ESE's works engine tuner

[wobbly]

Stock the port floors were slightly above the timing edge, when I dropped the cylinder they ended up 0.2mm below,not a concern I would have thought.

Edit - also the rules dont allow " adding material " for KZ2 .

[FastFred]

It might be a 12A Rotary exhaust port but there is some interesting ideas about testing and port radiusing applicable to 2-strokes. http://www.yawpower.com/Flow%20Testing.html

Ages ago Bucketracer posted about port radius's, at the time I don't think anyone recognized its value or knew what size the radius could or should be or paid much attention except SS90 who seems to delight in any opportunity to derided Bucket for his internet based research.

Me, well I would like to know more about the dimensions of suitable radius's.

[kel]

Jan Thiel of the radius that the Aprilia cylidner has at the exhaust port roof to improve flow... there are also two differnt durations mentioned for the RSA exhaust, one is 202* the other states "196* without taking the radius into account", or something to that effect...

Interesting stuff. Perhaps Frits might expand on this.
When I read the pitlane thread sometime back I assumed the radius referred to was the radius top edge of the exhaust port as is done on most all exhaust ports to aid ring life, thus the auxilliaries were 196* in line with the lower edge of the top of the exhaust port (as if it was square edge at the top) while the highest section of port due to the top edge radius was 202*. But dmcca has read this as a radius cut horizontally into the exhaust duct itself, which from Wobblys post most definitely has a positive effect on power. Jennings raised this in his 2 stroke tuners handbook way back when - 1973 to be precise

"As regards the exhaust port, a secondary function is served by providing a bevel,
and radiused edges, around the port window. There is a very considerably contraction of
flow through any sharp-edged orifice, and such orifices may be made effectively larger
by providing them with a rounded entry. Improvements in flow in the order of 30-
percent could be had were it possible to give the port window edges a radius of, say, ¼
inch. Unfortunately, to do this would mean advancing the point of exhaust-opening a like
amount, which in most engines would result in a very radical exhaust timing indeed. It
is, on the other hand, often possible to carve just such a radius at the sides of an exhaust
port - although it is questionable that this radius would be as effective as simply widening
the port to the same extent. The radius approach does have the advantage of leaving
intact much of the metal around the port, which can be important: Thick sections of metal
tend to equalize cylinder temperatures and prevent the kind of local distortion that is such
a potent cause of piston seizure."

[F5 Dave]

I'd assumed the 196/202 thing was the Power valve only moved a small amount, but did it fast enough & only started from (ermm?) 10,000 or something like that.

[dinamik2t]

If I remember Jan's info correctly, AUX ex ports were 2mm below the main. Main was 196 plus that big radius, extending it to 202.
If the -2mm from the main are with the 202 duration, then AUX timing is around 83 or 194 duration. If it was with the 196, the they are 86/188.

The PV was 90/180 at 10000, fully open to 79/202 at 12000.

With a 54.5 stroke, each timing degree is about 0.5mm, so the radius from 82/196 to 79/202 is 1.5mm vertically.
From EngMod's CADing, the exhaust top edge radius could be around 60-70mm to be like that.

edit: removal of misleading pic

[dmcca]

Interesting stuff. Perhaps Frits might expand on this.
When I read the pitlane thread sometime back I assumed the radius referred to was the radius top edge of the exhaust port as is done on most all exhaust ports to aid ring life, thus the auxilliaries were 196* in line with the lower edge of the top of the exhaust port (as if it was square edge at the top) while the highest section of port due to the top edge radius was 202*. But dmcca has read this as a radius cut horizontally into the exhaust duct itself, which from Wobblys post most definitely has a positive effect on power. Jennings raised this in his 2 stroke tuners handbook way back when - 1973 to be precise
"

I'd assumed the 196/202 thing was the Power valve only moved a small amount, but did it fast enough & only started from (ermm?) 10,000 or something like that.

Hmm... Maybe I have mistakenly interpteted it in a different way to others... I know I was constantly trying to find an explanation for the RM250 experience of a few years ago and so when I read a couple of key quotes at pit lane (from people who should know!) I didn't question my initial interpretation of what they were saying. Rightly or wrongly it seemed to add up to me.

I will try to find the quotes and post them up here just to see how others would interpret them...

[dmcca]

Here we go...

Jan Thiel, p44 Pit Lane RSA125 thread...

"The exhaust port had a radius at the top, but this was more for the flow and not to avoid ring clipping.
We never had problems with the piston rings, the central exhaust port was not so wide."

When i read this i though that a normal curved port roof doesnt really do much extra for flow, its more about controlling the exhaust pulses and saving rings, so to me it made sense that he could be talking about a horzintal radius which would definitely have a big impact on flow.



Frits Overmars, p47 Pit Lane RSA125thread...

"Exhaust 202°, A-transfers 130°, B- and C-transfers 132°."




fpayart, p7 Pit Lane RSA125 thread Part 2...

Q: Will you tell us the final width and height of the RSA exhaust exit? (after some conversation regarding port widths)

A: The sizes are 39.5 width x 27.5 height (without the radius).
Now I can imagine your next request
The opening time is 196 ° measured without taking into account the radius.

To me this last bit sealed the deal... why would he give a height or a duration to the lower point on a normal curved roof radius (ie. the height to some point near the far side of the port roof)... he wouldnt, it doesnt make sense... i think think this adds further weight to the fact that its a horizontal radius blending inwards into the exhaust duct. This would explain the difference in durations listed by people who definitely know this engine. I guess the way the port acts is somewhere between the two durations, most likely determined by the exact dimensions or construction of the radius...


Also there is this...
Havent really read the detail but the pics reflect what i found on the RM250...
http://www.google.com/patents?id=iks...page&q&f=false

[kel]

Yes very interesting indeed. I have a spare cylinder that I hope to start working on as soon as my wrist has healed, the exhaust port is top of the list for what I'd do differently from last time. Hopefully Frits will expand on the use of the top horizontal radius and how best to put this into effect.

[jasonu]

I don´t think i do.
What upsets me is that people are reading my posts as the devil reads the bible.
And that expression 'geez' is to me an expression we use in Sweden when people are really really dumb.
I do not judgement people until they have proven themself dumb.
But in certain cases i might reconsider my rules from here on.

I´ll tell you a little bit of my 'history' and where i´m coming from to clearify that i´m no rookie:
I´m born 1970
started to tune my first moped, a Puch 'florida' at 12years of age.
I got that to run at the impressive speed of 40Mph, not bad for a guy that wasn´t even a teenager.(and only tuned 1hp products)
At 13years of age i ported and flowed my first FORD V4 heads.
Those became running so good that they were used in an Rallycar(SAAB 96)
Then it became a Zündapp, at 15 years of age, tuned that one to the point where the std conrod couldn´t take it anymore.
It revved REALLY hard with my bored out BING22mm carb, (bored out to 24mm)
this was 1985.(with homemade pipe)

Several engines has passed my fingers since then.
Snowmobiles,Rallycars,Offroads, all with good results.

In latest 10years i have been concentrated to port and flow different dragracing cars heads.
Often Audi 5cyl 2.2litre.
Which i have tuned to about 1100hp in engine.(Exactly 1132hp)
And often with MUCH broader powercurve than others.
I had myself an Opel(vauxhall) Kadett GTE wich i had converted to 4wd with an specially built turboengine from my theories.
This was quite cool,, i settled for about '700hp' as maximum and then finetuned everything to work as good as possible.
This ended up in the most hard running 2.3 litre(4cyl) engine i ever driven.
full boost already at 3000rpm, and had it all the way up to 8000rpm.
Boost was almost instant, no lag, at any rpm between 3k and 8k.

Latest acheivment is an Audi 80 quattro 1984 wich had a topspeed of 214.2Mph on standing kilometer,(1000m)

But somehow i got tired of all this hogging out 4 stroke heads, so i picked up 2stroke tuning again.
Now with skills i wish i had when i was 15 years old.

Through all this years of tuning, i have never used a flowbench. i often have to 'fight' with internet trolls that people CAN be born with talent, but i´m always loosing the keyboardwar *lol*.

With that said, i just wanted to say i got about 30years of experiance in enginetuning in my spine.

Rgds
Patrick

Pictures and or videos or it never happened. Seriously mate I am interested in seeing some of your work especially the Audi and Opel stuff you mentioned.

[speedpro]

With that said, i just wanted to say i got about 30years of experiance in enginetuning in my spine.

Rgds
Patrick

Geez some people are sensitive. I'll say it again - I'd like to see what power your engine is making. Not because I doubt (well maybe a little bit) what you are saying but because
I'm interested in most things that burn petrol, or methanol, or nitro and I want to know what it's doing, not because I want to put it down. There's nothing to be gained from that and no point to it.

FYI I have a 39 year old turbo bike that made 175rwhp with bent exhaust valves and I've ported alloy big block heads that when fitted to a steel bodied holden ute ran 6.9? seconds at over 200mph in the quarter.

I also consider a drag strip to be a track. It's short and straight but still a track.

[Drew]

I also consider a drag strip to be a track. It's short and straight but still a track.

Drag racing goes somewhere. Point A, to point B. Circuit racing goes round in stupid circles!

[Brian d marge]

I´m calm.

But i know of experiance that many people reacts strange when a 'newbie' on different forums is waving the big hammer.
I just wrote the last post to clearify that i am not dumb
And this thread with Frits many many tips and pictures have made me more certain of my work as i can see a lot of similar thoughts and similar ways to design different things on a twostroker as my own ways.

Rgds
Patrick

what measurement tools are you using for the port flow

Stephen

[Frits Overmars]

fpayart, p7 Pit Lane RSA125 thread Part 2...

Q: Will you tell us the final width and height of the RSA exhaust exit? (after some conversation regarding port widths)

A: The sizes are 39.5 width x 27.5 height (without the radius). Now I can imagine your next request. The opening time is 196 ° measured without taking into account the radius.

To me this last bit sealed the deal... why would he give a height or a duration to the lower point on a normal curved roof radius (ie. the height to some point near the far side of the port roof)... he wouldnt, it doesnt make sense..

Francis Payart's answer makes perfect sense. Besides, he should know, he bought the winning Aprilia RSA125 right after the last 125 cc Grand Prix and today he produces his own, very well-made copies of those cylinders for his 250 cc tandem twin FPE superkart engine.
The port in the cylinder casting has a timing of 196°. Then the upper edge receives a radius that lifts the timing edge to 202°. It's as simple as that.

[wobbly]

Yea right ok guys, lets quit dick measurements, and get on with posts that help others understand 2T workings.
By the way I built a racing lawnmower when I was 12 - does that count.

[kel]

The port in the cylinder casting has a timing of 196°. Then the upper edge receives a radius that lifts the timing edge to 202°. It's as simple as that.

Frits, for the purpose of implementing and testing this radius is there a ratio to apply based on area, timing, etc? Is 6deg effective timing the magic number to work towards in say 2 deg steps? In the attached drawing AP125-01 does the broken line above the exhaust port represent the area the radius is applied to?
Thanks in advance for your advice