ESE's works engine tuner

[TZ350]

Avalon on the 600 at Mugello.

http://www.nzsuperbike.com/2013/04/a...-in-italy.html



Former New Zealand 125GP and 125TT champion and 2012 Italian Womens Championship Runner up Avalon Biddle decided to enter a round of the "Masters Cup" at famous Mugello circuit in Tuscany. This was Avalon's second race for the year at the famous circuit. The previous outing ended up with a crash , but this time was different. Starting from 15th on grid the Auckland charger cut her way to fourth place , then was awarded third after the winner was disqualified due to failing a tech check. Here is Avalon's report.

Starting from the fifth row in the rain for the race on Sunday I managed to avoid the chaos on the opening laps and settle into a rhythm, picking up many positions. Most of the race I was in a great battle with 4 or 5 riders but eventually I made a gap from that group and was comfortably in 5th place. Then on the last lap I started to catch 4th position so I pushed harder and did my fastest lap of the race,catching him just in time to get in the slipstream and overtake him at the finish line to grab 4th place by 0.01 of a second. That lap was only one tenth of a second slower than the fastest lap of the race overall. Later we were called to the official’s office to pick up the trophy for 3rd place because first position had been disqualified after a technical check on the bikes.

[F5 Dave]

Actually the dodgy engineering to hold the engine in is Dave's or one of Dave's bum buddies. From what I understand RMS Eng employs a higher standard of engineering.

RMS engineering did the tuning work on the engine. And quite a nice job he did. Few more things I would like to change but reliable track time is still more valuable at this stage.

Yeah that's how I got it as raced by Jay so don't blame me. Glad you've got it going.

[TZ350]

Wobbly, can you talk a bit about diffuser angles, ok, we are searching for the widest, lowest pressure around bdc, but in a pratical way...

I to am interested in that.

There also may be some more interesting pipe info here.

I have been trying to find the posts that talk about pipes and collate and edit them. There is heaps of it and pages 620 630 640 650 660 670 680 690 700 730 740 and 750 have un edited collections of raw material. If your interested in expansion chambers they are worth a look. Pages 710 and 720 talk about crankcase volume and inlet length.

[goose8]

Attachment 282671

Garry riding Speedpros 30hp MB100 in leg two looked to be the likely winner of the Dominic Howe and was laying down some super quick times until the rear shock came apart, dumping oil onto the rear tyre.

During the day Garry smashed the previous lap record of 29.4 with a bunch of 29's then a couple of 28.8's.

I would just like to point out that the shock is NOT a WP rear shock just a sticker to make it look like one, its a Dnm shock which works really good when the oil stays on the inside.

[TZ350]

Wobbly, can you talk a bit about diffuser angles, ok, we are searching for the widest, lowest pressure around bdc, but in a practical way...

Hi RomeuPT, Husaberg has just now reminded me, that he had posted Frits's pipe design spread sheet before, it could be worth a look.

Anyway this is a better one based on a simplified Frits Overmars design.

[RomeuPT]

Hi RomeuPT, Husaberg has just now reminded me, that he had posted Frits's pipe design spread sheet before, it could be worth a look.

I have looked and readed that info about pipes twice. Very Usefull.

Thing is, when I was using the demo Expansion Chamber Design Prog (http://www.bevenyoung.com.au/mota.htm) that is very used here and having all the Honda desing's in the table I notice that Mota makes ultra sharp final difuser cone, so the previous exhaust's I builded all have around 11º degree difuser angle, the mid section is longer, and the difuser starts later than the 30/33% rule of thumb.

Other thing is all Honda Exhaust have the last difuser the steepest one, and Aprilia uses the other concept of biggest and longest middle difuser, I would like to know if anyone used a pipe in Honda RS with the Aprilia type.

I don't want to force everthing you know, just discuss the angles and lenght's.

Here Mota example
Regards

[TZ350]

I am interested in this too, as I am a bit of a beginner at pipe design and would like to know more.

[wobbly]

Here is the hell RS125 pipe design that has basically everything I know embedded in its concept, the 800mm length is for a 200* Ex only with a
proper ignition curve and powerjet switching..
The first 25 mm is an oval transition flange ( 41 by 32 ) in the duct, out to a 41 header.
The stinger nozzle is 23.2 with 25 stinger pipe.
Dual stage header, and steep mid diffuser create the deepest and widest depression around BDC at 13,000, with tons of overev power.
The 120mm Honda and Mota pipes wont even get close, especially with the final diffuser being the steepest,it creates the Ex port depression way too late in the cycle
to help at the natural peak of a 200* Ex around 13,000 and into the all important overev past 14,000.
Several details can be jigged to work better than this design, but thats for you guys with a good code to work with to figure out from looking closely at the pressure ratio traces.

[RomeuPT]

Here is the hell RS125 pipe design that has basically everything I know embedded in its concept, the 800mm length is for a 200* Ex only with a
proper ignition curve and powerjet switching..
The first 25 mm is an oval transition flange ( 41 by 32 ) in the duct, out to a 41 header.
The stinger nozzle is 23.2 with 25 stinger pipe.
Dual stage header, and steep mid diffuser create the deepest and widest depression around BDC at 13,000, with tons of overev power.
The 120mm Honda and Mota pipes wont even get close, especially with the final diffuser being the steepest,it creates the Ex port depression way too late in the cycle
to help at the natural peak of a 200* Ex around 13,000 and into the all important overev past 14,000.
Several details can be jigged to work better than this design, but thats for you guys with a good code to work with to figure out from looking closely at the pressure ratio traces.

So this work on the Honda too. One less confusion. Thanks Wobbly.

For this top bmep engines we use 14º baffle angles, right, and if we go for slower less reving bikes, should we decrease this angle right? I have seen an amount of longer pipes (both handmade and aftermarket), like 950 and 1000 mm lenght for bikes who get peak power around 9k/10k rpm that have short baffles, like the ones of RS lenght, and the YZ and CR 125 have very long baffles. So I guess someone is doing a really bad job.

Made an Exhaust for a friend with a DTR 125 (peak at 9500/10000), using one 235mm 12,1º baffle, worked better against a known good aftermarket exhaust, my friend already solded the aftermarket pipe....

Now we are having fun making some drags on sundays

Regards

[wobbly]

The position of the start of the mid diffuser is the key to making top end and overev power.
Earlyer Aprilia and Honda designs had the steep diffuser starting right after the header, but this pulls the Ex depression down too early around BDC.
It works alot better for power production to space the main cone further along, and make the angle steeper to promote higher depression values by using a shallow last diffuser angle.
This also increases the main body volume.
I have been making the first and last diffussers around the same angle, just coz it feels right, and the sim says fill your boots.
Steep rear cones will work on any engine needing a high specific output, but you must have a digital ignition and powerjet switching, to stop the fast powerdrop off past peak
that the short cone will naturally create.
A longer rear will suppress the peak value and allow more natural overev characteristics without digital trickery.

[Dutch Fisher]

Wobbly,

Say if you had a single angle header and a steep first diffuser and then made that section by blowing it, do you think that the smearing of that angle would help make the wave "stick" thru that section change.

Have you tried it?

[teriks]

Thanks Wob, two really interesting posts there

[wobbly]

I also believed what I had been told previously ,that large changes in initial diffuser angle would cause flow separation and massive turbulence due to choking.
I built a heap of pipes to come up with a new design for CR125 Moto in SKUSA racing.
One of the tests was to try a design similar to the older Aprilia, with a very steep diffuser directly after the header.
This pipe made good power, but i was sure that if I added a short 25mm section ( the length of a bend segment in the U bend ) between the header and the main diffuser, with
only 1/2 the angle change - it would make more power.
Sadly no free lunch, it was worse by a small margin - bugger, another wives tale down the dunny.
I went on to discover the relationship of best power production, to the shape of the depression waves amplitude around BDC - was super critical to where the main diffuser started.

[Dutch Fisher]

Looking at the RSA125 tubo-102 pipe, Jan Thiel has gone for a three angle reverse cone.

What's your thoughts on the thinking behind that?



Have you got an example of a critical BDC depression wave?

[Forgi]

There are two factors in play with the tripple port setup.
You have drawn them correctly with 68% main port width, as this allows greater blowdown area to be gained via the aux ports.
Out at 72% that has proven to be approx the reliable max width, you loose some blowdown, and gain total area. ( not relevant at all ).
The problem is that even at 68% you cannot run a flat port roof with 8mm corner radi, as the ring life will be zero.

Secondly is that it has been proven in many dyno sessions that having all 3 ports open together looses power.
I can only explain this as a function of the fact that the effective duct length from the outer corners of the Aux is alot longer than that from the main port
mid point to the header.
Thus you get a smearing of the initial wave amplitude ( wider but lower intensity ) as it exits the cylinder into the duct during blowdown.
This reduces the effectiveness of the expansion phase, creating less depression around BDC, and less plugging efficiency as the piston closes the port.

It would appear that having a 68% main port opening first gives a good, high amplitude wave action in the pipe, then the Aux STA gets the blowdown pressure dropped as much as is possible prior to the Trans opening.

A few pages back was a drawing I did years ago of a T port with the outer edges higher than the mid point, thinking that this would ameliorate the duct length issue, but later
testing proved it didnt work well at all.
So by inferrence even lifting the Aux higher than the main wont fix this issue either in a 3 port.

Ok Wobbly, I understand...thank You!

Well, I saw your drawing with the T port. It is very strange that it doesn't work although it would be logical.

And what is more surprising to me is that the 3 ports opened together causes power loss. According to your dyno measurements how much is that waste?

In my opinion the problem might be if the aux ports are opening earlier than the main port (in case of a T port the outer edges are higher) the flow goes towards the aux ports and when the main port opens the flow turns to it with a poor efficiency. I don't know is it clear or not but here is a drawing.



This would be an explanation why does the power reduce if the 3 ports are opened at the same time.
But maybe I'm wrong...

Well if the distance between the aux and the main ports is bigger or the angle of the aux ports is bigger then the 3 ports can open together cos there is no effect on each other...