[Diy_efi] Turbine inlet & outlet pressures, housing A/Rs

[Greg Hermann]

At 3:49 PM 1/6/03, Grant Beaty wrote:
>Oh Greg,
>
>Just saw some old posts of yours in the archives,
>http://www.diy-efi.org/diy_efi/archive/1999-January/msg00237.html
>
>> >I think the REAL unexplored gain is in (more efficient) pressure recovery
>> >from the Mach .75 velocity in the gas spiral at the turbine outlet,
>though.
>> >The circumferential component of the flow in that gas is distinctly
>greater
>> >than the axial component.
>
>Hugh McInnes states that increasing pipe diameter right after the turbine
>outlet will convert axial flow into turbulent flow. But in your post you
>don't seem to consider that as an option, instead opting for a banjo
>discharge. Is there any reason for that? Have you tried larger pipes without
>success? Any idea how much larger the pipe needs to be than the turbine
>inducer?

A banjo would do an even better job of converting the spiral flow to
straight turbulent (less static pressure loss) than a step in the down
pipe, that's all. I think a step up from the exducer to the down pipe of
3/4" to 1" is generally sufficient to shock the flow out of the spiral.

The more of that static pressure you can recover (less shock loss), the
lower the effective outlet pressure is going to be at the turbine outlet,
and the less inlet pressure you will need.

Greg
>
>Forgive my lack of understanding of your post, but are you suggesting that
>exhaust gas velocity post-turbine could be more than doubled by
>straightening the flow? Wouldn't that imply pressures < ambient? Or would
>total velocity out the turbine decrease, and more would go out the
>wastegate? Either is good, I guess.
>
>Thanks for any help,
>Grant Beaty
>
>----- Original Message -----
From: "Greg Hermann" <bearbvd at mindspring.com>
>To: <diy_efi at diy-efi.org>
>Sent: Monday, January 06, 2003 10:56 PM
>Subject: Re: [Diy_efi] Turbine inlet & outlet pressures, housing A/Rs
>
>
>> At 7:21 AM 1/6/03, Grant Beaty wrote:
>> >Does anyone know how turbine outlet pressure effect the inlet pressures
>(TIP
>> >& TOP)? Does it work off of a pressure ratio like the compressor, or is
>it
>> >linear, and increasing TOP by 1 psi results in a 1 psi increase in TIP?
>>
>> Absolute pressure ratio, all the way.
>> >
>> >How about exhaust housing a/rs. Will a larger a/r always produce a lower
>> >TIP,
>>
>> Sure should.
>>
>> Higher EGT at the turbine inlet should require a bit lower pressure ratio
>> across the turbine to get the same shaft power (boost level at a given
>> engine rpm) out of the compressor.
>>
>> Greg
>> >
>> >Thanks for any help,
>> >Grant Beaty
>>
>>
>>
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