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Thread: ESE's works engine tuner

  1. #29986
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    .
    There is a lot of gold to be found in this thread.

    To search for it use the good old Google "SITE:" search option which turned up this on Det Buttons: ......

    det button site:https://www.kiwibiker.co.nz/forums/showthread.php/86554-ESE-s-works-engine-tuner

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    Choose a likely looking option and check it out and you will probably find a quality post like the one below.

    Quote Originally Posted by husaberg View Post
    ... follow the posts for the RGV500 version and pictures

    .........
    .
    There are over 12,000 images attached to this thread and there is a lot of gold to be found there too.

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    To look through them use the "Thread Tools" option at the top of the page and then the "View Images" option.

    Then they can be sorted by:-

    "Posted Within" ........... I use from the "Beginning".
    "Images Per Page" ....... and I prefer 70 images per page.
    "Order Results" ............ and they can be in Descending or Ascending date order.

    When you see a picture that interests, you can click on it to view it or click on the "N/A" symbol below it to go through to the original Post.

    .............
    .
    Quote Originally Posted by TZ350 View Post
    Page 1000 has a lot of directory information pointing to the good stuff. Click on the Blue chevron in link above to go there.

    Quote Originally Posted by TZ350 View Post
    Page 1500 .... https://www.kiwibiker.co.nz/forums/s...post1130957586

    Page 1500 has a lot of new directory information on it.

    I have been trying to find the posts that talk about pipes and collate and edit them. There is heaps of it, mostly from Wobbly and pages 620 630 640 650 660 670 680 690 700 710 720 730 740 750 760 770 780 1040 and 1050 have un edited collections of raw material.
    Also page 500 about mid way down BucketRacer has a links list on:-
    How to build a 1978 30hp aircooled Suzuki GP125 https://www.kiwibiker.co.nz/forums/s...-tuner/page500

  2. #29987
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    Blowdown STA (Specific Time Area) is everything and determines the RPM ceiling and power output of your motor.

    Optimum Exhaust Port Duration for maximum symbiotic resonance is 190 deg but blowdown STA requirements may force you to use a longer exhaust duration.

    Wob often refers to the vital pipe dimensions and Frits posted a diagram of them. Stick to these %%% to get good results.

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    Frits suggested design criteria for a good pipe.

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    And Transfer Ports. Low and Wide is the go….

    Quote Originally Posted by Frits Overmars View Post
    Here are the RSA values.
    A-ports timing 130°, roof angle 25°
    B-ports timing 132°, roof angle 10°
    C-port timing 132°, roof angle 50°
    Quote Originally Posted by husaberg View Post
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    Transfer Port Theory
    Click on Husabergs link to read everything you might want to know about Frits's theory on transfer ports.

    Quote Originally Posted by Vannik View Post
    Turbulence is caused by the breakdown of the main flow. Because of the viscosity (in effect the internal friction of the fluid) the main flow progressively break down into ever smaller eddies and if left long enough all the main flow and all the eddies will stop.

    The main flow is from the transfer port loop and a stronger better directed flow with more kinetic energy can generate a lot of turbulence before it stops. If you have weak flow by the time combustion happens you need the extra flow from the squish to generate extra turbulence to get good combustion.

    On the other side if you have strong flow and thus good turbulence the extra turbulence can speed up the combustion too much and you loose power but mostly overrev. This explains why engines do not always behave the same to squish changes. Good engines use squish to minimize end gas to stop detonation while poor engines use squish to add turbulence.

    Turbulence cannot reverse, it is a one way street after creation. The bulk flow with the squish opening will loop slower and slower, both because of the increase in volume and because it keeps generating turbulence until it completely stops.
    Quote Originally Posted by Frits Overmars View Post
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    As an empirical rule Wobbly's 75% of the total exhaust port area works very well. But I prefer to base the port exit area calculation on the blowdown area, not on the total port area. The drawings shown below you will find the Aprilia's blowdown area (and the angle.areas for blowdown and scavenging).

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    I think the duct should just be able to handle the flow during the blowdown phase; any more cross section area in the duct only increases its volume which should be avoided.

    Wobbly hits on an important point: the higher the exhaust timing, the smaller the header diameter should be for a given rpm range. It would take me too far to explain the fundamentals here, but you can find the relationship in my 'simple exhaust concept' below.

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    Stinger nozzel
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    Quote Originally Posted by wobbly View Post
    As always I have to agree with Frits analysis - tying the duct geometry to the blowdown is way more accurate - as this number is crucial to achieving the power an engine will make in reality.

  3. #29988
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    Expanding on Wobs very practical idea of setting the duct nozzle area at the header at 75% of the "effective" exhaust port area for multi port and 90% for a single exhaust port and the distance to the nozzle from the exhaust window is 1.5 times the bore diameter.

    Effective port area is not blow down area but the total combined area of all the exhaust ports, main plus auxiliary's combined times the cosign of the ducts down angle, so just a little smaller than the total visible area of the exhaust port. The 75% for a multi port has been extensively tested but the 90% for a single port is not as well proven but still makes a good rule of thumb.

    And if you had good simulation software like EngMod2T then the target Mach number in the header nozzle and exhaust stinger nozzle is 0.8. More or less than 0.8 looses power and 0.8 is easy with a multi port but not easy to achieve with a single exhaust port.

    Quote Originally Posted by wobbly View Post
    It seems that in many engines going to around 0.8Mach at the exit seems to work best. As I have stated a hundred times that 75% of the effective port area at the oval duct face will get you close every time, as will the 90% area for a single port.
    Quote Originally Posted by wobbly View Post
    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 duration's down at 192*. Unfortunately this is countered by needing a lot 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 area. 90% for a single exhaust port.

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    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, a lot less and it means the temp/pressure rise in the chamber isn't 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.
    Quote Originally Posted by Forgi View Post
    I have been studying the work of the exhaust nozzle for a long time, so I'm very glad that Wobbly wrote about it in details.

    Wobbly!

    Is it possible that the cause of the '75% rule' is that after the opening of the exhaust port the positive pressure in the exhaust port/duct lasts until 55-60 degrees, and then the diffusor starts to work, so the suction will be determinative? This area of the exhaust port at 55-60 degrees is the same as the exhaust duct's area should be (cc 75%).

    If the presumption is right the exhaust port's lower edge doesn't have to be at ATDC 180 degrees, it would be enough at 135-145 degrees. In this case the proportion of the effective exhaust port area and the exhaust duct area would be 1:1. Of course the shape of the port is not the same and there is some important factors as well, but in general the abovementioned are right, aren't they?

    By the way what is your opinion, where the exhaust nozzle has to be, how far from the exhaust port?
    Quote Originally Posted by wobbly View Post
    The idea of reducing the duct volume was pushed along by Jan at Aprilia where they CNC cut the shape.

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    He lifted the floor, but more importantly the bottom corner radius was increased, this also reduced the volume, and helped reduce short circuiting from the A port.

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    With the cosine of the 25* down angle taken into consideration, I would guess the area at the port exit was quite small in the cylinder.

    I have found that the 75% rule works OK in a triple exhaust port cylinder, as does making the duct exit area the same as the main port area only ( often works out to be the same value ) but that the exit area must include the 1/2 moon cutouts, or be very oval shaped, depending upon 3 port or T port. Changing the volume affects the HelmHoltz frequency, as does changing the length.

    As it stands, the nozzle being part of the flange is all we can do with an existing cylinder. Welding up the last part of the duct works OK, but I always try and get as far up into the duct as I can to reduce the vertical height gradually, and widen it to get the Aux ducts to flow better.
    Page 1710 is worth a visit..... https://www.kiwibiker.co.nz/forums/s...tuner/page1710

    Quote Originally Posted by wobbly View Post
    The 75% number came about from doing alot of testing on flanges and duct shape for a customer building aftermarket RS125 cylinders. The best beta cylinder ended up with an oval at 41 by 32mm.

    It was about this time I started doing alot of sims using Neels code, and it struck me that so many engines went the best - on the screen and on the dyno with that 75% idea.

    Then I later confirmed that an oval to round transition within the spigot worked the best. I have not had a chance to try Jans idea of continuing the 1/2 moon cutouts down into the header, making that somewhat oval as well.

    All I do know is that dozens of customers and hundreds of others have used the 75% rule of thumb and it works every time - way better than the over 100% seen so often.. Some engines like more - some less. 75% seems to work every time ( TZ350 ) but some like even less if the port is VERY high, like big drag race Kawasaki triples etc.
    Quote Originally Posted by shnaggs View Post
    Wobbly, How close do you run your EGT probe to the port? I noticed on both the new KTM 125/250 MX bikes that I could not see EGT's over 1000*F. leaning it out didn't change much on the temp, but once I heard popping on over-rev, I then came back the other way. I did run the probe about 3" from the face of the pipe, so maybe I was too far away from the port face, making the readings a bit low?
    Quote Originally Posted by wobbly View Post
    There are a couple of things in play that affect the egt reading of a perfectly well running engine. If you look at the velocity and temp profiles as we have seen in CFD analysis of the Exhaust port/header you see that the temp varies dramatically with not only position along the duct, but also across its profile.

    I know that the very short probes as sold by some manufacturers for kart/bike use only intrude some 10 to 15mm into the header,and these read much lower than if the tip is on the center line.

    So I try to standardize on 3X bore down the header and in the middle,using exposed tip probes from EGT industries - the only type that have a guarantee, 2 years for the Stinger type.

    The exposed tip is way faster reacting and as long as the data sample rate is high enough ( above 10Hz ) you get to see what is actually happening in real time. Some gauges only update the screen readout every couple of seconds - useless.
    Quote Originally Posted by wobbly View Post
    If you can only get to 500* then there is a serious problem.

    It can only be a few issues that will cause this, way too much compression or timing for the fuel, or severe short circuiting.

    I had the short circuiting problem on a 250 MX engine that had the Aux ground around to bore center.It ran just fine but when the piston was changed from a Wossner to a Prox it ran like shit and would not respond to leaner jetting changes at all.

    Finally in desperation I pulled it down ,to discover that the Wossner had a machined hole in the skirt above the small end that did not go around past the centerline. The Prox had a huge cast in cutout,that was well past centerline and this was seriously joining the Aux and A transfer together as the piston passed over them.

    Changing the piston fixed the jetting issue immediately,where previously it would run rich ( 500* ) no matter what jet was in it.
    Any engine on petrol should be able to run past 600* in the header without any problems at all, no matter what the cc,rpm or bmep.
    Quote Originally Posted by karter444 View Post
    Hi Wobbly, when you say short circuiting do you mean exhaust gas entering the transfers or transfer outflow entering the exhaust duct .

    With regard to the piston cutout it seems most pistons have some form of cutout that will link the Aport to the aux exhausts , why is this cutout there and why do some pistons have such different size cutouts . as you mentioned a cr 250 wossner has a relatively small cutout while a kx 250 pro x has a large cutout , both would join the A port and aux ex to some extent ,so I imagine some joining of these ports is acceptable
    cheers Richard
    Quote Originally Posted by wobbly View Post
    If the Aux port is in front of the pin hole then no linking occurs,same with the skirt holes or pockets for weight reduction.
    When linking does occur there must be transfer mixture entering the Ex as the egt drops,and going leaner does not fix this.
    Quote Originally Posted by wobbly View Post
    I also cool the back of the spigot, with slots thru the casting into the water.
    The pic is an old version done by hand as a test - also shows the smaller exit now being used in red line.
    The extended Aux ducts have a huge effect on the Blowdown Cd, Jan said he saw this extra flow pattern right up the diffuser on an Aprilia pipe when it was cut open.

  4. #29989
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    Quote Originally Posted by jamathi View Post
    I discovered that making the underside of the transfer ports even with the piston in BDC
    was very important: considerably more power, less detonation and far better piston cooling.
    We started to have the exhaust ducts CNC machined in 1999 I think.
    But first we had to overcome the new fuel regulations in 1998
    102 octane had to be used instead of 130 octane.
    We expected BIG problems.....
    But within a couple of month's we had more power than before!
    The compression ratio was lowered from 19,5:1 to 16:1
    And the tailpipe restrictor was made 0,25mm bigger.

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    Then a very serious combustion chamber development was started.
    The result was that parallel squish was the best, with a squish height of 0,75mm
    Less squish height would give more torque but less revs.
    At 0,45 the piston touched the head....
    Then a head insert with a much wider squish band (50% of cylinder surface) was tried.
    And that proved to be the final touch.
    We now had more power than with the 130 octane fuels, and less problems.
    The sharp edge between combustion chamber and squish band proved to be very important.
    Even a small radius would give 0,5HP less..
    Quote Originally Posted by jamathi View Post
    Transfer ducts. Many transfer ducts with small differences were tried.

    We found more power by enlarging the A-port in the direction of the exhaust.
    Only the lower half, but it was important to give the A-duct an inclination away from the exhaust!

    The ducts were very conical, the smallest point being the port.
    In and outside walls of the ducts had a constant radius from top to bottom.
    The flow remained attached to the inside radius and so cooled the piston and eliminated detonation.

    Flow bench testing and the Jante type testing proved useless for power improvement.

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    Giving the rear side of the "yellow" B-duct an inclination versus the middle of the cylinder gave a big improvement
    Quote Originally Posted by jamathi View Post
    Pistons: We had cast and forged pistons.
    Cast pistons gave slightly more HP, but sometimes cracked.
    0,8mm piston rings gave more HP than 1mm rings.

    As the auxiliaries and transfers overlapped each other a certain power loss was caused by this.
    So closing the pin hole in the piston was tried.
    There were many solutions that were tested, but they all caused some trouble.

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    In the end the best, and most reliable, solution was welding then closed.
    This was very well done by PANKL in Austria, and never caused any trouble!
    Quote Originally Posted by jamathi View Post
    Quote Originally Posted by diesel62 View Post
    Do you mind me asking why do you think cast pistons made more hp than forged?
    Because forged pistons had a tendency to 'bend' their dome inwards.
    Quote Originally Posted by jamathi View Post
    When modifying a cylinder measuring duct sizes is not easy, especially in the curves!
    You can see our solution to this problem on the photo....
    Round 'sensors' fitted to a piece of welding rod!
    We had them from 7-7,25- 7,5 and so on until 28mm.

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    Behind the cylinder, in the wooden block.
    Quote Originally Posted by jamathi View Post
    Detonation. This started te be a problem when 50cc engines started giving more than 17HP, around 1975.
    At the time I thought this was a limit on engine power.
    Nikasil plated cylinders were very prone to detonation.
    Because of the rounded off edge at the top.
    At Minarelli/Garelli I solved this problem by sticking the cylinder head insert 3mm into the cylinder.
    A good solution, used for many years.
    But at Aprilia we found an even better solution: plate the first 5 mm around the bore at
    the top of the cylinder.
    Later this was machined to a very sharp corner, and this eliminated completely the unnecessary
    'dead room' at the top of the cylinder, it also gave 0,3HP more.....
    A little bit of still remaining detonation was eliminated by modifying the inner wall of the
    transfer ducts, cooling the piston.
    But part-throttle detonation remained a problem.....
    Which we never had on the dyno!
    On the photo you see a piston after a 54HP run...
    As long as you keep the throttle wide open a 2 stroke doesn't brake down!
    Quote Originally Posted by jamathi View Post
    The lower the water temperature was the more power there was!
    40° was the lowest we tried, each 5° more giving a power loss of about 0,4-0,5HP.
    On the dyno we normally used 50°
    The exhaust duct had to be cooled really well, especially the bridges in it.
    In the beginning we had some trouble with holed pistons, caused by auto-ignition.
    But bringing the water closer to the spark plug cured this completely!
    We also found out that the quicker the water circulated the better.
    An electric water pump was insufficient!!
    Quote Originally Posted by jamathi View Post
    At Aprilia we never had any high tech equipment, just an EGT sensor.
    Nothing else was needed for finding more power!
    And a very good Dyno to measure the results.

    Quote Originally Posted by jamathi View Post
    We tried various flat, and radius-ed pistons, but the original ROTAX dome always gave the best results.
    With flat pistons the flow detaches which gives less piston cooling.
    Quote Originally Posted by jamathi View Post
    Quote Originally Posted by jonny quest View Post
    Did you try the hybrid Yamaha style? Flat top with chamfered edge?
    Yes, of course....not better!
    Quote Originally Posted by jamathi View Post
    Mainly working on the crankcase.
    Improved water cooling passages, which were far too small
    And I really came to hate reed valves!!!!
    Being used to rotary valves that never gave any trouble......
    Quote Originally Posted by jamathi View Post
    We never had any trouble with the rotary valve!
    With the reed valve we had trouble every day....
    Quote Originally Posted by jamathi View Post
    Of course the reed valve is a big obstruction for inlet flow.....
    While a rotary valve is not!
    And when dyno testing the reeds keep breaking, costs you half of your time.....
    The rubber detaches itself from the reed case after some time.
    I really HATED it!!!!
    Quote Originally Posted by jamathi View Post
    Quote Originally Posted by breezy View Post
    Jan, how were you able to know when the flow was attaching or not to the transfer walls?
    By looking at the piston.

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    Quote Originally Posted by jamathi View Post
    Quote Originally Posted by peewee View Post
    Hi jan i was wondering if you saw any increase in revs when the rsa125 compression ratio dropped from 19.5 to 16:1 ? i have 19.5 also and worry it might hurt my revs
    Yes, we got 500 rpm more!
    Quote Originally Posted by jamathi View Post
    Sometimes riders complained about not being able to change gear.
    With their 'spark interruption' system.
    So I had a button fitted to my desk so that I could interrupt the ignition.
    At certain revs the engine kept running without a spark!!!
    The power did not change, and there was no detonation......
    Quote Originally Posted by jamathi View Post
    Yes, I think it was HCCI
    Auto-ignition by a too hot spark plug had quite a different effect!
    That always ended with a seized engine....
    HCCI caused no damage at all, the engine ran very well.
    It happened with max. power carburation, and around and above max power.
    I did very few experiments with it, which now I regret!
    The test without spark was only done to find out where the gear change problem came from....

    There was also part-throttle auto ignition which caused a lot of damage to piston and head!
    Incredibly strong detonation!
    Quote Originally Posted by TZ350 View Post
    Kel sent me this ......

    jan thiel on part throttle deto

    "I am 100% convinced our engine could have run for 6 hours at max power without seizing.
    The problems arise when you close the throttle, or run part throttle!
    The piston is mainly cooled by the transfer flow.
    And at part throttle there is less transfer flow, causing detonation (auto ignition)
    The entering fresh charge is ignited by the remaining, hot, burned gases!
    You can see very severe damage to the piston after maybe 10 seconds at 20% throttle.
    This still is an unresolved problem! I was thinking about a way to reduce engine power without closing the throttle. But how can you do this? I did not find a solution before I retired.
    And nobody else was really interested.
    At 100% throttle the engine was undestructible!
    By making the transfer ports as wide as possible we had very good piston cooling."

    No answer here but at least we are not alone with engines that fail on part throttle

    I scraped the full coversation below from here:- http://www.pit-lane.biz/t3173p60-gp1...vermars-part-2

    Brian Callahan
    Jan or others, how did you control the tuned pipe wall temperature (or EGT directly?) when testing on dyno? This seemed the most difficult thing to mimic when testing either the GP engines at QUB or my R/C boat engines, in the lab. The inertial dyno or computer controlled brake seem to work best because we can match the test engine's acceleration with reality. On steady-state testing, EGT would simply climb 500, 600, 700, 750 °C until way past reality and the piston would seize.

    Frits Overmars
    This has always been one of Jan's greatest handicaps. He has asked for an inertial test bench over and over, but Aprilias race director Witteveen, or The Great Leader as we call him, never deemed it necessary....

    Jan Thiel
    When EGT goes up and up there should be some serious problem with the engine.
    We never had pistons seize during our steady state tests.
    Working on the dyno continuously 5 days a week!
    I am 100% convinced our engine could have run for 6 hours at max power without seizing.
    The problems arise when you close the throttle, or run part throttle!
    The piston is mainly cooled by the transfer flow.
    And at part throttle there is less transfer flow, causing detonation (auto ignition)
    The entering fresh charge is ignited by the remaining, hot, burned gases!
    You can see very severe damage to the piston after maybe 10 seconds at 20% throttle.
    This still is an unresolved problem! I was thinking about a way to reduce engine power without closing the throttle. But how can you do this? I did not find a solution before I retired.
    And nobody else was really interested.
    At 100% throttle the engine was undestructible!
    By making the transfer ports as wide as possible we had very good piston cooling.

    As Frits has written, I would have liked to have also a dynamic testing possibility, with a flywheel.
    In my opinion you should simulate a straight, starting at around 10.000 rpm, and shift through the gears
    until you reach top speed. And with the airbox as used on the bike, with a ventilator that simulates the raising
    air speed as it would be on track! Maybe it is interesting to know that without a ventilator the engine gave
    less power with the airbox fitted.

    I was told that such a testing system was too expensive.
    And unnecessary as we won anyway!

    I can also see a disadvantage of 'dynamic' testing.
    Because the duration of the test is so short you can get away with very extreme (too extreme?) settings,
    without damage.

    GrahamB
    Remember that retarding the ignition is used at high rpm to increase exhaust temps and effectively shorten the pipe. So it's likely to increase the heating of the front edge of the piston...

    Haufen
    Yes I know, but part load egt is usually lower than full load egt. And I think most of us would prefer higher part load egt over part load detonation. Of course, how far one could go and how far one would need to go would have to be tested, and how much would be needed would depend on the engine.

    Mic
    How about much larger travel on the exhaust power valve.
    With a shorter exhaust port duration power is lower. And this is already controlled with the stepmotor over the ECU.

    Jan Thiel
    This causes detonation (auto ignition)
    The problem is that the burned gases do not exit the cilinder!
    Retarding ignition also does not make sense.
    As you have an AUTO-inition problem!
    So the engine does not 'listen' to its ECU anymore!
    What you would need is the same fresh gas flow, but with less HP!
    Not easy to achieve!
    A variable tailpipe might help.

    Jan Thiel
    Haufen, We also had such a test bench at Aprlia.
    The prototype of this test bench was developed by Apicom in collaboration wit Aprilia.
    So we had it first, and now anyone can buy it.
    It was helpful but not what I wanted.
    A so-called step test.
    And without the airbox!

    Frits Overmars
    Like Jan wrote, a shorter exhaust duration will worsen the detonation. What happens is this:
    During normal operation, the blowdown time.area of the exhaust ports is sufficient to drop the cylinder pressure below the crankcase pressure before the transfer ports open, even at high rpm.
    At part-throttle that cylinder pressure will drop to the same level, but now the crankcase pressure is much lower and exhaust gases will enter the transfer ducts, contaminating and heating the fresh mixture even before it enters the cylinder.
    A theoretical solution would be a power valve that enlarges the normal exhaust timing instead of lowering it. But that is impractical as it would ruin the shape of the exhaust duct and it would cause cooling problems in the cylinder's exhaust area.
    A variable tailpipe area, like Jan says, can be a more practical approach. I designed a simple solution, shown in the drawing below, but then two-stroke development at Aprilia was terminated because of Dorna's ban on two-strokes

    Howard Gifford
    Another way to lower HP without sacrificing piston cooling would be to richen the mixture when you want to lower the power. With a signal to a fuel enrichening solenoid you could achieve a power range. It would then be instantaneous and programmable. Not enviornmentally friendly but would work for racing. The mixture ratio difference from high power to low power would need to be just rich enough before a misfire and just lean enough for sustained high power.

    The variable tailpipe idea will work but I suspect the pipe temperature would drop off and it would take several seconds to regain full power. But then again rich mixture may have the same problem.
    Two strokes are like redheads. Hard to figure out and very temperamental. But when they are happy they are a lot of fun!
    HG

    Jan Thiel a écrit:
    The entering fresh charge is ignited by the remaining, hot, burned gases!
    You can see very severe damage to the piston after maybe 10 seconds at 20% throttle.
    This still is an unresolved problem! I was thinking about a way to reduce engine power without closing the throttle. But how can you do this? I did not find a solution before I retired.
    And nobody else was really interested.

    Institute of TwoStrokes
    On aftermarket ignitions I use there is a mode I can switch on where a number of indivdual sparks are cut, depending on throttle position. It is now only configured for cutting 1 in every 3 sparks on over run(tps <10% with high rpm). Would that sort of system solve the part throttle detonation? If the number of sparks cut could be varied along with TPS for this to begin and end? If it would be helpful I'm certain the manufacturer would only need a software change to do this.

    Jan Thiel
    I certainly thought about cutting sparks.
    But remember: the problem was AUTO-ignition!

    GrahamB a écrit:
    Remember that retarding the ignition is used at high rpm to increase exhaust temps and effectively shorten the pipe. So it's likely to increase the heating of the front edge of the piston...

    Jan Thiel
    Indeed, retarding too much caused detonation!

    Institute of TwoStrokes a écrit:
    Jan Thiel a écrit: The entering fresh charge is ignited by the remaining, hot, burned gases! You can see very severe damage to the piston after maybe 10 seconds at 20% throttle.
    This still is an unresolved problem! I was thinking about a way to reduce engine power without closing the throttle. But how can you do this? On aftermarket ignitions I use there is a mode I can switch on where a number of individual sparks are cut, depending on throttle position. Would that sort of system solve the part throttle detonation?

    Frits Overmars
    As Jan pointed out, once you have auto-ignition, the engine does not listen to its ECU any more. So you would have to start skipping sparks well before the onset of detonation.
    In a foul-stroke your proposed system does work, but a two-stroke would react far from linear. For example, if you skip 1 in 4 sparks, you will loose much more than 25% of engine power because that one missing spark will cause the gasdynamics processes to collapse. The main problem would be to realise a smooth transition from intermittent to full ignition.


    Jan Thiel a écrit:
    Retarding ignition also does not make sense.
    As you have an AUTO-inition problem!
    So the engine does not 'listen' to its ECU anymore!
    What you would need is the same fresh gas flow, but with less HP!
    Not easy to achieve!
    A variable tailpipe might help.

    Haufen
    I think I expressed myself unclearly. What I meant was the following:
    Imagine your engine with the throttle opened just above the auto-ignition range. Then you have sufficient transfer flow, but too much power. To lower the power, now retard the ignition. Then you still have sufficient transfer flow, but with less power.

    I think Honda used auto-ignition to their advantage on two-strokes. As far as I remember they did it with a (very) variable exhaust power valve.

    Frits Overmars a écrit:

    Mic a écrit:
    How about much larger travel on the exhaust power valve. With a shorter exhaust port duration power is lower. And this is already controlled with the stepmotor over the ECU.

    Frits Overmars a écrit:
    Like Jan wrote, a shorter exhaust duration will worsen the detonation. What happens is this:
    During normal operation, the blowdown time.area of the exhaust ports is sufficient to drop the cylinder pressure below the crankcase pressure before the transfer ports open, even at high rpm.
    At part-throttle that cylinder pressure will drop to the same level, but now the crankcase pressure is much lower and exhaust gases will enter the transfer ducts, contaminating and heating the fresh mixture even before it enters the cylinder.
    A theoretical solution would be a power valve that enlarges the normal exhaust timing instead of lowering it. But that is impractical as it would ruin the shape of the exhaust duct and it would cause cooling problems in the cylinder's exhaust area.
    A variable tailpipe area, like Jan says, can be a more practical approach. I designed a simple solution, shown in the drawing below.

    Click image for larger version. 

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    Haufen
    I think I have not gotten behind the variable tailpipe idea, yet. What would you like to vary with it and to achieve which effects? At little throttle openings the pressure inside the exhaust pipe is already very close to atmospheric pressure (if not even) on most engines. And if you had say 100mbar inside the pipe at the critical throttle opening, then the engine might have had more power with a bigger tailpipe.

    Frits Overmars
    'Opening' the end of the reflector will cause a substantial weakening of the reflected pulse and thus less charging of the cylinder. Izze simple, no?

    Haufen a écrit:
    Variable transfer timing would be nice also, if feasible.

    Frits Overmars
    That would be my ideal. Lowering all the transfer roofs would shorten the transfer timing and lengthen the blowdown timing, so the cylinder pressure would drop further before the transfers would open. It would cure the hig revs/low power-detonation and it would improve the power band because a too early-returning exhaust pulse would have less opportunity to push the fresh cylinder contents back into the crankcase.
    A controllable transfer height would even make a throttle valve unnecessary.
    There's only the little problem of how to build it...

    Jan Thiel
    Haufen, Auto-ignition usually occurs between 10 to 40% throttle at high revs.
    In fast, non full throttle corners.

    Retarding the ignition was tried to diminish power.
    This makes the exhaust very hot.
    Then, when you need full power, it is not there because the exhaust temperatures are wrong.
    This takes a little time, when the engine is back to full power you are already at the end of the straight!
    The same goes for water injection in the exhaust.
    It was tried by Rotax about 25 years ago.
    There was a LOT more power at low revs, so the rider had to take it easy when opening the throttle.
    But the engine revved a little bit less, because the exhaust temperature did not recover at high revs.
    And lap times became actually slower.
    After a day of testing the system was switched off.
    Lap times immediately improved!

    A very important thing when accelerating is the power you have after changing gear.
    Spark interruption may be not so good for this!
    As I did not have the dyno I wanted this gearchange effect could not be tried on the dyno, very regrettably!
    Retarding the ignition and weakening the mixture by powerjet can also have a negative effect on this.
    The exhaust temperature should be 'Right' for the No. of revs after you change gear.
    If the temperature is too high there will be less power!

    So it is REALLY complicated!
    Part throttle deto.

  5. #29990
    Join Date
    18th May 2007 - 20:23
    Bike
    RG50 and 76 Suzuki GP125 Buckets
    Location
    Auckland
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    .

    Follow the link to read the whole story about Team ESE's GP/NSR110cc engine build. You will have to follow the links to see the whole post, pictures and related links.
    Quote Originally Posted by TZ350 View Post
    Page 1680 ...... https://www.kiwibiker.co.nz/forums/s...tuner/page1680

    This is Team ESE's formula for a reliable 110cc water cooled Bucket racing Engine.

    It's very simple, NSR cylinder, de stroke crank, long rod, to give enough room for a thick spacer plate to marry the NSR cylinder to the GP100 crankcase, can't get any easier than that.
    Quote Originally Posted by TZ350 View Post
    Attachment 333324

    Building another Suzuki GP100 NSR 110 hybrid using a re plated but standard NSR250 cylinder.

    Stroke 48mm Bore 54mm for 110cc ... (an NSR is 54 x 54).
    Inlet opens 140 BTDC closes 80 ATDC
    Exhaust opens 80 ATDC
    Transfers open 114 ATDC

    The shorter stroke gives me a very useful increase in blow down time area without having to do any porting at all.
    Quote Originally Posted by TZ350 View Post
    Attachment 329021.... https://www.kiwibiker.co.nz/forums/s...tuner/page1681

    How to make a decent light weight racing 12 Volt generator stator for the Suzuki GP/TF/TS RG50 from a Lifan after market magneto kit. We have spun these to 14,000 rpm plus on the dyno and they have proved reliable on the track.

    The Lifan back plate and modified flywheel fits perfectly into the Suzuki GP/TF/TS and RG50 cases.

    Attachment 329025

    Basically the conversion involves transferring the center from a Suzuki flywheel to the Lifan.

    Attachment 329023 ... Attachment 329024

    Chambers starts by spinning the heads of the rivets off of the Suzuki flywheel. He then punches out the rivets of the Suzuki fly wheel to free the Suzuki's center boss.

    He then bores the Lifan boss out to suit the Suzuki boss, a close fit is required here, basically size for size, with minimal clearance. And then he spins the heads of the rivets off the Lifan flywheel.

    The next move is to orientate the Suzuki boss and Lifan flywheel so that there is an appropriate gap between the heal of the trigger tooth and trigger coil at TDC, usually 20 deg.

    Attachment 329026 ... Attachment 329022

    The last move is to secure the Suzuki boss to the remains of the original Lifan boss left inside the Lifan flywheel. Chambers drills and taps through the Lifan flywheel and the remains of the original Lifan hub and rivet's. If a rivet turns, he gives it a little touch with the TIG, just a small tack weld is all that is needed to hold a loose rivet while it is drilled and tapped.

    We cut the two Lifan high Voltage winding's off and re wind the three empty stater polls for extra 12 Volt current capacity. Although you can get away with using just the three original 12 Volt coils for powering an Ignitec but if you want a water pump too then you need to rewind the empty three polls.

    Use a Lifan voltage rectifier/regulator and a 36V 2200uF capacitor for powering an Ignitec CDI ignition. If you do try winding on extra coils remember they are wound in alternating directions, ie; the first clockwise the second anti clockwise, the clockwise again and so on around the stater.

    We use the Lifan stater assembly to power our Ignitec ignitions. We have not tried it but you may get away with using the complete Lifan racing ignition package and CDI. The Lifan CDI is probably better for engines that don't rev much past 10k or so.

    Quote Originally Posted by TZ350 View Post
    Attachment 328247

    The Bad news .... a broken tooth which showed the classic signs of a fatigue crack ending in a fracture.

    The Good news is that there is plenty of oil getting to the gears. No sign of damage that could be attributed to a lack of lubrication.


    Attachment 328246Attachment 328245

    Case spacer and extra wide spacing between crank halves for a bit of extra crankcase volume.

    Attachment 328244

    Gearbox oiler tube and KE175 rotary valve cover.

    Attachment 328248

    NSR cylinder showing one of the fuel injector ports and rotary valve inner. Not much room left between the RV and gearbox input shaft.

    The good thing about having to pull the motor down is that I am now very comfortable with gearbox oil feed of about 1L min from those small pumps is well and truly sufficient.
    Quote Originally Posted by TZ350 View Post
    Dr Evil does it, a F4 class legal water cooled 110cc engine.

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    Finally, after several weeks of detailed finishing work Mr Bigglesworth's Frankenstein engine is ready.

    Possibly the worlds first ever 1979 learner/commuter Suzuki GP100 engine fitted with EFI, digital ignition, a dry sump six speed gear box conversion, an oversize KE 175 rotary valve, a servo power valve and water cooling.

    Attachment 324039

    All that remains is to fit it into the frame. Being 12mm wider than the original five speed air cooled unit and needing a radiator, pump and associated plumbing, it is not a straight swap but hopefully I will get it all done this week.
    Quote Originally Posted by TZ350 View Post
    Attachment 323698

    Making progress with the six speed Suzuki GP110cc engine. Spent my evenings after work for the last couple of weeks test assembling everything to make sure that they fit and the clearances are correct. Lots and lots of detail work has been required to get things right.

    Attachment 323702

    Micro polished gear-set courtesy of Morgan Engineering.

    Attachment 323700Attachment 323701

    Lots of port area. Exhaust opens 80 atdc transfers open 114-116-117 atdc and inlet opens 145 btdc and closes 80 atdc. No porting work has been done on the cylinder at all. The port timing has been obtained by adjusting the cylinder up and down with a spacer plate and shims until I got the timing that EngMod suggests as being optimal.

    Between the variable timing of the exhaust port power valve and a pressure reducing valve in the expansion chamber I hope to get a wide spread of useful power.

    The inlet tract is a nominal 30mm with a short 24mm venture restriction at the engine end of the carb to satisfy class regulations. From previous experience, I am not expecting the venture restriction to have much real effect on power output.

    Attachment 323699

    Major crankcase volume, it will be interesting to see how that goes. Slow speed injector port on the right hand side. The injector port is angled so the injection stream fires directly into the face of the incoming inlet air stream. The timing of the injection squirt can be adjusted in the EFI software for best effect.

    Attachment 323703

    The top of the cylinder was skimmed 2mm and the head insert also protrudes into the cylinder 2mm. The insert itself is a blank that can be machined to what ever combustion chamber you like.

    The beauty of reducing the stroke on a 2T motor is that even without any porting on the cylinder, the exhaust blowdown time area is automatically increased.

    I was unsure about the legality of using a VHM head but no where on the paperwork does VHM call it a racing part. It is clearly labeled as being for a NSR250 which is a class legal non competition engine.
    Quote Originally Posted by goose8 View Post
    It is a over size rule so the motor would have to start out as a 100cc or 150cc ?, just building a 110cc or a 158cc is against the rules is it not? I have wondered about the fxrs as many seem to build them out to the oversize limit straight off the bat , not as a need to do so after a blow up which I would consider to be outside the rules . After talking to a couple of people at the track yesterday ,they had similar feelings any thoughts on this.
    Quote Originally Posted by TZ350 View Post
    I agree building an engine to max oversize straight off is a grey area that probably needs addressing along with other issues like, what size is a 24mm carb and how much of an engine can be homemade before it is no longer based on a non competition engine. We have had a pretty common sense approach to this until now and I understand some of the AMCC Bucket committee members are looking at how a re write of the rules could address some of these grey areas.

    Just for the record, when this extra oversize rule was mooted for the convenience of a limited few MB100 pilots I made a submission to MNZ opposing it. Now that it is here and available to all, I am going to enjoy it.

    Attachment 319215 Suzuki GP100 bottom end with rebored (replated) NSR cylinder.

    I expected a bit of opposition. So I was careful to start with a 100cc engine. A air cooled Suzuki GP100 that I had previously raced and after adding an old water cooled NSR cylinder and porting it, the cylinder was rebored (replated in this case) because it needed it.

    Old dud cylinders are cheap to buy. So it is a totally legal within the rules and the spirit and the intent of Bucketracing endeavor. Which started of as a 100 and finished up as a re bored 110, my arse is totaly coverd rule wise.

    The only difference between what others have done and what I am doing is approach, different approach same result, a water cooled F4 2T100
    Quote Originally Posted by TZ350 View Post
    Attachment 317507

    Old air cooled Suzuki GP100 soon to be a 30+hp water cooled 110cc six speed Suzuki GP-NSR Frankenstein engine.

    Another step forward, the cylinder to crankcase adapter/spacer plate.

    Attachment 317506

    I picked up all the finished machining for the crankcases yesterday. There is still a lot of hand work too be done on things like cutting in the transfer ports and inlet tract but now I have everything to start finishing it off and putting it together.

    Attachment 317508

    The engine is going to run a dry sump for the primary gears and clutch. The wet clutch plates are going to be lubricated by pumping oil up the center of the gearbox input shaft to the inside of the clutch hub. Where it will get centrifuged out through holes in the inner hub to lubricate the clutch plates. After that it will drain back into the sump leaving the clutch assembly free to rotate in air instead of churning around in a bath of power robbing oil.

    For a pump I am going to use a diaphragm fuel pump. I had thought of running the gear cluster dry sump as well but just did not have the courage to rely on getting the oil spray right for lubricating the gears, maybe next time.

    At the GP, someone in the know told me there are those planning to get the 110 rule thing that was 105, now 110 changed back to 107. That will work for the shorter stroke MB100 boys who got the rule changed in the first place so they could run the cheap over sized KT100 pistons but it would disadvantage all the other 100cc makes like Kawasaki and Suzuki who then couldn't. To be fair, a rule change to make the KT100 piston available without de stroking the crankshaft needs to make the advantage available to everybody in that class. And that means 110cc max oversize for F4 100cc 2T's if you wan't to share the love around with the cheaper over sized pistons.

    In the end it does not really matter to me what cc rule change advantage they try to give themselves. If it disadvantages my current build, I will just make another crankshaft with a stroke to suit.

    Currently I have been working with old cylinders that need re plating to meet the re bored part of the rule. On any cylinder shortening the stroke increases the blow down STA without any porting required. So if I have to shorten the stroke anymore to stay within any new tricky dicky rule change I will be able to enjoy the advantage of the correct amount of blow down and not having to port and re plate the cylinder. Basically I will be getting the same power/rpm for the effort of a crank build, as much power as before for less effort, a win win in my book. I just wish I had figured that before I started the 110cc version.

    Attachment 317511

    Oooo look another crankshaft could this be a 106cc version, I have been thinking ahead and now have 115cc 110cc and 106cc crankshafts for the GP/NSR hybrid and could easily build a 100cc version if I had too. A 125cc version would be difficult because of limited space in the crankcase.

    The only rule change that would really effect Team ESE would be banning the spirit of Bucket racing and limiting cleverness. There is the Hyosung standard production cup, class, or whatever it is, for those who want to take the easy path and not have to make any real effort to develop a reliable front running engine. That sort of racing is as interesting as Bat shit in my opinion.

    The history of Racing is littered with good ideas that have effectively been banned because others have been to lazy or technically challenged to keep up. In Buckets, part of winning is building something special, and in this class I think attempts to limit that are wrong.
    Quote Originally Posted by TZ350 View Post
    The Dry Sump and Gear Oiler, not to sure how well this idea will work so I am going to try it on the old air cooled engine first.

    Attachment 317734 Attachment 317736

    The oil spray bar. The oil level in the crankcase will be minimal and well below the gears and clutch hub. The bulk of the oil will be held in a sump tank.

    The oiler drops oil onto the gear pairs, I sure hope the oil mist generated will find its way to the gear bearing surfaces and the ball races.

    Attachment 317738 Attachment 317737

    The oiler lubricates the clutch hub gear through a small hole near the end of the spray bar and the end of the tube sprays oil onto the outside of the clutch hub itself, some of it will hopefully dribble down to the output shafts plain bush bearing. There is a new hole in the input shaft to lubricate the clutch hub bearing. The input shaft hole was a challenge as the shaft is as hard as the hobs of hell. Thankfully Chambers found a way of doing it with Dremel and diamond bit.

    Attachment 317735

    Oil is feed to the spray bar and up the inside of the gear box input shaft to lubricate the clutch hub and release bearing.

    Attachment 317733

    As well as the dry sump and gear oiler I am trying a longer rod for more crankcase volume.

    The motor was going together really well until I fitted the cylinder. Then I found the fatter rod was jamming around TDC. Now the cases need relieving, bugger, I have to take them apart again.
    Quote Originally Posted by TZ350 View Post
    Another step on the way to building the Suzuki GP/NSR110 super Frankenstein engine, the crankshaft.

    Attachment 316848t

    The GP/NSR110 crank parts.

    Attachment 316844

    Old balance holes plugged with alloy and a Mallory slug opposite the big end. 22mm diameter 60mm long big end pin from a diesel, 115mm RD400 rod, RGV250 big end bearing and small hardened thrust washers. I made the bigger thrust washers out of material that is tough as shark shit.

    Attachment 316849Attachment 316847

    0.8mm side clearance. The flywheels are champhered to allow the wind to flow over the inner edges so the air mass can resonate into and out of the center section with less disruption, (hopefully).

    Attachment 316845Attachment 316846

    50% balance factor. The balancing was achieved by skimming the inside faces of the crank, removed 2mm each side. Plenty of crankcase volume with this baby.

    Back in the 80's a friend once fitted an RD350 crank into a set of RD400 cases, lots of extra case volume with the smaller 350 flywheels. I predicted it wouldn't work, not enough crank case compression, not the done thing etc. etc.... but it worked like a charm.
    Quote Originally Posted by TZ350 View Post
    Many thanks to Kickaha for the GN clutch.

    Attachment 316505

    Honda copy Monkey Bike primary gears are straight cuts which have the same C/C distance as the GP.

    GN Clutch on the left and GP one on the right. Previously I had managed to squeeze an extra plate into the GP one. The original GP 6 plate clutch would slip under power, modifying it for 7 plates cured the slip.

    Attachment 316506

    The big gear is smaller than the original GN125 and GP125 helical gears.

    Attachment 316507

    Once the straight cut gear is fitted to the GN clutch it will spin faster, transmits the same power but the plates are subjected to less torque and the need for cramming in an extra plate to stop clutch slip.

    The new GP/NSR110 is going to have straight cut primary gears and conventional clutch springs.
    Quote Originally Posted by TZ350 View Post
    Spent a happy afternoon checking out the balance of the new 48mm stroke NSR GP110 crank and the NSR cylinder port STA's with the 48mm crank.

    Attachment 316341Attachment 316345

    The crank overall is 12mm wider than a standard GP crank. After setting the crank up and working out the balance weights required for a BF of 50%. I found the Mallory slugs that were fitted to be to heavy but this is good news because I can now keep skimming the inside faces of the crank halves until it comes right. In the end there will be plenty of volume between the crank webs.

    Attachment 316344 Attachment 316343

    Checking out the timing, things worked out much better than I could have hoped for.

    With a 15mm spacer the Exhaust is opening at 80 deg ATDC and Transfers at 118 ATDC and the piston just clearing the port floor at BDC.

    Attachment 316346

    The deck height is -5.7mm for 0.8mm squish. This all matches the optimum STA's worked out with EngMod2T for this project.

    Attachment 316342

    A 15mm cylinder spacer/adapter plate brings the port timing into perfect alignment. (with 115mm RD400 rod, 2010 RM125 piston, 48mm stroke).

    Not bad, a 54mm stroke cylinder fitted to a 48mm stroke motor and the timing works out perfectly.

    Great, up until now it was all on faith and a belief that I could overcome any problems with the idea, but now I know it really is going to work.
    Quote Originally Posted by TZ350 View Post
    The Suzuki V100 2T Scooter cranks have a 48mm stroke and NSR 250 MC21 cylinders are a 54mm bore, 48 x 54 = 109.9cc. The crank is getting a 22mm bigend pin for a 115mm RD400 long rod.

    Attachment 316268 Attachment 316269

    Here is the rest of the story:-

    Original 100cc Suzuki GP motor being fitted with a re-plated (re-bored) NSR MC21 cylinder.

    God Bless those that had the rules changed to 110cc max over bore allowance so they could use cheap over-sized KT100 pistons without going to the trouble required of de stroking to stay within the old 105cc rule ......
    Quote Originally Posted by TZ350 View Post
    Thanks to some very expert engineering help the six speed spacer plate has been made and fits perfectly.

    Attachment 315900

    With the spacer plate fitted the new gearbox has the right sort of end float and spins over very nicely.
    Next move is the long rod crankshaft.
    Quote Originally Posted by Flettner View Post
    Here is a "thing" we machined up today, facilitate a six speed gearbox I believe

  6. #29991
    Join Date
    19th June 2011 - 00:29
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    found an error because of "re-organising" tables, same link with new file : http://users.telenet.be/jannemie/Jan...ng%20Test.xlsm

  7. #29992
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    Quote Originally Posted by wobbly View Post
    The spec for a TM KZ10C selected factory cylinder is 27mm ATDC = 82.54* = 194.92* Duration.
    That certainly doesn't mean they actually are.
    But with the piston radius , there is some conjecture as to what the real timing is effectively.
    It would appear that changing the cylinder height 1/2 the radius on the piston has the effect of great front side power at the expense of overev.
    So now I need to experiment with a slightly higher adjustment, then try an increased radius as well.
    Does anyone know what VHM did with their option piston and insert using a radius.
    They reported a 1 Hp increase , but didnt seem to loose overev in the dyno sheet i have seen.
    Do not know what or if VHM did something with a cylinder head
    https://www.youtube.com/watch?v=4KRwOObWCtA
    No amount of experimentation can ever prove me right; a single experiment can prove me wrong.

  8. #29993
    Join Date
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    I have searched all over the net, and have seen that video from VHM. You can see the piston edge radius but they dont seem to have revealed the insert anywhere I can find.
    And I dont intend on spending the silly money they want for pistons or heads - far rather learn how its done myself , alot more interesting as well.
    Ive got a thing thats unique and new.To prove it I'll have the last laugh on you.Cause instead of one head I got two.And you know two heads are better than one.

  9. #29994
    Join Date
    10th May 2016 - 23:45
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    TM 125MX intake

    The inlet channel of the vforce is not symetric,is this through the carb offset angle?
    The engine has plenty of midrange,but losing on top.
    The engine has a Keihin pwk 38 airstriker, and thinking of replacing pwk for pwm and add a scalvini exhaust.

    Are there more people with experiences with the 2014 TM MX125 engine?
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  10. #29995
    Join Date
    3rd August 2012 - 02:39
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    Closer at home
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  11. #29996
    Join Date
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    Quote Originally Posted by wobbly View Post
    I have searched all over the net, and have seen that video from VHM. You can see the piston edge radius but they dont seem to have revealed the insert anywhere I can find.
    And I dont intend on spending the silly money they want for pistons or heads - far rather learn how its done myself , alot more interesting as well.

    For the 85cc mx engines, they look like this.
    Attached Thumbnails Attached Thumbnails Click image for larger version. 

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  12. #29997
    Join Date
    18th April 2017 - 23:08
    Bike
    Moped
    Location
    Swe
    Posts
    342
    Quote Originally Posted by Muhr View Post
    The block begins to take shape!
    And this is what will look like dressed up.
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    No amount of experimentation can ever prove me right; a single experiment can prove me wrong.

  13. #29998
    Join Date
    19th June 2011 - 00:29
    Bike
    KR-1S, KR1-SV, KXR500, ZXR 4/600
    Location
    Belgium
    Posts
    221
    TZ, came across this : https://ac.els-cdn.com/S187661021733...42e75e70332750

    didn't reed it, but might be useful for you ?

  14. #29999
    Join Date
    8th February 2007 - 20:42
    Bike
    TZ400
    Location
    tAURANGA
    Posts
    3,380
    VeeForce make the carb stuffer to match the stock rubber manifold that has had the ears cut off.
    You can buy the stuffers and cut them in 1/2 to make even a perfectly round entry,this is worth about 1.5 Hp in a TM MX engine.
    Dump the angled manifold, for a straight version, and dump the Airstriker carb ( if you dont need throttle response at 4000 rpm ).
    The straight manifold ( short as possible ) with a PWM gives a huge boost in power everywhere, but especially top end overev.

    The 85cc piston does not appear to have an edge radius at all - only a small angle like Yamaha use ?????
    Ive got a thing thats unique and new.To prove it I'll have the last laugh on you.Cause instead of one head I got two.And you know two heads are better than one.

  15. #30000
    Join Date
    25th March 2004 - 17:22
    Bike
    RZ496/Street 765RS/GasGas/ etc etc
    Location
    Wellington. . ok the hutt
    Posts
    18,573
    Quote Originally Posted by Muhr View Post
    And this is what will look like dressed up.
    So. . When you are producing the gearbox version in significant numbers as a road- legal bike at a consumer product price. . . Make sure you export a bunch over here won't you?
    I've been told. Dreaming`s free.
    Think I'll go, back to sleep.
    Everybody listen, voices in my head
    Everybody listen, do yours say, what mine says?

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