ESE's works engine tuner

[wobbly]

I must have explained staggered Aux port theory 100 times , but here goes.
Its a twofold act.

Firstly - At EPO , we want the highest amplitude , and longest duration initial wave front ( yes its sonic ) entering the duct and subsequently the header.
This will generate the highest and longest negative pressure ratio at the Ex port around BDC if the pipe geometry is correctly timed.
To achieve this goal we want a single port with the most efficient Blowdown geometry ( ie area ) dumping into the smallest duct area possible.
This is helped immensely by lifting the duct floor ( Jan's genius ) and or necking down the duct exit area to achieve Mach 0.8 ( some tosser called Wobbly's innovation ).

Having the Aux ports lower achieves two goals , it restricts the EPO area , thus generating a high and wide initial wave front , and that wave front is coherent ie because
the Aux duct length is considerably longer than that of the main , this would smear out the high pressure ratio we are striving to achieve if it was active at EPO.
The area at the point the Aux side ducts enter the main is the greatest , and having a later timed high intensity "pulse" entering that area after the main one has passed would in effect create a double
camel hump pressure front that confuses the already complex pipe / wave interaction.
Thus the staggered Aux port is reduced effectively to the role of only dropping the Blowdown remnant pressure before TPO.

Lastly , having concurrent 3 port EPO generates huge Blowdown efficiency , and this kills the front side power , as the staggered transfers actually use remnant Blowdown pressure to
stall flow in the highest TPO , and having very low remnant Blowdown pressure severely reduces the transfer scavenging regimes ability at lower rpm's.

So there you have it SOTA is now staggered Ex and transfers that are subtilty interactive.

[Flettner]

What if the axillary ports and main ports are the same length?

[wobbly]

That would eliminate the time smearing issue but if you then reduced or eliminated stagger , the quickly increasing area presented to the Blowdown pressure at EPO would be much bigger ,
thus the initial sonic wave front amplitude and duration would be commensurately reduced.

Plus then you also have a huge drop in Blowdown pressure at TPO - affecting the staggered transfers scavenging efficiency , and thus front side power capability.

All this theoretical analysis , for me anyway , only applies to outer limit tuning - playing with low bmep shitboxes holds no interest whatever ,
for others its the very reason for staying alive , so no adverse judgment on my part.

[Flettner]

That would eliminate the time smearing issue but if you then reduced or eliminated stagger , the quickly increasing area presented to the Blowdown pressure at EPO would be much bigger ,
thus the initial sonic wave front amplitude and duration would be commensurately reduced.

Plus then you also have a huge drop in Blowdown pressure at TPO - affecting the staggered transfers scavenging efficiency , and thus front side power capability.

All this theoretical analysis , for me anyway , only applies to outer limit tuning - playing with low bmep shitboxes holds no interest whatever ,
for others its the very reason for staying alive , so no adverse judgment on my part.

Im not thinking of low BMEP shitboxes, what if you have considerable more blowdown area? What would you do with it? How would you arrange the porting, Being able to push Peak BMEP to higher revs?

[wobbly]

I really dont know what to think Neil.
As it stands there is no more real estate for extra transfer area to match a big increase in Blowdown STA , and we are already at the outer limit of reliability
reving a 125 to 14800 all day - so increasing the bmep at whatever higher level ,to a higher rpm simply isnt possible.
It would need a complete rethink - Frits 360* radial transfer option comes to mind , but that concept needs a huge amount of practical R & D to work into a viable
mechanical layout - and of course where is the cash going to come from, and who is going to use it in what commercial environment.

[Gradella23]

I really dont know what to think Neil.
As it stands there is no more real estate for extra transfer area to match a big increase in Blowdown STA , and we are already at the outer limit of reliability
reving a 125 to 14800 all day - so increasing the bmep at whatever higher level ,to a higher rpm simply isnt possible.
It would need a complete rethink - Frits 360* radial transfer option comes to mind , but that concept needs a huge amount of practical R & D to work into a viable
mechanical layout - and of course where is the cash going to come from, and who is going to use it in what commercial environment.

regarding this, any thoughts about these weird exhaust port shape? i don't know anything about that, only that they're some italian guys selling vespa kits.
I found them casually on Facebook. Never seen anything like that before tbh, at least it's different

https://www.zeusengine.it/ and ZEUS special components on FB for more pics

[Gradella23]

regarding this, any thoughts about these weird exhaust port shape? i don't know anything about that, only that they're some italian guys selling vespa kits.
I found them casually on Facebook. Never seen anything like that before tbh, at least it's different

https://www.zeusengine.it/ and ZEUS special components on FB for more pics

Ok now i got It: It's some sort of symmetric scavenging with a second boost transfer under the main exhaust. Mm i can't decide if It's dumb or interesting, for sure It's out of the ordinary

[Flettner]

I really dont know what to think Neil.
As it stands there is no more real estate for extra transfer area to match a big increase in Blowdown STA , and we are already at the outer limit of reliability
reving a 125 to 14800 all day - so increasing the bmep at whatever higher level ,to a higher rpm simply isnt possible.
It would need a complete rethink - Frits 360* radial transfer option comes to mind , but that concept needs a huge amount of practical R & D to work into a viable
mechanical layout - and of course where is the cash going to come from, and who is going to use it in what commercial environment.

I remember you once lamenting that if you could lift the head for extra exhaust blowdown, you would. Im not lifting the head (ie no unconventional valve in the head) but I do have the opportunity to build a new cylinder, water cooled, 125cc, with an unusual exhaust port layout that will increase exhaust area. Yes based around the twin port. I just dont want to make a mess of the rest of the cylinder by not taking advantage of an optimised transfer layout, ie timings.
At the moment Im basing all my information largely on using 2 x 65cc ...... because I dont know any better.

[TZ350]

.
Another low BMEP shitter.



Having got excited about the idea of radiusing the edge of the piston in the transfer port area. I thought I would try it on the new Suzuki GP110 (48mm stroke) with its 54mm cylinder from a NSR250 twin.

Max crankcase volume. Long 115mm rod. Crank machined and lightened to within an inch of its life. Balance factor 50%. Tungsten slugs pressed in with 3 tons.

Probably doing the piston edge radiusing wrong.



What it looks like down the bore.



Ok, so this may have been a mistake. The transfer radiuses open the sides of the exhaust port earlier than desirable. Could be an issue. Will see how it goes.

[Flettner]

Wobbly, if the eye ports are essentially 'one way valves' exhaust out but no reverse pulse back up them, what height would you place them?
Exhaust out but then about TPO they shut, to not open again until blow down on the next cycle.
Eye ports and main ports same length.

[Flettner]

.
Another low BMEP shitter.



Having got excited about the idea of radiusing the edge of the piston in the transfer port area. I thought I would try it on the new Suzuki GP110 (48mm stroke) with its 54mm cylinder from a NSR250 twin.

Max crankcase volume. Long 115mm rod. Crank machined and lightened to within an inch of its life. Balance factor 50%. Tungsten slugs pressed in with 3 tons.

Probably doing the piston edge radiusing wrong.



What it looks like down the bore.



Ok, so this may have been a mistake. The transfer radiuses open the sides of the exhaust port earlier than desirable. Could be an issue. Will see how it goes.

Its all most of us can afford to play with.

[F5 Dave]

.
Another low BMEP shitter.



Having got excited about the idea of radiusing the edge of the piston in the transfer port area. I thought I would try it on the new Suzuki GP110 (48mm stroke) with its 54mm cylinder from a NSR250 twin.

Max crankcase volume. Long 115mm rod. Crank machined and lightened to within an inch of its life. Balance factor 50%. Tungsten slugs pressed in with 3 tons.

Probably doing the piston edge radiusing wrong.



What it looks like down the bore.



Ok, so this may have been a mistake. The transfer radiuses open the sides of the exhaust port earlier than desirable. Could be an issue. Will see how it goes.

Tbh it just looks you have created two obvious hot spots on the piston front.
Reduced squish cooling about 50%.
And opened the exhaust port early, but only on the sides.

[diesel pig]

Wobbly, if the eye ports are essentially 'one way valves' exhaust out but no reverse pulse back up them, what height would you place them?
Exhaust out but then about TPO they shut, to not open again until blow down on the next cycle.
Eye ports and main ports same length.

I am just going to state this so if I am right I will look good for a week and if I am wrong I will only look bad a week.
I think Flettner is at least thinking about controlling the port's with a sliding sleeve like a Bistrol aero engine but using a 2 cycle operation instead of 4 cycle operation of the Bistrol.

[Flettner]

I am just going to state this so if I am right I will look good for a week and if I am wrong I will only look bad a week.
I think Flettner is at least thinking about controlling the port's with a sliding sleeve like a Bistrol aero engine but using a 2 cycle operation instead of 4 cycle operation of the Bistrol.

No, conventional bridge port except twin outlet but with more ports further round the cylinder where exhaust normally cant go. Extra eye ports but with a rotating valve that can open and shut as needed. Extra blowdown but thats all.

I still have the sleeve engine in a box waiting for a spare YZ250 gearbox to materialize.

[wobbly]

So this begs the question - does your engine need more Blowdown STA , and more specifically can that extra port time area be matched by a commensurate increase in Transfer STA.
Generating oodles of Blowdown has more downside than it does any perceived advantages , by way of seriously killing front side power capability.
And my previous comments about having excess initial area at EPO still apply , in that this will reduce the amplitude and bandwidth intensity of the wave front exiting into the diffuser.
Again I reiterate all this I take from the perspective of trying to push the boundaries of what can be achieved with current SOTA techniques.