ESE's works engine tuner

[HenkS]

Frits makes the assumption we all know the measurements are chordal , its like trying to convince a cop the 100 sign on the side of the road you thought were mph as opposed to kmh.
And he has tried to give a guide for all bore sizes , we all know small bores down at 40mm are a special case and will tolerate more than 70% with ease , but anything with R200 and more than 70% would have
to have huge corner rads , but then its already well departed from anything approaching the mechanically possible " optimal " Blowdown geometry.

Cordurally measuring the width is logical and easy to do. But how are you going to measure the top and bottom radius cordurally in the cylinder?
MM's from the top are no different than from a port folder, so how are you going to do that cordural in practice?

[Condyn]

Here is a paper port map of my cylinder. ( it looks a lot better in the bore ) haha.

75.4% chordal width exhaust port with small top corner radii. By the way I have 30 dyno pulls and 28 passes on the engine. I checked on the rings after 20 passes and re-ringed since I was in there. Rings showed very little wear ( but wear non the less ) Where they were being forced back into the bore. Also very very slight wear, where the end gap slides over the B port edge. ( really need to move the pegs )

I cannot wait to try the optimum shaped 70% port. If it produces the same power or more, we will happily go that route!

[wobbly]

The engines I work on with 54 bore have a 72.3 % chordal width , as the factory has a thing about pin plugs so I cant use 100% on the Aux.
To make repeatable , reliable ports , dead on bore centerline imho is impossible by hand , with or without a paper template or a lasercut pattern on a stick , especially when dealing with a raw casting.

Thus the ducts first 20mm ( just past the 3 port bridge ends ) is CNC cut in a Rottler 6 axis running software designed for 4T port machining with a ball - on - a - stick cutter.
The port/duct is designed as a surface in SolidWorks or NX and the tool path generated in PortExpert.

Many cylinders are junked as material shrinkage is not consistent , and one of the bridges can end up too thin - doing this by hand , the port may well end up exactly the correct shape , but
would then be asymmetric in the bore , and this is not reliable @ 72% - been there , and cut the engine in 1/2 with a broken rod.
The asymmetry pushes the ring sideways in its groove as well as inward , and the ring pin gets bashed on every stroke - quite a few at 14800.

Maybe not a viable option for a Bucket , unless you have a sponsor that sells alot of weed , but vital use of what is now common technology when living on the edge and pushing to the absolute max.

[Condyn]

And then the plater who smokes said weed goes and ruins everything anyway.

[wobbly]

Dead correct , I have to send 3 emails , write on the cylinder and put a note in the box - NO CHAMFERS OR A BBC WILL BE PLACED WHERE THE SUN DOESNT SHINE.

[ken seeber]

The author forgot to mention Mat is a 10 times National Champ , getting the double digit was the goal in the weekend.

The full(er) story.

https://www.kartsportnews.com/2022/0...e-for-kinsman/

[Frits Overmars]

To make repeatable , reliable ports , dead on bore centerline imho is impossible by hand , with or without a paper template or a lasercut pattern on a stick , especially when dealing with a raw casting.
Maybe not a viable option for a Bucket .... but vital use of what is now common technology when living on the edge and pushing to the absolute max.

You said it Wob. I did not develop my port concept for Buckets, but I did make it available for Buckets, for everyone to use it as they see fit.

I have to send 3 emails , write on the cylinder and put a note in the box - NO CHAMFERS OR A BBC WILL BE PLACED WHERE THE SUN DOESNT SHINE.

I don't quite understand how the presence of the British Broadcasting Corporation would make a difference; I'd rather escort my cylinders with a loaded rifle.
Jan Thiel once considered bringing a pack of Pit Bulls with Aids to the plater's, but then he has always been famous for his creative ideas .

[lohring]

My simple minded porting templates for small, industrial type race engines is described below. Those engines have one piece cylinders with included heads so it's difficult to use port to head measurements otherwise. Maybe something similar would be helpful in larger engines.

Lohring Miller

[wobbly]

Ken and I were discussing transfer port flow regimes and he asked me to screenshot the Mass Flow Rate of a TM KZ R1 at peak power ( 13750 ).
This is the A port ( 1st to open ) , note the reverse flow down the duct at TPO and TPC due to a positive Blowdown pressure ratio , then a negative pressure ratio in the case.

[Grumph]

I don't quite understand how the presence of the British Broadcasting Corporation would make a difference; I'd rather escort my cylinders with a loaded rifle.
Jan Thiel once considered bringing a pack of Rottweilers with Aids to the plater's, but then he has always been famous for his creative ideas .

I've met the guys Wob sends his cylinders to. Nice guys, catch on quickly. Wob's stuff they understand - but they wanted to know if I knew Neil Hintz as his stuff was just plain weird. I think I reassured them. BBC = Big block Chevy. Don't know if that idiom translates into Dutch.

[wobbly]

Here is what I didn't expect , as I have never used the Mass Flow data metric in EngMod to investigate previously.
At 10,000 rpm , the low end of the used power band on track , there is no flow reversion from an excess Blowdown delta across the port face.
But there is huge back flow as the port is closing due to the case going negative.
I knew the inlet flow from the reeds begins at about TPC , as I did tests years ago cutting away the piston inlet side skirt , thinking it was impeding the flow into the case from the reed box.
But it doesn't , as the piston is well on its way up the bore when the reeds start flowing into the case.

No free lunch there sadly - but it makes me think that a large amount of Desaxe cylinder offset may be something to investigate again .
As in one direction of offset the timing asymmetry generated by this technique , causes late opening and early closing of the ports.
This may need the Exhaust timing increased to keep that side of the equation working correctly with the pipe TL.

[Flettner]

Or open the inlet port 30 degrees ABDC. Rotary Disc Valve.
But only in the power band, below those revs, port opens after transfers close. Sliding Gib tech. Perhaps?
Thats how my 360 is setup. Reeds are for wetlands.

[wobbly]

Yea I know Neil , but I am trying to win World Titles in Karting , not throw dirt in the face of a following rider in Vintage MX.
Both are worthy pursuits , but one uses up funds , the other is gona buy me an Aston Martin - fuck the tree huggers - with a BBC.

[Frits Overmars]

Here is what I didn't expect , as I have never used the Mass Flow data metric in EngMod to investigate previously.
At 10,000 rpm , the low end of the used power band on track , there is no flow reversion from an excess Blowdown delta across the port face.
But there is huge back flow as the port is closing due to the case going negative.
I knew the inlet flow from the reeds begins at about TPC , as I did tests years ago cutting away the piston inlet side skirt , thinking it was impeding the flow into the case from the reed box.
But it doesn't , as the piston is well on its way up the bore when the reeds start flowing into the case.

That's Herr Helmholtz messing up things for you, Wob. https://en.wikipedia.org/wiki/Helmholtz_resonance
The cycle from a positive crankcase pressure differential accelerating the transfer flow to a negative case differential slowing that flow velocity back to zero again takes a fixed amount of time. At low revs this time is less than the total transfer opening time, so the cycle continues, performing more than half a sine wave during the open transfer period.
It's the same phenomenon you can observe with piston-controlled inlet systems, where at low revs blowback can occur although the piston is still on its way up towards TDC, so the crankcase pump is still trying to inhale.

In theory the reed valve inlet system ought to prevent the crankcase pressure from dropping below atmospheric. In practice the reed valve needs this pressure drop before it will even think about going to work.
Neils gibs-controlled rotary inlet system offers the best of both worlds. Although.... you may remember Roland Holzners 24/7 experiment at Modena a couple of years ago. Roland realized it without any electronics because the CIK would have vetoed that. His system worked, but with the karting world being the karting world, the CIK vetoed it anyway, like it had done with Rolands synthetic inlet inserts some time before. If the CIK doesn't like you, they'll let you know...

No free lunch there sadly - but it makes me think that a large amount of Desaxe cylinder offset may be something to investigate again .
As in one direction of offset the timing asymmetry generated by this technique, causes late opening and early closing of the ports.

Not even a free breakfast, I'm afraid. The problem is not the symmetry of the port timing; it's the duration of the timing. Asymmetry might have worked in the long-gone era of tiny crankcase volumes but these days Helmholtz will hardly be impressed by what the piston happens to be doing.

[HenkS]

You said it Wob. I did not develop my port concept for Buckets, but I did make it available for Buckets, for everyone to use it as they see fit.

Not being able to answer the question is correct, only possible in CNC for the few who can.
But they are not waiting for such a simple drawing.
And for the amateurs who are the real target group here, be misled !!
As can be clearly seen in this example, because they can only work with portmaps.

Thank you on behalf of all "Buckets"
What an arrogance !