ETZ 250 / TS250 Exhaust compatability

[Andy_C]

Does anyone know whether the 2 are interchangeable, and whether they are physically identical, in terms of diameter / length / length of the front tapered section.

I believe that the ETZ version might "kick up" slightly at the end whereas the TS is straight.

Reason for asking it that I know of a a virtually new ETZ exhaust that the owner wants to get rid of.

The one on my TS is a bit tatty and if the EZT exhaust would fit wihout upsetting engine performance I might well buy it.

Thanks.

[Puffs]

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[Kruh]

I would love to know that as well. Also a TS owner and am curious if the ETZ exhaust would improve performance. The 251 exhaust specifically is interesting to me, because of its overall shirter lenght.
I don't think that ETZ kick up look would look too out of place on the TS.

This is the best I could find:
http://www.simantik.de/mz-tuning-auspuff.shtml

By the looks of it, there is a slight performance improvement.

[Andy_C]

Kruh.

Having dug around the web on the face of it the only differences I can see physically between a TS and ETZ silencer are that:

1. The ETZ silencer is about 80mm shorter
2. The ETZ silencer is "kicked up" slightly

The bigger question is what are the internal differences? The porting on ETZ engines is different to the TS so I would expect them to be different.

The slinecer at http://www.simantik.de/mz-tuning-auspuff.shtml I have had experience of one of these on an ETZ 250, I found the silencer takes away much of the bottom end power of the ETZ and you have to rev the engine a lot harder. I ended up cutting the silencer into 2 pieces and welding a 250mm length of 100mm diameter tube into the silencer, effectively giving it a "belly" I found out that it worked really well on my old ETZ, no loss of bottom end power - the engine felt a lot more liveley with the silencer after that mod, but out of the box they dont work well at all.

[Kruh]

I see, with the shorter silencer on the 251, it has less backpressure, than the 250 and ts which have more pipes inside. Is this a issue with the original or was it a replica?

The etz has increased port timing compares to the ts, but the max power rpm hasn't increased much (only about 300 rpm). So I'd imagine the exhaust to have a very similiar tuned lenght to the ts.
Although, looking at the photos, the centre belly section (between the welds) seems a fair bit shorter on the etz exhaust. Which would mean the tuned lenght is shorter (perhaps the etz header pipe is longer). That would explain the increase of power on the top end, and loss in the bottom end, mentioned in that post.

Also, are there performance differences between new replica exhausts and the original?

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[Kruh]

I would disagree. This is a expansion chamber and it does have a tuned lenght.
It has a header pipe, diffuser and belly section just like any tuned pipe. The only difference is that there is no reverse cone. But that flat baffel at the end does reflect the pressure waves and has to be positioned at a specific lenght for optimal performance. The shape of the baffle just changes the way the power is distributed.
Generally, a shallow taper of the cone offers more broad power, while sharper cones offer more peak power, but less range. A flat baffel will allow the bike to rev only up to the max power rpm it was designed to (like a rev limiter). Whereas with a baffel cone it can rev past its peak rpm.

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[Kruh]

I might be wrong or using the wrong terminology.
My knowledge and experience is limited.
Since the mz exhaust differs from a proper expansion chamber only by the baffle design. I would still be inclined to call it a expansion chamber.
But, I do agree with you, that its not a very good one.
A proper pipe with a tapered header and multi stage diffuser would go a long way. But I belive just by adding a baffel cone to the existing mz pipe would help greatly with the performance.

Which is actually something I'm already working on and will post more about it once I do more testing. But basically, its the same overall dimensions of the original, from the header back, just with an addition of a reverse cone. Interestingly enough, the dimensions are fairly close to the recommendations of Jennings and Graham Bell.

[Andy_C]

Kruh.

You might be intrested in this, when I had my ETZ the silencer was in a pretty sorry state and I bought one of those expansion chambers - "Tuning Auspuff" very cheaply from an autojumble.

When I fitted it to my ETZ, it killed what little low down torque it had, but the engine really came to life at the upper end of the rev range, and the engine would rev much more freeley.

One of the problems with these chanbers is that it is way too short - it has hardley any "belly" what I did was to cut the expansion chamber apart at the end of the long taper and weld a section of 100mm diameter / 250mm long tube between the 2 pieces - not exactly scientific.

After doing this the bike ran really well - felt more or less like the standard exhaust but it was much more willing to rev, and I am sure it pulled a little harder in the upper rev range, it also stopped the engine surging on the over run which was a nice by product.

I covered many miles with that modified chamber, and I thought it ran really well, so much so I never bothered to fit a standard silencer to it again.

[Kruh]

Thanks Andy. Nice to know its worth doing.

This has been my experience as well on the first test ride. Very noticable improvement in the upper range, but quite a loss in the bottom end. Powerband from about 4500 to over 6500 rpm. Pipe definetly too short.
Will be lenghtening the belly as well.

[Andy_C]

Try the same belly size as I used Kruh - as I say worked very well with my ETZ.

I actually have another one of those expansion chambers out in the garage, it came with a box of MZ bits that I bought a long time ago, wondering if I made the same modification to this one how well it would work on my TS.

Anyway keep us posted.

[Puffs]

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