[Technique] RossiGRM 2strokes boat engine

Hello , Mr Rossi , do you know Lauro Falc ?
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at the end of this pfd document we can see , aluminium power boat exhaust .

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He is the producer of a proto engine for CVT using in scooter sprinter racing class .

Here is some fotos of the baby :

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On this Video you see all kind of boats in this categorie...
125ccm, 175ccm, 250ccm, 350ccm, 500 and 700.
These are boats from another engine company "VRP Engineering".
The Owner of VRP is Carlo Verona and he comes from Motorbike.

This is the factory team of VRP Engineering:

@ROSSIGRM:
Giuseppe, after seeing the video I have a couple of questions (I always have a couple of questions 8)).
When you want to turn around a buoy, do you need to cut the engine power to get the nose of the boat down (to end the wheelie, in motorcycle terms)?
I see a big rooster-tail of water hitting the expansion pipes. Not just from the boat itself, but also from other boats.
This looks like a rather uncontrollable cooling factor to me. Have you considered shielding the pipes from the water spray?

I am sorry SweatDreams: i tried to improve the video show (the website doesn't like so much the "iframe") when suddently everything has disapeared...

Could you put the link one more time, please?

i think that Mr.rossi engines are very incredible .. here there are some links for videos of this fantastic type of motorsport
Regards to all

Hello Marc,
sorry i see the video on my computer...
Please take a look of this factory-team-website: demmler-racing.com
On the button "Media" you can see the video...

Or look to Youtube and looking for demmler racing!
I hope it works...?!.

The reason because I was on this forum,was for a pure passion for engine and for learn:pipes, head,cylinder ext. ext.
It seams now that is coming for advertaising boat racing,is not my intention.
My cylinder is coming from Aprilia and Lauro Caforio from Falc Racing ( very good friend) made for me the cast mould of the transfer and exaust. The outside of the cylinder and all the other cast mould are made from Gattuso Pierpaolo ( he is the "G" letter of the GRM ).

For Mr.Frits: as You seen in video, we start from a jetty,the engine is dead quiet the last 30 second, red light from 5 to 12sec then start: the 2 crew that the driver have on his back are very important for a very fast start. Then straight for 500/600 mt, release the trhottle one or two time for reduce the speed ,about 120kmh for the 125 engine,160khm for the 250 engine, 170 khm for the 350 engine, 180khm for the 500 ( only for VRP...not my one...). half of the turn can be done with the pipe close,the driver feel the water condition and where he can drive the boat...a close to the boa need all the pipe out with the engine down to 1000rpm or less, a big turn keep the engine at 11000 with 3/4 of the pipes. At the end of the turn the driver close slowly the pipes to 13000 or more... wait 5/6 second straight and will be the next turn...again for 8 laps.
Drive the boat is funny, and not so hard like a bike,we have good driver over 40 years old....(me)
The pipe are washed from the prop spray on the boa sometimes,in straight the spray is under the pipes and not reduce the temperature.
Sorry for my english...this is forum please be patient.. Regards

Giuseppe grazie. Your English is quite good. For me it would also be fine if you would write in Italian, but I do not know about the other forum members...

Citation :

The pipes are washed from the prop spray on the boa sometimes, in straight the spray is under the pipes and not reduce the temperature.

Then I got the wrong impression from the video; there it looked as if the pipes were in the spray most of the time.
But what about the spray from other boats? That was what I meant by 'uncontrollable cooling'.
When I blow cold air over a pipe during a dyno-test, I may lose 1500 rpm. I never tried it with water, but I suppose the rpm loss must be even worse...

Citation :

the driver feel the water condition and where he can drive the boat

It sounds like motocross, where the track changes with every lap. I never thought about it like this for a boat; I always thought water is just water.... Thanks for giving me a bit more understanding, Giuseppe.

Frits, Jan and others...I would like to ask for help answering a couple of questions. On the surface these are simple questions, but I know that nothing about 2 strokes is simple.

1)Most kart engines that I have ever seen have the reed cage positioned parallel to the connecting rod. Is this the preferred orientation versus positioning the reed block parallel to the crankshaft? Does the orientation matter?

2)I have followed with interest the Aprilia thread. In that thread there is a power curve that shows that the rotary valve motor significantly outperforms the reed valve motor. The rotary valve has a number of advantages including better control of intake timing and it offers unrestricted flow from the carb into the motor when the valve is open....there is no reed block in the way. Is it possible that adding a second carb and reed valve to a motor would increase the available flow of air and fuel and improve the performance so that it would perform closer to the rotary valve engine? I am making the assumption, perhaps not correctly, that some of the performance difference is due to the disruption in flow caused by having the reed cage in the intake tract.

3)I am told, that at high RPM the reeds never fully close...is that true? How does one know if the reed cage is large enough for a specific application?


Thanks, David

At the moment most KF-type kart engines (no gearbox, just a centrifugal clutch) have their reed cage vertical (parallel to the conrod), while most KZ-engines (with 6-speed gearbox) have a horizontal cage. Some brands (Maxter, for instance) even offer a choice of KZ-engines with vertical or horizontal cage.
I would say that the vertical cage gives a flow that cools and lubricates the big-end bearing a bit better, while the horizontal cage gives a better flow and a little more power.

It is not only possible, but 100% certain that a second carb and reedvalve to such a kart engine would increase the flow and the performance, but that is because these engines have rather small carburettors (30 mm for the KZ, even smaller for the KF). Alas, everything is homologated; such changes are not allowed.

The power curve in the Aprilia thread that you mentioned, shows GP-engines without restrictions on carburettor size; even then the rotary valve is clearly superior. adding a second carb and reed valve would not alter this difference.

Normal reeds close during every crankshaft revolution, even at maximum rpm. You could fit reeds so flabby that they won't close at high revs any more, but then it would be impossible to get decent carburation, and the flow restriction would be present nonetheless....
Finding out if a reed cage is large enough, is simply a matter of bench testing.

Frits....thanks for the reply. We are in the process of building a reed valve motor for outboard racing using Mr. Rossi's crankshaft and ignition with an Aprilia Cylinder and head. The crankcase will be made from billet. I am going to incorporate as much of the intellectual capital from this website as possible in this motor. We are already testing a similar motor with a rotary valve that we built with 2 balance shafts.

We run these motors on methanol with 41mm Dellorto carbs through a V-force reed cage. I was thinking that for this application a second carb and reed block might be helpful.

I am interested to know if you or others on this forum have opinions on the best reed cage for a 125cc motor?


Also, I am inclined not to to use a crank shield to separate the crankcase from the cylinder. Without the shield I think we can get a better shape for the transfer passages in the case.

Outboard racing is a lot of fun....it is one of the last places where the rules for 2 stroke motors are open....really the only rule is bore and stroke. Even here though it looks like a 250cc 4 stroke is coming to replace the 125cc 2 stroke motor and will be used in competition soon...this will happen in Europe first. So far we have no plans to adopt this formula in the US.


Thanks, David

Hi,

in our RS 125 engine, we use a V-force2 from CR 125 moto-cross model. We have good results on all the powerband, especially mid and over-revs...as we stop 2stroke, we've never tried V-force3 but it could be interresting.

On the dyno, 1 hp on mid and 0.5 hp on top and much better overrevs...

Yes , VF2 seems to be the best option for RS125 h***a

ridley a écrit:

And why not an intake pipe length varying according to engine speed and throttle opening? I am currently working on this project.

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Et voila

Is this the variable exhaust length system Cagiva once tried?
Have you met Franco Brusco who is working there?

Jan Thiel a écrit:

Is this the variable exhaust length system Cagiva once tried?
Have you met Franco Brusco who is working there?

HI JAN
Not Franco , but the olds mecanics from Aermacchi Harley and later Cagiva.
IYes it s the Cagiva system with an ignition-valves "magic box"piloted servo motor

For who likes to do experiment...Winter time is that...carburetor with Dellorto bottom parts, short as possible on the top: on my 500 engine 4 cilynders there are space problem...[img][Vous devez être inscrit et connecté pour voir cette image][/img]

where is the needle?

ROSSIGRM a écrit:

For who likes to do experiment...Winter time is that...carburetor with Dellorto bottom parts, short as possible on the top: on my 500 engine 4 cilynders there are space problem...

next step : injection ? is it allowed by your regulations ?

nice!

ROSSIGRM may you post more pics of your carburetor please ?

it looks like a Lectron...

the carb is without needle, the slide is exactly over the atomizer and is tapered, it open the hole not perfectly as the needle, but the main important is that the boat engine work for 95% of a lap at full throttle, sure it is not good for a motorbike..
We try the injection, a homemade type (two friends with the electronic passion...),two injector for cylinder: we need about 0.8/0.9 liter a minute, but for the moment it is not working....burned about 15 used pistons....

I see that there are a number of companies selling electronic control for an electronic power jet. However I have not been able to find any companies that sell the electronic power jet unit itself.Where can I find the electronic power jet unit for the carb? This type of setup might be useful on the boats as well.

David,

In the states you can get the Del'Lorto Power Jet from Herdan Corporation. Ask for Herman 610-562-3155. It is a simple solenoid. You should get the other parts that make up the circuit as well. Let me know if you need any assistance there.

Riley

and another variable exhaust length system :

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A propos de pot à longueur variable,

je vous présente mon élucubration,

jamais testée... (excusez le croquis, c'est du Paint...)

La sortie du pot devient annulaire, le cône coulisse sur 3 patins plus palier de la tige de commande.

Prévue à l'époque où je roulais sur une "bleue" (...+/-1980...) avec utilisation

du déplacement dû au variateur au lieu du moteur électrique asservi...

(plus simple la tige est attachée au cadre)

Comme autocritique, je dirai que ce n'est pas forcément la partie

la plus efficace à moduler.


Comme avantage, pas de fuite (de bruit), moins d'effort.

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