Exhaust System Back-draw - Saab 9000 Bulletin Board - Saabnet.com


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Exhaust System Back-draw
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Posted by SwedishDynamicsInc [Email] (#2304) [Profile/Gallery] (more from SwedishDynamicsInc) on Tue, 5 Nov 2019 14:34:42 Share Post by Email
In Reply to: Re: Exhaust System Back-draw, Dim33, Sat, 2 Nov 2019 17:25:08
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Dim33,

Thank you for your reply!

On paper, 2.5" single pipe exhaust plumbing diameter has the potential for targeting 450 horsepower of flow, without restrictions, but this sizing is ideal to retain optimal velocities without the symptoms of back-draw when employed on the 2.0 or 2.3 SAAB engine applications.

The 3" size plumbing will almost always allowing for your draw-back symptoms at vehicle decelerations due to this being excessive for most 4 cylinder engine applications. These symptoms will typically worsen as the engine horsepower increases which provides greater exhaust velocities. The fact that you are at base boost pressures should be greatly reducing your exhaust draw-back symptoms. Restoring full turbocharger boost pressures should create more symptoms of the exhaust draw-back.

We have several customers with 3" exhaust systems who installed a reducing 2.5" diameter mid muffler plus long resonated reducing rear tip in an attempt to eliminate back-draw with some success, and this does dramatically change plumbing diameters which has never been recommended.

Another route to reducing exhaust back-draw would see employment of turbocharger turbine wheel which allow for a greater exhaust output. This requires a reduction in the turbine wheel "Cupping" which allows for greater exhaust output at the wheel's discharge. The OEM turbine wheel could also be sent for clipping of the wheel to allow for better exhaust throughput, but this will always increase turbocharger lag, especially in conjunction with the 19T compressor wheel trim.

Thanks again for your post, and we will be available until 6PM EST if there should be additional questions!

Sincerely,

Gary K. at SWEDISH DYNAMICS, INC.

->Posting last edited on Tue, 5 Nov 2019 20:33:51.
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