Hughie42

The beginner is me. I have a full pipe and header from circa 1999. I want to bolt it on to my ST G-51 which will subsequently go in to a Model Tech .36 Extra 300. I want a reasonably speedy model to thrash about on the weekends. Are pipes difficult to tune and mount, and if so am I better off just purchasing one of the newer items such as the Jett Stream pre-tuned pipe, which they claim will increase a ST RPM in the order of 2-3 thousand. What prop would you recommend swinging, with an emphasis on speed for the model and motor in question?

Can I also use these Jett pipes on an OS 55AX. This time in a 40 size F3A style aircraft, called the Shadow, forget who makes it, smaller version of the Power 3D. Again what size prop would you recommend?

Thanks all

Mike Connor

My Feedback: (5)

I have never owned the engine you are using but for tuning the pipe you can go to
http://www.macspro.com/tuning.asp
The Jettstream tuned mufflers are a great and simple way to go for a side exhaust engine. Their claim and my experience says you will get 1200 to 1400 rpm increase using the correct prop. Check out the Jett web site for info. It seems like I remember reading the OS 55 AX may be better for torque rather then rpm.

MJD

My Feedback: (1)

They're not difficult per se, but you have to understand the procedure and know how to analyze what is going on. A tuned muffler system probably gives you a bit wider rpm range in which you'll see boost. To see that boost you need to operate the engine in the pretuned range of the system. For specifics on the possibilities with the Jett tuned muffler system, I would cross-post to the Jett support forum, Bob27 probably will toss you some sage advice in no time.

That said, an Extra 300 is not a speed model, but it can fly quickly with enough power. Since it is also an aerobatic model, and you're dropping a .51 into a .36 airframe, my first instinct is that for flexibility over the entire operating range of the engine a regular can muffler might be the most versatile choice, giving you the baseline power of the engine and the tractability of a can muffled engine. I'd take a stab that a 10-7 would be a good starting point, allowing the engine to spin up reasonably well and offering good disk area, possibly dropping to a 9-8 or so if it will pull that somewhat draggy airframe well about which I have some doubts.

IMHO next in line from the can muffler would be a tuned muffler system a la Jett, but I would run your idea by them in the support forum and get a recommendation. I'm not sure I see the point of a full pipe in an Extra, but that would be your call.

My $0.02 worth, your mileage may vary.

MJD

vicman

My Feedback: (10)

You won't reap all the benefiet of having a tuned pipe on a 300. The high speed snap is brutal, fortunately it usually happens only once[X(].

Flyboy Dave

My Feedback: (21)

....if the pipe is not correct for that engine, trying to install it and tune it might
be more trouble than it is worth. []

You might want to try the stock muffler on the S.T. 51 first. If you get the 300
going too fast you run the risk of flutter and destruction of the plane, because
of the large control surfaces....that plane is not designed for high speed.

Like Mike said, if you desire better performance, you might look into one of the
new performance mufflers....they work as good as tuned pipes these days.

Try an 11-7 on the 51 for some decent speed, but be careful. Seal the hinge-line gaps
to ward off flutter.

FBD.

rmenke

My Feedback: (13)

Hughie 42

There are few airframes out there capable of staying togeather at twice the HP and speed of the original design intent. Keep this in mind when (not if) this thing comes apart. If you want t fly 3-D, set up a 3D plane correctly and learn to be an exceptional pilot, or as good as you can be. If you want to go fast (a relative term) go with a fast airframe and engine. Any OS, other than Ducted Fan units are designd for typical sport usage, meaning good transition and torque. A jett stream muffler (pipe) is a simple and effective way of increasing any engines rpm and still have reasonable transition. You will find the typical tuned pipe to be a pain to install and run, but effective when set up correctly. Pattern guys use them for increased torque, go faster guys use them to get as much rpm out of a engine designed for rpm's. Most of the go-faster bunch will start with a engine that is designed to scoot, a Jett LX or quickee engine, nelson etc. A Rossie and others do make rpm engines, their practical uses are generally limited to go fast stuff. The only overall engine out there cpable of idle and transition and multiple uses are the Jett LX series engines IMHO. A OS 46 quits around 14,500. A Jett 46LX or 50 quits at 18,000 plus. Now 4,000 does not seem like much, but in a racing application, your gonna get lapped flying the OS in most circumstances. Spend a few bucks on a viper, sig wonder, Diamond Dust ect, and strap on a good correctly sized engine. You will find out if you are a speed nut in short order. If you think you like it and have club pylon races, get a Hobbico "Avi-Star", make wing flat, chop to 40" add quickie landing gear, cowel in nose and a Webra 55, jett pipe and 9 X 10 apc. You and the gang will be shocked at the speed, and it will turn. We have 3 now in our Club racing them in our "Open class", allmost anything goes pylon racing. They kick vipers tail when they are powered by a typical sports engine, are cheap and durable. They are near quickee speeds with a Jett 60LX, and still land better than most. We are yet to scatter one in the air, the wings centers are not glassed for most, tailfeathers stock. A lot of the old 70's pattern designs will scoot with retracts and a good engine. The DC "Tusnami " still in production by someone else is also very quick with a good engine and retracts. You must remember, speed is relatively expensive. If you wanta go 200, stay with the known stuff such as Formula 40 or Q-500 for a relatively cheep go faster experience. Speed is not for everyone. Things happen quickly, a minor bo-bo will cost you around $1,000.00, more or less. When flying around the pylons 20 feet above the ground at 150 to near 200, you will either love the thrill, or flat hate it. Not much time to correct a little overbank, I guess about 1/20th of a second, or less. Back in the 70's, one of the guys around to beat was 80 something. Amazing, wonderfull old poop, loved by most all. He demonstrates how important set up skills are. ENJOY

Flyer95

My Feedback: (1)

Fullenght tuned pipes can be used on any modern twostroke engine and for any type of airplane where maximum performance is needed, as it can be used to gain more rpm or torque.
You can tune the engine with the pipe to give the best performance for hovering, 3D or speed or Pattern and IMAC type Extra, Yak, Edge.

The benefits of using a tuned quiet pipe are that you get atleast 20% more HP, and a whole lot more torque than the stock mufflers.
And noise level is sometimes even lower than before because now you are able to use a much bigger prop and also have a more efficient fourchamber silencer.

It is not that hard to tune a pipe and loads of information on tuning is available on the internet, read the good ones
Remember as long as the tuned lenght for the pipe is too long "uncut" and the prop is not too big it wont hurt anything but the performance gains are less.
A good prop for the OS55 when using a full pipe is the APC 13x6 @11500-12000rpm.

nsmjim

My Feedback: (52)

I have several delta wings. My best result is with a Jett sport .50 and a 9 X 6 prop. I'm considering a .91 (22 oz.) or a .46 (16 oz) ducted fnan engine, however, I'm finding that it may not perform better than my Jett engine??? Has anyone any idea what the results are from using a ducted fan engine on a delta wing with a prop??
Thanks,
Jim

Razor-RCU

My Feedback: (50)

My Sport Jett-50 was happiest on a 9x9 (Patriot) or 9x8 (Whiplash) and I ran I think an 8.75x8N on my Scatcat-

Hnestly, I have been flying for 25 years and I like pipes but these days the Jett-Stream and Ultrathrust mufflers are bolt and go, no hassle, no mounting issues, no pipe running into the wing etc. Best of all with most applications and sport models/ engines a full tuned pipe is a waste anyway...

I use Tower muffler, Ultrathrust, or Jett-Stream only these days--- My Novarossi came with a full-pipe but the wrong header so guess what, I am using a Jett-Stream instead--- bolt & go!