ESE's works engine tuner

[TZ350]

Thomas comes up with the goods again......... RSA ?



Transfers



Main Ex Port 66% of bore



Old bridge oilers glued up, so now we know for sure that gluing the piston works, just like Thomas said it would.

[kel]

Thomas comes up with the goods again......... RSA ?

Looks like a Chinese knock off

[TZ350]

Some interesting tit bits from:- http://www.pit-lane.biz/t117p570-gp1...es-aprilia-rsa

Jan Thiel
We did not flow the principal and secondary transfers separately.
In fact flowing the transfers makes little sense!
The important thing is more their direction and how
they influence upon each other.

Frits Overmars
The best place for a lambdasonde is in the fat part of the pipe where it least disturbs the flow, and in the top side so that it does not get fouled by oil.
If that is not possible, then put it so far away from the cylinder that there is a pipe volume of at least twice the cylinder volume between it and the cylinder. That way you can be sure that the lambdasonde will not be fouled by unburnt mixture.

I guess Jan is talking about Blow-Down here.

Jan Thiel
At high rpm there is some reverse flow, the transfer ducts becoming black, and even the
crankcase and carburetter bellmouth because of the entering burned gasses.
This happens because with raising rpm. the pre-exhaust flow becomes insufficient.
When rpm raises still more there is no more transfer flow and the engine stops completely.
So transfer flow depends completely from what is 'allowed' by the exhaust flow! We never used a lambda sonde.

Riley Will
The 125cc engine made 48 hp (sae) at the rear wheel. I have used my cylinder on the Rotax 129 engine where it made 50hp. Much of our technology has been derived from Aprilia. I believe I can make more with the reed valve engine by focusing development on the reedcage and inlet. However, it has been my experience that the mid range power of the disk valve engine is always superior. I have found over rev power of the reed valve engine to sometimes be eassier to achieve. In the past I would also produce more peak hp with the reed valve engine but the mid range maybe 7% less than the disk valve. Our 150cc engine when using Methanol has made 56hp and 24 ftlbs of torque. I love it for its simplicity. Our 250cc twin has made 104hp when using leaded fuel and Aprilia MW47 combustion chambers. I have also made tests on a 125cc disk valve engine with fuel injection. This made 10% more power everywhere than carburated!!! I want to spend more time in this area. At the moment we are fine tuning our 250cc twin engine for the 2011 superkart season. We have made crankcase, cylinder, and combustion chamber modifications in order to raise peak HP and over rev HP.



Frits Overmars
The JBB engine. It is a lot lighter and more compact than a tandem twin.



The JBB engine (created by Jean-Bertrand Bruneau who is a member of this forum), has two separate crankcases.
The crankshaft has a common big-end pin with a center disc which forms the separation. Hopefully the following pics will make it clear:



Riley Will
Those are the carburators used when burning methanol. It is needed not for more air, but to have the ability to move enough methanol!!! When running with Methanol, you can see your fuel tank dropping on the straights!!!!

[wobbly]

The unsupported disc between the cylinders is also the type of crank design as used in the SwissAuto V4 - Gp engine, that ended up as the Pulse 500 as run by some of the guys from the BSL500 team..This is called a flying web crank, but has the pins opposite to give 180* firing in adjacent cylinders.

One thing to note in the pics of the cylinder held by Thomas - the real RSA does not have any taper at all at the top of the duct divider ( septum), the end of the divider just has a small radius on each side.
This is to reduce the area ratio between the duct entry and the port exit.
Edit, here is a better pic I have just got.

[F5 Dave]

Ahh, I'd never seen the twin inlet single disc arrangement, just assumed like a tandem, but it makes sense & is way compact. Nice.

Makes you think if they still raced 500s they'd be well over 200 at the wheel. [sigh]

[kel]

Now that Rob has put a link to pit-lane.biz (my almost secret place for all things techo), I'd encourage anyone who loves race bikes to check it out. Its a French site so you'll need to use something like google translator (which can be amusing) although Jan, Frits and others do post in english, those clever Europeans tend to speak more than one language which does help. There's all kinds of super cool technical info on most racing classes plus pictures of just about everything. Enjoy!

http://www.pit-lane.biz/

[speedpro]

Interesting that the webs in the JBB engine aren't full circle. I have to wonder about friction and crankcase compression and balance factors. I presume the crankpin has a spline machined into the centre that the centre plate sits on, I can't see it being pressed into place. Very cool engine.

[TZ350]

One thing to note in the pics of the cylinder held by Thomas - the real RSA does not have any taper at all at the top of the duct divider ( septum), the end of the divider just has a small radius on each side. This is to reduce the area ratio between the duct entry and the port exit.

Hi Wobbly, I have heard you mention that before, it used to be that the entrance to the transfer duct was just a little bigger than the port window and that seems sensible, to make it like a funnel.

So why do they make the duct entry the same or a little smaller than the transfer port window now? Is it to reduce the gas velocity out of the port?

[wobbly]

If you look at the old Rotax pic it has a duct entry to port ratio of about 1.4.
The base gasket dimensions are virtually identical to the late model cases.
The RSA/RSW has a ratio close to 1.2, so its still tapered down to the port exit but no where near as much.
If you look at the Delivery Ratio of a full on 2T engine, virtually all the volume that ends up in the cylinder, is actually sitting in the transfer ducts, NOT the case.
The smaller this volume is, the quicker it can be accelerated thru the duct into the cylinder.

[F5 Dave]

putting paid to Bell's (or was it Jennings?) comment that it was virtually impossible to make the transfer entry ducts too big. Always challenge the classical wisdom I suppose.

[TZ350]

Got my cases back today, they have been bored for the RGV cylinder.



Cylinder fits Ok



The position of the reed block.



Speedpro told me there is a nice little curved ledge inside the cases that is just right for the reed assembly.



So the reed should fit Ok



Now I have to make up a spacer plate and reed block assembly, how hard can that be???.....

[Ivan]

how many horses are you planning out of this bike?

[speedpro]

So why do they make the duct entry the same or a little smaller than the transfer port window now? Is it to reduce the gas velocity out of the port?

More likely to "increase" the gas velocity in the duct. Keep in mind also that the port window is only ever fully open for a very small portion of the cycle. There could be a good case for reducing the duct size depending on application.

[TZ350]

how many horses are you planning out of this bike?

On this engine I am working to a Wobbly design based on the RGV cylinder and of course the final result is as much about workmanship as the design.

So I hope to do Wobblys design justice with my efforts and not let him down.

If the TF/RGV100 is anything like the Wobbly engine Speedpro built then it should be 30+ rwhp and have a good wide power spread of about 3.5-4k rpm and be quite useable.



You can see in this earlier dyno graph that Speedpros Wobbly 100 has a better spread of power than my 125. I expect that has a lot to do with the Wobbly-Pipes designed expansion chamber.

[TZ350]

Wobbly sent me an email (and permission to post it) re the shape of the RSA rotary valve disk. I had thought the soft closing may have been to extend the crank case packing by having a reducing inlet port window towards the end of the inlet period instead of a sharp cut off but it turns out it was more for mechanical reliability.

Interestingly the timings are much the same as I have been using on the GP, albeit the GP has a smaller inlet duct and port window,


Hi Rob
Here is a pic I just got from Frits, I asked about the RV timing as I am building up a Sim of the RSA/RSW.

He said that the opening wasn’t critical between 140 and 145, the closing between 85 and 88 depending upon the rider and track.

He said they tried opening timings all the way to 155*, but 142 to 145 was the norm.

The angle on the closing side is purely to help with wear on the case.
cheers
Wob