Tuned Pipe Wave Velocity

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Seems I remember the "Two-Stroke Tuner's Handbook" (by Gordon Jennings) being the most popular, and highly recommended for tuned-pipe design/set-up for model engines. I remember purchasing a copy from Shamrock Competition Imports back-in-the-day (I think I still have my copy buried somewhere). I believe it is out of print now, I've seen original copy's going for $400.00USD to $1500.00USD online   :)

TwoStrokeTuner'sHandbook_GordonJennings_01.jpg
 
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Tim get a eagle tree and log some EGT's on the boat as it is running .

That way you will not have to guess at what you are looking for.

You can log RPM .speed ,EGT, eng temp ,throttle position and 3rd channel needle position in real time all on the same spread sheet. 

Can even play it back in real time as you watch it run on google maps. 

I lost all my saved logs when my cheep 10 year old now lap top crashed that I used to down load it all at the pond.

Dose not $$ much and easy to set up and use.

Once you get a feel for the EGT's spreed then you can make calculations.

Be leave me thy are all over the place as you run the boat.
 
I have my boats set up with an Eagle Tree system. I am measuring EGT and cylinder head temperature. An example using a MAC 67 with AB 67 pipe in an older 67 Eagle SG rigger running 60% Nitro I will typically see between 550 - 650 deg F EGT. This is when the boat is at wide open throttle.

I am using a thermocouple located at the center of the pipe's diameter in the middle of the "barrel" section. The thermocouple is a 1/16" diameter - small as I could get to try and get a fast response.

A data logger like a Eagle Tree is a great tool to learn more about what the boat/engine is doing on the water - but there is a learning curve and it does take some deciphering of the data at times. It does take the "guessing" at values away since you have actual data for items like engine rpm, temp, GPS speed, etc.

Mike
 
David Bryant said:
Seems I remember the "Two-Stroke Tuner's Handbook" (by Gordon Jennings) being the most popular, and highly recommended for tuned-pipe design/set-up for model engines. I remember purchasing a copy from Shamrock Competition Imports back-in-the-day (I think I still have my copy buried somewhere). I believe it is out of print now, I've seen original copy's going for $400.00USD to $1500.00USD online   :)

View attachment 97909
Click to expand...
Yes, David, I remember that...got my copy back in the '70's... it's available in PDF online- FREE!

We've attached it below for those who're interested.

Thanks.

View attachment tuners (1).pdf
 
dwilfong said:
Tim get a eagle tree and log some EGT's on the boat as it is running .

That way you will not have to guess at what you are looking for.

You can log RPM .speed ,EGT, eng temp ,throttle position and 3rd channel needle position in real time all on the same spread sheet. 

Can even play it back in real time as you watch it run on google maps. 

I lost all my saved logs when my cheep 10 year old now lap top crashed that I used to down load it all at the pond.

Dose not $$ much and easy to set up and use.

Once you get a feel for the EGT's spreed then you can make calculations.

Be leave me thy are all over the place as you run the boat. Yes
Click to expand...
Thanks, Dave...been meaning to look into an Eagle Tree system... seems I remember Julian

mentioning his a while ago. 

Yes, would imagine they're all over the place... such that it is in an dynamic environment.

Log data from a varied sample of weather environments and develop a baseline mean.

We had toyed with the thought of a fuel delivery system that monitored EGT and optimized

fuel flow accordingly, grossly similar to EFI management. One could manually program to

logic chip, via laptop, a preset parameter. Even could get as complex as they wanted to with

presets, including TPS and MAF sensors. It could be done with minimal weight and current

draw considerations, too.

Appreciate the input, Dave.
 
Mike Rappold said:
I have my boats set up with an Eagle Tree system. I am measuring EGT and cylinder head temperature. An example using a MAC 67 with AB 67 pipe in an older 67 Eagle SG rigger running 60% Nitro I will typically see between 550 - 650 deg F EGT. This is when the boat is at wide open throttle.

I am using a thermocouple located at the center of the pipe's diameter in the middle of the "barrel" section. The thermocouple is a 1/16" diameter - small as I could get to try and get a fast response.

A data logger like a Eagle Tree is a great tool to learn more about what the boat/engine is doing on the water - but there is a learning curve and it does take some deciphering of the data at times. It does take the "guessing" at values away since you have actual data for items like engine rpm, temp, GPS speed, etc.

Mike
Click to expand...
Most excellent report, Mike, and we thank you for that!

Now I'm wondering about possibly moving the probe closer to, or at, the header/pipe interface

on a ceramic coated system.

Regarding this particular coating we're using, including the piston crown and squish/bowl area

of head button, the before/after comparison we've witnessed on the dyno sheets taken from

the run of a stock Chevrolet 350 + .030" TBI engine, stock other than overbore, showed an

average net gain of 14hp.

As soon as we have our NR46 'test mule' fully broken in we are going to experiment with DFL

on the piston's slip surfaces. That application has showed even further net gain, dyno wise,

on the 355 engine above...the figure eludes me now, without going back and looking at the

notes.

We'll go and study the Eagle Tree system... the speed of this particular hydro on the radar

gun, even while the engine isn't fully seated and optimum prop and tuning isn't in effect,

is flat out staggering...at least it is to me. I think our positive pressure inlet system may

contribute, to a certain degree, to this performance, thus far.

Again, your input is most appreciated, Mike...

Thanks!
 
Mike Rappold said:
I have my boats set up with an Eagle Tree system. I am measuring EGT and cylinder head temperature. An example using a MAC 67 with AB 67 pipe in an older 67 Eagle SG rigger running 60% Nitro I will typically see between 550 - 650 deg F EGT. This is when the boat is at wide open throttle.

I am using a thermocouple located at the center of the pipe's diameter in the middle of the "barrel" section. The thermocouple is a 1/16" diameter - small as I could get to try and get a fast response.

A data logger like a Eagle Tree is a great tool to learn more about what the boat/engine is doing on the water - but there is a learning curve and it does take some deciphering of the data at times. It does take the "guessing" at values away since you have actual data for items like engine rpm, temp, GPS speed, etc.

Mike
Click to expand...
Mike, a question regarding the Eagle Tree system-

Can you use the data logger independent of real time

telemetry, or both at once?... please excuse my lack of

knowledge on the system.

Thanks, again.
 
Tim just throw your tug in the water and test it haha,I'm going boatin

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Tim the eagle tree is easy to use.

Drill a hole in the fly wheel smaller than the magnet thy give you and press it in. then make a bracket to hold the sender.

you can put the heat pin point resistor in a wire end and stick it under the glow plug.

But I like the loop sensor that will just wrap around the head.

If you have the skills try this. https://www.arduino.cc/

I have one but did not have the skills or time to figure it out.

Should be a cake walk for you. 

I was going to control the needle with it using EGT head temp and RPM.

Check it out and let me know if you can wright the code to make it work.

There are play grounds that have copy and past codes to lode in it for servo controls. also K probe adapter codes. 

It can also hold logs and TONS of other stuff.

It is the BOMB if you can program it right?
 
dwilfong said:
Tim the eagle tree is easy to use.

Drill a hole in the fly wheel smaller than the magnet thy give you and press it in. then make a bracket to hold the sender.

you can put the heat pin point resistor in a wire end and stick it under the glow plug.

But I like the loop sensor that will just wrap around the head.

If you have the skills try this. https://www.arduino.cc/

I have one but did not have the skills or time to figure it out.

Should be a cake walk for you. 

I was going to control the needle with it using EGT head temp and RPM.

Check it out and let me know if you can wright the code to make it work.

There are play grounds that have copy and past codes to lode in it for servo controls. also K probe adapter codes. 

It can also hold logs and TONS of other stuff.

It is the BOMB if you can program it right?
Click to expand...
Thanks, Dave...

How does the mass of the trigger magnet compare to the mass of the aluminum removed

via drilling the pocket in flywheel?... suppose if it came down to it, could arbor it up in the

magnetic balancer along with balancing the 2 end points of the arbor with flywheel

mounted for a makeshift, half assed dynamic balance job- using digi pocket scales.

Regarding the Arduino (C/C++ coding), I've been contemplating implementing the

Arduino UNO into my inertial dyno controller for data logging, but I think we can log within

Windows. The dyno software and coding is done. There's a forum for the Arduino's out

there that have a wealth of guidance and info on.

    https://forum.arduino.cc 

    https://www.reddit.com/r/arduino/

    http://discuss.littlebits.cc/c/arduino

As soon as I get freed up a bit, we'll send you a message regarding this portable inertial dyno

we've been working on that has a few sample channels within- hopefully it will be a buh-bye

to the air flow/density devices out there... here's a hint- all you'll need in your pits is a lap top

and this lil' 'magic box' that couples to your stub shaft engaging the d/dog, with prop removed.

Engine temp and EGT will be sampled, under load. Inputs will go through 3 channels-

HE trigger/sensor, plug temp, EGT, MOI and other inertia wheel properties. With the parasitics

involved in the shaft/strut system a wheel of less MOI can be implemented. Once user becomes

acclimated, whole process is doable in ~10 minutes. This opens up the opportunity to make

shim changes, carb swaps, and TL adjustments as the atmosphere changes trackside.

Anyway, the only thing holding me up is the fact that my Ambition tree outback has died, thus

unable to provide me with the much needed Ambition fruit.  ;)

This aging thing truly sucks!...and I waited 25 yrs. to get back into this deal.  :(

Wile-E-Coyote-clever-rocket-plan.jpg
 
The catch with measured EGT is where do you measure it.  For the empirical pipe design "programs" you are looking for some arbitrary average sound velocity.  A good simulator will calculate the actual temperatures, velocities, and mass flows all through the engine.  These are determined by the combustion model.  However, in inexpensive simulation programs that's somewhat arbitrary but still more realistic.  The temperatures I've used in the above programs  for gasoline engine pipes are between 400 and 600 degrees C depending on the state of tune.  Nitro fuels are cooler, but I haven't done designs for nitro engines. 

Another area that has seen serious experimentation is the shape of the passage between the port and the header.  Cooling the header and that transition area is also important.  The feeling in high performance small two strokes has been that you need to keep heat in the pipe, but cool the exhaust flange area.  Some mixture spills out of the exhaust and is forced back into the cylinder, supercharging the engine.  Cooling the exhaust flange area acts like an intercooler on a turbo.  Keeping heat in the pipe preserves the energy of the exhaust pulse.  The diagram below shows a transition that works well with highly tuned engines with triple exhaust ports.  ABC engines with similar wide ports should also benefit.

Lohring Miller

Exh Duct Geometry.jpg
 
LohringMiller said:
The catch with measured EGT is where do you measure it.  For the empirical pipe design "programs" you are looking for some arbitrary average sound velocity.  A good simulator will calculate the actual temperatures, velocities, and mass flows all through the engine.  These are determined by the combustion model.  However, in inexpensive simulation programs that's somewhat arbitrary but still more realistic.  The temperatures I've used in the above programs  for gasoline engine pipes are between 400 and 600 degrees C depending on the state of tune.  Nitro fuels are cooler, but I haven't done designs for nitro engines. 

Another area that has seen serious experimentation is the shape of the passage between the port and the header.  Cooling the header and that transition area is also important.  The feeling in high performance small two strokes has been that you need to keep heat in the pipe, but cool the exhaust flange area.  Some mixture spills out of the exhaust and is forced back into the cylinder, supercharging the engine.  Cooling the exhaust flange area acts like an intercooler on a turbo.  Keeping heat in the pipe preserves the energy of the exhaust pulse.  The diagram below shows a transition that works well with highly tuned engines with triple exhaust ports.  ABC engines with similar wide ports should also benefit.

Lohring Miller

View attachment 97934
Click to expand...
Gee, thanks, IW!... my reply got blown away...

At any rate, redone in less technical form- as amplitude increases, cooling is in effect

(largest diametric cross section of diverging cone), hence while entering the converging

baffle, compression forms and transformation occurs in the form of reheating, thus

accelerating the wave again. So, in essence, a dynamic pulsing in velocity occurs.

Application of engineering 'common sense' based on experience could get to a reason-

able conclusion. Let's not forget we are using OEM supplied pipes designed by the same 

engineers who've designed any given engine.

Essentially, I believe Mike Rappold thought about his placement of the thermocouple

probe and found a satisfactory mean- for all intents and purposes.

Wave velocity on an average, based on Mike's log, of 600° equates to 1595.7 f/ps.

One last thing, surely the temperature variances at any given point within the pipe

CAN be calculated, but it is a thermodynamic problem of significant difficulty. A com-

puter would certainly ease the burden, as would diagnostic equip., at a tremendous

financial expense...hardly worth any of it regarding our 'toy boats'.

 We'll procure an Eagle Tree system and see what we can determine... in the mean time

we'll go start a Go Fund Me account in an attempt to garner the funds needed to

purchase an L&S EC dynamometer and all the related support... only going to take the

better part of $20K!

Final thought- the Speed Kings-aka- outrigger hydros- are less prone to pipe idiosyn-

cracies than our other hull classes.

Thanks for your input, Lohring.
 
timwhalen said:
Mike, a question regarding the Eagle Tree system-

Can you use the data logger independent of real time

telemetry, or both at once?... please excuse my lack of

knowledge on the system.

Thanks, again.
Click to expand...
Tim,

No problem on the logger questions. Be glad to help.

I do not use the real time telemetry. Instead after a run I download the data from the logger to a laptop. I then import the data file into an Excel spreadsheet that is more customized/easier to view than what Eagle Tree offers. I do not use the real time telemetry because it is too hard to watch the boat plus look down at a screen.

For the engine rpm sensing, I use two magnets 180 degrees apart pressed into the engine's flywheel. With two magnets there are no balance issues. The magnets are pressed into a hole/pocket in the flywheel that is 0.125" dia x 0.067 deep. I use a small centerpunch to peen the edges of the holes in two places to "squish" the edges of the hole. This locks the magnets in place to prevent them from flying out. The rpm sensor is a hall effect senor. It is mounted in an aluminum bracket that is attached to the engine rail. The photo attached shows one of the flywheel magnets and the sensor mount.

For cylinder head temp, I use a thermocouple soldered to an eyelet. The eyelet is the glow plug washer then. I wanted to get the thermocouple as close to the cylinder as possible. Using the eyelet/washer method has been a good repeatable location. For the boats the cylinder head temp has been one of the most valuable tuning aids. Changes to the cooling water amount can be measured.

On the EGT, I use a brass screw/nut assembly to create a compression sleeve system to hold the thermocouple probe. The probe extends to the center of the pipe's diameter.

For the logger itself, I use the logger plus the thermocouple expansion module. This is where the EGT and CHT thermocouples connect in my setup. I also have the GPS expander to measure speed. On the logger, the faster the logging rate the better - typically 20hz to 40 hz depending upon logger model used.

Hope this helps.

Mike

2005_0702Image0018.JPG

2005_0702Image0017.JPG
 
Mike Rappold said:
Tim,

No problem on the logger questions. Be glad to help.

I do not use the real time telemetry. Instead after a run I download the data from the logger to a laptop. I then import the data file into an Excel spreadsheet that is more customized/easier to view than what Eagle Tree offers. I do not use the real time telemetry because it is too hard to watch the boat plus look down at a screen.

For the engine rpm sensing, I use two magnets 180 degrees apart pressed into the engine's flywheel. With two magnets there are no balance issues. The magnets are pressed into a hole/pocket in the flywheel that is 0.125" dia x 0.067 deep. I use a small centerpunch to peen the edges of the holes in two places to "squish" the edges of the hole. This locks the magnets in place to prevent them from flying out. The rpm sensor is a hall effect senor. It is mounted in an aluminum bracket that is attached to the engine rail. The photo attached shows one of the flywheel magnets and the sensor mount.

For cylinder head temp, I use a thermocouple soldered to an eyelet. The eyelet is the glow plug washer then. I wanted to get the thermocouple as close to the cylinder as possible. Using the eyelet/washer method has been a good repeatable location. For the boats the cylinder head temp has been one of the most valuable tuning aids. Changes to the cooling water amount can be measured.

On the EGT, I use a brass screw/nut assembly to create a compression sleeve system to hold the thermocouple probe. The probe extends to the center of the pipe's diameter.

For the logger itself, I use the logger plus the thermocouple expansion module. This is where the EGT and CHT thermocouples connect in my setup. I also have the GPS expander to measure speed. On the logger, the faster the logging rate the better - typically 20hz to 40 hz depending upon logger model used.

Hope this helps.

Mike

View attachment 97943

View attachment 97944
Click to expand...


Got blown out of the water with our reply...again!... 5:01 am here and we're beyond shot...

will reply tomorrow, with a couple of questions- Thanks a bunch, Mike.

Club Cheeto.png
 
It's not expensive these days to do the thermodynamic calculations in a two stroke (or a four stroke) engine.  Scavenging is a lot tougher problem and requires a full 3D model with a computational flow program.  It has been done, though.  The model most people I know use is one dimensional.  It works very well for pipe and port design using empirical models for scavenging and combustion.  The program is EngMod2T costing around $400 and comes with forever updating.  It is based on Gordon Blair's work outlined in "The Design and Simulation of Two-Stroke Engines" mentioned above.  EngMod has been improved over the years with inputs from around the world by the best two stroke tuners.  It also contains great versions of the empirical pipe design and time area programs that were used for years. 

I can't recommend using it if you aren't very serious about engine design.  The available commercial pipes are very good.  All you need to do is tweak your port timing and pipe length to get the best performance from the hull and propeller you are running.  That's not trivial, though.  LOL

Lohring Miller
 

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