ESE's works engine tuner

[Grumph]

[QUOTE=TZ350;1130250437

So it looks like, how steep you can make this angle without encountering flow separation is one of the major things that will determine how much power can be wrung out of a rotary valve 2-stroke limited to a 24mm carb.

It doesn’t necessarily have to be motorcycle related, if you have a few smarts pretty much anybody can find Goggle clues that help in tuning racing 2-strokes and getting the best out of any sort of performance engine.[/QUOTE]

Eight degrees used to be the magic number...but I assume the people modelling flow dynamics may have moved this on a tad....

[TZ350]

Eight degrees used to be the magic number...

Was that eight or sixteen included angle?

In the literature there is quite a range and I have been finding it confusing trying to figure out if the quoted figure for the divergent section means diverging from the centre line or is the included angle of the cone if they don't also include the datum.

I expect the max angle possible is velocity dependent, it would be good to know what current thinking is regarding divergent cones and the typical velocities found in 2-stroke inlet tracts.

[2T Institute]

With IPO at 148 before will be hard to spread the power out(without a PV), a cheap and cheerful way of moving the disc timing is find how many deg 1 spline is, and juggle it around from there. A A100 we tested had very late closing with 120 IPO sacrificed some top end to pump up the mid when working with a 4 speed box. Has mid and a ton of over rev

[Grumph]

Was that eight or sixteen included angle?

In the literature there is quite a range and I have been finding it confusing trying to figure out if the quoted figure for the divergent section means diverging from the centre line or is the included angle of the cone if they don't also include the datum.

I expect the max angle possible is velocity dependent, it would be good to know what current thinking is regarding divergent cones and the typical velocities found in 2-stroke inlet tracts.

I always assumed from the context that it was divergence from the center line - ie 16deg included angle.....but I could be wrong....

[rgvbaz]

TeeZee,

I noticed that you are using two different flow widths for your inlet port. Exactly how I have been doing for ages until someone pointed out to me this bit in the instructions for Dat2T.

"Note: Even though the input and the following picture shows that the top and bottom flow widths can be different the software does not yet allow this and the users has to use the same value for the top and bottom flow widths."


I think you could use the average of the two flow widths to give you the same are of the trapazoid shape?

Dave

[TZ350]

"Note: Even though the input and the following picture shows that the top and bottom flow widths can be different the software does not yet allow this and the users has to use the same value for the top and bottom flow widths."

I think you could use the average of the two flow widths to give you the same are of the trapazoid shape?

Dave

I didnt know that, I thought I was doing the right thing, thanks for the heads up Dave.

[Frits Overmars]

....The design aim is a big inlet port, short inlet tract and a divergent angle joining the two thats not so steep that it promotes flow separation.....

You can't have it both ways, but you can get close by compromising. Avoiding flow separation will lead to too long an inlet tract, and a very short tract will invoke a lot of pressure loss through flow separation. The best way is to accept some separation and the only way to try this out is with a running engine (unless you have access to a pulsating flow bench or a very powerful CFD program).

Eight degrees used to be the magic number...but I assume the people modelling flow dynamics may have moved this on a tad....

Flow people may be getting ever better, but changing the laws of physics is still a bit beyond their power....

Was that eight or sixteen included angle?

That was eight degrees included angle. But for your purpose you might want to start with 10° and then gradually try larger angles.

I expect the max angle possible is velocity dependent

You are on the right track. Approaching this scientifically, there is no fixed maximum angle beyond which flow separation will occur. The angle depends on the expansion behaviour of the gas. Expansion in the flow direction means increasing particle velocity; expansion perpendicular to this direction means the gas is filling the whole cross section of the diffuser. The ratio of these two expansion directions and velocities dictates the ideal shape of the diffuser, which will look like a horn.

[TZ350]

Thanks ....

[TZ350]

.
Av smokes em at Tokoroa.

Just had a race report.

Race 1 Av starts of the back of the grid, works her way through the field and takes the win.

Race 2 Av starts from row one and wins again.

Race 3 Av takes the win after lapping the entire field including the current F4 GP champion.



Attachment 256696
Av and Chambers at Taupo

Av's bike was prepaired and tuned by Chambers, from Team ESE.

[cotswold]

.
Av smokes em at Tokoroa.

Just had a race report.

Race 1 Av starts of the back of the grid, works her way through the field and takes the win.

Race 2 Av starts from row one and wins again.

Race 3 Av takes the win after lapping the entire field including the current GP champion.



Attachment 256696
Av and Chambers at Taupo

Av's bike was prepaired and tuned by Chambers, from Team ESE.

Nice,,
Go the 2 strokes!!

[F5 Dave]

That's fantastic news, but mainly 'cause it means she made it there & thus took my tyres.

Well I've been having a bear of a time on the dyno. My MB just won't pull consistent runs. Now I know the cases leak due to incompetent welding many years ago despite gluing them together & new crank seals (I spent a couple of hours on the mill today on new cases).

But the behavior on the dyno is queer. it is making peak power at 10,000 & falling off a couple of hp or lots & ign trace goes. When it wasn't running as well peak power was 12,200. That is what it is tuned for & hits it.

I changed the ign as the NF4 RS igns are often dodgy, but no better, in fact worse. But the odd thing is it runs up better often if I start the run from 4000rpm. And in an 'all gear' run it occasionally pulls through & makes power & that gear curve is much wider than the rest. It does make a bit of a noise on the run & seems to pass through the gear a bit quick.

But a slipping clutch doesn't behave like that, I've had a H100 (same as MB clutch) slip & they tend to slip a bit when cold & lock up. Or just stay slipping, but from low revs. Now I have a Green modified pack which handles his 30hp with a touch of preload on the std springs.

I did have an issue when I first ran the bike on a long high gear cct as it slipped and I had to be careful how I applied the power, then as it got warm it seemed better. I made some spacers & preloaded it so it coilbinds just as the lever touches the grip.

As I lay awake (you may notice the timestamp is 4:30am) I am pondering the leaking cases. . .but; what I think I have created is a consistent action clutch that slips after a certain level of power - that is made after 10,000. Time for new plates & retry. Or stiffer springs.


Or try & think of a new hypothesis as why a 4,000 rpm run or an all gear run makes it carburete better at 12,000. Not that the slow rev start should have much effect on the clutch, but who knows?

[bucketracer]

... say two bucket racers, a low power/high torque bucket will only beat out high power/low torque bucket if the race is short (initial acceleration is higher for high torque) ...

Could be the reason that FXR150's are so good from the apex to the first few bike lengths out, often being able to get their wheel in front of a stroker.

... Now, of course, the ultimate goal is to have a high speed high torque bucket (i.e. a torque curve that is flat, and at flat at the maximum torque). But that is a higher power bucket anyway, because of the combination of high speed and torque.

Cheers,
FM

Attachment 256755

A flat torque curve typical of the Team ESE bikes.

[TZ350]

Changing the inlet tract angles by having a bigger rotary valve disk and smaller port window.

Attachment 256757

I feared that the 11.4-15.2-16.7 deg were too steep and would promote flow separation and reduced bulk flow.

Attachment 256758

So it looks like, by using a larger rotary valve disk I am able to have a smaller port window and shallower divergent angles 10-10.7-10.9 but the same STA as the bigger port because the smaller one will be fully open for longer at the larger radius.

The EngMod2T simulator is great for figuring this stuff out.

[Gigglebutton]

.
Av smokes em at Tokoroa.

Just had a race report.

Race 1 Av starts of the back of the grid, works her way through the field and takes the win.

Race 2 Av starts from row one and wins again.

Race 3 Av takes the win after lapping the entire field including the current F4 GP champion.



Attachment 256696
Av and Chambers at Taupo

Av's bike was prepaired and tuned by Chambers, from Team ESE.

Thats one very homely looking Brolly Dolly behind Av :-)

[Gigglebutton]

.
Av smokes em at Tokoroa.

Just had a race report.

Race 1 Av starts of the back of the grid, works her way through the field and takes the win.

Race 2 Av starts from row one and wins again.

Race 3 Av takes the win after lapping the entire field including the current F4 GP champion.



Attachment 256696
Av and Chambers at Taupo

Av's bike was prepaired and tuned by Chambers, from Team ESE.

Thats one very homely looking Brolly Dolly behind Av :-) Well done Avalon & Cully