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Tuning by ear vs. tuning with tachometer

Started by double clutchin weasel, December 31, 2013, 11:47:00 AM

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double clutchin weasel

Well, this'll probably start a fight...but I don't care.

I recently bought a Tech Tach 20K. BEST PURCHASE I EVER MADE! This takes MOST of the guess work out of tuning.  Notice I didn't say ALL?

That's because you STILL need to know how the carb works, and what to look/listen for in the saw.  But, it's a great place to start, and an incredibly good reference tool.

I used to tune exclusively by ear.  But, now I know I was not always on the money.

On my 372XP, it was WAY too lean from the factory.  I had tuned ot by ear long ago.  Then I bought the tach.  It was STILL a good ways off.  Oh, it 4-stroked fine, but the RPM were still higher than you would want.

After I tuned the HI and LO needles with the tach as specified in the workshop manual, I still did not like the way it ran.  So, I did a little more experimenting.

With the max RPM at 13,500 (spec), the saw would not rev "crisply" to that speed.  It labored a bit between 12,000 & 13,500.  Also, it would not "clean up" exactly as I wanted in the wood.  Oh, it was fine in a 24" white oak, but would still 4-stroke a little in smaller (12") logs/limbs.

So, I went back lean just a fuzz (maybe 1/16 turn?).  Now, it cleans up much quicker, even in smaller stuff.  On limbs, it toggles back & forth between 2-stroking & 4-stroking.  Just a little pressure cleans it right up.

Checking with the tach, it revs up more crisply, and peaks at about 13,800-14,000 RPM.  In the big oak, it easily pulls at about 10,200 under chain load only.  Leaning on it drops it down to about 9,600-9,800.  It takes a LOT of pressure to get it down below 9,000.  And, this is with a VERY aggressive chain setup (but, that's another argument in the making!).  So, now I know where this particular saw likes to run, and can put it back to that number quite easily.

Without the tach, my settings were still way off.  The newer saws are just harder for me to "hear" than the older ones.  But, once the tach was used to get into the correct zip code, the sounds are easier to judge.

So, my routine from now on is to use BOTH the tach and the ear to tune a saw.  For those of you who only trust one or the other, try it.  You might like it.

Keep in mind that, even though a saw is 4-stroking out of the wood, it still may be hurting itself.  I make bearings for a living, and I can tell you that every bearing and seal in the world has a maximum RPM.  If your saw sounds fine, bit is turning 2,500 RPM faster than the design spec, rest assured you are hurting the bearings and seals.  Also, the piston speed may be higher than tolerable.

On the other hand, as I saw on mine, going strictly by the tach may not be 100% perfect either.  Oh, I know I was not spinning mine too fast, but it would have had more carbon build-up had I left it set to the tach-only setting.

So, with a combination of a tachometer and a calibrated ear, I feel like I now have my saw set the best it has ever been.  And, I could not have got it there without both.

Let the fight begin!
Eagles may soar, but weasels don't get sucked into jet engines.

beenthere

Quotethis'll probably start a fight...but I don't care.

I wish that you would care...  makes for a much better Forum that way.
south central Wisconsin
It may be that my sole purpose in life is simply to serve as a warning to others

Fatcougar

DCWeasel...... what you say makes perfect sense to me.
Fatcougar
Stihl 461-R
Stihl 026
New Holland TC30
Rankin 3 point Splitter

chet

DCWeasel, well written and informative post.  But, you're opening and ending statements were totally not necessary as it implies you are looking for a fight. If that is the case , you are on the wrong forum.
I am a true TREE HUGGER, if I didnt I would fall out!  chet the RETIRED arborist

ladylake

 No matter what the tach says if you have them 4 stroking out of the cut and cleaning up with a little pressure you'll have them tuned good.  Back some years ago nobody tuned with a tach and there weren't many burnt up saws .   Steve
Timberking B20  18000  hours +  Case75xt grapple + forks+8" snow bucket + dirt bucket   770 Oliver   Lots(too many) of chainsaws, Like the Echo saws and the Stihl and Husky     W5  Case loader   1  trailers  Wright sharpener     Suffolk  setter Volvo MCT125c skid loader

ZeroJunk

Fatcougar made a good point in the other thread . Modern saws will quit slobbering and two stroke under load at about 10,500 or 11,000 RPM. And, they will actually work fine that way, particularly on synthetic oil that doesn't carbon up so much.

But, that leaves you a window of 2,000 or 3,000 RPM to reach factory specified max no load RPM. Anywhere in that range will work.

I suspect saws tuned by ear are all over the place in that range.

double clutchin weasel

Quote from: Chet on December 31, 2013, 12:54:39 PM
DCWeasel, well written and informative post.  But, you're opening and ending statements were totally not necessary as it implies you are looking for a fight. If that is the case , you are on the wrong forum.
I think you missed my point. I hesitated to start this post because I figured there would be a bunch of bickering between the ear guys & the tach guys. But, I risked it anyway as I felt the information might be helpful.

Eagles may soar, but weasels don't get sucked into jet engines.

double clutchin weasel

Eagles may soar, but weasels don't get sucked into jet engines.

chet

DCWeasel, I think you missed my point. The only problem with you're post was the begining and ending statements.
I am a true TREE HUGGER, if I didnt I would fall out!  chet the RETIRED arborist

Caloren

Never had a tach to use, I guess I tune mechanically. I adjust so that the saw idles without the chain moving, so the saw doesn't bog down in the cut, and when the trigger is pressed the saw accelerates without stumbling or hesitating, and try to leave the H a leeetle bit rich.
I read about 2 and 4 stroking, and have listened to Madsens WAV files until my ears are about to fall off, and I can not tell the difference! It all sounds the same. Maybe it has something to do with tinnitus, I have ringing in my ears all the time.
My saws may not be tuned for 'optimum' performance, but at least I've not burned one up in 40 years.  :)
Loren
Stihl MS 170, Stihl MS 310, Stihl 028 AV Super, and half a dozen other no-accounts! Cat D4 D.

double clutchin weasel

Quote from: ZeroJunk on December 31, 2013, 01:06:22 PM
Fatcougar made a good point in the other thread . Modern saws will quit slobbering and two stroke under load at about 10,500 or 11,000 RPM. And, they will actually work fine that way, particularly on synthetic oil that doesn't carbon up so much.

But, that leaves you a window of 2,000 or 3,000 RPM to reach factory specified max no load RPM. Anywhere in that range will work.

I suspect saws tuned by ear are all over the place in that range.

Interesting and useful info.  Thanks!
Eagles may soar, but weasels don't get sucked into jet engines.

double clutchin weasel

Quote from: ZeroJunk on December 31, 2013, 01:06:22 PM
Fatcougar made a good point in the other thread . Modern saws will quit slobbering and two stroke under load at about 10,500 or 11,000 RPM. And, they will actually work fine that way, particularly on synthetic oil that doesn't carbon up so much.

But, that leaves you a window of 2,000 or 3,000 RPM to reach factory specified max no load RPM. Anywhere in that range will work.

I suspect saws tuned by ear are all over the place in that range.
Brown's Summit?

Ever make it over to Jordan Lake or Falls Lake?
Eagles may soar, but weasels don't get sucked into jet engines.

double clutchin weasel

Quote from: Chet on December 31, 2013, 01:44:36 PM
DCWeasel, I think you missed my point. The only problem with you're post was the begining and ending statements.
Well, let me apologize for the opening & closing comments then.

In the future, I'll try to do better.
Eagles may soar, but weasels don't get sucked into jet engines.

pine

Really appreciate your post.  I used to be an ear only type but got a tach a while back and it really helps much like you said.  Neither is better or worse but together create better results.
Thanks

double clutchin weasel

Quote from: pine on December 31, 2013, 02:50:33 PM
Really appreciate your post.  I used to be an ear only type but got a tach a while back and it really helps much like you said.  Neither is better or worse but together create better results.
Thanks
And thank you!
Eagles may soar, but weasels don't get sucked into jet engines.

Al_Smith

Several points to ponder .First altitude and temperature most likely will be a factor in performance .I say with a certainty a saw will not run nearly as well in the mountains of Colorado at altitudes above 9,000 feet as well as in the flat lands of Ohio at around 850 feet .

If you alter the porting  scheme of a saw the factory set parameters no longer apply .It may be higher RPMs or it may be lower depending .

A tachometer is indeed a nice instrument to own .I know many engine builders personally .Some build hot saws ran in such events as the Stihl timber sports .None that I am aware of relies soley on a tachometer .

HolmenTree

Quote from: Al_Smith on December 31, 2013, 03:20:57 PM
I know many engine builders personally .Some build hot saws ran in such events as the Stihl timber sports .None that I am aware of relies soley on a tachometer .
Well said Al......this is where a stop watch timing cuts in a knotless piece of wood does the job. :)
Making a living with a saw since age 16.

ZeroJunk

Quote from: doubleclutchinweasel on December 31, 2013, 02:44:10 PM
Quote from: ZeroJunk on December 31, 2013, 01:06:22 PM
Fatcougar made a good point in the other thread . Modern saws will quit slobbering and two stroke under load at about 10,500 or 11,000 RPM. And, they will actually work fine that way, particularly on synthetic oil that doesn't carbon up so much.

But, that leaves you a window of 2,000 or 3,000 RPM to reach factory specified max no load RPM. Anywhere in that range will work.

I suspect saws tuned by ear are all over the place in that range.
Brown's Summit?

Ever make it over to Jordan Lake or Falls Lake?


I have fished Jordan, but not Falls. I usually go north, have a place at Phillpott in Virginia.

Philbert

Add me to the column that says a tach is a nice tool to have. Adjusting just by ear, or only by tach, can be stubborn strongholds that ignore performance or safe operating limits.

Good comment also on changing conditions.

I have been told that the tachs are more important with newer saws, due to the changes in carbs, etc. 

Philbert

Al_Smith

I think it's more a case of preference than bickering.Noone is right or wrong the way I see it .

On  one side is the crowd that are less experianced with tuning and rely on factory set specs .Then the old farts like me who have tuned just about every engine I ever fooled with by the seat of my pants .

There's really  not too much difference  than the great oil debate or how to file a chain .Methods matter little results are what count .

double clutchin weasel

Hey, Chet.

Why did my "new topic" on AutoTune carbs show up as a post in this thread?

Never had that happen before...
Eagles may soar, but weasels don't get sucked into jet engines.

double clutchin weasel

Quote from: double clutchin weasel on December 31, 2013, 05:30:06 PM
Hey, Chet.

Why did my "new topic" on AutoTune carbs show up as a post in this thread?

Never had that happen before...
I copied the text over to a new thread.  Seems to be okay now.

You want to delete the aforementioned AutoTune post from this thread?

Thanks.
Eagles may soar, but weasels don't get sucked into jet engines.

double clutchin weasel

Quote from: ZeroJunk on December 31, 2013, 04:08:18 PM
Quote from: doubleclutchinweasel on December 31, 2013, 02:44:10 PM
Quote from: ZeroJunk on December 31, 2013, 01:06:22 PM
Fatcougar made a good point in the other thread . Modern saws will quit slobbering and two stroke under load at about 10,500 or 11,000 RPM. And, they will actually work fine that way, particularly on synthetic oil that doesn't carbon up so much.

But, that leaves you a window of 2,000 or 3,000 RPM to reach factory specified max no load RPM. Anywhere in that range will work.

I suspect saws tuned by ear are all over the place in that range.
Brown's Summit?

Ever make it over to Jordan Lake or Falls Lake?


I have fished Jordan, but not Falls. I usually go north, have a place at Phillpott in Virginia.
Both those are lakes I helped clear in my youth.  Please don't do the math!
Eagles may soar, but weasels don't get sucked into jet engines.

Lnewman

Mr. DC Weasel, you know your stuff and provided some good info.  But for a beginner, could you explain 2 stroking and 4 stroking. 
Stihl 170, 210MS, 290MS, 441MS and Hudson bandsaw

Lnewman

Also, when the tachometer reading bounces around, do you select the high or the low or the average reading?
Stihl 170, 210MS, 290MS, 441MS and Hudson bandsaw

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