ESE's works engine tuner

[bucketracer]

TeeZee had one look ... ... and went off for a lie-down .... I think he is ....

[TZ350]

EngMod2T

For something different Page 400 is going to be the basic info for building a 30+hp Suzuki GP125 taken from the EngMod2T simulation files.

Crank HP. Simulated Dyno Graph from EngMod2T using an early RS125 pipe.

EngMod2T's main screen for developing the model.

Basic engine dimensions.

Exhaust port dimensions.

Transfer port and duct dimensions.

Transfer port cylinder entry design and angles.

[TZ350]

EngMod2T

Inlet port and disk timing info.

Early RS125 chamber layout.

24mm pumper carb and inlet tract model.

Combustion data for a flat top piston.

Air cool temp data.

STA's or Specific Time Areas.

[husaberg]

I am only a little jealous .... so there.

Don't be jealous your one actually has all the other bits that make it er..go under its own motive power. More importantly stop as well.
Ps don't panic about the 250cc bit on the side its only because it has an NSR250 cylinder and head on it. It seems they just bolt straight on

[TZ350]

This lot should have been on Page 360 but I was a bit slow getting around to it ….

How much difference do the carbon pipe covers and or pipe lagging that Aprillia and others used to run make HP wise in top end?
Is there still a place for them or has the electric solenoid PJ rendered them redundant?

"Is there still a place for them?" I should think so; look at the Aprilia RSA125. There the cover does two things: shield the pipe from a cold air stream, but more importantly, as you can tell by the shield covering only the top half of the pipe: shield the crankcase from radiated pipe heat.
How much difference? We can only guess (which I avoid as much as possible) because nobody ever took the trouble of measuring the difference on a real track (were measuring the power would not be simple anyhow). The crankcase-shielding will give more power everywhere and the pipe-heat conservation will give more overrun which is extremely import for lap times.

The exhaust open point has very little to do with creating power due to "pressure" on the piston for "longer" with lower timings.
The gas pressures soon after TDC ,that creates the real power, is up over 80 bar, the pressure at Ex open is a couple of bar at best.
Moving from 200* to say 190* creates jack shit extra exertion of pressure on the piston to create torque, that then creates HP.
But the real issue is that down at 190* duration we get a huge amount of superposition of the gas pulse exiting the exhaust, on top of the residual pressure at the port.
This adding of a new pulse on top of an existing residual pressure means the wave front running down into the header has a huge relative amplitude, and this creates a huge depression at the port around BDC.
This also means we have port/pipe resonance over a much wider range and at a much high higher level than can be achieved at 200* duration.
In a conventional design we are forced into a corner by needing to create as much BlowDown STA as we can, and raising the timing is the only available route.
This pushes us away from the ideal port/pipe interaction timings, but is a compromise we are forced to accept to create the + 200psi bmep's needed, to be competitive.
Just another small detail that many overlook, or are unaware of.

With regards to adjustable length pipes For (Expansion chambers). I seem to have picked up that they at least mostly lengthening for low end power.

Has anyone tried ones that just shorten for top end or a least over rev potential to me that would be a more logical solution?( I am not always logical mind you)
I know Cagiva ran a hydraulic system and someone posted a solution you like on pit-lane but I can't access the pic I have a log in and it would let me in?

You have to stay within certain length percentage limits for all elements of the exhaust system; you cannot make one part a lot longer or shorter in relation to the others without losing power somewhere.
It is best to concentrate on getting all dimensions correct for maximum power. In the high gears you don't ride low revs and in the low gears you'll have enough low-down power left to pull a wheelie or spin out the rear wheel (I'm not talking about buckets though, so you might want to reconsider your case).

If you have a decent setup for angle*areas, pipe, carburation and ignition, the necessary overrev potential will come naturally; no need to sacrifice maximum power in order to make it rev a little higher.

The wide septums between the transfer ducts is there for two reasons.
One it reduces the duct entry area, and thus the ratio between the port and entry areas.
This drops the volume of the duct.A smaller volume sitting at the port has less inertia that the pressure ratio across the port has to accelerate into the cylinder.
Also consider that if you calculate the delivery ratio at full power and compare this to the cylinder swept volume of the cylinder, the air/fuel mixture sitting in the ducts
is more than enough to fill the cylinder - the is very little "flow" from the case, around the duct and into the cylinder in reality.

Secondly, the front and rear wall radial angles of the ducts are maintained all the way from the port, out to the duct entry.
As in 4T ports, trying to "bend" flow in two dimensions concurrently,lowers the bulk flow rate considerably.
Thus the ducts taper all the way from entry to exit, but only change direction in the one plane, around the short turn to give the correct axial entry angle.
The old bullshit you see of sharp divider edges is just that.
Only supersonic aircraft have sharp leading edges on the wings,and we certainly arent dealing with supersonic flow in transfer ducting.
Any flow loss due to the corners on the flat topped septums is way offset by the better directional control and reduced volume of the duct acting to fill the cylinder quicker.

The outer transfer duct radius is utterly unimportant; there the charge has no option but to go where the duct wall leads it. But the inner duct radius is very important: it should be as large as possible to avoid flow detachment. If you manage to keep the flow clinging to the inner surface (the Coanda effect), there will be less pressure-absorbing turbulence, so the flow will meet less resistance, transport more mass and deliver it where you want it to go.
The golden rule of flow: look for sharp inner edges and remove them. It always works.

The radii at the bottom bore edges, as visible in the picture above, yielded 1 HP; that's about 2% of the total power. The egdes where the transfer port windows cut the bore, should not be radiused; you do not want to promote inflow of waste gas into the transfer ducts. Here only the top and bottom edges should be chamfered lightly to make life easier for the piston ring.
There should be no widening just before the port exit; the duct cross-section area should gradually move from entry area to exit area. And with the inner curvature of the duct fixed, this more or less lays down the shape of the outer curvature.

Assuming that the flow in a duct will accelerate faster as a result of narrowing that duct is an ineradicable misconception. If it were true, it would mean that a duct narrowing to zero would yield an infinite flow velocity......
Flow velocity depends on the pressure difference between entry and exit of a duct, and in the case of an engine, where the flow constantly accelerates and decelerates, it also depends on the column length of the mass in the duct. It does not depend on the column's cross-area; twice the area would mean twice the mass per mm column length, but it also means that the cross-area exposed to the pressure difference is twice as big.
A smaller cross-area can have the effect that because of the reduced mass flow the pressure in the crankcase does not fall as quickly, which in turn may lead to a longer-lasting acceleration of the flow and thus a slightly higher top speed. But it will also mean less mass transport during the transfer phase.

The duct entry area of the Aprilia cylinder's B-ports is slightly smaller than their port exit area. This stems from the old obligation to develop cylinders that had to fit the existing crankcases of the Aprilia RSW engine, of which there are hundreds around. the RSA engine did not have this limitation, but simply enlarging the B-duct entries disturbed the scavenging, so the ducts were left as they were (and remember: while the B-ports' exit areas are only open part of the time, the entry areas are open all the time).
The transfer timing is 130° for the A-ports (they are really close to the auxiliary exhaust ports) and 132° for the B-ports and the C-port.

so would their be a (correct) ratio between c/case volume and transfer duct volume for a high performance engine?

Not really. The RSA's TDC crankcase volume is 675 cc (for a 125 cc engine!) but most of this volume is in the transfer ducts.

also on the rsa cylinder the liner has an opening in front of the boost port, while the honda 250 production racer has not,in the honda this is directly in front of the inlet from the reed block and appears to be an obstruction to the flow.

Over the years Honda has produced cylinders with and without the lip that your picture shows, sometimes both types in the same production year. But flow through the C-port is not the most important item of a fast cylinder.
Another point to help you make up your mind: compared to a Honda RS125 or RS250 the Aprilia RSA125 produces about 20% more power per cylinder....

... the important thing is that lower exhaust timings need bigger header diameters...some simple calculations, I have included one variable, the speed of sound. Starting with 550 m/s will get you in the right ballpark, after which you can vary this value according to your findings. Final remark: the calculation of the tailpipe restrictor diameter is critical: you can only apply it to engines that are thermally sound. Air-cooled engines are not...

Page 370 ….

The ring peg is right opposite the exhaust: the only decent place for it. Each time the ring passes over the exhaust port, it bulges out a little and then gets shoved back in its groove when it runs over the top and bottom port edges. If the ring peg is not diametrically opposite the exhaust port, this shoving back will cause the ring to rotate in its groove and every time it will hit the peg from the same side until the peg works loose....

Don't worry about the ring gap running over the C-port. The Aprilia's C-port is now 15 mm wide, but it has been as wide as 22 mm and even then there were never any ring problems.
Generally speaking you can say that the ring gap is safe over a C-port width of up to 40% of the bore. For steel rings that is; I never tried it with cast iron.......

The notch in the crankweb triggers the ignition. There's a Hall sensor at the crankcase looking at the crankshaft circumference. That gives a more accurate timing signal than a sensor looking at the end of a swaying shaft.

Below are some pictures of the Aprilia RSA125; the red arrows indicate the ignition sensor.

That notch for timing reminds me of one of the cleverest triggering setups I have seen.
In the SwissAuto/Pulse flying web engine there were two magnets at 180* in one crank web with only 1 sensor, setup much as the pic of the RSA125.
I spent ages trying to figure out how it worked, untill one day I grabbed another magnet and discovered that each one inside the crank
was orientated N & S pole outward.
The trigger sensed the N pole as cylinders 1,3 and the S pole as 2,4, bloody clever and as simple as it could be made.

The Haltech engine management syatem I have is exactly the same. S pole sets the system to "home" and fires channel 1, the N pole triggers channel 2.

The 3rd harmonic gives the best spread of power for a 2T, as it has a higher frequency but lower amplitude than the lower harmonics.
From messing about I have found that a length from the bellmouth correction to the 2/3 reed end length of around 135mm is good for a 125 running up past 12000
And another example being the RZ400 F3 engine the total length is 205 for tune at 10,000.

… a kappa-type thermocouple and it was just for data acquisition. In fact its position is much too close to the cylinder; there should be room for at least one cylinder volume of 125 cc in the header between cylinder and sensor to avoid fresh charge hitting the sensor. But mounting the sensor further down the pipe proved impractical because there it was quickly destroyed by vibrations.

Somebody asked about the Aprilia's inlet disk diameter. From memory I would say it was 126 mm.

Optimized disk inlets do not generate pulses: you open the disk when the crankcase pressure is equal to the pressure just outside the disk. Opening it any sooner would cause a loss of mixture to the outside world; opening it any later would be a waste of time*area.
You close the disk when the inlet flow has come to a stop. At that moment the pressure at the outside face of the disk will be equal to the pressure in the crankcase, but it will be higher than the atmospheric pressure, so there will be some blow-back, but that does not come out of the crankcase (assuming your closing timing is spot-on); it is just mixture feathering back from the high-density zone outside the disk. For that matter, every conventional inlet system (disk, piston, reed) will show the same blow-back tendency. And it may not be even visible from the outside; maybe the cloud of blow-back moves just a few centimeters and never really exits the inlet tract.
By the way, closing an inlet disk too early (or revving the engine higher than the inlet system's frequency would like to) will generate serious blow-back because then the closing disk interrupts an inward-bound flow which will violently bounce off the disk.
You can observe this very nicely on a dyno: looking into the carburetter you can see the fuel spray exiting the mixing tube and curving towards the crankcase. But rev it high enough and you will see this curving change into a steep front of mixture.

Frits has given a good explanation of the reasons for fuel stand off in a rotary valver. Its also a clue to more power too, because if the stand off is at max power rpm, then it points to the possibility of closing the inlet a little later.

[husaberg]

It looks a real good unit, what is it? where did you get it from?

To tell you the truth I am not 100% sure if it is a NSR125 or a NSR150.
2t institute acquired it on Yahoo Japan.
It was dropped off in Australia and ended up in Tauranga.
It's there for some corrective surgery to fix the machining errors Honda made when they assumed it was going to be a road bike.

Stuff below is inspirational only. But you will get the idea of thinking behind the choice of engine.

[Yow Ling]

Welcome to the old men with big dreams club.
Looks pretty flash, so many good things coming out of the closet, Im not saying hondas are gay, just saying

Will look great with the peanut tank and tassels after Kick trashes you with the GN

[kel]

Had you considered using something like this Below.
It needs a bit of work mind you the Crank pokes to far up and to far down as well, The piston seems a little er...big as well. Oh well it can be fixed i guess.

Did you win the new years lotto draw?

[husaberg]

Did you win the new years lotto draw?

Cheaper than a good second hand FXR150 Motor. Never seen one

Right now this below is a Four stroke tuner Yes a Four stoke tuner. Worse still a Harley tuner and a side valve one at that. Who using a methodic appraoch was able to beat the factory bikes with only a part time effort. Please read between the lines as it were, because it is his approach is what i was tring to highlight. (Note the highighting has moved it bit Whoops) Also note what he was able to achieve with one go at a 500cc OHV Goldstar. Imagine if he had a go at two strokes.

[Henk]

Cheaper than a good second hand FXR150 Motor. Never seen one

I have, complete with all electrics $600, about what it costs to rebuild one when the rod piston and a couple of valves are shot.

[husaberg]

Welcome to the old men with big dreams club.
Looks pretty flash, so many good things coming out of the closet, Im not saying hondas are gay, just saying

Will look great with the peanut tank and tassels after Kick trashes you with the GN

I never agreed to tassles. Maybe an airbrushed mural if it was tasteful or some flames on the sidecovers.
Plus I hear Kick would have to miss the Rangiora Bowls Club Champs if he is to race at Greymouth Sreet races 2012. This would be a big ask for Kick. He sure does love his Lawn Bowls you know.
Ps err.....don't you have a NSR as well. Not that they are a little Gay aye.
pps Vanessa is a chick. What is it you call your NSR is it Alan?
For Henk and Kel
Ps the Motor was less than a Good FXR and the total budget is less than one fifth of what one person has allegedly spent on his four stroke

[Henk]

For Henk and Kel
Ps the Motor was less than a Good FXR and the total budget is less than one fifth of what one person has allegedly spent on his four stroke

I can believe that, people have been rumored to spend stupid money on both four strokes and two. The reason I run diesels, even though I love two strokes, Is that I don't have the time or talent to develop five oil burners, and that is how many we have in the fleet at the moment. Someone commented to me a while back that I need to find a pit bitch, instead of being one. Fun to be busy though.

[2T Institute]

To tell you the truth I am not 100% sure if it is a NSR125 or a NSR150.
2t institute acquired it on Yahoo Japan.
It was dropped off in Austrailia and ended up in Tauranga.
It's there for some corrective surgery to fix the machining errors Honda made when they assumed it was going to be a road bike.

Most definatly a restricted NSR125 JDM. Are going to use a similar engine in a friends TAG 125cc Superkart. The early RS/NSR cylinders drop straight on. Having a blance shaft opens a world of opportunities.

[TZ350]

EngMod2T

I have been playing with the simulator to see what could be done with a ram tube on the inlet of the 3ex setup.



160mm ram tube vis 105 Tube. Looks like opening a hole or shortining the tube 55mm at the cross over point would give a usefull power boost.



3ex and 24mm pumper carb plus variable resonant inlet compaired to the 1ex setup (brown line) with the same carb open to the side without a header.

Previously the 3ex and 1ex delivered much the same curve and it was not untill I simulated a bigger carb did the 3ex deliver more power. Now with the header on the carb it looks like it will pass more air and deliver more power.

Who knows if the simulator is setup to handle resonant headers on the carb, but if it is, then this is very promising and points to the direction and dimensions of where to begin experimenting on the dyno with the inlet.

[Yow Ling]

Im sure this is way over 400hp/litre

Not sure of the STAs though