Looking for more HP
 

I have a OS 52 FS and am looking for some more speed. Using cool power 20% fuel and 11x7 APC.
Any mufflers out there that would increase the performance on this small 4 stroke?

Looking for more HP
 

Stevta;
No! There is no muffler that will increase the power of your little 4 stroke. Even tuned pipes for 4 strokes are for astetics ie. (sound).
Your best bet with that engine is to practice with different props.
Try a 12 X 5 APC or as high as a 12.5 X 6.
You can try a 3 Blade Prop about a 9.75 X 7 3 Blade to possibly a 10 X 6 3 Blade.

Have Fun
AMA 6518
The OS really doesn't recommend using above 15% so if it's under warranty be careful.

Looking for more HP ?
 

There is alot more potential in most engines just with a little work instead of spending large $$$$ on racing engines.

Looking for more HP
 

Ovalthrasher,

Although we do appreciate your contributions here, your post found at http://www.rcuniverse.com/showthread...threadid=47349 constitutes an ad under the forum rules. The Engines area is for discussions only. Please remove it or edit it to remove any commercial information. You can place such information in the Product Announcements & Manufacturer News Forum.

Thank's for your understanding in this matter.

Elwood
Engines Moderatorr

Looking for more HP
 

ovalthrasher, maybe if you explained some of the mods you do for more preformamce, elwood would lighten up a bit, and let your post stand. I would be intrested in more info from you.

Discussion or ad?
 

So some guys are hanging around talking engines, and one of them wonders how can he get more power out of his .25. One of the other guys says "Hey, I can help you, I do mods and hop ups on that sort of engine."

Did he just contribute to the discussion, or did he advertise his services? How would anyone else in the group know about the services available from him if he didn't say something?

Perhaps RCU would consider making an area where custom services are offered and those offering these services could list themselves under various categories. Listings could be for custom machining, engine reworking, building, finishing, instruction, etc.

Looking for more HP
 

I want to apologize if I offened anybody by my previous post. I was just stating what we do and I didn't mean any harm by it.

Mods Wrong post location
 

Perhaps we could just turn down the agressivness a bit.
Doing your job is one thing, not using common sense is another.
One is getting paranoid here to reply if someone ask "How are you"
Lighten up guys...you will live longer
5

Looking for more HP
 

ovalthrasher,

No offence, in any way. We just want to ensure that the forums stay away from advertisements. I for one am interested in your service. A few extra ponies from an engine is never a bad thing.

Rossi Ray,

Great idea about a list of this sort. Perhaps we can go a little farther than the Product Announcements & Manufacturer News Forum. I will bring it up to the other moderators, and see if this will be a good thing for RCU.

Thanks!
Elwood

Looking for more HP
 

There is also a links page that has this information. It is found at the top of every RCU page.

Elwood

Saito
 

Some have run the Saito without the muffler...(straight pipe) I do not know if this will increase your hp, but you will think it will by the sound....
The 180 sounds like a snowmobile.
Good Luck,
5x5 :D

Tuned pipe for 4-Strokes.
 

If tuned pipes don't work on 4 strokes, why do full sized Hot Rodders speed so much time trimming pipes and testing them on a dyno? H'mmm?

Looking for more HP
 

SP ;
Your absolutely right on your analysis of Car Motors having power increases from Headers,Collectors and non-restrictive flow through Mufflers. But! these are not car motors and the power advantage of a Tuned pipe is negligible if any on Model Aircraft 4 Strokes. The only reason we use them in/on 4 strokes is for appearance and sound suppression. You will never hear a 4 Stroke Model Aircraft engine get on the pipe(at least not noticable) as you notice on 2 Strokes.

Looking for more HP
 

a tuned pipe for a 2 stroke works by the pressure pulses from the previous stroke from the same cylinder. a tuned exhaust for a "hot rodder" ie 4 stroke muli cylinder engine, the boost comes from a previous stroke from another cylinder. that why a v-8 header pipe comes together in the same place. a exhaust stroke from a previous pulse passing though the header collector from a another cylinder will pull or scavage the exhaust pulse that occuring at the moment. at least thats my story and i'm sticking to it :rolleyes:

Wrong Splatt
 

The principle is the same. AA fuel dragsters cut their pipes to tuned length also. Header companies place the pipes in the collector to avoid them from interfering with each other. There is a reason that tuned pipes are more effective on 2 strokes however.

Looking for more HP
 

You will gain little to nothing from trying to "tune" a model 4-stroke motor with the exhaust, this is fact, we are not talking about cars here. If your exhaust is too restrictive on a 4-stroke you will lose power, so removing the restriction will get you a better running motor.

I will say it again, you want more power USE MORE NITRO!!!!

Tuned pipes
 

The reason tuned pipes don't do much for our four strokes is that the valve timing on most is symmetrical and the cams are relatively low profile. And if the engine companies start to increase cam profiles, then stronger valve springs, stronger pushrods and stronger rocker arms become necessary. Beyond that acceleration and deceleration ramps on the cams become necessary to lift the valve off of it's seat and return it to it's seat gently so that valve bounce or chatter does not occur.

Looking for more HP
 

Take this for whatever it's worth to you.
I've run YS 91AC's on the stock muffler with baffel in place and run them with a straight pipe with an exhaust outlet larger than stock and have yielded a minimum of 300 rpm on the top end with the straight pipe. All else remaining the same.

Down side is a lot more noise for just a marginal gain. I have no idea if your engine will respond the same way or not.

I would'nt worry about running 20% nitro in your OS as long as you insure you are feeding it at least 18% oil as OS specifies as a minimum. Better yet, run 20% oil, your engine will thank you in the long run.

Fuelman

Re: Tuned pipes
 

No that's not the reason. Ever notice that on a 2-Stroke the exhaust and intake ports are open at the same time? Notice that on 4-Stoke racing engines a tuned pipe is just a straight pipe cut to length? Ever wonder why a two stroke tuned pipe gets larger then smaller?

With a high performance two stroke the engine is timed so that not only all of the exhaust goes out the exhaust, but a goodly amout of fuel air mixture goes out also. When the exhaust port opens a sonic shock wave is produced the shock wave will go to the open chamber and reflect off the back side of the pipe and reverse itself. Now the fuel air mixture has reached the front part of the pipe and is filling the front expanded portion of the pipe. The sonic wave pushes the fuel air mixture back through the exhaust port, and even through the intake port! This helps the mixture to gain momentum it wouldn't gain if the intake port is closed. Once the intake port closes the momentum of the reverse pressure packs the mixture into the cylinder and effectively super charges the engine. This effect can be as strong as the differance in a supercharged YS 4 stroke and non supercharged 4 stroke

With 4-strokes this cannot happen even with high duration cams cause the intake valve closes very shortly after the exhaust valve opens. By the time the mixture reverses course the valve is closed and momemtum cannot be built. Tuned pipes on 4-strokes work in reverse from 2-strokes, The sonic wave reverses course when it reaches the atmosphere or collector and after the exhaust valve closes. If the pipe is not tuned it could reach the exhaust valve just before it opens and back up the exhaust and increase back pressure. Instead with a tuned pipe it will have reversed course again after hitting the closed exhaust valve, if properly timed it can cause a negative pressure in the exhaust pipe which improves breathing. So a net power gain but nowhere near the improvement from a 2-stroke. The power gain would only be noticed by racers and then only with a clock and I doubt most pattern flyers would notice the gain, but some of those guys try for every edge they can get.

LadyFlyer can you read?
 

Doesn't work that way for 4-Strokes!

Yes it is the reason.
 

Ed Iskendarian discovered this phenomenon in the late fortys or early fifties hence the Isky five cycle cam which really wasn't five cycles but took advantage of the inertia of flowing gasses to enhance cylinder scavenging and filling by using valve overlap.

OK hobbsey
 

Just keep reading your Hot Rod mags and Isky ads. Fact is valve overlap has little to do with the tuned pipe! Only the opening of the exhaust valve is important. You can read till you or blue in your face but till you go through the calculations or test on a dyno will you ever understand it. Manufactures make lots of claims that I cannot duplicate, one posters claim that adjacent pipes improve performance in a automobile header is, I think, one such prior claim from a header company which is completely untrue. If it were the AA dragsters would have their pipes come out into a collector instead of just straight out.

Posteres who say it will have little improvement are somewhat correct. It does improve performance - a little. If improving the exhaust flow increases performance by 300 RPM as one poster suggested then I'm guessing a tuned pipe might improve performance 100 RPM. But you know 100 R's here, 100 R's there, and they all add up.

Looking for more HP
 

In my YS going from 25%---->30% nitro gives me an extra 350 rpm, why the hell would I waste my time fiddling with mufflers???

Can773
 

I dunno someone forcing you to?

Sport knows
 

Sport knows more than the experts, he's good.