ESE's works engine tuner

[richban]

Are you kidding hole-shots is what the cvt will give you.

The cvt is a weapon off the line. We were up against 85cc cr powered race bikes. You would holeshot them from back on the 2nd row.
I know mount wellington track I used to race kt100s on there. The cvt anillate will the gearbox bike into the top corner and you will end up playing from then on in.

You have to remember that you tune the cvt for the power of your engine so it will do both haul out of corners as well as off the line.
You can hold your engine on its power peak the entire track and at any speed if you can make the corners.

Your sitting on the power peak the whole time. If you tune a cvt wrong its easy to hold it on it the down slope of the rising slope as well and make a 30hp engine go like a 5hp engine if that where your holding the revs.

It would go great on the long tracks you would just have to change the sprockets on the chain. But that would be the same for the geared bikes

http://www.youtube.com/watch?v=x3UpBKXMRto

You miss understand me. I said you could hole shot every race. I just don't like corning the things and the power delivery out of corners, in my experience was a little unpredictable depending on the speed you were cornering.

[richban]

Page 650....

[wax]

oh ok sorry.

The strange power delivery out of corners is caused partly by a slipping clutch. which is why the doctor pulleys are so good.
Also as frits said to weak a torsion spring and it holds it up in the gears. By putting the right spring in the back it down changes correctly and so its in the right gear all the time.

Also you need to keep it lubricated so it can change the gears correctly. The weak point in a cvt is if it gets sticky it will not change gear correctly. Anyone who has ridden a road scooter will know that when you ride along and then back off and then gas it again its slow to pickup like its in to high a gear. You can stop on the side of the road and then gas it again and it will downshift. There is ways to get around this lack of downshift and it makes them come alive.
A doctor pulley clutch will not release in the corners and will give you a positive lock this gets rid of the mushy cvt feeling.

[TZ350]

Starting from the beginning 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 and 640 have un edited collections of raw material.

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. 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....

Re EngMod2T question on ducts and entry areas.
Depends upon the geometry of the duct in the case and that of the cylinder where the duct begins at the bore edge.
In many designs the inner wall is very short ( above the gasket plane ), and the case extension of the duct outer wall drops away very sharply - with the floor being miles away from the gasket plane.
In this case I would use the area/length at an angle from the bore edge out to just below the gasket plane.
Some engines have a longer inner wall, and also have the case floor close to the gasket surface.
In this design the duct really does "go around the corner" into the case and the ( vertical ) window forms the entry area, as shown in the help files.
Truth be known the main effect is to change the case volume, but this spec is always MUCH better to model accurately by drilling a hole in a piston at TDC, and calculating with the ducts included.
The case volume total has a bigger effect on the real power produced by the sim, rather than duct length.
Duct length, has a bigger effect on the sim run times, not power.
I tried to replicate the run time error as you found TeeZee, and yes my system does the same - I never found that issue as I have never changed the zero figure before.
None of the pipes I have done have a "step", always an oval to round transition in the flange, that is modelled as a short taper in the pipe screen.
So yes, send a report to Neels, it is a "fault".
He is working now on creating a "button" that will collect all the files used by a project, into one file, so its easy to send each other sims to check, making it much quicker for others to review projects already created.

Re Ignitech starting issues, and base advance.
Post up a screen shot of the "Bike" page and advance curve, I may be able to help with that.

The backward angle of the port flank nearest the exhaust (the green line in your drawing) is important, but I agree that your duct is not a thing of beauty.
But the right-side duct, though it may look more attractive, is even worse. The backward angle of the green line may be somewhat exaggerated, but the blue line is not sufficiently angled backward, which will result in short-circuiting: fresh charge from the A-ports will make a U-turn and escape directly into the exhaust duct. And it will do so as soon as the transfer ports open, which means it will be too far down the exhaust pipe by the time the return pulse tries to shove escaped charge back into the cylinder.
I can only guess as to the purpose of such a design. Maybe it is not even a deliberate design but just the result of using existing casting cores for a new cylinder.
Or maybe the cylinder studs were in the way...

By the way, I appreciate you calling me Mr. Frits, but there is no need; just Frits will do fine .

Remember what I said about those simple calculations: they are only meant to help beginning tuners on their way and a lot of more or less important facors, like compression ratio, ignition timing, type of fuel, carburetter diameter, crankcase volume and angle*areas, are not taken into account.
In your example the important thing is that lower exhaust timings need bigger header diameters. But explaining why this is so, might be beyond the scope of this forum (and it would certainly be beyond the time I have at my disposal).
But come to think of it: the least I can do is post the same simple calculations here. Instead of all those factors I left out, I 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...

Here is a comb file for a very fast RS125, where the sim is all but perfectly reflecting reality.
The difference between the sim and RWHp is around 10 to 12% as you would expect - despite what many say about the fudge factors in a Dynojet.
The comb file has afr as measured on the dyno - and shows the correction of the ratio naturally going rich over the pipe, by the powerjet switching at 12200.
Without the powerjet it would go very rich, and would not make any power past 12600 - as in reality.
But for most sims, you will be in the ballpark simply running 12:1 in all fields.
The comb efficiency is good for full house racing 2T at 0.92,less well tuned engines will be down between 0.87 and 0.9
And the combustion variables are as calculated by the program using the turbulent model - you use burnrate prescribed until the model is well refined,then run turbulent ( very slow)
and transfer the results from that run manually,to speed up later sims by using real burnrate numbers.
Re the question of cylinder temp.The important factor is TUbMax - the temp of the end gases trapped in the squish.Optimum is around 1000*, but if its too high, the sim will automatically
show a warning on the screen - "deto" as the run is progressing.
Too lean, and or too much timing or compression and this warning comes up, believe it and change something to fix it, or your computers piston will sieze.
PS - I need your .pjt file to make it easy to open the sim.
Neels is working on a "pack and go" button that will collect all files for a project and put them in one file to send out for review.

Re the A and B port stagger.
Honda have always run the A port higher approx 0.7mm giving timings of 132/130/129.
This works OK using the big T port,but in the Aprilia 3 port layout, when pushed to the extreme as Jan did, the A port is lower to allow more area for the huge Aux ports needed to give sufficient blowdown.
Then the B port is raised to get back the needed transfer TA.

Re the ignition problems at starting.
Two things, firstly reverse the wires from the trigger and delete the reverse polarity button in software.Many times the trigger wired backwards gives very odd results when strobed.
Secondly, look at the "number of programmings" no way have you done 33,000 changes - this means the ECU is being corrupted by RF noise, you need to check the resistor plug cap and plug, as well as
ensure that the hot wire to the coil is well away from the trigger wires etc.
Also the curve is very odd.
Any tuned engine will like 28* advance in the mid under the pipe, then where the bmep starts to rise as the pipe works, around 8000 in your engine, you start pulling out timing, heading for around 15* at peak torque.
Depending upon how its set up, then less advance may be needed at peak power and beyond to make it rev out.
Below is a curve for similar rpm as your example.

Yeah, as a nightmare. Just think of any error you can come up with: Kreidler had it. Both disks were axially fixed on the crankshaft; they could not nestle against their covers and it took hours to press (!) them into a position that would not yield too much leakage or too much friction.
And take a look at the inlet tracts between carbs and disks. Nice tight U-turn, wouldn't you say? No, for my cylinder I thought up something completely different:
the 24/7-system. I've got no time to elaborate now, but you may find some more info here: http://www.pit-lane.biz/t117p376-gp1...es-aprilia-rsa .
The devil is old, Greg. Below left is a drawing I did when working on a Rotax cylinder in 1980, and next to it the 1980 cylinder itself and a recent Aprilia cylinder.
You are quite right: not that much difference in over 30 years.

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 yellow trace is the pressure at the exhaust port.

Wob am I reading this right?



On the left the pipe is sucking the cylinder down to late for the transfer port opening TPO.

And on the right the exhaust pulse is arriving back to early, before the transfer port has properly closed TPC.

Page 360

If the stator has trouble supplying enough power, quickly enough,you can increase the "turns before firing" to say 5 or 10.
This gives the system a chance to ramp up, before the ECU starts to fire sparks.

Re your sim printout TeeZee.
Lots to be seen there.
Starting at the top, you are about 500 rpm below peak power in the sim at 11500.
The whole engine isnt very efficient as the D.Ratio is low for the rpm being close to peak.
The TexAv is very high ,over 600
The TuMax is low.
With the depression in the cylinder starting early, then dropping away, the pipe shape is wrong for that rpm.
The pipe is too short for that rpm, as the return pulse has dropped away before the piston is close to closing.
The port timing and the pipe length are not working together, you have no superposition on the far left.
Look at this 40 odd crank Hp RGV100 just over peak, read all the numbers,and note the pressure wave shape, this is as good as it gets.

Edit - you can see the effects of low blowdown, if you get a big jump in Transfer pressure ratio when they open.

yes DR is delivery ratio.
TexAv = average temp in middle of the pipe.
TuMax = max temp of unburnt gas in the squish.
PexPort = pressure ratio at the exhaust port.

Go into help from the Post 2T screen,then plot options, then performance traces, also go to thermo traces for those terms.

Dont get hung up on Bl - STA, thinking its good to get rid of the transfer blip..
Any well developed race engine is ultimately Blowdown restricted, and you will always see the Tr Port pressure ratio rise when they open.
That effect is what makes port stagger work.
The first port to open, initially has backflow, it must, as there is more pressure above than below.
Then the rest of the ports open and eventually begin to flow into the cylinder due to the depression created by the pipe diffuser.
Thus the port that opens first, flows last.
Counter intuitive, but reality, proven on motored, instrumented engines in the lab and reported in a raft of SAE papers - and now shown in the sim.
Getting a balance between the blowdown needed to achieve the power you want, and the transfer area available is the tuning trick most valuable.

Superposition at ExPort opening is loosely referred to as pipe/port resonance, and is best achieved over the widest range with low Ex durations down at 192*.
Unfortunately this is countered by needing alot more blowdown than these numbers allow, and around 198 is needed to achieve the best bmep numbers.
In this scenario we try to achieve resonance at peak and beyond, to give plenty of overev power.

Next issue that is my favorite hobby horse for today is Ex duct exit area.
You will find a heap of free power, when using a T port or a Tripple port configuration, by limiting the duct exit area to around 75% of the Total Ex Port Effective.
Then make the header start at the area = to the Total Effective.
Join these with an oval to round adapter in the spigot or flange, where the width = the header dia all the way thru, to enhance the flow from the blowdown area,and
the height at the flange face forms an oval to give the correct 75% area.

The Temp Av in the pipe should be around 500 as in any fast engine you would measure around 600 in the header.
The TuMax should be around 1000,any more and you get deto, alot less and it means the temp/pressure rise in the chamber isnt high enough, and you are restricting the "push" on the piston.
But can also mean that you are using retarded timing to get heat into the pipe, not create pressure on the piston.

Lots more stuff, so little time.

As an addition to what Wobbly said about the exhaust duct-flange diameter, there is this quote from pitlane.biz:

Quote Originally Posted by Jan Thiel

One wants the pressure wave coming back into the cylinder but NOT the burned gases that are hot and can cause detonation!

and the photos of RSA's duct/flange

Page 364

Wow that RSA has some different bits attached? Frits is that a temp sensor in the exhaust header flange and if so was it connected to the engine management or just the data acquisition system?

Yes, it was 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.

Firstly you are misguided re the reed trace - this represents reed tip lift, there is no "pressure ratio" being shown.
The reeds will flat line at the max lift if you use a stop plate.
The length of about 135 for a 12,000 rpm engine has an effect over a much wider range, than the longer intakes, as the pulse frequency is greater, and the crossing point doesnt
move as much with a change in rpm.
That length is what was achieved in the dyno graph I posted back a bit for the TM125MX - just taking 15mm off the rubber gave 2 Hp in 50, and worked over a wide range.
It used a SPJ short carb from a HRC RS125, and a very short rubber off a earlyer model with the same bolt pattern.

Re the Ex duct nozzle.
The area at the cylinder duct exit should be around 75% of total Ex effective, simply change this in the Ex Port page.
Then you should have at least 30mm or so of "flange" to increase the dia up to the header size ( this would be an oval to round CNC transition).
Your small taper is way too steep, and kills energy in both directions.
This flange is part of the pipe, as you have done.
When done right this is the result - no nozzle = a 45mm duct exit straight into the header.
The curves above had a 39mm dia duct exit, with a 30mm long flange going up to 45 dia at the header.

Sorry if this is a stupid question... but do you want to have a step at the top and bottom where the flange/duct meet?? I imagined the CNC oval/round transition to be smooth but it looks like its not the case in the RSA photos above???

This seems like a key bit of tuning advice so i want to be 110% sure i get it. Ive mostly worked with MX motors and most have this 'step' top or bottom or both

Thats what ive been wondering... taking the quote earlier from Jan Thiel into account (about wanting the return pressure wave but not the returning gasses) I would guess that the step hinders the reverse flow of the burnt gasses , possibly by bouncing back a small wave back down the pipe as the reverse wave returns to the exhaust duct??

*** on second thoughts the 75% oval to 100% round transition will create a reverse wave just fine by itself (even without the step) as the initial wave returns though it.

A stepped transition at the header joint is common on fourstrokes for just the reason Jan Thiel stated.

If I remember correctly it will flow just like a cone section for outward gases. The step has no effect on the return wave activity but does resist returning "solid material".

The areas of a header transition is whats important - a 39 duct exit is 75% AREA of a 45 header,39 isnt 75% of 45 obviously.
The 75% isnt set in stone - just a guide.
I have noticed that the best ratio seems to be when you use the header area the same as the full Total Effective Area of the Ex Port, along with a duct exit restriction
nozzle about the area of the main port.

Re the smooth transition nozzle Vs a stepped design.I started to experiment with this after getting hold of a genuine A Kit Honda spigot.
I did a series of dyno tests using a late model HRC RS125, when beta testing Luytens cylinders.
The cylinder as first produced had a 40 by 35 duct exit oval.And as a reference any dummy that removes the oval and makes it simply 40 dia round, just lost 2 Hp and all the overev power.
This was first tested with a simple 40 dia round spigot, thus having a step - top and bottom.
Next I bolted on an early model A kit RS250 spigot, this is a cast oval to round transition from the factory.This test immediately gained around 1.2 Hp, and alot more power past peak.
Then I ground the duct out to 41, and welded the duct up inside as far as I could, to enable a 32 high oval shape.
Hondas later model RS250 A Kit has this size spigot but with the oval 35 high, so I welded that and reshaped it as well to 32 high.
A new pipe with the bigger header was built to suit.
This gained another 1.5 Hp, so as a last test I made a simple 41 round spigot - and this lost all the power just gained.
The 41 by 32 oval was right on 76%.

So - I can say definitively with a T port that the transition is better than a step, but all the 3 port engines I have done have made alot more power as well, though not as well tested back to back ( I was paid to do the T port testing ).

I believe that the Aprilias slightly different system can work just as well, maybe even slightly better - as im sure Jan Thiel would have tested it to death, as it promotes the flow from the triple ports right up to the header.
But when you are modifying an existing design, the CNC oval to round setup is quite easy to implement, on a T port or a triple port design, especially as I have tested it to death on 50cc up to 500cc cylinders,and given you the basic numbers to follow.

Edit - re the so called "power port" idea.This was developed as a tuning aid back when engines made no power at all, and running a bigger piston port timing, along with forcing inflow to be pushed thru the boost port, just happened to add a Hp or 2 on top of none to start with.
What we find now is that cylinder reed engines always end up being power limited by the effective STA that can be obtained by cutting holes in pistons, adding big Boyesen ports and even then adding floor ports.
All this is attempting to get the inflow around and or thru the piston that is in the way alot of the time.
That is why case reed is ultimately better when done properly.

Just a couple of things to note - the program will crash with an entry greater than 100 for duration - its not a "real" entry.
And your ignition timings are very wierd - never ever seen any 2T that will run 40* at any rpm.
But for example running straight Methanol in a 125, the dyno testing has been done a hundred times, and won dozens of titles.
Run 18.5:1 com ( 17.5 in air cooled ) and a "normal" ignition curve for petrol, ie around 28* in the mid and 15* at peak torque.This sort of setup gives the best power every time.
Its a long drawn out fallacy that you can make big power by taking a petrol based engine, pour in a high latent fuel, and simply wind in timing - it doesn't work.
Its best to run an "average" input for the variables until you are confident with the other inputs, then run turbulent,then transfer the calculated data.
These are 12 for AFR, 9 for delay,50 for Duration,6 for VibA, 1.25 for VibM.
This always works well as a baseline.

From what I've seen you can gain 20 HP right there if you can convince Rossi to shield his pipes from the boat's rooster tale. Talk about water-cooled exhausts....

Im sure you are right Frits, I saw the water spraying all over them in a video.
Then they tell me they only have 420* in the header.
They run absolutely mental compression ratios, then drown the engine with fuel, and use extra big stingers to stop it blowing up.
Even on jungle juice they make way less power than you guys were on unleaded, the pipe design is a joke.
Much to do.

The extra mid range power was all down to using ATAC chambers on the top two cylinders, as well as the original PV blades.

Page 370

The calculator in EngMod was added by Neels after I had done dozens of tests with tripple and T port designs.
The calculator simply uses 75% of the total effective port area as a guide.
This always works and always makes alot more power and generally I found that the duct exit should be about the area of the main port alone.
This usually ends up around 75% of the total ( by taking away the extra area of tripple ports) needed for lots of blowdown - thus power.
It was never intended to be used with a single port only as I havnt tested that at all, apart from years ago on TD3s etc, and we always went bigger back then, not smaller.
Theory says that having a smaller duct volume changes the Helmholtz frequency ( higher ) , and reduces the amount of exhaust residuals able to be stored in that duct ( meaning more clean mixture sits close) , but im not sure this theory will apply to making more power with a single port.
Having said that, a 40mm pipe entry on an engine only making 30 Hp is way too big, so reducing the duct and or header area, or maybe both, will very likely work real well.
Did you model the nozzle as a short tapered section ( 30mm say) from the duct exit up to the header dia ( as the first section of the pipe) and this is made as an oval to round transition in the flange on T port and tripple port designs.
Be real interesting to see if the sim reflects reality on a dyno, in your single port scenario TeeZee.

373

EngMod2T

I have been looking at exhaust port nozzels, now I would have thought the best arrangement was to have the exhaust port gently opening up starting at the port window and flaring out to the expansion chambers header diameter which is 40mm on my bike(old RS125 chamber).

But EngMod2T and Wobbly tell me that a nozzel shape is what I need for top end and over rev.



First step was to model the exhaust port then click on calc to find the predicted best nozzel diameter.



You can see that it is less than the effective diameter of the port exhaust port window itself.

I tried nozzel diameters from the diameter of the expansion chamber header at 40mm, 38-36 and 34mm. All other aspects of the model were the same, just the nozzel was changed.



A 34.5mm nozzel (green line) worked the best as the nozzel diameter increased top end and over rev dropped off.

The exhaust port outlet (nozzel) on my bike is currently 40mm, I guess I will be trying a 34.6mm one soon.

The calculator in EngMod was added by Neels after I had done dozens of tests with tripple and T port designs.
The calculator simply uses 75% of the total effective port area as a guide.
This always works and always makes alot more power and generally I found that the duct exit should be about the area of the main port alone.
This usually ends up around 75% of the total ( by taking away the extra area of tripple ports) needed for lots of blowdown - thus power.
It was never intended to be used with a single port only as I havnt tested that at all, apart from years ago on TD3s etc, and we always went bigger back then, not smaller.
Theory says that having a smaller duct volume changes the Helmholtz frequency ( higher ) , and reduces the amount of exhaust residuals able to be stored in that duct ( meaning more clean mixture sits close) , but im not sure this theory will apply to making more power with a single port.
Having said that, a 40mm pipe entry on an engine only making 30 Hp is way too big, so reducing the duct and or header area, or maybe both, will very likely work real well.
Did you model the nozzle as a short tapered section ( 30mm say) from the duct exit up to the header dia ( as the first section of the pipe) and this is made as an oval to round transition in the flange on T port and tripple port designs.
Be real interesting to see if the sim reflects reality on a dyno, in your single port scenario TeeZee.

Pinched that bit from the later RS example file that came with the simulator, I expect its a tail pipe venturie that controls the bleed down and that the rest of the tail pipe does not come into the equation.

The exhaust exit "nozzle" was used first by Helmut Fath ( my hero ) when tuning for Honda where their V twin 250 had one stinger 150 long the other 450 long.
I have tested all manner of variations and the best is around 10mm of parallel nozzle and then 10mm of divergence to a stinger around 1.5mm bigger.
This reduces the effect of the waves bouncing up and down the stinger off atmosphere disrupting the rear cone waves.

The pipe vol/engine cc field in the pipe screen was added by Neels to the program when Frits noted that he had calculated this for the RSA - maybe he can elaborate on the relationship.
Note also that there is two fields for the length to end of header and length to end of diffuser.
I got Neels to add this as so few pipe designs are "correct" and its a pain to calculate all the time.The header end should be 30 to 32% and the diffuser should be 64 to 68%

TeeZee - really glad that you are looking at the STA numbers and realising that the sim is telling you what is needed - or not in many cases.
Getting all the elements of a design in harmony is what makes big power numbers.
I would try making the divergent header nozzle longer - very short ones can create shock waves and reduce the energy available to do positive "work" in the pipe.

There is a relationship between how wide you make a port, and how gradually it should widen in order to keep the ring healthy.
With a good ring, 70% chordal of the bore is the optimum width. If you make it any wider, the widening has to be so gradual that you loose surface area at the top, where it counts most, because that's the area that opens first and stays open the longest.
The drawing below shows that with too wide a port you have to sacrifice the yellow areas at the top. But sacrificing those areas costs blowdown angle.area. That red port may have more open area, but not where it counts, at the top; the blue port is better.

Unless you keep the revs really low, a single exhaust port with a 70% chordal width does not give sufficient blowdown time.area, but because of the reason I explained above, making the port wider will be even worse. You will either have to use a bridge, add auxiliary exhaust ports, or raise the timing of the single port to well above the 190° that is optimal for pipe resonance.

The Aprilia cylinder is extreme in that respect: the middle exhaust port is 38 mm wide (older versions were 40 mm wide) and there are huge auxiliaries but even so the middle port is raised to 196° and then it gets a large radius at the top. The radius makes it difficult to measure the timing but if you shove a piston ring in the bore until you can just see light between the ring and the bore, you will find an exhaust timing of 202°. Don't try this at home, unless you want your engine to produce its maximum power at a mean piston speed of 23.6 m/s. But then your transfer time.area will probably be insufficient. And you know: if you raise the transfers, that will eat into the blowdown time.area.

Why does Aprilia use an exhaust timing that is too high for optimum resonance? It is a compromise: any lower, and the maximum torque will rise, but the reduced blowdown time.area will cause an early torque collapse and the product of torque times revs (yes, that's power) will be lower.

The Rotax 24/33 rear cone was dropped in Superkart racing when I discovered that a single 28* made more power on the dyno.
This led to the development of the so called Silverstone pipes that we made when I worked for JL when he was still in England.
These won dozens of World and Euro titles.
I have spent days of dyno time testing multi angle rear cones, and have always been able to achieve the same or better power with a single rear of the right angle.
In many cases the sim likes a sharp rear cone, but in reality its no better.
Seems to me that the main reasons you got better power with the modified pipe, was down to a gradual front nozzle, stinger nozzle, and a way shorter tuned length.

STA stands for Specific Time.Area. STA depends on rpm: the higher the revs, the shorter the ports are open per revolution. So I can only give you STA numbers if you specify for what rpm you wish to know them.
It's like this: a cylinder has port windows with a certain width and certain distances from the cylinder top plane to port roof and port floor. You can only express the window dimensions in millimeters and square millimeters (or in other funny length and area units that english-speaking folk still use).
Put this cylinder on an engine with a crankshaft with a certain stroke and a certain conrod length. Now you can also express the window dimensions in crankshaft degrees.

Now we can look at the angle.area concept (the point between angle and area indicates a multiplication; I make a point of writing it like this )
Let us assume a port window is 1 mm wide. Turn the crankshaft until the window is on the verge of opening. Its open area is still zero.
Then turn the crankshaft 1° further. Let's say the piston descends 0.5 mm, so the open window area is 0.5 mm height * 1 mm width = 0.5 mm² , and it has been open for 1°; that yields an angle.area of 1° times 0.5 mm² = 0.5 °mm².
Then turn the crankshaft 1° further again. That first 0.5 mm² open area has now been open during 2°; and as the piston has descended some more, there is now some additional open window area that has been open for 1°. Multiply all those pieces of open window area with the number of crankshaft degrees they have been open, all the way from initial port opening till port closing, and you get the total angle.area of the port.
But for gas flow it does not matter during how many crank degrees an area has been open; what matters is the number of seconds it has been open. That is where engine rpm comes into play: twice the revs means half the time; angle.area divided by rpm is time.area. And if you divide time.area by the cubic capacity of the cylinder that has to be filled (or emptied), you have specific time.area.
You may have noticed that in previous posts I sometimes talked about angle.area, and sometimes about time.area. And hopefully now you understand why. When I talk about an engine, I use angle.area. When I talk about a running engine, I use time.area.
O, TZ350, before I forget: here is what you have been asking for:

In the pic you posted, would that blue port make engine peakier, because of the sharper exhaust pulse?

In theory, maybe. But there are other, stronger effects. The sides of the wide red exhaust port are much closer to the A-transfers than is the case with the narrower blue port. That would provoke short-circuiting

EngMod2T



I was trying to explore the effect of various nozzels at the exhaust port, thay are all 34mm and vary in the exit angle and length.

They started at 5mm long out to 30 mm and the angles varied from 61-33-22 degree to 11 for the 30mm one.

Now I am not sure if the change in overall tuned length was making the difference or the angle of the nozzel but food for thought.

Hey TeeZee, I think what you are seeing is related to the fact that the sim cannot replicate the flow regime that an oval to round transition creates in the spigot.
The wide oval shape, that keeps this width right thru to the header start,really promotes the flow from the top of a T or the tripples in that setup.
But as I said at the start of your experiments I have not tested the relationships or area changes in a single port engine.
My feeling is that just maybe a single port would "like"a small volume duct,and then a step at the header - as your short transitions seem to help top end, at the expense of some area under the curve leading up to peak though.
I have asked Neels about the ideal way to model this as part of replicating a sliding header project I am working on ( as this has a step at the end of the header).
You cant have a "zero length" step within the pipe, so I have asked him what to do.
Will let you know the result.

Thanks, Mental; everything seems to be fine now. So here they are again:

http://www.kiwibiker.co.nz/manual/Aprilia-1.zip (6.8 MB)
http://www.kiwibiker.co.nz/manual/Aprilia-2.zip (8.3 MB)
http://www.kiwibiker.co.nz/manual/Aprilia-3.zip (9.2 MB)
http://www.kiwibiker.co.nz/manual/Aprilia-4.zip (7.2 MB)
http://www.kiwibiker.co.nz/manual/Aprilia-5.zip (5.6 MB)

Why put the plug inside the pin with a "new"" groove,there is already a groove available and also there is a chamfer on the end of the pin that can be used - as it was previously - to force outward, the retainer
into this groove.
Wont say any more as this stuff is Frits intellectual property , but with all the pics flying about its quickly becoming public property.
I made these plastic plugs several years ago using glass reinforced Peek,and tested them with no positive results at all.
But now we have tripple ports reaching around to 1/2 bore, and yes they do work a treat.

Re TuBMax, this is the temp of the unburnt end gases in the squish.
It is affected only by a few factors.The main ones being ignition advance and effective compression.
Effective com is composed of the static com as set by the cc in the head.Then you add dynamic com to this.
The dynamic com increases with charging efficiency ie more air/fuel in the cylinder per stroke - better trapping efficiency ie more air fuel kept in the cylinder per stroke, and lastly scavenging efficiency - less exhaust residuals left behind per stroke.

As you increase the last three mentioned, then the effective compression within the cylinder, as the piston approaches TDC, becomes greater, and more fuel is burnt - creating more pressure and heat, thus power.
Then you will reach a stage where the end gasses detonate, due to radicals forming,from excess heat and or uncontrolled pressure rise.
The only way to reduce this , is to drop the static com or reduce the ignition lead.
As you approach the theoretical limits of charging,trapping and scavenging efficiency,then you have to balance this with a static com and or ignition advance that will keep the piston alive.
This is exactly what happens on the dyno during development - its a juggling act to balance the com and advance to get the highest cylinder pressure you can, to release as much heat into the gas as is possible ,at the right time to suit the engine characteristics needed.
Com and advance put more of the finite fuel "energy" into the piston and cylinder and then eventually into the water - thus this energy is lost, and cannot be used in the external sense ie to heat up the pipe and generate
more overev .
But pushing the limits of all the factors ,in some form of synergy, is the black art we are only just beginning to be able to reliably juggle with in a good sim - without locking up a piston and a rod coming at you thru the screen.

Hope I never see that error on my screen - looks bad.

End of page 380

As I said in the previous post we need to address two important factors in a 2T engine design.
Torque and rpm
It all comes down to Hp = Tq*RPM/5252.
Keep the torque constant and increase rpm by 10% and you get 10% more power.
Hard part is holding up the torque at the higher rpm level.
A short stroke will allow greater safe rpm, but the bore area needed to create the angle area needed, is limited more and more as you increase the piston size at the expense of stroke length.
The piston gets heavier as well, so ultimately the engine may not physically be able to rev to anything like what the stroke may allow.
Yamaha tried for years to fight Honda with a 56 bore size.The 250s failed miserably from Haradas win in 93 all the way up to 2000 when Jaques won easily on the new square engine derived from the 500.
The 125s won in 74 then never again.The short stroke 500s were useless except for the Rainey years, where he rode the wheels off the thing and Kennys bench was real deep.
The bottom line to all this is that the square engine has the best compromises of rpm capability Vs useful bore area.
Go short stroke and though you may be able to rev it, the scavenging is compromised by the bore availability.
With long stroke - the reverse happens.
This all assumes we are talking max power capability - 250cc MX is all longer stroke now as this favours torque production from low rpms,and the extra rpm capability of a square engine isnt needed to create peak power numbers.

Wob, just looking at the hand drawn pipe in this list Frits posted (pijp 21) & looking at the stinger venturi; -it would tend to follow your rule of parallel section diffused out ~1.5mm larger, - the only thing I am confused about is the smallest diameter is ~23mm which is what I’d expect a conventional 125 stinger to be.

I thought the idea was to run a very short section at a smaller di than you’d run a conventional stinger mimicking the restriction of a longer pipe? So even though the drawing is exaggerated the diameter isn’t that small. I was expecting 21mm or something like that. Is it because the last baffle stage is steep? Or the requirement to get heat into the pipe can be produced by other means of ign & powerjet so stinger sizes have increased? It still seems odd. Or am I just wrong about the smaller than conventional size part?

The stinger config in pipe 21 is exactly what is needed for a 125 making anything like 50 Hp.
I have been using CNC nozzles I had made over 10 years ago that are 23.2 at the smallest section specifically for the pipes I have built for karts that make around 50.
For a 125 down at 40 Hp then 22 is about right, as is used by the CR125 engines in SKUSA stock class,down at 30 Hp I would say 20 or 21 ( never built one, sorry)
It all comes down to the amount of air that is dumped into the pipe, and this is totally reflected in the Hp numbers - empirically these sizes work every time to generate the correct back pressure, without causing deto or finicky tuning issues..

Which is why my pipe has a removeable end piece sandwiched between the end of the cone and the tailpipe. It is just a little piece of cone with a precise diameter nozzle. I tried one size then went up one and made more power on the dyno. Funny enough it felt better initially on the track with the smaller one.

Like below? Red is the exchangeable restrictor. Blue is its container, welded to the yellow endcone at the left. The yellow pipe at the right is the tailpipe (held in place by a spring) with a bigger diameter than the restrictor.

Not as fancy. Mine has no venturi and is made from .8mm sheet. The two sizes I have were formed very tightly around the required size rod, welded, and then hammered with a rubber mallet. The end result is a perfect fit with a nice smooth finish. I might look at doing one with the venturi.

Make your own from say .8mm sheet. If you cut it nice and straight on a guillotine it comes out very nice. I have a good selection of different size axles which I form it on. Once welded it typically jams on the axle but a bit of smashing it with a rubber mallet soon frees it up and leaves it looking good. I form a lot of stuff from .8mm sheet - exhaust mounting brackets, brake stay arms, engine mounts. I have a couple of lumps of steel for beating it over and getting it flat so it welds up nicely.

Kawasaki have had subs above the mains for along time - they have a PV in the subs , not the main port.
I did a 125 for karts a long time ago that won a National Title, but I dont think that the idea is specially better or trickshit.

NGK race plugs were originally designed to be about 1mm proud of the chamber,one reason there are no threads on the shell end.
This leads on to one reason that a toroidal chamber design works best.
I believe that plug position and indexing effects are reduced considerably by the quality of the CDI and the energy in the gap.
Using Ignitech and 0.2 Ohm primary Aprilia RS250 ( RGV) coils, I tested plug indexing and found no difference - but the fine wire R7376-10 plug made near on 2 Hp in 50 against a
Denso RS125 plug and a B10EGV.

TeeZee, use the new pack and go feature and send me your files - I will get bored over Xmas at the motherinlaws, and have a play on the laptop.

End of page 390



So far I have got to page 390 on this thread and accumulated 29 pages of posts relating to pipes.

[wobbly]

Yea sadly, I have said this before as well.
NoMates engine was designed well over 6 years ago to make 32 crank Hp, first run on Brets Dynojet it made 27.6 RWHp - thus fucking perfection, at the time, as far as I was concerned.
Then it went on to run superbly for 3 years, winning 3 bucket titles in the process, with no issues whatsoever.
The rider, doing no maintenance at all due to work pressures, then proceeded for another 3 years to detune and fuck with it, causing all manner of reliability issues in the process.
Its now been redone properly, with Ignitech, chrome bore etc.
The dyno , a newer 168 with full load control,now says it has a huge increase in mid power due to the servo PV , and it makes exactly the same power it did before, on a simple rolling road,as per ESEs test unit.
Meaning ,in reality, its way ahead of the previous baseline.
So, as the old piece of shit that still holds the lap record at Mt Welly is now a quantum leap better than before,bring on the CVT ideas.
You will need alot better than that trick shit technology,to beat NoMates in a head to head.
Really fast engine, maniac do or die rider.
But what do I know.
Jack shit, obviously.

[husaberg]

OK technical question Mike has about 30 hp from around 100cc so that's about 300 HP/Litre
Rob has about 30 HP from around 125cc so that's about 240HP/Litre

Rob is of course constrained by the air cooling rule Mike is not.(although i think he is currently only liquid cooling the head)

Rob is constrained by the 24mm carb rule. Mike unconstrained by any carb size rule and has i assume a 36mm carb

Does that mean. Often a larger carb than is actually necessary is used for the race engines?
Or is the additional 25cc of Rob's engine is drawing more airflow threw the carb to make up the difference.
Or does the more constricted airflow through the Reed valve nullify most of the gains compared to the less restrictive rotary valve.
Therefor the reed engine needs a larger carb?

Putting aside Robs clever use of the venturi a 24mm carb only has an area equivalent to 1/2 that of a 34mm carb............
Although i guess Mikes revs higher and Robs engine is bigger which may account for the difference.....

hoping someone will be able to answer.........

PS that 24mm carb rule seems to have be about exactly right............

[wax]

Is the carb open on the 100cc engines ??

[husaberg]

Is the carb open on the 100cc engines ??

Yes
Most of the newer builds are 36mm Keihins shorties with TPS and Solenoid PJ. 99ish kx125 and i guess others makes used them as well

or RGV downdrafts.

[Frits Overmars]

All I need to know is what to get that is legal for my class of racing, and where to go to get it. Speedpro suggests something Yamaha from Malaysia as he tells me there are plenty of tuning parts for road scooters and bikes that don't have the illegal words "Racing" or "For Competition use Only" printed on the packaging.

Don't forget to look beyond two-wheelers. There's a world of CVT goodies for snowmobiles.
I almost forgot: Wob, with a CVT you can omit the power jet. And the quickshifter. And the trombone pipe. And a load of sprockets. And the power valve .
(And even the variable ignition if you can get the CVT to keep the revs from dropping when the throttle is closed).

Teasing apart, it is my considered opinion that shiftboxes would have disappeared decades ago if the FIM hadn't blocked their development.

In the Beginning... No, there were no two-strokes in paradise (which makes me wonder why they called it paradise).
OK, some time after the Beginning riders had to manually adjust mixture strength. They had to manually adjust ignition advance (and re-adjust their contact breaker points every saturday).
They also had to fiddle about with hand- and foot-levers to constantly adjust the transmission ratio between a more or less fixed crankshaft speed and a variable riding speed. This fiddling was called gear shifting and the need for it lasted until well into the 21th century...

[SS90]

Don't forget to look beyond two-wheelers. There's a world of CVT goodies for snowmobiles.

OK, some time after the Beginning riders had to manually adjust mixture strength. They had to manually adjust ignition advance (and re-adjust their contact breaker points every saturday).
They also had to fiddle about with hand- and foot-levers to constantly adjust the transmission ratio between a more or less fixed crankshaft speed and a variable riding speed. This fiddling was called gear shifting and the need for it lasted until well into the 21th century...

I have several knowledgeable people make similar arguments Frits, but I have never seen this in action (snow mobiles seem to be the business that's for sure)

Is is practical and realistic to expect a CVT to be suitable for riders of all weights, I only see skinny buggers making use of the advantages, whereas geared bikes can quite often be competitive ( in the right hands) with a "portly" rider, it seems that from what I see, CVts are only suitable for ideal rider/bike combinations

[wax]

A cvt engine does not care about the weight on it. the power to weight will be down much like a geared bike. The cvt engine will still happily spin at the rpm you set it to. The only way it would change is if the cvt was incorrectly set and then the engine could load down as it was going up through the gearbox to fast. A lighter rider will not show up a poorly set up cvt as much as the load on it wil be less but the bike will still be slower than a lighter rider on a correctly setup cvt.

If you set up a cvt incorrectly so its reving below or after its power peak then yes a geared bike will be faster. But then if you run a gear higher than you should on a geared bike you will be slower as well. It comes down to setting it up correctly

[Frits Overmars]

Is is practical and realistic to expect a CVT to be suitable for riders of all weights, I only see skinny buggers making use of the advantages, whereas geared bikes can quite often be competitive ( in the right hands) with a "portly" rider, it seems that from what I see, CVts are only suitable for ideal rider/bike combinations

It may not be easy for you to swallow, but Wax is absolutely right.
If you see 'portly' riders beat skinny buggers, then there is something else playing a role as well. They have more power and/or better roadholding and/or they are simply better riders. All these things being equal, the heavy bloke doesn't stand a chance, gearbox or no gearbox.

[Brian d marge]

I would assume that acuallly fairly close to how the Japanese actually manufacture the frames after the intitial frame is built.
maybe sir Stephen (our Japanese based corespondent) can confirm this

the frames are not exactly cutting edge I m sorry , Aluminium frame have extruded sides then the are place ( I think ) one side at a time in a Jig before being welded to the head stock
MotoGp frames are hand made in a strict welding order to avoid distortion

tiss all I know

Stephen

[bucketracer]

Recently I tried a 30mm carb to see if it would make any more power than my 24, it didn't ...



30mm carbs curve (Blue line) ... the 24mm carb (Red line)

Rob is constrained by the 24mm carb rule. Putting aside Robs clever use of the venturi a 24mm carb only has an area equivalent to 1/2 that of a 34mm carb............

I know it doesn't answer your question, but when TeeZee tested his 24 against a 30 in a back to back test. The 30 didn't make anymore power than the 24 and so he thought that meant the 24 could do better yet as it must be something else holding the engine back.

[husaberg]

I know it doesn't answer your question, but when TeeZee tested his 24 against a 30 in a back to back test. The 30 didn't make anymore power than the 24 and so he thought that meant the 24 could do better yet as it must be something else holding the engine back.

Yeah i was surprised..... but then thought, well everything else on the engine was optimised for the 24mm carb anyway. I then assumed it was not really persevered with either. So how many runs and combination were actually tried?

I also guess it exceeded the max number of answerable questions.

But going back through some stuff it looks like some data Frits posted suggests the Rotary valve is worth about 4 HP over a similarly well developed crankcase reed with similar spec.(with a 125cc cylinder.)

So that could theoretically push an engine of TZ's spec down to 26ish HP (about 208 hp /litre) if it was a Reed instead Rotary valve (in outright HP anyway)
The same basic (possibly wrong) math would of course suggest that the 100cc reed valve engine might expect to gain about 3.2 hp to end up with 33.2 (or 332HP/litre)
if it was a rotary valve...........