Piddler

I can't seem to find the manufacturer's suggested low end and top end starting points for a Thunder Tiger .61. If any one has this information please let me know.

Thanks,

The Piddler

Cyclic Hardover

My Feedback: (3)

It doesn't matter. First, lets set the low end. You need to open the high needle about 3 turns is good enough. Now completely close the low end needle. Take a spare piece of fuel tubing and connect it to the nipple on the carb. Now at the same time, blow into the fuel line and open the low end until you here a hissing noise. You need to be in a fairly quiet area for this

Congratuations! Your low end is now in the ballpark area. The high end is fore the most part a no brainer. you can open it maybe 2-3 turns and lean it from their.

Now after you get things running halfway decent. lets check the low end. There are several back up checks you can do to check the adjustments you made actually had some effect.

You may have to remove a cowl to get at it but thats just what has to be done. While the engine is running at and idle, carefully remove the fuel line from the carb or pinch it off. As the engine quits listen to the rpms. If they increase rigght before the engine quits, the low end needle is rich , therfore lean it but not much, maybe 1/16 of a turn. If the rpms just go down and quit-to lean. There is no reason why anybody can't have a perfectly tuned engine.

I have not had an engine quit on me in a few years due to adjustments. I also only need to set that low end once during any given season.

Piddler

This seems so simple, I pray that it works. I am a total novice and it has been very frustrating trying to tune this thing. I refuse to give up. It didn't realize the low end needed to be turned in such small increments, as was turning a full half turn each time.
Thanks for the help.

tIANci

The TT61 is sooooo easy to tune. HSN just open 2 turns as a base starting point. LSN just do the blow test I guess ...

Piddler

I did the blow test and it was 2 turns out. I think it is a good sign if both responses match up. Haven't had a chance to start it up. I'll try it in the next few days.

Thanks for you help.

The Piddler

Piddler

It was late at night and the kids were already sleeping, so I was only able to set the low end. While the engine was at slow idle I pinched the fuel line and the RPM's increased a lot. I did the pinch test twice with 1/16th turn in every time. In the last test the RPM's increased slightly and then it died. Do I want the low end just slightly rich? What should the low end test do when it is perfectly tuned?

The Piddler

William Robison

My Feedback: (3)

[b]Piddler:

This is where tou stop with the pinching. From that point check how it answers the throttle. Probably OK, but you may need to change the LS adjustment just a hair for best transition.

Bill.

Piddler

Ok, it is transitioning great, not too much blue smoke, not too little. When I position the plane semi verticle the engine quits. I know this means it is usually too lean, but I am already 2 3/4 out on the top end. Could it be a fuel line problem. I have included a picture of the side mounted engine and the fuel system. Any help is appreciated.

The Piddler

William Robison

My Feedback: (3)

[b]Oiddler:

I think I see the problem in your picture. It's spelled S-L-I-M-L-I-N-E. Or maybe P-I-T-T-S. These tend to have low muffler pressure, and consequent leaning of the mixture with the nose up. Plug one of the outlets and give it another try. Probably have to lean the top end a bit.

Bill.

turbo.gst

My Feedback: (8)

Piddler,

Bill, has a good point about theslimline muffler. Those do cause some leaning due to lack of pressure. You might change it and do a real quick test.

Good advice on the low end stuff, now set the high speed needle again. Sometimes when you adjust one side of the range( high speed/ low speed) you have to fine tune the other side after an adjustment. Depends on the engine. No problem, just check it.

Do the same pinch test to check the needle on the high speed. I like to be about three clicks rich as a rule of thumb-- for now it wouldn't hurt to be even a little more rich. Until you are more sure of your ability to tune your engine, you will be on the safe side. You want to pinch the line and have the engine pick up rpm for a couple of seconds. Then test it by point the nose of the vertical. If you still get leaning ( when you are set rich), you may have an issue with the fuel tank. I think you do. I bet if you were to hold the plane inverted, it would go very rich. That is because I think the tank is too low. So while inverted, it would be too high, causing the richening. This is a quick test to convince you that the following is really not just alot of print.

I don't know how much experience you have here, but the tanks centerline should no more than 3/8" lower than the centerline(C/L) of the needle valve. I set mine on the C/L. That is very easy on your side mounted engine. It will be the C/L of the crankshaft viewed from the side. From the photo's, the tanks C/L is probably too low. If you want a plane to fly with the same needle settings for the entire flight, you have to set this properly. This would require raising the fuel tank.

You also have to have assembled the tank properly. Many newbies set the pickup line too long. The fuel pickup line can then attach itself ( by suction with the engine running) to the back of the tank. This restricts flow and can cause leaning. You should make the pickup line about 1/4" to 3/8" from the end of the tank. Also check to make sure that the vent line is not pinched-- you can do a blow test on this line like you did to get a ballpark setting for your idle needle. Now check all external lines to the engine and make sure there are no kinks. With the tank C/L properly set, you will have a good running engine in any attitude.

Then your ready to check your needle settings by test running. Remember, if it won't run right on the ground, IT will not get any better in the air. Don't risk all that work until your engine is running good -- at all throttle settings. Then you will be rewarded with a good handling engine and some good airtime.

There are a few other factors. Fresh fuel, balanced prop and correct size, correct glo plug, no loose bolts on mount or engine and muffler. I don't think this is your problem, BUT they are things that are to be considered while diagnosing an engines performance. I

Good luck,
turbo

Piddler

I decided to try cutting off one exhaust end and it pumped way too much gas in to the carb. On the second try I used a zip tie on one of the Debro deflectors that were attached to the Pitts Muffler. I pinched it to about half closed. The engine passes all the test now. Thanks for everyones help. All responses were extremely helpful. Maybe I can enjoy this thing now that I have invested so much time in it. Building the kit was the easy part, the engine tuning I guess will come with experience.


The Piddler

Cyclic Hardover

My Feedback: (3)

Sorry for not answering but my computer has been acting up. I set my low end for a very slight increase. I have not had an engine quite due to tuning and a few years, so this is a proven method which is also in print in manuals if you look hard enough. I only set mine once in any season and its fine for a few months.

THis is going to be a bit off topic but you need to know it anyways------ Many things can cause your settings to be different from other people around the country or world. Altitude, Humidity DA and all that. What you set your engine at will not even be close to me since I am at 5000ft. All of my Supertiger engines have a low end setting of at least 4 turnrs out!!!!!!!! If you ask what rpms a certain prop should be turning, make sure the reply to consider is one from a similar area or altitude. Generally, all you guys at lower altitude get better performance than me.


I would set that high end needle out around 3 turns, fire it up and dial it in. Their is also another pinch test for that high end too. Dial it in where you think its good. While the engine is full speed, Give a real quick pinh/release to the fuel line by the carb. Three things can happen with this. Were not looking for an rpm thing like the low end but more a rpm/performance thing.

Give a quick pinch, if the engine sound/rpms kind of go down a bitand back to normal and the engine does not quit, the needle is rich. If you pinch it and hear the rpms go up and then back to normal, your on the leaner side. If your too lean and you pinch it, the engine wil quit. On this, I set it for a no change in sound/rpms.

This may sound like much but after you get the hang of it, its no big deal

Jazzy

Not enough muffler pressure from a Pitts!

I've had this problem from storebought and homemade mufflers.
The best thing I came up with was to get some stainless steel window screen or steel scrubbers (a ball of thin steel coils). I folded the screen over two or three times, molded it around the tip of my little finger, and cup in the shape of a small dish. This "dish" of screen was then pushed inside an exhaust tube and pinned in place. The pinning process consisted of drilling straight through the tube with a very small drill bit (<1/16"). Then pushed a pin (from the sewing kit) through one hole, the screen "dish", and out the other side of the tube. Bend over the pin and nip off the excess. Repeat for other tube.

This not only adds some back pressure but also helps reduce the loud "crackle" noise associated with pitts style and inverted muffs.

For the scrubbing pad material just make a small dense ball and the same procedure applies.

I've made three in-cowl muffs for inverted engines and it has worked for all. I even did it on a Slimline pitts for my Mag 1.08.
It works!

Jeff