ESE's works engine tuner

[RomeuPT]

The other small point I thought of later was that the drop down rear piston support tang,if shaped well also helps to deflect the reed flow sideways
toward the transfer duct entry area, and not allow most of it to migrate straight forward and hide under the piston.
I should temper my comments about reed flow at BDC somewhat in that when you watch the tip lift and case depression curves in EngMod
you see that the case going negative and the inlet going positive, if tuned correctly opens the reeds very quickly and soon after BDC,thus initiating
flow into the case when the piston is still hanging around " in the way ".
But again I emphasise it isnt the rising piston that creates the inflow in a race engine.

Many Thanks for this great share of knowlegde.

So, as fuel passes inside the open reed cage there should not meet a very big case entry or the flow velocity is lowered too much, then the fuel should go in the easier path to sit under transfer ducts. Is this right?

Concluding, we can't make a divisor for fuel to avoid getting much under the piston because of big and small end bearings lubrification!?

Many Thanks

[Grumph]

The other small point I thought of later was that the drop down rear piston support tang,if shaped well also helps to deflect the reed flow sideways
toward the transfer duct entry area, and not allow most of it to migrate straight forward and hide under the piston.
I should temper my comments about reed flow at BDC somewhat in that when you watch the tip lift and case depression curves in EngMod
you see that the case going negative and the inlet going positive, if tuned correctly opens the reeds very quickly and soon after BDC,thus initiating
flow into the case when the piston is still hanging around " in the way ".
But again I emphasise it isnt the rising piston that creates the inflow in a race engine.

So then, how important are holes in the rear of the piston skirt ? Do you place more importance on a strong signal from inlet port opening with a solid skirt - or use a very strong signal from the pipe to get as much mixture as possible into the cases via a 360 degree opening using a ported piston ?

this is assuming a non case reed motor....I ask because i like the 360 deg opening but it's necessary to "life" ported pistons to avoid a messy disaster....

[wobbly]

The amount of inlet flow capability varies from motor to motor with cylinder reed setups..
But I know for example in the RZ400 I had to make the Boyesen ports in the CPI cylinder twice as big and then use a Blaster type piston full of big holes
to get sufficient inlet STA to support over 100 Crank Hp.
That engine ended up making 96 RWHP and held up over 90 at 12,000 so when pushing the limits on a cylinder reed you have to use everything available.
Here is a pic of the Blaster pistons in 66mm bore, next to stock Blaster and RZ ,I had Wossner make them for the RZ and the TZ400.
Been reliable to over 500Km hard racing so far.

[wobbly]

Re the reed flow - yes keeping the reed box duct volume small helps keep the velocity high and in all late model engines you can see
the progressively smaller entry volume being redesigned year by year.
I have thought about making a pair of curved vertical guides in the reed box that would direct the flow from the outer reed petals ( in a 6 petal reed )
toward the transfer duct entries.
The centre petals then dumping flow onto the big end slot for lube - not had a suitable project yet to try this..

[jonny quest]

So what are your thoughts on making the cases as wide as possible on a case Reed motor? This NSR500 has the case Reed width almost as wide as the transfer ducts in the cases.

I have a cr125 that I'm doing and debating on how wide I should make the case Reed width entering the crankcase, and ultimately into the transfer ducts in crankcase

[jonny quest]

Another quick question, has anyone tried adding transfer ports under the exhaust port?

Vertical slots cut in the cylinder wall, that just cracked open at BDC.

I believe this would help piston crown cooling immensely.

[F5 Dave]

Read back a few hundred pages, it's been touched on.

[wobbly]

From what I have seen by various factories the development seems to have been toward reducing the area/volume in front of the reed tips as much as possible - at the expense of what you would think was a "good " flow
regime.
But along with that the Italians are lifting the duct floor higher and higher with it sloping upward and transitioning into the flywheel covers, just leaving a slot for lube.
This has also coincided with angling the carb upward, removing any bend in the inlet tract.
That has also given festerers like me endless fun with reed configurations - no longer do we need to bias the flow with differing stiffness and or backups on the top/bottom to
counteract the manifold bends deleterious effect on flow.

[jonny quest]

Read back a few hundred pages, it's been touched on.

The exhaust transfers?

[husaberg]

The exhaust transfers?

Yip think it was on pitlane as well.......

[TZ350]

Another quick question, has anyone tried adding transfer ports under the exhaust port?

Yes and No ... tried an exhaust port dam, seemed to work OK, as for the transfers under the exhaust port itself, good idea but from memory Frits reported that Jan Theil had tried it without success.

Is this what TeeZee is up to and Jan was talking about, raising the exhaust port floor and maybe fitting an extra transfer there too?

I would be very interested in the roof angle of the 6th transfer port thats under exhaust.

To make the raised floor work as part of an overall plan that was seen all the way thru by Jan at Aprilia, the area reduction at the port should be extended all the
way to the flange.
Making this oval, and reducing the duct volume all the way to the exit then works with the 75% area guideline for T or tripple port duct exit geometry.

The glued and screwed in port floor dam held up OK and the dyno results were better.

You work too hard, TeeZee. Leave out step 1 and step 3 and you'll end up with a clean bin and 37.7 rwhp

Yes, high temp epoxy to seal the plate. I fastened the plate in with screws, the epoxy was mostly for sealing around the sides and under the plate.The dyno results were posted here.

I remembered that Jan and Frits had talked about experiments where raising the exhaust port floor made more power by reducing short circuiting.

And by reducing the exhaust duct volume and to help guide the washed-through mixture back over the piston edge into the cylinder. Lenghten it up to the flange face and make a smooth transition, like Wobbly advised.

Tdc211 its encouraging to hear you have got good results with your 5mm dam, and Romeu its hard to measure mine with the cylinder off but it looks like the dam is about 6mm or so above the piston and still 5mm or so below the top of the transfers.

Well at least its good to know I am on the right track but I sure would like to know if this is the limit or if I can take it closer to the top of the transfers.

Attachment 292539

After 40 liters of fuel and hours on the dyno the exhaust port dam and Belzona epoxy are still there.

[F5 Dave]

Oh, maybe it was pitlane I saw it on.

[jonny quest]

Thank you for digging up those quotes. I'm familiar with raising exhaust floor. Been doing that for years. .. glad to see I wasn't alone. I came across it when I tried a different piston that had a shorter skirt. It opened up ex port at tdc. When I went back to other piston I found some power I didn't have before. Just dumb luck on my part

Hopefully Frits will see this and comment on the ex transfer. .. what it did when it was tried.

[TZ350]

Rob
I have uploaded the results to Mylaps: http://www.mylaps.com/en/events/1012834)
I have also updated the link on the Bucket News section of the AMCC website.
And congratulations to Nathanael on his brilliant lap times at the weekend, in both F4 and F5.
Tim




Great Day at Mt Wellington. Out on the 50 and had lots of fun. The bike ran really well, but I got slower as the day went on. My best time was 35.8, the winning bike (number 58) and rider were just a shade over 31's. That is faster than I have ever been around there, even on my 125.

Some of the other F5 bikes.

[mr bucketracer]

went out to brian thomas work shop today , i saw a 50cc Kreidler he had build ....yummmy! here is a link to some stuff he has built

http://www.themotart-journal.com/201...ollection.html