ESE's works engine tuner

[F5 Dave]

0.04 would be better for 40mm bore but it's certainly not doing somersaults in there.
There's not much back to that piston so replacement schedule may have to decrease

[lodgernz]

Maybe, squash gap is too small and sometimes piston touching the head.

No sign of contact, apart from where a few bits of the skirt have made their way up the transfers and out the exhaust. Squish gap was 0.75mm.

I've seen it before on cast iron sleeve cylinders probably because of pistonclerence. I have thought it was because of curb jumping

The cylinder is cast iron, but piston clearance seems OK. Kerb jumping is unavoidable in bucket racing. For me anyway.

0.04 would be better for 40mm bore but it's certainly not doing somersaults in there.
There's not much back to that piston so replacement schedule may have to decrease

Back face is in really good order, but yeah, agreed.

[Grumph]

Have you got access to dye penetrant crack test gear ? I've reached the stage of life/cynicism where I automatically test pistons esp if they're NOS.

Surprising what you find too...

[jonny quest]

Is that a $6 China piston from Ebay? There's your answer.

[lodgernz]

Have you got access to dye penetrant crack test gear ? I've reached the stage of life/cynicism where I automatically test pistons esp if they're NOS.
Surprising what you find too...

I'll check around.

Is that a $6 China piston from Ebay? There's your answer.

Ha ha, no, USD70 Kitaco piston made in Japan. Chinese one wouldn't have lasted 10 tough hours.

[Jannem]

Is there a reason why the atac valve should be in the header. Would it work in the side of the expansion chamber the same?
Or at the end of it?

[TZ350]

Is there a reason why the atac valve should be in the header.

Good question, to find out, try this search:-

atac valve site:www.kiwibiker.co.nz/forums/showthread.php/86554-ESE-s-works-engine-tuner

[Jannem]

Thanks, tried it already.

I guess the question could also be formulated differently:
Does the main benefit from atac come from the volume change or or out of phase standing wave at a specific point in the pipe near ex flange)?
All previous discussion is about the location in the header.

The reason I’m asking is an idea about combining adjustable volume and stinger size at the end of the pipe, which would be simple to implement.

It would be adjustable for stinger separately for valve open and valve closed and would also increase pipe length for open. Only one simple moving part with no sealing issues.

[Frits Overmars]

... an idea about combining adjustable volume and stinger size at the end of the pipe, which would be simple to implement.

Something along these lines Jannem?

[Peter1962]

Something along these lines Jannem?

Frits, to your knowledge, has anyone allready tried & tested this design ?

[wobbly]

My understanding of the ATAC sitting near the cylinder exit is that the stuffing pressure wave returning up the header at the wrong time ( due to the pipe length being mismatched to rpm)
is reduced in amplitude when it encounters the relatively large side volume by the opened valve.
Several manufacturers use this idea in concert with the power valve,in that when it is down,the Exhaust duct is connected to a volume within the sides of the cylinder via a hole in the
PV drum or blade.
When the PV rises,this hole is blocked of.
Killing the return wave pumps up the lower end power by reducing the pipes efficiency, exactly the same effect as opening up the stinger area at low rpm does.

[TZ350]

Frits, to your knowledge, has anyone allready tried & tested this design ?

Maybe not exactly like Frit's design but gives some idea of the possibilities. My experiment had much the same effect of increasing the chamber bleed area and lowering the residual working pressure in the chamber.

Need to click back to the original post to view all the related work.

The mid chamber bleed re visited as it might be useful for some low end boost...... Ok the mid pipe bleed didn't work for me as an over rev detonation suppressant but it did show a useful low end boost. The interesting thing was that there was very little noise from it.

Attachment 286902

Red line is the bleed in the open position, Blue is closed.

Attachment 286903Attachment 286904

And there was those who scorned me for trying this .......

I will re visit this again sometime, maybe with a bleed system like Frits suggested.

[Frits Overmars]

Frits, to your knowledge, has anyone allready tried & tested this design ?

I designed this system in 2007 for Jan Thiel, who retired at the end of that same year, so the professional tests I had hoped for never took place.
After Jan and I decided to reveal our ideas, one or two tuners informed that they were going to try the moving tailpipe system, but I have no data.

My understanding of the ATAC sitting near the cylinder exit is that the stuffing pressure wave returning up the header at the wrong time ( due to the pipe length being mismatched to rpm) is reduced in amplitude when it encounters the relatively large side volume by the opened valve. Several manufacturers use this idea in concert with the power valve,in that when it is down,the Exhaust duct is connected to a volume within the sides of the cylinder via a hole in the PV drum or blade. When the PV rises,this hole is blocked of.
Killing the return wave pumps up the lower end power by reducing the pipes efficiency, exactly the same effect as opening up the stinger area at low rpm does.

+1

[TZ350]

All previous discussion is about the location in the header.

The reason I’m asking is an idea about combining adjustable volume and stinger size at the end of the pipe, which would be simple to implement.

Interesting idea. Yes, when you think about it, it has all been at the header end and the benefits trumpeted by the Marketing dept. Just because it was done that way and popularized in the 70's and 80's does not mean its the only way, or even the best way.

Maybe out of phase wave disruption could be better achieved by disrupting it at the reverse cone.

....... interesting ... ... not conventional but makes sense, thanks jannem for the ideas, you have got me thinking.

Because the reverse cone works by capturing pressure from the travailing wave and reflecting it back. Maybe disrupting the pipe action during its out of phase period would work best if the pressure in the reverse cone was not allowed to build up at all by bleeding it off into a side chamber or over sized stinger. The good thing is that unlike a conventional system with the ATAC in the header the front header/diffuser section of the pipe would still assist with scavenging if the disruption was in the reverse cone.

And maybe something like a Yamaha Exup valve could be used to open a side chamber or to activate something like Frit's idea.

[oldjohnno]

A couple of years ago I was experimenting with different silencers in an attempt to quieten a 360 single street bike. One of the mufflers I made was a baffled design rather than an absorption type with packing; it was too loud and reduced peak power a bit though it very noticeably filled in the hole in the torque curve just under the powerband. I made the openings in the muffler a little smaller in an attempt to make it quieter and this worked to some extent but I also lost the torque it previously had under the pipe. At the time I thought the combination of a servo-operated belly bleed with a conventional rear stinger and silencer might work well but never tried it.