stunthanger.com
Engine basics => Engine set up tips => Topic started by: Joe Yau on August 10, 2011, 03:57:02 PM
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Just wondering if anyone know the exhaust timing for the Stalker.61 RE 4-2. and would it work with a pipe set-up?
Thanks in advance.
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I would be more concerned that the baffle topped piston would negate much of the pipes benefits.
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Stalker timing for most is on one of the Stalker sites , which one ? good question. Pommy or Ruski , I fink .
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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.
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The only stunt engine I know of that has a baffle top piston and has what looks like a magic muffler or short quarter wave style pipe is the Cyclon 60 from Russia.
I think that a 4-2 run is an anathema to pipes.
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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?
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I seem to remember reading a report in an older issue of stunt news, a report by Pickard in OZ. He had done some work with a Stalker .61RE on a pipe. If memory is correct, it worked, but your still better offf with a dedicated pipe engine. H^^
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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.
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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!
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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.
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Hi Pete,
I have to ask here, have you ever seen a successful stunt engine with a baffle top piston and a tuned pipe?
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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. D>K
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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.
Not at all, you want it nowhere near peaked out. You want it to be tuned to lower RPM than you are going to run, so it will regulate the run. Getting power is a non-issue, they can all put out far more than you could ever use. Just try running a 40VF on open exhaust sometime and I guarantee you will see what I mean.
Brett
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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
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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.
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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
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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.
Brett
Thanks for clarifying that.H^^ So,does that mean it'll work to some degree as is? and is it worthwhile doing? or the effect will probably be minimum.
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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. 8)
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Honestly here, if any pipe is going to be considered I would try an alloy MVVS tuned silencer, part number 3248.
They are very forgiving with the state of tune should yield about a 10% increase in power (and they aren't that expensive.)
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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.
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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.
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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
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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.
PJ...Did you mean to imply that you removed the baffle off the piston crown, or the baffle out of the muffler? So fa', all mention of baffle has meant piston baffle. If you don't mind clarifying this point... ???
I recall some Fox Combat hop-up article in the dim and murky past that said to file a small amount off the top of the piston baffle. The rpm peak would increase until it reached optimal, after which further shortening the baffle would make the engine less enthused about 2 cycling, turning it into a 4-cycling combat engine. That's just from memory, tho. I think the article would have been Larry Scarinzi's article on the Blitz combat design in MAN, about 1964.
D>K Steve
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Here are all the data:
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Just a note on the info provided above. The two figures shown for the 61RE port timings are for the two versions. The bottom figures of 110/130 are for the first engines which were called the 2-2 meaning they'd run at a constant rev (whether 2 stroking or 4 stroking). My engine (a 2-2) actually measures at 116/130. The engines with the 120/140 were called 2-4 (or maybe 4-2, I don't remember now) meaning they'd give a 4-2-4 break. This rather surprised me because I'd always assumed an engine with low blow down was more inclined to give a 4-2 break.
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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) ???
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P.J. said he removed the baffle 'out' of (as in it is indeed a removable item), and rounds up the post by mentioning the exhaust so its my best guess that its the 'exhaust' baffle he is referring to!
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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.