[2 Stroke] Cagiva Mito Racer-new Exhaust

{mRk} a écrit:

These are the images of Filandro:
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may I ask how you do those sketches of the bend exhaust? I am looking for a simple way since quite a while, but Catia seems to be too much effort without any Macros...

After a long time, finally the parts are ready to weld:
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koenich:there is a simple rule to sketch a bent cone starting from a straight one, this the link to an old book :
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Give a look at page 6, hope this helps.

A very good work, Fil...

Do you used a cone roller? I'm looking for a schematic of one but I can't find, I want to build myself a one.

Muciek a écrit:

Do you used a cone roller? I'm looking for a schematic of one but I can't find, I want to build myself a one.

No, simply bent the cones with hands, using a vice and some tubes of proper diameter.

Filandro a écrit:

Muciek a écrit:

Do you used a cone roller? I'm looking for a schematic of one but I can't find, I want to build myself a one.

No, simply bent the cones with hands, using a vice and some tubes of proper diameter.

Hi If you look on UK ebay they sell them fairly cheap.
I made mine that I roll all of my exhausts, but that was 33years ago
Phil

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I had rolled 3 diffusors by hand and I think it pain in the ass takes much time and not always it look like it should after. I have machines lathe, mill ect so I thought it would be easier to fabricate a roller then get it shipped from another country.

we also tried it by hand, but as you said - it's a pain in the ass and the outcome is not really round shaped.

what i did was to turn cones with different angles on the lathe out of wood (faster and cheaper than metal). around those you can easily lay the metal by hand and finally hammer it in the right form a bit.

with the usual roller you can only roll metal with same diameters on both ends - trying cones the result will be really bad. and to get massive cones for the roller will be quite a big effort.

Muciek a écrit:

I had rolled 3 diffusors by hand and I think it pain in the ass takes much time and not always it look like it should after. I have machines lathe, mill ect so I thought it would be easier to fabricate a roller then get it shipped from another country.

Try this link and go down to weldtutor post
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pfpraider a écrit:

Muciek a écrit:

I had rolled 3 diffusors by hand and I think it pain in the ass takes much time and not always it look like it should after. I have machines lathe, mill ect so I thought it would be easier to fabricate a roller then get it shipped from another country.

Try this link and go down to weldtutor post
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Oh Thanks pfpraider , I will try fabricate it when I will have some free time :) I used cone layout for fabricating cones really simple application.

Hi again. Nice cones.

I make them with big metal rods I have around home and a rubber hammer. And they look good.
Here is the ones for my second exhaust I produced in 2011

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In this moment I am making a ram air box for my 125cc but then I will test tail pipe restrictions identical as the ones you showed.

I have about 21,5/22mm tail restrictor, but I will go to 20,5mm and may even try 20, as frits formula gives 20,3 for 45 horsepower :|

Do you have some results already?

Thanks

romeuh80 a écrit:

I have about 21,5/22mm tail restrictor, but I will go to 20,5mm and may even try 20, as frits formula gives 20,3 for 45 horsepower

Attention, Romeuh: the formula is based on crankshaft horsepower. If you have 45 HP at the rear tire, that will be about 53 HP at the crankshaft and then the restrictor diameter should be at least 22,2 mm.

Frits Overmars a écrit:

romeuh80 a écrit:

I have about 21,5/22mm tail restrictor, but I will go to 20,5mm and may even try 20, as frits formula gives 20,3 for 45 horsepower

Attention, Romeuh: the formula is based on crankshaft horsepower. If you have 45 HP at the rear tire, that will be about 53 HP at the crankshaft and then the restrictor diameter should be at least 22,2 mm.

I would be more then happy if I have 45 at crank

Perhaps not even 40

Will take it to the dyno soon

Two years ago the first three bikes (Aprilia Rs 125 SP) in the Italian championship 125SP were held in parc fermé after the race. Were tested on the dyno. They found a little over 37 hp at the wheel.

Monday, March 10 we are back on track (Rijeka- Grobnik, Croatia) with two Cagiva Mito SP. Perhaps few people know that the Cagiva Mito engine is an old Aermacchi project. We tested small exhaust and cilencer changes to looking forward to the new exhaust designed for the use of de Laval nozzle. I will use a tube 28x1 mm. I'm satisfied of the current performance of the engines, but I want to do even better.

This is the photo of the bike with the kit SP exhaust dated 1995:
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The last update of the SP engine components and electronics made by Cagiva is dated 1996. So I updated all the engine components, including electronics and the exhausts. For years all use exclusively with the Aprilia RS 125 SP. I preferred to work on Cagiva also as an exercise in technique.

Questa è la seconda foto della moto con uno dei nuovi scarichi utilizzati nel 2013:
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With this exhaust the engine works better before the maximum power. The bike is easier to drive for riders. I will modify one of these exhausts to insert the de Laval nozzle. Unfortunately, the friend who produces the exhausts for me lives more than 450 km from my house. He is like me, a simple fan of 2 stroke engines. So the work is progressing slowly. I don't have even a chance to try on dyno, I can only rely on telemetry on track and to the feelings of the rider. So any advice which speeds up work is much appreciated.

The exhaust that I will use for the inserts of de laval may remain unchanged up to the point where it will be added to the de Laval nozzle?

Ecco un paio di foto dello scarico costruito usando il programma FOS:
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Le saldature non sono impeccabili perchè non ho usato la calandra (non ce l'ho..)e il somaro che ha tagliato gli sviluppi al laser ha fatto un lavoro schifoso.
Dalla seconda foto si può vedere la ghiera, alla fine del controcono, che blocca in sede l'ugello.
Adesso non rimane che aspettare il fine settimana per andare a provarla.

What parameters did you use? - Quali parametri hai utilizzato.
I'm curious to get your feedback. - Sono curioso di avere il tuo feedback su questa realizzazione.

This is the drawing obtained with the fos-pipe made ​​available by Fritz:
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Parameters:
Bore × Stroke: 56.0×50.6 mm (124.6 cc)
Exhaust duration: 196 degrees
Target RPM: 11400 r/min
Target HP: 42,0 HP (BMEP 13.2 bar / 192.1 psi)
Wave speed: 550 m/s
Lcyl: 47.0 mm (piston to flange distance)
Cooling: liquid
Diffuser type: 2-stage

I'll try to make it. But first I want to try de de laval nozzles with existing exhausts.

Frits, non Fritz, che poi si arrabbia..  
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Filandro a écrit:

Frits, non Fritz, che poi si arrabbia..  

Grazie Filandro   .

In the above drawing I see an end cone restriction diameter of 19 mm.That may be to narrow. For your target power of 42 HP it should be 3,06*SQR(42) = 19,8 mm, asssuming that you mean 42 HP crankshaft-power. If you mean 42 HP rear wheel power, then the power at the crankshaft will be about 50 HP and you will need a restriction diameter of at least 21,6 mm.

Scusami Frits, ho un due amici che si chiamano Fritz, mi veniva naturale chiamarti così.


I mean 38 HP rear wheel power. I hypothesized a loss of 10% of power between the crankshaft and the wheel. I redid the calculations with the power loss percentage indicated, I got 45.2 hp. With the parameter "target HP" 45.2 I get 20.6 mm.
La potenza alla ruota è di 38 CV. Ho ipotizzato una perdita alla ruota del 10% circa tra albero motore e ruota. Con le perdite percentuali di potenza indicate ho ottenuto il nuovo valore di "target HP" di 45,2 CV. Con questo valore di potenza ottengo una restrizione 3,06*SQR(45,2) = 20,6 mm. Grazie.

The angle of the first cone of the kit SP 1995 exhaust is 3°, initial inner diameter of the exhaust is 35 mm. The angle of the second cone of the kit SP 1995 exhaust is 8°. The final cone is 16 °.
The angle of the first cone exhaust that we made is 4 °, inizial inner diameter is 35 mm. The angle of the second cone of the this exhaust is 9°. The final cone is 16 °.
This is the Cagiva cylinder exhaust side:
L'angolo del primo cono della marmitta kit SP del '95 è di 3°. Il diametro interno iniziale della marmitta è di 35mm. L'angolo del secondo cono è di 8°. L'angolo del controcono finale è di 16°.
L'angolo del primo cono della marmitta che abbiamo utilizzato è di 4°. Il diametro interno iniziale è sempre di 35 mm. L'angolo del secondo cono è di 9°. L'angolo del controcono finale è di 16°.
Questo è il cilindro Cagiva lato scarico:
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This is the exhaust flange:
Questa è la boccola di scarico:
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I will have to make a new exhaust flange because the initial diameter of the fos-pipe exhaust is greater.
Realizzerò una nuova boccola di scarico, il diametro iniziale della marmitta fospipe è maggiore. Devo anche modificare internamente la boccola di scarico?

{mRk} a écrit:

Scusami Frits, ho un due amici che si chiamano Fritz, mi veniva naturale chiamarti così.

Non ti preoccupare, {mRk}. Ma due Italiani che si chaimano Fritz? È veramente strano. Mi hanno sempre chiamato Federico quando lavoravo in Italia.

Citation :

I mean 38 HP rear wheel power. I hypothesized a loss of 10% of power between the crankshaft and the wheel.

I calculate with 5% loss in the primary transmission (assumed, straight-cut gears), 5% in the gearbox, 5% in the chain and 5% (or more) between tire and flywheel drum.

Citation :

I will have to make a new exhaust flange because the initial diameter of the fos-pipe exhaust is greater.

But not as great as in the above drawing. In the drawing I see a diameter of 39 mm at the flange. When I calculate with your parameters, I find a flange diameter of 37,5 mm. And these diameters are very important. If you make them too large, the engine will lose a lot of torque.

EDIT: Maybe I got confused by the two drawings. In the first drawing, I could not read the flange diameter.
In the second drawing I read 39 mm, but I have my doubts about several dimensions in that drawing .

EDIT: Maybe I got confused by the two drawings. In the first drawing, I could not read the flange diameter.
In the second drawing I read 39 mm, but I have my doubts about several dimensions in that drawing .[/quote]
Second drawing is mine..
My engine data:
Speed of sound: 550 ms
rpm of max power: 11500 g/min
exhaust timing: 196°
cubic capacity: 125 cm3
Lcyl 75 mm
Lmax=(550x196x88)/11500=825 mm
Dx=(407-196/7100)xSQR (125x11500)=35.6 mm
Dheader=((0.36x75/0.34x825)+1)xDx=1.096x35.6=39.01mm
Ddiff=1.36x35.6=48 mm
Dmax=3.6x35.6=128 mm
Please Frits  , give a look and tell me what I did wrong

You did not do anything wrong Filandro. Your pipe dimensions did not agree with the Mito-parameters that were presented by {mRk}. But with the parameters that you just posted, everything is OK, except maybe the exit diameter of the end cone. I would advise to make that larger for safety reasons, even if you don't expect to get more than 38 crankshaft-HP.

Thanks!
This pipe has an interchangeable exit cone nozzle; I made two nozzles, with an ID of 20 and 21 mm.
Now it's only time to test and compare it..

Frits Overmars a écrit:

{mRk} a écrit:

Scusami Frits, ho un due amici che si chiamano Fritz, mi veniva naturale chiamarti così.

Non ti preoccupare, {mRk}. Ma due Italiani che si chaimano Fritz? È veramente strano. Mi hanno sempre chiamato Federico quando lavoravo in Italia.

Citation :

I mean 38 HP rear wheel power. I hypothesized a loss of 10% of power between the crankshaft and the wheel.

I calculate with 5% loss in the primary transmission (assumed, straight-cut gears), 5% in the gearbox, 5% in the chain and 5% (or more) between tire and flywheel drum.

Citation :

I will have to make a new exhaust flange because the initial diameter of the fos-pipe exhaust is greater.

But not as great as in the above drawing. In the drawing I see a diameter of 39 mm at the flange. When I calculate with your parameters, I find a flange diameter of 37,5 mm. And these diameters are very important. If you make them too large, the engine will lose a lot of torque.

EDIT: Maybe I got confused by the two drawings. In the first drawing, I could not read the flange diameter.
In the second drawing I read 39 mm, but I have my doubts about several dimensions in that drawing .

People, sorry for the OT.
No, non sono italiani. Uno è sloveno, lavorava alla Tomos. Lo chiamiamo tutti Fritc (si pronuncia Fritz in italiano). Mi ricromava i cilindri. Abito vicino al confine con la Slovenia, l'ex fabbrica della Tomos è a 10 km da Trieste. Avevano un buon nikasil.
L'altro è tedesco (aus Südtirol in Italien), si chiama Fritz.
End OT


Thanks for the information. I tried to optimize everything (primary transmissio, primary transmission, chain, contralbero etc.) within the limits imposed by the technical regulations. I was expecting a lower percentage loss of power.

We use different cylinders with different flange exhaust. Filandro uses standard cylinders. I use last cylinder made for the SP kit. My exhaust flange is shorter. For this reason the parameter "Lcyl" is different.

Then there are also other differences, as the type of piston. Filandro with standard cylinders uses the standard flattop pistons. I use the Mahle (Ziegler) pistons made for Cagiva 500 and then homologated for the Mito SP engine, these:
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The Mahle has an outer band of 3 mm inclined at 6 °. For this reason the design of the heads differ. But this does not affect the dimensioning of the exhuast.
The drawings of the heads that we use is something like that, for those who want to do some head design testing with engines similar to ours:
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This is for flat pistons.