Tuned Pipe Wave Velocity

[dwilfong]

It could be the motor to some extent but it's mostly "noise" IMHO.  I'm only using 10 hz here as that's what the LCD panel wants, but I have tried 50 hz and it's not much better.

I doubt a motor could actually jump from 9-14K in 0.1sec. unless it's hitting the pipe.  (199.9 - 200.0 sec.).

Funny tho it is pretty smooth coming on pipe from 15-23K. 

Yes it is funny that as soon as the boat catches up to the eng it gets erratic.

Might need a little more load on the eng.

 

[John Beardslee]

Terry what material and how thick are you using to mount your hall affect sensor? On all my heli’s I’ve used G10 -1/16” or 3/32” depending on how far it has to reach the magnet. Always mounted to the engine lug. As you know the magnets also have to have the correct pole facing the pickup. I always epoxied the magnets in the flywheel and used lead shot of the same weight to balance the other side.

 Thanks John 

 

[Terry Keeley]

Thanks guys. That's an old mount in the pic, I've made a newer solid aluminum one and even tried a rubber insulator mount with the same results.  The only thing left I might try is a noise reducing circuit from the sensor mfg but I'm not holding my breath.  Optical IR is supposed to work very well as long as there's a good flat black section. 

 

[LohringMiller]

We always noticed a lag in GPS speed relative to engine rpm.  The early GPS units were really bad.  The rpm variations happen as the prop immersion changes.  We also see this with an electric motor's current draw.  Below are two example graphs.  The first is from a gas hydro 2005 SAW record run.  Note the GPS lag and the rpm fluctuation through the trap.  The average rpm is a much more sensitive speed indication, especially with the early GPS units.  The second is from the 2008 UIM kilo record setting electric hydro runs.  The voltage and current is from ONE 6S pack.  The total voltage was 6 times and the current was 7 times the values graphed.  The rpm is prop rpm.  The motor rpm is that value divided by 1.75.  There is almost no GPS lag with the newer unit, but there's still a little.  The prop is much more immersed than on model boats, but you can see the effect of rough water on the first pass.  You can also see where Mike lifted a little due to the rough water.  We might have been able to get an average over 100 with really perfect conditions.  The first run was into the wind and the second was down wind.  The boat flies better into the wind giving a little more speed.

Lohring Miller

 

[dwilfong]

Thanks guys. That's an old mount in the pic, I've made a newer solid aluminum one and even tried a rubber insulator mount with the same results.  The only thing left I might try is a noise reducing circuit from the sensor mfg but I'm not holding my breath.  Optical IR is supposed to work very well as long as there's a good flat black section. 

I tried the optical and it is hard to keep the white white and the flat black flat.

Did not work so good.

 

[DickJones]

I tried the optical and it is hard to keep the white white and the flat black flat.

Did not work so good.

Mr. dwilfongoooooo

I started reading alotttttttt of this thread, part way thru,  I started getting a terrible headache, I took some of my orange, blue, yellow and ooooorange pills to help my pain, after some time I figured out the pain, was coming from all the thread I was trying to consume in my very,very small brain!!!!!!!!!!!!!!!!!

dick     

 

[PaulHail]

People have been getting great performance out of their engines and winning races without knowing the wave velocity in their pipes.

The real question is, if you know the wave velocity could you plug in a formula for your engines port timings, rpm, operating temp, fuel, prop load and come out with the exact length you need to set the pipe at, or will end up with a range of settings say +/- 1/4" of length and have to test and tune the same way everyone's been doing for decades.

 

[dwilfong]

Mr. dwilfongoooooo

I started reading alotttttttt of this thread, part way thru,  I started getting a terrible headache, I took some of my orange, blue, yellow and ooooorange pills to help my pain, after some time I figured out the pain, was coming from all the thread I was trying to consume in my very,very small brain!!!!!!!!!!!!!!!!!

dick     

Sorry dick did not mean to give you a headache.........................may be try a different pill??????

I will try to simplify it more the next time around.

May be I will just post some eng noises to sooth your mind some.

 

[Ray Sametz]

People have been getting great performance out of their engines and winning races without knowing the wave velocity in their pipes.

The real question is, if you know the wave velocity could you plug in a formula for your engines port timings, rpm, operating temp, fuel, prop load and come out with the exact length you need to set the pipe at, or will end up with a range of settings say +/- 1/4" of length and have to test and tune the same way everyone's been doing for decades.

DING DING, Give that man a See Gar. 

 

[David Ashcroft]

DING DING, Give that man a See Gar. 

Yep

 

[DickJones]

Tim there is more to it than just what you are showing in the examples.

The pipe will pull a vacuum in the case all the way back to the carb if it is flowing right.

Intake timing will also effect how a pipe comes on and also port timing and design.

Some eng with the same pipe set at the same length with the same prop will be on pipe as soon as thy hit the water.  

When others will struggle to get on pipe.

So why dose this happen???????? 

Is it  the pipes fault??????

Just some thing to chew on........................................

Well, fellow boaters,  I always run my  "15 year old pipe, and it always works good enough for me, although I would like a little more speed, as I am sure we all would.

JM2CW  dick jones