ESE's works engine tuner

[AndreasL]

With the "dam" in place and all (if I remember correctly) of the remaining port area in the blowdown region I don't think you'd want much of a reduction at all.
75% of the original port area, or perhaps equal to or sligtly larger than the remaining area could be good starting points for some work in Engmod.

Thats what came to my mind during lunch as well.
My interpretation of Wobblys guidelines has always been for % of TOTAL ex port area.
The last days we have learned that a "more accurate way" may be to base the spigot min area on blowdown numbers alone. Hopefully we will get to know how some day in the future.

But I'm sure TZ will tell us what area % used.

Great to see the thread getting back to DIY Works Tuning.

[Frits Overmars]

First we have the blowdown area. I relate all other exhaust system areas to it; then I don't need to differentiate between 75% for a triple port, 90% for a single malt port, and so on.

I agree completely that we should be using the blowdown as a basis for all this, as it has a direct relationship to the power capability available. Now that we are seeing the real possibilities surrounding lifting the port floor, this is again making the port window area even more irrelevant so I need to start generating a data point set to indicate the numbers we need to be looking at based on blowdown STA. Add to this the duct length factors I detailed before and then real gains can be made with ease.
Neels has done an update to the EngMod RSW sim using the above numbers that will make your socks roll up and down. We will see soon what he has come up with.

With the "dam" in place and all of the remaining port area in the blowdown region I don't think you'd want much of a reduction at all. 75% of the original port area, or perhaps equal to or sligtly larger than the remaining area could be good starting points for some work in Engmod.

My interpretation of Wobblys guidelines has always been for % of TOTAL ex port area. The last days we have learned that a "more accurate way" may be to base the spigot min area on blowdown numbers alone. Hopefully we will get to know how some day in the future.

Like Teriks suggests, after the blowdown area we probably do not want a further cross flow area reduction down the exhaust duct. Wobbly and Neels are already pondering on new promising duct shapes.
My experience is somewhat biased because the Aprilia-research was cut short by the two-stroke ban in GP racing, so I concentrated on my FOS cylinder layout with blowdown area to spare, even with my mild 192° exhaust timing. The exhaust floor timing was 160°; well above the 130° transfers, so this layout may not be directly comparable with a bucket-situation. But for what it's worth, the FOS exhaust ducts expand at a 3° included angle right from the blowdown area.
I guess, and until it has been tested, it is no more than a guess, that for a bucket the exhaust duct should expand between 0° and 3°, starting at the blowdown area.
With that I mean that all cross flow areas, when converted into circles, should form a cone with a 0° to 3° included angle.

[Frits Overmars]

One more word about that exhaust floor. Looking at TZ350s picture I get the impression that his situation is not very different from mine: for the most part his floor is well above the transfers too; only the middle part of the exhaust window, where the dam is, extends a little further down.
But the blowdown flow should make use of all available time and area between exhaust opening and transfer opening, so the exhaust window should extend down to the effective transfer opening timing. Having the exhaust floor higher than that is giving away valuable real estate.
Yes, I do it too in the FOS system, but for me there is no other way. And what's more, I have about twice his total exhaust port width and my ports do not suffer from the area loss caused by the large corner radii that TZ has to use in order to keep the piston ring alive in his very wide single exhaust port.
All in all I am not surprised that TZ's dam-cylinder has trouble reaching the power level of the dam-less cylinder, and that any flow-aiding radius at the dam helped.

[peewee]

Anyone with ideas how to create at least SOME inner radius to some straight and very narrow transfers? (Approx 15x15mm at the case-to-cylinder entry.)

First thought was to add epoxy and then try to shape it with a curved file...but I don't really see me having success doing so.

Make some inserts and epoxy them to the inner wall?
Maybe not to bad except no uniform surface in any direction...but the epoxy will take care of that I guess.

Any input and crazy ideas is more than welcomed.
Cold (-19 yesterday) greetings from the other side of the globe.

this is how I decided to do it. first I made 2D drawing then I can print this on paper. then I can cut it out and trace than onto a thin piece of flat alloy plate and cut out that. then I can use that as my template when I put in the epoxy. after that I just grind down the epoxy to the indentation that my tamplate has left when it was pressed into the uncured epoxy. its hard to explain but maybe you understand

[Frits Overmars]

I like your port drawing Peewee; it has a nice gradual narrowing. How did you establish the inner and outer duct radii and their center positions?

[AndreasL]

I like your port drawing Peewee; it has a nice gradual narrowing. How did you establish the inner and outer duct radii and their center positions?

Finally it might be the right time to ask a little about what numbers goes where in your drawing Frits?
I'm a bit stuck trying to get the position of every dot etc sorted when scaling it for my own engine.

[MotleyCrue]

One quick question, how long should the ring locator pin be (I will be making a pin and relocating to the 6 o'clock position)? Never had a locator pin out before to see how long it is.

[peewee]

I like your port drawing Peewee; it has a nice gradual narrowing. How did you establish the inner and outer duct radii and their center positions?

frits theres some free 3D programs like solidworks but obviously with less functionality but for simple stuff the free ones work great. what I did was just take a few quick measurements from the cylinder, like how tall the inner wall is, how big the transfer entrance is, then you can draw what you want with the program. you can make the radius what ever you want, the walls what ever length you want, the roof angle into the cylinder what ever you want, etc.

[ief]

Curious to see if it turns out to be true that starting the exhaust header dia at the x % of the export will be the way to go. Somehow those anti step solutions never agreed with me. (and up to now haven't figured out why the header had to start with a big(ger) dia in the first place, didn't look very hard as well tho...)

But could well be wrong, as allways ....

[TZ350]

And,,, confirmed!
I did 9 pulls 3 without polished crown, three with polished, and three again without.
Average gain 0.8hp (peak 1.3hp)
All was done with new piston and rings.

Also did an equal test with overfilling the gearbox with 2dl oil extra.
Average loss: 0.5hp (dip 0.6)
Then tested to add a 1dl GL5 hypoidoil into the dexron VI i´m running.
Averege gain: 0.3hp (peak 0.4)

Have reached total peak at 26.78hp at 12200rpm with 10% VP116 octane mixed into ordinary premium fuel from station.

Very interesting results. ... Thanks.

My interpretation of Wobblys guidelines has always been for % of TOTAL ex port area.

But I'm sure TZ will tell us what area % used.

There have been a lot of good comments about the exhaust duct. I will have to sit down with Chambers and carefully review the recent posts and our work. There must be some miss match with what we have done, been fun though, maybe we will find success next time ...

[Frits Overmars]

I like your port drawing Peewee; it has a nice gradual narrowing. How did you establish the inner and outer duct radii and their center positions?

frits theres some free 3D programs like solidworks but obviously with less functionality but for simple stuff the free ones work great. what I did was just take a few quick measurements from the cylinder, like how tall the inner wall is, how big the transfer entrance is, then you can draw what you want with the program. you can make the radius what ever you want, the walls what ever length you want, the roof angle into the cylinder what ever you want, etc.

Finally it might be the right time to ask a little about what numbers goes where in your drawing Frits?
I'm a bit stuck trying to get the position of every dot etc sorted when scaling it for my own engine.

Scaling that drawing down only makes sense if various other dimensions from your cylinder and mine will also fit the same scale, which usually won't be the case.
I can recommend Peewees approach.

[AndreasL]

Thanks Frits and, of course, you right.
Scaling might not be the correct word, but for sure your drawing is the inspiration.

I already have several sketches in Catia for transfers and more.
A bit all over the place with to many ideas at the same time though.
Need to sit down and try to make something like peewee.
KISS...my hardest part.

Hope to have something to show of what can be done within the limited space of an old cylinder.
Don't expect anything fantastic, but I better start contributing to the thread and not just lurk around.

[wobbly]

Well at the moment what we know "works" is to make the header inlet 100% of the Ex port effective window area and place this at 2* bore diameter
from the port.
Then a nozzle of 75% effective area at 1.25* to 1.5* bore from the piston that has a smooth transition from oval to round ( steps DONT work as well ).
And the floor of the transition should be co-linear with the duct entry angle.
These are the numbers that Neels used to make near on 10% more power in his very accurate RSW125 sim - I challenge anyone to find any other way of improving Jan Thiels RSA/RSW by
that sort of gain in power.
And exactly the same numbers I have dyno and sim proven in dozens of project engines.

Just yesterday I measured up an 04 Honda CR125, and it has a much smaller duct exit than its predecessors,the area % and the spigot transition shape are dead on the money.
It even has reverse staggered transfers like an Aprilia, so as this model was the only cable driven servo PV they made, its a no brainer that
a couple of these will be going onto an MC21 to make a 80Hp road rocket.

The next step is to construct a point graph of all the proven results and to mathematically relate the Blowdown to duct exit and header entry areas - Frits request is my command.

[ief]

Well at the moment what we know "works" is to make the header inlet 100% of the Ex port effective window area and place this at 2* bore diameter
from the port.
Then a nozzle of 75% effective area at 1.25* to 1.5* bore from the piston that has a smooth transition from oval to round ( steps DONT work as well ).
And the floor of the transition should be co-linear with the duct entry angle.
These are the numbers that Neels used to make near on 10% more power in his very accurate RSW125 sim - I challenge anyone to find any other way of improving Jan Thiels RSA/RSW by
that sort of gain in power.
And exactly the same numbers I have dyno and sim proven in dozens of project engines.

100 % is fine as well Didn't know it was common knowledge allready, gutfeeling was kinda right for a change, yeaaay. My english is not up to the task of understanding what you mean with the green colored sentence and it seems importend.

[Frits Overmars]

The next step is to construct a point graph of all the proven results and to mathematically relate the Blowdown to duct exit and header entry areas - Frits request is my command.

Yeah right Mr Wright; pull the other one. You're as curious as I am, Wob .

I think we should look at the upper edge of the exhaust port first. The turbulence caused by a sharp edge there will destroy a lot of exhaust gas energy before we can even start harnessing it in an efficient duct & pipe. A generous radius there will not only improve the flow coefficient, it will also leave more energy available (De Laval nozzle) although that port edge radius will only create half a nozzle; radiusing the piston edge too would make it complete; it would also help in the return of washed-through fresh mixture.
Too bad these phenomenons can't be incorporated in EngMod, so we will have to experiment the hard way: on the dyno.