Dyno tested....Mastermind's ported 261cm vs Stock 261cm Gotta see this one.

[wyk]

Looking at the linear rise of the power, there is a sudden dip. I wonder in this this case if it might have been some light detonation. If so, then that dip might not be there when cutting wood.

A dyno puts an extended load on an engine and the heat builds up. Maybe a flash run up to the dip might tell us more.

Chad, that dyno of yours is truly fantastic.

That is under a load. Dyno tests are always under a load. So, it is unlikely that dip will disappear in wood.

 

[Terry Syd]

I'm referring to a hot engine, heat soaked. It is unlikely that a 50cc saw will be used for milling, rather it would be for limbing.

Chad, if you do try that experiment, you have to remember that an air-cooled two-stoke can loose up to 20% of its power when it is heat soaked. If you take a 'cold' reading you will get a erroneous reading that is too high (often done by people to inflate their figures). You'd need to bring the engine up to operating temperatures first, then check the dip - (or if you had some race gas handy...)

 

[weedkilla]

Great article on detonation

http://www.klemmvintage.com/deto.htm

It's nearly 4am in Tennessee, when does that monkey wake up and add his 2c?

 

[wyk]

I'm referring to a hot engine, heat soaked. It is unlikely that a 50cc saw will be used for milling, rather it would be for limbing.

Chad, if you do try that experiment, you have to remember that an air-cooled two-stoke can loose up to 20% of its power when it is heat soaked. If you take a 'cold' reading you will get a erroneous reading that is too high (often done by people to inflate their figures). You'd need to bring the engine up to operating temperatures first, then check the dip - (or if you had some race gas handy...)

Didn't Chad say he did 5 runs minimum? I would think adding a bit of air flow and taking temperatures wouldn't hurt.

 

[chadihman]

I don't know a lot about this stuff, and feel kind of stupid to ask, but what size rim were you using and would the Torque and/or HP numbers change if you switch rim sizes?

It's all in the calculations.

Chad, is this 361 run apples to apples with the 261 run? Would it be fair to compare them?View attachment 356640A sticky where all these graphs could get dumped would be really cool.

I could probably throw in a test with the ported 361. It will have to wait though as I have a pile of things to do now.

 

[whitedogone]

I'm referring to a hot engine, heat soaked. It is unlikely that a 50cc saw will be used for milling, rather it would be for limbing.

Chad, if you do try that experiment, you have to remember that an air-cooled two-stoke can loose up to 20% of its power when it is heat soaked. If you take a 'cold' reading you will get a erroneous reading that is too high (often done by people to inflate their figures). You'd need to bring the engine up to operating temperatures first, then check the dip - (or if you had some race gas handy...)

Interesting....may be prudent to rig a temp probe on the test subjects. That is, if you aren't already doing so.

 

[weedkilla]

I could probably throw in a test with the ported 361. It will have to wait though as I have a pile of things to do now.

Not certain I'd bother, ported 50 against stock 60 is interesting though....
I was really just asking whether it was fair to compare runs from different days. Whether you are seeing a large variation. Wasn't intending to distract you from the runs you want to try.

 

[chadihman]

Any good info on a good tach that will read engine rpms correctly on a CM model or a shaft rpm sensor that will read up to 4500 rpms accurately would be nice. My current shaft rpm sensor works well up to 3300 rpms then the #'s drop and fluctuate. I might try a photo tach with a piece of reflective tape on the shaft love joy coupler. I'd make a metal bracket to hold the tach in place.

 

[tacomatrd98]

Anybody want to see how a Dozerdan 346xp compares? I have one that I would be willing to put on the dyno for the sake of curiosity. IIRC, chad is not that far from me. For that matter, take your pick of saws in my sig, they're all up for the job.

 

[whitedogone]

Any good info on a good tach that will read engine rpms correctly on a CM model or a shaft rpm sensor that will read up to 4500 rpms accurately would be nice. My current shaft rpm sensor works well up to 3300 rpms then the #'s drop and fluctuate. I might try a photo tach with a piece of reflective tape on the shaft love joy coupler. I'd make a metal bracket to hold the tach in place.

Kinda old...... but....
http://www.k2dt.com/library_files/2901.pdf

 

[VinceGU05]

That's the best news a bloke with a new 261cm that has a booking with Randy could ever lay eyes on.
Now the 4 month wait becomes more painful [emoji37][emoji12]

 

[whitedogone]

might google Hall efect sensor

https://sites.google.com/site/measuringstuff/more-sensor-examples

http://www.readymaderc.com/store/index.php?main_page=product_info&cPath=165_10&products_id=147

 

[blsnelling]

Awesome results!

 

[Terry Syd]

Great article on detonation

http://www.klemmvintage.com/deto.htm

It's nearly 4am in Tennessee, when does that monkey wake up and add his 2c?

Great article on detonation - Neat to see the rotary valve 350 Bighorn engine again, I ran one in my desert racer - freaking fast, great torque and a top end that didn't want to quit. It had a 68mm stroke which allowed for some outrageous RPM for a big bore (some of the 250s had a longer stroke).

The 'dip' may be detonation, it may be something else, but something is causing a dip in the power curve. With the dyno a few experiments could solve the issue. I can understand why Randy wants a dyno.

 

[blsnelling]

I fail to see how a tenth of a HP dip is an issue. Why major on the minors, the miniscule? It's not like the thing has a programmable ECM where you can just tune it out.

 

[Terry Syd]

Brad, perhaps the actual peak horsepower was where the dip occurred. In other words, the power curve was cut short when it went into detonation.

 

[whitedogone]

might google Hall efect sensor

https://sites.google.com/site/measuringstuff/more-sensor-examples

http://www.readymaderc.com/store/index.php?main_page=product_info&cPath=165_10&products_id=147

I do believe the eagle tree logger with a hall effect sensor will do what you want. Heck, it will also record temps along the way. I'm sure there is even be a way to tweek their software to do your graphing of rpm/t/hp..... beyond my engineering skill set.
http://www.eagletreesystems.com/index.php?route=product/product&product_id=54

 

[LegDeLimber]

Heck! If It's ok with Cahdiham, all of you guys could chip in the funds to adopt me and then "re-home" me in Chadihams workshop.
Then just give me a worksheet of tests to run.
mercy, just think of all the combos of mufflers, cylinders, carburetors, filters,
multi tap multi fuel tank rack with reg-mid-prem grade gas for changing in the middle of a run
then timing alterations, squish clearance and so on so forth.

It can be jaw dropping when you begin to think of the time it takes to work through all the trial runs of things.

 

[chadihman]

Heck! If It's ok with Cahdiham, all of you guys could chip in the funds to adopt me and then "re-home" me in Chadihams workshop.
Then just give me a worksheet of tests to run.
mercy, just think of all the combos of mufflers, cylinders, carburetors, filters,
multi tap multi fuel tank rack with reg-mid-prem grade gas for changing in the middle of a run
then timing alterations, squish clearance and so on so forth.

It can be jaw dropping when you begin to think of the time it takes to work through all the trial runs of things.

Yeah makes me. To much testing not enough time.

 

[weedkilla]

I fail to see how a tenth of a HP dip is an issue. Why major on the minors, the miniscule? It's not like the thing has a programmable ECM where you can just tune it out.

Because that is the beauty of tuning with a dyno.
A dyno gives a pretty graph and a hp number that makes the owner of the engine feel good about themselves pays the bills with a dyno. But the real gains are twofold - the tuning gains that occur from picking up minuscule things that might be a sign of a problem and making a stack of small gains that add up.
That dip says something isn't quite right, now we assume the engine had correct fueling - but without a wide band O2 sensor up the exhaust we just guess that mtronic is doing it's job. So there are really only two likely causes. That the ignition timing isn't quite right at that point or there is a resonant frequency issue in the inlet or exhaust tracts.
Detonation is easy to check - throw in some higher octane fuel. When you dyno something that is hard to change ignition timing it's always handy to have a can of octane booster nearby. If that removes the dip then fixing it is valid, it will extend engine life.
If it doesn't help then it may be something that is a pain to sort. You can try different exhaust and inlet configurations till you are blue in the face chasing something like that.

Now this isn't a situation where every last tenth of a hp matters, so in one sense you are right, on the other hand it is expected to live a long and happy life so ensuring the tune is safe is important.
The era of coarse tuning of fuel (mtronic/autotune), ignition timing and exhaust back pressure is coming to a rapid end.