freakingfast

My Feedback: (3)

Massive props. Tach numbers could help.

mfuess

Using COOL POWER 15% Nitro, my 95AX did this:

PROP Size MFG. RPM
13 x 6 APC 12,400
13 x 8 APC 11,250
14 x 6 APC 10,800
14 x 7 APC 10,320
14 x 7 Graupner 9,630
14 x 8 APC 9,750
15 x 6 APC 9,600

Harry Lagman

MFuess that's a wonderful data set for the .95. Thanks for sharing!

It looks like it's easily as powerful as the FX .91 and it doesn't appear to mind heavier loads.

freakingfast

My Feedback: (3)

Very nice mfuess! Good data and range. Thanks!

coopster88

My Feedback: (45)

Broken Wings

I am using a 12oz tank. I have wanted to put in a larger tank but I don't think I will have the room. I am sorry it has taken me so long to get back I have not been flying. My radio is in the shop and I am trying to sell my house so life is busy right now.

Coop

coopster88

My Feedback: (45)

mfuess,

Which one performed the best in your opinion and what type of plane did you fly them on or was it just a bench run?

Coop

RDaisy

Thank you very much !

Let's spend money now....

mfuess

My favorite of the props tested, is the APC 13x8. It gave me good thrust and excellent throttle-up transition. My 95AX has been in two airplanes so far. It was first put into an R3 Gee Bee, then later moved to an old Great Planes FUN-ONE.

I also installed a Performance Specialties "ULTRA THRUST" on my AX. I plan on testing the props again to see which one's do best with this tuned muffler.

estradajae

Correct me if I'm wrong....

I've read that the 91 4 Strokes swing a 14x6 Prop at about 10k Rpms....That the magnums are capable of so...

May one get better results in your engines with a bigger prop??

mfuess

10K RPM on a 91 spinning a 14x6 prop is pretty much correct. I'm taching 10,800 RPM on a 14x6 APC. There is so little difference between a .91 and a .95 that it's more a matter of a good tune than size. There is only .01 horsepower difference between the .91 and .95AX.


*** APC 13x8 Narrow Prop ***
Stock Muffler RPM= 11,250
UltraThrust Muffler RPM= 11,880
Tuned Pipe RPM= 12,030

estradajae

Yes!....but I mean a 91 4 stroke!

There are also reports from the tower 75 turning 11700 RPM on an APC 13x6, so I don't see much power difference here...

APC 13x6 @ 11700= 1.78 HP (tower 75)
APC 13x6 @ 12400 = 2.09 HP(95AX)
APC 14x6 @ 10800= 1.87HP
APC 14x6 @ 10000 = 1.49HP (magnum 91 4T...from the posts around here)

With the props mentioned, the engine develops about 1.8HP.... how are the numbers of the 91FX?

Seems a little on the down side to me??

mfuess

NO, my AX engine is turning a 13x6 at 12,400 RPM on the stock muffler.

APC 13x6 @ 12,400 RPM= 2.334 horsepower

__________________________________________________ ___________________

OS 95AX with stock muffler

PROP Size MFG. RPM SPD THR HP
13 x 6 APC 12,400 70.46 13.19 2.33
13 x 8 APC 11,250 85.23 10.85 2.32
14 x 6 APC 10,800 61.37 13.46 2.07
14 x 7 APC 10,320 68.41 12.29 2.11
14 x 7 Graupner 9,630 63.84 12.7 1.75
14 x 8 APC 9,750 73.87 10.97 2.03
15 x 6 APC 9,600 54.55 14.01 1.92
__________________________________________________ ____________________

estradajae

Yes I know! I was putting some numbers there to compare (I edited the post a couple of times)....

I'm using the prop power calculator from Pé Reivers, I guess you have another one.

I'm just pointing that the 91 AX doesn't look to me especially strong, but I may be wrong, I don't have two stroke engines in the 90-100 range.

mfuess

You have to fly with a 95AX to appreciate it. From idle to maximum RPM on a 95AX is about double that of other engines.

I'm cranking out 12,030 RPM on an APC 13x8 and it goes from idle to top RPM almost instantly.

griesel

I had trouble with my 95AX 4 stoking at 40 and 50% throttle.
When temperatures got down to 40 - 50 degree I started
having dead sticks. I finally found the cure today. The
engine was running cold even at 80 - 85 degrees F.
I wrapped the engine with Reynolds aluminum wrap
about 3/4 of an inch from the top down, but not the top.
I also boosted the nitro from 15 to 25%. This is at 3000 ft.
elevation which reduces power about 9%. I don't think
25% is excessive at 3000 ft. Anyhow the engine ran smooth
at 40 and 50% throttle and the dead sticks went away. The
next task is to figure out how to lower the nitro; probably with
some more heat shielding.
Added on 12/16: Removed the aluminum foil and then lowered
the nitro to 20% and the engine is running fine at 40% throttle.
It also does not 4 stroke at idle but does at one or two clicks up.
It also is running more consistantly at landing. The plug is an
Enya #3.

jessiej

Have you tried different heat range plugs?

jess

griesel

I tried a bunch of glow plugs. I think the Enya #3 was best. But none of them
eliminated 4-stroking at 40% and 50% throttle.

Bax

My Feedback: (11)

It's quite normal for any model two-stroke engine to be rich in midrange...you won't necessarily eliminate four-stroke mode when in the midrange. That's because fuel flow is not linear throughout the throttle range, and you also need a bit of excess fuel in the mix to allow the engine to accelerate when you open the throttle.

griesel

Bax:
I finally got it to stop 4 stroking at 40% and 50%.
Increased nitro to 25% ( 3000 ft elevation ) and wrapped
3/4 inch wide tin foil from top down but not on top.

DenverJayhawk

Griesel: I live in denver at over 5280ft elevation. Will I have trouble with this engine? I normally use 15% nitro fuel. I need an engine for my Big Stik 60. What is it that you're doing with tin foil?

Ernie Misner

You won't have a bit of trouble with any of the AX series engines. They are the best engines ever made. As Bax mentioned, any 2 stroke can run a bit fat in the midrange at times, especially if the tank is a bit high, using a Macs muffler, etc. This would be a perfect engine for any 90 size application. Sure wish I had one!

Ernie

Strykaas

Provided it does not peel...

Kweasel

My Feedback: (29)

I once ran an APC 14-8 on a 91FX and a 108FSR, both with stock mufflers and 10% nitro. The 91 would turn 9500 and the 108 did 10500. Too much prop for the 91s carb size.

griesel

I wrap tin foil around the cylinder head to increase the head temperature.
The problem is the engines run too cold and are running rich at mid range.
I saw the same thing with 91FX's, just a little bit better than a 95AX.
If you run your plane most of the time at full throttle I feel these engines
do fine without self destructing if set up properly. 3D stuff.
If you do a lot of part throttle flying like touch and goes and IMAC aerobatics
Not so good.
At 60 to 85 degrees F, at 3000 ft. the engines did OK, not great but OK.
At 40 degrees F, when full throttle and idle were properly set up I was
getting dead sticks every touch and go; actually touch and not go; even
when I ever so gently increased the throttle. The tin foil and 25% nitro
at 3000 ft made the 4 stroking at mid range and dead sticks go away.

Nitro: the maximum OS lists for Nitro percent for 95AX and 91FX is
20%. At 3000 ft the power loss is about 9% and at 5000 ft the power
loss is about 15%. Increasing nitro at higher altitudes replaces oxygen
lost, partially restores power, and the engine runs hotter. In cold
weather and higher altitude you can use more nitro. Just be careful.

Picture: This is a H9 Twist 60 with the cheeks sawed off and the engine
mounted sideways. The prop is a MAS wood scimitar 14X8. I found
noticeable better vertical with the 14X8 versus the same prop in 14X6.
RPM was 9500 max; 9250 operational max. The aluminum foil is held
on with a tie wrap. No temperatures were measured.

I am also going to try an OS FS110a; less power; less weight; may run
better over a wider range. PS I love OS 55AX engines. They are
wonderful on 40 size planes.

DenverJayhawk

Griesel: would you say the 75AX is less hassle and runs better than the 95AX?