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Pipe Setup Question

Old 10-26-2008, 02:56 PM
  #1  
brjensen71
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Default Pipe Setup Question

This is my first time setting up a pipe. I have went through normal tuning, gradually shortening the header getting higher and higher RPM. Double checking it with different props.

I am now to the point that I can not shorten the header pipe, but still there is more potential (I slide the pipe over the header to gain even more )

My question is, can I shortened inlet side of the pipe without destroying the pipe? or the benefit of the pipe?
Old 10-26-2008, 03:34 PM
  #2  
pe reivers
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Default RE: Pipe Setup Question

shorten the header instead. That seems more logical to me.
Old 10-26-2008, 03:49 PM
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Default RE: Pipe Setup Question

Pe, I think he cannot shorten the header any more.

To TS, yes you can trim some off the inlet of the pipe as long as you do not start trimming the cone itself away.


Mark
Old 10-26-2008, 04:03 PM
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pe reivers
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Default RE: Pipe Setup Question

Hmmm...
If you can slide the pipe over the header, there still seems some header left methinks?
High rpm engines have the pipe starting right at the exhaust port outlet. The manifold then is just long enough to allow a sealing ring, butno more. In a side exhaust engine of course one needs a little more header to get around the bend
Old 10-26-2008, 07:14 PM
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brjensen71
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Default RE: Pipe Setup Question

Sorry, I should have provided a little more detail.

It is a side exhaust engine, I have about a 1/2" before the header will be trimmed back to the radius. Will I run into issues once I start trimming into the radius?
Old 10-26-2008, 09:54 PM
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downunder
 
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Default RE: Pipe Setup Question

Disclaimer ...I've only had some experience setting up a pipe for low rev applications. From what you're saying it seems that you may have a pipe that's designed for low revs in which case it's possible you can't shorten it enough if you're after very high revs. My pipes are on the order of 17-18" from the piston face to the first baffle but they're designed to work in the ~10,000 range.
Old 10-27-2008, 05:57 AM
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Flyboy Dave
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Default RE: Pipe Setup Question

....yep, you can trim some off the front of the pipe if necessary. In this application I
was limited from shortening the header because of the pressure nipple. I had slid
the pipe as far forward as I could. The Zip-tie is to keep the pipe away from the
nipple.

If the pipe will slide over the header , or the header will slide over the pipe,you
can slide one over the other and shorten the overall length with out cutting it right away.

You can see how short my system is to get maximum RPM out of it, 18,100 on the ground.
The engine still has the original plug in it I got with the engine years ago.

I have heard it said that you should not slide one pipe over the other. It doesn't matter,
you can do it....no problem.

FBD.
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Old 10-27-2008, 12:11 PM
  #8  
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Default RE: Pipe Setup Question

OTOH you can see how long the system is on my Irvine 40RLS to run around the 10,000 mark.
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Old 10-27-2008, 12:17 PM
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Flyboy Dave
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Default RE: Pipe Setup Question

....yep, good example, Brian.... [sm=thumbup.gif]

....long for torque....short for RPM.

FBD.
Old 10-27-2008, 02:48 PM
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brjensen71
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Default RE: Pipe Setup Question

OK, time for more details, I starting to wonder if the pipe I have is sized correctly. The goal is to get max RPM on high pitch prop.

The engine is a Super tigre 90, it has had boost port timing raised to match the inlet ports. The inlet and boost ports have smoothed. The crank timing changed to gain more RPM, and the piston modified uncover the ports.

I have been using a 15cc Macs pipe and header, and an APC 10X10 on 10% nitro fuel.

So far I have been able to get 15300 rpm from the motor.

I have included my data so far
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Old 10-27-2008, 03:11 PM
  #11  
ChrisAttebery
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Default RE: Pipe Setup Question

Is it the MAC's airplane pipe or marine pipe? I ran the marine pipes all the way down to 12.5" on my boats. They have shorter/steeper cones and are designed for higher RPM setups.

In a perfect world your like the header and pipe to be the same size at the joint and have a perfectly smooth transition, but they will work just fin if you start cutting into the cone slightly. I think the reliability penalty from having them mismatched would be higher than the performance penalty. You'll burn through couplers more often if they are mismatched.
Old 10-27-2008, 03:51 PM
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Default RE: Pipe Setup Question

its the airplane pipe that I am using
Old 10-27-2008, 04:24 PM
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Flyboy Dave
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Default RE: Pipe Setup Question

....leave it where it is...you are cranking slightly higher than a Jett 90L.

I don't think you can get any more out of it.

A Jett 90L will crank 15K flat with an APC 11-8.

FBD.
Old 10-27-2008, 05:29 PM
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pe reivers
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Default RE: Pipe Setup Question


ORIGINAL: brjensen71

OK, time for more details, I starting to wonder if the pipe I have is sized correctly. The goal is to get max RPM on high pitch prop.

The engine is a Super tigre 90, it has had boost port timing raised to match the inlet ports. The inlet and boost ports have smoothed. The crank timing changed to gain more RPM, and the piston modified uncover the ports.

I have been using a 15cc Macs pipe and header, and an APC 10X10 on 10% nitro fuel.

So far I have been able to get 15300 rpm from the motor.

I have included my data so far
what details?
you still do hold back the all important information that is needed to evaluate your problem, IF there is a problem. I do not like being led by the nose.
Old 10-27-2008, 08:23 PM
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brjensen71
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Default RE: Pipe Setup Question

I apolagize, I don't mean to lead anybody on.

For my own entertainment, I am trying to see if I can make a ST90 turn a APC10X10 prop 16,000. While it may not possible or practical, and I may spend three times as much as buying a Jett 90lx, its all in the fun of trying.

The piston modification were to the skirt to uncover the ports when the piston in at BDC. I'll try get pictures of what I have done posted





Old 10-27-2008, 09:13 PM
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Default RE: Pipe Setup Question

ORIGINAL: brjensen71
The piston modification were to the skirt to uncover the ports when the piston in at BDC.
I presume you mean something like this? It's a worthwhile mod (if only for helping cool the small end of the rod and piston) and I don't know why it isn't done on more engines. Apart from the cost of extra machining anyway.
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Old 10-28-2008, 09:12 AM
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pe reivers
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Default RE: Pipe Setup Question


ORIGINAL: brjensen71

I apolagize, I don't mean to lead anybody on.

For my own entertainment, I am trying to see if I can make a ST90 turn a APC10X10 prop 16,000. While it may not possible or practical, and I may spend three times as much as buying a Jett 90lx, its all in the fun of trying.

The piston modification were to the skirt to uncover the ports when the piston in at BDC. I'll try get pictures of what I have done posted





I jumped to conclusions too soon.
Maybe 16000 rpm is too low to deliver the 2.5 hp that the prop requires at those rpm. It can be done I think, but components should match the tune to a T.
The best is, when there is ample header length in relation to pipe cone length. A very short header with a long cone probably will not get you there.
Someone with boating experience using .90 engines may have good ideas about the pipe/header combo to use.
Old 10-28-2008, 03:17 PM
  #18  
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Default RE: Pipe Setup Question


ORIGINAL: pe reivers


ORIGINAL: brjensen71

I apolagize, I don't mean to lead anybody on.

For my own entertainment, I am trying to see if I can make a ST90 turn a APC10X10 prop 16,000. While it may not possible or practical, and I may spend three times as much as buying a Jett 90lx, its all in the fun of trying.

The piston modification were to the skirt to uncover the ports when the piston in at BDC. I'll try get pictures of what I have done posted





I jumped to conclusions too soon.
Maybe 16000 rpm is too low to deliver the 2.5 hp that the prop requires at those rpm. It can be done I think, but components should match the tune to a T.
The best is, when there is ample header length in relation to pipe cone length. A very short header with a long cone probably will not get you there.
Someone with boating experience using .90 engines may have good ideas about the pipe/header combo to use.
You are right...good idea! Some of the boat guys have tried it all! Capt,n
Old 10-28-2008, 06:30 PM
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brjensen71
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Default RE: Pipe Setup Question

This is a first stage of my modifications

I raised the case exhaust port, this was to uncover the port in the sleeve. It appeared to be a casting problem

I deburred the inlet port at the crank, a burr was protruding into the port

On the case I lowered a raised spot directly below the boost port. the pictures do not the changes well.

I filled the crank with JB weld and smoothed in the inlet side edges, and moved the rear edge back so it was not protruding in the case opening.

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Old 10-28-2008, 06:45 PM
  #20  
brjensen71
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Default RE: Pipe Setup Question

My stage 2 modifications were to smooth the lower side of the boost port. And I changed the crank port timing

From :
Open @ 135 deg btdc, closed @ 49 deg. ATDC duration of 184
To:
Open @ 143 deg btdc, closed @ 56 deg. ATDC duration of 199

Sorry, no after pictures of the crank


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Old 10-28-2008, 07:27 PM
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brjensen71
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Default RE: Pipe Setup Question

My Stage 3 mods:

Raised the boost port timing to match the inlet port timing

Smoothed the flow on the inlet ports

shortened the piston skirt on the boost port side by .080", this was done to try uncover the boost port at BDC

narrowed the piston skirt on the exhaust port side and raised the reliefs by .020" to .030", this was done to uncover the inlet ports at BDC

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Old 10-28-2008, 07:46 PM
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Default RE: Pipe Setup Question

While using the MDS muffler with and adapter, I did get modest improvements each of the modifications, see my earlier post with the test data. Once I started using the Pipe RPM started to pick up.

I did start using an OS carb, not because I dislike ST carbs, I can make them perform with any muffler ( I use the tricks on pe reivers'es website ). I simply get more RPM's at max throttle, and I can use it with a remote needle ( BVM type ).

Now, based on the feedback I am getting, I am wondering if I need a different pipe.

I included a picture of my test stand, you can see the MDS muffler and adapter.

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Old 11-21-2009, 08:24 PM
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Default RE: Pipe Setup Question

Its been a while, but I think I finally finished my project. I ended up using a 13cc marine pipe and changed the piston modifications slightly. With a OS91 heli carb I was able to obtain a stable 15700 RPM with an APC 10X10 prop on 10% nitro on the test stand. I am going to re-test this motor with my modified ST2300 carb, but at the current rate of progess this could be years away.

The most interesting part is I tried an APC 11X12 prop (suggestion from another RCU contributer) and got 13700 RPM. I space the pipe back 3/8" and got a more stable 13500". This gives a prop speed of 153 MPH compared to 148.7 with the 10X10 prop at 15700 RPM and is displacing about 25% more volume than the 10X10 prop.

Now I have to get around to putting it on an airplane

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Old 11-22-2009, 09:44 AM
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Default RE: Pipe Setup Question

I ran the engine at 7500 rpm!
Try lower rpm, you will not be disappointed. The engine sweet spot is around 12000 rpm, so that should be about the highest in flight rpm to aim at.

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