Author Topic: Stalker .81 not overly powerful Any ideas? (Read 4060 times)

John Leidle · « **on:** December 21, 2011, 06:48:11 PM »

I have run my Stalker a while now & it's not real strong is there any tricks like opening the exhaust baffles or venturi size.
John

Mark Scarborough · « **Reply #1 on:** December 21, 2011, 07:27:57 PM »

John, you may try talking to Alan Ressinger, he is a Stalker guy I think?

John Miller · « **Reply #2 on:** December 21, 2011, 09:01:07 PM »

Try running a larger venturii, about .3125 dia. and use at least 10% nitro with a 13 x 6, or 7 prop. 7800 to 8200 rpm, prop for lap time.

Alan Resinger · « **Reply #3 on:** December 21, 2011, 09:39:39 PM »

John is right about going to larger venturi and boosting nitro. I was running 20% in my 66RE for a while. The 81 will swing large prop at the kind of RPM that John mentioned. I did send you some head shims didn't I?
Alan

PJ Rowland · « **Reply #4 on:** December 21, 2011, 10:10:34 PM »

Larger Venturi - I had great sucess with .335 and 20 % Nitro

More than enough power.. I pulled mostly 12.5 " but did go up to 13 still in a deep 4 break. 62 - 64oz ships. undercamber .

I ran the Stalker .81 for 4 years.

Now I run PA 75 Merlin - now thats an engine if you want more power...

Bill Little · « **Reply #5 on:** December 21, 2011, 10:43:05 PM »

Quote from: PJ Rowland on December 21, 2011, 10:10:34 PM

(snip)

Now I run PA 75 Merlin - now thats an engine if you want more power...

Only on eproblem, PJ. The Merl;in .75 is not in production and anyone wanting to get rid of one wants a NIB price for them.

I bought over a dozen cars in my lifetime (and drove the wheels off them) for less.....................

BIG Bear
AMM

John Leidle · « **Reply #6 on:** December 22, 2011, 08:12:34 AM »

Some where along the line I heard the Stalkers don't like nitro so I was cautious in upping it . I tried 15% & it responded for sure. Mine came with a .322'' venturi so I will pick up a larger drill bit this am. As far as the PA .75 idea goes,, sure who sells them now days? Also I heard you need to drill out the exhaust but I'd prefer to talk to you boys that already use these things.
Thanks all, john

Gordan Delaney · « **Reply #7 on:** December 22, 2011, 08:48:04 AM »

John,

I`m using the stalker in my 743sq.in Tony.Venturi size is .330 and I run 10% nitro. The prop is 13 1/4 by 5.5 runs great. Uses about 7oz. of fuel on the coast. I forgot to mention the the prop is a Carbon 3 Blade.

Hope this helps.

Gordy

Dan McEntee · « **Reply #8 on:** December 22, 2011, 09:44:32 AM »

I have no experience with this engine, but the exhaust is often over looked as a source of these types of problems. Whatever the engine breathes in, it hast to exhale! Some times a more open exhaust will react as more fuel consumption and more power. Biggest example I have had of this is my Brodak .25. The engine would run fine, needle any where I wanted it, start easy, but had no power. I called the symptoms 'The potato in the tail pipe syndrome." It would only need about 2 ounces of fuel to do the OTS pattern in a Ringmaster, and that didn't quite register with me at the time. My OS LA.25s had more power, and used 3 ounces of fuel. I sent the engine off to Tom Hampshire and he sent it back with a clean bill of health and a modified muffler with more opening at the exit. What a difference! Power and fuel consumption both went up dramatically. This should be the same for any engine. Don't completely discount the possibility of a restrictive muffler.
Good luck with it.
Merry Christmas and Happy New Year!
Dan McEntee

Bob Reeves · « **Reply #9 on:** December 22, 2011, 10:18:13 AM »

I just find it interesting that these big engines are using the same size props I run on my Saito 56 and it has a really small exhaust hole

Mark Scarborough · « **Reply #10 on:** December 22, 2011, 10:19:41 AM »

Bob ,, and only half the exhaust gas to eliminate too,,

Randy Ryan · « **Reply #11 on:** December 22, 2011, 11:02:52 AM »

Quote from: John Leidle on December 22, 2011, 08:12:34 AM

Some where along the line I heard the Stalkers don't like nitro so I was cautious in upping it . I tried 15% & it responded for sure. Mine came with a .322'' venturi so I will pick up a larger drill bit this am. As far as the PA .75 idea goes,, sure who sells them now days? Also I heard you need to drill out the exhaust but I'd prefer to talk to you boys that already user these things.
Thanks all, john

They say Stalkers are supposed to run on FAI fuel and no castor but I found that some nitro and a castor/synth blend made a much happier engine that didn't have overheating problems.

proparc · « **Reply #12 on:** December 22, 2011, 11:57:11 AM »

Quote from: John Leidle on December 21, 2011, 06:48:11 PM

I have run my Stalker a while now & it's not real strong
John

Switch to the Saito 72. Your going to get all you want and more.

PJ Rowland · « **Reply #13 on:** December 22, 2011, 03:41:30 PM »

I tend to run my stalkers a little differently - specially the .81 - I foudn early on they are actually developing most of the power low down in the power band.

I added Shims with the increase of more nitro.. I also ran it very deep, around 6400 on the ground, but I ran 8 Inch pitch. That for me a key secret to getting them working well.

Incidently thats the same principle behind the .61 series, but In smaler airframes. The idea is to get the power low down, and maintain good lap times and power delivery.

Gordons I heard run very well also - we both use much larger venturis and more prop. I wonder if he's ever tried to go 8" pitch

Phil Coopy · « **Reply #14 on:** December 22, 2011, 03:47:58 PM »

I noticed that my two Stalker 46's didn't develop a lot of power till they were fully broken in. I only use FAI fuel...no nitro. I found out by not using shims but using FAI fuel they had a much more consistent break, expecially in the FLorida summer heat. They seem to have a ton of compression, as a matter fact, when hot, mine have started a few times without battery.

Phil

Bill Little · « **Reply #15 on:** December 22, 2011, 03:56:39 PM »

Quote from: Phil Coopy on December 22, 2011, 03:47:58 PM

I noticed that my two Stalker 46's didn't develop a lot of power till they were fully broken in. I only use FAI fuel...no nitro. I found out by not using shims but using FAI fuel they had a much more consistent break, expecially in the FLorida summer heat. They seem to have a ton of compression, as a matter fact, when hot, mine have started a few times without battery.

Phil

HI Phil,

My buddy (also named Phil!) bought an early plain bearing Stalker .46. He used some Powermaster 1/2 and 1/2 oil, 10% nitro. Ran like a dog........... Then I had him read the instructions, got the right fuel (FAI) and it turned into an outstanding running engine with very good power. It still is a very nice engine (and it's been years).

BIG Bear
AMM

John Miller · « **Reply #16 on:** December 22, 2011, 04:12:43 PM »

The Stalkers are an interesting assortment of engines. I have been, and still am a big proponent of running FAI fuel and mostly synthetic oil in them. Whenever somone posts with problems with one, my normal suggestion has been to go back to square one, and run them as the factory says to run them. It gets the engine back to a known starting point, and often the problem goes away.

Then there are those exceptions to the rules. Engines like the .66, and especially the .81 respond very well to higher nitro, and better breathing, if you want to get real grunt out of them. I mean, they run pretty decent stock, on FAI fuel, but weak, compared to other engines in the size range.

Gordan took the Stalker .81 and went from stock, to running a .325 Dia. venturii, and 10% nitro, with 11-11% castor-synthetic. Using his prop of choice, CF 13 1/4" 3 blade 5.5 pitch, His big Tony is impressive flying on the combo.

Sufficient to say that some of these Stalkers can be upped in performance, but first set the base line by running them as the were intended, before you start modifying. You should not have to make any other modifications, other than venturii size, and head shims.

PJ Rowland · « **Reply #17 on:** December 22, 2011, 05:12:32 PM »

PLUG PLUG PLUG!

Gordan Delaney · « **Reply #18 on:** December 23, 2011, 09:38:15 PM »

John Miller,

Like I said in the earlier post Venturi size is .330. Not 312 or 325. Please note: .330

John Leidle · « **Reply #19 on:** December 23, 2011, 11:05:05 PM »

I made a .333" venturi yesterday & will put it in the air as soon as I'm able.
John

KAZ MINATO · « **Reply #20 on:** December 24, 2011, 03:14:22 AM »

Φ8.2 to 8.4mm venturi

6800rpm to 7200rpm

13.4 to 14.2 X 7.0 to 7.5 pitch 2B

12.5 X 7.5 to 8.0 pitch 3B

10% nitro fuel

Kaz Minato

Allen Brickhaus · « **Reply #21 on:** December 25, 2011, 01:30:47 PM »

Kaz,

Thank you,

Allen Brickhaus

Dan McEntee · « **Reply #22 on:** December 25, 2011, 03:19:28 PM »

Sounds like the Stalker .81 wants to ruin similarly to the old ST.60, or like the Bob Reeves style of four stroke engines. Big props, more pitch and lower RPM range. We really do have a wide range of engines to choose from these day in stunt, and sometimes I think there is a tendency to try and run them all the same way. I guess if there is a "normal" it would be the wet two stroke that some engines like to run at, as in the OS LA series that is so popular, and the high RPM pipe runs. I guess the short answer is you gotta give the engine what it wants, and some engines have to have a load to make power. I had it explained to me using a chain saw as a reference. With the way a two stroke chain saw is timed, a properly tuned chain saw will sound like crap on the bench, but will clean up and sing a good tune once a load is introduced on a log, and I find that to be true. It all depends on how the engine is timed.
God luck and have fun with it.
Merry Christmas and Happy New Year,
Dan McEntee

John Leidle · « **Reply #23 on:** December 26, 2011, 04:17:00 PM »

I took the big boy out this morning with my new .334" venturi 15% fuel runnig a 12-7 , 13- 7 APC prop 8100 & 7950 RPM The engine showed promise for sure. The outboard wing on my 15 year old Impact folded up so that ended the testing. I need another plane to fit it in now.
John

proparc · « **Reply #24 on:** December 26, 2011, 04:19:06 PM »

Quote from: John Leidle on December 26, 2011, 04:17:00 PM

The outboard wing on my 15 year old Impact folded up
John

Sounds like good power to me!!!

John Leidle · « **Reply #25 on:** December 26, 2011, 04:21:18 PM »

The thing was running just a touch rich so more tuneing one thing for sure mine is a gas hog 5 ounces gets me maybe 4 minutes ,time will tell.
john

PJ Rowland · « **Reply #26 on:** December 27, 2011, 03:41:01 PM »

RPM and pitch are the two more critical area's to look at.

Everyone was shocked when they heard I was running 8" pitch, but thats where the engine likes to be for a deep 4cylc.

Even Kaz recommends that pitch and rpm.

John Leidle · « **Reply #27 on:** December 27, 2011, 07:20:53 PM »

Thanks for the reminder PJ 8 pitch props arre comman the 7 pitch anyway. .
Rain now untill further notice