I would be more concerned that the baffle topped piston would negate much of the pipes benefits.

Timings are on the old Stalker Modusa site http://www.stalker-modusa.com/index3.htm but you have to navigate your way through Engines then down the page to "detailed engine specs". Later engines such as the 61 2/4 RE aren't shown though.

Looks like the exhaust timimg is 136 degree. but would it work with the baffled piston?  What if the baffle is removed, and the notch in the head filled in?

Tuned exhausts work with any type of engine even 4 stroke engines. The difference being what the tuned exhaust system is designed to accomplish. Tuned exhausts have a far higher effect on traditional 2 stroke engines because they effectively adjust the exhaust timing of the motor. Baffle piston engines still benefit from tuned exhaust systems with the exception that the pressure and sonic waves can not influence the intake fuel air charge as much as a flat top motor. Note I say as much. It still helps clear the combustion chamber and hold in fresh fuel air in the combustion chamber.

You will have to play with tuned length as well and perhaps the distance and locations of internal baffles and cone angles to perfect the system to get the run you desire. If you are the type who loves to experiment and don't mind the cost of trying several types of currently available tuned pipes, then go for it. How ever if you are looking for out of box solution, it is wiser to focus your efforts on a proven engine and pipe combination.

But we are not in this forum with anything but unthrottled stunt engines in mind and although I have seen pipes on cross flow motorcycle engines and all sorts of different engines outside of all this, you would have to bear in mind that all of the successful ones had some form of speed control with a throttle.

So what we have here is a purpose built engine that uses the 4-2 system and a baffle as a means of speed control and then we are considering the addition of another speed control system with a pipe?
(Makes no sense to me.)

I had a talk with an experienced stunt flier here in Oz last night about this and he can can only recall this being partially successful with crutches like 15% nitro and much higher compression ratios so there goes your nice 4-2 break right out the window!

A tuned system in our application is used for more than just speed control. It is also designed or should be, to deliver maximum power at the rpm's suitable for CLPA.

I had a talk with an experienced stunt flier here in Oz last night about this and he can can only recall this being partially successful with crutches like 15% nitro and much higher compression ratios so there goes your nice 4-2 break right out the window!

Well, the 4-2 is not something I was looking for anyway.  I would rather have a constant 4-4 pipe run like around 9300rpm or so.  but not sure removing the baffle is all it needs to work. 

So what we have here is a purpose built engine that uses the 4-2 system and a baffle as a means of speed control and then we are considering the addition of another speed control system with a pipe?
(Makes no sense to me.)

   The baffle is not there for speed control, or at least not intentionally. It's there to ensure that the incoming charge goes up to the top of the cylinder and thus scavenges the exhaust. If you didn't have that, the charge just shoots across the top of the piston and out the exhaust. Schneurles don't do that only because the ports are aimed up to the top already.

    In fact, if you want to detune a baffle-piston engine, you sometimes need to reduce the baffle height (although it's kind of a kludge in most cases).

     Brett

I guess that leads to the question..    Would there be much performance gain as in power & speed regulation with the baffled piston/piped set-up ?  or better off using the stock muffler.

  Of course it would likely be better regulated with a pipe than an untuned muffler. Whether that's a useful thing with the average baffle-piston engine (that tend to be weak to begin with, and particularly for "stunt engines") is another story. The effects should be no different, and people have certainly done it, but there's no very good reason to do it. If you tune it to attempt to correct for the power deficit, you tend to lose the regulation effect.

    I was mostly commenting on the idea that the type of scavenging was somehow relevant to the effects of the pipe, which for the most part, it is not.

     Brett

I run pipes and have a Stalker 61 as well. Love pipes but the Stalker 61 is one engine that I would not use them on. Its power is very well regulated with the stock muffler. It will never be the powerhouse that a PA 61 is but is a fine stunt engine in its own right. I'd' run it stock and save the piped experimentation for an engine that is known to benefit from pipes...VF40/46, Ro-Jetts, PA's, Enya 61 RE etc. 

 
    I was mostly commenting on the idea that the type of scavenging was somehow relevant to the effects of the pipe, which for the most part, it is not.

     Brett

Hi Brett,
  I am laboring under the impression that the returning wave in an efficient tuned system wants to interact with the transfer ports by drawing the charge from the lower crank case, and to do this it must 'see' the ports in question.

The issue with an obstructing baffle is just that, it obstructs the view of the wave and thus negates much of its effect in that area - so I suppose that the argument revolves around how efficient you want the system to be.

Thanks.

Hi Brett,
  I am laboring under the impression that the returning wave in an efficient tuned system wants to interact with the transfer ports by drawing the charge from the lower crank case, and to do this it must 'see' the ports in question.

The issue with an obstructing baffle is just that, it obstructs the view of the wave and thus negates much of its effect in that area - so I suppose that the argument revolves around how efficient you want the system to be.

  Low pressure at the exhaust is low pressure at the exhaust, it's going to have about the same effect. Of course the scavenging is less efficient, but it's less efficient with a muffler, too.

    Brett

Here are all the data:

I remove the baffel out of the standard 4-2-2 anyway..

Gets much more constant runs.

Infact for the Engine I ran at the US NATS, I had shortened the pipe by 1 Inch and removed the baffle.

I'm also curious which baffle you're referring to?  (piston or muffler)

Possibly should have read the entire thread 1st....

I did'nt realise you were referring to the Piston Baffle.. Id recommend NOT removing that..

Mine was in reference to the Muffler.