Tuned Pipe Stinger Diameter

Intlwaters

Help Support Intlwaters:

This site may earn a commission from merchant affiliate links, including eBay, Amazon, and others.

Duke Mordja

Well-Known Member
Joined
Jan 15, 2005
Messages
754
What are the characteristics of having too small or too large of a stinger diameter on a 67 or 80 engine? What to look for??

Thanks in advance,
 
If I could add along with to small or to large, what about stinger being to short or to long as well.
 
Duke if you go down the page a few posts "67/80 pipe stinger " Jim Allen explains.

David
 
Last edited by a moderator:
John,

Not really any issues. Kind of wondering if motors are limited in RPM by having too much "back pressure". I read Jims post and I have to educate myself and measure my setup to understand it better.

Ran the twin with with my 80's and new props. All else the same from my 67's. It is an absolute beast now.
default_ph34r.png
default_ph34r.png
default_ph34r.png


I am just wondereing if taking my reducer off of the CMB pipe is necessary and any benefit. I haven't noticed any piston issue. I had stinger down to 0.415" for the 67's. I believe stock diameter is 0.450"

It is a task to remove the reducer (4 set screws) LOL.

I think I may just tighten the head clearance a little more and give her some more fuel.

And do a little more testing.

I do not like changing things if there is no need. Driveability is my goal. Need to finish heats.

Thanks

.
 
Last edited by a moderator:
Hi Duke,

The basics on stingers for me are not so much doing anything with the length but the I.D. - going smaller to get more back pressure for fuel delivery. It usually comes with more heat in the engine as well. Driveability and servivability - I'm still having carb barrel issues - can't seem to keep them in - I'm on hold now waiting for moded carbs with the barrel held in with snap rings. I have one that I got from Doc Turner - works great never an issue, it was done by Mark Bullard. As always Mark's work is flawless and durable!

John
 
I think I am going to leave well enough alone and burn some Nitro. The twin is a blast to drive and it doesn't blow off the water nearly as much as my scale.

Something to "tinker" with.
 
John,

I am ready to start testing "flawless and durable".

When are you going to have some free time?

Duke,

I think the .415" stinger diameter is going to be fine for your set up.

I may have a better set of propellers than your H-48's?

It is important to find the right set of propellers that make the boat

more responsive for heat racing. Duke give me a call when you have time.

Thanks For Reading Fellas,

Mark Sholund

231-590-3023
 
John,

I am ready to start testing "flawless and durable".

When are you going to have some free time?

Duke,

I think the .415" stinger diameter is going to be fine for your set up.

I may have a better set of propellers than your H-48's?

It is important to find the right set of propellers that make the boat

more responsive for heat racing. Duke give me a call when you have time.

Thanks For Reading Fellas,

Mark Sholund

231-590-3023
Hi Mark,

My time is always free now days - my hourly rate got so high no one could afford it so I just work for free!! Are you thinking of testing on a weekend or? Let me know, my projects here are easy to put on hold periodically.

John
 
Stinger length & stinger inside diameter both will effect the engine's operating temperature. However, increases or decreases in diameter will have a much more pronounced effect on the engine's operating temperature than increases or decreases in stinger length. In order for any tuned pipe to be able to give a high boost pressure, without a heat problem, the tuned pipe being used "MUST" have an adequate volume compared to the displacement of the engine. A factor of approximately 26+ times for nitro engines to approximately 32+ times for gas engines will allow the use of longer, smaller internal diameter stingers.

Consider the fact that the stingers I use on my 26 cc QD engines are .4062" ID X 5.5" in length. The gas engine's operating temperature is approximately twice what would be found in a nitro engine of the same size. I use a toroidal head with a volume of less than 1 cc & a deck clearance of 002". The measured tuned pipe internal pressure is 120" of water or 4.336 psi. at WOT.

Jim Allen
 
Last edited by a moderator:
Stinger length & stinger inside diameter both will effect the engine's operating temperature. However, increases or decreases in diameter will have a much more pronounced effect on the engine's operating temperature than increases or decreases in stinger length. In order for any tuned pipe to be able to give a high boost pressure, without a heat problem, the tuned pipe being used "MUST" have an adequate volume compared to the displacement of the engine. A factor of approximately 26+ times for nitro engines to approximately 32+ times for gas engines will allow the use of longer, smaller internal diameter stingers.

Consider the fact that the stingers I use on my 26 cc QD engines are .4062" ID X 5.5" in length. The gas engine's operating temperature is approximately twice what would be found in a nitro engine of the same size. I use a toroidal head with a volume of less than 1 cc & a deck clearance of 002". The measured tuned pipe internal pressure is 120" of water or 4.336 psi. at WOT.

Jim Allen
Jim, the pipe volume that you mention, is it measured from the exhaust port to the end of the stinger or is it the volume of just the coned sections?
 
Stinger length & stinger inside diameter both will effect the engine's operating temperature. However, increases or decreases in diameter will have a much more pronounced effect on the engine's operating temperature than increases or decreases in stinger length. In order for any tuned pipe to be able to give a high boost pressure, without a heat problem, the tuned pipe being used "MUST" have an adequate volume compared to the displacement of the engine. A factor of approximately 26+ times for nitro engines to approximately 32+ times for gas engines will allow the use of longer, smaller internal diameter stingers.

Consider the fact that the stingers I use on my 26 cc QD engines are .4062" ID X 5.5" in length. The gas engine's operating temperature is approximately twice what would be found in a nitro engine of the same size. I use a toroidal head with a volume of less than 1 cc & a deck clearance of 002". The measured tuned pipe internal pressure is 120" of water or 4.336 psi. at WOT.

Jim Allen
Jim, the pipe volume that you mention, is it measured from the exhaust port to the end of the stinger or is it the volume of just the coned sections?
Tim,

Measure from the exhaust port to the end of the stinger. Also keep in mind that the area from the exhaust port window to the tuned pipes header should decrease. This part of the tuned pipe should also be pointed in a downward direction, approximately 10* to 15*. The beginning of the tuned pipes header should not be straight, as is found on all of our toy engine stuff, but tapered also, approximately 2* to 3*. Remember, any device that is similar to a tuned pipe will work to some extent. A good ball park figure to look for when calculating the stingers length would be, it's length should be 13.5+ times it's ID, if the pipes volume is the correct amount.

I measured many tuned pipe internal pressures, while the engine is operating, with a Wika water gauge, capable of reading 0 to 200 inches of water in 5 inch increments. Very Interesting stuff found when comparing a good & not so good chamber????

JA
 
Jim Allen are you the Jim Allen RC Pylon racer in Dubai

just reading Model Aviation

marty
Marty,

I'm the Jim Allen who works for Mike Langlois at Aero Precision Machine Inc. building & repairing the Nelson Q-40 pylon racing engines sold world wide. However, I know the Jim Allen you are referring to & he does fly pylon racing model aircraft. In fact, he was at the recent Pylon racing contest held at Julian, NC this past week end. I was also there as one of the turn judges on pylon #1.

Jim Allen
 
Jim Allen are you the Jim Allen RC Pylon racer in Dubai

just reading Model Aviation

marty
Marty,

I'm the Jim Allen who works for Mike Langlois at Aero Precision Machine Inc. building & repairing the Nelson Q-40 pylon racing engines sold world wide. However, I know the Jim Allen you are referring to & he does fly pylon racing model aircraft. In fact, he was at the recent Pylon racing contest held at Julian, NC this past week end. I was also there as one of the turn judges on pylon #1.

Jim Allen
 
Jim Allen are you the Jim Allen RC Pylon racer in Dubai

just reading Model Aviation

marty
Marty,

I'm the Jim Allen who works for Mike Langlois at Aero Precision Machine Inc. building & repairing the Nelson Q-40 pylon racing engines sold world wide. However, I know the Jim Allen you are referring to & he does fly pylon racing model aircraft. In fact, he was at the recent Pylon racing contest held at Julian, NC this past week end. I was also there as one of the turn judges on pylon #1.

Jim Allen
 
Stinger length & stinger inside diameter both will effect the engine's operating temperature. However, increases or decreases in diameter will have a much more pronounced effect on the engine's operating temperature than increases or decreases in stinger length. In order for any tuned pipe to be able to give a high boost pressure, without a heat problem, the tuned pipe being used "MUST" have an adequate volume compared to the displacement of the engine. A factor of approximately 26+ times for nitro engines to approximately 32+ times for gas engines will allow the use of longer, smaller internal diameter stingers.

Consider the fact that the stingers I use on my 26 cc QD engines are .4062" ID X 5.5" in length. The gas engine's operating temperature is approximately twice what would be found in a nitro engine of the same size. I use a toroidal head with a volume of less than 1 cc & a deck clearance of 002". The measured tuned pipe internal pressure is 120" of water or 4.336 psi. at WOT.

Jim Allen
Jim, the pipe volume that you mention, is it measured from the exhaust port to the end of the stinger or is it the volume of just the coned sections?
Tim,

Measure from the exhaust port to the end of the stinger. Also keep in mind that the area from the exhaust port window to the tuned pipes header should decrease. This part of the tuned pipe should also be pointed in a downward direction, approximately 10* to 15*. The beginning of the tuned pipes header should not be straight, as is found on all of our toy engine stuff, but tapered also, approximately 2* to 3*. Remember, any device that is similar to a tuned pipe will work to some extent. A good ball park figure to look for when calculating the stingers length would be, it's length should be 13.5+ times it's ID, if the pipes volume is the correct amount.

I measured many tuned pipe internal pressures, while the engine is operating, with a Wika water gauge, capable of reading 0 to 200 inches of water in 5 inch increments. Very Interesting stuff found when comparing a good & not so good chamber????

JA

Thanks Jim

I have done a general measurement of a Nova 67-91 pipe that I was looking at running on a 101. It has come out at around 16.5 times the engines volume (at 11.5" length). Interestingly the stinger size is 12.21mm (0.480) diameter by 22mm (0.866) long and therefore only double the width which I assume reduces the back pressure to counter the pipes small volume. (I may be off target here so excuse my ignorance if that is the case)

If not, I ask the question, what is the advantage/disadvantage between smaller volume and larger stinger vs larger volume and smaller stinger. Nova have obviously designed a smaller volume pipe to be used on their 91 motors where as MAC (as an example) make a larger volume and smaller stinger pipe, also does the application change the choice e.g.. Rigger vs mono?

Cheers
 
Tim,

You're not off target. Any tuned pipe can be made to work. The disadvantage of to small a volume & a necessary larger, short stinger, is a lower back pressure as you stated. This would make the use of large straight through bore (.625"+ for 1.00 cu in size engines) carburetors difficult, maybe impossible. The advantage of this type of chamber is, it may be easier to tune because it will require a lower compression ratio & a smaller ID carburetor that has a fuel drawing signal.

Larger volume pipes, with small, longer length stingers (example; CC Racing V2 pipe) allow the use of higher compression ratios & larger, ID bore carburetors. The engine's operating temperature will also be lower & the necessary fuel delivery for the larger bore is possible because of the higher internal pressure.

I cannot say if a different type of a chamber should be used for different type hulls, because I have no experience in this area. When looking at tuned pipes sold on the market, the same type of chamber is being used on both type hulls. My testing under actual running conditions shows that a larger volume, smaller ID, longer length stinger shows a considerable performance gain on the low end, mid range & the high end. Some testing was recently done this past weekend at Falls Lake with the CC racing tuned pipe, which has an adjustable stinger. The engine used was modified & the catamaran type boat was definitely slower with the stinger inside.

There is another thing to consider with larger volume, larger major diameter chambers. The "angles" used in the diffuser sections must be higher. A tuned pipe designed this way can have a longer length in the header. This will greatly improve low end & mid range HP. Using steeper angles in the diffuser sections & the baffle section will produce a much higher boost amount.

JA
 
Back
Top