gasfreak

My Feedback: (13)

Has anyone ever ran a Super Tigre 91 inverted and if so did you ever have any problems with it running picking up fuel etc.

twinman

My Feedback: (2)

Have two of them on the VQ P-38 and no problems. Believe me, I am very picky about reliablity on a P-38. Am using 15% fuel, and Master 13x8 three blade props. Also, I like the three blade props. Have Jtec Muffler, inverted style.
Hope this helps. Also runningf four more on twins, but not inverted.
Twinman

skyking424

Twinman,
as many G91's as you have maybe you can help me. I have one on my VF 66" Extra 300S. It runs great! The first start of the day needs alot of prime but from then on it will start with a flick of the finger. The problem is, it will idle down and run good for maybe a min. then it goes into a lower idle speed and depending on how fast the idle was set it may or may not continue to run. It is like it has a high speed idle and a low speed idle but you never know when it is going to go to the low idle. It makes for either a hot landing or a very scary low slow and dirty stall landing. I changed to a perry carb and even put a new Super Tigre carb on and it doesn't change. Running a 14x6 or 13x7 prop doesn't change it either. It only has about 3/4 gallon of fuel run so maybe it just needs broken in, I don't know. It is mounted sideways and am using PowerMaster 15% nitro 18% oil Any ideas?
Thanks

cap10b

While your waiting on Twinman to answer I'll put in my 2 cents.

I had a Super Tiger .90 in a TF P-40 inverted.

1. Ran totally stock including carb.
2. Ran 15% red max fuel
3. 13.5x8 Graupner prop
4. Ran great, started easy, (mine would flood easy so look at your plumbing set up to see the tank center line).
5. Used a hemostat to shut off fuel when shut down because fuel would siphon out due to tank level.

My experiences with the stock carb is wrought full of nightmares and successes. Else where in RCU I have posted comments on using the OS 7D carb and the ST .90. From what you describe I would say you have an air leak someplace within the carb meaning check the needle valve orings, check the carb seat (use medium thread lock to get a good seal from carb to block) clean the carb and make sure your not fighting dirt or foreign objects and filter your fuel into the tank from your fuel bottle and again from the fuel tank to the engine. (and use and install a new plug whether you think you need to or not)

Set the carb to the stock setting, I think there used to be an owners manual posted on the supertiger site a long time ago. I had one floating around someplace but probably gave it away. Once the carb is clean and back in stock configuration start the motor up and document every detail you can about how many times you prime how many flips ect. Tune the carb according to the manual and start the low end procedures i.e....start, tune bring throttle down to idle punch full throttle see if the engine stumbles or if it sags ect...

Once you determine where you are in the low end tune move the low end needle in 1/32 movements. Any more than that and you will pass the sweet spot.

The reason I document all my procedures is to compare when you finally get frustrated and yank the motor out and place it on the test stand and run the engine again. the comparison between your install and the test stand will tell you if you have problems with your install. IE tank centerline, plumbing problems (fuel lines making too tight of turns, pinched lines ect.)

Many people will not or do not have the patience to do all this. They usually run down to the hobby shop and buy an OS sell the Sup .90 and from then on bash supertiger. But tuning the OS .61/.90 FX is basically the same you need to know where you are in the tuning procedures and the only way to do that is document your efforts.

The stock carb is a good carb and the newer versions are better, but sometimes the install can make them a little difficult to tune on the low end. Many people say I can get mid to top end and weak or unreliable idle, or I can get a good idle to loose mid range and be well below peak RPM on the top. They do not seem to be able to get both


Just my .02 cents worth.

JDS

skyking424

JDS Thanks for the info.! I have the engine out of the plane and will be running it on the bench this weekend. I have the manual and tried adjusting it to the book but no luck. It runs great, good response and all just the idle is not consistent or even close. I tried switching plugs from Fox to OS it seems to like the #8 plug the best. I am going to install the perry carb. and start over with the adjustments and keep a log of everyhing, good advice, Thanks!

cap10b

Skyking,
I also like the Perry Carbs and had two of them. BUT. If you think the Supertiger carb is touchy read the Perry manual and they tell you in big bold letters their carb is very touchy. (On the low end) They say to use a smal slot tip screw driver to turn the brass wheel and that sometimes you need to turn past your point on the slash marks and come back to it. Here is another thought recently I read where the cats eye on the spray bar can be turned with the two slot tip screws the hold the barrell into the carb body. Buy turning the spray bar it can affect the idle and transition. I've never done this but some say it works.

It sounded good at the time. !!

JDS

skyking424

JDS
Yes I agree with you on the perry carb. I had it on before because I thought that was the problem. That carb has easy fuel flow, all it takes is a touch on the adjustment. I liked the Perry carb except for the high speed needle valve not being long enough to come out of the cowling. When the idle acted the same I put the stock carb back on. Thought I would try to get everything running good with the stock parts, at least I have the stock manual to go by.

twinman

My Feedback: (2)

Hey, it's thanksgiving and I am tweeking my VQ P-38.
I really cannot add to the above comments. It does sound like an air leak. I would also consider checking the back plate gasket and the older ST's had a front plate also. Turning the bearing plate allow counter rotation.
I would really go to 15% fuel or check your fuel. Hey, you don't have a check valve in the muffler pressure line do you? Don't. I have also found the ST's may or may not like after market mufflers due to loss of back pressure.
If you decide to change the carb, and I really do not feel this is necesssay, but I did it for more power. Here is a post I did for my club newsletter about getting more power.
Good Luck,
Twinman
"ASP Carbs on ST Engines"
Sep-13-02, 08:13 PM (CST)




My Motto -If it ain't broke, it needs fix'n!
I was in one of our local hobby shops the other day and on the sale table was an ASP 1.08 which I was casually handling. It was then that I noticed that the mounting barrel looked surprisingly familiar. The store owner had in stock an OS 7D carb which is pretty much a standard replacement for the Super Tiger carb. I was able to compare the two and noticed that the ASP carb was a little bigger in the bore area than my ST favorites. Thoughts starting spinning in my head. Would it work? The store owner was nice enough to lend me the carburetor from his own personal ASP 1.08. I took it home and sure enough it fit the bore of a Super Tiger 90 carb opening. (OK so he saw a sale coming!). I should at this point say that both carburetors are similar in design. (Read this bigger than the carb Super Tiger uses in the 60, 75, and 90.) It was interesting to note that the A.S.P. carb casting is very similar to the O.S. The high-speed needle valve and fuel nipple are either purchased form OS or an exact copy. The idle adjustment is definitely from the earlier Super Tiger carbs that used a knurled knob adjustment. Later ASP carbs have gone back to the internal idle screw.

ON to the test

7:00 pm Thursday night. Yes it was dark! (Car headlights will work with photo tachs!) A Very tired Super Tiger 90, with a 13x6 master Air Screw prop, narrow spray bar (note the previous posts for this discussion),tuned pipe, and 15% Rich's Brew synthetic fuel.
Witnesses in attendance, my son Kyle, and Rapter, a fellow club member, who thinks we are nuts. (What does he know, he fly's combat!)

Test Results
Standard Super Tiger Carb - 13,000 RPM
ASP Carb on same engine fuel- 13,500 to 13,600 RPM. Good idle, transition and awesome top end!

Flight Results
Test bed-one very used and heavily repaired Super Stick 60. (Who said two or three tubes of epoxy is not heavy.) It previously took 90% or more throttle to hover. With the larger ASP carb it now hovers at 60% throttle and accelerates straight up out of the hover and fly's straight up almost as fast as during level flight. Let's just say take-offs are quick!!

Conclusions
1. You get an awesome performance increase for a small investment. An ASP 1.08 carb retails for $35-$40. An OS 7D carb costs $65. Same size and parts...hard choice?!..Not!!!
2. You can put off rebuilding an engine due to the new performance. Why bother there's no need!..Well almost!
3. You must increase either the diameter of prop or increase pitch. The RPM increase in dives is scary. You don't want to put a rod through the side of the engine.
4. You will still go straight up with a 14x8 prop, just not as fast. Tried a 14x6 later and liked better.
5. Shrewd Hobby Shop owner suckers me into spending more money!!!! Yes, I gave him back his carb and bought new one!
6. For some reason my fuel use is climbing!

The flight tests will continue on the Super Stick for determining reliability. If it continues as it is now, there will be three Super Tiger 90's in the house (two on a twin engine Ultra Sport 1000 back from the grave.. another story, another time) with ASP 1.08 carburetors. Note, after I first wrote this story for my club newsletter, I did install two of these on a twin with two ST 90's and have never looked back.

Note, later I did install these on the twin ultra sport and loved the increased power. Don't worry, I have carbon fiber in the wing!!! I ran this combination on that Ugly Stick for dozens of gallons and never looked back. Engine was mounted up right.

I installed these carb's on a set of ST 2500's that happen to be in..yes you guessed it..a P-38. Gained 400 rpm with 18x8 props.

More Later!
Off to "fix" something else!!!!

twinman

My Feedback: (2)

Now you got me on my soapbox, so here is another post for my newsletter on the ST engines.
Hope this helps.
Twinman
"Two Stroke More Power ARG ARG!!"
Sep-13-02, 07:48 PM (CST)
LAST EDITED ON Sep-13-02 AT 07:49 PM (CST)


In the ever day quest for increased engine performance, I have discovered a few relatively simple ways to increase engine performance without breaking the
bank (or incurring the wrath of the significant other).
No contrary to common held misconceptions, too much power is never enough!!!!!!!!!!!!
You can always throttle back!!!!( If you believe that, I have a good deal on a bridge over the ship channel for you)
Supertiger( my personal favorite)
1. The simplest method of increasing performance in the smaller( up to ,51 size) is to change the spray bar in the carburetor to part number 22072813. This is the spray bar used in the .61 and larger ST carburetors. Warning, the part you get with that number may or may not be the preferable flat spray bar. Sometimes they substitute the round one. This bar was discontinued for a while at the last of the production in Italy. I have seen the new Chinese ST 90's and the flat spray bar is back!!
In personal experience on the same day, same engine (ST.45), fuel, and a 12-4 propeller, I found a solid 600 RPM increase (Yes With A Tach) and no other modification. You may find that backing out the idle adjustment one turn may be necessary for reliable idle. I can find no loss of transition or reliability with this modification. Reliability is very important to me as I use two of these engines on an airplane.( Note article on don't do twins!)
This spray bar was discontinued even for the larger ( up to .91 size) and so you may have trouble trying to order or find one. Yes, I said it twice, so noone can say I did not warn you. Check your larger ST engines to be sure that you have the smaller spray bar. The milled spray bar from Super Tiger is now shipped with the new Chinese engines. Stores are having a hard time getting it.

To determine spray bar identification
1. The standard spray bar is completely round as you look down the carburetor. The bar is a uniform .155" in diameter.
2. The preferred bar has flat sides milled on each side .098" across and .336" long from the end.
3. I believe that it would be possible to modify a standard spray bar to those dimensions relatively easy. WARNING: If you grind too deep, you will break through to the fuel passage and ruin a perfectly good $15.00 So be careful!!!!!! This is brass!

Exhaust Modifications
1, Many engines can benefit from increase exhaust flow. Larger mufflers and tuned pipes are several good and expensive methods.
2.A properly set up tuned pipe on a two stroke can and will (I have tried it) gain upwards of 1200 RPM. Draw backs are cost and a rather "peaky" engine. Peaky is defined as an engine that increases RPM normally and then instantly screams up 2000 to 3000 RPM! Not good for many smooth maneuvers, but impressive. Watch out for this jump on take off, or the plane will dart sideways. I finally decided not to peak and only gained 600 rpm on a 14x6 and left it at that.
3. If you fly many of the OS brand engines, you will find a conical shaped cone inside the muffler. Unbolt the muffler, and remove this baffle. Reassemble the muffler and retune the engine.
I have found no increase in .25 size engines, but have seen 300 RPM increases in the ....40 size and larger. Yes, it is slightly noisier, but not objectionable.
4. Another trick that I have found simple and cheap is to add a second outlet to the muffler. Find the hollow threaded rod used to secure the light socket in lamp shades and the two small flat nuts. Drill into you muffler case ( if you have a muffler that you can dissemble) for the hollow threaded rod. Tighten the flat nuts against each other to lock the hollow rod in place. (Note, One inside the muffler and one outside)
Results: On a Supertiger .40 a solid 300 rpm. Note that this decreases the muffler back pressure and cause lean conditions in some engines or applications. It is also slightly messier than stock. This can be improved by using two of those silicon exhaust deflectors ( and it looks neat!) As a side note, the sound quality changes to almost a twin cylinder sound due to different exhaust outlet timing.
5. While on the subject of those silicon exhaust deflectors- Yes they do keep the airplane cleaner, however, they also cost around 200 RPM or more, loss of performance. If you must use them, then use the largest one possible to reduce loss of performance due to increased back pressure, or go to the twin outlet idea.

skyking424

Twinman,
Wow looks like I hit the jackpot on Super Tigre information. I am printing it all out now. Thanks and I can't stand it im off to the garage.

twinman

My Feedback: (2)

Thanks, If you are crazy enough to do twins, I usually hang out in the twins forum, then you really learn about reliability or ELSE!!!
With the VQ P-38, which also has ST 90's. (Note, not recommended by the manufacture of VQ at this engine size, but I NEEDED IT!!), I am flying two other twins with the ST 90's, one 108" P-38 with ST 2500's( One reversed), and one twin bash with ST 45's.
My personal favorite is the fox idle bar long.
Good Luck,
Twinman

cap10b

I think people who can tune and fly Supertiger engnes like Twinman turn out to be the most knowlegable engine guys at the field.
There are two kinds of modelers those you flip the prop and fly and those who twist and grind on the needle valve and are never happy with the way their engines runs.

Good engine guys that you can trust and rely on are far and few between.

LOL

Rendegade

I know all about the peaky Supertigre's on pipe.

I have a G90 piped and pumped and low and behold, the supertigre carb is GONE!

Why because it's a pain in the rear to get a reliable midrange.

I swapped it for an ASP 108 carb and never looked back

The idle is super slow and super reliable, and the top end picked up roughly 200-300 rpm from the larger venturi.

OH yeah, and an OS F plug seems to help the idle.

Here's the Supertigre with my custom header and the ST carby which lasted one trip to the field before being relogated to the "crappy parts" box.

skyking424

Thanks for all the help Twin & Cap! I high temp. permatexed all the gasket surfaces and also I am running a Slimline Pitts Muffler and it always sounded like a weed eater on idle so I put a Hyd. line cap into one of the exhaust outlets to get more back pressure. That realy helped on the idle and the sound. Still wanted to be a little wet to start on the first cold start so I changed to the perry carb. ( if it aint broke fix it. ) That seemed to help the hard cold starting but will know for sure after it sits all night. I like the ASP carb idea. I have another new G-90 and a JTec. Pitts muffler that I bought for my Seagull Edge 540 that I am waiting for the brown truck to bring. Just in case you were wondering if I would toss the SP to the side and buy OS. I just ordered another G-90 to put a Davis Diesel Head on for my Model Tech P-47. No thanks on the flying the RC twins at least for now. Just like the full scale, some fly ok on one engine and others will wear your leg out on rudder while your butt is sucking up the seat cushion. With the RC your not in the cockpit so you are already behind the airplane when the fan stops spinning.

rc34074

My Feedback: (5)

skyking- your idle concern is happening because of one of two things:

a. the engine is only about 1/2 broken in. it will settle down to idle better when its fully broken in. unitl its broken in the idle is unsteady and you need to keep the idle speed up some.

b. the engine may not be getting enough cooling air. if its not cool enough it will tend to heat up in the air and go lean. this will affect the idle as well as the top end. has the engine died in the air? if so this is often due to overheating, regardless of the engine.

you need to set the tigers to run somewhat rich when they take off. you will see a small smoke trail in the air when they are set right. use an idle bar plug. i usually use a fox long.

i use bisson pitts style mufflers on my tigers. they have a larger chamber which makes the sound more "mellow" as they say, and the engine is easy to tune. the ones i have seen on the slimline pitts mufflers all are touchy to tune and they sound real tinny, and they tend to hiurt your ears. i have tried plugging one of the two outlets to get more back pressure, to see if it will turn a bit faster at the high end. this will add 300-500 rom or so to the top end but it makes tuning real touchy. in fact it gets almost as bad as with a poorly set up tuned pipe. tuned pipes that are designed right for the engine will not make this engine touchy to set. pipes that have too sharp a back cone will be real touchy to tune as the relected wave works right in only a very narrow rpm band, so the engine will tend to drift in and out of tune.

be sure to hold the plane vertical with the engie at full throttle to check that it doesn't slow down due to a lean high end setting.

how high is the fuel tank cl? if its very high above the carb cl or too low the mixture will change as the fuel level goes down. a low tank location will cause something like your idle thing and may be a part of your problem- it depends on how low the tank is and how much fuel has been used out of the tank- that is when the fuel level goes down the idle will go leaner. but the short breakin time is likely most of your idle problem.

i guess i have someow gotten the perfect g90s as i have 6 of these in my warbirds and have not had much problem with them- it is mty standard warbird engine- in fact i tried a saito 100 this summer and took it out in favor of a g90 .

good luck.

ed

skyking424

Hi Rc,
The G-90 has never quit running in the air or on the ground and I have always ran it a little rich like you say a smoke trail. It would even do the high then go to low idle speed on the test bench same as in the plane. I wanted to think that it was maybe just needed breaking in more like you said. I think i may have fixed it per my last message at least it didn't drop as many RPM's on idle as it did before. My tach is in the mail so I didn't get the exact numbers but before it would idle slow enough for my VF 66" Extra 300 to sit still and idle nice except for the weed eater sound, then after maybe a min. it would drop enough RPM that it would just run with alot of shaking. So when I am on approach and have the needles pegged to say running at about 1/4 throttle the RPM will drop then im adding power and when over the numbers im hot because the RPM's are still high. It seems to only do it at 1/4 throttle or less. It would be ok if i had a 5000' runway for some nice wheel landings but not that lucky. I hope to fly her later this week to see if I did any good on the test bench with alot of great advice from everyone here.

Cyclic Hardover

My Feedback: (3)

Let me tell you a story from my G90. Ive had two of them and they're very good engines. A couple years back i had my first G90 in the little WM P-51. What a mover until its untimely end from a battery failure. I had over 200 flights on that baby.
Anyways, the first 10 flights were miserable. Ground run ups were perfect. Get it in the air and a minute later it overheat and come in with my throttle full open and engine is at an idle. I went over everything and even sent it in to Hobby Services "twice within a month and they found nothing!
Got it back again and re installed it "again" and flew it again and it overheated again and I got &^%$ again! So I took a long hard look at it "again." I noticed my fuel line from the tank to the carb came out as normal but it curved around and such. I took a guess that there was to much curve and that my line maybe pinched.
So I made my fuel line longer to sure there was no pinch and that was it. Over 200 flights without a problem. So check the fuel line. It may not look pinched enough to cause a problem but it might.

DA2000

My Feedback: (2)

I had the same problem with mine. Being a long time fan of Perry carbs, I went with a Perry 4501 carb which has the same size venturi as the 108 size carbs. It took me about 2 minutes to get it set and now the engine runs perfect! I also gained 600 rpm.
JB