ESE's works engine tuner

[wobbly]

MC21 deck dimension = 30.1mm

[2T Institute]

Has anyone experiences overhauling the Aprilia RS250 / Suzuki RGV crank? Mine needs a rebuild because of too much play at the right conrod.
I want to fit 110mm long TZ250 rods instead of the 105mm series.
1. Is it a good idea to convert the Crank to Washers at the low end? Is it even possible without milling of the crank web on the inside?


Happy to say I was the first to build a long rod rgv/rs engine, conrods can be bottom guided no machining needed

[husaberg]

Anyone have piston dimensions for a nsr250r mc21?

Looking for wrist pin to timing edge of piston crown please. Thanks!

Pretty sure they are on this site
http://edetuckracing.blogspot.co.nz/p/fitting-rm125-pistons.html
here is his site as well
http://nsr250.freeforums.org/

here is plenty of piston, rings and conrod information anyway not related to the NSR250.
http://www.mitaka.co.uk/pistons.htm
http://www.wossnerpistons.com/products/wossner-street-motorcycle-pistons
http://www.pvlsverige.se/vrm/index/index22.html
http://www.tkrj.co.jp/product/m-piston-kit.html
http://www.mingyang-group.2u.com.tw/pdf/CAPT-Motorcycle.pdf
http://www.con-rod.com.tw/motorcycle-connecting-rod.htm
http://www.google.co.nz/url?sa=t&rct=j&q=&esrc=s&source=web&cd=1&ved=0CBwQFjAA&url=http%3A%2F%2Fwww.mingyang-group.2u.com.tw%2Fpdf%2FCAPT-conrod.pdf&ei=iBQJVdibIdXv8gWHmIHoDQ&usg=AFQjCNFf-gNnmOpzO-D1MVppLeMVAqjHUA
http://www.mxcomposites.com/con_rod.php
http://www.connectingrod.com.tw/ktm.htm
http://www.pro-x.com/downloads/Technical.pdf
http://www.kevinbreedonracing.co.uk/...ts_conrods.asp
http://www.connectingrod.com.tw/honda.htm
http://www.samarin.nl/webshop/index....ewCat&catId=32
http://dl.dropbox.com/u/399336/Pictu...ted/HotRod.pdf
http://www.kingrod.com.tw/products.p...t&pc_parent=22
http://www.crankshaftparts.com/index...7_93&limit=100
http://shop.atlanticmotoplex.ca/prod...catalogId=2016
http://jjmachineryonline.com/snowmob...onnecting-rods
http://www.scooter-center.com/scoweb...y2=CAT&lang=en
http://www.bansheedepot.com/products.asp?cat=17
http://http://www.samarin.net/?productos

[Flettner]

come on then Flettner, lets have it. spill the beans,,,,:sherlock:

I'm a bit gun shy to say anything, it is interesting what you learn doing odd ball (dumb) stuff though. I'm sure Ryger wasn't a complete hoax, this high pressure transfer is interesting and being able to present the super homogenized (and heated) fuel air up into the head around the spark plug (with normal fuel air mixture further down the cylinder) might have the answer. Being able to adjust the compression on the fly (as in the beam engine) has a huge benefit for controlling HCCI timing. Ignition still started with the spark plug but shortly after (with the right conditions) HCCI occurs. Well that's the theory anyway. Isn't it ironic that squish may no longer be a good thing. Real work keeps getting in the way though bugger it!

[Tim Ey]

conrods can be bottom guided no machining needed
Well that is what I call lovely news :eek: Thanks a lot!

[jonny quest]

Great links Husaberg! Thank you!

Deck height is 23mm on NSR250 piston.

Wobbly, you must have given me the deck height of a NSR125. They're 30mm

[jonny quest]

What is meant by conrods can be bottom guided?

[breezy]

I'm a bit gun shy to say anything, it is interesting what you learn doing odd ball (dumb) stuff though. I'm sure Ryger wasn't a complete hoax, this high pressure transfer is interesting and being able to present the super homogenized (and heated) fuel air up into the head around the spark plug (with normal fuel air mixture further down the cylinder) might have the answer. Being able to adjust the compression on the fly (as in the beam engine) has a huge benefit for controlling HCCI timing. Ignition still started with the spark plug but shortly after (with the right conditions) HCCI occurs. Well that's the theory anyway. Isn't it ironic that squish may no longer be a good thing. Real work keeps getting in the way though bugger it!

maybe" true" hcci is still a dream away, but maybe new ideas of better si combustion will come from the hcci challenge..... still interested why your hcci test engine suddenly screamed to high rpm before it died...:scratch:

[wobbly]

I have MC18 and MC21 pistons here, they both measure 22.6mm from the pin to the timing edge, checked with a vernier and a height gauge.
The pin is 15 dia so the deck height is 22.6 + 7.5 = 30.1.
This is also mentioned here, when we were looking at RM125 piston fitment.
http://edetuckracing.blogspot.co.nz/p/fitting-rm125-pistons.html

Bottom guided rods are the " norm " and have silver plated washers each side of the thrust faces , with a clearance between 0.6 and 0.8mm.

[jonny quest]

My bad Wobbly. I looked at drawings from link Husayn provided.

I trust you.

I have a MC21, and wanted to do a +2mm to the stock cylinders. I want to use cast pistons, and pistons readily available in the USA. The RM and KX125 pistons are probably my best choice.

This will only be a commuter, not a track day bike. I don't want EX timing any higher than it already is, maybe even a bit lower than stock. Worried if I have to cut bottom of cylinders 1mm, it will mess up all the port floors for what I want to do.

I haven't taken motor apart yet, just general Web searches to get an idea of it's configuration. From what I've found, it's really an oddball motor. Not many part choices for how many they've made over the years

[TZ350]

Some terminology.

323261323258

In the good old days the "Compression Height" was the distance from the center of the pin to the top edge of the piston. Excluding any sort of combustion chamber filling piston dome pop up.

A four stroke piston dome pop up is mostly about boosting the compression ratio by filling up space in the combustion chamber.

323268323260323269

Some call the "Deck Height" the distance between the top edge of the piston and the block deck. The Deck Height can be positive or negative. It is negative if the piston edge protrudes above the block. The block or piston are machined to get the Deck Height required. I guess if it was a two stroke, we would call it "Setting the Squish".

323270

But with all terminology you have to be a little careful about what others mean because the engine block "Deck Height" could also be the distance between the center of the main journals and the top of the block.

[oldjohnno]

So I've been thinking that what I really need is a thermodynamicist, and when I stumbled upon this interview I couldn't help but feel my prayers were answered. I mean, as two stroke builders we're all familiar with concepts like angle/area and so on, but this woman takes us much further with things like heat angles and the circle of hotness. Watch, listen and be in awe.

https://www.youtube.com/watch?v=bbjGdgtscDA

[WilDun]

So I've been thinking that what I really need is a thermodynamicist, and when I stumbled upon this interview

Either I'm on the way out and my brain is dying or something has gone wrong with the kids of today, they speak a different language, but they obviously have an exceptional understanding of things - much greater than mine!
One thing I do understand though, is that someone with that degree of wisdom must be kept out of the workshop at all times! :laugh:

[husaberg]

So I've been thinking that what I really need is a thermodynamicist, and when I stumbled upon this interview I couldn't help but feel my prayers were answered. I mean, as two stroke builders we're all familiar with concepts like angle/area and so on, but this woman takes us much further with things like heat angles and the circle of hotness. Watch, listen and be in awe.
https://www.youtube.com/watch?v=bbjGdgtscDA


Either I'm on the way out and my brain is dying or something has gone wrong with the kids of today, they speak a different language, but they obviously have an exceptional understanding of things - much greater than mine!
One thing I do understand though, is that someone with that degree of wisdom must be kept out of the workshop at all times! :laugh:

Not really the thread for this, but this is the best explanation of how it works

https://www.youtube.com/watch?v=hKWmFWRVLlU
https://www.youtube.com/watch?v=UjBuicfuJ8I

[richban]

After 3 years of slow development, the NSR300 finally is getting what it wants. Proper pipes. Many thanks Wobbly for the engmod help and pipe design. Also thanks Sketchy for the CAD help. Now its time to roll and weld. If I do a good job I will post the finished pipe pics.:sweatdrop No pressure.

[wobbly]

Why are you laughing at her.
We have degrees C and degrees F and they are both the same freehundredansixty degrees of heat - yea.
Your the dumb bastards, quit taking the piss.

[WristTwister]

https://www.youtube.com/watch?v=BKorP55Aqvg

[eldog]

Expert sketch

Most days I feel like 'Anderson' when I deal with some of the customers I have.

Some of them are paid 6 figure sums and still act just like the video, its never their problem

Draw 7 circles in red ink and warm them with 360 degrees of heat

[eldog]

After 3 years of slow development, the NSR300 finally is getting what it wants. Proper pipes. Many thanks Wobbly for the engmod help and pipe design. Also thanks Sketchy for the CAD help. Now its time to roll and weld. If I do a good job I will post the finished pipe pics.:sweatdrop No pressure.

Intrigued with some of the non symmetrical profiles - take your time

will be interesting to see the end result :rockon:

[oldjohnno]

Firstly, my apologies for taking the best thread on the internet off-topic, I promise this will be my last "expert" post.

Anyhow, now that I've picked a thermodynamicist, I thought I could also use someone to conduct a post-race analysis of the logged data. You know what I mean; someone that has a firm grasp of vehicle dynamics and able to take one look at the data dump and know immediately what to do:

https://www.youtube.com/watch?v=Qhm7-LEBznk

[TZ350]

http://www.kiwibiker.co.nz/forums/images/icons/exclamation.png Let's get in the expert! https://youtu.be/BKorP55Aqvg

... :facepalm: ....... :brick: ........ :laugh: .... that is so totally true, and the idiots will be getting well paid, better than the expert anyway.

And that guy that is mocking his wife, well I guess he will find out who the real dummy is...

[peewee]

i finally got the new plating back on this cylinder :2thumbsup. that acid sure reveals any casting or weld porosities. anyways the platers around here put large chamfers on the windows so i instructed them not to touch the windows and i would put a small chamfer on them myself. the outer portion of the cylinder top that seals the water in, needed .5mm shaved off to make it flat again and in doing so i welded the outer portion of the head to compensate.

also the stroke is 2mm longer than standard so the piston sticks above the top deck. looking back i probly should of welded the cylinder top so i wouldn't have to fuss with the surfaces of the head but oh well. my question is i have to recut the squishband and chamber because the piston is about 1.5mm higher now which puts the spark plug 1.5mm closer to the piston. i was going to weld/machine the area where the sparkplug seats to the head so i get my plug/piston clearance back, basically raise the plug in simple terms. is there a common rule for the distance the plug strap should be from the piston top or should i just put the distance to what it was originally ?

all that remains now is shape the transfer passages with devcon and chamfer the windows and get this head sorted out and it should be able to run :2thumbsup

[jonny quest]

Peewee, ground strap to piston =5mm.

Are those exhaust segments laser cut? You must know a guy. I would cut those out with an electric shear.

[chrisc]

Does anyone have a comparison between the standard and A-kit Honda RS125 exhaust duct exit?
Wondering if the actual exit is the same meaning an A-kit spigot could be used on the standard cylinder. I know the exhaust spigot on the A-kit is tapered whilst the standard one is round (stepped with the duct).

[chrisc]

You're welcome

https://www.facebook.com/thomas.vanleeuwen.92/videos/1070116893065489/

[husaberg]

Does anyone have a comparison between the standard and A-kit Honda RS125 exhaust duct exit?
Wondering if the actual exit is the same meaning an A-kit spigot could be used on the standard cylinder. I know the exhaust spigot on the A-kit is tapered whilst the standard one is round (stepped with the duct).

This fella is has what you really are looking for even if it isn't what you are actually asking about.
Replica Aprilia cylinders that bolt onto RS125 Hondas
http://www.50c.nl/Archief%20Ton%20Kooyman-Album-4/14-Techniek/Diversen/Cilinders/Aprilia%20Thijs%20Hessels%20op%20Honda%20RS125/index.html
http://www.50c.nl/Archief%20Ton%20Kooyman-Album-4/14-Techniek/Diversen/Cilinders/Aprilia%20Thijs%20Hessels%20op%20Honda%20RS125/index.html#19-10-inro-12%20Honda%20RS125.jpg

http://www.he-ja.nl/2007-RS125-intro.brits.htm

[Flettner]

This fella is has what you really are looking for even if it isn't what you are actually asking about.
Replica Aprilia cylinders that bolt onto RS125 Hondas
http://www.50c.nl/Archief%20Ton%20Kooyman-Album-4/14-Techniek/Diversen/Cilinders/Aprilia%20Thijs%20Hessels%20op%20Honda%20RS125/index.html
http://www.50c.nl/Archief%20Ton%20Kooyman-Album-4/14-Techniek/Diversen/Cilinders/Aprilia%20Thijs%20Hessels%20op%20Honda%20RS125/index.html#19-10-inro-12%20Honda%20RS125.jpg

http://www.he-ja.nl/2007-RS125-intro.brits.htm

When are you sending that box of stuff up?

[husaberg]

When are you sending that box of stuff up?

I will start tomorrow, if you promise not to do any more videos with your knees showing:bleh:

[Flettner]

I will start tomorrow, if you promise not to do any more videos with your knees showing:bleh:

Health and safety, no knees casting then it is. Just let me have a go at that box of stuff.

[Neal]

This fella is has what you really are looking for even if it isn't what you are actually asking about.
Replica Aprilia cylinders that bolt onto RS125 Hondas
http://www.50c.nl/Archief%20Ton%20Kooyman-Album-4/14-Techniek/Diversen/Cilinders/Aprilia%20Thijs%20Hessels%20op%20Honda%20RS125/index.html
http://www.50c.nl/Archief%20Ton%20Kooyman-Album-4/14-Techniek/Diversen/Cilinders/Aprilia%20Thijs%20Hessels%20op%20Honda%20RS125/index.html#19-10-inro-12%20Honda%20RS125.jpg

http://www.he-ja.nl/2007-RS125-intro.brits.htm


I have recently purchased a used HE-JA barrel and head , just searching for info on what piston they used with it . It's a flat top piston with the ring peg in the centre .


Cheers , Neal

[peewee]

started making some templates for the epoxy on the inside trans wall. printed them from the computer then cut it out of thin alum. they'll work like a treat :headbang:

[2T Institute]

I have recently purchased a used HE-JA barrel and head , just searching for info on what piston they used with it . It's a flat top piston with the ring peg in the centre .


Cheers , Neal
measure the comp height

[2T Institute]

Does anyone have a comparison between the standard and A-kit Honda RS125 exhaust duct exit?
Wondering if the actual exit is the same meaning an A-kit spigot could be used on the standard cylinder. I know the exhaust spigot on the A-kit is tapered whilst the standard one is round (stepped with the duct).

Look up Daniel Cottu on FB he has a A kit Honda 250

[wobbly]

I would not worry at all about the distance between the ground strap and the piston dome.
Ive run it as close as 1.5 mm and seen no issues at all.
The idea with a flat top is to get the spark gap in the middle of the chamber by using a toroid.
With a dome,the best is a flat roof bathtub, so that the highest turbulent zone from the squish action points at the gap.
But I have found that the toroid also works best with a dome, in many situations like aircooled heads or for use with pump gas ie low bmep.
This is what was used on the Webco repro heads I designed.
It allows alot more advance and a leaner mixture before deto, making the head way less fussy to tune closer to the limit.
In all cases a sharp edge from the squish into the chamber is the go.

The A kit Hondas had quite alot larger exit dimensions ie 42mm wide,that was also the header diameter.
The customer RS125s were smaller width, and also had steps,but even that size is too big for a stock port setup.
So you would have to be using the 200* exhaust timing,along with the short A kit pipe length, to make the bigger spigot work properly ie making close to 50 Hp.
Then of course it would need the bigger offset bored SPJ carb and special ignition with different PJ cut etc etc.
So in a word no,you can only use an A kit tapered spigot if you are making A kit power - otherwise weld up the stock exit height and CAD an oval to round transition CNC spigot to suit.

Re port chamfers - you must put chamfers on the Ex before plating or you will grind thru to alloy before getting it correct.
The transfers dont need any chamfer before or after plating.

All genuine A kits ran flat tops with central peg, the flat tops for customer RS125 had an offset peg as the cylinder had a wide gap on one side of the boost port - dumb.
There are dozens of good 54mm single ring with center pin.
Best I have tested would be a Meteor thin ring lightweight for a TM125 - KZ10 ,has a 4* conic dome.

And lastly Husa - those cylinders arent even close to Aprilia replicas,with no radius on the bore/transfer duct, no radius on the Ex port timing edge and stupid old fashioned round ( read stupid big ) duct exit area.

[Flettner]

OK, anyone here know anything about the Ignitech IJ 12 1CH unit? I have one but can't do anything with it, for a start I need software to program it. Ignitech are not interested in replying, at all!

[husaberg]

I
And lastly Husa - those cylinders arent even close to Aprilia replicas,with no radius on the bore/transfer duct, no radius on the Ex port timing edge and stupid old fashioned round ( read stupid big ) duct exit area.
Wob I am only going by what Frits said about them...

Dolph van der Woude is a good friend of Jan Thiel and myself. In cooperation with another friend, Thijs Hessels (picture) he has developed cylinders and other engine parts that can raise the power of an Aprilia RSW production racer to RSA-level. Thijs also makes a conversion kit to fit these cylinders to Honda RS125 production racers, giving them a new lease of life:
http://www.pit-lane.biz/t1693p25-actus-new-world-championship-intercontinental-championship-race-tech

I am picking also they don't give away all their secrets in pictures on the net......
I am pretty sure he also said on another forum they are the closet in execution to the Aprilia bikes other than my PayKarts ones.

[peewee]

kind of a before and after of what I did. got some epoxy in the front transfers tonight and ill work on the others tomorrow. I hope this thing is making smoke soon :wings:. good thing this aint my day job or I'd be broke

[F5 Dave]

So ahh, the small holes below the ex port ? Some sort of oil reservoir perhaps?

[Frits Overmars]

So ahh, the small holes below the ex port ? Some sort of oil reservoir perhaps?http://www.kiwibiker.co.nz/forums/showthread.php/86554-ESE-s-works-engine-tuner/page1054?p=1130802658#post1130802658

[jonny quest]

I've tested a flat top/chamfer piston against dome. All else being equal, the flat/chamfer was a full 1hp better mid on up on a 125

Has anyone tested a flat top vs domed?

I know RSA is domed piston, but for the mere mortal engines the hybrid seems best. Primarily because of excellent flow stability at EX opening.

What gives the pure flat top an advantage? Is it more even "push" on piston during expansion?

[wobbly]

I have tested flat tops Vs domed and the critical element isnt the piston at all, its the chamber shape.
A flat top with a proper toroid will make more power than a dome with a bathtub, and that is way better than a hemi.
Its all to do with spark gap positioning.
Jan tested the difference in the Aprilia but I havnt seen any comment from him anywhere about the chamber configs that were compared, along with the dome shape.

Many people ( including Yamaha ) have found that the flat top with a chamfer ( and VHM with a radius on the timing edge ) is also superior
to the dome - but again it comes back to the chamber shape, and Yamaha for sure has a well developed toroid.
I have also done the hard yards and found the " best " combination when working on the BSL500 piston.
This ended up with the piston edge chamfer matching the squish band width ( at 50% area ) then going flat, this gave the best flow regime from the transfers
around BDC and had a good chamber shape as well.

If you combine that with ceramic coating on the chamber/piston,outside the squish area, then get clever and find a trick way of cooling the squishband
you suddenly have the best elements combined in a synergistic fashion.

Mechanically the two shapes have no advantage over each other - apart from the flat top that wont lock the ring in the groove if deto collapses the top face.
If you collapse a domed piston , even a little, it automatically crushes the ring groove,leading quickly to a seizure and a DNF.

[jonny quest]

Great reply Wobbly, thank you!

I've modified domed pistons into the Hybrid design, copying Yamahas chamfer width ratio. Needed to cut .070" off dome. I had one failure out of 5 that I modified, piston cracked at dome. Didn't cause any harm, but not good nonetheless. I knew I was risking it.

I was going to try the chamfer to match squish percentage next. For my applications, that should be no problem with piston strength.

[2T Institute]

Wob I am only going by what Frits said about them...

I am picking also they don't give away all their secrets in pictures on the net......
I am pretty sure he also said on another forum they are the closet in execution to the Aprilia bikes other than my PayKarts ones.

I have seen He-Ja equipped bikes get around they are a few hp off full house RSW 125 power levels

[peewee]

I use a 1.5mm dia needle roller from a little end bearing . Material is tough and also polished so there is no fretting on the ends of the ring. Drill down from the top of the piston allowing for some interference fit (say .05mm ) so the end of the pin is 1 - 1.5mm below top of piston, then weld over the hole to prevent the pin from coming out. You may get a slight swelling of the piston diameter at the position of the pin. Dress this off carefully with a mill-cut file. With a two ring piston you will have the ring gap in the same spot for both rings but this is fine.

good job mate. in the garage found a yami needle bearing from the clutch actuator arm. 1.5mm x 10mm needles. exactly what I needed.

[husaberg]

I have seen He-Ja equipped bikes get around they are a few hp off full house RSW 125 power levels

I guess some of that maybe because they are missing that rotary whatawacallit intake thingwajig....:niceone:

[2T Institute]

I guess some of that maybe because they are missing that rotary whatawacallit intake thingwajig....:niceone:

42mm carby

[F5 Dave]

150mm rod.


(I assume we're playing top trumps)

[2T Institute]

RSW 125/250 only went to 115mm rod

[wobbly]

Biggest issue is they aint got a freehundredansixtydegree temperature gauge.

[chrisc]

Speaking of temperatures.

Wob, I got one of your thermostats from Steve Bagshaw which I'm going to fit to my 125. Any sharp leads on radiator hoses and a t-junction for the lower hose, before I go on the search myself?

[wobbly]

Here is how I did it on the TZ400.
Hoses are silicone off trademe,I have seen nice stainless T junctions available from Mico I think.
But hoovering up an alloy one isnt hard.

[husaberg]

Here is how I did it on the TZ400.
Hoses are silicone off trademe,I have seen nice stainless T junctions available from Mico I think.
But hoovering up an alloy one isnt hard.

The Engine there Wob, has it been changed?
It looks piston ported now.

[shnaggs]

Hi there fine gentleman,

I've been a lurker on this site for over half a year, lots of great stuff and great minds on this site...and I thank you for that!

If any of you could give me your input on a few matters in regards to Engmod, it would be much appreciated.

1) when reading the mach index traces on the exhaust, I'm a bit confused at what the numbers actually represent? I am no engineer, but if I see a peak value of .8, does that mean that I am seeing 80% of the speed of sound?

2) I've been trying to replicate the leaning out and retarding Ign on over-rev, to get some more usable power past peak, but when I try to simulate it, it doesn't work. If I keep it on the rich side and adv. the timing, I gain more over-rev??? What am I doing wrong?

Thanks in advance!

[wobbly]

Re the TZ400 cylinder, that was just a dummy piece I used to build the pipes - the reed cylinder was away being plated.

Re the EngMod questions - Mach 0.8 is as you say 0.8 X Sonic.
If you change the A/F ratio from say 12:1 at say 12,000 to 13:1 at 12500 the Ex temp will rise in the pipe, but just as in reality the lower fuel energy
available my not in fact be sufficient to make more power.
This is way more likely to be affected by the Delivery Ratio dropping greater than the pipes positive effect from temp has on Hp.
Pulling out advance also affects the pipe temp, but again in many cases the engine efficiency drops way more rapidly than the rise in power seen from the pipe effect.
Thus if the bmep drops, then cylinder pressure drops, and more advance will often make better power - just as in reality, again.
What average pipe temps are you using, as this input shows a much greater effect on the Hp curve.
Remember that a solenoid powerjet is not " leaning out " the mixture, it is simply opposing the carbs natural tendency to go rich over the top of the powerband .
ie the A/F ratio is forced to remain alot closer to a constant number, not rise to make the engine hotter.

[shnaggs]

Re the TZ400 cylinder, that was just a dummy piece I used to build the pipes - the reed cylinder was away being plated.

Re the EngMod questions - Mach 0.8 is as you say 0.8 X Sonic.
If you change the A/F ratio from say 12:1 at say 12,000 to 13:1 at 12500 the Ex temp will rise in the pipe, but just as in reality the lower fuel energy
available my not in fact be sufficient to make more power.
This is way more likely to be affected by the Delivery Ratio dropping greater than the pipes positive effect from temp has on Hp.
Pulling out advance also affects the pipe temp, but again in many cases the engine efficiency drops way more rapidly than the rise in power seen from the pipe effect.
Thus if the bmep drops, then cylinder pressure drops, and more advance will often make better power - just as in reality, again.
What average pipe temps are you using, as this input shows a much greater effect on the Hp curve.
Remember that a solenoid powerjet is not " leaning out " the mixture, it is simply opposing the carbs natural tendency to go rich over the top of the powerband .
ie the A/F ratio is forced to remain alot closer to a constant number, not rise to make the engine hotter.


Thanks for the response Wobbly.

I am starting the exhaust wall temp at 325* and have peak power at 425*, I got those numbers from earlier in this thread. Are these numbers close to reality in a MX application?

As you stated above ^^^ I am seeing more over-rev with advancing the timing and keeping A/F constant. So this is due to the delivery ratio dropping off? So does that mean that if I increased the time-area of intake and exhaust the delivery ratio shouldn't drop off as much, allowing the heated pipe to suck more?

Was not aware of the powerjets keeping the a/f more constant on over-rev. Makes sense now that I think about it.

Thanks again!

PS. Wobbly, what combustion efficiency number would you use for a MX 250 with a bore of 66.4mm, and stroke of 72mm?

[wobbly]

So if you are running a solenoid powerjet you can simulate its action more accurately by setting the pipe temp at 450 at say 500 rpm past peak.
It will take some fiddling to find the element that is affecting the power the most past peak.
I have found time and again that all it needs is to pull down the Ex exit area to 75% and add a tapered nozzle out to the 100% header area.
The increased pipe temp doesn't make it " suck " more it increases the wave speed,that in turn reduces the effective tuned length.
You can try adjusting the intake length to get it into resonance in the overev, depending upon the harmonic being used and the room available.

A 250 well tuned will sim accurately at around 85 to 88% C.E

[richban]

Progress.

I've learnt so much I want to start again!

323395

[wobbly]

Yea, the problem you now have is that as you have assembled the rear cones, you cant use a mandrel to tap the seam together
before or after welding.
Rule 1A is to always move along one weld at a time, so each seam can be tacked, tapped together accurately, then welded, then hammered flat.
To do it perfectly like the factory Ti pipes, the cones have to be absolutely round, and with purge gas up inside, the seam then cold wire over tig welded.
Then no hammering is needed, as the seam is as good on the inside as it looks on the outside.

[peewee]

worked all weekend with the epoxy. templates worked a treat. not sure if you can tell but these passages were never intended to have a large teacup (B and C are worse off because the inner radius is larger than A) :laugh:. technically I guess theyre not actually a teacup but rather more like a half circle , similar to the rsa. I even grinded the gasket surface 6mm farther outward which is as much as the crankcase deck will allow without welding them wider. what ill probly have to do is grind some what of a teacup in the outter wall also , other wise there will be a choke point half way up the passage where the inner wall reaches its max radius

[F5 Dave]

Indeed, that I believe was my mistake when I did my 100. I think I reduced the volume of the transfers too much. Vinamold showed me what the finish was like where it was hard to see but your cylinder has the luxury of plenty of space.

[shnaggs]

So if you are running a solenoid powerjet you can simulate its action more accurately by setting the pipe temp at 450 at say 500 rpm past peak.
It will take some fiddling to find the element that is affecting the power the most past peak.
I have found time and again that all it needs is to pull down the Ex exit area to 75% and add a tapered nozzle out to the 100% header area.
The increased pipe temp doesn't make it " suck " more it increases the wave speed,that in turn reduces the effective tuned length.
You can try adjusting the intake length to get it into resonance in the overev, depending upon the harmonic being used and the room available.

A 250 well tuned will sim accurately at around 85 to 88% C.E

Thanks again Wobbly, I will have to tinker around with that some more.

Damn I am showing my ignorance, makes sense though now that I think about it. Higher temps= the pulses moving faster, ie the pipe effectively gets shorter, not "sucks" more. Thanks for the clarification.

Right now I'm at 82.5% C.E. This is what is boggling my mind, if I raise the C.E. up to around 88% I'm almost at 70hp!!! Either I have totally messed something up, or I have stumbled upon gold. I'm sure it is the first...

I made all my measurement's as accurately as my small brain can. The only part I guessed at was: crank case volume.

[wobbly]

Keep in mind that the sim reads out crank power.
When using a normal street tire or slick you deduct around 12% to 15% to give power as seen on a Dynojet.
ie 70 Hp = 62 RWHp to 59 RWHp = OK for a good 250.
The very best 250 road race engine are getting high 60s at the rear wheel of a kart, that has little wheel inertia so probably mid 60s
if done with a bike wheel on a Dynojet.
When putting a long rod into a YZ250 and using a spacer plate power rises, now who knows if that is due to the rod or the case volume - it works.
What case vol ( with transfers ) did you use.

[peewee]

Indeed, that I believe was my mistake when I did my 100. I think I reduced the volume of the transfers too much. Vinamold showed me what the finish was like where it was hard to see but your cylinder has the luxury of plenty of space.

ill print out some more templates for the outer wall then final check everything with the vina. the entrance probly wont be near as big as it should but this is the only thing I can see to do at this point. I believe the reason the entrance is so small is because it had 140mm rod with 82mm stroke. theres now a spacer plate but the bad initial design hampered what I could do with it

[shnaggs]

Keep in mind that the sim reads out crank power.
When using a normal street tire or slick you deduct around 12% to 15% to give power as seen on a Dynojet.
ie 70 Hp = 62 RWHp to 59 RWHp = OK for a good 250.
The very best 250 road race engine are getting high 60s at the rear wheel of a kart, that has little wheel inertia so probably mid 60s
if done with a bike wheel on a Dynojet.
When putting a long rod into a YZ250 and using a spacer plate power rises, now who knows if that is due to the rod or the case volume - it works.
What case vol ( with transfers ) did you use.

I used 900cc with transfer volume. It was a rough guess and it got me close to 1.6 crank case ratio, which I read was a typical ratio for a mx 250.

This may be a stupid question, but could you in theory make a good pipe/tune for an engine that makes more power then you would really need in your application, and then use the power valve opening to cut the top off the power band, essentially making for a more linear/wider power band???

[TZ350]

... could you in theory make a good pipe/tune for an engine that makes more power then you would really need in your application, and then use the power valve opening to cut the top off the power band, essentially making for a more linear/wider power band???

Keeping things in resonance for longer sounds like a good idea for extending the power spread. But I think lowering the power valve at the top end to flatten the power curve by strangling the top end power by reducing the effective blow down time area is likely to promote detonation. Due to the cylinder being unable to be purged properly and the excess residual hot combustion gasses being forced back down the transfer passages and overheating the fresh incoming air/fuel mixture.

[wobbly]

If I assume you are measuring the case volume with the piston at TDC, then 900-250 = 650.
900/650 = 1.38 CCR.
This is a perfectly normal CCR for a 250MX - 1.6 is completely insane if it was measured or a wild guess.
But as I said, adding a 5mm plate under the cylinder when going to the 130 long rod makes more power.
So a bigger case ,getting closer to 1.3 is a good thing for the highly modded kart race engines.

[peewee]

1.6 would be crazy. seems like one of the engines i have might of been around 1.5 but it was crap from the early 1980s. to get beyond 1.5 or so , would probly really take some misguided efforts. very short rod and a wristpin located near the piston crown

[peewee]

ended up changing out the rod and piston which allowed about a 8mm spacer. never did recheck the volume

[peewee]

sorry guys the edit button seems to be broke but i remembered the rod stroke ratio was originally only 1.7 which i think is part of the reason the case ratio was through the roof and the wristpin was higher than i have ever seen in my life

[wobbly]

You can, in all cases, create a huge amount of extra power, in a particular band, by changing the Ex port timing.
This can, and usually does, badly affect the Ex STA, but if as a consequence the pipe goes into superposition resonance,then this effect is way greater than
the effect of the limited STA.
You can arrange the superposition to occur at any rpm, with the limitless combinations of pipe length and port timing.
Usually the best effect is seen when the residual pressure in the duct rises, as the rpm goes over the peak of the pipe/port - then it will just keep on reving instead
of hitting a wall as the power drops off savagely.

[Peter1962]

Keep in mind that the sim reads out crank power.
When using a normal street tire or slick you deduct around 12% to 15% to give power as seen on a Dynojet.
ie 70 Hp = 62 RWHp to 59 RWHp = OK for a good 250.
The very best 250 road race engine are getting high 60s at the rear wheel of a kart, that has little wheel inertia so probably mid 60s
if done with a bike wheel on a Dynojet.
When putting a long rod into a YZ250 and using a spacer plate power rises, now who knows if that is due to the rod or the case volume - it works.
What case vol ( with transfers ) did you use.


Wobbly, is this specific for the yamaha yz250 engine, or have you seen the same effect on a honda cr or ktm 250 ?

[wobbly]

Same effect on a late model KTM250 using a long rod and plate.
The small case does work best for the MX tuning where they pull out of corners at 4500, simply better throttle response.
But in karts and road racing, the long rod combined with the bigger case works with all the other mods done to increase upper and top end.
But having said that for so called "expert " use on a 250 MX, every man and his dog used the long rod and plate for years in the YZ250 range of engines.

[shnaggs]

Yeah bugger. I did the calc wrong on the crank case. just did a run now with 1.33 volume, now my numbers are much more worldly and pathetic! :facepalm:

I do appreciate you guys keeping me on the straight and narrow.

Wobbly, you talking about the pressure rising in the duct after peak hp...do you mean port duct, or header?

[ief]

But doesn't that imply that raising the ccv to 1:1.6 raises the power to unworldly figures and doesn't that then imply there must be something else wrong?

[shnaggs]

There seems to be a glitch in engmod I think. I am using the 'crank case calculator' to determine my ratio. No matter which option I pick, it automatically selects 'transfer volume excluded from ratio'.

If I enter 900 in 'BDC volume plus transfer volume', hit calculate, I get 1.33. But then it highlights 'transfer volume excluded from ratio'?
Well, didn't I just use it in the volume calculator???

Is this wrong or am I wrong? Lets just say that 1.3 ccv is a good ratio, should I include or exclude the transfer ports in the ratio? About a 3hp difference for me.

[ief]

Glitches aside, if using 1.3 gives 'normal' outcome and 1.6 gives better outcome but real world says 1.3 should be better something is a miss right?

Not that I know how and what, just saying, also not claiming that's an engmod issue!

Engmod seems glitchy here and there, hope the next update adresses those instead of new features. Ccv I calcuated by measuring the total volume including transfers, then measure the volume of transfers and see if these where the same as calculated in engmod.

Hope that helps somewhat, it's bin a while :)

[wobbly]

All the 250s I have actually measured are mid to high 1.3 ratio.
When you are watching the Ex pressure trace ( measured at the port face ) you will see the pressure ratio varying in value where it crosses
the cursor at EPO.
You will have superposition when the crossing point is above 0.
The higher this value the higher the scavenging ratio at the port goes - a really good diffuser with the added superposition will go off the scale.
Here is an example of good superposition and a really good diffuser acting together.

[wobbly]

I have absolutely no idea how one can measure the case volume without the transfers - please educate me.
Engmod calculates the transfer volume from the port area, the inlet/exit ratio and the duct length, so this volume is
entirely dependent on the input accuracy, especially the correct length ( as this is also a large part of the case, if you read the help files ).
Running the code with a CCV of 1.6 is an insane input, so the result will be equally insane output - its not a sim issue at all.

[jonny quest]

See if someone knows the answer to this here.

The MC21 is 45HP restricted by CDI timing curve. There is a well known wire splice mod, but it also has a gear position sensor.

From my understanding, 1st gear is most agressive timing curve, 2nd slightly less agressive, and 3rd gear a decent curve for pump gas street use.

My question, if you don't perform the wire splice mod, leave everything stock... are these bikes 60HP in 1st, 2nd, and 3rd gear.... but restricted to 45HP in 4th, 5th, and 6th?

[richban]

See if someone knows the answer to this here.

The MC21 is 45HP restricted by CDI timing curve. There is a well known wire splice mod, but it also has a gear position sensor.

From my understanding, 1st gear is most agressive timing curve, 2nd slightly less agressive, and 3rd gear a decent curve for pump gas street use.

My question, if you don't perform the wire splice mod, leave everything stock... are these bikes 60HP in 1st, 2nd, and 3rd gear.... but restricted to 45HP in 4th, 5th, and 6th?

I had major problems with the wire splice method when I first got the NSR300 going. We messed around for ages and could only ever get 60hp. Plug in HRC bypass loom and 72 straight away. I run an ignitech now. We never did an all gears run so could not tell you about 1st to 3rd sorry.

[ief]

Running the code with a CCV of 1.6 is an insane input, so the result will be equally insane output - its not a sim issue at all.

Oke, that will be true but then... I start at 1.3 and increase it and it keeps making more power. How do I know where the input starts being insane or, probably a better question, what am I not adjusting as well so the power doesn't go up anymore since that wouldn't be the case in real world?

ps; more of a hypothetical question btw although I to have encountered this 'issue' in the past, never went to 1.6 though. Would have to dive in again to see how my model fares now, maybe a none issue but perhaps for broather understanding of things/ engmod.

[shnaggs]

Thanks Wobbly again for the example above regarding the exhaust.

My question was, why does engmod default the crankcase volume to exclude transfer port volume from the ratio, when we are using the transfer volume to do the calculation?

I've just opened some of the other projects to verify. The radio button of, 'transfer volume excluded from ratio' is always selected. Should we be running the sim with, 'transfer volume included in ratio' instead?

[jonny quest]

Richban, are you talking about installing the complete HRC wiring loom that eliminates the lights?

Or a type of inline small wiring setup that HRC made?

[wobbly]

The code will always have the transfer duct volume available to it, as I pointed out you have to input the areas and length.
But Neels must have been reading this thread and has just sent me an update to make the inputs clearer to everyone.
I will install this tonight and report to him and you.

Edit - OK Neels has changed the help file to make clear what is happening.
In most cases you will simply be using the default ie a volume measured a TDC thru a hole in the piston and this of course includes the transfer ducts.
He has made it clear now why we need other options, including the fact that if you change the transfers, this will then be updated automatically in the code as CCR ie Calculated Compression Ratio

Regarding useful values of case vol.
The Aprilia RV engine has it down at 1.24 or so ie a huge volume as would befit it huge power output.
I have found that 1.3 is about the optimum top limit for a full house reed engines ie KZ kart 125, as with a bigger case you have to keep on installing thinner reed petals and eventually they hit the stops and go spastic
or simply lift too far then flutter with no control.
This I have absolutely dynoed to death on the TM KZ10B kart engine, as a small change in case vol under 1.3 looses mid power, and a small change above 1.3 with a reed spacer looses
all the overev power - no matter what reed stiffness is used in each case..

Engines with crap transfer ducts need the ratio up closer to 1.4, and I have never seen anything go at all well with a case smaller than 1.4 ( by smaller I mean volume ie say 1.45 ).
But as always remember that the code can only recognize crap ducts in a limited fashion ie the input you have control over in specifying the shape.

Re MC21 and its ignition control.
There are two parts to the Honda ignition control.
First is the blanket retard function that is easily disabled with the wire splice method.
But secondly there is a function that limits the road speed to 180Km/Hr max in 4th,5th,6th.
This can be disabled by fooling the ECU into thinking it never goes past 3rd gear.
As to the curve in 1st gear being the most aggressive, this is a possibility, but I have never seen any evidence that the PGM software has the ability to store
more than 2 curves.
So it makes sense that 1, 2, 3 are the same and 4.5.6 are the same.
Reworking the gear detector so it never tells the ECU 4th is selected would keep the more aggressive curve active.
I only say more aggressive in that as the rpm rate of change is so much faster in the 3 lower gears, Honda would be logically happy to wind in alot more advance without
fear of meltdown on shit fuel and or long periods of WOT.

[ken seeber]

All the 250s I have actually measured are mid to high 1.3 ratio.
When you are watching the Ex pressure trace ( measured at the port face ) you will see the pressure ratio varying in value where it crosses
the cursor at EPO.
You will have superposition when the crossing point is above 0.
The higher this value the higher the scavenging ratio at the port goes - a really good diffuser with the added superposition will go off the scale.
Here is an example of good superposition and a really good diffuser acting together.

Hey Wob, the minor pressure fluctuations (of around 40 to 45 deg) in the transfer port after TPC, are they real as a result of resonance within the passage or some reed tip frazzle OR some EngMod calculation perturbation? The pipe is doing a good job, well to me anyway.

[wobbly]

Hey Ken, I have always thought that the sine wave fluctuations in the transfer ducts after TPC were a result of them being converted from an open pipe ( ie the duct open at both ends )
into a stopped organ resonator ie one end only open.

The pipe in the example I gave was well past its designed peak, as the max pipe/port depression is well past BDC, but the superposition of the scavenging effect is so strong it easily overcomes this
natural movement of the peak depression moving rightward ( too late ) with rpm.

[ken seeber]

Hey fellas,

http://www.grampianmotors.co.uk/

This is a neat site in that if you, say, go to MITAKA, click on road bike rod kits, then your bike & model and up comes the rod crs, widths, diameters etc. Ditto with pistons. Good if you're chasing bits to swap around between motors.

[husaberg]

Hey fellas,

http://www.grampianmotors.co.uk/

This is a neat site in that if you, say, go to MITAKA, click on road bike rod kits, then your bike & model and up comes the rod crs, widths, diameters etc. Ditto with pistons. Good if you're chasing bits to swap around between motors.
http://www.kiwibiker.co.nz/forums/showthread.php/86554-ESE-s-works-engine-tuner?p=1130987881#post1130987881
You can keep Russell Crowe but we want Far Lap back.:innocent:

[shnaggs]

Wobbly, thanks for the update, and thanks for the detailed results and explanations.

And Neels, thanks for the update as well, and sorry for not going directly to you before stirring the pot here on the forum. It all makes sense now.

[Vannik]

And Neels, thanks for the update as well, and sorry for not going directly to you before stirring the pot here on the forum. It all makes sense now.

Please feel free to ask anything you like on this forum - there are enough experts to help you and it shows me where to improve!

[TZ350]

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.

323702

Micro polished gear-set courtesy of Morgan Engineering.

323700323701

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.

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.

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.

[peewee]

Engines with crap transfer ducts need the ratio up closer to 1.4.


mines barely over 1.3 with vf4 which seems to be some of the thinest petals ive seen. any predictions how it will turn out since it isnt running yet ? incase it doesnt go well ive got plan B which is higher wristpin pistons

[mr bucketracer]

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.

323702

Micro polished gear-set courtesy of Morgan Engineering.

323700323701

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.

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.

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.whats with this buying heads .gpr boys make them 323713

[TZ350]

whats with this buying heads .gpr boys make them 323713

Yea I know, buying one, totally piss poor of me ... :laugh: ... your head work looks great, very impressive.

[jonny quest]

Curious, why did you use a NSR barrel TZ?

[2T Institute]

135/90 disc timing will make better mid range and top end

[jasonu]

Curious, why did you use a NSR barrel TZ?

My guess is because he already had one in a box somewhere...

[SwePatrick]

About HCCI ignition(i think)
I have built a new engine(not fully complete yet)
Test started it this weekend.

It´s an Kawasaki KX250 downstroked to 211.9cc(due to regulations in swedish dragracing)
However, i was so eager to hear the engine spin even though the pipe isn´t ready yet.
So i started it anyway.
And note, the exhaustvalves wasn´t in place, the guillotine therefor left a big hole downwards in exhaustport(no lid on either)

Engine started nicely but started to rev out of control almost directly.
Tried to stop it, pulled the cord to the stop button, nothing happened.
Placed hand onto the carburetor, nothing happened.
With hand still on carb and full throttle engine lowered the speed.
Had to shut off fuel to get it to stop.

Later, put back all exhaustports and started engine with no other adjustment.
It ran nicely on idle.

Quite interesting experiance ;)

I figure the exhaustpulses drew fresh air into cylinder through guillotineport.
And even though i had hand on carb it still drew fuel enough to get a burnable mixture.
But, interesting is that what i think it almost directly triggered HCCI.

Rgds.

[TZ350]

Curious, why did you use a NSR barrel TZ?My guess is because he already had one in a box somewhere...

Pretty much true …. like all good Bucket racers, plenty of junk in a box under the bench.


Curious, why did you use a NSR barrel TZ?

The F4 F5 (Buckets) is a formula road racing class with a mix of small capacity four and two strokes where the engine/gearbox components have to be sourced from a non-competition engine, no road racing or MX allowed except for a few specific exceptions like piston and ignition.

It used to be in F4 that a water cooled two stroke could only be 104cc max oversize but to make things easier/cheaper for themselves some bright spark got the re-bore allowance increased to 110cc but restricted to a 24mm carb.

Here in New Zealand the RGV250 and NSR250 were popular road bikes. Some people sleeved the 56mm RGV cylinder down to get their 104cc, I guess because it had easily modified power valves to suit the smaller bore.

But now that 110 is allowed using an old re-bored (re-plated) cylinder and de-stroking is an easier to meet the class rule. So I have recycled my old GP100 bottom end and shortened it’s 50mm stroke to 48mm and fitted a re-plated (re bored) 54mm NSR250 cylinder. That way, at 110cc I still have the same bore/stroke ratio as I had with my original Suzuki GP125 air cooled motor. Not ideal, square would be ideal but at least workable.


135/90 disc timing will make better mid range and top end
Yes, this temps me because, on the dyno I have seen the air/fuel mixture bouncing back of the closed rotary valve at 80 and 85 deg atdc so maybe 90 will allow a bit more to be squeezed in (TZ’s were 90/90) and I agree opening 135 btdc is more the norm than 145.

[jonny quest]

I didn't realize you couldn't use MX cylinders. Surprised at that. They're popular, and would be a cost effective means.

That's why I asked TZ. The NSR cylinder is decent, but CR is better.

[TZ350]

I didn't realize you couldn't use MX cylinders. Surprised at that. They're popular, and would be a cost effective means. The NSR cylinder is decent, but CR is better.

Agreed a CR125 cylinder or complete engine would be much better and possibly cheaper (in time anyway) but the Bucket non competition thing is a deliberate self inflicted inconvenience for the sake of keeping things relatively cheap for racing with the spin off of learning something about engine tuning and engineering in general.

An objective of the Bucket racing rules is to oblige you to earn your competition hp by building something clever out of non competition engine bits, and to prevent you from taking the easy way out by buying factory made hp, there are other racing classes for that.

[lodgernz]

Agreed a CR125 cylinder or complete engine would be much better and possibly cheaper (in time anyway) but the Bucket non competition thing is a deliberate self inflicted inconvenience for the sake of keeping things relatively cheap for racing with the spin off of learning something about engine tuning and engineering in general.

One of the Bucket objectives is to oblige you to earn your competition hp by building something clever out of non competition engine bits, and not to take the easy way out of buying factory made hp, there are other racing classes for that.

Beautifully and succinctly put TeeZee.

[Frits Overmars]

Agreed a CR125 cylinder or complete engine would be much better and possibly cheaper (in time anyway) but the Bucket non competition thing is a deliberate self inflicted inconvenience for the sake of keeping things relatively cheap for racing with the spin off of learning something about engine tuning and engineering in general.
An objective of the Bucket racing rules is to oblige you to earn your competition hp by building something clever out of non competition engine bits, and to prevent you from taking the easy way out by buying factory made hp, there are other racing classes for that.
Beautifully and succinctly put TeeZee.Same here. I like both the Bucket philosophy and the way you described it Rob.

[jonny quest]

http://www.greencarcongress.com/2016/08/20160805-anltribo.html


Researchers at Argonne National Laboratory have discovered an ultra-durable, self-lubricating tribofilm that regenerates in the presence of oil, heat, and pressure—meaning that it will not wear away over the life of an engine. The film, reported yesterday in the journal Nature, develops when a new catalytic coating that can be applied to engine parts interacts with lubricating oil to create an extremely tough coating that almost eliminates wear.

Tests revealed the diamond-like carbon (DLC) tribofilm reduced friction by 25-40% and that wear was reduced to unmeasurable values. The discovery could have implications for the efficiency and durability of future engines and other moving metal parts that can be made to develop self-healing DLC tribofilms.

This is a very unique discovery, and one that was a little unexpected. We have developed many types of diamond-like carbon coatings of our own, but we’ve never found one that generates itself by breaking down the molecules of the lubricating oil and can actually regenerate the tribofilm as it is worn away

[2T Institute]

Agreed a CR125 cylinder or complete engine would be much better and possibly cheaper (in time anyway) but the Bucket non competition thing is a deliberate self inflicted inconvenience for the sake of keeping things relatively cheap for racing with the spin off of learning something about engine tuning and engineering in general.

An objective of the Bucket racing rules is to oblige you to earn your competition hp by building something clever out of non competition engine bits, and to prevent you from taking the easy way out by buying factory made hp, there are other racing classes for that.

Only problem is that the pile of broken/discarded bits is twice the cost of a competition engine and still fragile at the limit. You do learn a lot that is true but taking an an already highly tuned and developed engine and increasing it's output is much steeper learning curve than hotting up a mudbug.

[Flettner]

About HCCI ignition(i think)
I have built a new engine(not fully complete yet)
Test started it this weekend.

It´s an Kawasaki KX250 downstroked to 211.9cc(due to regulations in swedish dragracing)
However, i was so eager to hear the engine spin even though the pipe isn´t ready yet.
So i started it anyway.
And note, the exhaustvalves wasn´t in place, the guillotine therefor left a big hole downwards in exhaustport(no lid on either)

Engine started nicely but started to rev out of control almost directly.
Tried to stop it, pulled the cord to the stop button, nothing happened.
Placed hand onto the carburetor, nothing happened.
With hand still on carb and full throttle engine lowered the speed.
Had to shut off fuel to get it to stop.

Later, put back all exhaustports and started engine with no other adjustment.
It ran nicely on idle.

Quite interesting experiance ;)

I figure the exhaustpulses drew fresh air into cylinder through guillotineport.
And even though i had hand on carb it still drew fuel enough to get a burnable mixture.
But, interesting is that what i think it almost directly triggered HCCI.

Rgds.

No doubt true, as I had a similar problem with my HCCI mudbug (100cc yamaha), hand over the inlet didn't stop it. It was getting air in again each cycle via the exhaust port. I also had no exhaust system attached, interesting isn't it.
In my case I didn't even have an electrical ignition to try to turn off. It certainly gets the heart rate up! See what happens when you dick around doing dumb stuff, you learn dumb shit::facepalm:
All you need is a bit of HCCI control:shifty:
https://youtu.be/9zhFsS_ocuQ
https://youtu.be/VBVMGywXVr8
https://youtu.be/OCBngYfWiTE

I guess this is a free piston engine, that last one certainly has some grunt.

[F5 Dave]

Decompression valve should sort it out. Probably a bit abrupt but. . .

[chrisc]

What should the deposits look like on the piston and head for a well functioning race 2 stroke?

Just changed the ring on the Derbi 50 and repacked the muffler so I shot a few photos:
323800323801

[Frits Overmars]

What should the deposits look like on the piston and head for a well functioning race 2 stroke?
Just changed the ring on the Derbi 50 and repacked the muffler so I shot a few photos:
323800323801You might want to check the squish gap fore and aft.

[diesel pig]

What should the deposits look like on the piston and head for a well functioning race 2 stroke?

Just changed the ring on the Derbi 50 and repacked the muffler so I shot a few photos:
323800323801

With the earth strap not quite burned half way and the fair amount of wash around the edges of the piston I would say a touch rich but not bad at all.

[chrisc]

You might want to check the squish gap fore and aft.

Was thinking that but wasn't sure if it was impacted by being the exhaust side. Will do.

[Neal]

I had major problems with the wire splice method when I first got the NSR300 going. We messed around for ages and could only ever get 60hp. Plug in HRC bypass loom and 72 straight away. I run an ignitech now. We never did an all gears run so could not tell you about 1st to 3rd sorry.

That's the way I understand it too

[Neal]

Richban, are you talking about installing the complete HRC wiring loom that eliminates the lights?

Or a type of inline small wiring setup that HRC made?

You could buy a hrc wire splice in a adaptor loom and just plug it in to get full power , the gear position splice is a different mod

[Sketchy_Racer]

Was thinking that but wasn't sure if it was impacted by being the exhaust side. Will do.

The head needs to be dowel located to the bore. That is why the squish won't be even. Dave and I machined that head profile just before heading to Tokoroa and ran out of time to dowel her up.

[F5 Dave]

Two outer bolts Ithink bored for dowels. We did squish test with solder front and rear at same time held with plasticine or grease. Should be 0.5.

[jonny quest]

Does anyone know if the stock MC21 chambers have internal stingers?

[wobbly]

Using a " normal " earth strap to read the chamber conditions is not accurate at all due to its very high thermal mass .
Fine wire electrodes give a very good indication of the combination of advance and jetting leannes.
Having the burn mark change about 2/3 of the way toward the body is spot on.
At 1/2 distance you can look at winding in some more advance if the egt is at optimum power.

Usually the rear of the pistons squish ( over the boost port ) will mark up more due to heat as when the piston rocks over TDC
this side closes the squish gap up, increasing the MSV and the retained heat in the end gases..
Here is a KZ10 that has a straight line ignition, tuned right to the edge after a 25 lap final, any more advance and the piston would be starting to deto.
The other is a 66mm piston in a RZ400 that has done 480Km racing miles, one piston is jetted slightly richer,but the squish gap is perfect.

[chrisc]

Using a " normal " earth strap to read the chamber conditions is not accurate at all due to its very high thermal mass .
Fine wire electrodes give a very good indication of the combination of advance and jetting leannes.
Having the burn mark change about 2/3 of the way toward the body is spot on.
At 1/2 distance you can look at winding in some more advance if the egt is at optimum power.

Thanks Wob. From reading on here and a few other places that's how I've understood it too. Good to have confirmation.
The main thing for me and this bike at the moment is reliability, suspension and gearing. I won't be doing any engine development until I have some of my own baselines so it's good to know it's probably on the safer/lower power side. It shouldn't be giving me any issues whilst I sort out the meat sack on the thing. It's getting a rev counter, temp gauge and maybe an EGT, at the moment it has none of them. Whilst it might not mean an decrease in times, it'll teach me loads about set up that I can take to my 125.

[wobbly]

PS, if the jetting and ignition are perfect with a correctly set squish and you keep on getting a hot spot in front of the exhaust, then most likely
the stinger is too small and or there is insufficient cooling of the Exhaust duct.
I cured this in the KZ10 engines by allowing water thru slots right up to, and into the back of the bolt on flange spigot.

[philou]

Venturi flow meter for exhaust port. correction calculation blowdown sta

http://img4.hostingpics.net/pics/600515exhausttimeflowarea0320160812210850751.jpg

=> http://www.torqsoft.net/exhaust-time-flowarea.html

[wobbly]

I am REALLY interested in the flow method of checking actual port power capability.
And cant wait for you to show some results from this.
But as I have said before, lifting a cylinder only increases the Exhaust and Transfer STA but as in the example shown the Blowdown is actually reduced.
So how can we trust this result from the software unless its dyno proven.
Also what is the venturi connected to in the pic that gives the flow info i assume ?

[Flettner]

maybe" true" hcci is still a dream away, but maybe new ideas of better si combustion will come from the hcci challenge..... still interested why your hcci test engine suddenly screamed to high rpm before it died...:scratch:

I guess it went like this, compression is ignition, so if it stops running at higher rev's it must be running out of compression, or at least enough to initiate combustion. So as the revs climb the ability of the crank case pump drops off to a point where there is just not enough compression rise to set of combustion, so the rev's drop until the cycle can start again? Maybe? As for the high speed takeoff in the end I think by that time the little piston is hot enough to 'pick up the ignition' where the compression only left off. It would seem we might need to control the small piston temp? and / or keep the volumeric efficiency up at high speed. I'm sure a tuned pipe will help with this requirement.
I assuming the compression rise on my crude test engine is just enough to initiate combustion. I have a new version that will have much better control over the ignition compression rise.

[Ocean1]

I guess it went like this, compression is ignition, so if it stops running at higher rev's it must be running out of compression, or at least enough to initiate combustion. So as the revs climb the ability of the crank case pump drops off to a point where there is just not enough compression rise to set of combustion, so the rev's drop until the cycle can start again? Maybe? As for the high speed takeoff in the end I think by that time the little piston is hot enough to 'pick up the ignition' where the compression only left off. It would seem we might need to control the small piston temp? and / or keep the volumeric efficiency up at high speed. I'm sure a tuned pipe will help with this requirement.
I assuming the compression rise on my crude test engine is just enough to initiate combustion. I have a new version that will have much better control over the ignition compression rise.

I has a silly question. Is it possible that a spark plug initiated combustion event at some stage through the combustion process could increases pressure to the point where compression ignition immediately completes the job?

If so isn't it likely that there are existing engines that fall into that category?

And is that an effective way to manage the timing of the event so that it remains safely on the after tdc side, while offering most of the advantages of HCCI?

[marsheng]

Just in case this has not been posted before

Direct injection 2 Stroke

http://www.snowmobile.com/products/fuel-injection-systems-in-todays-twostroke-600s-1775.html

Some interesting piston shapes.

[Flettner]

I has a silly question. Is it possible that a spark plug initiated combustion event at some stage through the combustion process could increases pressure to the point where compression ignition immediately completes the job?

If so isn't it likely that there are existing engines that fall into that category?

And is that an effective way to manage the timing of the event so that it remains safely on the after tdc side, while offering most of the advantages of HCCI?

Absolutely, I think many engines fall into this category by accident. If Ryger had anything to believe, listen to the video of the cart running up and down the short road test. Even though the sound has been buggered up, it's quite obvious the the engine is struggling down low in the revs (worse than a standard engine I think), very retarded ignition timing. Assuming the high pressure crankcase pump has something to do with 'conditioning / homogenizing ' the fuel air ready for a quick burn event, compression is low and squish is minimal, then once the plug ignites the fuel air the pressure rise is such that it goes to self ignite condition shortly after, with a bit of luck just after TDC or there abouts. You are right I think.

Still tricky to control with a throttled engine.

[Ocean1]

Absolutely, I think many engines fall into this category by accident. If Ryger had anything to believe, listen to the video of the cart running up and down the short road test. Even though the sound has been buggered up, it's quite obvious the the engine is struggling down low in the revs (worse than a standard engine I think), very retarded ignition timing. Assuming the high pressure crankcase pump has something to do with 'conditioning / homogenizing ' the fuel air ready for a quick burn event, compression is low and squish is minimal, then once the plug ignites the fuel air the pressure rise is such that it goes to self ignite condition shortly after, with a bit of luck just after TDC or there abouts. You are right I think.

Still tricky to control with a throttled engine.

Be nice to have some actual numbers from some of the engines that've been built that made more power than expected. And yes, I can imagine the sound would be a giveaway.

What actual pressure are we talking, here, for ordinary petrol?

What would the above process mean for spark timing? Would need to stay at or about tdc right through the rev range wouldn't it?

And tricky in what way? Is your experience with run-aways from residual fuel in the crankcase/ports? If that's not easily resolved you'd be right back to direct injection wouldn't you?

[Frits Overmars]

I am REALLY interested in the flow method of checking actual port power capability.... But as I have said before, lifting a cylinder only increases the Exhaust and Transfer STA but as in the example shown the Blowdown is actually reduced. So how can we trust this result from the software unless its dyno proven.I too am really interested in this approach. You may recall that I proposed substituting the calculated flow areas by measured flow capacity numbers in EngMod.
Lifting a cylinder does reduce the blowdown angle area because it will increase the number of transfer timing degrees more than the number of exhaust timing degrees. The Torqsoft website quotes 0,00132 and 0,00130 respectively, a 1,5 % reduction, and that ties in with what I found, using their dimensions. But while their quoted exhaust timing values may be correct, their quoted transfer timing values are way off, so I too wonder how we can trust their software, though for a different reason.

[ief]

Other end of the spectrum but still, have to ask, any reason this portshape is as it is?

even the 'higher performance' cylinders have those and I wonder what benefit they could have?

(old school, 2 transfer ports barrel)

323858

[wobbly]

Assuming you are describing Aux Port shape ( or Hook Port as the Mericans call them ) the triangular shape used in a hi performance
cylinder is like that for a couple of reasons.
The top edge chordal width is greater than the duct width, but as this upper edge opens first the pressure differential is greatest and we get the maximum flow
ability in the upper 1/2 of the port opening, where the port area matches the duct area for maximum exit velocity.
As the piston moves down past the 1/2 height point, the Blowdown pressure is alot less, thus the flow rate reduces, so we dont need anywhere near as much area to keep up the flow needed.
Then there is the issue of vertical short circuiting from the A port window.
Only having the front corner down near the A port, reduces the tendency for the A ports flow column to do a U turn above the timing edge and exit thru the Aux port.
The same applies to the port linking area presented to the passing small end pin cavity.
The rear corner of the Aux port that is closest to the pin hole, has a much reduced area, and is well separated in distance from the A port, so there will be much less linking time area
thru the pin hole cavity.

Re the real port flow capability.
If we look at the raw numbers of the Aprilia in EngMod is would seem that the Transfer STA is excessive in relation to the Blowdown numbers.
But this is taking no account of the big radius on the timing edge of both the Ex and Aux ports.
Thus the effective Cd numbers for the Blowdown is much improved, and this is accounted for in the scavenging model that was presented in an SAE paper from I think the Uni of Valencia.

[ief]

No, it's the transfer, sorry :)

it's less pronounced then I drew it but still. And this is the opposite of ' tuned for max performance'

Tnx anyway for the aux port shape exlpanation, the more info the better :niceone:

You probably answered it allready with:

'As the piston moves down past the 1/2 height point, the Blowdown pressure is alot less, thus the flow rate reduces, so we dont need anywhere near as much area to keep up the flow needed.'

Would that mean that in this case flow in the transfers is kept higher to help in the lower revs giving up some sta for higher revs?

[Flettner]

Be nice to have some actual numbers from some of the engines that've been built that made more power than expected. And yes, I can imagine the sound would be a giveaway.

What actual pressure are we talking, here, for ordinary petrol?

What would the above process mean for spark timing? Would need to stay at or about tdc right through the rev range wouldn't it?

And tricky in what way? Is your experience with run-aways from residual fuel in the crankcase/ports? If that's not easily resolved you'd be right back to direct injection wouldn't you?

I think I was wrong, the HCCI engine did not run away due to residual fuel, I'm sure it's compression/heat (small piston heating up) related somehow.
HCCI opperation is a function of heat and pressure, which changes dramatically throughout the a normal engines running conditions/throttle settings. This would require a constant compression change to avoid detonation but still allow for HCCI combustion. Every crack of the throttle would change these conditions and need compression/timing adjustment. I guess doable.
I think with my test engine as it is, if I fitted a sparkplug as well (as Frits said) this would help with the conditions where the compression just falls off ie at high rpm where the crank case runs out of puff.
My engine was designed to raise the compression ratio to approx 21 to one if it were a full cylinder volume but with the exhaust port spilling out half before compression begins, I'm probably a few ratios short on compression in the real world, if you know what I mean:rolleyes:
My latest engine has a bigger combustion piston and a little longer stroke so quicker rise time. This engine at least has some control via the spray gun fueling system, I can modulate it's revs with the trigger although still hairy. I have a clutch fitted and it's ready to be hooked up to the out doors dyno when time permits.

[philou]

323858


it's the transfer,

?

usual, the delta transfert ports in the other direction

323860

323861

[wobbly]

The normal triangular max performance A port geometry is there to allow more room for the Aux, and to increase the wall area next to the main Exhaust to
prevent short circuiting.

[ken seeber]

Been thinking about HCCI a bit more. Seem that it is a part load thing only. One thought, say if you wanted 20 hp (under HCCI control because of the low emission and fuel consumption benefits) and your engine was 20 hp, then no go. Then give the engine to the WWW (Wobbly’s Wonderful World) and it comes back with 40 hp. So, could you then run the engine at its 20 hp part load point and then expect HCCI to kick in? Not likely.
After talking further to some ex Orbital cronies, it is clear that HCCI just needs temperature. In a 2 stroke, this can be accomplished with high levels of retained exh gas. In a 4 stroke, similarly using high levels of EGR. But, to get more power, amongst other things, the WWW crew strive to trap more fresh mixture in the cylinder at the time of exh port closure. The problem is that this is cool, not conducive for HCCI.
Dunno where this is going, but maybe HCCI could be promoted at higher load by being able to increase the gas temp after EPC. The big risk here is deto. Could be that Fletto’s auxiliary piston, that is phased early in the compression stroke, might be the go initiate HCCI prior to the conventional spark timing.

[peewee]

with triangle aux you can also drop the forward portion below the A transfer top but don't go so far as to break through the roof. a lot of cylinders especially older ones use a flat A roof so it will be easy to break through if you don't pay attention

[breezy]

Been thinking about HCCI a bit more. Seem that it is a part load thing only. One thought, say if you wanted 20 hp (under HCCI control because of the low emission and fuel consumption benefits) and your engine was 20 hp, then no go. Then give the engine to the WWW (Wobbly’s Wonderful World) and it comes back with 40 hp. So, could you then run the engine at its 20 hp part load point and then expect HCCI to kick in? Not likely.
After talking further to some ex Orbital cronies, it is clear that HCCI just needs temperature. In a 2 stroke, this can be accomplished with high levels of retained exh gas. In a 4 stroke, similarly using high levels of EGR. But, to get more power, amongst other things, the WWW crew strive to trap more fresh mixture in the cylinder at the time of exh port closure. The problem is that this is cool, not conducive for HCCI.
Dunno where this is going, but maybe HCCI could be promoted at higher load by being able to increase the gas temp after EPC. The big risk here is deto. Could be that Fletto’s auxiliary piston, that is phased early in the compression stroke, might be the go initiate HCCI prior to the conventional spark timing.

323869 picture of typical erg system,

[TZ350]

Page 1560 ......

http://www.highwaymanbikes.com/the-highwayman-f37-a-fully-custom-purpose-build-vintage-road-racer/

http://www.highwaymanbikes.com/design-and-construction-of-the-highwayman-f37-road-racing-chassis/

Not a Bucket but very interesting Vintage race bike build.

[Muciek]

Guys does anyone had luck using RGV carbs without solenoids? I wanted to use 34mm one in 125 engine, engine starts very well runs for about 2 minutes reaction for throttle is excellent but when the engine gets into working temperature it fouls a plug and You had to clean a sparkplug because engine dies. I have blocked air solenoids, it's weird and I don't know why it happens.

[Frits Overmars]

323869 picture of typical erg systemThat's a typical foul-stroke EGR system you are showing, Breezy.
Two-stroke EGR can be much simpler: just one exhaust port without auxiliaries. And then EGR does not mean Exhaust Gas Recirculation but Exhaust Gas Retention.
323926

[breezy]

That's a typical foul-stroke EGR system you are showing, Breezy.
Two-stroke EGR can be much simpler: just one exhaust port without auxiliaries. And then EGR does not mean Exhaust Gas Recycling but Exhaust Gas Retention.
323926

yes Frits, its a foul stroke diagram, but it shows a EGR set up, giving an inkling to the process .

so your picture shows a cylinder, single exhaust port... is the gas retained in the port itself? doesn’t this occur in 2 strokes already? how would you control the amount of heated gas and temp required to be fed back into the cylinder? :blink:

[Frits Overmars]

... your picture shows a cylinder, single exhaust port... is the gas retained in the port itself? doesn’t this occur in 2 strokes already? how would you control the amount of heated gas and temp required to be fed back into the cylinder?The exhaust gas is not fed back into the cylinder; it never leaves the cylinder because we make sure that there is not enough blowdown time.area to get rid of it all.
That is why I emphasized the absence of auxiliary exhaust ports that would otherwise increase the blowdown time.area. And yes, this occurs in two-strokes already.
The best-known control mechanism is the exhaust power valve used in the Honda Activated Radical combustion engine.
323927
But once you have established HCCI, you can also control it via the mixture strength. With HCCI you can make the mixture as lean as you wish and the fact that very lean mixtures are no longer spark-ignitable doesn't matter because they will still be compression-ignited as in a diesel.

[jamathi]

PS, if the jetting and ignition are perfect with a correctly set squish and you keep on getting a hot spot in front of the exhaust, then most likely
the stinger is too small and or there is insufficient cooling of the Exhaust duct.
I cured this in the KZ10 engines by allowing water thru slots right up to, and into the back of the bolt on flange spigot.

This picture makes me very happy Wobbly!
At Aprilia I was thinking about lengthening the exhaust duct 1 cm and then cool it very well.
It was in 2007.
This was not done because I retired.
Thank you for having the same idea, now I know it would have worked!

We were having a lot of deto problems in part throttle corners, about 30% throttle.
Is this also a problem in karting?
Because of this we could not use best power carburation on-track
And the gear-shifter would not work at high rpm, because the engine continued running without spark.
Probably HCCI
I had a switch fitted to the dyno, around 1999 to check this.
This was done because the riders complained about gear shifting problems, above all the 250's
The engine kept running without spark....
And without detonation.
So it looks like there was HCCI at full throttle, but not on small throttle openings.
The riders refused to chance gear in the 'old-fashioned' way.
But when Rossi went to the Honda 500/4 he had to do just this...

A problem I sometimes had on the dyno was that the engine sometimes would refuse to rev above 13000-13500
You could hear it coming, from the exhaust noise
Then it suddenly stopped running at all.
To resolve this I had to make a radius at the auxiliary ports, or make them inclined towards the main, so it looked like insufficient blowdown
But this usually cost some power....
Our exhaust ducts were CNC machined, and all cylinders flow tested.
Some cylinders had this problem, others did not.
I never really understood why this happened.

Once a mechanic brought back a spark plug from a race, the mass electrode had broken off.
But the engine had finished the race....
So I tried it on the dyno, and was amazed about how much more power there was!
That is until the ignition coil failed at around 13000....

[wobbly]

Having the duct 1cm length extension on the Aprilia would have made it exactly the length I have found works best ie 1.5X bore.
And in most engines this is way too short - as is the duct exit area way too big.
Using these length and cooling ideas, along with making the floor of the duct,going into the spigot, co-linear,with all of the oval to round transition angle in the roof
would have put your RSA close to 60 Hp.
All way to late now of course, but thanks to your help Jan , I will be able to use / test these and many more ideas with Franco at TM.

Here is the next idea i will be testing soon in the KZ10 , using an old Boyesen offset reed cage originally designed for a KTM.
I will be using " proper " reed petals, but from the testing I have done before on Jetski world champ engines this should be worth a couple of Hp in a 125

[peewee]

i present to you guys my machine shop. chinese drill press borrowed from the neighbor. :laugh::laugh:. got the pins in and ill attempt to weld the hole tomorow without melting off the edge of the piston

[peewee]

hey wob is that asymmetric valve for a engine that has a sharp kink at the carb/reed block like yami twins ?

[jamathi]

Wobbly

For CNC machining the exhaust duct we had separate programs for upside, downside and auxiliary ducts.
So we could 'mix' them.
First the auxiliaries were straight, later I made them slightly curved, which was a bit better.
This reduced exhaust duct volume a little bit.
I also had a cylinder cast with a much higher underside of the exhaust duct.
Just as high as the top of the transfer ports.
Only the top was CNC finished.
My intention was to see how high the underside could be made without losing power.
And to see if just the blowdown flow area would be sufficient!
But when I decided to retire I understood that the cylinder would not be plated before I left.
So it became machined with the 'normal' programme.
I still regret not having been able to do this test!
Raising the exhaust port underside 1,5mm and making it narrower at the sides had already given good results.

[teriks]

<SNIP>
My intention was to see how high the underside could be made without losing power.
And to see if just the blowdown flow area would be sufficient!
But when I decided to retire I understood that the cylinder would not be plated before I left.
So it became machined with the 'normal' programme.
I still regret not having been able to do this test!
Raising the exhaust port underside 1,5mm and making it narrower at the sides had already given good results.
How about, when you have raised the exhaust floor enough to loose power, you add a nice radius to promote flow, while maintaining the small duct area.
In a way that could give a good hint if the (potential) gains comes from the reduced area or the potentially reduced short circuiting.

[SwePatrick]

About HCCI ignition(i think)
I have built a new engine(not fully complete yet)
Test started it this weekend.

It´s an Kawasaki KX250 downstroked to 211.9cc(due to regulations in swedish dragracing)
However, i was so eager to hear the engine spin even though the pipe isn´t ready yet.
So i started it anyway.
And note, the exhaustvalves wasn´t in place, the guillotine therefor left a big hole downwards in exhaustport(no lid on either)

Engine started nicely but started to rev out of control almost directly.
Tried to stop it, pulled the cord to the stop button, nothing happened.
Placed hand onto the carburetor, nothing happened.
With hand still on carb and full throttle engine lowered the speed.
Had to shut off fuel to get it to stop.

Later, put back all exhaustports and started engine with no other adjustment.
It ran nicely on idle.

Quite interesting experiance ;)

I figure the exhaustpulses drew fresh air into cylinder through guillotineport.
And even though i had hand on carb it still drew fuel enough to get a burnable mixture.
But, interesting is that what i think it almost directly triggered HCCI.

Rgds.

Got the pipe from my friend today.
No silencer yet, so turn speakers down ;)
It distorts sound quite a bit as is.
But, a vid from today, just hade to rev some, to get positive vibes ;)

Click on link(should be working, it´s public):
https://www.facebook.com/patrick.wetterskog/videos/10154096572449475/

Kx250 -96 downstroked to 61.1mm stroke from 72mm
Maico 490 rod 137mm long.
Ported 200/138/138/138
Ported boyesen radvalve, redirected flow a bit so it aim´s for my big boyesenports in cylinder, and ported it to 42mm.
Keihin PWM 40mm
Own design on head, torus design, 15-1 compressionratio 0.8mm static squishclearence.

Later on, i will redesign radvavle some more and use a 44-46mm carb
Pipe is just a test to get a baseline, simple design in a simple program(but with some experiances included)

Rgds.

[shnaggs]

Here is the next idea i will be testing soon in the KZ10 , using an old Boyesen offset reed cage originally designed for a KTM.
I will be using " proper " reed petals, but from the testing I have done before on Jetski world champ engines this should be worth a couple of Hp in a 125

Wobbly, what does the offset reed cage provide? Wouldn't the one side of the valve be vary close to the inner runner, causing some shrouding and lack of flow?

[philou]

I tried assymetric reed valves to correct the inclination of the conduit for large shit minarelli am6 with very good results.

[breezy]

The exhaust gas is not fed back into the cylinder; it never leaves the cylinder because we make sure that there is not enough blowdown time.area to get rid of it all.
That is why I emphasized the absence of auxiliary exhaust ports that would otherwise increase the blowdown time.area. And yes, this occurs in two-strokes already.
The best-known control mechanism is the exhaust power valve used in the Honda Activated Radical combustion engine.
323927
But once you have established HCCI, you can also control it via the mixture strength. With HCCI you can make the mixture as lean as you wish and the fact that very lean mixtures are no longer spark-ignitable doesn't matter because they will still be compression-ignited as in a diesel.

thanks Frits, great source of information in the file, should keep me quiet for a while. ive got a 50cc motobecane for my test engine.. very poor porting... couldnt get it to fire up untill i removed the exhaust!!:violin:

[wobbly]

The engine that the asymmetric reed cage came from was a late model KTM250 and yes it had a very odd entry angle into the case.
In the KZ10 the factory has progressively straightened out the carb/manifold to get flow symmetric into the cage, and at the same time tilted the cylinder back
and the reed mount face downward - all to get incoming flow directed upward within the case toward the transfer entries.
Having the reed cage tilted, but with very good flow guides, will increase the upward tilt of the entering flow even more.
I will have to try all manner of varying petal stiffness and backup combinations to find what is best.
The centerline of the carb entry is offset vertically, as are the bolt mounting holes, so that there is no shrouding with all the petals at full lift.
I believe what is really needed though is a very small exit area from the reed cavity but with an extra pair of scalloped ducts down the reedbox/case sides to
promote the flow that comes out the sides of the reed cage - and maybe something like the reed cage pictured.
Better yet a VeeForce W cage, with double the reed tip curtain area - I have just recieved a pile of freeby parts from them to test in Italy.

Although its technically illegal in the KZ2 class engines I have welded the Ex port floor upward 3mm and filled in the bottom corner rads.
It "looks " identical " to stock, but makes around 1.5 Hp everywhere.
I believe that then radiusing the bottom edge would promote short circuiting flow at BDC so have not tried that idea.
Of course welding/filling in the duct to make the exit area way smaller would be very illegal and obvious - but if someone happened to scrape the duct port core
prior to casting at the factory - then the rule regarding " no added material " would not be broken - would it, he asks hopefully.

[teriks]

Although its technically illegal in the KZ2 class engines I have welded the Ex port floor upward 3mm and filled in the bottom corner rads.
It "looks " identical " to stock, but makes around 1.5 Hp everywhere.
I believe that then radiusing the bottom edge would promote short circuiting flow at BDC so have not tried that idea.
Of course welding/filling in the duct to make the exit area way smaller would be very illegal and obvious - but if someone happened to scrape the duct port core
prior to casting at the factory - then the rule regarding " no added material " would not be broken - would it, he asks hopefully.
Well, the radius idea might come in handy if you happen to scrape a bit too much of that duct core.
Of course its a shit load of work to test such feature, wish I had the means to do it myself..

[jfn2]

wobbly, which side is up and which side is down? Straight side up?

[peewee]

almost like that hole was never even there and suprisingly I didn't melt the corner off :clap: but I cant consider it successful until I see the engine run without piston failure

[jamathi]

How about, when you have raised the exhaust floor enough to loose power, you add a nice radius to promote flow, while maintaining the small duct area.
In a way that could give a good hint if the (potential) gains comes from the reduced area or the potentially reduced short circuiting.

That would certainly have been done.
With a higher exhaust port floor the ideas behind it were 2:

1 to reduce short circuiting, although a certain amount is necessary.
2 to be able to try wider A-ports.

[jamathi]

Well, the radius idea might come in handy if you happen to scrape a bit too much of that duct core.
Of course its a shit load of work to test such feature, wish I had the means to do it myself..

At Aprilia we made our own casting models, and core boxes.
But still scraping the cores was used, above all when I started working there.
And I started by boring out a STD ROTAX cylinder exhaust duct and fitting an insert which also worked well.
That was in 1995.
The STD ROTAX exhaust duct was really way too big, I think they still make their cylinders the same way.....

The place were the CNC machining was done was not far from us.
So sometimes I would test a cylinder on the dyno, then have it re-machined, and test it again.

When the auxiliary ducts were still a bit small I tried to raise the exhaust port underside.
The engine lost power, so it needed all the exhaust port surface for blowdown.

[Dutch Fisher]

And I started by boring out a STD ROTAX cylinder exhaust duct and fitting an insert which also worked well.



Jan did you bore out thru into the exhaust duct water channel and seal it back up with the insert?

[husaberg]

- but if someone happened to scrape the duct port core
prior to casting at the factory - then the rule regarding " no added material " would not be broken - would it, he asks hopefully.

if someone scraped the core, assuming they were that clumsy. Imagine If they inadvertently dipped some other parts in ceramic glue and it fell in some sand, well that would be unfortunate as well.:innocent:

[teriks]

That would certainly have been done.
With a higher exhaust port floor the ideas behind it were 2:

1 to reduce short circuiting, although a certain amount is necessary.
2 to be able to try wider A-ports.
Im thinking of one more potential benefit:
The smaller duct area should result in a longer column of fresh gas in the duct, this could reduce the thermal load on the piston a bit at lowish rpm, when the return pulse is too early.
Also you should get slightly less dilution of the fresh gas, if not for the longer column, but at least due to the increased difficulty of mixing fresh and exhaust gas in a narrow duct.

At Aprilia we made our own casting models, and core boxes.
But still scraping the cores was used, above all when I started working there.
And I started by boring out a STD ROTAX cylinder exhaust duct and fitting an insert which also worked well.
That was in 1995.
The STD ROTAX exhaust duct was really way too big, I think they still make their cylinders the same way.....

The place were the CNC machining was done was not far from us.
So sometimes I would test a cylinder on the dyno, then have it re-machined, and test it again.

When the auxiliary ducts were still a bit small I tried to raise the exhaust port underside.
The engine lost power, so it needed all the exhaust port surface for blowdown.
Could work quite well on my ring-less engines where one can make the exhaust port ridiculously wide then.

Thanks for great info Jan, as always!

//Thomas

[jonny quest]

High ex port floor help with less shortcircuiting, or perhaps better flow path for returning mixture?

On bridged ports, I've found power by widening bottom close to transfers

[Frits Overmars]

High ex port floor help with less shortcircuiting, or perhaps better flow path for returning mixture?Better blowdown outflow coefficient and stronger exhaust pulses due to smaller turbulence losses, less mixing of spent and fresh gases because of a smaller exhaust duct cross-section area where spent and fresh gases are in contact with each other, less short-circuiting, and a better flow coefficient for the returning mixture.

[wobbly]

Been a while that someone felt the need to ask me "which way is up ", im not telling, you will have to wait for the dyno results to be published.

[WilDun]

The best-known control mechanism is the exhaust power valve used in the Honda Activated Radical combustion engine....... once you have established HCCI, you can also control it via the mixture strength ........ the fact that very lean mixtures are no longer spark-ignitable doesn't matter because they will still be compression-ignited as in a diesel.

Having grown up on a farm I was aware that a diesel's "throttling" was done by controlling the amount of fuel coming in and was aware that petrol (gasoline?) should not be compressed to the high diesel compression figures - and of course the theory that to be more efficient an engine must breathe a cool charge, these theories now seem to have been blown right out of the water!

My questions are:-

1. Does it all mean that the good old "simple"carburettor will be back in favour (better for a fully homogenized charge?).

2. Does it mean that squish (and therefore squish clearance with it's inherent problems) is no longer necessary with HCCI?
In theory, could a thin disc (very thin biscuit like) combustion chamber formed by a flat top piston and the bore sealed off by a flat cylinder head be sufficient (simple description) and still achieve the high compression ratio necessary for HCCI?

3. Does a cool fresh charge no longer matter for cylinder filling? ie. in the case of HCCI.

4. Is it now necessary to have a bulky expansion chamber exhaust? seeing that as you say, the spent charge has not all actually left the cylinder and therefore I assume that none of the fresh charge will have gone either (to be pushed back in as in a normal high performance two stroke).

5. Or am I way off track - maybe I should just have stuck with farming? :msn-wink:

[Frits Overmars]

...petrol (gasoline?) should not be compressed to the high diesel compression figuresTwo things might happen if you put petrol in a diesel tank.
1: the temperature rise caused by the compression might not be sufficient to ignite the petrol/air mixture, so no combustion at all.
2: the temperature might be borderline; unlike diesel fuel that will start burning as soon as it is injected, a large amount of petrol may be injected in the combustion chamber before ignition begins, and then it begins with a head-removing bang.


1. Does it all mean that the good old "simple" carburettor will be back in favour (better for a fully homogenized charge?).I hope not. The drawback with pulsed injection is that not every bit of air gets a bit of fuel administered. In this respect a carburettor is better. But continuous injection is better still. I designed such a system for 35.000 rpm model engines for which it would be impossible anyway to find injectors that are fast enough.
It is one of the many projects that are still awaiting completion...


2. Does it mean that squish (and therefore squish clearance with it's inherent problems) is no longer necessary with HCCI?You're probably right about that, Will. Squish will no longer be required for flame spreading, though it may still contribute to homogenizing the fuel/air mixture.


In theory, could a thin disc (very thin biscuit like) combustion chamber formed by a flat top piston and the bore sealed off by a flat cylinder head be sufficient (simple description) and still achieve the high compression ratio necessary for HCCI?In theory that would be a yes. But it would yield an unfavourable volume/wall surface ratio, meaning big heat losses.
Anyway, the head shape also plays a role during scavenging so I'd stick with the present shape for now.


3. Does a cool fresh charge no longer matter for cylinder filling? ie. in the case of HCCI.It would seem so, wouldn't it? But the cooler the charge, the more mixture mass we get in the cylinder and that is what we need to make power.
It may mean that we will have to compress this cool mixture even more in order to achieve HCCI.


4. Is it now necessary to have a bulky expansion chamber exhaust? seeing that as you say, the spent charge has not all actually left the cylinder and therefore I assume that none of the fresh charge will have gone either (to be pushed back in as in a normal high performance two stroke).That bulky pipe can charge the cylinder with 1 bar overpressure (2 bar absolute) at exhaust closure. Without it we could not hope to make anything like decent power.
What I was trying to say is that with limited blowdown time.area not all spent charge has left the cylinder when scavenging starts, so fresh and spent charge mix, and the fresh charge gets heated. That won't impede it from washing through though.


5. Or am I way off track - maybe I should just have stuck with farming? :msn-wink:I'd say your dead on track Will. And it may seem like I've got all the answers, but HCCI is a new and partly virgin territory for all of us
(which makes me wonder: can there be such an animal as a partly virgin?).

[trevor amos]

Birthday congratulations and best wishes Frits, one more year of learning behind you!

[WilDun]

You're probably right about that, Will. Squish will no longer be required for flame spreading, though it may still contribute to homogenizing the fuel/air mixture.

In theory that would be a yes. But it would yield an unfavourable volume/wall surface ratio, meaning big heat losses.
Anyway, the head shape also plays a role during scavenging so I'd stick with the present shape for now.

What I was trying to say is that with limited blowdown time.area not all spent charge has left the cylinder when scavenging starts, so fresh and spent charge mix, and the fresh charge gets heated. That won't impede it from washing through though.

I'd say your dead on track Will. And it may seem like I've got all the answers, but HCCI is a new and partly virgin territory for all of us
(which makes me wonder: can there be such an animal as a partly virgin?).

Just dreaming up a scheme for a layout where the homogenising of the fresh charge is taken care of just as, or just before it enters the cylinder and with no actual compact combustion area needing to be scavenged as well, this would be a bonus.
Hopefully the layout I'm thinking of using would pretty well eliminate mixing of fresh and spent charges, but as you are talking a conventional two stroke layout (quite different to mine), we could end up talking at cross purposes here!
Most probably it will remain a dream.:rolleyes:

As for a partial Virgin ......... let's say that (in engine terms) if compression strokes occur, that might be an impossibility, but many people are led to believe that an exhaust stroke can take place without the need for a compression stroke to occur! (so a partial virgin?) - however, I have no desire to broach such a controversial subject! :no:

Oh, and happy birthday.

[Frits Overmars]

Thank you folks :drinknsin

... as you are talking a conventional two stroke layout (quite different to mine), we could end up talking at cross purposes here! Most probably it will remain a dream.I know the feeling Will. But you can do something about it: let us into your dream, and Flettner will take care of realization :yes:.

[ken seeber]

Frits, you young blokes are always having birthdays, but please enjoy another one with many more to come. And, as always, please continue your great contributions to kiwibiker and other forums.

[WilDun]

Thank you folks :drinknsin
I know the feeling Will. But you can do something about it: let us into your dream, and Flettner will take care of realization :yes:.

Yes, but a dream is only a dream and reality is something else and in order preserve my dignity I'll give it a go first to see if it actually works (even if it just runs in a mediocre way) then some of you guys can give it the once over and estimate it's worth!
However, if you don't hear about it again, don't hold your breath till it reappears, because either it didn't work or I've kicked the bucket! :rolleyes:

Impressed with the efforts of Flettner, Ken and the latest one from SwePatrick. :niceone:

So I'll go and at least try - sorry TZ - didn't really want to clog up your thread with bullshit! :facepalm:

[ief]

Another question pops up...

the 75 % resonance freq. of the membrane...

Remembered Wob saying the bigger the crankcase the thinner the reeds have to be...

So.... that 75 % ain't a rule but is in direct relation to crankcase volume (ratio)?

How would the real rule look than? :)

[wobbly]

In a sim the power continues to rise as the reeds are made thinner ( from being too thick ) , due to the petals resonant frequency coinciding with the forcing frequency of the intake tract.
BUT,as you drop the resonant rpm you are also effectively increasing the lift and petal open duration.
This very quickly runs into trouble at peak power and beyond,as the instant the petals hit a stop, or are not stiff enough to exhibit controlled drop back
onto the seat,they go completely spastic.
Easily seen in the sim as wildly varying tip lift ( and a big power drop ) with each sim iteration in turn.
One trace run will show a good result, the next trace the lift is all over the place.
Add a couple of 1/10 of a mm to the petal thickness and the resonant rpm will rise a few hundred, and the effect goes away in the top end.
This is exactly what the sim is for - to point you in the right direction with what to be trying on the dyno.
IMHO there are way to many variables involved to even begin to formulate a workable rule of thumb for reeds, as in reality, suck it and see is the only way.

I have just completed a huge number of sims for the KZ10 with all manner of different reed blocks, the only way to get a meaningful result was to set the petal thickness for every block
such that the 1st harmonic rpm was 10,000 with engines natural peak power at 13200 ( as in reality ).
This then shows the real effect of the reed block geometry on the power - not the differences due to the varying petal thickness - as this is easily changed during the subsequent dyno confirmation process.

[jonny quest]

Will it SIM a reed block with no reeds?

I know Frits or Jan have been talking about a reed block that basically opens up to a 360 intake as RPMS increase

[wobbly]

Frits friend Roland Holzer at Modena has tested this on a KZ2 engine with positive results, but no way would I believe it would be accepted by the CIK.
An adjustable PV mechanism isnt allowed so why would a moving spring loaded " thing " that allows the reed block faces to move apart be any different.
If you want to sim this specifically, ask Neels.

[Dutch Fisher]

Frits friend Roland Holzer at Modena has tested this on a KZ2 engine with positive results,


I must have missed the comparison dyno charts

Which page ?

[Frits Overmars]

Frits friend Roland Holzner at Modena has tested this on a KZ2 engine with positive results
I must have missed the comparison dyno charts.No worries Dutch, you missed nothing because there was nothing here to miss. I was never at liberty to post Roland's results; I only whispered in Wobbly's ear.

[TZ350]

Dr Evil does it, a F4 class legal water cooled 110cc engine.

324038 ...... 324040

Finally, after several weeks of detailed finishing work the Frankenstein Mr Bigglesworth 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.

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.

[lodgernz]

Sterling work Rob, can't wait to see (and hear) it going. Videos please...

[mr bucketracer]

good stuff rob , other real bucket build!

[FastFred]

:niceone:

Yes, a very traditional old school sort of Bucket build, a Frankenstein hodgepodge of bits all sown together, great work.

[SwePatrick]

Dr Evil does it, a F4 class legal water cooled 110cc engine.

324038 ...... 324040

Finally, after several weeks of detailed finishing work the Frankenstein Mr Bigglesworth 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.

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.


Nice! :niceone:

Next weekend will be first shakedown for my new engine(the downstroked kx250)
I feel that the gearing is a bit wrong, but maybe it´s me being heavy.
I´ve got a driver that is half my weight, hoping that will solve the problem ;)
However, the engine seems crisp and sound.
It revves like a 85cc mx bike :)

[peewee]

hey guys ive started the drawings for the outer wall templates like what I did on the inner walls. tomorrow I can transfer these to thin alum and start grinding. since the entrance is so small (ive done everything I can short of splitting the cases and welding the gasket surface wider) this is how they'll have to be shaped but there is still a small amount of converging as the passage goes up. in the end it should be far better than the original passages

[TZ350]

Nice! :niceone:

Next weekend will be first shakedown for my new engine(the downstroked kx250), the engine seems crisp and sound.
It revves like a 85cc mx bike :)

Thanks, and I look forward to some videos of the KX if you get to take a few.


hey guys ive started the drawings for the outer wall templates like what I did on the inner walls. tomorrow I can transfer these to thin alum and start grinding.

A great way of doing it, there are lots of interesting projects being worked on by people, I love it.

[Frits Overmars]

hey guys ive started the drawings for the outer wall templates like what I did on the inner walls. tomorrow I can transfer these to thin alum and start grinding. since the entrance is so small (ive done everything I can short of splitting the cases and welding the gasket surface wider) this is how they'll have to be shaped but there is still a small amount of converging as the passage goes up. in the end it should be far better than the original passagesHi Peewee, I see you've chosen different center point coordinates for the inner and outer radii. In order to achieve still more conversion you might try to move those centers even farther apart, like in this duct geometry of the Aprilia RSA125 A-transfer.
324052

[F5 Dave]

Should be interesting Rob. But I'd suggest you raise the seat so a human being can ride the bike. Well a European one over the age of twelve.

[Peter1962]

No worries Dutch, you missed nothing because there was nothing here to miss. I was never at liberty to post Roland's results; I only whispered in Wobbly's ear.

Frits, did the experiment at Modena let them draw conclusions or is the experiment still proceeding ? Do you forsee a practical use for this device in the future of 2 stroke competion engines ? Or is the rotary valve still the winning formula when ultimate power and a wide powerband + overrev is the goal ?

[Frits Overmars]

Frits, did the experiment at Modena let them draw conclusions or is the experiment still proceeding ? Do you forsee a practical use for this device in the future of 2 stroke competion engines ? Or is the rotary valve still the winning formula when ultimate power and a wide powerband + overrev is the goal ?Conclusions? Hell yes: 10% power gain and far better overrev.
Still proceeding? I doubt it. Like Wobbly said, there's no way that the CIK (the international karting governing body) will permit anything breaking new ground. Old farts, the lot of 'm.
Do I foresee a practical use? I would have to, wouldn't I? It's my 24/7-idea.

[peewee]

Hi Peewee, I see you've chosen different center point coordinates for the inner and outer radii. In order to achieve still more conversion you might try to move those centers even farther apart, like in this duct geometry of the Aprilia RSA125 A-transfer.
324052

frits im not sure what you meen by different center point coordinates but my passages cant be like the rsa because of the small passage entrance, which is dictated by the mating surface of the crankcase. ill get a photo so you can see the problem

the only easy thing I could of done was raise the bottom of the inner wall, where the bullnose corner is typically located. this may have allowed a more converging passage.

[Peter1962]

Conclusions? Hell yes: 10% power gain and far better overrev.
Still proceeding? I doubt it. Like Wobbly said, there's no way that the CIK (the international karting governing body) will permit anything breaking new ground. Old farts, the lot of 'm.
Do I foresee a practical use? I would have to, wouldn't I? It's my 24/7-idea.

Frits, there is 1 (one...) manufacturer that is still investing in 2 stroke technology, related to motorbikes : KTM. If this experiment gave proof of concept of the 24/7 induction principle, would this not be a great platform to build your device as an aftermarket solution ?
The number of 2 stroke MX and enduro bikes sold per year are in the thousands, this market is 10 times the total karting engine market. And it is the only 2 stroke competion where there are no retarded rules that inhibits all possible progress.
I do not know if Modena is active in other branches than karting, but with a sanctioning body like CIK we can forget all evolution in that particular branche of sport. Maybe a manufacturer like TM who are active in MX and enduro also would be interested ?

I mean, when was the last time that any manufacturer had an idea that gave their MX 250 cc a 10% gain in power, and gave a solution to the limiting factor of actual 2 stroke MX engines when compared to 250 4 strokes : too little overrev ?

[wobbly]

Peter, I agree that KTM ( and TM as well ) may be a viable end use for the 24/7 concept as they do build MX bikes, but the lack of " overev " in the 250 - 2T is limited by the
crank, not any particular tuning element like the reeds.
The 4T engines are very oversquare, and will rev to the moon with the pressure lubed big end - then it destroys a number of engine parts worth more than the whole bike to replace.
In the 2T the pipe/ports/undersquare crank are designed specifically to give a wide useable powerband that then drops off violently to prevent
sticking the needle roller big end thru the case.
The 72mm stroke used in all 250 - 2Ts will rev to 11,000 with a very limited race life.
The MX bike engines are all severely power limited past 10,000 to give an acceptable service interval.

[Peter1962]

Peter, I agree that KTM ( and TM as well ) may be a viable end use for the 24/7 concept as they do build MX bikes, but the lack of " overev " in the 250 - 2T is limited by the
crank, not any particular tuning element like the reeds.
The 4T engines are very oversquare, and will rev to the moon with the pressure lubed big end - then it destroys a number of engine parts worth more than the whole bike to replace.
In the 2T the pipe/ports/undersquare crank are designed specifically to give a wide useable powerband that then drops off violently to prevent
sticking the needle roller big end thru the case.
The 72mm stroke used in all 250 - 2Ts will rev to 11,000 with a very limited race life.
The MX bike engines are all severely power limited past 10,000 to give an acceptable service interval.

Wobbly, when tuning an MX 250 engine, is it possible to use better quality bearings so that the 10.000 rpm limit can be breached in a more safe way ? Or is it the crank itself that can not support these rpm's for a longer period ? When you are working with a ktm engine for kart use, do you retain the original crank ?

[wobbly]

The bearings used these days in 2T - MX cranks are all flat construction , silver plated cages, so the quality isnt the issue.
Its the inertial loads of stress reversal at BDC and TDC, and the inability of the cage to accelerate fast enough to prevent skidding ( instead of rolling )
by the needles.
Pressure fed, shell bearings, as used in a 4T dont have these issues, and the bottom ends are pretty bullet proof.
As I said, by giving up service life, the 72mm cranks can be spun to 11,000, but be prepared to change the big end VERY regularly.
I have changed just the cage/needles on a KZ2 crank 4 times with no issues as the rod and pin dont wear at all.
Its the cage scuffing that causes failures, no matter how much, or how good the oil used.

Gas Gas 250 engines used in kart road racing are 68mm square, and they are bullet proof at 11.000 - the normal MX crank are severely marginal.

[shnaggs]

The bearings used these days in 2T - MX cranks are all flat construction , silver plated cages, so the quality isnt the issue.
Its the inertial loads of stress reversal at BDC and TDC, and the inability of the cage to accelerate fast enough to prevent skidding ( instead of rolling )
by the needles.
Pressure fed, shell bearings, as used in a 4T dont have these issues, and the bottom ends are pretty bullet proof.
As I said, by giving up service life, the 72mm cranks can be spun to 11,000, but be prepared to change the big end VERY regularly.
I have changed just the cage/needles on a KZ2 crank 4 times with no issues as the rod and pin dont wear at all.
Its the cage scuffing that causes failures, no matter how much, or how good the oil used.

Gas Gas 250 engines used in kart road racing are 68mm square, and they are bullet proof at 11.000 - the normal MX crank are severely marginal.


Ski-doo's new 850 etec has pressure fed shell bearings.
Maybe this will trickle down to the MX world? Wishful thinking.

If the crank is the issue to the MX 250's rev limit, then can we tune the engine to produce more low-end, so the spread of power is more but just the other way, plus not have the over rev hit a brick wall?

I've seen the trombone pipe, but I have been thinking of another way to make a variable length pipe, but simplified. Will it work? Have no bloody idea...but it's fun to think about.

[shnaggs]

I have just completed a huge number of sims for the KZ10 with all manner of different reed blocks, the only way to get a meaningful result was to set the petal thickness for every block
such that the 1st harmonic rpm was 10,000 with engines natural peak power at 13200 ( as in reality ).
This then shows the real effect of the reed block geometry on the power - not the differences due to the varying petal thickness - as this is easily changed during the subsequent dyno confirmation process.

How did you come up the 10,000 harmonic rpm? Was that just the natural freq of the stock reeds, or was this an ideal freq that you determined?

[wobbly]

As I said before, if the reeds are too thin they loose control at peak rpm.
The KZ2 engines will run happily to 15000, and peak power is at 13,000 or so.
In the sim if I went 0.01mm thinner than 0.45 petal thickness on the stock cage ( the petals are actually 0.35,but have backups on top as well )
the power would drop dramatically past 14,000, where the tip lift started to go very weird.
When simming the Blaster/Banshee VF4 the petals needed to be at 0.3mm, and in both cases the 1st harmonic was at 11,000.
Sorry i said 10,000 before ( just checked ).
With the 1st harmonic set at 11,000 ( same case with the Boyesen asymmetric cage I simmed as well ) the petals were stable up to 15,000 when simming at that rpm.
So - run the reeds as thin as you can,with the thickness set by keeping tip lift under control at the peak rpm you will use when running.
And this will give you the best power at the lowest and highest rpms.
Reeds are a hugely complex area of tuning - and to write workable code for, as thin petals, by themselves are useless.
They flutter and go spastic very easily and you end up with big power losses and chipped tips in no time.
But with combinations of backup stiffness/length/shape and the use of rev plates, huge gains in power are just one more dyno run away ( he says after doing 3 days non stop
testing just that on SKUSA Honda CR125 ).

[Peter1962]

The bearings used these days in 2T - MX cranks are all flat construction , silver plated cages, so the quality isnt the issue.
Its the inertial loads of stress reversal at BDC and TDC, and the inability of the cage to accelerate fast enough to prevent skidding ( instead of rolling )
by the needles.
Pressure fed, shell bearings, as used in a 4T dont have these issues, and the bottom ends are pretty bullet proof.
As I said, by giving up service life, the 72mm cranks can be spun to 11,000, but be prepared to change the big end VERY regularly.
I have changed just the cage/needles on a KZ2 crank 4 times with no issues as the rod and pin dont wear at all.
Its the cage scuffing that causes failures, no matter how much, or how good the oil used.

Gas Gas 250 engines used in kart road racing are 68mm square, and they are bullet proof at 11.000 - the normal MX crank are severely marginal.


So -in theory- the WiWa GasGas 250 engine could be a solid base for modification to a tuned MX engine since it is bullet proof at high rpm's ? ( I was thinking for example in supermotard, where high rpm's are necessary). I know it has a balance shaft, which is a good thing. But what I do not know is if his cylinders have a power valve or not.
Wobbly, have you ever worked with this engine ? What would be your assesment ?

[wobbly]

I have only worked with the kart specific engine, that uses the quad cases as a basis and has a special cylinder casting.
The only down side I can see is that it has a T port, but makes very good power in this form for road racing use.

[2T Institute]

So -in theory- the WiWa GasGas 250 engine could be a solid base for modification to a tuned MX engine since it is bullet proof at high rpm's ? ( I was thinking for example in supermotard, where high rpm's are necessary). I know it has a balance shaft, which is a good thing. But what I do not know is if his cylinders have a power valve or not.
Wobbly, have you ever worked with this engine ? What would be your assesment ?

What makes you think that MX 250's are not revved to 10,500-11,000 on an MX track? Motard tracks are very tight usually top speeds are less than 120kmh. What kills the big end in a 250 National kart engine is the length of time spent at those RPMs.

[wobbly]

If you look at the dyno charts of all the usual 250 MX engines, they are miles over the pipe and make so little power past 10,000
I could see no point in reving there at all.

[Jvenni]

Assuming you are describing Aux Port shape ( or Hook Port as the Mericans call them ) the triangular shape used in a hi performance
cylinder is like that for a couple of reasons.
The top edge chordal width is greater than the duct width, but as this upper edge opens first the pressure differential is greatest and we get the maximum flow
ability in the upper 1/2 of the port opening, where the port area matches the duct area for maximum exit velocity.
As the piston moves down past the 1/2 height point, the Blowdown pressure is alot less, thus the flow rate reduces, so we dont need anywhere near as much area to keep up the flow needed.
Then there is the issue of vertical short circuiting from the A port window.
Only having the front corner down near the A port, reduces the tendency for the A ports flow column to do a U turn above the timing edge and exit thru the Aux port.
The same applies to the port linking area presented to the passing small end pin cavity.
The rear corner of the Aux port that is closest to the pin hole, has a much reduced area, and is well separated in distance from the A port, so there will be much less linking time area
thru the pin hole cavity.

Re the real port flow capability.
If we look at the raw numbers of the Aprilia in EngMod is would seem that the Transfer STA is excessive in relation to the Blowdown numbers.
But this is taking no account of the big radius on the timing edge of both the Ex and Aux ports.
Thus the effective Cd numbers for the Blowdown is much improved, and this is accounted for in the scavenging model that was presented in an SAE paper from I think the Uni of Valencia.


Hi all,

Very motivated by the results Wobby has shown I started to grind out the moons in the exhaust duct of the KZ10 cylinder.

During training on the track we saw a drop in exhaust temperature and a loss of overrev. ( Green line ) Out of corner we lost speed. First response was to lean out the engine but this didn't effect the EGT at all. Next step we changed the gear ratio ( shorter ). Temperature was ok, exit ok but we lost on top speed ( Yelloe line ) and a lot of overrev was there. The 'operating window'of this engine has changed to 12.000 to 14.200. Normally we gear within the range of 11.500 to 13.700 but there seems to be some kind of cooling effect within this range now.

As we have lost speed at time I trying to figure out what happend and what I could do to improve on low revs. Shoud I lower the cylinder or extend the exhaust pipe length by adding an insert at the exhaust duct ? Or buy a new cylinder :facepalm:..






324100.

[wobbly]

What ignition timing are you running - and what are the head cc.
Also do you have the short factory header manifold.

[Jvenni]

Thanks for replying.

The head cc is at the 13.2 cc ( 11.2 cc without plug hole ) and ignition is set at 1.55. We don't use the short outlet manifold yet but we removed the gasket between head and manifold. Inlet is with the factory short manifold

[wobbly]

Depending always on the track you need to try many combinations of pipe length and timing.
Less timing ( 1.2 ) = more egt and more overev power, this usually compromises the off corner drive ( but this is easily fixed with a 1/2 tooth on the back ).
Depending upon the fuel, you may find that even more timing ( 1.8 ) will give you plenty of bottom end, allowing slightly
taller gear ratio to gain the speed.
The short exhaust manifold also increases the overev power even more, but again what you gain on top you loose down low .
But with the correct combination, the short gearing and the ability to rev harder is always quicker.
Just changing the gear,and reving hard wont be fast unless the whole engine package is set to run that way.
You need to find the combo that works best for that particular track, and especially where the first 5 karts are maybe 2/10 apart, every tiny detail counts.
We regularly rev to 14,8000 with a ton of timing, a short pipe and run at 680*, but you will need really good reeds ( nothing like stock at all ) to get power up at that level.

What I dont understand is that even with the shorter gearing you are pulling way less rpm out of the hairpin,and way less corner speed, so of course it will be slow.
In that case the shorter gearing ( yellow ) should have the exit rpm way higher, and then accelerate faster - but its not,so something else is badly wrong

[diesel pig]

I am considing getting a set of straight cut primary gears made for a road going engine I want to turn into a road racing engine and since it would be quite an involved not to mention expense project.

I would like to ask some questions to clarify my understanding so I don’t make choices I regret later.
I notice factory road racers have slightly lower primary reduction ratios compere to dirt and road bikes for example a racer might have 3 to 1, and dirt & road 3.5 to 1, I thought this may because of the racers higher top speed (more power and better aerodynamics) the factories gave the racers slightly lower reduction ratios to avoid painting themselves into a corner as regards sprocket sizes e.g. stupidly large front sprockets and ridiculously small rear sprockets, is there any other reasons or advantages to making the gearbox spin faster?

This brings to my next question since the water pump on my engine runs off the crankshaft primary gear if I was to change the gearing I would have to change the water pump gear which got me thinking about changing the speed of the impeller as we know better cooling in a two stroke better power but would speeding up the impeller work? Or would I just end up over speeding the impeller and cause it to cavitate?

[wobbly]

The overall gear ratio from crank speed to rear wheel,to achieve the terminal speed you want is the overriding issue.
Of course a road race engine will be reving harder, so this will naturally mean top speed is increased.
Then the torque multiplication factor of the primary dictates how much load is on the clutch - lowering the ratio decreases the clutch load, and increases road speed.
But as power increases you will need usually more plate area or stronger springs, but less so if you have dropped the primary ratio.
Then as you mentioned there is the issue of sprocket sizes.
In general we usually want to be running a small front and rear sprocket combination to keep the chain run close to the swingarm - increasing anti squat.
Then you have to factor in the 1st gear ratio,by dropping the primary you may have an issue getting off the line.
Lastly is the water pump speed.
If you can, its way better to increase the impeller depth to shift more water without changing the speed,as this will be higher than stock anyway if the crank is spun harder.
I did this on the TZ400, with an 8mm wider impeller, using the stock pump gears, and it runs at 50*C in 30* heat - a stock TZ350 would be closer to 70*.
Many companies make uprated pumps for Banshee's and Boyesen make them for all manner of 4T bikes.
One last point is that there is very little difference in efficiency/power between straight cut and helical gears - 2 Hp in 80.
But a straight cut means no side load on the crank, so you can run a roller on the highly loaded gear side.

[marsheng]

We are busy playing with an Ignitech and a KR150. I see very little difference between the power runs between with the ignition set on 12 deg 16 and 20 deg btdc after 7500 rpm. Is the pipe or some other thing affecting the performance, or is it just at 20 deg there is more heat lost in the engine which dosen't really show any negative effects on a short dyno run?

Thanks Wallace.

[marsheng]

The Maico has got a new bad habit. It runs on full for 1/2 a second after WOT and then snapped closed. Bit confused as to where to look. It can't be sucking in that much air somewhere to keep it open on full. Seems to run correctly every where else.

Cheers Wallace.

[marsheng]

I am considing getting a set of straight cut primary gears made for a road going engine I want to turn into a road racing engine and since it would be quite an involved not to mention expense project.

I would have to change the water pump gear which got me thinking about changing the speed of the impeller as we know better cooling in a two stroke better power but would speeding up the impeller work?

My Maico gearbox range from 1st to 5th is 2.2: 1. Originally I had a 440 gearbox internals (I didn't realize I had the wrong set) which was a 3:1 ratio. It was really bad on the track. Gears just too far apart for the 250.

Note this is on a 5 speed 1980 250 but it gives you an idea.

The water pump really only needed a low speeds. Bikes only boil when in traffic or going up a monster hill with a 1 ton trailer.
Once on the open road, you could almost get away with thermosiphon.

See if you can find out what happened to this motor

http://www.kiwibiker.co.nz/forums/showthread.php/127584-Water-cooling-the-Buckethttp://www.kiwibiker.co.nz/forums/showthread.php/127584-Water-cooling-the-Bucket (http://www.kiwibiker.co.nz/forums/showthread.php/127584-Water-cooling-the-Bucket)

[wobbly]

" The water pump really only needed a low speeds. Bikes only boil when in traffic or going up a monster hill with a 1 ton trailer.
Once on the open road, you could almost get away with thermosiphon. "

Really - tell me then why every stock TZ350 I have ever seen runs over 70* - add an aftermarket thicker modern radiator and if you are lucky
it might get down to 60* on a cool day.
I had to completely change the water routing with a plate welded on top of the cylinder, then CNC an impeller 50% deeper to get the TZ400
down to 50* where it should be.

[JustHarry]

We are busy playing with an Ignitech and a KR150. I see very little difference between the power runs between with the ignition set on 12 deg 16 and 20 deg btdc after 7500 rpm. Is the pipe or some other thing affecting the performance, or is it just at 20 deg there is more heat lost in the engine which dosen't really show any negative effects on a short dyno run?

Thanks Wallace.

another not with the kr150
its using lots of water doing to dyno runs. and also pressurizing the overflow tank to the point where it is blowing a lot of water out... but only at round 7000rpm. round peak torque. i think the head gasket has slipped but is unusual that only blows through radiator at 7000rpm. is this a normal symptom of a slipped head gasket? or could the cylinder sleeve have moved causing a leak?

Cheers Harry

[marsheng]

Really - tell me then why every stock TZ350 I have ever seen runs over 70* - add an aftermarket thicker modern radiator and if you are lucky
it might get down to 60* on a cool day.
I had to completely change the water routing with a plate welded on top of the cylinder, then CNC an impeller 50% deeper to get the TZ400
down to 50* where it should be.

Is it a water pump issue or size of radiator issue? The 2 are to a large extent independent. The original question was about water pump. The pump with road going air flow through the radiator may well be sufficient.

[wobbly]

Anything making serious power needs a shit load of pump and radiator.
General rule is 1L/Min/Hp - and the RSW did 50L/min with the whole of the frontal area filled with radiator in an effort to keep it at 50*C.
No way would any TZ250/350 not boil instantly without a pump,no matter how fast the road speed.
A water cooled head only, is a special case off on a serious tangent - rejecting the head load transferred into the combustion
chamber of a Bucket is nothing like what is needed doing the whole cylinder of a highly tuned road race engine.
Like I said the 400 needed an impeller 50% bigger than the stock TZ350 to pull the temp down to a proper level, with as big a radiator as would fit,and
that just keeps to 50*C even doing 235Km/Hr in 20* weather.

[marsheng]

Anything making serious power needs a shit load of pump and radiator.
General rule is 1L/Min/Hp - and the RSW did 50L/min with the whole of the frontal area filled with radiator in an effort to keep it at 50*C.
No way would any TZ250/350 not boil instantly without a pump,no matter how fast the road speed.
A water cooled head only, is a special case off on a serious tangent - rejecting the head load transferred into the combustion
chamber of a Bucket is nothing like what is needed doing the whole cylinder of a highly tuned road race engine.
Like I said the 400 needed an impeller 50% bigger than the stock TZ350 to pull the temp down to a proper level, with as big a radiator as would fit,and
that just keeps to 50*C even doing 235Km/Hr in 20* weather.

Great info, thanks.

[oldjohnno]

I'm playing with a Rotax cylinder in a bike at the moment; the original engine had an angled duct that directed the header around the side of the single central downtube. The Rotax on the other hand has a duct that exits straight out from the bore in a plan view. The duct is 50mm long and 45mm diameter and there is about 70mm from the flange face to the back of the frame downtube.

A 45deg bend (about 1.5D radius) that starts immediately at the flange will clear the downtube, but will this affect performance badly (I'm aiming for about 10.5bar)? Or should I keep the header straight and use double downtubes instead?

[Frits Overmars]

I'm playing with a Rotax cylinder in a bike at the moment; the original engine had an angled duct that directed the header around the side of the single central downtube. The Rotax on the other hand has a duct that exits straight out from the bore in a plan view. The duct is 50mm long and 45mm diameter and there is about 70mm from the flange face to the back of the frame downtube. A 45deg bend (about 1.5D radius) that starts immediately at the flange will clear the downtube, but will this affect performance badly (I'm aiming for about 10.5bar)? Or should I keep the header straight and use double downtubes instead?A forked downtube could be a solution. Substituting the part of the downtube directly in front of the exhaust duct with a ring through which the exhaust header fits, would allow you to maintain the single downtube under the engine. Or maybe you can rotate the cylinder 180°.

[wobbly]

A bend close to the flange that is vertically up or down is nowhere near as bad as a sideways inclined one.
This give asymmetric plugging flow into the cylinder, and upsets the loop scavenging regime.
10 odd bar isnt really pushing the envelope, but if the rest of the setup is synergistic, the header bend may be just a small detraction.

[SwePatrick]

Thanks, and I look forward to some videos of the KX if you get to take a few.


Weekend have gone, but quite succesfull to be honest.
Started out just 'feeling' the machine on saturday, no spectacular.
But we saw a lot of potensial in theese runs.
Driver started way later than his opponent(just a qualifyrun) but almost passed him at the end, my driver had to pull the brakes due to promises that we just tested ;)

Video, mine is the one on the far lane, this run 9,27 on the eigth mile, bad start and heavy braking on the end, just 50mph trapspeed says a lot ;)
The clutch wasn´t good,, it jerked a lot and pulled the cycle forward, hard to stand still and concentrate on a good start.
https://www.facebook.com/patrick.wetterskog/videos/10154129881694475/

Sunday, bad weather was heading in, and no power in my camera,, bollocks!
But the track was rearranged to 150m instead of 201m(1/8 mile)
I decided not to touch any tune at all, infact, only thing i checked was sparkplug, nothing else.

Did four runs and best was 6.71 and 79.40mph trapspeed on the shorter track, still nothing was good.(2.077 60ft)
Wheelspin,, a lot!
Even on 2nd gear it was spinning hard.
Tried to heat up tire in an another run, this ended up in wheelspin in 1st gear and a long power wheelie on 2nd, driver had to shut off.
Even though we had problems and had to throttle it on the track this run was an 6.74 and 81Mph trapspeed.(2.403 60ft)

The other two runs was no good, was laying rubber about 150ft :)
One of theese runs had a better 60ft, 1.9xx something, but it was more like speedway than dragracing at 100ft marker so driver let off the throttle.(my drivers name is Filip)

Good things in weekend was,, pipe seems to be working, just a 5minute calculation job and 2-3 hour building process, not goodlooking, but prototypes don´t need to be goodlooking ;)
Quickshifter was dead on, needed no adjustment at all.
Engine seems to taking it with ease, never any signs of 'stressed out', overheating(was running it on Avgas 100ll) etc etc etc.
No leakage anywere, i just sat in pit talking bullshit to other guys when they were trying to fix their problems, quite nice :)

The best run:(hard to see)
https://scontent-arn2-1.xx.fbcdn.net/t31.0-8/14188100_10154132093809475_4391807452397799363_o.j pg

It says:
60ft 2.0768862
ET 6.7132968
Trapspeed 127,764(79.40mph)

[oldjohnno]

A bend close to the flange that is vertically up or down is nowhere near as bad as a sideways inclined one.
This give asymmetric plugging flow into the cylinder, and upsets the loop scavenging regime.
10 odd bar isnt really pushing the envelope, but if the rest of the setup is synergistic, the header bend may be just a small detraction.

Thanks Frits, Wob. The downtube can be changed fairly easily so I'll take that route.

[Lightbulb]

Anything making serious power needs a shit load of pump and radiator.
General rule is 1L/Min/Hp - and the RSW did 50L/min with the whole of the frontal area filled with radiator in an effort to keep it at 50*C.
No way would any TZ250/350 not boil instantly without a pump,no matter how fast the road speed.
A water cooled head only, is a special case off on a serious tangent - rejecting the head load transferred into the combustion
chamber of a Bucket is nothing like what is needed doing the whole cylinder of a highly tuned road race engine.
Like I said the 400 needed an impeller 50% bigger than the stock TZ350 to pull the temp down to a proper level, with as big a radiator as would fit,and
that just keeps to 50*C even doing 235Km/Hr in 20* weather.

That's great info their Wobbly. What is the total fluid volume for a RSW ?
How do I figure out the minimum volume of fluid required to cool a 4.5 to 5 hp engine that has to run for 90 seconds ?
You got me thinking overtime again, as if I were not over thinking too many things at the moment.
Neil L

[Frits Overmars]

That's great info their Wobbly. What is the total fluid volume for a RSW ?
How do I figure out the minimum volume of fluid required to cool a 4.5 to 5 hp engine that has to run for 90 seconds ?
I don't recall the coolant flow of the RSW125, only that it was less than in the RSA125 which pumped 60 liters per minute. The RSA125 used the impeller of the RSW250 twin!
For an RSA125 doing a 30 minutes race the 1 liter per hp per minute rule of thumb would work out at 1620 liters. That would be a bit much to carry around, but some clever mind came up with the idea of employing a radiator and recirculating the coolant.
Your 5 hp engine would need 7,5 liters over 90 seconds if the cooling system were total-loss (and then you wouldn't need a radiator at all) but the actual volume, determined by the volume of the radiator and the rest of the cooling system, would be about 3 liters, give or take.

[FastFred]

Anything making serious power needs a shit load of pump and radiator.


........................ :innocent: ... making serious hp, TZ had better get a bigger radiator.

[wobbly]

Yes Fred, all TZs need more/better rad.
What model are you talking, as I have a CAD file tor TZ350 50% bigger impeller and shaft as well.
Edit - Ha, reckon I misread what TZ you were referring to.

[2T Institute]

If you look at the dyno charts of all the usual 250 MX engines, they are miles over the pipe and make so little power past 10,000
I could see no point in reving there at all.

What about using the brakes while the bike is in the air?:msn-wink: It won't slow you down but will change the angle of the bike, same with the throttle.

[FastFred]

Edit - Ha, reckon I misread what TZ you were referring to.

Yes, true. I meant TeeZee but its interesting/helpfull to have heard about the water temp for a performance 2T and flow required, thanks.

[chrisc]

To ride, this bike feels exactly like the power curve suggests, challenging. It's been great for my riding though and what a challenge. Love it.
Red line is current set up, as received from Dave with a new ring fitted and the muffler repacked.
Blue line is Cully's RG50 with fairly stock cylinder and a few little things done to it. Rick's riding this at the moment.

324155

You'll notice the obvious brick wall in the power at 13,100 rpm. A 7.8hp ish drop in power over a few hundred RPM isn't exactly great over rev and I'm keen to see if I can get more of this back. It has enough peak power but needs to be more rideable.
We have a few area's to look into but suggestions on what might normally cause this would be great.

For a quick experiment, we tried running a 25mm long PVC tube on the end of the carb. No peak power was lost and about 0.5-1hp was gained in the mid range. No change to the over rev wall.

Records I got from Dave has the following for this engine:
Squish Clearance 0.90mm
Exhaust Timing ºatdc 81.5 =197
Transfer Timing ºatdc 115.5 =129

Here's a few laps on the local Mt Wellington kart track. I've since got a RS125 rev counter fitted along with the shift light (comes on 12,800rpm) and soon to have a temp gauge too.

https://www.youtube.com/watch?v=NrkBWogOjPQ

[F5 Dave]

Err, squish should be 0.5. Never got that high a reading on the dyno I use, but hadn't redone on that dyno since Sketchy reshaped the head.

Don't remember it falling off quite so steep, but certainly was never ideal there. Sub ex ports were left close to std size as this was done well before I'd seen a modern barrel with enormous sub's. That would have to help blowdown and overrev, but mean a replate.

[speedpro]

It's not the ignition killing it? That is so steep it almost looks deliberate, as in a limiter kicking in.

[F5 Dave]

Actually that'sworth checking, we messed around with a curve on sketches dyno but got no gain over a flat line, but we were like super pressed for time, Icould have used one of the MB files and that was only peaking at 12.
So it got put in the worry about it later file.


I never rode it after myself.

[CunninghamJames007]

For a quick experiment, we tried running a 25mm long PVC tube on the end of the carb. No peak power was lost and about 0.5-1hp was gained in the mid range. No change to the over rev wall.

If I could add my 2 cents' worth, I found a good article on designing openings for carburetors that may be of some use.
http://www.fxr150.co.nz/forum/showthread.php?1133-Carburetor-Bell-Mouth

[Jvenni]

Depending always on the track you need to try many combinations of pipe length and timing.
Less timing ( 1.2 ) = more egt and more overev power, this usually compromises the off corner drive ( but this is easily fixed with a 1/2 tooth on the back ).
Depending upon the fuel, you may find that even more timing ( 1.8 ) will give you plenty of bottom end, allowing slightly
taller gear ratio to gain the speed.
The short exhaust manifold also increases the overev power even more, but again what you gain on top you loose down low .
But with the correct combination, the short gearing and the ability to rev harder is always quicker.
Just changing the gear,and reving hard wont be fast unless the whole engine package is set to run that way.
You need to find the combo that works best for that particular track, and especially where the first 5 karts are maybe 2/10 apart, every tiny detail counts.
We regularly rev to 14,8000 with a ton of timing, a short pipe and run at 680*, but you will need really good reeds ( nothing like stock at all ) to get power up at that level.

What I dont understand is that even with the shorter gearing you are pulling way less rpm out of the hairpin,and way less corner speed, so of course it will be slow.
In that case the shorter gearing ( yellow ) should have the exit rpm way higher, and then accelerate faster - but its not,so something else is badly wrong


Thanks for answering !

we try to run as short as possible but the available grip at is also part of the puzzle. If i go too short we will lose time by having too much slip at corner exit. I adapt to make the turn tighter to settle more into the grip available. gives lower speed in the corner but at corner exit and straigth shorter gearing is certainly faster. Beeing in the rev area of 10700 makes the engine a bit tricky to handle on exit In race conditions we sometimes use a longer gearing to be more defensive at the long straight.

So if'm right we will lose some bottom end with the higher blowdown but we have to figure out how to win more at top ( and how to use it ) .We have checked the ignition timing and it was set a bit at the early site, next week we go to the next race track for training and try out what works best.

If I compare the pistons before and after grinding the moons, the piston is more clean at the exhaust site. This is also caused by the exhaust length / ignition timing not ok ? With this latest type of the engine we also have a lot ( need to clean it after every race weekend:eek5: ) of carbon build up at the exhaust site of the cylinder head. A nice perfect triangular starting from the spark plug towards the squish edge.
What has changed on this engine type is that the cylinder has less angle/more straight on the engine block 324166324167324168and the main transfer ports are made smaller. Maybe the booster port too strong ?

[Jvenni]

Thanks for answering !

we try to run as short as possible but the available grip at is also part of the puzzle. If i go too short we will lose time by having too much slip at corner exit. I adapt to make the turn tighter to settle more into the grip available. gives lower speed in the corner but at corner exit and straigth shorter gearing is certainly faster. Beeing in the rev area of 10700 makes the engine a bit tricky to handle on exit In race conditions we sometimes use a longer gearing to be more defensive at the long straight.

So if'm right we will lose some bottom end with the higher blowdown but we have to figure out how to win more at top ( and how to use it ) .We have checked the ignition timing and it was set a bit at the early site, next week we go to the next race track for training and try out what works best.

If I compare the pistons before and after grinding the moons, the piston is more clean at the exhaust site. This is also caused by the exhaust length / ignition timing not ok ? With this latest type of the engine we also have a lot ( need to clean it after every race weekend:eek5: ) of carbon build up at the exhaust site of the cylinder head. A nice perfect triangular starting from the spark plug towards the squish edge.
What has changed on this engine type is that the cylinder has less angle/more straight on the engine block 324166324167324168and the main transfer ports are made smaller. Maybe the booster port too strong ?

..The main port ducts are smaller..

[F5 Dave]

Actually that'sworth checking, we messed around with a curve on sketches dyno but got no gain over a flat line, but we were like super pressed for time, Icould have used one of the MB files and that was only peaking at 12.
So it got put in the worry about it later file.


I never rode it after myself.


hmm, no curve on this laptop & I set limiter at 14000.

[TZ350]

324253

Good things take time. That is Mr Bigglesworths front engine mount. Even with Chambers help with the welding it was a weeks worth of work. Took two nights to figure out what to do and another three to make it and get it so it slips on easily and the head can still be removed without any trouble.

324252

The gap is so that when the head nuts are pulled up, the selastic bushes on the cross member are loaded and take the weight of the motor.

324250324251324249

A lot of air just bypasses a flat radiator. To make a radiator efficient it needs some ducting to prevent the air from spilling around the sides.

It is hard to have much ducting on a Bucket, but a curved radiator should reduce spill of the sides.

324254

The pump is 25 l/min so a bit small. I had no idea what sort of water flow would be required but fortuitously Wob has just posted the answer, 1 L/min per hp. There is also one of Wob's thermostat arrangements for holding the motor at 45-50 deg C.

Hopefully get the radiator mounted and all plumbed up this week. I say hopefully because if a simple bracket can take a week .......

[peewee]

A lot of air just bypasses a flat radiator. To make a radiator efficient it needs some ducting to prevent the air from spilling around the sides.

.......

don't bother telling the sand sprinter guys in america this. they wont hear of it :laugh: . don't waste your breath explaining to them why the radiator shouldn't go directly in front of the aluminum fuel tank either

do you know about how far the ducting should protrude in front of the radiator to be affective ? 4" seems like it would do the job but I don't know. I was going to either get some thin aluminum plate and weld it together so basically there will be ducting on top/bottom and both sides of the rad. other Idea I had was use some type of thin plastic in the same way but the alum is probly a better way. I may use one of them small trailtech fans also http://www.trailtech.net/digital-gauges/tto/digital-fankit/732-fna1

[Frits Overmars]

do you know about how far the ducting should protrude in front of the radiator to be affective ? 4" seems like it would do the job but I don't know. I was going to either get some thin aluminum plate and weld it together so basically there will be ducting on top/bottom and both sides of the rad. other Idea I had was use some type of thin plastic in the same way but the alum is probly a better way.Use plastic. Aluminium sheet is twice as heavy and it cracks.

[manolis]

Hello all.


Quote from the post #23,190 of Frits Overmars (July 12, 2016):

“I had a pleasant exchange of thoughts with CITS-inventor Basil van Rooyen (picture) last year. I think I did comment on the CITS engine before, didn't I?”


I searched but failed to find anything. Any help?


In a couple of months it is to be granted the UK patent for the PatTwo engine:

http://www.pattakon.com/PatTwo/PatTwo11.gif

With a single piston and conventional kinematic mechanism it makes better what the CITS-engine tries to achieve with its two pistons (for more: http://www.pattakon.com/pattakonPatTwo.htm ).

Depending on the angular displacement of the “yellow” throttle valve, the engine “feels” as having from a quite small “crankcase dead volume” (the two spaces inside the piston are isolated) to a huge “crankcase dead volume” (the two spaces inside the piston communicate freely, i.e. as the piston moves towards its BDC there is no increase of the pressure in the space just under the piston crown).


Here is the “harmonic version” of the PatTwo:

http://www.pattakon.com/PatTwo/PatTwo_Harm1.gif

It doesn’t need other throttle valve than the “dark” throttle valve in the middle of the cylinder (that with the yellow” lever).

The crankcase can be isolated / sealed (“purple” separator) from the space(s) “under” the pistons.

In comparison to the CITS Vee engine wherein the total volume of the space underneath the two independent pistons cannot help vary during a crank rotation (FIG A, curve C):

http://www.pattakon.com/PatTwo/PatTwo_Volumes.gif

in the PatTwo the total volume underneath the piston(s) is constant (curve C in FIG B and FIG C).

Think what this means for the light loads and the idling (for instance, can the CITS operate without an external / additional throttle valve?)



Take the Harmonic PatTwo of the above animation and think what is the “crankcase compression”.

When the throttle valve is completely open (i.e. the two spaces, one under each piston, communicate freely), there is no “crankcase compression” (the ratio of the total “crankcase” volume to the dead volume of the “crankcase” is 1). It is like having an infinitely big crankcase in a conventional 2-stroke.

When the throttle valve is completely closed (no communication between the space under the one piston and the space under the other piston), the crankcase compression can get too high (it can get substantially higher than in any normal 2-stroke).

In the intermediate positions of the throttle valve, the actual “crankcase compression” appears something between the above two extreme values.

To make it simpler:
when with the throttle valve partially open the top piston crown moves towards its BDC with the transfer ports still closed, a part of the charge previously being into the space under the top piston crown passes to the space under the bottom piston crown so that, when the transfer ports open the quantity of the fresh charge under the top piston is reduced, etc, etc.


With the throttle valve completely open, the engine idles and the pumping loss is eliminated (like in the Atkinson - Miller cycle (Toyota PRIUS etc) in the 4-strokes).

As the throttle valve closes and the revs increase more and more power is provided .

When the throttle valve is completely closed and the revs substantially high, a local peak of power happens.

In case of tuned exhaust, the engine can provide even more power at even higher revs with the throttle valve completely open, i.e. as open as in the idling!
Follow the animation and think how this happens: a good part of the charge that enters into the top cylinder comes from the intake port of the bottom cylinder.


It may be confusing, but think how much it can change the way the 2-strokes operate.



As for the kinematic mechanism of the PatTwo Harmonic (you can see photos of it used in the PatRoVa rotary valve project at http://www.pattakon.com/pattakonPatRoVa.htm ), it achieves to give perfect balancing of all inertia forces, inertia moments and inertia torques; .in simple words, the Harmonic PatTwo is as vibration-free as the Wankel engine.


Thoughts?

Objections?

Thanks
Manolis Pattakos

[tjbw]

Hi Manolis

The only comment on CITS engine, that I recall, made reference to a Ryger patent.

[breezy]

hi Manolis, have you managed to knock up a working example yet?

[WilDun]

Hi Manolis

The only comment on CITS engine, that I recall, made reference to a Ryger patent.

I'm not really sure if the guys on this thread want it to be used for anything other than "real world" Bucket Race engine experiences, experiments and solutions etc.
I could be wrong of course - Maybe TZ could advise us or keep us straight here?

However it might be appropriate on the "Oddball Engines and Prototypes" thread. So I'll put a link to the CITS engine on there, (I've had that link for a long time and I think was already mentioned on that thread somewhere) .

Anyway what do you think TZ?

[manolis]

Hello Tjbw.

You write:
“The only comment on CITS engine, that I recall, made reference to a Ryger patent.”


For a long time I read about Ryger’s project / engine and about Ryger’s patent(s).
See in how many posts of this thread the Ryger project is mentioned.


In the patenting system there is a significant time limitation.
In 18 months from the first application for a patent the patent application has to be published (unless the applicant / inventor rejects it or unless he/she asks specifically for “non publication”; even in such a case, if a patent is eventually granted, it is obligatory to be published and to become available to everybody on earth.

The principle is simple:
the inventor takes the patent (which means the exclusivity in making and selling it for a 20 years period of time),
while the public has full access to every detail of the patent.


Asking for more details about Ryger’s project (in this and in other technical forums), nobody could (or was allowed) to provide them.

Unless I am wrong, till today there is no publication of a recent patent application (or of a patent) for a 2-stroke engine under the name of Hurry Ryger.


By the way, I asked (the question was actually for Frits Overmars) about the “pleasant exchange of thoughts with CITS-inventor Basil van Rooyen”
because Basil van Rooyen refused to respond to my messages.

Thanks
Manolis Pattakos

[manolis]

Hello Breesy.

You write:
“have you managed to knock up a working example yet?”

Not yet.

There are other projects of pattakon having, for the moment, higher priority.
It is also the fact that the PatTwo engine is a quite “fresh” project: it is less than 21 months old.

This is why I ask for the opinions and, preferably, for the objections of the experts in the 2-stroke engines.

Thanks
Manolis Pattakos

[manolis]

Hello WilDun.

You write:
“I'm not really sure if the guys on this thread want it to be used for anything other than "real world" Bucket Race engine experiences, experiments and solutions etc.
I could be wrong of course - Maybe TZ could advise us or keep us straight here?”


As I wrote to Breeze, there is not yet a working prototype.

However the PatTwo is a quite simple project.

http://www.pattakon.com/PatTwo/PatTwo10.gif

In the above animation the yellow “disk” throttle-valve is at the “open” position (in the animation in my previous post it was in the close position), the two spaces (above and below the separator) communicate, and the reed valve opens only for a small percentage of the time, i.e. the engine runs at partial load with quite small pumping loss.


Take a look at it and let me know how difficult it is to be done, i.e. to turn to a “real world” thing for Race engine experiences.

What I see looking at it, is just a longer piston with a separator/throttle valve inside it.
Way simpler than a sleeve liner project.
Maybe simpler than the modification of the radiator mentioned in post #23,483.

Make an estimation:
Starting with a conventional racing 2-stroke, how many days are required for the modification to PatTwo?
More than Two?


Think the new parameters that get into the play with the PatTwo design.
It is not about a small improvement, it is more about a breakthrough. Everything changes.


I understand it is “too unconventional” and spoils the way some member of this forum use to think. However they can simply omit / ignore such posts and proceed to the next ones.

On the other hand, everything used today for “"real world" Bucket Race engine experiences” (as you set it), was yesterday nothing more than a "promising" project.

Thanks
Manolis Pattakos

[JanBros]

http://www.dumpert.nl/mediabase/6872739/513eb652/zie_de_explosies_in_mijn_motor_2.0.html

[WilDun]

Hello WilDun.


As I wrote to Breeze, there is not yet a working prototype.

However the PatTwo is a quite simple project.


I understand it is “too unconventional” and spoils the way some member of this forum use to think. However they can simply omit / ignore such posts and proceed to the next ones.

On the other hand, everything used today for “"real world" Bucket Race engine experiences” (as you set it), was yesterday nothing more than a "promising" project.

Thanks
Manolis Pattakos

OK. Manolis, A word to the wise:-
I have no quarrel at all with your inventions, nor do I find them all that hard to understand (and I like them). but I only wanted to point you in a direction where they might be gratefully received and appreciated by many people without the chance of having to cross swords with anyone, but as I always say, I could be wrong!

If you press the "reply with quote" button in order to reply, then delete the surplus stuff (but leave the word "quote" inside the brackets at the beginning and the end of the part you want to quote - then it will save repeating everything in your answer and keep things tidy, (most of us tripped up on that one at the beginning).

I do still think it might be wise to go to the other relevant threads :msn-wink:

[Flettner]

Hello Manolis, what is your priority? Patent ideas so no one else can use them unless they pay you?
Patents are generally an amalgamation of other peoples ideas rearranged or in some cases just plain out stolen. Just be sure you are not here to take and not give, thankyou.
Fortunately (or perhaps unfortunately) people on this forum are only to happy to show off their ideas with not a thought as to financial gain. :shutup:

[WilDun]

Hello Manolis, what is your priority? :shutup:

:facepalm::rolleyes::laugh::killingme:.......:nice one:

[manolis]

Hello WilDun.

You write:
“If you press the "reply with quote" button in order to reply, then delete the surplus stuff (but leave the word "quote" inside the brackets at the beginning and the end of the part you want to quote - then it will save repeating everything in your answer and keep things tidy, (most of us tripped up on that one at the beginning).”

I know how to reply with quote.
However I prefer my own way.

Thanks
Manolis Pattakos

[manolis]

Hello Flettner.

You write:
“what is your priority? Patent ideas so no one else can use them unless they pay you?”


It is more than that.

In the last posts they were mentioned the names Harry Ryger and Basile van Rooyen.

First thing they did? They applied for a patent to protect their intellectual property.

A patent was granted to Basile van Rooyen (US8,683,964, April 1 2014, here is the link if you want to read it: http://patft.uspto.gov/netacgi/nph-Parser?Sect1=PTO1&Sect2=HITOFF&d=PALL&p=1&u=%2Fnetahtml%2FPTO%2Fsrchnum.htm&r=1&f=G&l=50&s1=8,683,964.PN.&OS=PN/8,683,964&RS=PN/8,683,964 ) for his CITS engine.

A patent is not yet granted to Harry Ryger who still keeps his project secret. Think why. I guess it is a way to protect his (intellectual) property.


Look how the patenting system works:

In his patent Basile van Rooyen defines exactly what his idea is, and what are the characteristics that distinguish his invention from the state-of-the-art. A specialized in the field examiner of the USPTO searched worldwide for relative documents and examined whether the invention complies with all necessary criteria in order a US-patent to be granted.

The granting of a patent means automatically two things:
1. the inventor has the exclusivity in making and selling his invention for some 20 years (it depends on the country),
2. the patent (which, by the way, has to provide all the necessary information for a skilled in the art to realize it) opens to the public.

Reading his patent and visiting his web site, one can learn several things.
And he can think different ways of realization to erase the limitations of the CITS engine.

The basic idea is good, but several of Basile van Rooyen’s limitations are unnecessary.

For instance, why to use a Vee engine when you can achieve better results with one only cylinder?

Why to apply the idea only on engines having even number of cylinders?

Why to have a fluctuating total volume under the two pistons, when you can achieve a really constant volume with fewer parts.

Why to have an additional external throttle valve for the control of the engine when with the inner throttle you can have it all?

Etc, etc.

This is the way the PatTwo project started.



And don’t think the PatTwo is bad for the CITS project and for Basile.

Quote from http://citsengine.com.au/investor-information/
“$4.0m is sought, to provide the funding of the final phase of the technology by world specialists, and for marketing the data by royalty agreements with the world’ s engine manufacturers, over a few years.”

He did not answer to my mesages, however I suppose that for one and a half years Basile van Rooyen knows that there is a competitor of his CITS engine and so he can protect himself and his investors from spending money (they say for some millions) for nothing..



But patenting (a great tool of the modern world, with its own limitations and weaknesses) is more than just protecting or making money.


Suppose you have an idea that seems good to you and you want a second “serious” opinion.
And that you are ready to pay for it.

First of all you have to write down / to draw your idea, to define what is your idea, at what it is better than the existing ones. It sounds simple. Ask those who tried it.

Then you apply for a patent, you pay the Application Fee and the Search and Examination Fees (230 pounds in the UK-IPO (United Kingdom patent office), US730$ for the USPTO (USA patent office)), and then you expect a highly specialized in the specific field Examiner (say a wizard in the specific field, the same for Honda, the same for GM, the same for VW, the same for an independent inventor) to look seriously at your idea / invention, to search everything already published and to certify about the novelty of your idea, about the industrial applicability of your idea and about having or not an inventive step your idea (i.e. about being non-obvious to the skilled in the art).

There is a big difference when you apply for a patent than when you ask for the opinion of the members of a technical forum like this.

In the first case you pay for a specific service and you demand serious Search and Examination.

In the second case anyone one can say anything, relative or not. See how many "strictly technical" replies there are so far.


So why I am asking here for opinions and objections?

Because there is always the hope that one member (just one is enough) will read and will understand and will respond with his true technical objections / thoughts. A second eye is, sometimes, invaluable.


By the way, it’s not so easy to take a patent in a serious patent office, especially for a “general” (i.e. not too much specialized) invention / idea.

For instance, take the PatRoVa rotary valve project of pattakon (more at http://www.pattakon.com/pattakonPatRoVa.htm ) which has a higher priority than the PatTwo project.

It is a rotary valve wherein the total force acting on the valve (no matter how high is the pressure into the combustion chamber) is permanently zero. It is a breakthrough. It changes the play. However only few really understand it, so far.


Sorry for the long post.
The hope is that some young engineers and mechanics will read it and will make questions to clarify anything they like.

Thanks
Manolis Pattakos

[WilDun]

Hello WilDun
I know how to reply with quote.
However I prefer my own way.

Thanks
Manolis Pattakos

Ok. - I think that statement says something.

[Flettner]

So Manolis, you will pay that one person on this forum that will help you make your millions with their advice? This is a "free for all" forum not an ideas mine.