Another chainsaw dyno...

[RI Chevy]

No reason to have to LEAN on a saw. Just tune the chain to your saw and wood. Let the chain do the work. Much safer too.

 

[Red97]

OK, nice, I didn't connect the dots ... that is the piston you windowed?

Yessir.

 

[Walter Glover]

What an impressive thread! Found this searching for dyno numbers. I have built a disk brake dyno and playing with a 372xp kit saw for testing dyno. I can only get 2.85hp out of it so far. My question is for Red as I see the graphs have corr torque and hp trends. Is that ‘corrected’ numbers and if so what does that mean?
Thanks fellas

 

[Red97]

View attachment 290259 What an impressive thread! Found this searching for dyno numbers. I have built a disk brake dyno and playing with a 372xp kit saw for testing dyno. I can only get 2.85hp out of it so far. My question is for Red as I see the graphs have corr torque and hp trends. Is that ‘corrected’ numbers and if so what does that mean?
Thanks fellas

Nice setup.

What do you have measuring tq? And rpm?

Maybe you are missing part of the calculation somewhere.

"Corrected" means the weather conditions are all recorded and corrected to the same baseline.

So a saw run on a hot summer day, would be corrected to the same standard as one run a cold winter day.

Temp, humidity, barometric pressure is all monitored and recorded throughout the runs. Those things can change the output of an engine this size.

 

[Nutball]

View attachment 290259 What an impressive thread! Found this searching for dyno numbers. I have built a disk brake dyno and playing with a 372xp kit saw for testing dyno. I can only get 2.85hp out of it so far. My question is for Red as I see the graphs have corr torque and hp trends. Is that ‘corrected’ numbers and if so what does that mean?
Thanks fellas

A good test might be to run a wimpy little 25cc saw on there and see if it can reach anywhere near the rpm it can off the dyno with a regular bar and chain. Such a test may show more friction in your setup than expected.

Are you figuring the gear ratio and rpm properly? Looks like if the HP was doubled it would be correct. 2.85x2 = 5.7hp

 

[Walter Glover]

Red, I have a 12” torque arm pressing on a hydraulic cylinder of my making such that 20 pounds reads 2000kpa. For rpm I use a mag pickup sensing the four bolt heads in sprocket into a tach adapter to drive the auto tach. Gearing at 4:1

 

[Walter Glover]

Nutball,I am using the dyno rpm and torque to get hp
Is that not correct?
7.5 pounds torque at 2000 rpm = 2.85hp

 

[Red97]

Nutball,I am using the dyno rpm and torque to get hp
Is that not correct?
7.5 pounds torque at 2000 rpm = 2.85hp

This is where it gets very difficult....

Calibrating everything from scratch.

Can you set a known weight on your cylinder and measure the reading?

 

[Nutball]

Nutball,I am using the dyno rpm and torque to get hp
Is that not correct?
7.5 pounds torque at 2000 rpm = 2.85hp

I'm not the best at math, but best bet is convert torque and rpm back to what the engine is putting out. In theory the HP should be the same at the dyno end, but there may be a conversion error somewhere.

2.85 is right, maybe just a junk saw?

Oh, yea, what Red sed, calibrate. And you don't want any other forces finding their way in like the weight if the braking system if it could skew the results. Darn variables.

 

[RI Chevy]

Nice setup.

What do you have measuring tq? And rpm?

Maybe you are missing part of the calculation somewhere.

"Corrected" means the weather conditions are all recorded and corrected to the same baseline.

So a saw run on a hot summer day, would be corrected to the same standard as one run a cold winter day.

Temp, humidity, barometric pressure is all monitored and recorded throughout the runs. Those things can change the output of an engine this size.

SO... there are variables??? HaHaHaHa...

 

[Red97]

SO... there are variables??? HaHaHaHa...

He could throw out the numbers entirely.

And see what changes come about

That is where all the extra gadgets come into play.

Average,and correct everything back to the same baseline no matter the variables.

It is all just part of learning the system. That is also the reason I took the route I did with a mostly store bought system. Tech support sure is handy at times.

 

[Walter Glover]

A buddy just delivered a properly calibrated large scale pressure gauge. Also will upgrade the force sensor mounting for near frictionless action. Torque arm and caliper were made in such a way that they are balanced and bearing mounted.
I will check calibration with a known weight
Also recheck tach cal
Thanks fellas

 

[Walter Glover]

Nice gauge

 

[Walter Glover]

Thinking on this stuff, Red would your setup provide Uncorrected numbers as in raw torque and rpm?

 

[Walter Glover]

New gauge air purged out with 15 pounds weight as per my shipping scale

 

[Red97]

New gauge air purged out with 15 pounds weight as per my shipping scaleView attachment 290293View attachment 290294

Any way to hang/set the weight on your tq arm? See if it reads the same?

 

[Walter Glover]

Red will do that tomorrow. Was excited to see the big gauge reading so nice!

 

[Red97]

Red will do that tomorrow. Was excited to see the big gauge reading so nice!

If you have a lesser saw to try out as well.

I will warn you..... this dyno adventure is going to test your patience something fierce.... But it can be so much fun too.

 

[BonScott46]

Any stuffed 461’s in the line up?

 

[Red97]

Any stuffed 461’s in the line up?

I'm supposed to be getting one to port, it has not showed up yet.