[Diy_efi] RE: Banjo Dis. Pic

[Mike]

At 10:14 AM 9/1/2003 -0800, you wrote:
>Any pic of the current set-up? Your T3 flanged dump is an elbow?

Standard one, nothing special - seems to go straight out
in line with turbine... I have a 2meg byte pic somewhere have
to trim it a bit,

>I thought wastegates were used to avoid high engine back-
>pressure. You were you talking about throttling the turbine
>not the compressor, right?

No. From a control systems perspective its generally better
to control the input variable - in this case the air into the
compressor. I understand why its being done in terms of the
exhaust, cheap, traditional etc. The current wastegate system
is a 'bad' compromise for a mechanical throttle coupled with
commercial issues.

In principle it is more efficient to control the boost
pressure with the input throttle, not feasible unless you
have drive by wire - which simplies the turbine/wastegate
casting and should end up smoothing out the exhaust flow
not having the discontinuity of a wastegate to mess it up.
The 'delay' through the engine at speeds capable of boost
reaching some maxima is trivially short.

Another method is to have an extra ECU-controlled butterfly
in front of the compressor inlet, but this adds turbulence
and restriction (a little). In control systems aspects its
far better to control the pre-amplified variable instead of
dumping 'power' (post amplified variable) vis a vis exhaust
pressure after the event so to speak.

>A smooth, gently narrowing pipe can be sufficient muffling to
>avoid the resonator altogether, it'll bark as your wastegate
>opens though :)

mmmm, My exhaust is throaty now as its 3" all the way through
and all the existing resonator is - is just a opened pipe
with restriction at both ends - though not much. The muffler is
a 'straight through' - the car goes well and is quiet at highway
cruise speeds a little noisey when pushing it hard.

PS: Only just saw this email  after some time as it didnt come
through list, I llok at my list stuff first and am interested
in any other observations so I'm happy to keep it on list, tah

rgds

mike




>Cheers,
>Rod
>
>-----Original Message-----
From: Mike [mailto:erazmus at iinet.net.au]
>Sent: Thursday, January 09, 2003 9:38 AM
>To: R.E.Hiorns at IEE.org
>Subject: RE: Banjo Dis. Pic
>
>
>Unfortunately I have the existing turbo-flange dump pipe,
>which looks like 2.5". So I have a 'downpipe' which comes
>from the turbo dump. Its 3" as is the rest of the system,
>cat, and resonator and tip. Seems to be a heck of a lot
>better then before and the resonator (basic type) seems
>to absorb any highway drone (80 - 120Kmh). I havent
>done a turbo outlet pressure yet - too preoccupied with
>work. I might get a proper T3 flanged dump next time though
>I have been thinking of getting a turbo with no waste gate
>and throttling the inlet instead as boost control, makes
>more sense from a control systems perspective and its unclear
>why its not done - other than cost issues, for performance
>mods vis a vis exhaust flow improvements, thanks for the
>feedback - I guess I could do a TOP as I have a few gauges
>around the place, maybe after work calms a bit next month,
>
>rgds
>
>mike
>
>
>
>At 09:26 AM 1/9/03 -0800, you wrote:
>>T3 -> 3" ... if you have no abrupt corner in the downpipe then
>>you're not doing badly. The easy way to match them is to use an
>>opening taper in the exducer, and if it's steep enough it'll
>>cause turbulence to drop out of the helix and give you pretty
>>much minimum TOP. The angle required is about 30 degrees but
>>don't quote me on that! Keep the wider pipe for at least a foot,
>>maybe 2, after that you can narrow slowly to 2.5" if you like.
>>Have you measured your TOP? You might have no issues to tackle :)
>>Cheers,
>>Rod
>>
>>-----Original Message-----
>>From: Mike [mailto:erazmus at iinet.net.au]
>>Sent: Thursday, January 09, 2003 8:35 AM
>>To: R.E.Hiorns at IEE.org
>>Subject: RE: Banjo Dis. Pic
>>
>>
>>At 08:29 AM 1/9/03 -0800, you wrote:
>>>Hi Mike
>>>I'll get you a pic later. Let me know if you find one in
>>>the meantime. IIRC they're as good as a straight pipe.
>>
>>OK, tah - I'd like to see some physical issues, size, angles etc
>>
>>>Imagine a compressor assembly put up to the turbine exducer,
>>>except round not spiral, and with no wheel. The gas enters
>>>axially and leaves radially, so effecting a 90 degree turn in a
>>>very small space. They're used to avoid sharp corners.
>>
>>mmmm - I have a T3 into a 3" exhaust, hence a discontinuity, I'm
>>wondering if a horn type outlet into the larger pipe from the
>>small turbine exit would be of benefit ?
>>
>>rgds
>>
>>mike
>>
>>
>>
>>
>>>Cheers,
>>>Rod
>>>
>>>-----Original Message-----
>>>From: diy_efi-bounces at diy-efi.org [mailto:diy_efi-bounces at diy-efi.org]On
>>>Behalf Of Mike
>>>Sent: Thursday, January 09, 2003 7:40 AM
>>>To: List for general do-it-yourself EFI talk
>>>Subject: Re: Banjo Dis. Pic ? Was Re: [Diy_efi] Turbine inlet &
>>>outletpressures, housing A/Rs
>>>
>>>
>>>At 08:32 AM 1/9/03 -0700, you wrote:
>>>>>Excuse my ignorance, anyone have a picture of a banjo discharge ?
>>>>
>>>>There's a picture of one in the McInnes book. No numbers available.
>>>
>>><cough>
>>>
>>>As you could probably have predicted, I asked this from an
>>>internet perspective...
>>>
>>>Sorry for not being pedantic,  is there a picture on the web somewhere,
>>>would someone have a link or have scanned a copy of the relevant page
>>>(for academic study only;) which shows a turbo banjo discharge ?
>>>
>>>rgds
>>>
>>>Mike
>>>
>>>
>>>
>>>
>>>>Greg
>>>>>
>>>>>And anyone have a metric on how much better they are supposed to
>>>>>be - or are we talking the little banjo fitting on the water
>>>>>and oil on the turbo ~`:o
>>>>>
>>>>>I've done a quick search on google but I seem to get all sorts
>>>>>of other discharges, mostly medical ones, some with turbos ;-)
>>>>>
>>>>>
>>>>>Rgds
>>>>>
>>>>>Mike
>>>>
>>>>
>>>>
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>>>>Diy_efi mailing list
>>>>Diy_efi at diy-efi.org
>>>>http://www.diy-efi.org/mailman/listinfo/diy_efi
>>>>
>>>>
>>>
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>>>
>>>
>>
>>
>
>

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