supposed to be equipped as they would normally be in
their intended use. Air cleaners, cooling pumps, emission controls
systems, etc, are all required if they are normally installed in
production vehicles. A transmission is not required, but correction of
engine power for transmission losses is not permitted. (huh? That's
what it says.)
The spec differentiates between steady-state and transient procedures.

The definition of "Net Brake Power and Torque":

"The power and torque produced by an engine at any speed when
configured as a "fully equipped" engine, corrected and tested in
accordance to the applicable procedures contained in this standard."

It talks about dyno testing, but also says the road surface must be a
closed course, with dry, flat, level hard-paved surface. It doesn't
say anything about measurement at the flywheel or rear wheel, and as
usual with bureaucratic specs, seems very ambiguous about a lot of
stuff.

BTW, the latest version is dated March, 2008.

--
Turby the Turbosurfer
.

Relevant Pages

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  • Re: hp spec...was Re: Motorcycle Horsepower Question
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