Saab b284 / A28NER highflow exhaustmanifolds

Initial manifold design in plastic through to the latest version in stainless steel 316L

First design of the manifold in plastic up to the latest version in stainless steel 316L.

The exhaust manifold of the V6 engine supplied in the Saab 9-3 from 2006 is a so-called “log” manifold. That means you have a straight tube on which the cylinder ports connect via smaller tubes. With the B284 and A28NER this has been designed such that after the exhaust gas leaves the exhaust port in the cylinder head it goes into the smaller tubes and then into the big “log” which sits perpendicular. That means there is very poor flow of exhaust gases. This causes the air to exit more poorly from the cylinder spaces, resulting in a lower filling degree.

This construction therefore results in the engine’s efficiency being lower than it could be. Because if the exhaust gases hit a wall then this creates back-pressure and heat. In addition it leads to uneven pulses arriving at the turbo and thus the turbo is not supplied cleanly in the ignition sequence of energy (hot exhaust gases). That causes heat and swirling which cannot be fully used for the turbo’s spooling.

In the process of improving our beloved V6 engine we therefore came up with the idea to develop a new and improved exhaust manifold with which we can increase the engine’s efficiency.

In this blog we will show the steps we have taken and will show the test results of the final exhaust manifold.

Mid-December 2025 we are expected to start taking orders for the manifolds.

The original manifold:

Original B284 A28NER exhaust manifold — left side surfaced, right side in as-removed condition

Step 1 is measuring the space in which the manifold must fit. We chose to scan the engine bay and a standalone engine. This allows us to place the design on the engine in the engine bay and take into account the dimensions.

3D scan of the Saab B284 engine bay

Then it’s time to start with the first sketch. V1 was with a V-band clamp with the idea of quickly making a universal coupling so that anyone who buys a set of manifolds can easily have a set of uppipes made.

We had it 3D-printed:

This technique works fantastically and helps us to develop faster. The bed of the 3D-printer was not large enough to print a manifold in one piece, so it was printed in two parts.

To print the manifolds faster and better we purchased a 3D-printer with a larger bed. This makes it possible to make the manifolds and other prototypes in-house quickly. The result is unprecedented:

Saab B284 highflow exhaust manifold V18

At Version 18 we felt very close to a first real stainless-steel prototype, so we began sketching uppipes that run from the manifolds to the turbo:

CAD design of B284 engine manifolds, uppipes and downpipe

In this drawing we were able to draw the manifolds, uppipes and downpipe to see how everything should theoretically fit.

The uppipes are still in development but will likely follow based on assembly of the manifolds with handcrafted uppipes.

We printed and fitted V18:

It already looked quite like it, adjustments from here up to V21 were; plate thickness from 4 mm to 8 mm, different radii in the bends, thicker wall of the entire manifold 3 mm and EGT cut-outs.

Here is V21:

After printing that version we arrived at an even slightly modified and more streamlined version with mounting lugs for the original heat shields and without the EGT cut-outs. Otherwise the shields wouldn’t fit. The shields are important so that was not an option.

Then the last plastic print:

Here a picture compared the latest version versus the second last. if you look closely you can spot the differences

After fitting the last version we decided it was time to print in stainless steel 316L. With anticipation we waited, the result is so cool!

The flange still needed machining as expected. On average 0.30 mm needed to be removed, which is quite manageable. The next version will come with a flange thickness of 10 mm, then there remains enough material so it can be resurfaced a few more times and remain usable.

Photos from first version to last version:

That concludes the blog about the manifolds. I hope in the coming month to be able to mount the manifolds, make uppipes and then show the test results.