ro347

My Feedback: (13)

Im running a saito 91 with a 15x6 apc prop *****g out at about 8300 rpm at flight settings. Is this enough. Should I be getting more rpms? Should i be running a smaller prop?

Gray Beard

My Feedback: (-1)

How do YOU like the way the plane is flying??

fredscz

My Feedback: (47)

Normally a 15X6 is too big of a prop for a 91 4-stroke in my opinion. I use 14x6-14x7 APC for my 91's in sport planes. I also try to keep the ground rpm under 10,000.
Fred

mpalermo

Yeah that is too much prop I am running a 15x6 on my Saito 100 and getting 9400 does quite well.

Mike

bingo field

I get out of sight vertical (not super fast, but it keeps going up) with a 13x6. This is on my Venture 60. I don't remember what my r's are, but I kept to around 10k when I used the tach. That 91 is a sweet engine.

ro347

My Feedback: (13)

It flies well. Wondering if a smaller prop with higher Rpm(+1500 or so) would give better performance. Verticle is good....But starts to slow after a while. Ive tried a 14x8 and think its a bit to fast especially on landing. Causes plane to float longer. Will try the 14x7 and see what happens. Buy the time ive tried x # of props...I could have bought another plane!

carrellh

From
http://www.horizonhobby.com/Products...rodID=SAIE091S
Benchmark Prop: 14 x 6 Zinger @ 9,100

Using the controversial program, ThrustHP, here are some theoretical numbers

mesaflyer

Hey Roland,
Is that a new motor?
Just asking, because I only have one Saito (82), and although I did not do any tach number's when I first got it, I know it is running A LOT stronger now that it is broken in.
Pete

ro347

My Feedback: (13)

Its at about 2 gallons or so +/- a little.

Jester241

Doubt you'll notice much if any of a difference between the 15x6 and the 14x7. Actually the 14x7 will likely be worse especially during landings. I was told that higher the props pitch,the more it will try to pull it through the air at lower speeds like landing. A larger diameter prop with a smaller pitch will not only be slower at lower speeds,it may in some cases actually act like an air brake during landings because the plane may actually be going faster then the prop wants it to kinda. It seems to me that it kinda hold true too.

Either way,some other points that alot of guys say is that a prop that has 1 less pitch is equal to a prop that has 1 more diameter.......14x7=15x6....or....12x8=14x6...get it? And again,I believe it usually holds true or pretty close to it. And therefore I dont think you'll notice a big difference between your 15x6 and the 14x7. And I think you really should be getting a good bit more than your 8300 rpms for several reasons. And if you want to see a diffence.... try a 14x6. That will give you a noticable rpm difference to get you closer to where you should be. And it sounds like you could be alittle on the rich side,so IF it needs leaned out,that will help raise the rpms.

I've been testing my .91 thunder tiger 4-stroke the last week or two with a 14x4W (wide) prop. I did however have to run it fairly rich to keep the rpms below 11,000 which worked out nice because the engine ran better inverted at that setting. It flew my bipe great until the pavement made it 3/4" shorter from grinding off the tips. Then it barely flew it,lol. Needless to say,I put on a 14x6 for tomarrow and will see how it performs. I think it will be a good match and put me around alittle more than 10,000 rpm where it likes to be. I really liked the 14x4W on that .91,but the 14x6 might be safer. The more I fly and play with prop and rpm's....the more I like smaller pitches and getting the full use of the engines power curve(the rpm in which it make the most usable power). Not to mention smaller pitched props idle way better.

Also note that while testing a 14x6 wooden prop(I didnt have a plastic one)......the engine HATED it because it just didnt have enough weight to it being that it was wood. Seems the compression of these 4-strokes at idle and stuff likes to have some weight there to give the prop some inertia. Got rid of that prop right away! So,personally I'd stay away from wooden props if you havent already.

Nathan King

How much nitro are you using in your fuel? What is your field elevation? What brand of prop are you using? The 14x7 is a perfect sized prop for the Saito 91.

mesaflyer

I am no 4 stroke expert, but that sounds like enough fuel to be broken in. My 82 started to run better after about 10 flights and 3 tanks on the ground, 12 oz fuel tank. After about 15 flights, it would idle perfect and throttle up real nice, and it was mounted inverted. I'm running Power Master 15%. Have played aroud with different props, some of the larger props really make it slow down. Good luck with yours.

Nathan King

Technically not fully broken in, but enough to where you should see an improvement in performance.

ro347

My Feedback: (13)

Im using 15 PERCENT NITRO. Elevation - At about sea level(Northen Jersey). I like how the 15x6 flies....Its just Im wondering If i would get better RPMs out of the 14x7 even though they shold be similar in performace. Ill give it a shot and see what happens. Im looking for good thrust...and not too much speed. Ive done a 15x4, but needed to keep the throttle up to keep speed - so bad on fuel.

2slow2matter

My Feedback: (1)

That's too much prop, plain and simple. You could start doing some harm to the engine as it will run hot trying to lug too much prop around. Get a 14X6 and it will be like a brand new engine. If you must stay with the 15 inch prop, better go with a 15X4 at most.

Nathan King

Yeah, the 15x6 and the 14x7 will load the engine about the same amount. I'd go with a 14x6.