[GP125] All that you wanted to know on Aprilia RSA 125, and more, by Mr Jan Thiel and Mr Frits Overmars (PART 3) (Locked)

Riley, I would personally omit the inlet disk altogether and use my 24/7 inlet system.
But if it has to be a disk, 124 mm might be on the small side; 130 mm sounds OK.

Mic a écrit:

If you want to sell engines here in europe you should test with non power jet carb as power jets isn't allowed by CIK.

Mic, it is my understanding that electronically controlled power jets are not allowed.
I happen to know that Francis Payart is developing CIK-legal power jets for his FPE engine.

Dont go bigger than 130mm?

I doubt I will sell engines into Europe again, I found it very political and not very rewarding.  Australia has been an enjoyable market and I wish to provide them with something new to play with.  The CIK needs to get with the times.... Not allowing PJ is rediculous!  It does not add cost, it will lower them by helping the engines to live a longer life!

My EFI will lower the costs again in comparison to what 42mm carbs cost along with all of the brass that goes inside!  Not to mention that the EFI system seems to get better fuel economy...


Look out, ive learned to post pics;)
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Some of my work:
BRC125 Prototype
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BRC150
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BRC250FE
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EFI dyno curves from this week comparing old non PV cylinder with our current PV cylinder.
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Mule with Butterfly Throttle Body
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Mule
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frits, you mentioned a facebook page of BRC. can anyone post a link?

Frits Overmars a écrit:

Manuel Rainer a écrit:

Frits maybe you can explain the calculation method with the engine's torque curve and the exhaust pipe dimensions.

Just take the rpm value that you found for maximum power, use it in my simple exhaust concept
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and vary the speed of sound value in that concept until the calculated length coincides with the length of your pipe.

Thanks Frits

if i do this way i get the 587-588 m/s. so we can say that the RSA has a exhaust velocity around the 590 m/s.

thanks Manuel

Riley Will a écrit:

Dont go bigger than 130mm?

I doubt I will sell engines into Europe again, I found it very political and not very rewarding.  Australia has been an enjoyable market and I wish to provide them with something new to play with.  The CIK needs to get with the times.... Not allowing PJ is rediculous!  It does not add cost, it will lower them by helping the engines to live a longer life!

My EFI will lower the costs again in comparison to what 42mm carbs cost along with all of the brass that goes inside!  Not to mention that the EFI system seems to get better fuel economy...


Look out, ive learned to post pics;)
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Frits or Jan please correct me if I'm wrong but this cylinder looks newer than APC jugding from the bottom sidewalls of the main exhaust port. Could it be something between APC and APE time? I'm aware that it isn't a APD as I remember Jan saying this was an unsuccessful 7 port design.

Hello everyone. I'm back at home for two days, and I am not too bad.
Not easy to write at this time in her bed. Sitting position banned, but I can read your messages.
Thank you all for your wishes. At very soon.

For those who love "butchery"  
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Frits Overmars a écrit:

koenich a écrit:

frits, you mentioned a facebook page of BRC. can anyone post a link?

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hm doesn't work, maybe I need to like their page first?

koenich a écrit:

Frits Overmars a écrit:

koenich a écrit:

frits, you mentioned a facebook page of BRC. can anyone post a link?

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hm doesn't work, maybe I need to like their page first?

No idea; I still do not understand how Facebook works.

Koenich,


Look me up on Facebook and friend request me

Riley Will

Anyone want to impart their wisdoms to assist with the design of a new Mule testing engine for 125cc and 250cc twin cylinder development?

Riley Will a écrit:

Anyone want to impart their wisdoms to assist with the design of a new Mule testing engine for 125cc and 250cc twin cylinder development?

Past experience taught me: make sure the engine has its own clutch. And give the cases ample coolant passages (for preheated, thermostat-controlled boiler water) so you can keep the temperature constant during tests.

Why is the clutch necessary? My dyno is from Soft Engine. It is intertia type and has a clutch that I can unload the engine with. Do I still need a clutch on the engine?

Riley Will a écrit:

Why is the clutch necessary?  My dyno is from Soft Engine.  It is intertia type and has a clutch that I can unload the engine with.  Do I still need a clutch on the engine?

You'll need to draw faster than Lucky Luke....
If the dyno clutch is OK, you do not need a clutch on the engine.

Frits,

My wife says I'm the fastest she's seen.... 

Seriously, what would be the drawback from going with a disk of 135mm-140mm diameter? In your opinion, what may be the benefits?

It appears my original cylinder casting maybe better than the standard APC cylinder. Frits, can you look at MIC's question and porting pictures? Rather than a whole new cylinder tool, maybe I am able to just modify the exhaust port portion of the tool...

My target is for case volume to be 700cc.

As for inlet, some of the disk valve kart engines years ago offset the inlet in the direction of rotation of the crankshaft so that the fresh intake was not seeing the wide section of the connecting rod as much. Any opinion here if this is an area in your opinion to focus design energies?

Riley Will a écrit:

what would be the drawback from going with a disk of 135mm-140mm diameter?  In your opinion, what may be the benefits?

The drawback would be the higher friction. The benefit would be more liberty in shaping the inlet port. The port would also open and close faster.

Citation :

It appears my original cylinder casting maybe better than the standard APC cylinder. Frits, can you look at MIC's question and porting pictures?  Rather than a whole new cylinder tool, maybe I am able to just modify the exhaust port portion of the tool...

I went back a couple of days but I only found one cylinder picture from MIC, so I assume that is what you are referring to. Judging by the exhaust ports I would say it is a relatively 'young' cylinder, but the exterior suggests otherwise. This would be a question for Jan to answer. And of course you could take another look at the many pictures that Francis Payart has posted here, both from the RSA cylinder and from his own FPE cylinders.

Citation :

My target is for case volume to be 700cc.

Sounds fine to me.

Citation :

As for inlet, some of the disk valve kart engines years ago offset the inlet in the direction of rotation of the crankshaft so that the fresh intake was not seeing the wide section of the connecting rod as much.  Any opinion here if this is an area in your opinion to focus design energies?

The inlet port area is so large that you won't be able to do that; the con rod will be in the way no matter what. That was the main reason for Jan to design the RSA's rear inlet disk.

Hello Riley,
 
I would certainly NEVER make a single cylinder engine without a balancer shaft!
The cylinder picture seems from an APC, or the later APG that was made because
the APC casting models became too old after casting more than 1500 cylinders.
Exhaust ducts were CNC machined from about 1999 onwards.
To save money we had the exhaust core case CNC machined.
This was done for production racer cylinders.
A lot of different exhaust ducts were CNC machined.
Independant of the type of cylinder.
We had machining prograns for the top and bottom halves.
The one on the picture was one of the latest I think.
This was done to have a greater distance from exhaust to A-transfer.
It seemed to work!
Making the rotary valve bigger than 126 will give no advantage I think.
One engine was made with a 128 disc, but it was not better.
The RSA engine was a bit of a disappointment to be true.
It only gave marginally more power.
To keep water temperature constant our cooling water was mixed with cold water,
controlled by a thermostat.
But for an inertia type dyno I would advice to preheat water and engine.
Otherwise you will get too optimistic results.
Many people tried fuel injection, on a dyno it always works fine.
Later, on-track, there are almost always problems with driveability.
I hope you succeed, as carburettors are terrible things on a kart-engine!

Jan,

Thank you for posting! Do you think I need to add the complexity of the balance shaft to my Dyno Mule engine? If I was building a single for competition then I would for sure. Is this short sighted on my part?

Have you seen the Dyno test I posted on Facebook? It seems to have the same reaction in acceleration as I see from a Del'Lorto.

I am testing tomorrow with my APC with ported exhaust port like APF cylinder. Way bigger/wider sub exhausts, 202 degrees duration main exhaust, dug out sub exhaust ducts.

My development is for superkarting, maybe the efi will be more forgiving than with a bike. We will see.

Thank you and Frits for the great input.

Having a balancer shaft can make a big difference, especially if you compare a carburettor with EFI.
I once tested an engine with and without balancer shaft.
Without it gave 1,8HP less!
Due to a less constant fuel level in the floatchamber I think.

Hi Jan e Frits, what kind of balancing cranckshaft percentage I can use on my 100 cc engine for drag race?
It's an horizzontal layout cylinder with CVT trasmission, so I want to achieve maximun power around 14 krpm.

luca.lorigiola a écrit:

Hi Jan e Frits, what kind of balancing cranckshaft percentage I can use on my 100 cc engine for drag race?
It's an horizzontal layout cylinder with CVT trasmission, so I want to achieve maximun power around 14 krpm.

50% balance factor for the crankshaft and 50% balance factor for the balance shaft, Luca. Cylinder layout and rpm do not play a role here, unless the chassis develops a resonance at some rpm; then you may have to experiment a bit.

Someone used to asymmetrically balancing the crankshaft so that it will fall forward, in the direction of rotation. Have you ever tried it?

Here is an EFI test from last week showing start up, acceleration, throttle response and idle.

2-stroke development is definitely not dead:happy: 

Around here people seem to have better results when there is a little bit more weight in one side of the crank than on the other, its called positivity, because the crank as the tendency to move forward, Bell also calls it a similar name, when you say 50%, is that when the crank is in a pair of parallel bars(with the piston mounted/equivalent weight in the rod), it will tend to roll until the big end is at 0/180º(horizontal)?