ahicks

My Feedback: (2)

With max thrust in mind, is there a target rpm (range?) we should be propping for (using the standard exhaust), or are there too many variables due to all the different prop designs to come up with anything usefull?

Has anyone sourced something that could be used to extend the stock exhaust tubes a couple inches? Not interested in a solution requiring welding.

Thanks,
-Al

w8ye

My Feedback: (16)

The maximum practical thrust vrs prop, vrs rpm, etc has yet to be set up in chart form. All we have is some scattered reference rpm's with different props under different conditions.

Some of the thrust values given are calculated rather than measured on a fish scale. The calculated values given so far have led to much debate. Even the fish scale is debated by some people.

The engine does respond well to a tuned pipe but this sets up a whole new set of variables

Todd has given some actual values a couple posts up for both a typical tuned pipe and a new stock engine. These type reference values are usually all you will see.

Most likely the only concrete facts ever presented will be reference figures from individuals under differing conditions. This is typical of most of our model engines.

There is another thread on the SAP 30 in the Pattern Forum and there are some pipe values given there.

It would be nice to have torque/power curve charts etc but we can get along just fine without them.

ahicks

My Feedback: (2)

W8ye (or anyone) -

OK, this is what I was looking at, thinking about. I was just wondering if Todd may have gone out the top of the range he (we) should be running in with the use of the 18x6?




So the question is -
Would you think the difference in thrust seen above might be mainly due to prop design, or could it be that the engine is pulling harder at the lower rpm? Or are you saying not enough info is available to form a decent opinion?

Not even remotely interested in piped performance, though I'm very familiar with the potential.
Thanks, -Al

w8ye

My Feedback: (16)

Go to the other thread and look for a Vess 19A number on a stock engine. Compare that with the 18 - 6 number Todd gave

The Xoar 18 X 6, Vess Sport 18 X 6, APC 18 X 6W, and the 18.5 X 5.5 all seem very comparable in rpm within this thread. This looks like where the 3D guys are focusing?

Syssa Aircraft

Please keep in mind these numbers were all taken on new engines (less than 10 minutes running time).

The rpm you want to have your engine running at is 8000 rpm or above for the engine to be efficient.

For higher pitch props (8 and 10 pitch) running on the ground wont tell you everything. You need to fly the plane to see how the speed is. Higher pitch props unload quite a bit more than the lower pitch props used for 3D and sport flying.

The 14 pitch I have on the Sundowner turns only about 9,600 on the ground...but unloads to about 12,000 in the air.

Any thrust figures that I ever present will be actual, either from an engine on a test stand or as installed in a plane using a digital scale attached to the tail of the plane on a smooth surface.

The only program I found to be accurate was, I believe, obtained somehow, a while ago, from PE Reivers (sorry spelling?). It was quite accurate actually. Others have been off by as much as 45%.

Joystick TX

I now have over 3 gallons of gas through my engine. Currently using 87 octane (up to 10% ethanol) at 50:1 mix with Pennzoil 2 Cycle Air Cooled oil. I have the stock muffler and the Vess 18x6 sport prop.

With a temp of 88 deg. and my location at 600' altitude I measured 8,700 rpm. The most rpm I have seen so far was 9,200 peak, I like to run about 300 rpm below peak.

The Vess prop gives me about 300 rpm more than the Zinger 18x6 with better throttle response and a little better vertical performance on my GS Sportster. Most flying is done at or below 1/2 throttle with full throttle reserved for take off and vertical maneuvers.

Acceleration from idle (I like 1.700 to 1,800 rpm) to 8,700 is as fast as my servo will move.

Slow and Steady

Hello Tod, A friend who attended Joe Noll told me you were doing demos with an Extreme Flight 78" Extra, which was performing 3 D aerobatics. Can you tell me the prop you were using with this plane?

Syssa Aircraft

I was using a bit of a special prop...its an 18.5x5.5 Vess...right now we are testing it out and have only a few prototypes...but it seems to be very good so far!

ghoffman

My Feedback: (3)

Todd, I want a couple of those, and a drill guide too! I bought a 19A and want to try it as well. Do you still have my CC number?

Slow and Steady

Thanks for the info Todd; I heard the Extreme Flight was very impressive with your engine and I may swap out from my Funtana 125 before to long. Take Care!

Syssa Aircraft

Not sure if I posted here or not yet...

SAP-180HP with ES composites pipe

77 degrees out and just above sea level

10,200 rpm Mejlik 18x6 21.3 pounds pull (measured on Extra with digital tension meter)
9760 rpm Vess 18x6 21.5 pounds pull (measured on Extra with digital tension meter)
9450 rpm Vess 18.5x5.5 22.5 pounds pull (measured on Extra with digital tension meter)

This engine was run on dino oil 40:1 and had about 7 flights on it. (just over a half a gallon of fuel)

Syssa Aircraft

forgot to mention that the tach numbers and thrust were measured in the Extreme Flight Extra 300 78"

Antique

My Feedback: (4)

Thank you for the REAL information....

50%plane

My Feedback: (5)

That's still on a new engine, isn't it? have ya'll tested a Syssa with a stock muffler on the 18.5 X 5.5??

ahicks

My Feedback: (2)

From Todd's notes on the previous page:

Here are some more results from a brand new engine with stock muffler with the 18.5x5.5 vs the 18x6 Vess.

18x6 @ 8600 rpm 16.60 pounds thrust 70 degrees outside 250 feet ASL

18.5x5.5 @ 8260 rpm 17.25 pounds thrust 70 degrees outside 250 feet ASL

18.5x5.5 @ 8300 rpm 17.64 pounds thrust 70 degrees outside 250 feet ASL

50%plane

My Feedback: (5)

Any data from a broken in motor yet?? Using a stock muffler, Royal Purple @ 50:1, and a Vess 18.5X5.5, my motor is hovering my 12 pound 78" Extra at half throttle... Pullout is great! It feels like the power has doubled since I flew it at the Nall....(it was still breaking in) Maybe it was just the awesome weather... I do not have a tach or fish scale, or I would be posting my numbers too....

50%plane

My Feedback: (5)

Anyone tached their engine post-break-in?

ghoffman

My Feedback: (3)

I have the Syssa on a ES pipe and it runs great, 9600 with a Vess 18-6. It has tremendous throttle response, and starts very easily, due in part to the accelerator pump carb. Here is a vid of it burning some holes in the sky with an EF Extra. I have a DA-60 as well and the quality level is basically equal.
http://www.youtube.com/watch?v=vg6YtO17oNQ

wingburner

My Feedback: (17)

Very first run with an insert in each muffler tube.

Vess 18/6 8400
Mejzlik 18/6 9200

5150flyer

Same setup and numbers on my new engine. Sure starts and idles nice.

5150flyer

Vess 18.5 x 5.5 8450 after about 1 gallon

Syssa muffler w/ sound inserts

Joystick TX

I have over 550 hours of engine run time now. My onboard tach reading yesterday, with the Vess 18.5x5.5 prop, was around 8,400 RPM at 87 degrees and 620 feet ASL. Old style muffler with the tone inserts.

The engine still starts great, hand starts with one or two flips, and it runs great at all throttle settings.