ESE's works engine tuner

[ceci]

And adding to the effect of having very high exhaust duration you can cut the skirts short such that the port is open a few mm when the piston is at TDC.
Wreaks havoc with the jetting , but in the project i tried that we were using big pumper carbs.
Very easy to adjust the fuel curve as was needed - but I doubt a normal carb could be made to work.
This setup on a " stock " 950 SeaDoo gave an added 8 Hp in about 80 , so 10% - enough for the title at Havasu.
On a 1180 twin race motor the bump was 15 Hp in 120 so a little less.

That fact intrigues me, filling (supercharging) supplement volume charge for the exhaust why it happens.
How to get that little supplement volume of cargo to the exhaust:
The depression of the main exhaust creates a venturi effect and attracts it
the inertia of the incoming mixture forces it out through this small slot.
Which of the two causes can it be?

[andreas]

That fact intrigues me, filling (supercharging) supplement volume charge for the exhaust why it happens.
How to get that little supplement volume of cargo to the exhaust:
The depression of the main exhaust creates a venturi effect and attracts it
the inertia of the incoming mixture forces it out through this small slot.
Which of the two causes can it be?

I believe it's the split suction wave from the single diffuser that find it's way into the tdc side crank case. Or it's explained on previous pages.

[ceci]

wobbly, your project excites me, it resembles the project that I would like to carry out. The two projects are based on supercharging the engine by providing an extra supplement through the exhaust.
In the project I want to carry out, being a single cylinder, the supplement is provided by an auxiliary pump cylinder
Attempts to find a suitable solution to provide that supplement

[ceci]

Another attempt, is based on the FOX cylinder of Mr. Frits Overmars

[JanBros]

My spreadsheet for porting, head and pipe is ready (well, for now, as such things are never "final" )


excel : http://users.telenet.be/jannemie/Jan...oke%201.0.xlsm
manual : http://users.telenet.be/jannemie/Jan...oke%201.0.docx

I've opened a seperate topic where we can discuss it if people feel the need.

https://www.kiwibiker.co.nz/forums/s...post1131145957

[Frits Overmars]

My spreadsheet for porting, head and pipe is ready (well, for now, as such things are never "final" )
excel : http://users.telenet.be/jannemie/Jan...oke%201.0.xlsm
manual : http://users.telenet.be/jannemie/Jan...oke%201.0.docx
I've opened a seperate topic where we can discuss it if people feel the need.
https://www.kiwibiker.co.nz/forums/s...post1131145957

Bravo Jan ! I know that it has been a tremendous amount of work.
I noticed that you refer to my 'Leaning Tower of Pisa' story. If you wish, you can download the complete Pisa-story from https://drive.google.com/drive/folde...rNTk89_KgwgWof , from the folder 'FOS Tips & Concepts', and bundle it with your masterpiece.
In fact, you can use everything you find there and use it, provided credits are respected.
You might also take a look at the disclaimer accompanying the 'FOS Exhaust Concept'; it is a bit more extensive than the older version that you quoted.

[Frits Overmars]

Frits, don't know if I have to congratulate you or ask you, looking at this graph :
is from my excel, entered all the RSA data (cylinder and head, and than calculated your FOS pipe. Red is standard FOS as by your fomula's with 57.5 BHP at crank and an exhaust temp of 587° to get the same length as the tubo102....

Jan, I was so delighted with your praise that I did not notice until now, that the above value of 587 must have been the speed of sound instead of the exhaust gas temp. I already corrected this wherever I could and if you do the same, I can delete this post and pretend it never happened

[JanBros]

changed it Frits .

Guess it's an old habit of all the other pipe program's out there, and the old one I used; they all use exhaust gas temp as the changeable variable.

so checked my manual end excel and made the same mistake there

so changed it and uploaded correct versions. Also put a direct link to the Pisa story in it if that's ok. I haven't got much upload space, and uploadeing the same again is a bit silly I think.

[marsheng]

Jan, I was so delighted with your praise that I did not notice until now, that the above value of 587 must have been the speed of sound instead of the exhaust gas temp.

Is it not always at the speed of sound? The speed just needs to be corrected for air temperature and pressure.

[cotswold]

The KTM went back on the dyno today, last time we were a little underwhelmed with 38 bhp and an awful curve.
John splashed out on a new FMF fatty and it added about 3 1/2 but the golden touch was winding the power valve spring right out flush,😜 it went from 41 ish up to 48, the curve was much stronger too, we’ll gear it to run where it’s strong and not use the overrev.
TZee made the magic happen as he was wondering how the Valve was adjusted, someone had wound the springs all the way in, I reverse engineered that and wound it all the way out and bingo an extra 8 BHP. ]
Green the original pipe, blue the new pipe, red the power valve wound out with the new pipe

[Frits Overmars]

Changed it Frits. Guess it's an old habit of all the other pipe program's out there, and the old one I used; they all use exhaust gas temp as the changeable variable.
I also put a direct link to the Pisa story in it if that's ok. I haven't got much upload space, and uploadeing the same again is a bit silly I think.

It's fine by me Jan, but the link https://drive.google.com/drive/folders/1JXzzjE_Ol6LGs-yEMuy2DbpjdH-2R0f
that I found in the updated version of your documentation, doesn't seem to work here...

Is it not always at the speed of sound? The speed just needs to be corrected for air temperature and pressure.

Yes Marsheng, it's always the speed of sound. And if you want to work it out via the exhaust gas temperature (not the air temperature), you would have to know that temperature and you would have to know how to do the math. But why complicate a simple exhaust concept like mine?
Just enter the speed of sound directly and you're good. KISS, remember?

[andreas]

Here is the conversion between speed and temp: The front of all pressure waves travels at the local speed of sound, ao,

ao = ^YR(Texc + 273) m/s
R and Y be estimated to be as for air at atmospheric conditions, i.e., 287 J/kgK and 1.4,
respectively.

The roof is square root.
Blair

[Niels Abildgaard]

Here is the conversion between speed and temp: The front of all pressure waves travels at the local speed of sound, ao,

ao = ^YR(Texc + 273) m/s
R and Y be estimated to be as for air at atmospheric conditions, i.e., 287 J/kgK and 1.4,
respectively.

The roof is square root.
Blair

It can maybe be easier to remember this way:
Ad degree celcius of exhaust to 273.
Take the square root of this number and multiply by 20 and this is then speed of sound in meter per second.

Example

500 degree Celcius

500 +273 is equal to 773 and square root of 773 is27.8.
if 27.8 is multiplied by 20 we gett 556 meter per second

[JanBros]

It's fine by me Jan, but the link https://drive.google.com/drive/folders/1JXzzjE_Ol6LGs-yEMuy2DbpjdH-2R0f
that I found in the updated version of your documentation, doesn't seem to work here...

direct link seems to be impossible, so removed the "hyperlink" from the word document.
pasting the link into a browser leeds the user to the FOS concepts folder and than they'll find it "somwhere in the middle" ;-)

[lodgernz]

It can maybe be easier to remember this way:
Ad degree celcius of exhaust to 273.
Take the square root of this number and multiply by 20 and this is then speed of sound in meter per second.

Example

500 degree Celcius

500 +273 is equal to 773 and square root of 773 is27.8.
if 27.8 is multiplied by 20 we gett 556 meter per second

This formula and the other one given above are only approximations for low temperatures around room temp and will be grossly inaccurate at exhaust temps.

The correct formula for Speed of Sound S at temperature T in ⁰C is:

S = 331.3*SQRT((T+273.15)/273.15) m/s