Tuned pipe OS 61FX??
10-08-2003, 11:20 PM
#1
Tuned pipe OS 61FX??
I've got a Macs pipe on my 61FX with a 1/2" header extension to clear the fuselage.
I've got it in a 6.75lb plane. It won't hover here because of the altitude. I'm running a 12-6 TF prop. I've tried a bunch of different props, and the lower pitch props seem to do better, but it's still not enough to hover this amount of weight.
I'm thinking about a tuned pipe for the engine.
Plane is a 40 size Giles. I want to develope as much thrust as possible. I don't need speed. So I think that I need to tune the engine for a bigger prop with lots of thurst. Maybe a 13-6 or a 13-8.
I'm totally clueless when it comes to tuned pipes. I've searched the archives here and still have the questions.
Do I tune it for max power on the test bench?
Does tuning for max RPM make the midrange get sloppy?
Can I tune for Torque?
Engine is rated at 1.9HP @ 16,000RPM. I'm lucky to get 11,000RPMs with the props I've tried. I'd like to get the engine up to 13,500--14,000RPM.
Any recommendations for the tuned pipe? Which one to buy and how to tune (torque--RPM?)
Thanks very much
I've got it in a 6.75lb plane. It won't hover here because of the altitude. I'm running a 12-6 TF prop. I've tried a bunch of different props, and the lower pitch props seem to do better, but it's still not enough to hover this amount of weight.
I'm thinking about a tuned pipe for the engine.
Plane is a 40 size Giles. I want to develope as much thrust as possible. I don't need speed. So I think that I need to tune the engine for a bigger prop with lots of thurst. Maybe a 13-6 or a 13-8.
I'm totally clueless when it comes to tuned pipes. I've searched the archives here and still have the questions.
Do I tune it for max power on the test bench?
Does tuning for max RPM make the midrange get sloppy?
Can I tune for Torque?
Engine is rated at 1.9HP @ 16,000RPM. I'm lucky to get 11,000RPMs with the props I've tried. I'd like to get the engine up to 13,500--14,000RPM.
Any recommendations for the tuned pipe? Which one to buy and how to tune (torque--RPM?)
Thanks very much
10-08-2003, 11:53 PM
#2
Senior Member
RE: Tuned pipe OS 61FX??
RCPilet,
Most large tuned pipes made in Europe (MVVS, Genesis), or Australia (Bolly), are tuned for lower RPM, with interest of reducing engine noise (so we can all keep our flying sites).
These pipes do not increase the engine's HP output, but rather allow it do develop its open exhaust numbers at much lower RPM levels.
Read this review: http://www.supertigre.com/engines/supg0235-man.html .
It allows the engine to spin a much larger diameter, efficient prop, that will develop much more thrust. If you want to hover your plane, a 14x4 will be much better than a 13x6, or a 12x8.
I understand your FX is getting the 11,000 RPM on the 12x6 without the pipe.
At sea level it would be only 1.07 HP. At your altitude it is much less.
Prop RPM does not change much with altitude. Power output is decreased, but so is air resistance, due to a lower air density. So they cancel each other out.
If you are getting this RPM on the Mac's tuned pipe, it is obviously, badly maladjusted.
Your engine is not getting on-the-pipe at all.
Most large tuned pipes made in Europe (MVVS, Genesis), or Australia (Bolly), are tuned for lower RPM, with interest of reducing engine noise (so we can all keep our flying sites).
These pipes do not increase the engine's HP output, but rather allow it do develop its open exhaust numbers at much lower RPM levels.
Read this review: http://www.supertigre.com/engines/supg0235-man.html .
It allows the engine to spin a much larger diameter, efficient prop, that will develop much more thrust. If you want to hover your plane, a 14x4 will be much better than a 13x6, or a 12x8.
I understand your FX is getting the 11,000 RPM on the 12x6 without the pipe.
At sea level it would be only 1.07 HP. At your altitude it is much less.
Prop RPM does not change much with altitude. Power output is decreased, but so is air resistance, due to a lower air density. So they cancel each other out.
If you are getting this RPM on the Mac's tuned pipe, it is obviously, badly maladjusted.
Your engine is not getting on-the-pipe at all.
10-09-2003, 12:03 AM
#3
RE: Tuned pipe OS 61FX??
I know that I'm suffering badly with the RPMs. I've got it adjusted as good as its gonna get. I have excellent transition and the high end it about 3-4 clicks rich.
I've been at Tower Hobbies looking at tuned pipes. Looks like the only ones making a tuned pipe and header for this engine is Macs.
I guess I'll get one of these tuned pipes/header and give it a try. The black Macs Quiet pipe that I have on it is not doing the trick.
I've been at Tower Hobbies looking at tuned pipes. Looks like the only ones making a tuned pipe and header for this engine is Macs.
I guess I'll get one of these tuned pipes/header and give it a try. The black Macs Quiet pipe that I have on it is not doing the trick.
10-09-2003, 06:53 AM
#4
RE: Tuned pipe OS 61FX??
Check out the pre-tuned system #1973....it might be
your best bet, and you won't have to cut the header
and mess with the length....
http://www.macspro.com/pretunedsystem.asp
your best bet, and you won't have to cut the header
and mess with the length....
http://www.macspro.com/pretunedsystem.asp
10-09-2003, 03:48 PM
#5
RE: Tuned pipe OS 61FX??
The link doesn't work. I even searched for Macs on google and hit that link------no luck. Maybe the Macs site is down.
Can anyone tell me HOW to tune this? I know that you cut it and look for higher RPM; but---- do I tune for Max RPM or do I put a big prop on it as was suggested and tune for Max with that prop?
Can anyone tell me HOW to tune this? I know that you cut it and look for higher RPM; but---- do I tune for Max RPM or do I put a big prop on it as was suggested and tune for Max with that prop?
10-09-2003, 04:05 PM
#6
Senior Member
RE: Tuned pipe OS 61FX??
RCPilet,
When the tuned pipe is too long to be optimized, the engine is always on-the-pipe, but not optimized for power.
Your engine is making a great deal LESS than it should with the standard muffler.
A tuned pipe, when too long, doesn't help much, but you have a situation that your setup is making much less than a standard muffler.
Are you sure you didn't put the pipe to help a low power situation, resulting from a badly done break-in (as in four-cycle rich)?
When the tuned pipe is too long to be optimized, the engine is always on-the-pipe, but not optimized for power.
Your engine is making a great deal LESS than it should with the standard muffler.
A tuned pipe, when too long, doesn't help much, but you have a situation that your setup is making much less than a standard muffler.
Are you sure you didn't put the pipe to help a low power situation, resulting from a badly done break-in (as in four-cycle rich)?
10-09-2003, 06:11 PM
#7
RE: Tuned pipe OS 61FX??
I broke the engine in properly. I'm pretty good with engines. I know how to break in an engine; wheather it be an ABC or a ringed engine or even a gasser. I'm not new to this stuff.
This engine has been a strong runner for a few years now. No lean runs and I've always taken good care of it with plenty of afterrun oil when done flying for the day. No crashes.
I discovered what's wrong. I used a 1/2" spacer to move the muffler out away from the engine to clear the fuselage.
That 1/2" spacer is ruining the tune on the Macs pipe. I've intorduced a variable thats not meant to work with this pipe. It should be bolted directly to the cylinder----not spaced out 1/2"
I've got to either get the Macs pipe bolted directly to the engine again or get a tuned pipe for the engine.
I'm primarily concerned with how to tune a pipe for the engine.
I've been doing some reading; and it seems that the best way to tune a pipe for this aplication is to buy the prop, plug, and fuel that I intend to use and then tune the pipe to swing that prop as best it can.
Thanks for the replies.
This engine has been a strong runner for a few years now. No lean runs and I've always taken good care of it with plenty of afterrun oil when done flying for the day. No crashes.
I discovered what's wrong. I used a 1/2" spacer to move the muffler out away from the engine to clear the fuselage.
That 1/2" spacer is ruining the tune on the Macs pipe. I've intorduced a variable thats not meant to work with this pipe. It should be bolted directly to the cylinder----not spaced out 1/2"
I've got to either get the Macs pipe bolted directly to the engine again or get a tuned pipe for the engine.
I'm primarily concerned with how to tune a pipe for the engine.
I've been doing some reading; and it seems that the best way to tune a pipe for this aplication is to buy the prop, plug, and fuel that I intend to use and then tune the pipe to swing that prop as best it can.
Thanks for the replies.
10-09-2003, 06:20 PM
#8
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RE: Tuned pipe OS 61FX??
It would be easiest for you to get the MACS pre-tuned setup. Just bolt on and go. Also get an APC 13x4W if you want to 3D and hover. Your hover will be much more stable on this prop. If you are getting 15k rpm you might want to try a 14x4w also!
10-10-2003, 01:54 AM
#9
Senior Member
RE: Tuned pipe OS 61FX??
RCPilet,
If your engine has a few years of work behind it, it may be too worn to make good power. The .61 was tested; you can see it at this web site: http://www.osengines.com/reviews/osmg0561-rcr.html .
Bolt on power is good for engines that are in a good physical condition. A tuned pipe does not replace an overhaul. It is not a 'cure all'.
If your engine has more than 50 hours, you can suspect it may not be in very good shape.
With the glow plug removed, does the piston still "catch", or squeak at TDC?
If not, you could be in for a rebuild.
Do you remember it ever having better performance in past days?
If your engine has a few years of work behind it, it may be too worn to make good power. The .61 was tested; you can see it at this web site: http://www.osengines.com/reviews/osmg0561-rcr.html .
Bolt on power is good for engines that are in a good physical condition. A tuned pipe does not replace an overhaul. It is not a 'cure all'.
If your engine has more than 50 hours, you can suspect it may not be in very good shape.
With the glow plug removed, does the piston still "catch", or squeak at TDC?
If not, you could be in for a rebuild.
Do you remember it ever having better performance in past days?
10-10-2003, 02:54 AM
#10
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RE: Tuned pipe OS 61FX??
I've just bought a "purple pipe deal" for my 61 FX from justengines.co.uk in England. 60 GBP inc. air it cost me, and apart from being purple it's a replica Hatori three baffle pipe. It's very light and the pipe deal includes all couplers, header, mount, silicone, pressure tap etc.
The engine has been reported to rev over 10.000 RPM with this pipe and a 13x10 APC! Not had the chance to try mine so I can't vouch for it just yet. Looking forward to try though!!
The included instructions for tuning all demanded a knowledge of exhaust timing and intimate knowledge of the pipe's interior. Not something I'm willing to get into but get a tach and a length of silicone and off you go! Unless you plan for 16.000 RPM pylon racing you'll be fine. Leaving the pipe longish will get you a decent power increase anyhow provided you don't underprop it. A 12x6 is VERY small for this engine! For hovering I'd consider a 13x8. I've used a 13x6 APC and performance was very poor. It was all noise and no thrust. I favour a 12x10 with the stock muffler which provides both good acceleration and speed but I'll definately move to a 13x10 now that I have the pipe.
The engine has been reported to rev over 10.000 RPM with this pipe and a 13x10 APC! Not had the chance to try mine so I can't vouch for it just yet. Looking forward to try though!!
The included instructions for tuning all demanded a knowledge of exhaust timing and intimate knowledge of the pipe's interior. Not something I'm willing to get into but get a tach and a length of silicone and off you go! Unless you plan for 16.000 RPM pylon racing you'll be fine. Leaving the pipe longish will get you a decent power increase anyhow provided you don't underprop it. A 12x6 is VERY small for this engine! For hovering I'd consider a 13x8. I've used a 13x6 APC and performance was very poor. It was all noise and no thrust. I favour a 12x10 with the stock muffler which provides both good acceleration and speed but I'll definately move to a 13x10 now that I have the pipe.
10-10-2003, 04:19 AM
#11
Senior Member
RE: Tuned pipe OS 61FX??
Jon,
For hovering you need a large diameter prop with a low pitch. This is the reason most .40-.53 3-D flyers favor the APC 12.25x3.75, or the 12x4.
A prop with a pitch of 8 will give you a very high top speed, but in a hover situation, most of the blade area is in a stalled condition, not producing any real thrust.
The 12x6 is better for hovering than a 13x8, as you wrote.
If you want a hovering prop with the same load as a 13x8, try a 14x6, or a 15x4.
The OS.61FX is far from being a real powerhouse (with the standard silencer).
The 13x8 is a really heavy load on it anyway.
The OS.61FX was found, by Dave Gierke in the MAN 5/2003 .60s shootout, to be inferior in power (and idle, and transition), even to its low budget, OS.65LA sibling.
For hovering you need a large diameter prop with a low pitch. This is the reason most .40-.53 3-D flyers favor the APC 12.25x3.75, or the 12x4.
A prop with a pitch of 8 will give you a very high top speed, but in a hover situation, most of the blade area is in a stalled condition, not producing any real thrust.
The 12x6 is better for hovering than a 13x8, as you wrote.
If you want a hovering prop with the same load as a 13x8, try a 14x6, or a 15x4.
The OS.61FX is far from being a real powerhouse (with the standard silencer).
The 13x8 is a really heavy load on it anyway.
The OS.61FX was found, by Dave Gierke in the MAN 5/2003 .60s shootout, to be inferior in power (and idle, and transition), even to its low budget, OS.65LA sibling.
10-10-2003, 07:43 AM
#12
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RE: Tuned pipe OS 61FX??
Another alternative is a Perry pump and larger Perry carb as at the higher altitude the larger carb bore will allow more airflow. I have one on an older OS61 and a big jump in HP.
10-22-2003, 10:02 PM
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RE: Tuned pipe OS 61FX??
I have the tuned pipe for this engine in the garage, was gonna put it up on ebay, just the pipe, not the header. Changed it over to a quiet pipe, the noise was a tad too much for the older fellas at the field, the change in RPMs didn't mattter for what I had it on. ifya are interested, drop me a line at [email protected] it's been used for 2 yrs and is in fine shape. Take 20 offa Macs price and that's what I'd let it go for plus shipping. Anyone interested, drop me a line.
10-22-2003, 11:51 PM
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RE: Tuned pipe OS 61FX??
I have been using the Performance Plus tuned silencer on my OS 61fx's for several years. 12-6 APC 5 1/2 lb. "Super Hots", virtually unlimited vertical! Easy on, no tuning, and pick up 1K to 1.5K RPM like magic! A lot lighter than a pipe hanging out the side!
