ESE's works engine tuner

[SwePatrick]

YES!!!
Finally!

I finally managed to make a couple of testdrives to sort out small stuff on the Kawasaki overkill bike.
This is an old Kawasaki KX250 -96 engine with a LOT of mods done to it.

And i am all in all positivly impressed so far, it keeps somewhat together *lol*
I have only scratched the surface powerwise, i keep it 'safe' while sorting out bugs.
So far it has dynoed 67whp at 9500rpm.
I figure there are at least 5 more lurking in it.(check sparkplug in the end of video)


Setup:
Kawasaki KX250 1996 engine.
Mixmatch between years to get closest ratio gearbox.
TM racing cylinder, ported and turned 180 degrees, exhaust facing backwards
Billet head 15.5-1 compression
KTM woessner piston
Maico 490 rod
Lockup clutch(home made)
Rotary intake disc(home made, from Rotax parts)
42mm Keihin PWM
Balance shaft from Kawasaki Tecate.
Ignitech DCCDIP
Pipe made by me.

So,, for you to enjoy:

[diesel pig]

An interesting Bucket project in Wellington
https://www.youtube.com/watch?v=dbQpYDBawEA

Having watched the video. I like they are not trying to reinvent the wheel and are using a Yamaha gearbox and all ready designed cylinders that are all ready good to go.

[Condyn]

Re cones.
A program called cone layout can be used as well. It is far less costly than anything else I have found. Unfortunately you need to add one material thickness to your diameters to make them correct. WS exhaust designer is intriguing, however I cannot read German and have not had time to translate the website information. I believe it is a subscription service as well which is…… blah

[wobbly]

Yea , at $600 USD/year you would have to be doing full time pipe building to justify that, way better to spend that money on EngMod as a one time cost so you can design optimized pipe and port geometry
and see the results on Hp without building anything.

[F5 Dave]

At USD600 a year, I'd want them to build the pipes and supply the materials.

They could live in the garden shed and eat what they could forage from the neighbouring gardens. And would learn the true meaning of Discipline.

Sorry. Got carried away.

[katinas]

Off topic, an interesting Honda decision to integrate chain driving balancer crescent on the primary gearbox shaft of the CB 250. Has a similar scheme been used on other models?

[wobbly]

Not that I would ever presume to doubt Honda's balancing ability , when you look at the genius V5 , not so much the old 250 triple road bike, but
as the clutch primary reduction in most bikes is about 3:1 down - then that out of balance forces vector seems to bear no relationship to any forces generated at the crank.
Unless the chain drives just the balance mass at 1:1 on one end of the primary shaft , and the other end is driven by the clutch gear reduction.

[husaberg]

Off topic, an interesting Honda decision to integrate chain driving balancer crescent on the primary gearbox shaft of the CB 250. Has a similar scheme been used on other models?

Not that I would ever presume to doubt Honda's balancing ability , when you look at the genius V5 , not so much the old 250 triple road bike, but
as the clutch primary reduction in most bikes is about 3:1 down - then that out of balance forces vector seems to bear no relationship to any forces generated at the crank.
Unless the chain drives just the balance mass at 1:1 on one end of the primary shaft , and the other end is driven by the clutch gear reduction.

with that chain there I am assuming they dove it from there and used the shaft just to support it?
The CB250N def had twin chain balance shafts but diferent than that?


I don't recall many Hondas having outrigger counter shaft bearing, so what looks like a countershaft sprocket I assume is the drive

oddly I cant find that set up in the CB250N?





Edit found it it the CB250RS based on the XL/XR 250 the third gen after s motor but before RFVC 80-83 ish

they just use the shaft

[jato]

i was wondering about how the balance shafts were run counter to the engine (with a chain drive) then realised the chain only runs on one side of the crank sprocket...

[husaberg]

i was wondering about how the balance shafts were run counter to the engine (with a chain drive) then realised the chain only runs on one side of the crank sprocket...

Yes


you can do the same with a double sided belt.
I was going to build a single with a belt primary and drive a balance shaft off the outside.



but to be honest a geared set up like the CRF150r with the water pump off the same shaft is neater. but harder to do with a Disc valve.
I wanted to use a belt as I was confident could get the gears centers right, the same reason the poms likely used chain primaries.

[Rudex]

There is one program called " Plate 'n' Sheet Professional " it works ok.

Regards

Yea , at $600 USD/year you would have to be doing full time pipe building to justify that, way better to spend that money on EngMod as a one time cost so you can design optimized pipe and port geometry
and see the results on Hp without building anything.

[Niels Abildgaard]

Yea , at $600 USD/year you would have to be doing full time pipe building to justify that, way better to spend that money on EngMod as a one time cost so you can design optimized pipe and port geometry
and see the results on Hp without building anything.

How well can Engmod predict a well developed 125ccm (Aprlia) in three different power situations?

[wobbly]

The RSW/RSA is very close but suffers in that there is no way of simulating the large timing radius on the Main Exhaust.
And the " real " timing of that hugely affects the sim output - if you look at the raw numbers it would seem the STA of the Transfers is about 10% better than the Exhaust port, but the radius increases the exit Cd
to very cleverly match the transfer actual flow numbers.
The RS125 road type engine is easy, and very accurate.

[jonny quest]

Transfer stagger

Honda incorporated a higher A port

RSA higher B port. I going to assume the RSA wanted a little more transfer area, if the A was raised... too much cross talk with exhaust port. So the stagger really wasn't important, just the logistics of the ports.

What made Honda work with raised A? Was it a bridged ex port that liked it?

Do the first opening transfers really not flow yet because of cylinder pressure? Is it only above a certain RPM ? Or wave tuning when pipe is working?

What about putting a powervalve into the mix? Some of these powervalve's when closed are the height of the transfers, or even lower!

I'm working on a 250cc single, CR250 triple port. I had to lower cylinder 1mm to get side exhausts lower than main port. Main port was raised .8mm.

MX application, motor needed more bottom. It gained 2hp down low, lost 2hp on top.

Going to start modifying transfers now... but don't have anymore room for error to lower cylinder if they get too high.

Now tro

[wobbly]

Transfer stagger " works " simply due to the fact that at TPO there is way more blowdown pressure pressure above the port timing edge than there is case pressure
in the ducts created by the dropping piston.
Thus there is reverse and then stalled initial flow down the duct that is opened first.
In the case of Honda using normal stagger with the A highest , this is created due to the fact that the T port outer extremities are much smaller in height than the Aux ports in a 3 port cylinder.
Thus Honda used as much A port height as they could to achieve the maximum Transfer STA within the vertical space available.

With a 3 port regime, to achieve the maximum Blowdown STA , the Aux have to be very deep , and this limits the timing height the A port can be lifted to.
Also limiting the A port height reduces the vertical short circuiting from the A into the Aux at low Transfer velocities, early in the cycle.

The added B and C chordal width total is much greater than the A alone, thus lifting that whole wider width, achieves a much higher total Transfer STA than can be achieved using normal stagger.
Lastly the natural scavenging regime of low A port reverse stagger, favors upper front side/peak and overev power.
Normal stagger scavenging that boosts the whole front side, is always used in wide band applications such as MX or more especially where there is no PV to help front side power.

I tested the two differing approaches in a KZ race engine, where I lowered a stock normal stagger engine , then ground up all the ports to replicate the Aprilia regime.
In EngMod and then on the dyno it showed a loss of around 3 Hp at 10,000 ( the usual lowest rpm on track ) and then gained around 2 Hp ( in 50 ) at the peak of 13800.
But it made an amazing 8 Hp more at 14600 - close to the max the rpm down the shute.
This setup went from 140 Km/Hr at our fastest track to an easy 145, but the serious lack of acceleration off the two slowest 2nd gear corners meant an average drop in lap time of 3/10 sec
even with shorter gearing ratios.
With a PV and a digital ignition if allowed , this reverse stagger setup would have been way faster.