ESE's works engine tuner

[Frits Overmars]

well maybe im fuked. the honda cylinder i have was 124 A and B. 127 C. so i put A at 128 and B/C 127. ill try it and see. if that dont work i can put B/C at 130 and leave A at 128 and try that. my concearn is not letting the transfers get to high but i think ill be ok

128° for A and 130° for B and C sounds fine, provided the transfer timing doesn't take too much away from the exhaust blowdown angle.area.

[lodgernz]

I think I understand how to derive the time-area for the exhaust and transfer ports, but I'm not sure that my method for the blowdown STA is correct.
I think that, for example, if exhaust opens at 85º, then the mean exhaust area is that exposed at 132.5º.
Similarly, if the A transfer opens at 115º, then the mean open area is the area exposed at 147.5º.

For the blowdown mean area, I'm assuming this is the area of the exhaust port exposed when the crank angle is halfway between EO and TO, ie in the above case at 100º.

Please, anybody, correct me if I have that wrong.

[Frits Overmars]

I think I understand how to derive the time-area for the exhaust and transfer ports, but I'm not sure that my method for the blowdown STA is correct. I think that, for example, if exhaust opens at 85º, then the mean exhaust area is that exposed at 132.5º. Similarly, if the A transfer opens at 115º, then the mean open area is the area exposed at 147.5º. For the blowdown mean area, I'm assuming this is the area of the exhaust port exposed when the crank angle is halfway between EO and TO, ie in the above case at 100º.
Please, anybody, correct me if I have that wrong.

There are no such animals as an exhaust mean area and a blowdown mean area. The uppermost millimeter of port height is open for much longer than the lowermost millimeter and you must take these various periods of time into account. That's what the angle.area and time.area concepts do.

[wobbly]

Why fuck about deriving anything - there are plenty of free, or even better "proper" software programs that give you computed STA or Angle Area directly
with simple inputs.

[lodgernz]

There are no such animals as an exhaust mean area and a blowdown mean area. The uppermost millimeter of port height is open for much longer than the lowermost millimeter and you must take these various periods of time into account. That's what the angle.area and time.area concepts do.

Hi Frits, thanks for responding.
I agree that Jennings method as I outlined above seems terribly flawed in its concept and assumptions, but if I want to use his published ranges of time-area, I have to use his methods.

I also used your method (as I understood it) of multiplying the area of each mm "slice" of the port by the number of degrees that slice would be open, and totalling those angle-areas for the whole port, then dividing that total by the cylinder capacity. The answer was 42 deg-cm²/cm³, which doesn't seem to agree with any published values I can find. Clearly I'm doing it wrong.
I've read this entire thread several times, along with all four pit-lane.biz GP125 threads several times, but I'm still missing something. Quite a lot as it turns out.

I know you're a busy man Frits, but I'd really appreciate some guidance here.

[lodgernz]

Why fuck about deriving anything - there are plenty of free, or even better "proper" software programs that give you computed STA or Angle Area directly with simple inputs.

Because I want to understand it.

[peewee]

128� for A and 130� for B and C sounds fine, provided the transfer timing doesn't take too much away from the exhaust blowdown angle.area.

im trying to figure out the exh blowdown. in the past ive tried tall 200* exh ports (500cc single) and i simply couldnt make it work, with low transfers (130) and high transfers (136), no matter what combination i couldnt make it work. a well tuned 300cc probly had more power and certainly a wider bandwidth.

so i went back to the drawing board with new cylinder and remebered some warning advice you had for over zelous tuners getting the exh to high. for that large of engine i think 192 exh is a good place to start so thats what ive done. since i already have the A at 128 and B/C at 127 im gonna try it this weekend. i have to admit ive never tried the B/C higher than A but i want to test it. next week i can pull the cylinder back off and easily raise the B/C to 130 and keep A at 128 then test again, all while leaving 192 on the exh atleast for now

why i couldnt get the high exh timing to work on this big engine im not sure. to much time*area for the speed the piston is traveling perhaps ? im not sure. what works on them small engines sure doesnt seem to be any good on the large engines

[senso]

For simple, durable engines I have been using 187º exhaust and 124-127º in the transfers with good results, paired with "low" compression heads(around 12:1 in 50-75cc engines), they are not power houses, but much better than stock.
Given that removing material is much easier than adding it(and plating the new material is even worse), I would point for 187-190º in the exhaust.

[Frits Overmars]

Why fuck about deriving anything - there are plenty of free, or even better "proper" software programs that give you computed STA or Angle Area directly with simple inputs.

Because I want to understand it.

The best answer in the world .

I agree that Jennings method as I outlined above seems terribly flawed in its concept and assumptions, but if I want to use his published ranges of time-area, I have to use his methods.

Jennings' values are superseded now and his method was far from exact, but it served a purpose: it gave an impression of the angle.area and time.area concepts in an era when nobody had access to a computer.

I also used your method (as I understood it) of multiplying the area of each mm "slice" of the port by the number of degrees that slice would be open, and totalling those angle-areas for the whole port, then dividing that total by the cylinder capacity. The answer was 42 deg-cm2/cm3, which doesn't seem to agree with any published values I can find. Clearly I'm doing it wrong. I've read this entire thread several times, along with all four pit-lane.biz GP125 threads several times, but I'm still missing something. Quite a lot as it turns out. I know you're a busy man Frits, but I'd really appreciate some guidance here.

I can't check your calculations because I know hardly anything about your engine. My advice would be to start by calculating the raw angle.areas without bothering about cylinder capacity and crankshaft rpm for now, and use millimeters, not centimeters. You can use the Aprilia values as reference; you'll find them in the Pit-Lane threads and I also posted them here somewhere. In case someone else is interested in this subject, here are a couple of links to some of those Pit-Lane threads:
http://www.pit-lane.biz/t3173p816-gp...-part-2-locked
http://www.pit-lane.biz/t3173p969-gp...-part-2-locked.

...for that large of engine i think 192 exh is a good place to start so thats what ive done. since i already have the A at 128 and B/C at 127 im gonna try it this weekend. i have to admit ive never tried the B/C higher than A but i want to test it. next week i can pull the cylinder back off and easily raise the B/C to 130 and keep A at 128 then test again, all while leaving 192 on the exh atleast for now

Specific time.areas are supposed to be universal; the size of the engine doesn't matter. But remember that short-stroke engines need more exhaust timing in order to achieve their desired specific blowdown time.area. For the short-stroke Aprilia RSW500 (awful engine!) it was even necessary to limit the transfer timing (to something like 122° if I remember correctly) in order to get sufficient blowdown TA. So don't raise your transfers just yet...

[lodgernz]

The best answer in the world .

Jennings' values are superseded now and his method was far from exact, but it served a purpose: it gave an impression of the angle.area and time.area concepts in an era when nobody had access to a computer.I can't check your calculations because I know hardly anything about your engine. My advice would be to start by calculating the raw angle.areas without bothering about cylinder capacity and crankshaft rpm for now, and use millimeters, not centimeters. You can use the Aprilia values as reference; you'll find them in the Pit-Lane threads and I also posted them here somewhere.

Thank you Frits. I do use mm, I only convert the answers to cm because those are the units of the most-published figures.
I'll look for those Aprilia figures.
Regarding my angle-area value of 42: I'm embarrassed to admit that I used the wrong column in my spreadsheet (where would we be without spreadsheets?) and my answer using your method should have been 5.966... , which is of the expected order of values, and not too far away from those calculated using Jennings method.
The time-area value of this cylinder at 12,000 RPM would therefore be 0.0000829, again, of the expected order. Clearly the engine is deficient, but I knew that already. Now I have a good method of quantifying port areas and timing that I actually understand. You've made an old man very happy.

[wobbly]

OK I get it about understanding how to derive the STA numbers, but to then apply those numbers to Jennings old assumptions makes no sense.
Since then due to QUB, to Tom Turner, to Kurt Leaverton and then leading to Vannicks EngMod2T we now have cheap accessible code that not only calculates easily the STA numbers but then relates
all the numbers to each other, and to a desired bmep at a desired rpm from a specific swept volume.
Thus you KNOW how much power each port is capable of in relation to the others.
In this day and age I personally see no sense in harking back to prehistoric writings about 2T technology when all the answers you need are available at the click of a mouse.
BUT - here is the kicker, just up the thread we have someone working in the dark - wondering why a certain transfer height didnt work with some arbitrary Ex port height.
Without ANY calculation, I can tell you straight off that having any set of reasonable transfers sitting at 130* or even worse 136* duration and combining that with
an Ex sitting at 192* will not even begin to work PROPERLY due to compromised blowdown.
130* transfers are EXTREMELY high, a 192* Ex is EXTREMELY low for any high performance application.
The transfers are set for an absolute full race Aprilia GP type tuning, and the EX is down where a low BMEP MotoX engine would be.
Running the ports thru any simple STA program would give you the answers immediately.
If you have that sort of powerful information you then dont even need to have the experience to look at the timings and say, it wont work, due to the huge transfer STA creating very low velocity
and thus uncontrolled transfer scavenging streams, combined with very low blowdown STA that then creates a huge positive pressure ratio across those excessive transfers - making the situation
even worse.
Rant over for today.

[peewee]

i have engmod but it takes aleast a week if not alittle more to input all the info since i have other obligations during the day. my ktm is loaded in engmod but i just havent got to the honda yet. the 136 trans engine was a mistake i did quit a while back. long before i had engmod or much common sense. of course i wouldnt do the same mistake today. our major holiday is here in a couple weeks and i simply dont have enough time to mess with engmod until after that.

since we're on the subject, how does engmod account for the kickers (hooks) in the ports ? on the transfer port layout page theres a section that says 'area ratio between window and passage exit'. i assume this is where it takes into account any hooks ? but i dont understand how it can calculate the rearward/forward angle at which the kickers aims, since there is no place to put that info, only the ratio of window to passage exit. my ktm doesnt have hooks so theres wasnt much difficulty inputting the required info but honda has hook in the A and B.

edit: ok i forgot about the 'transfer port cylinder entry design' page. that must be where it figures the hook angles ?

[lodgernz]

OK I get it about understanding how to derive the STA numbers, but to then apply those numbers to Jennings old assumptions makes no sense.
Since then due to QUB, to Tom Turner, to Kurt Leaverton and then leading to Vannicks EngMod2T we now have cheap accessible code that not only calculates easily the STA numbers but then relates
all the numbers to each other, and to a desired bmep at a desired rpm from a specific swept volume.
Thus you KNOW how much power each port is capable of in relation to the others.
In this day and age I personally see no sense in harking back to prehistoric writings about 2T technology when all the answers you need are available at the click of a mouse.
BUT - here is the kicker, just up the thread we have someone working in the dark - wondering why a certain transfer height didnt work with some arbitrary Ex port height.
Without ANY calculation, I can tell you straight off that having any set of reasonable transfers sitting at 130* or even worse 136* duration and combining that with an Ex sitting at 192* will not even begin to work PROPERLY due to compromised blowdown.
130* transfers are EXTREMELY high, a 192* Ex is EXTREMELY low for any high performance application.
The transfers are set for an absolute full race Aprilia GP type tuning, and the EX is down where a low BMEP MotoX engine would be.
Running the ports thru any simple STA program would give you the answers immediately.
If you have that sort of powerful information you then dont even need to have the experience to look at the timings and say, it wont work, due to the huge transfer STA creating very low velocity
and thus uncontrolled transfer scavenging streams, combined with very low blowdown STA that then creates a huge positive pressure ratio across those excessive transfers - making the situation
even worse.
Rant over for today.

...and a most articulate and erudite rant it is Wobbly.
I wouldn't use the "prehistoric" assumptions such as Jennings and Blair now that I have Frits' methods and his numbers for the Aprilia.
I'd love to be using classy software to avoid the brain work, and I guess the "cheap" software you're talking about is EngMod2T. It might be cheap for someone who makes a living from preparing engines, but USD400 is a bit of a hit for the average bucket racer. Any suggestions for more accessible software? I have bought one of the really cheap ones, but it appears to be using Jennings methods, so probably not that one.

[peewee]

there appears to be a free calculator here. never tried it but it might be handy http://www.x-h2o.com/index.php?threa...program.43429/

[wobbly]

As its only single dimensional EngMod cant " account " for transfer hooks, but what it does have is a very accurate canned model of the scavenging regime of an RS125.
This type of setup would apply the flow and scavenge characteristics of any engine with similar port layout with hooks.
All you do is enter your accurate port geometry and click the RS125 Scavenging Model at the bottom of the transfer page.

Frits numbers for the Aprilia of course make the assumption that you are able to develop EVERY aspect of the engine whole , to be able to use those ports
at that level of finesse - be careful, or should I say err on the side of caution.