ESE's works engine tuner

[TZ350]

Did you model the nozzle as a short tapered section ( 30mm say) from the duct exit up to the header dia ( as the first section of the pipe) and this is made as an oval to round transition in the flange on T port and tripple port designs.

I modelled the convergent half of the nozzel in the exhaust port port duct and the other half as a divergent cone at the start of the header.

I am not sure if this is the right thing to do but the simulator liked it. The pipe is my old Honda RS125 chamber.

... im not sure this theory will apply to making more power with a single port.

Having said that, a 40mm pipe entry on an engine only making 30 Hp is way too big, so reducing the duct and or header area, or maybe both, will very likely work real well.

Be real interesting to see if the sim reflects reality on a dyno, in your single port scenario TeeZee.

Yes dyno time will be interesting ......

[speedpro]

Interesting design at the end, 22mm dia for 3mm, then diverging to 25mm over 20mm length

[TZ350]

EngMod2T

Transfers openning 114 atdc vis 117 atdc, all other aspects of the engine model are the same.

In the early days I chose a transfer opening time of 114 atdc duration 132 for 12,000 rpm based on Jennings and Bells books. This involved skimming the top of the barrel and fitting a spacer plate. This must have been a popular thing to do as I saw many strokers with small spacer plates under their barrels.

I do remember Sonic-V saying that he has often been disapointed by tall transfer ports.



The simulator works on STA or specific time area and it tells me that with the effective transfer port window that I have the transfers only need a duration of 126 degrees opening 117 atdc for a little more power and improved blowdown.

Low and wide just as Wobbly said.

[TZ350]

Interesting design at the end, 22mm dia for 3mm, then diverging to 25mm over 20mm length

Pinched that bit from the later RS example file that came with the simulator, I expect its a tail pipe venturie that controls the bleed down and that the rest of the tail pipe does not come into the equation.

[Frits Overmars]

That is like putting cooling fins inside the ducts. Think about it...

Hmmm good idea..

With regards to Frits post I assumed he is inferring that the ports will serve to remove heat from the cylinder.........Thus the cooling system will....be cooling the transfers.

Do you think the turbulence created, or the surface area would in some way (Heat transfer, drag effects?) negate the extra inlet/exhaust/transfer area then available?

Frits - I'm also still thinking about the "cooling fin" comment. Not even sure if you meant it as a + or - now!

The good news is that y'all did think about it, and that is what I hoped to accomplish.
Husaberg is right: 'the ports will serve to remove heat from the cylinder'. But then he spoils it by saying: 'the cooling system will...be cooling the transfers'.
Koba seems more cautious. And he is right too. Heat transfer: yes. But from where to where?
'Cooling fins' is a misleading expression, deliberately in this case, because I tried to set you on the wrong foot. I should have called them by their scientific name: heat exchangers....
The cylinder material will always be hotter than the fresh charge in the transfer ducts. So these 'internal fins' will cool the cylinder to the detriment of the charge density. Not good for power....

[koba]

The good news is that y'all did think about it, and that is what I hoped to accomplish.
Husaberg is right: 'the ports will serve to remove heat from the cylinder'. But then he spoils it by saying: 'the cooling system will...be cooling the transfers'.
Koba seems more cautious. And he is right too. Heat transfer: yes. But from where to where?
'Cooling fins' is a misleading expression, deliberately in this case, because I tried to set you on the wrong foot. I should have called them by their scientific name: heat exchangers....
The cylinder material will always be hotter than the fresh charge in the transfer ducts. So these 'internal fins' will cool the cylinder to the detriment of the charge density. Not good for power....

Hmm, very smart. Makes me think twice, no already done that, (must be up to 36) about the "Boysen" type ports for my motor. I'm betting speedpro is thinking along the same lines as soon as he reads that.

[Frits Overmars]

I just had an idea - What if the transfer ports were divided vertically into upper and lower sections. You could have the gas flow directed in one direction as the port opened and as the second lower portion opened it's gas flow could be in some other direction. There would not neccessarily be a reduction in gross flow as the port duct could be enlarged to allow for the divider..... I envisage the divider following the curve of the port right to the duct entry so effectively you will have 2 seperate transfer ports stacked. You could even close off the outer duct leading to the upper portion of the port with a guillotine, if that was a benefit.

The idea is good. But your logic is not always... "There would not neccessarily be a reduction in gross flow as the port duct could be enlarged to allow for the divider". Yeah, right. Then you could also enlarge the port without putting in the divider.That would give you even more flow area.

Then why is it still a good idea? Because you reduce the port height in the curve; the ratio of inner curve radius to outer curve radius becomes larger, and that is very good for the flow. Look at any air conditioner ceiling-outlet: they are all shaped like that.
To my knowledge the idea was first proposed by a german researcher, Ernst Ansorg, around 1965. I have seriously thought about applying it, but incorporating thin-walled curved guides in a cylinder casting proved too difficult at the time. It might still work though.
Yes, the guides will heat up the passing charge. But the net result will probably be positive; especially if the guides are kept short, only in the upper, curved part of the ducts.

I also like the idea of closing off the outer/ upper transfer ducts. It would prevent wrongly-timed exhaust pulses from shoving fresh charge from the cylinder back into the crankcase, and that would yield a very civilized power curve.

[bucketracer]

... good idea? Because you reduce the port height in the curve; the ratio of inner curve radius to outer curve radius becomes larger, and that is very good for the flow.

THis sounds like something TeeZee was doing with his curved inlet. I will see if I can find a picture.

Inlet Manifold Dyno Test



Red line is the original inlet manifold, Blue line is the manifold with the divider fitted.

[breezy]

teezee, i noticed on the exhaust print out there are values for the pipe volume cc and also a ratio of the pipe against the engine cc. what , if any , do these values play in the pipe design.. thanks

[wobbly]

The exhaust exit "nozzle" was used first by Helmut Fath ( my hero ) when tuning for Honda where their V twin 250 had one stinger 150 long the other 450 long.
I have tested all manner of variations and the best is around 10mm of parallel nozzle and then 10mm of divergence to a stinger around 1.5mm bigger.
This reduces the effect of the waves bouncing up and down the stinger off atmosphere disrupting the rear cone waves.

The pipe vol/engine cc field in the pipe screen was added by Neels to the program when Frits noted that he had calculated this for the RSA - maybe he can elaborate on the relationship.
Note also that there is two fields for the length to end of header and length to end of diffuser.
I got Neels to add this as so few pipe designs are "correct" and its a pain to calculate all the time.The header end should be 30 to 32% and the diffuser should be 64 to 68%

TeeZee - really glad that you are looking at the STA numbers and realising that the sim is telling you what is needed - or not in many cases.
Getting all the elements of a design in harmony is what makes big power numbers.
I would try making the divergent header nozzle longer - very short ones can create shock waves and reduce the energy available to do positive "work" in the pipe.

[F5 Dave]

The old RS pipe has a stinger join. for my 100 I have made up some interconnect bits of tube machined with different tapers & sizes that can be easily swapped. But with the pipe still out of whack in other areas I haven't had much conclusive results with these experiments.


For the transfer duct dividers I was imagining heated bent razor blades devconed in place.

[dinamik2t]

Hey, TZ, nice seeing you improving those results!
I noticed one thing in you ex.port data. Isn't 74% (chordal) of the bore too much?
I liked your idea on the inlet divider too! Yielded almost 1.5whp!

to a stinger around 1.5mm bigger.

That worked best for me too!

A couple of days ago I tried modifying the pipe design a little (so far, I tried every other variable, except the pipe). I don't want to build a pipe from stratch and limited myself to modifications only after the mid section.
So I came up with this idea; seperating the baffle cone into two stages of different angles. I saw this design in a Rotax pipe. First stage was about 24 deg and the second one was 33 deg.
I did a lot of testing and managed to achieve a great power increase from 38 to 42 hp.
I am not sure about the small stinger diameter and the laaarge angle of the second baffle stage (40 deg). Both numbers though gave the best results among other variants ; at least in the simulator. Perhaps I'm missing something, like back then with the wall pipe temperature?

Here's the "old" pipe design:


and here's the newer one. Mid section length reduced 20mm, stinger length increased 80mm, plus the alterations in baffle:


No other parameter was altered.

[bucketracer]

Hey, TZ, nice seeing you improving those results!
I noticed one thing in you ex.port data. Isn't 74% (chordal) of the bore too much?

Hi dinamik2t, TeeZee is impressed with your work and carfully reads your posts.

All the team ESE engine exhaust ports are 70+% chordal of the bore, TeeZee has been running about 75% with good 1mm rings.

[dinamik2t]

That compliments me, thank you! I don't think of myself to be that great though..

Have you ever measured ring life with such widths? In hours or km s perhaps? I'm very curious as I always though of ~85% arc width to be somewhat the limiting percentage for decent ring life. I believe that 85 arc must be around 69 chordal.
I really don't know; never tried anything above that...

[NordieBoy]

For the transfer duct dividers I was imagining heated bent razor blades devconed in place.

As long as they don't have knife edges or you'll get a wobbly smack.



Thin brass sheet?