PA BEN

I have a new G-90 and ran it yesterday. (Break in by the book) The break in prop is a 13x6 also the biggest prop the book says to use is a 13x6. This prop seems under size for this engine. I checked the RPM’s at full throttle 12000. (Not broke in yet) The spec says top is 16000 RMP’s. It’s a 3-D plane and I like using X4W props. I have a 14x4W to try but I think it will by undersized too. Also, do I make sure it is broke in w/the 13x6 before changing prop size?I'm using 10% Nitro, can't fine any fuel with less nitro.

noveldoc

My Feedback: (2)

Maybe I'm chicken but I would finish break in with one prop and then play until you find the right one for your engine and plane.

Tom

drube

I have the same engine on my hellcat. Check out this. http://www.quicktechhobby.com/articl...rt_for_two.htm

w8ye

My Feedback: (16)

Pa Ben is saying all the right stuff.

w8ye

My Feedback: (16)

Do "search" on Quick Tech Hobby before actually you buy anything from them. Many items on their web site are no longer available.

drube

Thanks for the info. I only use them for that prop info.

PA BEN

Looking at that chart a 14x6 or 14x8 would work. I was thinking of trying a 14x6. I see heat is a big deal along w/power band. But over RPM's will heat up an engine just as bad as an over size prop. Man this thing screems with a 13x6, just seems to much, even some of the other guys at the field said it seems to much.

carrellh

maybe 15x4W http://www.apcprop.com/ProductDetail...tCode=LP15040W
14x6 or 8 seems wrong for 3D

w8ye

My Feedback: (16)

Due to the small intake runners on the G-90, it is best to keep rpms lower by using a larger prop.

Keep the rpm down below 10500 on the G90

Dave Gerieke always talked that the torque peak was down close to 8000 rpm

DarZeelon

PA BEN,


Please read [link=http://supertigre.com/engines/supg0235-man.html]this article[/link] from MAN's Mike Billinton, and the prop sizes used.

Different strokes, hah?

daven

My Feedback: (1)

15 x 4 W works well with this motor, good luck. I ran it like that on my chipmunk for several years, nice combo. One of the nicest running motors out of the box I have ever had.

daveopam

My Feedback: (9)

14x6 and 13x8 are the bench mark props in my neck of the woods. For 3D I would run a 15X4W APC.

david

charlie1960

14x4W APC
Was born with it. Never turned any other prop.
http://www.youtube.com/watch?v=Y8-1i6Y4zYI

ST G90, Seagull Extra 300 .75

PA BEN

Well it's been awhile. I got out today and put a Master Airscrew 14x6 on and what a difference. This plan has all the power one could ask for. 10560 rpm high and 351 rpm low. When it gets broke in I will try a 15x4W or 16x4W.

Azcat59

I run a 14x8 APC in a Midwest CAP 232. It turns 9000 using 10% nitro. Flies the airplane very well, but I don't do 3D stuff with it. It turned 9500 with a 14x6. Handles the 14x8 well though, and the noise is not too loud.

Clair

DarZeelon

Quote:

ORIGINAL: Azcat59

I run a 14x8 APC in a Midwest CAP 232. It turns 9000 using 10% nitro. Flies the airplane very well, but I don't do 3D stuff with it. It turned 9500 with a 14x6. Handles the 14x8 well though, and the noise is not too loud.

Clair

Clair,


Your engine is now making a respectable 1.466 HP. With the 14x6 it made less power, despite the higher RPM.

Please check the installation of the muffler to the stack... I suspect you may have it assembled 'too snugly', causing the 'drum' to restrict the gas-flow from the stack.
It has been mentioned by some that they cut the stack at a 45° angle, to prevent the drum from ever 'snuffing' the flow.

An MVVS .91 engine, on 5% nitro and with the #3250 pipe, makes an APC 14x8 spin at 10,500 RPM.
This is 2.328 HP and the improvement is much, much more than a tuned exhaust alone should add.

PA BEN

We hooked up a scale at the field on my plan and I was getting 10lbs of thrust. My buddy has a Magnum 90 w/a APC 14x6 and a tune muffler, he was betting 14lbs of thrust. Once my engine gets broke in I will check it again before I change props.

Azcat59

Hi Dar. I have a Pitts style muffler on the ST 90, either a Slimline, or a Bisson. Might restrict the rpm slightly over the big ST muffler but I have more power than I need, flying at about 1500 feet above sea level. I did get tired of screwing around with the ST carb, and installed a Magnum 91 carb, which improved the user friendliness. Nice engine, nice airplane, now I need to fly it more, have 28 airplanes so it is a long wait for its turn!

Clair

baronbrian

My Feedback: (13)

I always ran 13x8 or 14x6 as well on a Goldberg Extra 300 and later a Direct Connection Ultimate Kaos.