Exhaustive Degassing

Getting the gas out of the B204 was once a simple matter. With the engine transversely mounted there was plenty of room forward of the engine. So from the exit of the turbo the exhaust could sweep forward and downward and then under the engine. With those nice SAAB engineers designing and building series of pipes, silencers and catalytic converters all was calm, hot and under control.

Now in my world the first problem was how to get any sort of pipe out from the turbo flange in the first place. Let alone the fact that the longitudinally mounted engine requires a very tight 90 degree bend just to clear the engine bay. Add to this the shortened width and length of the chassis the requirements for flex couplings, lambda mounts, CAT, silencers and then another rapid 90 degree exit. Oh and don't forget that the whole exhaust has to be aerodynamically perfect, zero drag and zero turbulence. Simple..... yeah right!

PC powered up CAD/CAM to the ready and go..... well no not quite. None of the major custom (or universal) exhaust suppliers give much information away. Jetex are possible one of the best suppliers of info so naturally they get the biggest slice of the pennies. Even with Jetex parts arranged on the drawing board the solution was not yet available or for that matter affordable. On the other hand these nice guys on Ebay could not only dramatically reduce the costs but also give some very nice length and width information. So once the general plan had been accomplished with Jetex parts alternative better sized (and priced) parts could substituted.

The first job still remained getting a tight bend, flange and size change from the original turbo exit. This could only be achieved by building a custom component. Using a Jetex welded tight 90 degree bend in 2.5” mild steel plus a 2.5” flange the basics for the adapter were ready. The flange had to be milled out so that the SAAB 2" turbo exit can mate. The 2.5” tight 90 needed swaging out to the same as the turbo flange, so a mandrel had to be manufactured to achieve this. Then finally the new flange and bend had to be welded together to form the new component.

Turbo Flange to Flex section

From this point on the exhaust could be constructed from 2 ½ inch standard components. Performance gains between 2 ½ and 3 inch systems are minimal with sports CATS and silencers giving the greatest benefits. Actual flow through the system is the key, diameter is a relatively cheap and visually popular way of achieving the correct flow. Actually using high flow CATS and Silencers can provide exactly the same performance at slightly higher prices although less visually impressive. But when space is limited and for aerodynamics reasons, the entire exhaust system will be hidden from view by running through the bodywork, then the slightly smaller diameter system makes sense. A quick note on the fact that anything bigger that 3" actually will diminish performance at the lower end of the rev range and will probably cause peeks and troughs through out the rev range.

Flex Section to Lambda Section.

Lambda Section to CAT.

That keeps the ECU happy with life, now to keep the good fellows from the emissions dept. and noise abatement society happy.

CAT to Resonator Box.

The next bonus of the totally enclosed and hidden exhaust is the cost savings made by not requiring stainless steel. Eventually when all the sums are totted up the small bore, high flow, mild steel system runs out good value for money and should provide excellent performance. For ultimate power outputs the CAT will have to take a little nap in the garage.

Back box and Tail Pipe

CAT Back Section of the Exhaust.

Finally the whole assembly can be clamped and assemble with large amounts of assembly paste to stop any nasty leaks.

Click to see Further Degassing.

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