ESE's works engine tuner

[wax]

Please let me know the offical rule on the engines.
125 aircooled
100cc water cooled
they are not allowed to be from a competition bike.
Do I have it close ??

[crazy man]

Please let me know the offical rule on the engines.
125 aircooled
100cc water cooled
they are not allowed to be from a competition bike.
Do I have it close ??

125 aircooled 24 mm carb and 150cc four stroke
and 100cc four stroke super charged or turbo

[wax]

125 aircooled 24 mm carb and 150cc four stroke
and 100cc four stroke super charged or turbo

ok 100cc water cooled no carb restriction
And no competition engines. But road bike engines ok
Single cylinder or are you allowed twins

[jasonu]

ok 100cc water cooled no carb restriction
And no competition engines. But road bike engines ok
Single cylinder or are you allowed twins

It is all in here somewhere.
http://www.mnz.co.nz/regulations/rules/general-rules

[TZ350]

Page 670 already, and I have not collated the links for 660 yet .... Ok got 660 done, now working on 670's

Recently I have been trying to find the posts that talk about pipes and collate and edit them. There is heaps of it and pages 620 630 640 650 and 660 have un edited collections of raw material. If your interested in expansion chambers they are worth a look. Pages 610 600 590 580 570 ..... 100 etc all have links lists to other stuff, then there is the Thread-Tools View-Thread-Images option that also helps to find the interesting pictures and posts.

25* down angle giving the best flow. This also reduces the duct area by the cosine of the exit angle, thus reducing the duct volume.

And this then also allows steps and transitions in the flange to promote the flow exiting the Aux Ex ports, helping blowdown efficiency. The main handbrake at the limits of power production.

The flow exiting into the duct, just as the piston cracks open the port, is dropping over a cliff - the piston face. This is why the down angle helps flow, it is " pointing " the exiting gases toward the duct centre, not keeping it attached, normal to the piston dome.

P450

Squish configuration is now set in stone, be it race gas or ULP.
As long as you have the tuning aids to overcome the natural effects.
50% SAR, combined with a vertical height that allows the piston to clip in the overev is the baseline.
This gives a VERY close optimum setup, be it domed or flat top piston, combined with a toroid chamber.

The domes like a bathtub ( confirmed by Frits ) and Yamaha factory bikes.
A flat top likes a re - entrant dropped plug shape, confirmed by HRC and me, many times.
Wide, close squish will always give great acceleration, but will restrict overev if you havnt got a digital ignition to pull out timing, and a solenoid powerjet to turn off the fuel past peak torque.
Without the tuning aids you have to juggle com,static timing and squish height, to get back the overev, if its needed for the application.

The solenoid Powerjet does lean off the BSFC curve BUT, what you need to get is that all it is doing is returning the fuelling to much closer to optimum. Its not really "leaning it out "as such,it is dumping more of the available heat energy in the fuel - into the pipe, speeding up the wave action and thus extending overev available.

You know when you get there, as I did with KT100 pipe design project I did years ago.
As soon as the pipe produces more than 18Hp at the crank, the cylinder and head cannot get rid of the heat produced, and it will fade badly after 3 laps - hitting the thermal limit wall. Needing fuel to cool it, not make power. Thus I worked for months locked in a dyno room in Flat Bush extending the band width, at the expense of peak power.

P461

ATAC as short a connecting tube as you can get, diameter about 1/2 the header, ATAC vol about the same as the cylinder swept vol. We had about 1/3 of the throttle plate hanging down in the header when it was open, in line with the flow direction.

By experiment you find the point where the resonating volume starts to kill power, and then go back a couple of hundred rpm, and snap it shut with a rpm driven solenoid. Easy with the Ignitech programmable output. There is NO advantage to ramping the closing point ie interconnecting it with the PowerValve is nowhere near as effective as a single point solenoid action.

You could get even better useable band width by having a double volume system, where another plate valve opened and shut the entrance to a second bottle vol. The two being open initially, then the second vol being shut off, creating a much smaller vol that was then shut of at a higher rpm.

But hey the simple thing works a treat on engines with no option for a PV.

forum: http://www.pit-lane.biz/t117p246-gp1...es-aprilia-rsa .
-------------------------------------------------------------------------------
Gordon Jennings certainly did a lot of good with his easy-to-read articles. But he created one misconception that is festering until this day, with his translation of the SAE-papers of Yamaha's Naitoh and Nomura into 'tuner's english'.
He extracted specific time*areas and claimed them to be the optimum values for a two-stroke. On the scavenging side he was as right as makes no difference, but on the exhaust side it was quite another story.
Naitoh and Nomura just stated their findings; Jennings concluded that specific exhaust time*area should be what Yamaha had been using. But Yamaha had by no means found a gasdynamic optimum; they just had gone as far as the quality of their piston rings allowed them to do. And had they thought of using auxiliary exhaust ducts (first seen in their present form in the 1971 Jamathi engine), they would have made a quantum leap.
Another point of criticism is that Jennings emphasised exhaust time*area and almost neglected blowdown time*area.
----------------------------------------------------------------

Nowadays an engine needs a large crankcase volume (the Aprilia RSA125's is 675 cc at TDC), all the port area you can cram into the cylinder circumference, good ducts for efficient flow and directional control, an exhaust that sucks and blows hard at the appropriate moments, and cooling, cooling, cooling.

p468

Re Blowdown STA numbers and the effect they have.
Firstly get out of your head completely the lawn mower engines view of the world that the piston dropping increases the pressure in the case, and it is this that forces the flow thru the transfers.
Mr Villiers creations may have operated this way - not any modern 2T.

When the transfers open, there is more pressure above the piston than there is case pressure in the transfer duct. This gives rise to the alarming notion that when using staggered ports, the one to open first has so much backflow that it takes ages to recover, thus it has inflow last.

The area available in the Ex from the time the port cracks, down to where the transfers open, sets the amount of combustion pressure that is lost down the duct, and thus the amount of positive pressure ratio across the open transfers ( and for how long this lasts ). We can have NO FLOW until that positive pressure ratio is reduced to the point where we have more case pressure than cylinder pressure.

There are two ways to do this - lift the case pressure and or lower the cylinder pressure. In a modern engine the case pressure is only rising very slowly due to the piston dropping, but what we do have is the pipe diffuser action, that started with the high pressure front ripping out the opening Ex port - then entering the expanding pipes front section.

As the piston approaches BDC the Ex port is starting to suck the chrome off the proverbial tow ball, dropping the cylinder pressure ratio dramatically, and it is this that forces the bulk flow into the cylinder.

If the blowdown is set correctly for the power needed within the rpm band we want, then the recovery time from the unavoidable transfer back flow at the opening point, is such that we get the correct amount of inflow to be trapped above the piston, thus creating the conditions for the correct amount of combustion pressure after the spark event.

It is this set of conditions - all revolving around the blowdown pressure, that ultimately creates how much combustion psi is developed - this creates torque, and it is this combined with rpm that creates POWER.

P472

The less clever a pipe design is, its much harder to pin down what the designers intent was, and the less it will be "port specific ".

But with say the 125 Bucket pipe, it was designed right from the get go to run with a 78* Ex port, and will only work correctly with the proper area step at the flange etc. As it has a two stage header and all manner of trickery to try and maintain the spread as well as create good peak numbers.

But there are all sorts of generalities that work, like 200* with 950 will peak at around 10500 with anything from a TZ350 to a Banshee Cheetah.

The RS125 with 196 and 830 will peak around 12000,then the A Kit with 200 and 800 will peak around 12500 but rev hard to 14,000.

But one thing that is a real fly in the ointment is the ignition - the peak prm point and the overev capability of a port timing/pipe length combination is hugely influenced by the timing and how much of the available heat energy in the fuel is dumped into the pipe, or the head/piston/water.

Best example is the Italian 125 ICC engines with fixed timing around 14*, these need a pipe some 40mm shorter than the A kit Honda to get revs near 14,000 with identical Ex timing.
The Honda has a digital ignition with a ton of retard and a solenoid powerjet, the ICC has none of this so needs a completely different approach - no free lunch.

Something to think about while the rest of the family occupy themselves with buying, boiling, painting, hiding, searching, finding and eating Easter eggs: a couple of recent videos from the Dutch 50 cc scene.
http://www.youtube.com/watch?v=mvV4x...feature=relmfu
http://youtu.be/0odVzSgufjk

p474

My experiences with these size exports are the following:

1. Never exceed 41mm for your bore (56mm)
2. Use at least 10mm radius for top corners
3. Use 100mm top edge radius
4. use 12mm radius for bottom corners
5. Use 80mm radius for bottom edge

Exceeding these gave more power but lead to the following:
1. Unexplained seizures
2. Broken rings after cooling off at the end of a race - runs fine and wins race, refuses to restart
3. Pinched rings - from severe hammering of piston top edge
4. Broken ring land at export
5. Ring breaks at low speed - not sure why but I think it just have more time to bulge into the export

If the only way to be competitive is to run such a port:
1. Piston and ring life is max 50km
2. Bore must be perfect
3. Very good (rounded) chamfer of top and bottom edge

I really like reading your ESE thread - gives me good feedback about where to improve my software and it is great to see such an enthusiastic bunch.

Regards
Neels

More news from Richard Maas. Did his trombone pipe give the desired results? O yes. At 10,000 rpm it gives 4 HP more than the same engine with a fixed pipe. It runs over 17,000 rpm without the need for a powerjet and with a fixed ignition timing. It is miles better than an engine with an exhaust power valve. And the mapping of pipe length, ignition timing and powerjet pulse width has yet to be carried out. Maybe the powerjet can disappear altogether.
Only problem so far: the piece of pipe that is fixed to the cylinder, is shrouded by the pipe that slides over it, so it gets very hot. Too hot for the Viton O-ring that is taking care of sealing. Any bright ideas, anyone?

P476

Running egt and cht you can watch both rise in unison as the rpm and power rise. As soon as deto starts the cht will shoot up, the egt will flat line or drop as radicals are formed in combustion. The best data logging gauge ( and the ONLY reliable egt probes ) are here.
http://www.exhaustgas.com/ProductDet...sketID=&RepID=

Get one of these with the extra wire to ground. When it sees deto it can ground an Ignitech input and retard the timing automatically. You get flashing lights and engine protection all in one shot, and cheap as chips - made in Czech so it likes being connected to an Ignitech - same lingo.. Works perfectly - when you get it trimmed correctly it will tell you where to manually pull out timing, then it just operates as a failsafe.

http://www.ebay.com/itm/Knock-gauge-...ht_1582wt_1297

A 74% port width should not cause any ring problems. If it does, it will be because of radii being too small. With good quality piston rings you can get away with 80% port width. But that will not do your power any good; such a width requires huge port radii that will take away much blowdown area at the top corners of the port as the picture below shows.
70% width is optimal in this respect. And like Neels says, pay attention to the bottom of the port window. Rings have more time to bulge into the port when the piston is on the way down. And you can apply large bottom radii because that will not take away any blowdown area.

p480

After looking at the trombone pipe I was wondering how the very long variable header fitted in with the requirements of keeping the header and diffuser within certain % limits of the pipes tuned length but combined with the slippery it might be possible.

There are several options in lengthening a pipe. You can move the end cone, like on the above drawing, or you can lengthen the header, like on the trombone pipe.
The gas pressure generates a force that is proportional to the cross section area of the moving part and proportional to the pressure difference at either side of that area. For a moving end cone this force can be up to 4 times larger than for a sliding header. That is one reason to go for the trombone system rather than the moving cone system.

The second reason: say you wish to lengthen the total length of the pipe by 10 %. If you do it by moving the end cone, you will also enlarge the pipe volume by a little over 10 %.
But in a good pipe configuration the header length is about 1/3 of total pipe length, so in the trombone system, lengthening the pipe by 10 % will result in lengthening the header by about 30 %. That gives a far greater variation in the pipe's Helmholtz frequency than a 10 % volume change.

It is true that the length percentages of all pipe components should be in a rather fixed relation to each other. Varying the lengths of all components by the same percentage would be the theoretical optimum, but that is not feasible.
Lengthening the belly will disturb the optimum relations, as will lengthening the header. So the pipe in its lengthened version will not be the optimum for the low resonance rpm dictated by the length. But it will be a hell of a lot better than using an exhaust power valve that spoils the 180° effective exhaust timing, necessary for true resonance.
And a pipe shortened beyond its optimum may not show the optimum length relations between its components either, but it will be a lot more effective in overrev than artificially raising the exhaust gas temperature by retarding the ignition, or by weakening the mixture strenght through closing a power jet, which has the disadvantage that not all inhaled air is used for combustion.

That Dutch trombone pipe moved from +70 mm length to -20 mm length, so its effect was concentrated on the lower revs (although raising max.rpm from 14,500 to over 17,000 rpm was a welcome bonus).

Do I understand this correctly, given sufficient blow down and exhaust STA an exhaust duration of 180 deg would be the optimum at any rpm?

The short answer is yes.

When the exhaust port opens, a pressure pulse starts moving through the exhaust pipe. It is reflected at the end cone and it should be back at the cylinder just before the exhaust port closes.
Next a part of this reflected pulse bounces off the partly-closed exhaust port and a residual pulse starts moving down the exhaust pipe.

This residual pulse too is reflected by the end cone and starts moving back to the cylinder. Ideally it will arrive at the exhaust port just when the port opens again. Then the cylinder pressure and the pressure of the residual pulse combine their energy and the resulting pulse will be stronger than the pulse from the previous cycle. And the combined pulse from the next cycle will be stronger still, and so on; we have achieved true resonance.

Some may argue that we want a low pressure in the exhaust pipe when the port opens because then the spent gases will experience less resistance while leaving the cylinder. But that is not true. Gas flow depends on a pressure difference ratio. But once that ratio reaches 2, the flow velocity will reach Mach 1, the speed of sound. Raising the pressure difference any further will not raise the flow velocity any further.

The cylinder pressure at exhaust opening can be as high as 7 bar and the pressure of the reflected pulse will be about 2 bar. Thus the pressure ratio is well above 2, so lowering the pressure in the exhaust duct outside the cylinder will not do any good to the flow.

What has the exhaust timing got to do with the 'true resonance' I mentioned above?
The initial pulse starts moving at Exhaust Opening and it has to be back at Exhaust Closing, or a little earlier. This pulse travels with the speed of sound and its journey up and down the exhaust pipe will take t seconds.

The residual pulse starts moving at Exhaust Closing and it has to be back at the next Exhaust Opening. This pulse also travels with the speed of sound and its journey up and down the exhaust pipe will also take t seconds.

So from EO to EC takes t seconds and from EC to EO also takes t seconds. In English: the exhaust port should be open just as long as it should be closed.
Assuming that the crankshaft rotates with a uniform speed, this means that the crank angle during which the exhaust is open must be equal to the crank angle during which the port is closed. So both angles must be 180°.

I developed this line of thought some 40 years ago, but when I first published it in 1978 (in the motorcycle magazine Moto73 of which I was the technical editor) everybody called me crazy. Some people still do, but I got used to it .

Above I made a couple of assumptions. The crankshaft does not rotate with a uniform speed, but at high revs the deviation is negligible. In case you really want to know, I did the math for the Aprilia RSA125. At a nominal rpm of 13,000 the minimum rotation speed is 12970 rpm @ 107° after TDC and the maximum value is 13031 rpm @ 356° aTDC. What's more significant: the deviation in crankshaft position from truly uniform rotation is always less than 1°. So that really is negligible.

Second assumption: both the initial pulse and the residual pulse move with the speed of sound. Not true: the pulse pressures in exhaust waves are so high that acoustics rules do not apply any more. We are dealing with gas dynamics here and the stronger a pulse, the faster it moves. Since the residual pulse is weaker than the initial pulse, they move at different speeds. But we will leave this aside for now.

Third assumption: the initial pulse starts moving as soon as the exhaust port starts opening. More or less true, but we are not interested in the first weak appearance of the pulse; we want to know when the pulse reaches its maximum amplitude. And that requires a certain amount of open exhaust port area. It turns out that for our desired theoretical exhaust timing of 180° we will need a geometrical exhaust timing of about 190°, depending on the shape of the port: does it open gradually or does it open over its full width all at once.

The obvious question will be: why has the Aprilia RSA125 a geometrical exhaust timing of about 200°? True, at 190° the maximum torque value would be higher, but the engine would not want to rev because the blowdown time.area would be too small.
The 200° are a compromise: a bit less torque and a bit more revs; as long as the torque decline is smaller than the rpm rise, we gain horsepower.

Up to p481

[Farmaken]

Merry Christmas TZ, thanks for sharing your wins and not quite wins on your way to developing your bike. See you next year ,cheers , Ken

[Frits Overmars]

100 cc watercooled, 125 cc aircooled, 150 cc fourstroke, 100cc fourstroke supercharged or turbo. But no competition engines.

Now that is a laugh. Even I could extract 40 HP from a blown 100 cc fourstroke. And a really dedicated foulstroketuner could make it 50. "But no competition engines" .

[husaberg]

Now that is a laugh. I will not demean myself to such activities, but even I could extract 40 HP from a blown 100 cc fourstroke. And a really dedicated foulstroketuner could make it 50.
"But no competition engines" .

Mr Frits have a look here.
http://www.kiwibiker.co.nz/forums/sh...nduction-100cc
http://www.kiwibiker.co.nz/forums/sh...have-a-real-go

[Bert]

Merry Christmas Rob and the ESE Team (and National and International contributors),
thanks for sharing all your evperiences and wisdoms, for all of us to think about and attempt to apply.

Please long may it continue.
Have a great day
Brent (and I'm sure; the rest of the GPR team).

[TZ350]

Merry Christmas TZ, thanks for sharing your wins and not quite wins

Merry Christmas Rob and the ESE Team (and National and International contributors), thanks for sharing all your evperiences and wisdoms, for all of us to think about and attempt to apply. Brent (and I'm sure; the rest of the GPR team).

Thanks guys, I very much like the positive people I meet here on KiwiBiker and at the Bucket race meetings.

May everyone have a Great Xmas doing the things they enjoy.

[2T Institute]

I have a KX80 engine in the shed and an RS125 chasis. Now lets see, the MX80 and 85 already have a bigger carb than I am currently allowed, they are water cooled, six speed close ratio and have well developed inlet, transfer and exhaust ports plus blowdown STA to spare so no need to modify the ports, all thats required is a little freshen up, and thats easily done by the shop, so all good there. And in keeping with the lazy spirit of not doing any of it ourselves we could pay someone like Wob to make the pipe. So with a little dosh and no nouse the possibilities are 30+rwhp with little effort.

The 85's are difficult to extract serious HP out of, have seen many 'claimed' 30HP at the wheel engines only to see them read 25-26HP(pretty peaky to) on a real dyno.

[FastFred]

Hi 2T I think TeeZee is all for outfits that people have built themselves and was trying to pull the punters leg. " with a little dosh and no nouse the possibilities are 30+rwhp with little effort." Speedpro is better at the sardonic windup.

Buckets is about building something yourself, there is the Hyosung Cup for those that need a stock class to ride in.

[TZ350]

I have been cleaning up inside the exhaust duct and un shrouding the side ex ports.



No matter how careful I tried to be tidying things up, the main Ex port which was at 73% crept out to 75%

There is a dark area over the Ex port, this implies the engine has crap scavenging and has alot of short circuiting. The A transfer rearward radial angle may be too steep, allowing direct looping into the EX when at BDC

Std A port angles were probably ok for a std pipe but with all the extra suck from the increased blow down and better pipe, the front of the A ports may need to be angled back some more. I will have to have a look at Frits Aprilia dwgs and some performance cylinders to see what angles they use.

[koba]

I've finally caught up with this thread again!
I feel compelled to share something at least slightly interesting and constructive.

I've been playing with TZ's old copy of MOTA over the last year and a bit.

It's been very interesting simulating engines and seeing how changes affect the end result.
The program is relatively simple and there seems to be a lot about an engines attributes that it doesn't take into account when compared to Engmod (and likely others) but it has nevertheless been helpful in gleaning a basic idea of how the fundamental engine attributes interact.

Bearing in mind I'm a compete novice and most of this is not backed up by real testing...
Some general trends I've noticed in the sim:

Reeds seem finicky, getting them right is quite hard but rewarding.

It seems very hard to have too much reed area (I suspect the down sides aren't being shown by the sim.

I have started simulating mine with a 28mm carb (It has a 28mm Mikuni flatslide from an RG150), I haven't been able to find more 'Simpower' with a 32.
(I have a 32 in the drawer but the real engine seems happier with the 28 as they are now)

Generally Speaking; more exhaust port area means more power.

I'm mindful that the pipe designs that the sim likes might be too 'sucky' for the transfers on my engine; I'm going to try a mild pipe and a wild pipe.

Better combustion efficiency is a really, really good thing to chase! (I've run most of mine at a base of 0.8 for doing comparisons between pipes and other changes.

Pipes. I can see how a factory team would try many pipe designs to squeeze out a better result!

Ignition, I must make a basic map of the 'curve' on the KX125 ignition I'm running.
It would be great to be able to change it but I'm going to have to work within that box for a while.

My engine is a port reed, MOTA doesn't really take this into consideration so I created a piston port model too with an eye towards working out the optimum timing, that was interesting as it gave similar power to the full reed sim when I got it refined, this worries me that I may still have the reed stuff wrong, I need to spend some time with the engine apart to look at this in more detail.

[TZ350]

Koba it looks like your doing quite well using MOTA for simulating the outcome of design changes.