ESE's works engine tuner

[TZ350]

TZ, are you going to see Yamaha rod to get those revs without smoking the poor RG crank?

AM6 rod kit.

There are a couple of these rotary valve Suzuki RG50 engine conversions in the works. Two 50cc another, possibly a turbo 70 or an 85. We have also found ways to get 110 cc's out of one of these. If the 110 materialises and works. We will take it to Christchurch for the next Battle of the Buckets.



Basic AM6 stuff is pretty affordable of Aliexpress.



After transfering the RG50 primary gear. GN125 clutches can be made to fit as well. Stay tuned for details.



Also GN125 clutch spring kits can work wonders for a standard RG50 clutch.

Rotary Valve Suzuki RG50

[Vannik]

I suspect EngMod2T as good as it is, is based on known good engines. We never got to see the ultimate RS125 and how big its crankcase volume would have been.

EngMod2T and 4T is not based on any engine but on thermodynamics and gasdynamics. Any shortcomings is from my lack of programming skills and/ or misunderstanding the physics. And from modeling combustion and scavenging as quasi-dimensional and not full 3D.

[F5 Dave]

I just usedDT175 springs and TS plates allowed 4rather than 3. But 100 power may unravel that.

[TZ350]

EngMod2T and 4T is not based on any engine but on thermodynamics and gasdynamics.

Good to know, thanks. I knew it was good and now understand why.

I just used TS plates allowed 4 rather than 3.

Yes, I remember you sharing that info. We have been doing that ever after you clued us in.

[Noxin]

Many team engineers at the track increased that to 0.7 as it was easier to tune and rev'd slightly harder.

What was the main effect that simplified the tune and harder rev?
Was it the lowered compression ratio or the squish gap itself?

[wobbly]

Increasing the squish gap, decreases the MSV. Small changes have quite significant effect on this parameter.
In the RSW going from 0.6 to 0.7mm gives a change of 48M/s to 42M/s = 12.5%

Lowering the MSV is analogous to retarding the ignition timing, as the reduction in the speed of the turbulent eddies exiting from the squish annulus ( curtain area )
reduces the flame fronts burn speed thru the chamber - also with the upside of decreasing the losses due to compressing the trapped mixture later.
Retarding the timing or reducing the MSV, thus has the mixture burning later in the cycle, and this puts less heat into the piston and more heat into the pipe.

There is a minor effect from reducing the static compression ratio, and this has similar effects as the reduction in MSV - more heat into the pipe
As far as tuning goes the lower com and reduced flame speed allows higher egt numbers without getting into deto, giving a higher bulk gas temp and thus increased wave front speed thru the pipe = more overev power.

[TZ350]

Some posts on crankcase volume.

Originally Posted by Frits Overmars
In order to take full benefit of a large crankcase volume you need free-flowing transfer ducts. That means: large cross sections, short gas column lengths and large time.areas.

Originally Posted by Frits Overmars
An Aprilia RSW125 has a TDC crankcase volume of 650 cc. An RSA125 has 675 cc and a bit more power. See where this is going?

Originally Posted by Frits Overmars
Increasing the crankcase volume has several consequences. One of those is that the flow through the carb will be more even, less violent, which usually results in a leaner mixture.

Originally Posted by Frits Overmars
make sure your crankcase volume is not too small. I have seen lots of cases with too little volume, but none with too much yet. The optimum primary compression ratio is probably less than 1.3.

Originally Posted by wobbly
In my testing I have found no more power going to a bigger than 1.3 case on a reed engine.
This is a function I believe of the efficiency of the rotary valve intake system being able to better fill the case at high rpm,using the 1.24 as Frits has described , but having said that I have only just crept over 50 Hp with a 125 reed, and the Aprilia RV made alot more than that, so maybe a huge case simply isnt needed at the lower bmep.

Originally Posted by Frits Overmars
Off the pipe you need a pump with the minimum amount of dead volume; on the pipe you'll want the engine to breathe directly from open air (mixed with a bit of fuel and oil). But that oil has to pass through the crankcase to keep the bearings happy. Hence my 24/7-setup

Originally Posted by wobbly
There are several issues involved with the reed engine and its case volume - that has effects not seen in an RV setup. The bigger the case the less are the pressure swings from piston movement and the pipe action ( assuming the same depression at the Ex port created by the pipe ) around BDC.

This changes the tuned frequency of the case vol, but this also requires thinner reeds to get them open fast and far enough. Of course changing the reed stiffness then changes the intake tuned frequency,they then hit the reed stops and flutter uncontrollably - and so it goes on and on.

I tried machining the KZ10B case back to make the volume smaller as I already had the 5mm laser cut spacer from a test making the case bigger by pushing the reed block outward. This failed miserably, so of course you then go the other way - this also failed,but only partially in that I did not then try differing reeds to compensate as I should have.

Adding a spacer behind the reed block HAS NOTHING to do with the intake length, this is already as short as it can be, with the rubber manifold recessed into the reed stuffer.

All I can say is that from a huge amount of sims and real world reed engine testing, that a very well tuned engine with good power capability ( bmep ) likes the case down near 1.3.

An engine with less power ( bmep ) capability ( for whatever reason ) tends to respond better to the case closer to 1.4.
When you are making 8 Bar and or 14 Bar BMEP of course these exceptions to the norm tend to prove the rule of thumb.

Originally Posted by Frits Overmars
The smaller crank will give the pipe more crankcase volume to breathe from. This larger volume will also lower the resonance frequency of the inlet system, hence the drop at high rpm. It can be compensated with a shorter inlet tract, a bigger carb diameter and a later inlet closure. To put it real simple: if you have more volume, you need more time to fill it. But more time, i.e. later closure, has adverse effects at low revs. So my preference is a shorter tract (unless you go the 24/7-way and employ a reed for the low revs, and swing it out of the way at high revs).

Originally Posted by Frits Overmars
crankcase compression ratio = TDC-volume / BDC-volume
TDC-volume = 680 cc (I'll take your word for it)
BDC-volume = TDC-volume - cylinder volume
cylinder volume = 173,7 cc
BDC-volume = 680 - 173,7 = 506,3 cc
crankcase compression ratio = 680 / 506,3 = 1,343
And now for some reverse engineering:
what TDC-volume will give a crankcase compression ratio of 1,43?
TDC-volume = comp.ratio / (comp.ratio - 1) * cylinder volume
TDC-volume = 1,43 / 0,43 * 173,7 = 577,7 cc.

Some of the posts where I came away from with the idea that bigger was better for rotary valve crankcase volume.

I found the EngMod2T section where crankcase compression ratio is calculated.



I have a case volume of 120cc on my rotary valve 50. So will try a series of simulations using 1.4, 1.3, 1.2, 1.15, 1.1 and see where it goes.

Wob favors 1.23, I have great faith in EngMod so it will be interesting. Give me a bit of time to develop the Simulation for the current 50 and run it. When the engine is together we will put it on the dyno.

[wobbly]

Its not that I favour 1.23 - that's just what has been proven in the RSA, and when I ran bigger in the sim of that engine, you can see it lost considerable power everywhere.

120cc in a 50cc engine is insanely small @ 1.69 CCR
Getting to 1.2 CCR will need 264cc under the piston - obviously screaming out for a long rod and plenty of crank clearance in the case.

I see no point in going up as small as 1.3, as that is guaranteed to loose power - Jan has been there done that when he changed from a 115 rod to a 120.
You don't need to use the calculation page for CCR - simply put in the cc or the ratio in the engine dialogue page and the code does the rest, just be sure to invoke the " include the transfers " radio button.

Regarding testing your rotating valve cover idea, the code will deal with a step in area at the end of the manifold, exactly as it deals with a step or discontinuity in the pipe
where the manifold bolts on.
It cannot know the step is asymmetric, but that is taken care of reasonably well with the changes in timing you will enter.
The pipe step functionality is well proven to represent reality, even when those steps are just 1/2 moon's at the top and bottom of the duct exit - its the area change that is the overriding feature
in modelling the effects.

Neels has done alot of work recently on updating the functionality of the Rotary Valve inlet modelling, so you will benefit from that immediately.

[TZ350]

120cc in a 50cc engine is insanely small @ 1.69 CCR Getting to 1.2 CCR will need 264cc under the piston -

My gestumit calculations of 120cc at bdc are obviously badly out. As is, this motor will have more crankcase volume than a standard RG50.

I will have to wait until the motor is assembled so I can do a proper liquid measurement. Thanks for your comments, very helpful.

Crankcase Compression Ratio
TDC-Volume / BDC-Volume
120 / 70 = 1.7
170 / 120 = 1.4
270 / 220 = 1.23 CCR

[TZ350]

.

Aligning up the primary drive gears. AM6 crank and RG50 clutch basket.



First step is to cut the starter gear of the back of the RG50 clutch basket.



The next step is drill the hub so it slides further onto the input shaft and then make a driving coller for it. I made this one out of an aneld engine sprocket.



As everything has moved inboard. I made this basket for the clutch release bearing.



All good. For a bigger engine you could use a GP/TF/TS five plate clutch. There is plenty of room under the Suzuki RG50's clutch cover.

Rotary Valve Suzuki RG50

[TZ350]

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This is what a really wild rotary valve looks like. Interestingly, on the dyno it started easily, made very good power, and even idled. Throttled well enough on the dyno but I was not game to try it on the track. I had heard the stories about the difficulties of tuning a late closing RV and was not keen to put the time into it. Another day maybe.

[F5 Dave]

Rob, just leaving the large area of Suzuki 1/2 case reed out will create a large area of mixture to the rear side of the case. I'd far prefer it in the transfer area where it can quickly be drawn into the cylinder. Gas will still need time to accelerate and move.

[TZ350]

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Hi F5. Yes, lots of stagnant volume. Unsure about it myself. Latter plan is to have something removable to fill that void. Going to try to get sensible dyno results for comparison. But really good back to back tests that give some confidence seem hard to achieve in my experience but we will give it a go.

Currently trying to find some two stroke formula that makes up for the scarcity of up to date two stroke machinery available in NZ. Not many Derbi or Aprilia 50 engines around or even Aprilia 125's. Mostly last century Suzuki farm bike stuff.

[TZ350]

Crank stuffers? An Aprilia RSW125 has a TDC crankcase volume of 650 cc. An RSA125 has 675 cc and a bit more power. See where this is going?

My quest for greater crankcase volume was sparked by reading posts like this.