ESE's works engine tuner

[husaberg]

Yea well Lozza, why the fuck do you think im a wheelchair, doin exactly that shit is exactly why.
But yes it is cool when others appreciate the effort and sweat that went into the 400.
The Bricky paid good money - he has already had a heap of fun on it, what more could a guy ask for from a toy.
His wife says is the best thing that has happened to him , apart from the kids, and they are debating that now.

Wob i was looking at one of Mikes video's and came across the NS400 with the CR125 top end was it finished looked kind of neat in the RGV frame.



I always kind of thought the NS400 was a little underrated.


Shame they arn't Crankcase reed.
Photo of the cabbage tree in the House paddock.thought it might have blown down by now. Sorry its fuzzy taken from my cell.

[Forgi]

Hi Everyone!

I'm Balazs from Hungary. Dear Fritz, and Jan nice to see you both of you here as well!

Well, I have read the comments til this moment, but now I'd like to ask some questions.

I have been studying the work of the exhaust nozzle for a long time, so I'm very glad that Wobbly wrote about it in details.

Wobbly!

Is it possible that the cause of the '75% rule' is that after the opening of the exhaust port the positive preassure in the exhaust port/duct lasts until 55-60 degrees, and then the diffusor starts to work, so the suction will be determinative? This area of the exhaust port at 55-60 degrees is the same as the exhaust duct's area should be (cc 75%).

If the presumption is right the exhaust port's lower edge doesn't have to be at ATDC 180 degrees, it would be enough at 135-145 degrees. In this case the proportion of the effective exhaust port area and the exhaust duct area would be 1:1. Of course the shape of the port is not the same and there is some important factors as well, but in general the abovementioned are right, aren't they?

By the way what is your opinion, where the exhaust nozzle has to be, how far from the exhaust port? And what about the exhaust duct? It has to narrow gradually all along, or is it ok, if it is 1:1 and only on the last 10-20 mm narrow to 75%.

TeeZee!

Have you tested this nozzle? About a year ago I read that it was planed to make it, but I haven't seen dyno test about it.

[TZ350]

... the exhaust port's lower edge doesn't have to be at 180 degrees ATDC ...

Hi Balazs, I remember seeing a post some place where Jan talked about getting more power (reduced short circuiting) from razing the exhaust port floor. Your idea makes sence to me, hopefully Wobbly will be able to tell us more.

TeeZee!

Have you tested this nozzle? About a year ago I read that it was planed to make it, but I haven't seen dyno test about it.

No ... reliability issues have kept me busy, and now I am building a completely new lighter bike. I am planning two engine setups for it, one will be a water cooled 100 with CVT transmission and that will have an exhaust nozzle.

[wobbly]

The idea of reducing the duct volume was pushed along by Jan at Aprilia where they CNC cut the shape.
He lifted the floor, but more importantly the bottom corner radius was increased, this also reduced the volume, and helped reduce short circuiting from the A port.
With the cosine of the 25* down angle taken into consideration, I would guess the area at the port exit was quite small in the cylinder.
I have found that the 75% rule work OK, as does making the duct exit area the same as the main port area only ( often works out to be the same value ) but that the exit area must include
the 1/2 moon cutouts, or be very oval shaped, depending upon 3 port or T port.
I dont know how far you could take this idea, I did think of having a Honda type powervalve plate in the floor of the duct, that lifted up, to reduce the area
outside the port, and could be servo driven,along with - or independent, of the main valve.
Changing the volume affects the HelmHoltz frequency, as does changing the length, but what is the optimum - only testing different lengths, and adjusting the pipe accordingly
would find out.
As it stands, the nozzle being part of the flange is all we can do with an existing cylinder.
Welding up the last part of the duct works OK, but I always try and get as far up into the duct as I can to reduce the vertical height gradually, and widen it to get the Aux ducts to flow better.

The NS400 is hiding in a corner somewhere 1/2 finished, Jarred has financial issues that have taken a long time to resolve.

[2T Institute]

Yea well Lozza, why the fuck do you think im a wheelchair, doin exactly that shit is exactly why.
But yes it is cool when others appreciate the effort and sweat that went into the 400.
The Bricky paid good money - he has already had a heap of fun on it, what more could a guy ask for from a toy.
His wife says is the best thing that has happened to him , apart from the kids, and they are debating that now.

Bikes are never about being sensible Hey Wob something interesting I realised while watching a Aston Martin Mega factory doco on youtube, designers were talking about the "golden ratio' which has been used since they built the Parthenon. The ratio of 'anything' should be 1.612:1 just under 1/3 to 2/3rds, designers say everything conforming to that has natural beauty and looks 'right'. Your header to t/l , diffuser to t/l and what to do with the remainder seems to conform with that 'golden ratio'.


http://en.wikipedia.org/wiki/Golden_ratio

[dinamik2t]

Wob, the RSA duct exit must be 39.2mm in equiv. diameter, from Frits' aprilia 102 pipe schematic

From another cad drawing posted in pit-lane by Francis Payart -which I cannot find by any means at the moment-damn research - the exit is ~33x46mm tallXwide, auxiliary ½ moons included.

I cannot find a way that will make the main+aux ports around 1600mm², in order to have a duct exit of ~75% of that. The total of the ex ports would have to be around 45mm of equiv. diameter! Seems huge

Actually, when modeling the older apc ports, it would seem it is more like 40.5 ports - 39.2 duct; or ~95%. That % would be even bigger for the bottom-risen/narrowed apf port.

Could it be that the nozzle effect is only duct-volume related and not duct-exit% related?
Or perhaps the auxiliary ½ moons are excluded from that area%.. -which you have confirmed in the past it's not the case, I think.


p.s. I don't mean to insult you Wob; you have my respect. I am just discussing my thoughts, eh..

edit: Here it is.. Just had to go through fpayart posts et voilà:

[wobbly]

The 75% number came about from doing alot of testing on flanges and duct shape for a customer building aftermarket RS125 cylinders.
The best beta cylinder ended up with an oval at 41 by 32mm.
It was about this time I started doing alot of sims using Neels code, and it struck me that so many engines went the best - on the screen and on the dyno with that 75% idea.
Then I later confirmed that an oval to round transition within the spigot worked the best.
I have not had a chance to try Jans idea of continuing the 1/2 moon cutouts down into the header, making that somewhat oval as well.
Maybe Frits could shed some light on the area at the flange testing done at Aprilia.
Yes of course you cannot separate out the duct volume from the area at the flange - the two go hand in hand, but which one is the chicken and which is the egg?? I do not know, nor care, at this stage.
All I do know is that dozens of customers and hundreds of others have used the 75% rule of thumb and it works every time - way better than the over 100% seen so often..
Some engines like more - some less, but there have been, and will be even less in the future, those who can get even close to the specific output of the earlyer model Aprilia and will need a detailed analysis of EXACTLY what is best
for any given engine.
Try this for another rule of thumb - I have found that most full noise RACE engines built with single exhaust ports, like the exit area at the flange ( and thus the header diameter ) at 90% of the EFFECTIVE port area.
Again, this seems to work every time ( TZ350 ) but some like even less if the port is VERY high, like big drag race Kawasaki tripples etc.

[husaberg]

http://sharkshifter.com/zc/index.php...ort=20a&page=3
above is a random link not the TZ one

depending on your set up you may need to remove an extra http://

this triple port seems to be a great idea mmmmmm.......I wonder if it will catch on..................Maybe next week.

Wob, the RSA duct exit must be 39.2mm in equiv. diameter, from Frits' aprilia 102 pipe schematic

From another cad drawing posted in pit-lane by Francis Payart -which I cannot find by any means at the moment-damn research - the exit is ~33x46mm tallXwide, auxiliary ½ moons included.

I cannot find a way that will make the main+aux ports around 1600mm², in order to have a duct exit of ~75% of that. The total of the ex ports would have to be around 45mm of equiv. diameter! Seems huge

Actually, when modeling the older apc ports, it would seem it is more like 40.5 ports - 39.2 duct; or ~95%. That % would be even bigger for the bottom-risen/narrowed apf port.

Could it be that the nozzle effect is only duct-volume related and not duct-exit% related?
Or perhaps the auxiliary ½ moons are excluded from that area%.. -which you have confirmed in the past it's not the case, I think.


p.s. I don't mean to insult you Wob; you have my respect. I am just discussing my thoughts, eh..

edit: Here it is.. Just had to go through fpayart posts et voilà:

I always had suspicions that one one looked at what i posted

[dinamik2t]

Husa, no need to have suspicions on being neglected!
It just happened to first see those pics in pit-lane, so automatically my memory was linked to that web-page, in which I knew I could narrow down the poster's id and find them easier.


Wob, thanks for the patience of re-explaining everything. After all, you are right about achieving aprilia's specific HP...
It would be interesting to hear more about the paradox, but if we don't it 'll be ok too.


By way, I believe that the chicken came from one egg (or the egg came from one chicken). Evolution.

[Frits Overmars]

The 75% number came about from doing alot of testing on flanges and duct shape for a customer building aftermarket RS125 cylinders....It was about this time I started doing alot of sims using Neels code, and it struck me that so many engines went the best - on the screen and on the dyno with that 75% idea.

As an empirical rule Wobbly's 75% of the total exhaust port area works very well. But I prefer to base the port exit area calculation on the blowdown area, not on the total port area. The drawings shown above by Husaberg, give a good indication of the port exit area; below you will find the Aprilia's blowdown area (and the angle.areas for blowdown and scavenging).

you cannot separate the duct volume from the area at the flange - the two go hand in hand, but which one is the chicken and which is the egg?? I do not know, nor care, at this stage.

I bet you do care, Wob . I think the duct should just be able to handle the flow during the blowdown phase; any more cross section area in the duct only increases its volume which should be avoided.

Try this for another rule of thumb - I have found that most full noise RACE engines built with single exhaust ports, like the exit area at the flange ( and thus the header diameter ) at 90% of the EFFECTIVE port area. Again, this seems to work every time ( TZ350 ) but some like even less if the port is VERY high, like big drag race Kawasaki tripples etc.

Wobbly hits on an important point here: the higher the exhaust timing, the smaller the header diameter should be for a given rpm range. It would take me too far to explain the fundamentals here, but you can find the relationship in my 'simple exhaust concept' below.

[cookie1965]

There's been discussion in this thread about home made dynos. I got some sound advice regarding the Heenan and Froude water brake I have which I chose to follow. So I continued my plans to build an inertia dyno and then stumbled onto this:





Hoping to get it dug out of the blackberry bushes and to my house soon so I can start working on it! Haven't seen any progress pictures of anyone elses dyno projects, how are they coming along?

[Yow Ling]

Hi Cookie,
there are 3 new dynos around the place, heres mine
Mine and the GPR ones use Dynomite software and Im pretty happy with it
you could have that dyno going in about 1 hour

[Bert]

Hi Cookie,
there are 3 new dynos around the place, heres mine
Mine and the GPR ones use Dynomite software and Im pretty happy with it
you could have that dyno going in about 1 hour

Following previous comments; we are really happy with the performance trends' Dynomite interface and software.

[wobbly]

As always I have to agree with Frits analysis - tying the duct geometry to the blowdown is way more accurate - as this number is crucial to achieving the
power an engine will make in reality.
The Ex effective area is pretty much irrelevant, so having an empirical duct number ,based on an irrelevant dimension seems pretty short sighted, even if it is based on long term observation.
But reality gets in the way of desire, and busyness precludes the time needed to try and construct a good approximation for a duct based on Blow STA.

Yes I do care about the duct/area relationship, but as 95% of the time working on engines involves the huge compromises needed when modifying an existing, flawed design,
I again cant afford the time needed to work thru it.

Clean sheet designing is a huge challenge, as EVERY aspect is your fault, or your success depending upon the result, at least with an adapted design there are usually several loop holes for escape.

[husaberg]

Clean sheet designing is a huge challenge, as EVERY aspect is your fault, or your success depending upon the result, at least with an adapted design there are usually several loop holes for escape.

Engineering is all about making the right compromises (stole this phrase and i like it)

Design is unfortunately always a compromise the hardest bit is quantifying how to avoid the worst. Starting with a clean sheet makes you appreciate just how much is involved and what seems like an obvious flaw and first glace is maybe not as it seems and the designer was forced into it by some other aspect.
The other thing is when faced by a blank slate it is so much work.
It is sometimes easier (for my small brain at least)to fit something in to the fixed parameters of an existing design.
Which of course is a huge compromise?


The cleverest design is often as an afterthought seems so incredibly simple and blindingly obvious and offers the least amount of compromises where it counts. I also believe most often form and function are totally interrelated.

I can think of an engine from someone that was supposed to be an ace Race engineer that was copied entirely of another but as an afterthought he placed upside-down to seemingly mimic another design. Plus make it look "trick"
He it looked like in his rush to finish the job and get paid forgot to make sure the one important design aspect was up the right way.
Frits and Wob will have a pic somewhere i guess.