ESE's works engine tuner

[DoldGuy]

Stock Rod 125mm, currently running a 133mm Rod with a spacer plate. Wobbly posted the need to run much leaner jetting (I believe 145 from 165), trying to understand the reasoning behind this, I have never had to go this lean before & ran out of jets before getting close, was concerned about that lean of jetting, but after searching here, hoping this could be normal. Again trying to understand the why part?


Doldguy

[TZ350]

Stock Rod 125mm, currently running a 133mm Rod with a spacer plate. Wobbly posted the need to run much leaner jetting (I believe 145 from 165), trying to understand the reasoning behind this, normal. Again trying to understand the why part? Doldguy

I would love to know too, and used this search term "" long rod site:https://www.kiwibiker.co.nz/forums/showthread.php/ ''" to turn up a whole lot of references to long rods on the ESE thread. I then got distracted reading something else that was interesting.

Enter all of this in Google to find references to long rods on the ESE thread :-

long rod site:https://www.kiwibiker.co.nz/forums/showthread.php/

[Peter1962]

I would love to know too, and used this search term "" long rod site:https://www.kiwibiker.co.nz/forums/showthread.php/ ''" to turn up a whole lot of references to long rods on the ESE thread. I then got distracted reading something else that was interesting.

Enter all of this in Google to find references to long rods on the ESE thread :-

long rod site:https://www.kiwibiker.co.nz/forums/showthread.php/

I think that the link is not correct... this just shows up the start of the ESE thread ?

[Frits Overmars]

long rod site:https://www.kiwibiker.co.nz/forums/showthread.php/

I think that the link is not correct... this just shows up the start of the ESE thread ?

So it wasn't just me; I think you're right Peter.

[F5 Dave]

Maybe he's drawing a long bow?

[TZ350]

long rod site:https://www.kiwibiker.co.nz/forums/showthread.php/ ... worked for me ...

Frits, many many thanks for a great artical ( and the previous 300 odd posts)

I have learned more in the last year reading posts from you, Wobbly and others than I have in the previous 50 years of 'playing' with two strokes.

I do not have much to offer to the discussion (apart from more questions!) but some may find this useful. Rather than use the site search which usually fails, use Google so to search this site use an ordinary search phrase and after it add

site:www.kiwibiker.co.nz

for example

Frits priceless site:www.kiwibiker.co.nz
or
Frits pisa site:www.kiwibiker.co.nz

the same will work for other sites with the appropriate site address

Mick

[DoldGuy]

Long rods that affect the case volume then influence the carb tuning dramatically as well.
I did a Rotax 257 single years ago for sprint kart racing, filling the crank webs with that UHWMP stuff.
This raised the case com form down near 1.3 up to about 1.35.
It needed complete rejetting and the main dropped from a 185 to a 165 due to the much stronger signal across the jets.
Going the other way on a 250 tandem twin by fitting long ( 120 ) rods and making full circle ( no pockets ) cranks, the jets then need to be huge
in size by comparison.
Honda used the short rod for years in the customer engines, but when push came to shove the final version used to win the last 250GP title used a long rod, for a reason obviously.
The big reed boxes that design had from day one, gave a relatively big case volume by default.

In my experience if a case reed is done as well as it can be ( look at a TM - KZ10 ) then there is very little difference in power if a cylinder reed
is also done properly with plenty of intake STA via piston cutouts and big Boyesens or floor ports.
The only real difference is that the boost port duct does not have a proper inner wall, and thus the flow regime is not as well controlled.

I finally found it...I had it backwards , requires richer jetting with the longer rod.

[DoldGuy]

Page 1370 ....












If you are looking for 2T tuning technical information I have found this thread is best read backwards, ie start at the last page and read back towards the beginning.





There are also over 7000 images on this thread, use "Thread Tools" to view them and then click through to the original post about them.





A lot of the decade pages have collections of quotes and links to other interesting things.


Page 1250 Links List
Page 1240 2T development Software, Port Theory, Interesting Sites
Page 1230 Compression Ratio, Ex duct shape and length, Fancy spark plugs.
Page 1220 Reed Valve Petals, Oxygen Sensors, Exhaust duct step at the pipe flange.
Page 1210 Ignition Trigger Woes, EngMod 2T and Blow-Down, Fuelling Curve.
Page 1200 Frits on power spread and the ratio of the maximum and minimum points in the power band.
Page 1190 No data, but a lot of talk about what the Ryger engine might look like.
Page 1180 Frits on 2T fuel consumption. M50 cylinder portmap and EngMod2T analysis.
Page 1170 Engine/Gearbox oils and bearings. Transfer duct shape and optimal Ex port timing.
Page 1160 Frits - Engines need large crankcase volumes, Power vis Handling.
Page 1150 Serious talk about crankcase volume.
Page 1140 Measuring the transfer duct length, Ignitec, Expansion chamber design, Trombone pipe.
Page 1130 Team GPR Edgecumbe Videos …. Cooling 2T’s …. 3xEx vis T port,
Page 1120 Crank Balancing, Ceramic Coating, Plugs, Piston Edge chamfers, RS125 pipe dimensions.
Page 1110 TeeZees progress on the EFI thing with the Beast.
Page 1100 No Data but some talk about pickups and EngMod 2T transducer position in the pipe.
Page 1090 Links about the Detonation Sensor and Temperature Data Logger.
Page 1080 No Data, the plenum is protested, Frits on Blowdown and Transfer window height.
Page 1070 Exhaust Duct shape, Kawasaki and BRC EFI dyno videos.
Page 1060 No Data but talk about Port shape and Flow in a duct on this page.
Page 1050 EngMod2T setup talk about pipes, transfer ports and the TubMax graph.
Page 1040 Basics of pipe design and how to influence where the point of maximum depression occurs.
Page 1030 Racing at Greymouth, its well worth a look to see Team GPR in action.
Page 1020 Pipe dimensions, Seattle Smittys hydroplanes. Husaburgs piston link.
Page 1010 Suspension Tuning.


Page 1000 has a lot of useful information and links. http://www.kiwibiker.co.nz/forums/sh...post1130773139








On Page 500, Bucket has links to how Team ESE built their 26, 28 and 31 hp engines:- http://www.kiwibiker.co.nz/forums/sh...-tuner/page500

TZ350

This page is what led me to LOTS of reading & Wobblys Post....

My search results have been miserable here & using google, I will try the way you posted next.

Thanks for the help!

[DoldGuy]

I first tried it on a 50 cc in 1074: more power.
Going from 80 to 85
Then at Aprilia in 1996: more power.
Without varying the crankcase volume.
We went from 112 to 113 and 115, later 118 was tried, still better.
For the RSA we had to lengthen the connecting rod from 115 to 120 to improve inlet flow: more power.
It is mainly due to piston friction I think.
NSU already found this in 1953, piston friction was the main source of friction in their 250 4-stroke engine.
It may be different for a reed valve engine, I have not much experience with these.
But the piston friction loss will, of course, be the same in a reed valve engine.

Of course at BDC there is no difference as you have to adjust the cylinder height!
Maybe it is interesting that with a longer connecting rod I could use higher transfer ports on my 50.
Getting still more power!

The crankcase volume also changes, of course, unless you change the position of the piston pin in the piston, as we did at Aprilia
This can be better or worse....
You can change your crankcase volume in many ways.
But always keep in mind that flow is more important than volume.....
On rotary valve engines I found the bigger the better, within reason of course....
The Aprilia engines had very narrow crank wheels, (16mm) so a very big crankcase volume. About 660cc in TDC
A big crankcase volume makes very long inlet timings necessary.
And big carburetors.

This is probably the reason why reed-valve engines need a smaller crankcase volume.
The reeds 'decide' for themselves when to open...
They need some depression.
And because maximum inlet flow is probably determined by the reed block, big carburetors won't work on a reed-valve engine.
They just slow down the flow in the carburetor, making for a difficult carburetor adjustment.

So I think that a rotary valve engine will always give about 3-4 HP more (125cc) than a reed valve engine.
Because of its unrestricted inlet flow and less pumping losses.

If the longer rod has consistently yielded more power, why have some manufacturers gone to shorter rods?

KTM used to use a 132 Rod with a 29.7 compression height piston, then a 129 Rod & now a 125 with a 38 compression height. I would think case volume (and cylinder height) would be the same on these motors based on these numbers. What would be positive about the shorter rod length?

[JanBros]

this search term "" long rod site:https://www.kiwibiker.co.nz/forums/showthread.php/ ''"

I think that the link is not correct... this just shows up the start of the ESE thread ?

you are not supposed to click on the link, you have to copy everything between "" ..... "" and paste that in google. that way google searches the term long rod only on Kiwibiker.

if you want to search something else, you simply change long rod in exhaust duct for exapmle, so you paste exhaust duct site:https://www.kiwibiker.co.nz/forums/showthread.php/ in google (everything that's underlined)

[TZ350]

you are not supposed to click on the link, you have to copy everything between "" ..... "" and paste that in google.

That way google searches only on Kiwibiker.

"" exhaust duct site:https://www.kiwibiker.co.nz/ "".... sure makes finding stuff on the ESE thread a breeze.

[wobbly]

The only thing to add re case volume is that a reed engine does not respond well at all to " going bigger " than around 1.3 ratio.
The bigger volume does have a positive effect, just as it does in a RV, but this is badly offset by the change in Helmholtz frequency,that then affects the reed
petals 1st natural resonance.
This requires thinner and thinner petals, to get the resonance working again correctly, and these thin petals ( or less backup pressure ) causes them to go spastic.
They hit the stops and rebound, or simply wave about all over the place with no control, and this creates havoc with power - on the dyno as well as in the sim.
You can see this happening in the sim, with huge differences in the reed lift profile, from iteration to iteration, and overall power drops.
This is why its very difficult to model reed stiffness correctly,you must "guess " the main petal thickness to take into account the backups stiffness/effectiveness.

[Vannik]

you are not supposed to click on the link, you have to copy everything between "" ..... "" and paste that in google. that way google searches the term long rod only on Kiwibiker.

I am constantly surprised to see how few people know about Google Advanced Search https://www.google.com/advanced_search which does it all for you.

[F5 Dave]

What is this bedevilry?!

[husaberg]

"" exhaust duct site:https://www.kiwibiker.co.nz/ "".... sure makes finding stuff on the ESE thread a breeze.

I used KB thread search , advanced option, single content and came up with these. for "Long rod" and Mr wobbly.
it took 1/2 second.............
make sure if you are looking for a particuilar phrase to include "" marks...
Otherwise you will find Mr wob uses the word long a rather lot of times.....

https://www.kiwibiker.co.nz/forums/s...post1130990445
https://www.kiwibiker.co.nz/forums/s...post1130990569
https://www.kiwibiker.co.nz/forums/s...post1130481748
https://www.kiwibiker.co.nz/forums/s...post1130481699

But using different terms in regards to case volume and jetting gives this which is i assume what he was wanting
https://www.kiwibiker.co.nz/forums/s...post1130478507

If you look at CCR in the context of what is accepted as being "normal", then the full range is generally accepted as being a low CCR at 1.3 and a very high CCR at 1.4.
This means a difference of 0.1 from "big" to "small", and the 50cc change in the case, represents 1/2 of the engines swept displacement by the piston in a 100cc bucket..
Aprilias latest engines are in the high 1.2s - and a very fast NZ champ 50 quad I built had 1.42, both on the very outer limits.
Changing from 1.4 to 1.3 would need huge jetting changes, like 4 mains, and this then affects the bsfc, and the pumping efficiency,needing a whole new approach to the transfer designs as well.
It goes on and on.
When you consider what happens when you change say the primary com from 13:1 up to 16:1,then this shows the relativity of the difference created.
But again - even the primary com change has huge effects that are not directly related to the numbers.
16:1 would need Avgas to stop deto obviously and this com would give great jump of the turns but would stop any pipe design from overeving.
Thus a high com engine needs a short pipe, or lots of retard, due to all the heat of combustion being released into the piston and the water - not the exhaust, making it appear longer to the engine. etc etc.
Change one element of a 2T and you are then looking at a whole raft of changes needed to optimise that setup,and it will never "work" if just one other element isnt synergistic with the rest.
And remember a general comment I made a while ago, about crap transfer ducting "liking" higher CCR ratios.