[2 Stroke] Cagiva Mito Racer-new Exhaust

Hello everybody, I've a track-only Cagiva Mito, with an old Factory kit exhaust, this:
[img][Vous devez être inscrit et connecté pour voir cette image][/img]
Using the FOS Calc chart (thanks again, Frits!!)with a value of 550 m/s and data for my engine (Bore x Stroke 56.0x50.6, 196° Exhaust Opening, max power at 11500 rpm, 38 crank HP) , this is the exhaust:
[img][Vous devez être inscrit et connecté pour voir cette image][/img]
Is 35 mm shorter than mine, and with a bigger belly; I noticed, using the FOS Calc, that only little changes in engine data give to great differences on exhaust dimensions.
I'm thinking to made the exhaust obtained with FOS Calc, putting a bolted flange between header and diffuser, and an interchangeable nozzle at the baffle's end.
This way, I could try a different exhaust without the great effort of a new one header (that's a lot of time to made it), and a different tail restrictor diameter (it's a semplified DeLaval nozzle , right?).
What do you think about?
PS sorry to write only in( my very bad) English, but I know only few French words..

Hi, interesting topic, I will follow, has I probably will make a interchangeble tail restrictor too.

I Think you should develop three or four staged diffusor, and better start on safe side for the size of restricitor, I would start by 21mm. If it overrevs good and doesn't seized going straight in six gear then going down to 20 or 20,5mm.

Try this software to compare results: [Vous devez être inscrit et connecté pour voir ce lien]

I have used it several times, I leave one of the examples I build for my tuned CRM 125 engine (first tune state). Amazing top end, max power around +12000


[Vous devez être inscrit et connecté pour voir cette image]

i think this programme uses (more or less) blair's calculations,

Et c'est qui Blair?

rgdavid a écrit:

i think this programme uses (more or less) blair's calculations,

Yes

[Vous devez être inscrit et connecté pour voir cette image]

Il suffit de demander, vive Pit-Lane

Filandro a écrit:

....I'm thinking to made the exhaust obtained with FOS Calc, putting a bolted flange between header and diffuser, and an interchangeable nozzle at the baffle's end. This way, I could try a different exhaust without the great effort of a new one header (that's a lot of time to made it), and a different tail restrictor diameter (it's a semplified DeLaval nozzle , right?). What do you think about?

Good ideas, Filandro.

Citation :

PS sorry to write only in( my very bad) English, but I know only few French words..

Potresti scrivere in italiano. Per me sarebbe più facile che francese .

Citation :

Potresti scrivere in italiano. Per me sarebbe più facile che francese .

Mi sento piccolo così
Parlo (poco e male) solo una lingua straniera, ci sono persone qui che ne parlano almeno 3..
Ok, talking about silencers..mine is 300 mm long x 70 mm outside diameter, with a 26 inner diameter ??"tubo forato"??.

Que c'est beau l'italien!

Filandro a écrit:

.. talking about silencers..mine is 300 mm long x 70 mm outside diameter, with a 26 inner diameter ?"tubo forato"?

Those dimensions are fine, Filandro.
The trick with languages is to notice the similarities. For example: if I write about a perforated tube, even if you have never before seen the expression, you will immediately recognize that it means tubo forato .

Another question.This is a spare cylinder for my Mito, I made a sketch on it:
[Vous devez être inscrit et connecté pour voir cette image][Vous devez être inscrit et connecté pour voir ce lien]" border="0" alt=""/>
if I use some miracle green epoxy as Jan did on RSW cylinders, it's necessary to widen the ports?(as shown in the next photo)
[Vous devez être inscrit et connecté pour voir cette image][Vous devez être inscrit et connecté pour voir ce lien]" border="0" alt=""/>
Another work I would do on this barrel is shorten the reed cage housing; stock reed cage is huge (is the same of Honda CR250), I use a Honda CR 125 cage and manifold, far smaller and shorter than stock one.
I thought to cut off 10 mm on the joining surface, as in this photo:
[Vous devez être inscrit et connecté pour voir cette image][Vous devez être inscrit et connecté pour voir ce lien]" border="0" alt=""/>

I would not mind with big cranckcase volume and reed valve area....

That work on the first cylinder would compromise intake area for B ports....I think

Good night, by far I'm no expert, but I can try to help you.

I wouldn't fill anything in the B port ducts, they already seem so small compared to the A ducts.

What I would do, was to do some ducts connection the intake to the B ducts, like the aprilia rs 125 engines have, enlarge the direct crankcase intake a lot, and trim the skirts to match the new bigger cranckase intake.
I would try to find a single ring piston, with the retainer in the center, so you could go get some extra area in the B and C transfers, widen the main cylinder intake a bit(or a lot), fit something like a 38mm carburettor and some bigger reed cage, and also try to get some more area in the exhaust boost ports, to have as much blow down area as possible.

senso a écrit:

What I would do, was to do some ducts connection the intake to the B ducts, like the aprilia rs 125 engines have, enlarge the direct crankcase intake a lot, and trim the skirts to match the new bigger cranckase intake.
I would try to find a single ring piston, with the retainer in the center, so you could go get some extra area in the B and C transfers, widen the main cylinder intake a bit(or a lot), fit something like a 38mm carburettor and some bigger reed cage, and also try to get some more area in the exhaust boost ports, to have as much blow down area as possible.

Thanks a lot, but Mito and RS barrels are quite similar; the ducts connecting intake to transfers there are jet on stock Cagivas.
About the intake port, I'm working on it.
I don't like huge carburettors, in Italy Sport Pro bikes (now only Aprilia RS) run with a VHST 28, developing something like 38 HP at rear wheel; I have the same Dell'Orto, with Honda reed cage and HRC reeds (stock reeds on Honda GP 125).
I'll post a sketch of my barrel porting.

Filandro a écrit:

senso a écrit:

What I would do, was to do some ducts connection the intake to the B ducts, like the aprilia rs 125 engines have, enlarge the direct crankcase intake a lot, and trim the skirts to match the new bigger cranckase intake.
I would try to find a single ring piston, with the retainer in the center, so you could go get some extra area in the B and C transfers, widen the main cylinder intake a bit(or a lot), fit something like a 38mm carburettor and some bigger reed cage, and also try to get some more area in the exhaust boost ports, to have as much blow down area as possible.

Thanks a lot, but Mito and RS barrels are quite similar; the ducts connecting intake to transfers there are jet on stock Cagivas.
About the intake port, I'm working on it.
I don't like huge carburettors, in Italy Sport Pro bikes (now only Aprilia RS) run with a VHST 28, developing something like 38 HP at rear wheel; I have the same Dell'Orto, with Honda reed cage and HRC reeds (stock reeds on Honda GP 125).
I'll post a sketch of my barrel porting.

That is weird, you should at least use a 34mm carb

I agree with senso. You have some of cheap motocross 56mm single ring pistons available...

I am a fan of 2 stroke engines. We use the Aprilia RS 125 SP Cagiva Mito 125 SP in the Alpe Adria Championship.
[Vous devez être inscrit et connecté pour voir cette image]

The power of the Mito engine is about 37.5-38 hp at 11,300 rpm at the wheel.
This is one of the cylinders we use:
[Vous devez être inscrit et connecté pour voir cette image]
Exhaust duration 196 degs.
This is the exhaust flange:
[Vous devez être inscrit et connecté pour voir cette image]
The output is not circular. We use exhaust with initial diameter Ø35-36mm (circular). I will try to use the program to create a new exhaust with FOS Pipe Calc. In this case the flange must be included in the value Lcyl?

This is one of our exhaust:
[Vous devez être inscrit et connecté pour voir cette image]
The inner diameter of the muffler is 28mm, length 28cm, otherwise the engine gets too hot:
[Vous devez être inscrit et connecté pour voir cette image]
We use Mahle pistons, should be the last of Ziegler:
[Vous devez être inscrit et connecté pour voir cette image]

Mahle are flattop pistons with an outer band of 3mm with angle of 6 degrees, single NPR ring (0.8mm).
We use Dell'Orto VHST 28 of the Aprilia RS 125 SP calibrated for the Cagiva Mito engine.
The compression ratio is limited by the technical regulations in 13,5:1.
We use heads like this but with the squish band angle of 6 degrees:
[Vous devez être inscrit et connecté pour voir cette image]
We use Kokusan small rotor ignition.
[Vous devez être inscrit et connecté pour voir cette image]
To develop and implement programmable CDI and PV controller I have worked with Zeeltronic.
We use 102 octane unleaded petrol.
The reeds are developed by Joe Romano, a true friend.

Sorry for my bad English!


In italian:
Io sono un appassionato di motori 2T. Partecipiamo con le Aprilia RS 125 e la Cagiva Mito nel campionato Alpe Adria 125 SP.
[Vous devez être inscrit et connecté pour voir cette image]

La potenza del motore Mito si aggira sui 37,5-38 CV alla ruota a 11.300 giri (con l'Aprilia qualcosina in meno).
Questo è uno dei cilindri tipo che utilizziamo:
[Vous devez être inscrit et connecté pour voir cette image]
La fasatura di scarico è di 196 gradi.
Questa è la boccola di scarico:
[Vous devez être inscrit et connecté pour voir cette image]
La boccola non è circolare, nella parte interna più larga misura 35mm. Usiamo scarichi con parte iniziale circolare di Ø35-36mm.
Proverò a disegnare una marmitta con il programma gentilmente messo a disposizione. La lunghezza della boccola di scarico va conteggiata nel parametro “Lcyl”?
La distanza totale della boccola di scarico dal mantello pistone è di 35mm, la boccola misura 21mm (56mm totali).

Questa è una delle nostre marmitte, le realizziamo da soli:
[Vous devez être inscrit et connecté pour voir cette image]
Il diametro interno dello spillo è di 24mm, diametro interno silenziatore 28mm (fori mitraglia da 2,0 o 2,5mm), lunghezza 28cm:
[Vous devez être inscrit et connecté pour voir cette image]
Usiamo i pistoni Mahle, quelli realizzati da Ziegler per la Cagiva 500GP:
[Vous devez être inscrit et connecté pour voir cette image]
Il pistone Mahle ha il cielo piatto con banda esterna inclinata di 6° e fascia singola da 0,8mm NPR. Purtroppo Ziegler è morto nel 2007 e i pistoni ormai sono difficili da trovare... Ho comprato tutti i pistoni Mahle che sono riuscito a trovare. Quando saranno finiti dovrò farli replicare.
Usiamo il carburatore Dell'Orto VHST 28 Racing delle Aprilia 125 SP ritarato per il motore Mito.
Il rapporto di compressione è limitato dal regolamento tecnico a 13,5:1(misurato all'italiana, volume di 10cc).
Usiamo teste con conformazioni simile a questa però con banda di squish di 6 gradi e rapporto di compressione di 13,5:1:
[Vous devez être inscrit et connecté pour voir cette image]
La testa postata sopra ha un rapporto di compressione più basso. Con le ultime teste la banda di squish è il 48% della superficie totale del cielo pistone.
Usiamo una accensione Kokusan a rotore piccolo.
[Vous devez être inscrit et connecté pour voir cette image]
Abbiamo sviluppato la CDI programmabile e la centralina di gestione della valvola di scarico con l'aiuto di Borut (alias Zeeltronic). Per la Mito prima non c'era nulla di buono. Se può essere utile o interessante posso postare anche un grafico della curva d'anticipo accensione del motore Mito.
Usiamo benzina verde 102 ottani.
Le lamelle sono state sviluppato con l'aiuto di Joe Romano, ci ha dato una grossa mano. Si è dimostrato un vero amico.
Rispetto ai vecchi motori Mito SP abbiamo spostato il regime di potenza massima a regimi più bassi e migliorato la curva di coppia senza perdere in potenza massima.

Porting looks very good, also the exhaust seems apropriate and head design also great. 38bhp at the whell is very good, probably 44/45 at cranck?!

Cant you tell stinguer sizes, belly diameter and exhaust lenght used?

28 carburators? Then why Honda RS uses 39mm and Aprilia RSA 41,5mm

The small 28mm carburetor is imposed by technical regulations.
I have tried to reduce the loss of power from the crank to the wheel.

We won the last two championships with the Aprilia. Our engines are not bad... but with the Aprilia is easier. The the main work of development was done by the people of Reparto Corse Aprilia. Pellizzon (former test pilot and Aprilia) and others have helped us.
The technical challenge is with the Cagiva Mito. For Cagiva does not have a material or references, you have to get all by yourself. I like it.

If I remember correctly, the Cagiva Mito has a balance shaft that runs at the bottom of the crankcase, immersed in gearbox oil, which consumes a lot of power. Putting a piece of tube around the balance shaft so that its external shape become cylindrical, will save about 2 HP.

Frits Overmars a écrit:

If I remember correctly, the Cagiva Mito has a balance shaft that runs at the bottom of the crankcase, immersed in gearbox oil, which consumes a lot of power. Putting a piece of tube around the balance shaft so that its external shape become cylindrical, will save about 2 HP.

Somebody told me about this..
Thanks Frits, this evening I'll post the pipe drawing as I'll fit to the bike, and an interchangeable nozzle solution drawing, too.

Everyone speaks highly of Joe Romano. {mRk} what is the source of the NPR 0.8mm rings (I use Mito SP pistons in other engines)?

Header on the Cagiva pipe looks way too steep, never seen a 7deg taper

Frits Overmars a écrit:

If I remember correctly, the Cagiva Mito has a balance shaft that runs at the bottom of the crankcase, immersed in gearbox oil, which consumes a lot of power. Putting a piece of tube around the balance shaft so that its external shape become cylindrical, will save about 2 HP.

Yes, this works fine.

Institute of TwoStrokes a écrit:

Everyone speaks highly of Joe Romano. {mRk} what is the source of the NPR 0.8mm rings (I use Mito SP pistons in other engines)?

Header on the Cagiva pipe looks way too steep, never seen a 7deg taper

Joe gave me a lot of useful tips and contacts. It 'a very special person. He developed the reeds only for us, we are the only ones to compete with the Mito.

The NPR rings are difficult to find There are different types of NPR 0,8mm rings, some are good some less.
I've had rings from people who worked in Cagiva.
You can still find them but they cost a lot, € 40 for a ring. Too much for me... I can give you the contact.
You could ask Ferry Brouwer (Yamaha Classic Racing Team), he could have them.

I will draw and post the exhaust we use.

Here the final drawing, with the position of the bolted flange:
[Vous devez être inscrit et connecté pour voir cette image][Vous devez être inscrit et connecté pour voir ce lien]" border="0" alt=""/>
And here the nozzle's detail:
[Vous devez être inscrit et connecté pour voir cette image][Vous devez être inscrit et connecté pour voir ce lien]" border="0" alt=""/>
Nozzle is fitted into the baffle and rest in place with an outside bolt; the stinger is clamped at the end of the nozzle.
PS forgot how to post bigger images..someone could help me?????

I'll post the designs of a exhaust we use. The second exhaust is the result of the fos-pipe program.
[Vous devez être inscrit et connecté pour voir cette image]

Some advice or recommendation?