[2 stroke] Exhaust chamber software

Hello is there any one here that  knows of any exhaust chamber software that is modern  and works and which ones to stay away from
i have built a few pipes using A G Bell book as a guide line but the world must have moved on since 1989

Thank you

There is a verry simple calculation file on underdogs racing.com
According to Frits. The most educated and proven exhaust guru
This is a simple but effectieve way to get you in the ballpark.
Luc Foekema is right up there with Frits and some others i know off
(All dutch guys)

Iff all parameters are known these guys could calculate the exhaust to make brutal power.
But you need a special driver to make it work on the track.
So sometimes you can be faster with a pipe thats a little under ultimate design.

At least that is what i think i understand off it

I bought software from Coker Racing products.
It's 5 different excell sheet's for different engine capacities (50-70/70-100/100-200/250-350/350+).
it's not a simple calculation, it needs lot's of info/measrements from your engine and it gives you lot's of  options as to what pipe you'd like.
great advantge I feel is that it directly shows the shape of the pipe and this way you learn rapidly how changes to the engine/input changes the shape of the exhaust.

only used it up till now for exhausts for my Honda Sky MX-moped, but they work very well and changing for example the needed power (pure top-end or more spread) or the revrange, the working of the exhausts shifts just as the programme says.

I'd recommend it to anyone. I could easily pass it on to anyone, but I feel that if someone goes through the trouble of making it and sell it, he deserves to be paid for it in order for those people to keep  doing it. And it's cheap, so it realy is a bargain.

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If anybody wants to give it a try, supply me your data and I'll calculate you some

and this is also very handy and worth it's money, allthough you could endlesly use the free-trial

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Sanderhoutman a écrit:

There is a verry simple calculation file on underdogs racing.com
According to Frits. The most educated and proven exhaust guru
This is a simple but effectieve way to get you in the ballpark.
Luc Foekema is right up there with Frits and some others i know off
(All dutch guys)

Iff all parameters are known these guys could calculate the exhaust to make brutal power.
But you need a special driver to make it work on the track.
So sometimes you can be faster with a pipe thats a little under ultimate design.

At least that is what i think i understand off it

I had a look at the program Sanderhoutman and put in my values and the results looked way off
i put in the details in for a suzuki AC50 engine

Bore                 41mm
Stroke              37.8mm
ex duration       174 degrees
Rev                  8500rpm
power               6 hp

the calculator replied       header 21mm       stinger  8.1mm       belly section 82mm this must be completely wrong or it is not possible to make a pipe work on most of the
50cc cylinders as they have a exhaust flange diameter normally between 25-30mm which is to large for a 21mm header

I have tried all of the so called free calculators online and none of them show the same results

what section or topic can i find the FOS exhaust concept ?

thanks for any feedback

ACR a écrit:

Sanderhoutman a écrit:

There is a verry simple calculation file on underdogs racing.com
According to Frits. The most educated and proven exhaust guru
This is a simple but effectieve way to get you in the ballpark.
Luc Foekema is right up there with Frits and some others i know off
(All dutch guys)

Iff all parameters are known these guys could calculate the exhaust to make brutal power.
But you need a special driver to make it work on the track.
So sometimes you can be faster with a pipe thats a little under ultimate design.

At least that is what i think i understand off it

I had a look at the program Sanderhoutman and put in my values and the results looked way off
i put in the details in for a suzuki AC50 engine

Bore                 41mm
Stroke              37.8mm
ex duration       174 degrees
Rev                  8500rpm
power               6 hp

the calculator replied       header 21mm       stinger  8.1mm       belly section 82mm this must be completely wrong or it is not possible to make a pipe work on most of the
50cc cylinders as they have a exhaust flange diameter normally between 25-30mm which is to large for a 21mm header

I have tried all of the so called free calculators online and none of them show the same results

what section or topic can i find the FOS exhaust concept ?

thanks for any feedback

I'm not an expert on the subject.
I will try to tell / help the best i know.

For a standing wave exhaust you need at least 180 degrees effective duration
In general this results in measured duration between 183 to 190 degrees
The wave needs a head start to occur, that is why its over 180 degrees actualy

Exhaust chambers need flow and the diameters influence the flow.
The dimensions you get are based on the formula designed by Frits.
This is the basic formula to get started.
Exhaust temperature is best to start at arround 520.
Single difusor.
You will see that the pipe changes in length iff you play with different timing and temperatures
Diameters wont change that much.
I would try rpm at 10000-12000
Exhaust 185
Target hp 8
520 m/s wave speed
I have a stock scooter 4.25 hp with stinger size stock 6mm
6 hp with 8.1 stinger is not what scares me. Iff you want to be safe start with 10 mm

Fos is short for Frits Overmars

It is all in the jan Thiel and Frits overmars topic's 1 through 4

I have a dutch file about exhaust chambers i can send iff you want. Maybe translate it with Google ?

ACR a écrit:

what section or topic can i find the FOS exhaust concept ?

you just used it

ACR a écrit:

I had a look at the program Sanderhoutman and put in my values and the results looked way off
i put in the details in for a suzuki AC50 engine

Bore 41mm
Stroke 37.8mm
ex duration 174 degrees
Rev 8500rpm
power 6 hp

the calculator replied header 21mm stinger 8.1mm belly section 82mm this must be completely wrong or it is not possible to make a pipe work on most of the
50cc cylinders as they have a exhaust flange diameter normally between 25-30mm which is to large for a 21mm header

maybe the program is correct, but your "cylinder" is wrong ? could just be as simply as that your exhaust flange is too big for the ex duration/rpm of peak power/...

Its a fail from the cylinder makers, because bigger exhaust duct looks racy and so they can sell more cylinders, sachs engines are even worse, a 50cc engine with a 30mm exhaust duct at the flange, totally bonkers, the solution presented by Frits if I recall correctly is to use a small short cone to reduce the diameter to the expected initial diameter of the exhaust pipe, I have done it, and it works a charm, the other solutions is to either mill a nice round hole and plug a filler plug with the correct diameter(if there is meat/walls to do it without making a huge hole in the duct), or get it welded to make a nice oval duct with the correct dimensions and then have the cylinder replated.

JanBros a écrit:

maybe the program is correct, but your "cylinder" is wrong ?

this is what i was thinking also. ive tried some expansion chamber programs and they never seem to match the size of the exh duct

brokedown a écrit:

JanBros a écrit:

maybe the program is correct, but your "cylinder" is wrong ?

this is what i was thinking also. ive tried some expansion chamber programs and they never seem to match the size of the exh duct

the one I bought just asks you what the diameter is and starts with that one. it's easy but maybe not the best solution for power. But I could always use FOS to determine the "best" diameter, change it on my cylinder and than go on with the program with the changed diameter.

to be honest i dont have much experience with pipe calculators but if i enter the engine information to underdogs it says the starting pipe diameter is 46mm. my cylinder duct diameter is only 35mm. so i dont know what is correct, cylinder or pipe program

Start making this

35 / 46 160 L
46/71 103
71/90 68
90/90 75
90/ 15 160

16 inner taille

Do not make 10 mm then you get damage

ACR
Dutch just confirmed that i'm not the expert.

He is one off the experts i know of that just gave you your christmas present.

Here You go  free application named Exhaust calculator 2 , [Vous devez être inscrit et connecté pour voir ce lien]  ,
Good one is Bimotion Pipe and Port  (http://www.bimotion.se/) , You put there your cylinder ports dimensions and engine data then on another spreadsheet You have a exh calculator (custom and generic Blair one). After this there is only EngMod2T I think but it's more expensive.

Sanderhoutman a écrit:

ACR
Dutch just confirmed that i'm not the expert.

He is one off the experts i know of that just gave you your christmas present.

Well Sanderhoutman  none of us are experts there is always something we learn from each other, thats why we read and write
here and then we learn    so basicly most of the pre 1980s cylinders on the street bikes are far to large at the exhaust flange
as a standard cylinder the suzuki AC50 flange is also 30mm  i took a look at my suzuki AS/TS 50 hopup cylinder Flange  is 32mm
and as i have read Ernst Degner played a part in that design so even experts make mistakes and hopefully they
learn aswell   and i ask here because i see there are alot of clever people here

Thank you every one for the input , now its only to weld and grind and then i have a better starting point