gr8johnson3

it seems like i need one because everyone is always talking about the 4 stroke rpm when discussing how well it is running. do i need a tach. this will be my first 4 stroke engine (TT 91). thanks.

Sport_Pilot

Highly recommended! Good insurance to prevent frying your new engine with a lean run. You can get by without it if you are very experianced and have an ear for the slight pitch change of a 4 stroke leaning out. But since this is your first engine, and enen the pros use a tach, go buy a tach!

Roby

I totally agree with Sport_pilot.
Get the tach.

Regards
Roby

rajul

My Feedback: (58)

TNC tach that is

gr8johnson3

thanks guys. will do. anything i should look for or stay away from in a certain make.

Sport_Pilot

Hobbico makes a good first time tach. But many other good ones out there also. Also combined voltmeter and tach's if you have not bought a votmeter yet.

daveopam

My Feedback: (9)

I went with the Glow Bee. I have heard great things about the TNC. My first tach was a Hobbico. It took two watch batteries that were exspensive. The Glow Bee uses a 9v.

David

Sport_Pilot

I had a really old one like that. It took two watch batterys and eventually, like every couple of months, I would forget to turn it off and have to replace the batterys. Found that it would work on cheaper alkaline watch batterys instead of silver oxide, then I also took it apart and repaced the slide swith with a spring return push switch. Worked fine. The present one I have from Hobbico uses a double AA battery and automatically turns off.

Ed_Moorman

My Feedback: (1)

The reason everyone says to use a tach is that most people have a 2-stroke ear. We are used to peaking out a 2-stroke .46 and listen for the scream of the prop. You don't get that with a 4-stroke. Since they don't rev like a 2-stroke, many people tend to unconsciously tweak them too much, setting them slightly over lean. A lean 4-stroke will backfire and kick the prop off. Sometimes you lose the turust washer or prop drive. With a tach, you can peak, then back off 200-300 rpm and safely fly.

If you do hear your 4-stroke knocking in the air, throttle back, land and open the needle slightly. It does take some getting used to to set one by ear, so a tach is very useful at first.

William Robison

My Feedback: (3)

Tim:

As Ed and others have said, a tachometer is not necessary. But until you develop an ear for the 4s engines it can be dangerous (read expensive) to go without.

Bill.

Barbarian

I have a couple Saitos that have taught me a lot. I now have very reliable and consistent engines, but it took me going through some growing pains. That said, I'll never buy another 2 stroke engine. I like the sound and feel of my 4s.

I have a tach - and recommend owning one for a number of reasons: comparing fuels, props, setting idles and tuning engines for performance.

However, a simple method I use, with or without a tach, is to always start by going open when tuning the needle. If you hear the rpm drop as you open the needle, then you are on the rich side. Slowly close the needle until you are in a 'flat' range - about 3-4 clicks that don't make a difference by ear. Set your needle about 3 clicks into the flat range. That's all you need. It may lean out a bit more in the air, which is what you want. Once you have it set, with a given fuel and prop, you will probably never need to modify it by more than a couple clicks, even in cold weather. If you wind up moving it a quarter turn - something else changed.

Although these may not be universal 4s truths, they work for my Saito .72 and 1.50.

Good luck!
Barbarian

Hobbsy

My Feedback: (102)

For engine longevity and better "less than half of a tank" performance it is best to richen the rpm down about 300 rpm, I use 200 and others use as much as 500 less.

jaka

Hi!
Of course you don't need a tach for setting the rpm on an engine be it four or two-strokes! Why!
Fourstrokes are as easy to set as two-strokes. When you turn in the highspeed needle the rpm goes up....that simple.
I never use a tach on my two and four-trokes ...pylonracing ,scale or sport airplanes.
Where I do use it occationally is on my twin engined airplanes ...but even there it is not allways needed.
I also use it to record what different props turn after modifing them. In my club with over 130 members no one uses a tach for setting a sport engine.....


Regards!
Jan K
Sweden

William Robison

My Feedback: (3)

Jan:

I'm surprised.

Thought you would say all he needed was APC props and 100% Motul synthetic oil. And using them he would never have to worry about needle settings.

Haw.

Bill.

Cheech

My Feedback: (19)

I have this tach/voltmeter from Airwild. It's a good tool. Use it on the 4 strokes and the big 2 strokes

jaka

Hi!
Oh yeah! Forgot..... Do use a APC props.....But Tach...No!

Regards!
Jan K
Sweden

Ed Smith

I agree with Jan.

A tach will not prevent a lean engine run as was originally mentioned. All the tach will do is tell you the engine rpm. The user still has to recognise the needs of the engine. Different props will give different rpm readings. So to say a specific rpm is ideal under all conditions is false. The quickest way to understand the engines needs is to run it. Listen to it's different sounds, observe the exhaust smoke and interpret what is happening. It is called experience.

Ed S

Sport_Pilot

Jaka, Ed Smith, and Babarian.
Been in this hobby a long time. I can tune a four stroke by ear. You don't tune it anywhere on the flat spot, but rich of lean peak. Just like a two stroke but it is harder to hear the peak pitch. I can do it better with a tach, so I usually use one. Since all four strokes I know of are running in the 9,000 to 10,000 RPM plus 200 to 300 RPM rich of lean works fine. If there are any four strokes that run a lot faster than that then they should require a larger rpm drop on the rich side. You may get by with less than that if the engine has a regulator. But for most of us a 200 to 300 RPM drop should work fine.

N1EDM

My Feedback: (2)

I just tried to look up TNC Tachometers from Skyborn Electronics, but all I get are blank pages. Is the TNC still being made or did they go out of production again?

Other than the TNC tach, what other tachs would you recommend?

Thanks,

Bob

Flyboy Dave

My Feedback: (21)

A tach is a valuable tool to have and use. When you are learning about
how to set and run the engines, you can see as well as hear how the
adjustments and sounds effect the engine....the indicator being the rpm.

Not everyone on this Planet can tune an engine by ear, make no mistake
about that. Use the tools that are available to you to get the best out of
your engines, and run them without harm, at optimum performance.

Do you use a thermometer to see how hot the water is, or do you just
stick your finger in it ? Get a decent tach, and learn how to use it.

Dave.

N1EDM

My Feedback: (2)

Flyboy Dave,
I think you might have read my post a little to rapidly. I wasn't asking whether I should use a tach or not (I have one already) but rather which ones are better than others?

My question was whether the TNC tach is still available, and if not, which one would someone recommend.

I went to the NEW home of TNC Tachs, and I couldn't bring up the pages for the TNC - as if they decided to delete the TNC from their inventory...

Thanks for showing interest.

Flyboy Dave

My Feedback: (21)

I was posting to the thread starter....gr8johnson3 .

Dave.

N1EDM

My Feedback: (2)

Oh, OK. The header on your msg said that you were replying to me...

But the same question... if the TNC tach is no longer available, what would anyone recommend in its place?

Thanks,

Bob

MinnFlyer

My Feedback: (4)

In the Navy, we were taught to take the temperature of the water by sticking your finger in a WAVE

William Robison

My Feedback: (3)

Minn:

And here I thought it was join the Navy so you could RIDE the WAVEs.

Haw.

Bill.