Dyno

[Red97]

What does your scale read wide open with no load? Maybe you need to add that into your calculations? Might bring your numbers closer to "normal".

Unless it is an easy conversion factor, and it repeats among lots of saws. Your dyno may just real low, and that is fine. Test a saw stock and then again after mods and it will show the gains.

Which is what a dyno is made for. Show the difference.

 

[Ronie]

What does your scale read wide open with no load? Maybe you need to add that into your calculations? Might bring your numbers closer to "normal".

Unless it is an easy conversion factor, and it repeats among lots of saws. Your dyno may just real low, and that is fine. Test a saw stock and then again after mods and it will show the gains.

Which is what a dyno is made for. Show the difference.

I just looked at one video and with the valve wide open it was reading 1.8lbs but the orifice in that needle vale is small and restrictive so so right off the bat it's getting some load on it. It might take awhile to figure it out but I think it's worth the effort but in the mean time, like you said, it can show me the gains after mods.

 

[Ronie]

I couldn't find a cheap round handle for the valve so made one up, it's a little small but will work better than the T handle. After I finished with it I was looking around and happened on 3" used one on Etsy with the right size square bore so I ordered it. The last pic is the one from Etsy.

 

[Ronie]

Well I guess I'm about finished, I'm giving up for the time being on using the scale and I'm going to use pump pressure to get the numbers. Tomorrow I'm going to put a 7 and 11 tooth sprocket on the jack shaft to see if that will slow the pump down so the saw can turn more RPMs with the valve all the way open. Future plans for it include a digital pressure gauge, oil cooler, oil heater and filter. Today I made a spreadsheet template with the formulas so that I just need to put the pump RPM and pressure in and it will calculate the rest, I'll still have to use an online corrected HP calculator and figure the corrected torque from that.

Example of the spreadsheet template, I just put a pump rpm and pressure in and it did the rest.

 

[Ronie]

Just an update. I replaced the the rubber wheel on the chain tensioner with a sprocket, replaced the tank cap with a filter, added a 3000psi digital pressure gauge, made a solid mount for the pump, put a 7 tooth rim sprocket on it and I have a hydraulic oil filter kit for it that I'll be putting on this week end. I also installed a flow meter with a remote display that came with a temperature sensor and a plastic oval gear pulser but I have an Italian made aluminum body pulser on order and will put it on when I get it. I didn't think about it before but the 10 tooth rim sprocket I had on it is about twice the size of the 11 tooth roller sprocket on the jack shaft so all the gear ratio calculations I was doing are off.

 

[Ronie]

I put the saw and pump tachs in a box and stuck the flow display on it so now everything I need is together and shows up good on the camera. I also took a coupler I had, shortened it and machined a hole for the hall effect magnet, I gave it a try and the frequency counter works good as a saw tach but my magnet flew out of the hole so I JB welded it in there, waiting on it to cure so I can give it a run. I found a NOS magnet block heat cheap and put it on the underside of the tank so this winter I can heat the oil up.



.

 

[isaaccarlson]

Just remember that there is loss in the bearings, pump, fittings, etc... if you multiply up all the percentages, the loss is pretty big. Compare that to the saw driving the saw chain directly with only the chain friction loss and you start to wonder just how much power a saw really makes. I know some will say otherwise, but 5hp going through only 4 bearings that are 95% efficient and then a pump that is 80% efficient, and then through fittings/filter will barely make 3hp. That doesn't include chain/bar/sprocket losses. Multiply those in and there is not much left. Losses in a system multiply, not add.

 

[Ronie]

Just remember that there is loss in the bearings, pump, fittings, etc... if you multiply up all the percentages, the loss is pretty big. Compare that to the saw driving the saw chain directly with only the chain friction loss and you start to wonder just how much power a saw really makes. I know some will say otherwise, but 5hp going through only 4 bearings that are 95% efficient and then a pump that is 80% efficient, and then through fittings/filter will barely make 3hp. That doesn't include chain/bar/sprocket losses. Multiply those in and there is not much left. Losses in a system multiply, not add.

The dyno correction calculator I'm going to use assumes an 11% drive line loss, It maybe more than that.

 

[Ronie]

Finally finished, I got the filter, the new flow meter pulser on, it took a while to get the K value figured out but now it's field tested and right on the money. I also took off the Chinese pressure gauge because it was to slow to react to changes and installed a Cecomp gauge I found at a a good price on ebay. It was a fun project and I think if I built another it could be built a lot cheaper, maybe half the price without the expensive gauges and flow meter. Thanks @Red97, @Dieselshawn and @wcorey for the help you've given me.

 

[Maintenance Chief]

I'm really surprised by the amount of work you gave this project Ron! I didn't realize what was involved with these things.
Hopefully you can get some use and good feed back now.

 

[Ronie]

I'm really surprised by the amount of work you gave this project Ron! I didn't realize what was involved with these things.
Hopefully you can get some use and good feed back now.

There just wasn't any plans that I could find so there was a lot of trial and error and waiting on parts took up most of the time it took me to build it. I think if someone had a plan and knew exactly what parts are needed they could put one together in a couple of days.

 

[gurwald]

The dyno correction calculator I'm going to use assumes an 11% drive line loss, It maybe more than that.

View attachment 347049

Maybe one could calibrate their dyno using an electric motor to run it, knowing the voltage and amps you would know the output effect, there are very low losses in an electric motor.

 

[Ronie]

Maybe one could calibrate their dyno using an electric motor to run it, knowing the voltage and amps you would know the output effect, there are very low losses in an electric motor.

I've seen some small engine dynos on the web that used an alternator and a load cell but couldn't find enough info on them to build one.

 

[Ronie]

Little update
The dyno seems to be working like it should, I've only ran my ported 371 on it but I'm going to run a couple of stock saws on it this weekend and compare the HP numbers to the factory ones.

This is what I got with the 371.
EX 102
TR 118/122
IN 79

 

[wcorey]

Seems odd that peak torque and peak hp occur at the same rpm, peak torque would normally happen sooner. Do you have the data at lower rpm to see if the two intersect at 5252rpm as they should?

 

[Ronie]

Seems odd that peak torque and peak hp occur at the same rpm, peak torque would normally happen sooner. Do you have the data at lower rpm to see if the two intersect at 5252rpm as they should?

That's the lowest RPM I recorded, I'll have to run it again and see what it looks like.

 

[Ronie]

@wcorey I just looked at a 372 dyno run on youtube and the results are similar to the one I got, @Red97 do you think the correlation between my peak HP and torque look typical of a ported 372?

Pic of red97's results

 

[Red97]

Looks pretty good. How is the repeatability? Look good for 2-3 runs in a row?

 

[Ronie]

Looks pretty good. How is the repeatability? Look good for 2-3 runs in a row?

That's the only recorded run I've got, I ran out of fuel on the next run and haven't done one since then.

 

[wcorey]

Yah probably my oversight, since there’s no data at lower rpm’s, the torque could of course be higher back there and I just jumped to a conclusion on the numbers presented.