Aerochargers etc: real back pressure numbers

[Greg Hermann]

At 11:54 PM 10/16/01, Dave Evans wrote:
>Hi
>
>Wouldn't lower back pressure increase oil blow by, past the seal?
>Theirs some picture around of a Garret T25, verses a T3, and it would
>appear from the casting point of view that its just the T3 has been
>flowed.

I suspect that the problem is something other than backpressure.

Consider: If you are getting any significant backpressure on the turbine at
idle or on over-run--when there is little gas flow at all--I hate to think
what your backpressure would be under load !!

Greg
>
>I know on the T25 fitted to my car unless you've got cats fitted
>(increasing the back pressure) oil virtually pours past the seal at idle
>and on over run, I'm told this is a common problem with the T25, any
>Nissan ZX?00/T25 owners care to comment.
>
>Cheers
>
>
>In message <Pine.SOL.4.33.0110161813480.938-100000 at tempest.gpcc.itd.umic
>h.edu>, Frank F Parker <fparker at umich.edu> writes
>>> Insightful info.  Thanks.  I am curious as to whether you had an exhaust
>>> system downstream of the turbine in your TY during those tests (ie: piping,
>>> converter, muffler), and whether you data logged the EBP at the turbine
>>> discharge?  Anyone else ever measure this type of thing?  I know this is
>>> going to sound rather vague, but, what's an acceptable value for post
>>> turbine EBP in a street car before seriously impacting a turbo's capability?
>>> Walt.
>>>
>>
>>Yes, I had a complete exhaust, 3" downpipe back to a Flowmaster and 3"
>>over the rear axle, but test pipe in place of cat.
>>
>>Sorry, did not measure EBP at the turbine exhaust but from tests others
>>have reported, it seems turbos like the lower the better. In fact, in the
>>early days of turbos, exhaust backpressure was often used to limit boost.
>>( my old 66 Corsa turbo, for example). Also used an external HKS wastegate
>>with it's output fed back to DP about 3x dia's down the pipe.
>>
>>regards,
>>
>>frank parker
>>
>>
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>
>--
>Dave Evans
>Lotus Omega 3.6l,S6,412Bhp,186Mph on the clock.
>
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