ESE's works engine tuner

[TZ350]

Bruce Anstey wins Lightweight TT, new record on Honda RS 250.

Great to see a Kiwi doing well on a 2T at the Island.

Neels sent me this link, very interesting read if your into DIY EFI.

https://klr650.net/forums/showthread.php?t=108393

Got my bike back together ready for the dyno but unfortunately I will be away for work in the South for a week or so. Maybe get to the dyno in two weeks time, fingers crossed.

[koenich]

Bruce Anstey wins Lightweight TT, new record on Honda RS 250. Interesting for RS airbox intake on right side.

that little thing is a GoPro Session I think...

[speedpro]

Those who are a little older may remember Bruce on his TZ here in NZ. Hill climb up Mt Vic was going good untill he highsided it or what about dicing with Robert Holden who was on the Bob Brown Ducati at Masterton. Pretty sure he was National champ on it at least one year as well. Or, not so motorcycle related, eating all the chocolate biscuits at DynoTech every time he visited, which was every day.

[chrisc]

When modelling a reed setup in DAT2T, how do I reasonably estimate the maximum tip displacement when there isn't a stopper plate?
Carbon 0.3mm reeds, vforce 4 sided block, 8 petals/reed block ports.

[katinas]

that little thing is a GoPro Session I think...

Yes, I am wrong, this is GoPro. Thanks

[F5 Dave]

Those who are a little older may remember Bruce on his TZ here in NZ. Hill climb up Mt Vic was going good untill he highsided it or what about dicing with Robert Holden who was on the Bob Brown Ducati at Masterton. Pretty sure he was National champ on it at least one year as well. Or, not so motorcycle related, eating all the chocolate biscuits at DynoTech every time he visited, which was every day.

I was talking to Chris when Bruce showed up on his mountain bike on one wheel. Slowed down, Tapped him on the shoulder with the front tyre and off again.

[teriks]

as a kid i had a control line plane with small cox engine. it must of been some 30yrs ago. i vaguely remember it using some kind of fuel from a small metal can like a liquor flask. to start it, it seemed like there was a spring on the back side of the prop and you would put the hook of the spring on one of the blades and turn it backwards to wind the spring. once you let go it spun the engine forward and would start

Perhaps it made more of an impression than you remember given your choice of username here.

Cox Peewee:

[TZ350]

Ages ago to increase the airflow through a class legal 24m carb I came up with the idea of a 24mm venturi section in a 24mm carb that had been bored oversize. The idea was that the larger front section acted like a flow straightener and by eliminating turbulence it would allow the venturi to pass more air. Whether it really worked like that I don't know but it did allow Team ESE to make much more power with the old air cooled 125's than people thought possible for the class.



Recently on an inspired whim I brought an old Kilt pumper carb from Ebay Japan. And found it had a larger bore with a 24mm venturi at the engine end, just like my modified carb.



The 24mm venture can be seen at the engine end of the Kilt carb. Seeing that Kilt have also done this leaves me feeling really vindicated and in good company.

It is not everyday that you find one of your original clever ideas was also one of the big boys tuning secrets...



Kilt make real flash pumper carbs for Kart racing.

[dark art]

. Seeing that Kilt have also done this leaves me feeling really vindicated and in good company.

Maybe pumper carbs are less sensitive to ventury speed to attaind good metering?

[guyhockley]

Great to see a Kiwi doing well on a 2T at the Island.

Mr Anstey is looking pretty good for the super bike race, too. Did a 125+mph on the YZR500. Possibly fastest ever 2 stroke lap?

[wobbly]

REED BLOCK MODELLING.
The front page of STA numbers gives you a recommended tip lift based on the petal length.
If you run the intake traces and see the reeds going spastic,ie wild changes in lift cycle to cycle, then the petal is too thin and hitting the ( virtual ) stop.

[chrisc]

Thanks Wobbly. This prompted me to more clearly read the help section on inlet modelling in DAT2T which has helped a lot. I also revisited a bunch of the posts you've done on reed valves before which helped some more.

I'm obviously modelling something wrong somewhere because I can't seem to get much predicted reed tip lift which is killing power in the sim. If I reduce the reed thickness from 0.3mm carbon to 0.25mm carbon the tip lift increases significantly and so does predicted power. I would have thought 2x narrow 0.3mm thick carbon reeds on each face would be plenty flexible enough.

[wobbly]

What is peak Hp rpm, and what is the reed 1st mode frequency rpm.

[2T Institute]

On my 50 engine, now fitted with a disc valve inlet, the transfers open at 114º ATDC, which means they close at 114º BTDC. My disc valve opens at 135º BTDC, so there is only a tiny window of 21º where the negative pulse from the exhaust diffusers can communicate directly with the carb.
We usually target this negative pulse to coincide roughly around BDC at peak power revs, so presumably this negative pulse, reflecting through the transfers, adds to the negative pressure caused by the rising piston to significantly reduce the crankcase pressure BEFORE the RV opens, so that when it does open, there is a burst of flow through the carb, which then quickly reduces to just the flow caused by the still-rising piston as the transfer ports close. I would have thought this uneven flow could cause difficulties with carburetion, compared with a reed setup that presumably allows a more consistent gas flow, starting as soon as the negative crankcase pressure is sufficient to open the reeds.

It seems to me then, that the additional flow through the carb resulting from the tuned exhaust should be longer in a reed engine, with less fluctuation than in an RV engine, so why does a disk valve generally enable more power?
Is that initial burst of flow through the carb actually beneficial rather than problematic?
Or is the better power perhaps more to do with better control of the closing point of the inlet offered by an RV?

So many questions, so little time...

There isnt any need for the diffuser to influence the carb at BDC, there isn't enough time for intake charge to go from the carb to the combustion chamber by the time the transfers shut. The low pressure in the diffuser at bdc is beneficial because thats where the transfers are fully open, pressure flows from high to low and if the lowest pressure is in the diffuser at bdc charge in the transfer ducts and just under that in the cases will want to go toward the diffuser.
Case pressure won't start to drop rapidly until the transfers shut. with reed engines the reed is the restriction a rotary has no restriction which is why a really well designed stuffer combined with petal thickness/width is so beneficial, so the inertia of the intake charge will keep the reed open for longer.

[chrisc]

What is peak Hp rpm, and what is the reed 1st mode frequency rpm.

14,000rpm, 28,218rpm when using 0.3mm thick reeds

EDIT: Screenshot of the reedblock except I just noticed I'd left 0.25mm reeds in