Has anyone done any tests on power decrease using silicone exhaust deflectors.

Is there any noticable difference. Do the longer deflectors produce more of a decrease than the shorter.

There appears a slight increase in power if the standard muffler baffle is removed.

I have an OS46AX and OS55AX. Standard muffler with baffles removed. Just wondering if anyone had Tached an engine for comparison using deflectors.

On my MAGNUM .15xls i lost 1500rpm with an exhaust defletor, with my TT PRO .46 and .36 the loss is about 1000-1200rpm. I took it off the magnum but both TT's still have them on as it keeps the plane alot cleaner and the .36 has lots of power for my Avistar and the .46 still rocks on my Twist

That's a lot of power decrease... 1000-1500 rpm is what you gain in the best cases when you use a tuned pipe, or a "special" muffler....

I use an exhaust deflector on my Magnum 46 xls, I got about 12500 rpm max, as soon as I can test I will tell you if there is any gain by removing the deflector...

Such decrease in power looks more than is with the baffle tan with the deflector....lots of rpms indeed..


Jorge

I used to use the deflecters until someone at my club suggested that they can straighten out when the power is on and possibly restrict the size of the outlet at the bend. Goo gets on your plane no matter what so a bit more wont hurt . Cheers the pope

On a muffled twostroke or fourstroke engine the exhaust deflector will decrease the power by a few hundred rpm. On a twostroke with a tuned pipe the exhaust deflector will not decrease the power and doing it correctly it will sometimes increase the power output[sm=thumbs_up.gif]

PH,


On an MVVS .49 with the standard #3245 muffler, adding a Hobbico .35-.90 size deflector caused an immediate drop of ~1,100 RPM.

The cleanliness was limited to a more scattered distribution of the same dark oil.


An exhaust deflector is simply a waste of money, with negative consequences to the power.

Dar, I wish you had not made that post. Now I have to go rethink two of my planes. I have one on a muffled YS61LS two-stroke and one on a Rossi tuned pipe installation. Picture is of the current YS installation. I don't have one of the tuned pipe Rossi. But here is one of the pipe installation prior to switching the engine from Webra to Rossi. The pipe now has the same type deflector as the YS61 shown.

The blue line that looks like it is going down to the muffler on the YS is the fuel vent line from the tank. It is not connected to the muffler.

Flyer95, what kind of 2 strokes are you running a deflector on ?, 3 of my engines lost at least 1000rpm with the deflector on.

Quote:

ORIGINAL: airbusdrvr

Dar, I wish you had not made that post.

AirBusDr,


Had I not entered the post, you would have been immune to that RPM loss...

It is always better to know what to expect, but I believe some engines may even benefit from installing a deflector.

Dar, I hope you know my post was, as we say in the States, "tongue in cheek." Meaning, not serious. You have always been a valuable resource for engine info and I'm going to make some changes. Where I have the YS61 side mounted engine, I have thought about making a couple of faired covers for the two rudder servos under the middle of the plane that get the brunt of the oil. I'm going to do that and take the exhaust deflector off. The one on the tuned pipe, I may just shorten it as the pipe exhaust blows againt part of the fuse.

Thanks all for the replies.

100-200 RPM would not make much of a difference (I would think). 1000 or more probably would.

I wouldnt expect it to be so much.

Dar.

Im running deflectors on both OS46AX and OS55AX which I recall you had the OS55AX.

I run off dirt strips so had a filter on the OS55AX. Have now removed and replaced with two layers of ladies stockings to prevent the bigger stuff being ingested. (dont tell my wife). If the loss is closer to 1100RPM I should remove the deflector.

I have read reviews of flyers commenting the OS55AX has plenty of power.

Ive run 11 X 7 and currently 12 X 6 APC props.

I fly in the tropics (30-34C) with a 40-46 size pattern plane.
I operate dual batteries and converted to trike so a bit extra weight there.

I would not say its overpowered.

It may be a combination of Hot humid climate, 10% nitro, air filter and deflector.

I will put up with the lack pf power if its the air filter as the dirt where im flying is too much to run without some sort of filtering (IMHO).

If its over 1000RPM drop from using a deflector, I think I will remove it.

Cheers

Wow yeah...if the deflector is causing such rpm loss I will remove it too....

Jorge

I still believe a deflector works for better pressure to fuel feed besides of cleanness.So unless needing for the last drop of power I would use it.

The fact is that a 1000 rpm loss is quite considerable....I have read that you could gain that much rpm using a tuned pipe, maybe a little more, between 1500 rpm to 2000....

Anyway... Is there anybody that has the chance to test it with numbers?.... run the engine with the deflector and tach it, and then removing it and taching it?

Well, on 2 new magnum .15 xls on the break in stand we were getting 18200rpm, we then built our planes and added an exhaust deflector ( dubro .20-.34 ), my freind was having some problems setting his low end needle so we got the tach out and tested both engines, i couldn't figure out why my engine was only turning 16550, took off the deflector and back up to 18000 it went, so it's not on that engine anymore, next time i'm out at my shop i will see if i can tach my TT PRO .36 and .46 with and without the deflector.

I put a deflector on my OS FS .91 Surpass II which is installed on my Super Skybolt. I cut about 1.5" off the end of the deflector leaving just enough after the bend so that the exhaust is still deflected straight down.

I noticed absolutely no drop in rpms with it installed but the model is considerably cleaner after 5 flights. There was only a very light dusting of oil on the belly of the plane whereas the belly, landing gear and underside of the stab used be completely covered before.

On the other hand i was breaking-in an OS FSa .56 4-stroke on the test stand. I put a deflector on because the needles and exhaust are on the same side and i was burning my hand with the exhaust whilst tweaking the needles. I saw 200-300rpm drop in peak rpms with the deflector installed.

I would be very interested to hear from anyone that has actually tached their engine with and without the deflector.

So far the thread has indicated zero decrease to 1500RPM drop when using a deflector.

I would suppose it may well vary depending on what engine, exhaust and possibly what prop you are using.

I see props for the OS55AX range from 13 x 4 to 10 x 10.

Unfortunately I dont have a Tach to check my OS46AX and OS55AX.

PH,


Tower hobbies have quite [link=http://www3.towerhobbies.com/cgi-bin/wti0095p?FVSEARCH=tachometer&FVPCODE=RF&search3=Go]a broad choice[/link], for pretty good prices.

Even the cheapest (I have had it for 7 years) does a pretty good job. You don't really need a TNC, if your hearing can distinguish between reasonable (perfectly accurate) figures and those that are 'off the charts'.

With a Webra 55 and Jett muffler APC 9X10 a gain of 300 rpm was seen with a deflector. A visable improvment in the air too.

It's case by case, most of the time you loose a few hundred RPMs.

microsprint9,
A larger exhaust deflector is better for performance on a muffled two or fourstroke engine. A piped engine is a different story. On my twostrokes in use OS91FX, 108FSR, 120AX I only use quiet tuned pipes with exhaust declectors and a piece of aluminium pipe. The dimensions are 8mm innerdiameter x1 thickness x lenght 100mm. It gives a very good tank pressure, instant acceleration from idle and very clean airplanes at the end of the day. I also use OS-F glow plugs in all these twostroke engines.

freakingfast

Interesting. You gained 300RPM with a deflector.

Anyone tached an OS55AX or OS46AX with and without deflector.

Well on my TT PRO .46 running an APC 12.25x3.75 i was getting 11500-11700rpm with the deflector, as i was brosing through the "Tachometer Readings " forum i found most guys running this setup without a deflector were getting 12100-13000rpm with the same prop.

I know it's a little bit different but my SuperTigre 51 that I am running on gasoline gained 200 with the deflector. The muffler is the stock ST boat anchor. I don't normally run one so I tried just to see if it made a difference and that was the result.

I do run one on my Raptor 50 and it makes NO difference with or without. When I get some more time I will try my TT 40 Pro on my Viper and see how it reacts.

Can anyone else confirm that there will be no loss or even a slight gain when using a tuned pipe? I want to run a deflector on my piped magnum 52 but I really do not want to lose any power.