Track Tac

Prototype dynomometer

This is the formula I use for calculating HP.
 

Attachments

  • correction formula.jpg
    correction formula.jpg
    48.5 KB · Views: 26
  • 2.jpg
    2.jpg
    34.1 KB · Views: 25
95 shaw said:
Looks to me like both can be correct, or both wrong.

Depending on which standard you set your correction factor to.

The J1439 SAE standard produces a number less than indicated hp.

The motorsports std and the std day correction factors produce a number greater than indicated hp, all using the numbers provided by the poster.

All 3 standards assume 0% humidity.

Which, by the calculator in question, indicates a measurable difference in correction factor.

Here is the calculator I used.

https://robrobinette.com/Dyno_Correction_Calculator.htm
Click to expand...
 
I migh be in left field here . It looks like with the link posted.
You have several choices sae hp , estimated flywheel horsepower and msa corrected horsepower and msa estimated hp .
The thing to not forget ; it's only a tool to compare your engines or
improvements .
 

Attachments

  • Screenshot_20201127-172111_Chrome.jpg
    Screenshot_20201127-172111_Chrome.jpg
    108.7 KB · Views: 20
Correction factor as of June 1990. When using this correction factor, you get the same HP as with the old correction factor. This is SAE, the authority.
 

Attachments

  • correction formula 3.jpg
    correction formula 3.jpg
    34.9 KB · Views: 12
These correction factors are used by dyno shops to correct for nonstandard temperature, barometric pressure and humidity. The Flywheel HP estimate assumes a 14% driveline loss. SAE J1349 standard day is 77 º F, 29.23inHg (inches of Mercury) pressure, 0% Relative Humidity. Motorsports Standard InAtmosphere (MSA) is 60 º F, 29.92 and 0% humidity.-------------------------------------------------------------------
14% loss, from the driveline, I think I'll not be using that formula. It does factor in humidity, I like that,, but I can do without it. And I can tell you why.

I'm pretty sure that humidity they're talking about is actual humidity, not relative humidity. They are 2 different things talking about the same condition.
 
alvin l nunley said:
Correction factor as of June 1990. When using this correction factor, you get the same HP as with the old correction factor. This is SAE, the authority.
Click to expand...
:) ...... Your point is ? Your correct and there is no doubt that , you believe your correct ?
My point is , as it says estimated , shoot I can estimate any number you want no need for facts .
 
I'll tell you why they changed the standard.

When using either standard, as the conditions change, higher/lower, the Farther and they get from the numbers being used, the less accurate they are. The change was instituted to make the standard "in the middle" of expected normal conditions. They both come up with the same corrected horsepower, if not exactly, pretty damn near exactly.

The MSA Formula 4 corrected horsepower would be of little use in karting, for 2 reasons. The 14% loss in transfer correction and there's little chance of any curve that I know getting actual humidity numbers. Relative humidity is of little use when calculating HP numbers.
 
alvin l nunley said:


I'm pretty sure that humidity they're talking about is actual humidity, not relative humidity. They are 2 different things talking about the same condition.[/B]
Click to expand...


A revue of the SAE standard indicates that relative humidity is what is used in the calculations.
 
95 shaw said:
A revue of the SAE standard indicates that relative humidity is what is used in the calculations.
Click to expand...
To be accurate you need a air density gauge. About $100 from Longacre.

Still, you can guess, but it's a crap shoot.

In general;
Altitude means thinner air, smaller jet, but it's just a guess.

Hot, in general, needs thinner air. Cold just the opposite.

Barometric pressure. Almost impossible to feel, but more important than temperature. Lots of clouds can generally mean low-pressure.
On and 80° day I've seen air density over 103, that's high.

Generally, cool clear mornings being high air density, cloudy muggy afternoons generally mean low air density.

.038" – .039" will cover about 5 points on the air density gauge. Here in Liberty Hills Texas, over a year, air density can vary about 12 to 15 points. It's generally lower in the summer and higher in the winter. But that's just generally, not a hard and fast rule.

How to pick the best yet?
You need a baseline. Remember that day when you went fast, it may be that you were jetted just right that day, use that as your baseline. Write down the conditions, temperature and barometric pressure. No clouds, in general, means high air density. Very cloudy, in general, means low air density.


I'm working on a theory now that you can change the jets, high/low, to get the right mixture. For instance; you're running a 38 jet high-end and the 22 jet low end. There density, your guessing, goes down some. Maybe not enough for a 37 jet, but put in a 37 it anyway and increase the low-speed jet to 23. I have a spreadsheet that calculates the difference in flow overall.
Air density in general.
Clear cool morning = high air density.
Muggy hot afternoon = low air density.
When the sun goes down = higher air density.
All predictions are "in general"! "In general" meaning better than nothing but you really need an air density gauge.
 
So, in the debate about a change in the correction factors, can we safely assume that there is no real evidence of global warming, at least since 1990, just typical and cyclical trends?
Sorry, am I getting too political? LOL
 
Big Time said:
Is anyone still using a prototype hydraulic,dyno
Click to expand...
I'd say there is a few still in use, plenty of others based on the same design.
I went with the inertia wheel design, and wished after, I would built a hydro or water brake dyno.
The OP for this thread hasn't been here in a few years.
Sadly Al Nunley passed away.
 
Last edited:
XXX#40 said:
I'd say there is a few still in use, plenty of others based on the same design.
I went with the inertia wheel design, and wished after, I would built a hydro or water brake dyno.
The OP for this thread hasn't been here in a few years.
Sadly Al Nunley passed away.
Click to expand...
I was trying to figure out how to use i bought 1 with out a book on how to operate it I don’t have any formula to calculate hp or tq
 
RyanDavisPerformance87 said:
Any forsake anywhere
Click to expand...
I saw one for sale recently for a few hundred dollars and considered picking another one up for myself.
I have a brand new (never used) Prototype dyno available for sale if you're really wanting one...I'm not going to let it go cheap though. ;)
It is identical to our #1 dyno without the load cell and data acquisition.


-----
🏁Thanks and God bless,
Brian Carlson
Carlson Racing Engines
Vector Cutz
www.CarlsonMotorsports.com
Carlson Motorsports on Facebook
www.youtube.com
35 years of service to the karting industry ~ 1Cor 9:24
Linden, IN
765-339-4407
bcarlson@CarlsonMotorsports.com
 
CarlsonMotorsports said:
I saw one for sale recently for a few hundred dollars and considered picking another one up for myself.
I have a brand new (never used) Prototype dyno available for sale if you're really wanting one...I'm not going to let it go cheap though. ;)
It is identical to our #1 dyno without the load cell and data acquisition.


-----
🏁Thanks and God bless,
Brian Carlson
Carlson Racing Engines
Vector Cutz
www.CarlsonMotorsports.com
Carlson Motorsports on Facebook
www.youtube.com
35 years of service to the karting industry ~ 1Cor 9:24
Linden, IN
765-339-4407
bcarlson@CarlsonMotorsports.com
Click to expand...
I seen one on Facebook the other day for sale.
 
You must log in or register to reply here.
Back
Top