The condition of the car's exhaust system was pretty rough when I bought her. On the dockside, the exhaust gasket returned a positive test for asbestos, leading the car's empounding. At the dockside, my mechanic friends removed the gasket and the asbestos lagging that was connecting the resonator cylinder (box) from the rest of the exhaust pipe. It appears that the pipe had been cut at some point in the past and repaired simply by wrapping asbestos tape around the cut. When I removed the whole exhaust system from the car when it was in storage, I found that the tail end of the pipe was held in place by a piece of canvas rope. It would have been swinging around quite a bit when the car was driving.
What I have discovered as I've slowly restored this car is that Auto-Union were constantly changing and improving the F89P between its introduction in 1950 and its replacement by the F91 in late 1953. This is revealed through the often vast differences between what is published in the owner's manuals and what is actually on the car. For instance, the ignition system was completely changed during the three years of production, starting with a distributor connected to the Dynastart in the earliest manuals, through to the tried and true condensors and breakers of the prewar period - something Auto-Union would stick with until the Munga was retired in 1968. Similarly, the exhaust system was completely changed over the years.
The F7 and F8 models had a straight through pipe from the engine manifold to the rear of the car. For the F89P model however, a resonator box was added. This box - or more accurately, cylinder - was mounted to the exhaust manifold and was designed to reflect the exhaust pressure wave back towards the engine, minimising the loss of fuel mixture as the cylinders were cleared. This simple addition did a lot to improve the performance of these small engines.
The resonator box on my car was in terrible condition, being badly rusted and with several tears and holes. I thought it would be a rather easy matter to have a new one replicated in Perth, but I was wrong. No one wanted to touch it and I was quoted some ridiculous amounts to replicate it... "if we have time." That's the polite way of saying "go away."
So it was back to the markets in Germany, but these parts are hard to find. Also, the box was completely redesigned in 1953 when the four speed gearbox was introduced, as the gearbox was larger and required neighbouring parts to be adjusted to fit. After much fruitless searching, I was referred to Holger Behnke of Old Car Ranch in Spremberg, Germany. Holger manufactures reproduction exhaust systems for DKW and IFA vehicles, but he did not have an F89P exhaust in his inventory, so I sent him the parts and within a week it was done.
The new and the old
I look forward to getting this back in the car.
And now Holger will have an F89P exhaust system in his inventory. You can check out his parts and services online here: http://old-car-ranch.de/
Update 1 June 2023 - It arrives!
The reproduction looks great and is of good, heavy-gauge steel. Thanks Holger!
