Okay, after waiting long enough to get up my nerve, here goes. I have a really stupid question. I have a Brison 3.2 (my first gasoline engine) that has a ton of power. It easily turns a 22x8 Pro Zinger at just shy of 8K rpm, and a 20x10 at 8300 rpm but as you might suspect it is very loud at those high rpm's. After reading a ton of posts about the noise issue, one thing keeps coming up. Keep the RPM's where the engine produces its best power, in this case around 6800-7000 rpm. I know when I throttle it back to this level the noise is much less and I understand why. My question is..... drum roll please....[:@] When you guys set your engines up to keep it at it's best RPM for power, how do you do it. Do you prop it until full throttle keeps it in the correct range, do you set your throttle servo EPA so the max. is in that range, or do you adjust the needles to get it there? I know this sounds simplistic, but I have my throttle servo end throw set so it can't exceed the RPM's I want it at. I really like the way my plane, Midwest 27% Extra flys with a 22x8 so I would like to keep my prop size at that. I also have a 21x8 NX prop to try next time and if it is quieter and flys as well, I may change to that. My goal is to lower the noise my plane is producing. I use throttle management quite well, but there are times when I need to push the left stick to the top! So far, no complaints, but I am afraid that it is just a matter of time.[X(]

Sorry if this is really dumb, but I just haven't seen this question asked before.

Adjusting to the RPMs that you are looking for by richening the needles is not a good idea. If you run your engine rich you will develop carbon build up which can seize your engine.
You could i suppose set your endpoints on the servo but youre defeating your purpose.

There are 2 ways to achieve what you want to achieve.
1 is with the exhaust. You could put some cans on it to keep the noise down.
2nd is to prop it right. I'm sure someone will chime in and point you in the right direction on prop selection.

The very best way to adjust the RPM down at full throttle is by increasing prop pitch and/or diameter. For starters try a 22x10 prop. MenzS, Pro Zinger, Bambula, Mejzlik to name a few. One of the quieter props being a Bambula from RC Showcase. It will cut your RPM way down but the pull power is very good. You might even try a 22x8 in the Bambula.

Ken

You don't NEED to run it at full throttle..If you like the way it flies with the 22-8, just use the little stick on the left hand side to adjust the rpm...Rpm in not your enemy, the engine turned way more than that when the engine was a chainsaw,which is where the cylinder, piston, and carb came from..Sachs Dolmar model 115..
This is not to say that Brison makes engines from used parts....

I was pretty sure the answer would be to prop it to get the rpm's where they should be. I haven't flown with a 22x10 yet, but I do have one and will give it a try. I did run it on the ground and got around 6700 rpm with it. The reason I haven't flown it yet is I am wanting pull, not speed. My landing gear won't let me go any bigger than a 22" prop without clearance problems. I am also going to get a JA peacekeeper for it. The stock muffler is a joke.

RCIGN1, I know that rpm is not the enemy and the engine can handle much higher speeds without damage. I am using the throttle to control speed and noise now, but when I have to push it up to pull out of a manuver, it howls and echoes through the woods around my field. I fly electrics a lot and know all about throttle management.

Thanks for the answers. I guess I already knew the answer, but I thought I should ask anyways!

davidmor,

Your best bet will be changing your brand of prop. Most guys here feel the Pro Zingers aren't good for anything but stirring paint. Get a Biela, Mejzlik, Menz S, MSC, NX, PK Plus, etc. and you will notice a big difference in the thrust department. I have a Brison 3.2 on a Laser 200 and use a Biela 22x8 with good results. It sounds like you have a strong 3.2 that deserves a better prop. Good luck!

Using the MSC 22-8 will give you a lot more usuable thrust at the same rpm you are at now. At both ends of the throttle. By reducing the throttle just a tad with a more efficient prop you will be able to maintain or increase the available power and run quieter.

The MSC props are also economical to purchase, are lighter than the Bambula and Menz, are more readily available, and with a little "shopping" you will find them on sale at Troy Built Models right now.

How much does your MW Extra 300 with that Brison 3.2 up front weigh, and how does it fly.

"How much does your MW Extra 300 with that Brison 3.2 up front weigh, and how does it fly."

It came in at 14 3/4 Lbs. I built it pretty much stock with a couple of lightening mods. I enlarged the lightening holes in the fuse, cut out a lightening hole in the LG mounting plate, used balsa instead of hardwood in the fuse stringers. I used Dubro heavy duty horns on all of the surfaces instead of the plastic ones that came with the kit, and a Dubro HD pull pull system on the rudder. Hitec digitals all around except the throttle. It flys great and has unlimited vertical. I haven't tried any 3D stuff with it yet so until I do I won't know if it really is light enough or not. If need be, I will replace the LG with CG (The stock aluminum one weighs a ton), change out the batteries with LiPo, and may get a CF spinner. I figure that I can get it right at 14 pounds with those changes. I already double beveled the control surfaces so it gets as much throw as I want to give it. I really like the plane/engine combo, I just need to work on the noise.[:'(]

DITTO!!!! no wait--DOUBLE DITTO!!!!!! Zinger pro is what I classify as a sport prop. Not bad-- but best used on Stock Quatra, Zenoah, Fuji, for sport/warbird applications. If you have a performance plane and engine then it only makes sense to get a prop to match.

I did not do any additional lightening mods to mine and it came out at 17.5 lbs. I initially used a Zinger 20x10 but on advice changed to a Bolly 20x10 and got much better results. I used Hitec 545 servos throughtout except for the throttle, with four for the elevator and rudder in the tail which helped with the balance.

I would have certaintly liked mine to be a lb. or two lighter, but it still is a nice flying model with no bad habits. The G45 does a pretty good job of hauling it around and even though the vertical is not unlimited it good enough for me as I'm basically a sport flyer.