ESE's works engine tuner

[Gradella23]

But the 'just add a 42mm and change the pipe " scenario would make the engine useless.
Not only in karts where it would have insufficient front side , but in Roadracing where it would need the PWM PowerJet to enable ovrev potential
as the Port/Pipe combination would have to be biased toward front side ( so it had some ) and thus compromising high rpm power.
To make it work it has to have a Rotary Valve as well , and if that is going on its just a modernized RSA.

But let's Say you have a Roadracing Reed valve, with pj, programmable ignitions and all, there must be something to take advantage of from the last 10 years of progress in cylinders and crankcase beside the improved exhaust duct geometry and cooling.. or maybe It's just been too specific development of the kz regulations and we'd still be stuck with a finely tuned Honda rs like engine? I've heard that good old Gabriele Gnani has reach 55hp lately, no clue how tbh but he doesn't look like an "exaggerate takes" guy

[wobbly]

Yes we can use the developments of the last 10 years if dealing with a reed roadracing engine that has the PV , PJ ,ECU etc.
I have done a 96 4DP Yamaha , I fitted the last -20 cylinders from 99 ( last 56 bore ) and ground all the transfers to change mainly the A port radial and increase their STA
to match the bigger Aux port grinding.
Aftermarket carbon reeds and 40mm HV Lectrons - using the stock PJ solenoids from Yamaha.
With all the latest pipe trickery and programmable Ignitech ECU for the PV , PJ and advance , it made more power everywhere than any of the PVP ,FPA ,DEA Superkart engines had on the same DynoJet
and it made just over 100 RWHp on Avgas ( same fuel as the Rotary Valve engines ).
So I would have to say as the later Yamaha with square bore/stroke was light years ahead of the 4DP even in stock form from the factory , one of those would be easily up at 110 on that same Dynojet.

[Gradella23]

Yes we can use the developments of the last 10 years if dealing with a reed roadracing engine that has the PV , PJ ,ECU etc.
I have done a 96 4DP Yamaha , I fitted the last -20 cylinders from 99 ( last 56 bore ) and ground all the transfers to change mainly the A port radial and increase their STA
to match the bigger Aux port grinding.
Aftermarket carbon reeds and 40mm HV Lectrons - using the stock PJ solenoids from Yamaha.
With all the latest pipe trickery and programmable Ignitech ECU for the PV , PJ and advance , it made more power everywhere than any of the PVP ,FPA ,DEA Superkart engines had on the same DynoJet
and it made just over 100 RWHp on Avgas ( same fuel as the Rotary Valve engines ).
So I would have to say as the later Yamaha with square bore/stroke was light years ahead of the 4DP even in stock form from the factory , one of those would be easily up at 110 on that same Dynojet.

I don't know those engines, was the 4dp the One with 7 transfers? Did you reduce the A Port front Wall radial angle to get it more backwards? I'm usually considering something around 35° as the optimal... How much does a modern kz have?

[wobbly]

4DP was from 91 -99 with 7 transfers yes. The 96 G model ( I think ) A port front wall was 55* from the front to back CL and crossed at about bore center - crazy.
I angled it back to around 1/2 way from bore center to the boost face - still not as steep as the RSA for example.
Modern KZ cross around 1/3 from the boost face to the bore CL.

[41juergen]

4DP was from 91 -99 with 7 transfers yes. The 96 G model ( I think ) A port front wall was 55* from the front to back CL and crossed at about bore center - crazy.
I angled it back to around 1/2 way from bore center to the boost face - still not as steep as the RSA for example.
Modern KZ cross around 1/3 from the boost face to the bore CL.

Hey Wob at what rpm was this, approx. 12.500 - 13000rpm?
Btw: happy new year to all and a good start into 2024!
cheers
Juergen

[Gradella23]

4DP was from 91 -99 with 7 transfers yes. The 96 G model ( I think ) A port front wall was 55* from the front to back CL and crossed at about bore center - crazy.
I angled it back to around 1/2 way from bore center to the boost face - still not as steep as the RSA for example.
Modern KZ cross around 1/3 from the boost face to the bore CL.

Interesting. So the trend is still to aim the A port front wall steeper, like also Jan said sometimes.
And doing so i imagine it becomes not profitable to make the B port front wall intersect CL at the same point (as i thought was some sort of a standard), as combining this with the hook of the rear wall will give too small of an effective cross area. Or am I missing something?
I guess they use something like the yellow line for the B front, right?

[Frits Overmars]

Interesting. So the trend is still to aim the A port front wall steeper, like also Jan said sometimes.
And doing so i imagine it becomes not profitable to make the B port front wall intersect CL at the same point (as i thought was some sort of a standard), as combining this with the hook of the rear wall will give too small of an effective cross area. Or am I missing something?
I guess they use something like the yellow line for the B front, right?

Here you go Gradella.

[Gradella23]

Here you go Gradella.

exactly what i was thinking of, Frits. I used plenty of your concepts on my 50cc cylinder, so thanks!

[wobbly]

I made the front and rear walls of the A port cross the centerline at the same point in the 4DP - but this was just improving on " old " scavenging in the 90's from Yamaha.
They then got a Czech anemometric flow visualizing CNC machine and it all changed in 2000 when they went 5 port + T port , and the same scavenging regime as the Aprilia.
That is all but the B port front wall coincide on the center line @ 18% of bore - as Frits diagram shows.
Suddenly Yamaha had swallowed corporate pride , built a RS250 cylinder with Aprilia scavenging - except they kept normal stagger , and absolutely smashed the 250 class by taking 1st and 2nd with ease.

The idea behind all this is the flow column from each port may connect to the same radial coincident point on the bore CL but they are all separated axially.
In this scavenging regime the A port is entering Frits's " Pisa Tower " in the middle , the B ports are colliding with each other underneath that , and the C port is at the highest point , angled well upward
and pulling the column toward the wall above the boost port ( a sort of stratified charge process as used in direct injection technology ).
Thus the rising loop column " leans " away from the Exhaust port , reducing short circuiting , and making it U bend completely across the combustion chamber , increasing the scavenging of Exhaust residuals.

Nowadays the only variable to consider is what scavenging regime to use , reverse stagger or normal , and that is determined by the presence of a PV , or not.
Plus with no PV we need even more bias toward front side power and this entails the exact reverse of what all the old SOTA said was needed , slightly less rearward port radial angle.

EDIT - the 4DP made max power @ 12450 , the PJ switched @ 12650 and it rev'd easily to 13500. I tried the pipe a little shorter but there was less power under the curve - so much for Yamaha being so obsessed with
the short stroke to allow higher revs, it didnt.

[41juergen]

Got it Wob, thanks! One other question, have you merged the B and the C port to one?
RE the RS250 bridged exhaust port: there is a rumor that this was the idea from Guy Coulon at that time (copping the 500ccm design) as the TZ production racer had a triple exduct design..and the last version (TZ250 5KE4) had/has additionally a resonance chamber (as the Honda ATAC system) .minimizing the power dip between 7000 and 8000 rpm.

[a.montani]

Looking at the picture I noticed a knocking sensor. I am interested to detect knocking on a kart engine.
On the net I found Bylund automotive knocking shield. This shiel is using Arduino uno board.
below the link. do you have experience on this equipment?
what is the system (electronic) used to manage the knocking sensor in the picture on KZ cylinder head?
Thanks in advance for your help.

https://www.bylund-automotive.com/st...-2-for-arduino

[wobbly]

I have used for years the Czech made deto amplifier that outputs a 0-5V logger signal available on Ebay.
It can also have a ground wire added to interface with an Ignitech unit to retard the ignition when deto is seen.
Cheap , reliable and uses a standard Bosch sensor with 8mm thru hole available new or from car wreakers from BMW/VW/Benz etc.

https://www.ebay.com/itm/18573910441...Bk9SR47GtdigYg

[Peter1962]

Got it Wob, thanks! One other question, have you merged the B and the C port to one?
RE the RS250 bridged exhaust port: there is a rumor that this was the idea from Guy Coulon at that time (copping the 500ccm design) as the TZ production racer had a triple exduct design..and the last version (TZ250 5KE4) had/has additionally a resonance chamber (as the Honda ATAC system) .minimizing the power dip between 7000 and 8000 rpm.

I am not sure if it was over here, or on the pit-lane.biz forum but one of our most esteemed members already pointed out that the 'sudden' change by yamaha was seriously inspired by an illegal copy of a honda cylinder made by a mechanic with less than loyalty to his employer.

[wobbly]

Yamaha had seen the results gained by Harold Bartol who made his own version of a Honda style cylinder using the Czech made CNC anemometric flow visualization machine.
He was running Yamaha's 125GP program that was embarrassingly slow , but even though his cylinder was designed to fit directly onto the Yamaha case he was not allowed to use his stuff on the factory bike.
He showed me the dyno sheets of his cylinder against Yamaha's best in the pits at Philip Island , and he was far , far advanced over what they were capable of.

I had a plastic 3D printed cylinder for the BSL500 made and sent it to him for analysis , and it came back with alot of epoxy and grinding done.
Those changes were immediately incorporated into the models for the first 3D laser sintered alloy cylinders ever manufactured.
All the lessons learned by Bartol later ended up on the KTM250GP parralel twin , and Yamaha finally saw the light and ended up with pretty much what Bartol had developed.

[SwePatrick]

Part one(forced) dynosession of me and my friends Piaggio Roost twin.

To obvious reasons in this video it needed to be a two part video