ESE's works engine tuner

[Haufen]

Well made pipes that go around a corner dont loose any power to a dead straight one - but dead straight pipes do actually cause deto, and need a deto button of some sort in the header to suppress this artefact. I posted a pic of one of these on here ages ago.

Can an EGT probe serve as a deto button on a straight pipe?

[wobbly]

I did proper back to back testing of the bent Vs dead straight pipes when building the BSL500.
The top pipes could be dead straight with just a small angle where the slip joint fitted onto the header,and these 2 pipes would deto as soon as you got close to spot on tuning.
Fit a deto button and the effect simply disappeared - we always had egt probes fitted and they made no difference.
On the bottom pipe of the tripple, this had a serious S bend to get the belly forward enough for it to fit nicely into the banana arm.
I found that as long as we had about 100mm of dead straight header fitting onto the slip joint I could get identical Hp within 1/2 in 55 as long as compensation was
made for weld shrink on every joint, as well as every joint being hammered smooth.
And the S bent pipe did not need a deto button at all.
I discussed the straight header effect with the Yamaha R&D chief at the time called "Suzan" and he opined that if you had a bend too close to the slip joint
especially if it was bent in any way than on the vertical plane, this gave rise to an asymmetric plugging pulse flow, and this adversely affected the loop scavenge regime.
Sounds pretty plausible to me.

[TZ350]

Links to pictures of pipes with det buttons.

Here's some pics of rgv500 cylinders and pipes...hhmmm...

Hi all, Attached is some pictures of a late model TZ yamaha titanium GP 125/250 pipe. Can anyone explain what the part inside the pipe is.

Why is it there?
What is it called?
How does it work?

Ten carrot actors.

follow the posts for the RGV500 version and pictures

When unleaded became mandatory in 98 most teams had a hell of a time keeping deto under control, having to run very rich and retarded.
The cylinders with the straighter pipes always gave alot more grief, untill a lowly dyno operator at Yamaha discovered that
when he stuck a large pressure probe into the header, the deto went away.
They managed to keep this secret for a couple of years but when teams like WCM got hold of the bikes, and left pipes lying about as you see in the pics,word soon got around.
The "things " intruding into the header take varying forms,but all do the same thing - the usually bottom "bent "pipes dont have the same issue, so dont need the so called deto buttons.
I have a couple somewhere from a Red Bull bike - I will pic them and post here .

Here is a shot of a cylinder I have been working on - its just come back from plating - the duct entry shape looks a bit familiar doesnt it.
The plating must have more Nickel in it, that would be why some of the previous shots on here look as though the cylinders have a liner, its the colour of the plating process.

[adegnes]

I did proper back to back testing of the bent Vs dead straight pipes when building the BSL500.
The top pipes could be dead straight with just a small angle where the slip joint fitted onto the header,and these 2 pipes would deto as soon as you got close to spot on tuning.
Fit a deto button and the effect simply disappeared - we always had egt probes fitted and they made no difference.
On the bottom pipe of the tripple, this had a serious S bend to get the belly forward enough for it to fit nicely into the banana arm.
I found that as long as we had about 100mm of dead straight header fitting onto the slip joint I could get identical Hp within 1/2 in 55 as long as compensation was
made for weld shrink on every joint, as well as every joint being hammered smooth.
And the S bent pipe did not need a deto button at all.
I discussed the straight header effect with the Yamaha R&D chief at the time called "Suzan" and he opined that if you had a bend too close to the slip joint
especially if it was bent in any way than on the vertical plane, this gave rise to an asymmetric plugging pulse flow, and this adversely affected the loop scavenge regime.
Sounds pretty plausible to me.

Do you have any rule of thumb numbers on what is bendy enough to not need the button? I was planning a straight exhaust for my build, but this is giving me second thoughts.

[seattle smitty]

Everybody else here seems to know this term, not me. I went to Advanced Search, tried both "deto button" and "detonation button" with wobbly as author, hoping to find out more but got zero hits.

[adegnes]

Everybody else here seems to know this term, not me. I went to Advanced Search, tried both "deto button" and "detonation button" with wobbly as author, hoping to find out more but got zero hits.

You are not alone.

[husaberg]

Everybody else here seems to know this term, not me. I went to Advanced Search, tried both "deto button" and "detonation button" with wobbly as author, hoping to find out more but got zero hits.

You are not alone.

Don't use advanced search, it searches all of KB
use the search thread which is below it.then search
Using your same key words pulled up everything

[wobbly]

I have a couple of deto buttons here but cant be bothered looking hard.
All they are in the form used by Yamaha and Roberts etc is a sort of mushroom.
Or a penny on a stick.
The penny being around 20mm dia by 3mm thick sitting on a stalk big enough for an M6 down the middle and a couple of flats to hang onto.
The length being so the penny sits around 1/2 way into the pipe dia.
This thing situated about 50mm from the slip joint fixes the deto issue with a straight pipe.
Any bend that isolates the main body of the diffuser from the port seems to work.
The only plausible explanation I have is they shield the duct from infra red heat radiating from the pipe body interior - that overheats the plugging vol
sitting in the duct.
Goes along with not using heat wrapping on a header as it instantly causes deto.
And as we well know Mr Thiel is a big exponent of keeping the duct charge volume small and cool - works for me.

[adegnes]

Any bend that isolates the main body of the diffuser from the port seems to work.

Thanks! Could you elaborate on the isolate part? If I where the diffuser I should not be able to see the port?

[TZ350]

Wob explained to me that with the "Wall Temp a Function of RPM" box ticked the 50 deg entered in the "Exhaust Wall Temp at Max Power" has no effect(the 50 was more applicable to an older version of EngMod). He also suggested to me to use 325 at the start of useful power and 425 for max power and 450 for extra heat in the pipe in over rev if you have an elec power jet and or retarding the ignition.



Thanks Wob for the Heads-Up on the Temperatures to use with the EngMod2T simulation file.



Making progress with the RG50 pipe design.

Cheated a bit by making the inlet a large piston port in the simulation as I don't really know how to represent a 50/50 piston/case reed setup. But I forgive myself as I am only learning about pipes and how to use this simulation software for designing our own expansion chamber.

Page 1040 is about the basics as explained by Wob of how to influence where the point of maximum depression occurs.

There are other collections of pipe talk on pages 620 630 640 650 660 670 680 690 700 730 740 which have un edited collections of raw material. If your interested in expansion chambers they are worth a look.

[TZ350]

Everybody else here seems to know this term, not me. I went to Advanced Search, tried both "deto button" and "detonation button" with wobbly as author, hoping to find out more but got zero hits.

Some good search methods....

Some may find this useful. Rather than use the site search which usually fails, use Google so to search this site use an ordinary search phrase and after it add
site:www.kiwibiker.co.nz
for example
Frits priceless site:www.kiwibiker.co.nz
or
Frits pisa site:www.kiwibiker.co.nz
the same will work for other sites with the appropriate site address
Mick

Don't use advanced search, it searches all of KB
use the search thread which is below it.then search
Using your same key words pulled up everything

[Larry Wiechman]

The only plausible explanation I have is they shield the duct from infra red heat radiating from the pipe body interior - that overheats the plugging vol sitting in the duct.
Goes along with not using heat wrapping on a header as it instantly causes deto.
And as we well know Mr Thiel is a big exponent of keeping the duct charge volume small and cool - works for me.

Very interesting, Wob.
Wouldn't the button itself be glowing red hot?
Do these buttons function as a fluid diode for the return pulse?
I notice quite a difference in the downward angle of exhaust ducts. Does the escaping exhaust mass have a natural downward vector, or is this to direct the returning charge?

[wobbly]

Dunno about the mushroom theory, maybe I didnt take enough when I looked like Hendrix to get some insight.
Flux capacitor - fluid diode , take your pick before taking lysergide and peering into the running engine.

The down angle of the Ex duct has been thoroughly tested, again by Mr Thiel - 25* is the magic " mushroom " number.
This is to do with the initial flow adhering to the roof at low piston openings - the flow bench and the dyno dont lie to each other or us
in this case, again.

[seattle smitty]

Tried Husaberg's search, got hits, mostly from what's right here but a couple from some time back.

Weird, Wobbly. Weird! If a good curved exhaust system can make the same power as a equivalent straight system, why would the detonation effects be different? . . . well, I guess we know by sad experience that we don't have answers for everything in this lifetime, especially regarding 2-strokes as Frits has commented (but maybe he didn't consider the mushroom mode of inquiry).

[wobbly]

Being a Dutchy you can be sure several modes of serious inquiry were heavily investigated.
Nowdays I have the odd weed with my sons at Yes concerts, but being a Chemical Brother is relegated to serious testing of single malts.
My preference now is for a 16 yr old - no not schoolgirls, a Lagavulin lightly peated joy to the taste buds.