ESE's works engine tuner

[Peter1962]

I think I already did tell, some time ago.
With the same obligatory 30 mm carburettor, the 24/7 engine produced 5 hp more than the standard engine, and revved 500 rpm higher.
The injected engine had good driveability; anything more would be for Roland himself to reveal.
I could invite Roland to tell us here but I'm not sure if he has sufficient English. We always speak German when Italians are listening, and vice versa (Roland is from Süd-Tirol, the German-speaking part of Italy). Besides, he is always pressed for time. And when he finds some time, he gives lectures to interested youngsters.
Attachment 331785 Attachment 331786

Frits, do you know if Roland has plans to experiment with your 24/7 system on other types of 2 stroke engines where the rules do not prohibit such a device ?

[Frits Overmars]

I don't think so; he is tied up to his elbows in kart engine development.

[dtenney]

Frits....was the power curve for the 24/7 motor showing better HP and torque everywhere versus the stock Modena engine? Do you know at what rpm the reeds were opened? It would be interesting to see the results from testing the motor on a kart to see if the power improvement on the dyno yielded quicker lap times on the track.

[Frits Overmars]

Frits....was the power curve for the 24/7 motor showing better HP and torque everywhere versus the stock Modena engine? Do you know at what rpm the reeds were opened? It would be interesting to see the results from testing the motor on a kart to see if the power improvement on the dyno yielded quicker lap times on the track.

I cannot discuss the powercurves here; I will leave that to Roland if he chooses to do so.
Like I wrote, and as you may have noticed in the pictures, the reeds were opened by a cam on the crankshaft because the use of a servomotor would not be allowed.
So at low rpm the reeds opened and closed with every revolution of the crankshaft. At higher rpm their inertia prevented them from completely closing and at even higer rpm they simply stayed open.

[Jannem]

Any program for comparing ports must compensate for for both the axial and radial angles.
Port chordal width * height is pretty much useless for anything meaningful.
Its the effective FLOW width* height * cosine up angle* open period ( for Specific Time Area ) that is used in EngMod.

Is that effective flow area the traditional "mean area" that is the area to the mid angle between opening and closing of the port measured from opening? Is that calculated directly from radial area (chordal not used in the calculation)? edit:with angle corrections?

Forgetting the mean area concept, wouldn't chordal width be the effective flow width? edit:when corrected for angles.

Edit: The way I thought the areas should be calculated:
1. Calculate chordal width of the port
2. Compensate that and height for axial and radial angles
3. From that, calculate mean area (based on mean angle between opening and closing) from opening of the port

Any help indicating where I went wrong would be appreciated.

[Frits Overmars]

Is that effective flow area the traditional "mean area" that is the area to the mid angle between opening and closing of the port measured from opening?

There is no 'mean area'.
The mean area was an approach, thought up by Gordon Jennings when he tried to explain the concept of time.area in his Two-stroke Tuner's Handbook of 1973,
when mere mortals had no access to computers. The 'mean area' approach provided some insight in the matter, but it was not exact.

Jennings based his time.area ideas on an SAE-paper written by Naito and Nomura, the engineers who developed the 125 cc and 250 cc four-cylinder Yamaha GP racers. These gentlemen did not sit on their findings but made them available to the world right after Yamaha withdrew from Grand Prix racing, which was very commendable and almost unheard of, especially for a Japanese company.

Naito and Nomura published time.area values for inlet, transfer and exhaust, and Jennings quoted those as the optimum values.
The inlet and transfer values were pretty close, but the exhaust value was far from optimal; it was only the maximum that could be achieved with a single exhaust port. If Naito and Nomura had thought of auxiliary exhaust ports, they would have come up with a much larger exhaust time.angle value and a big leap in horsepower.
Returning to Gordon Jennings: he apparently neglected the importance of blowdown time.area, which still makes itself felt to this day.
I do recomment reading his book, but one should never take anything written for granted (except when I wrote it, of course ).


EDIT: I tried to upload the whole book, but it's too big.

[F5 Dave]

I must find it, think I know which stack it is at the bottom of. He makes an amusing anecdote of the calculations that may be possible if one had access to a computer at home.
How easy it is to feel smart with the benefits of time (as I tap away at my supercomputer telephone lying in bed)

[Jannem]

There is no 'mean area'.
The mean area was an approach, thought up by Gordon Jennings when he tried to explain the concept of time.area in his Two-stroke Tuner's Handbook of 1973,
when mere mortals had no access to computers. The 'mean area' approach provided some insight in the matter, but it was not exact.

Jennings based his time.area ideas on an SAE-paper written by Naito and Nomura, the engineers who developed the 125 cc and 250 cc four-cylinder Yamaha GP racers. These gentlemen did not sit on their findings but made them available to the world right after Yamaha withdrew from Grand Prix racing, which was very commendable and almost unheard of, especially for a Japanese company.

Naito and Nomura published time.area values for inlet, transfer and exhaust, and Jennings quoted those as the optimum values.
The inlet and transfer values were pretty close, but the exhaust value was far from optimal; it was only the maximum that could be achieved with a single exhaust port. If Naito and Nomura had thought of auxiliary exhaust ports, they would have come up with a much larger exhaust time.angle value and a big leap in horsepower.
Returning to Gordon Jennings: he apparently neglected the importance of blowdown time.area, which still makes itself felt to this day.
I do recomment reading his book, but one should never take anything written for granted (except when I wrote it, of course ).


EDIT: I tried to upload the whole book, but it's too big.

Thanks, that's where I got this concept from. What puzzles me is that Engmod screenshots here quote "Mean eff area" which look a lot like the Jennings mean areas and reported STA values seem to be based on those. Perhaps for "universal" comparison purposes, even if the simulation wouldn't use them in any way?

[wobbly]

The inclusion of Mean Eff Area,I think was just an afterthought on Neels part - due to the legacy of Jennings etal,no one uses it.
What is important is that the STA numbers for the Blowdown and Transfers is well proven to work effectively for the vast majority of engines.
At the extremes of very low or very high specific output the problem is that we are dealing with a single dimensional simulation and by definition
this is ultimately limited in what it can achieve.
In any sim the STA number for the Ex is basically useless,as lifting the port floor and increasing the bottom corner rads has way more effect ( positive )
on eliminating short circuiting and increasing the duct velocity.
A real good example of a very high power anomaly is the RSA Aprilia sim.
In this the raw numbers dont seem to match what the dyno says is possible.
This is due to the fact that the transfers are pretty much described perfectly, but the Ex in the engine has a huge radius on the timing edge.
Thus the real Cd of this port is way in excess of what a simple EPO description would indicate.
But I have done hundreds of sims on a huge range of race engines and the end result if one realizes and uses small fudges to more accurately reflect reality,
has proven time and again to be very accurate.
A factor of around 12% drop going from the crank power result in the sim, will be seen on a DynoJet ( and yes I know that rig has a big inbuilt power fudge,but the comparison works way more often than not ).

[Haufen]

I think I already did tell, some time ago.
With the same obligatory 30 mm carburettor, the 24/7 engine produced 5 hp more than the standard engine, and revved 500 rpm higher.
The injected engine had good driveability; anything more would be for Roland himself to reveal.
I could invite Roland to tell us here but I'm not sure if he has sufficient English. We always speak German when Italians are listening, and vice versa (Roland is from Süd-Tirol, the German-speaking part of Italy). Besides, he is always pressed for time. And when he finds some time, he gives lectures to interested youngsters.
Attachment 331785 Attachment 331786

That sounds like a nice improvement! Do you happen to know if this is 5 hp more than an ideal kart reed setup, or if it is 5 hp more on the engine which was optimized for the 24/7 and then run with closed reed cage (and eg a crankcase compression ratio which had been optimized for the 24/7 setup)?

Then just tell him that there are many interested youngsters here on the board (I guess some on the outside and the inside, others more on the inside than the outside but who cares really). From what I recall there are several people on the board able to translate the occasional german or italian sentences or words. Should be manageable I'd say.

[peewee]

heres what I have so far, 3.5" inside the existing arm. probly start welding tomorrow. no turning back now so don't say it will break and ill wreck

[Lightbulb]

Remember one test with first piston and Rygerised Ns 250 cylinder with sleeve from my racing days.

Raised boost windows, halfway between Ex open and main transfers open. Started and it feels very different, something very reactive, and little more revs.
Outside was cold April rain, so I cant test on road and decide to rise even more, just 1 mm after Ex open. Started it and immediately feel engine laziness. It revs, but not fast as before. On the road was slow acceleration with terrible noise. But maybe without pipe would be different. So feel sorry, that not tested with with halfway boost.
Piston in photo from std. engine, just for better view

With your work so far, have you equalled the power of the std 125 yet?
Early days I know.

Neil

[Jannem]

The inclusion of Mean Eff Area,I think was just an afterthought on Neels part - due to the legacy of Jennings etal,no one uses it.
What is important is that the STA numbers for the Blowdown and Transfers is well proven to work effectively for the vast majority of engines.
At the extremes of very low or very high specific output the problem is that we are dealing with a single dimensional simulation and by definition
this is ultimately limited in what it can achieve.
In any sim the STA number for the Ex is basically useless,as lifting the port floor and increasing the bottom corner rads has way more effect ( positive )
on eliminating short circuiting and increasing the duct velocity.
A real good example of a very high power anomaly is the RSA Aprilia sim.
In this the raw numbers dont seem to match what the dyno says is possible.
This is due to the fact that the transfers are pretty much described perfectly, but the Ex in the engine has a huge radius on the timing edge.
Thus the real Cd of this port is way in excess of what a simple EPO description would indicate.
But I have done hundreds of sims on a huge range of race engines and the end result if one realizes and uses small fudges to more accurately reflect reality,
has proven time and again to be very accurate.
A factor of around 12% drop going from the crank power result in the sim, will be seen on a DynoJet ( and yes I know that rig has a big inbuilt power fudge,but the comparison works way more often than not ).

Thanks, this is helpful to compare the results. One thing I immediately noticed comparing my 60cc single ex.port to TZ's single exhaust port 125cc with similar bore/stroke ratio, that single ex.port gets progressively better with decreasing displacement. Probably not big news for the pros, but enlightening for newbie, like myself.

Did a quick comparison between 125cc vs. 60cc with differing bore/stroke combos and ex.port widths. Used simply port width % of the bore and 10% of stroke height, assuming port position to be same vs. stroke.

128cc with 1.08 B/S, 74% port produces same area/cc as 60CC with 1.13 B/S and 58%.
Square would compare to 60% and 0,86 B/S to 63%.

If both are 70% ports, area/cc is about 40% bigger in the 60CC.
If you compare the 60CC with 70% port to square B/S 50CC with 70% port, the 50cc has 20% more ex. area/cc for only 20% less displacement. Square 40CC with 70% port would have whopping 40% more area/cc than the 60CC mentioned.

It seems also that if you are inclined to increase displacement of single ex.port engine either by boring or stroking, the stroking would be beneficial from ex. perspective, although more challenging for other timings. From transfer flow perspective, it's not so easy to say which one would be better...
Of course, it's been discussed here often that square with good transfers and triple exhaust is the way to go, if you get to choose. Emphasis on the triple ex increasing with increasing displacement.

[Frits Overmars]

Do you happen to know if this is 5 hp more than an ideal kart reed setup, or if it is 5 hp more on the engine which was optimized for the 24/7 and then run with closed reed cage?

With the same obligatory 30 mm carburettor, the 24/7 engine produced 5 hp more than the standard engine...

just tell him that there are many interested youngsters here on the board... Should be manageable I'd say.

Just what would you manage? Rolands spare time? I'm sure he will be very grateful if you can find him a couple of free minutes now and then .

[Haufen]

Just what would you manage? Rolands spare time? I'm sure he will be very grateful if you can find him a couple of free minutes now and then .

Just making sure I understood correctly. An increase in performance of 11% in a competition engine is not peanuts.

I was referring to the language barrier, if there should be any. And I was thinking that, if he finds time to educate others, he might as well do it on this board from time to time. The ratio between the number of people he can reach per minute of time invested is quite good.