EXUP - How does it work?
Marco Alves
functioning of the exup valve in those engines that have it. Can anyone
enlighten me?
Thanks.
Marco Alves
Steve H
"Marco Alves" <marco...@lis2.siemens.pt> wrote in message
news:9c121m$oh8$1...@venus.telepac.pt...
there to vary the backpressure of the exhaust sytem. Haynes manual for
FZR600, 750 & 1000's quotes 'This valve (the EXUP), mounted in the exhaust
sytem, regulates exhaust backpressure to increase performance and reduce
exhaust emissions.'
The exhaust on most bikes is a compromise, whats best for one engine speed
won't be so good for another. Backpressure is created by sound waves in the
exhaust system and is required to maximise extraction of exhaust gases. The
EXUP valve is a rotating plate in the exhaust collector, operated by a
servo motor, controlled by the CDI unit. The valve restricts flow at low rpm
and opens fully at higher rpm.
Honda & Suzuki are now using similar valves in the Fireblade and GSXR1000. I
have seen some articles that suggest that these valves may also help
motorcycles to pass noise emission regulation, that is the valve restricts
exhaust flow (and therefore noise) at the rpm that the noise test is carried
out.
I personally own an FZR1000 with EXUP valve and the power spread is very
broad, pulling from 2500rpm upwards.
Steve H
--
FZR 1000, BMW R80/7
Kaybearjr
>The exhaust on most bikes is a compromise, whats best for one engine speed
>won't be so good for another.
When Suzuki first allowed the motorcycling press to road test their new
4-stroke GS-750 in 1977, the writers claimed that the engine had a "delightful
two-stage power delivery," that it had good low end torque up to 4K or 5K rpm
and that it had a second
torque peak at 7K to 8K where there was lots of power...
By the time the GSXR-750 was being tested, the writers were admitting that
there was a terrible flat spot between 5K and 7K rpm, where the reverse
pressure pulses from the four-into-one exhaust system were
coming back through the intake valve during the overlap
period and preventing the cylinders from sucking fresh mixture through the
carbs...the flat spot is an untunable lean condition...
I bought a Dyno-Jet kit, and called up the manufacturer of the kit for info.
The tech-rep said that I would have the flat spot described above, but what
most riders did was accelerate hard enough to rush through the 5K to 7K flat
spot...
Well, that made the GSXR-750 a rather nerve-racking bike to ride in situations
where I wanted to run in third gear. It would flatten out, and I would have to
shift back to second, and "rush through" to 7K, and repeat the whole silly
cycle of riding a bike with a flat spot...
Yamaha, with their expertise in acoustics and exhaust system tuning, invented
the 4-stroke exhaust throttling valve by 1989...
The EXUP valve breaks up those annoying reverse pulses which caused the flat
spot...
It has only taken Suzuki and Honda a dozen years to
adopt the wisdom of exhaust throttling...
And I have been spoiled by my EXUP since 1995...
mrdancer
news:20010423172718...@ng-cf1.aol.com...
<snip>
> Yamaha, with their expertise in acoustics and exhaust system tuning,
invented
> the 4-stroke exhaust throttling valve by 1989...
>
> The EXUP valve breaks up those annoying reverse pulses which caused the
flat
> spot...
>
> It has only taken Suzuki and Honda a dozen years to
> adopt the wisdom of exhaust throttling...
That's because Yamaha had a patent on it, and the patent expired only
recently. Honda and Suzuki had the technology, they just couldn't bring it
to market until Yammy's patent expired.
> And I have been spoiled by my EXUP since 1995...
Yamaha's FZ1 reportedly has a flat spot between 3000 and 4000 rpm, so EXUP
isn't quite perfect yet.
Steve Bailey
"Kaybearjr" <kayb...@aol.comedy> wrote in message
news:20010423172718...@ng-cf1.aol.com...
snip
>
invented
> the 4-stroke exhaust throttling valve by 1989...
>
Yamaha created it much earlier but for 2-strokes. The idea becomes much
easier to understand if you know about 2-stroke port timing. The idea is
to tune the positive power pulses to restrict the intake charge going
straight through the exhaust port but then to allow negative power pulses
to suck the exhaust gas out of the cylinder. It in effect does the same
job as lower ports which allow for more power lower in the rev range. By
opening the valve after a certain rpm the motor is allowed to benefit from
the higher ports which aid in high rpm power and cylinder filling.
Yamaha realised that in a 4-stroke the same principles were in effect.
A high flow pipe gave high rpm HP but robbed the backpressure needed for
midrange performance. A moveable restrictor in the exhaust system was
their answer. Same as a "power valve" that is cast into the cylinder only
this time in the collector. The EXhaust Ulitimate Powervalve.
Now they could tune the motor for high RPM by using free flowing
exhausts, more valve overlap, higher cam lift and still keep the
backpressure needed for midrange by restricting the exhaust.
Steve
--
R.A.C.E. am#2 Honda RS 125
CMA Novice Trials #143 Fantic 241
Marco Alves
newsgroups should function.
Thanks steve for the info. I don't think I'll start messing around with the
servo just yet. The bike's practically new and I'm assuming the EXUP system
works fine. It was just a curiosity of mine as to the working of the valve
itself.
For all those interested, at: http://thunderace.hadeler.net/ you can see in
the parts section where the valve is located.
----------------------------------------------------------------------------
--
Marco,
I think you will find that the other Japanese manufacturers are only now
using valves in the exhaust because Yamaha had a patent on the system. I
think the patent has now elapsed, allowing other to use it.
To check if your Exup valve is working you need to lacate the servo
which controls it. On the FZR it is under the tank, on the right had side
towards the rear. There are 2 cables attatched to a drum on the servo which
go to the Exup valve. To check if it is operating, turn off the ignition and
rotate the drum on the servo by hand. It should turn quite freely. Leave the
drum at the extreme of its travel then turn on the ignition (make sure the
kill switch is on). The servo should return to its original position.
If it won't turn then its probable that the Exup valve is stuck (not
uncommon). If so it means a stripdown and lubricating with copper grease.
Soak all the bolts on the valve in freeing oil, preferably the night before.
If it turns by hand but won't return when you turn on the ignition, then
either the servo or the CDI unit may be defective. If you think this may be
the case then it would be worth getting your Yamaha dealer to look at it
first as both components are somewhat expensive, new.
One last point, if you are posting on a newsgroup it is customary to
reply, via the newsgroup, not by e-mail direct, unless specifically
requested.
Hope the above helps
Steve H
FZR 1000, BMW R80/7
Steve H <stev...@hotmail.com> wrote in message
news:%7VE6.2164$f.44...@news1.cableinet.net...
Shaun
>
>The EXUP valve breaks up those annoying reverse pulses which caused the flat
>spot...
>
>It has only taken Suzuki and Honda a dozen years to
>adopt the wisdom of exhaust throttling...
>
>And I have been spoiled by my EXUP since 1995...
>
I have an FZR400 exup and midrange pull in top gear is amazing for
such a small highly tuned bike. However.........
in the real world, after several years EXUP valves stick, rattle.
wear out, and force you into paying Yamaha prices when the headers
rust through. For long-tern ownership I'd prefer not to have one.
Kaybearjr
>in the real world, after several years EXUP valves stick, rattle.
>wear out, and force you into paying Yamaha prices when the headers
>rust through.
Yes, I priced out the exhaust system for
my FZR-1000. It looks like the header system is about $700...and the muffler
can is another $400...