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I've got an 87' FC S4 with failing catalytic converters that I want to remove, and in my searching here I see the actuators and sleeves for the 5th and 6th ports are operated by the back pressure of the exhaust through the fresh air injection tube going to the converters.
If I remove the converters replacing it with a piece of straight pipe, and drill a hole for the fresh air tube, and re-weld it back in the stock location, IS there going to still be enough pressure to operate the actuators??
Or does this have to be relocated to another area of the pipe to get proper back pressure?
Note: This car is completely stock, which includes the mufflers.
Last edited by 7's & 9's; Jul 26, 2019 at 10:48 AM.
Reason: spelling
If I remove the converters replacing it with a piece of straight pipe, and drill a hole for the fresh air tube, and re-weld it back in the stock location, IS there going to still be enough pressure to operate the actuators??
Or does this have to be relocated to another area of the pipe to get proper back pressure?
Note: This car is completely stock, which includes the mufflers.
From what I've read on here the answer seems to be no. That won't work. Here is a post I made on the subject years ago that explains a little.
On a n/a you'll want some sort of pre-silencer or muffler somewhere before the main mufflers at the rear to help cut the noise down. As to the tube for the auxportactivation on a S4. The Racing Beat pre-silencer for the 86-88 cars have it, the universal ones do not. Also you could make your own tube but you can't just drill a hole and weld a tube to it. This is why I believe some after market exhaust doesn't work with the actuators. It's not backpressure it's the tube setup. Their( RB) tube bends 90 degrees once in the exhaust path so the opening of the tube is directly in the exhaust flow. Seems they are using the exhaust pressure to open them, not backpressure.
Thanks DAK, and this morning while having coffee, I poked around the interwebs and saw exactly what you were talking about, so really my only so called fix is to buy the RB set-up or go the route of deleting the actuators and sleeves (not my preferred route)
I can clearly see the tube you were talking about here in this picture........
That is correct, there is not enough pack pressure for just a tube on the side of the pipe to work. You will need to have some sort of pickup tube inside the exhaust stream like in the RB presilencer/DP combo. I've had that on my '87 back when it was NA and it worked great. It is a very high quality product.
There is also an option to rig something using an air pump and some RPM - activated switches. I did it over a decade ago, after I swapped on an S5 intake, based on some plans I found somewhere on the forum. That worked well and opened them exactly at the right time, but it was a lot of work and planning. It also ended up costing me around $100 in parts, but YMMV, I mostly did it because I enjoy projects, so unless you do as well, the RB product is your best bet.
Last edited by Sideways7; Jul 28, 2019 at 09:05 PM.
Reason: Words
i have a lumbar pump hooked to mine, going to a tank and higher pressure pump controlled by the ms3 pro.
I got a cheap 12V air compressor pump, but I've heard good things about the lumbar pumps. I got a basic RPM switch off Summit, but, again, that was 15 years ago so I'm not sure what's out there now.
FYI, if you choose the air pump route, make sure you have something to bleed off the pressure, otherwise the ports will stay open. I poked a hole in the hose between the pump and the actuators, but I'm certain there are more elegant methods.
I got a cheap 12V air compressor pump, but I've heard good things about the lumbar pumps. I got a basic RPM switch off Summit, but, again, that was 15 years ago so I'm not sure what's out there now.
FYI, if you choose the air pump route, make sure you have something to bleed off the pressure, otherwise the ports will stay open. I poked a hole in the hose between the pump and the actuators, but I'm certain there are more elegant methods.
Thanks Sideways, I think it was either your article or someone else's that talked about that, but was using a fish aquarium 3 way valve to bleed off pressure, I ran across that modification when I was searching for infomation about the 6 Port Actuators.
I also notice we're kind of neighbors, I'm down in Bastrop, I have a friend who live in Belton
Depends on your setup. My SA with 13b EFI and Racing Beat 79-80 exhaust has functional aux ports with a fitting inserted into the presilencer and metal pipe to the actuators. I have tested it by putting zip ties around the rods and they moved after a drive.
84-88 ELECTRIC 6 PORT CONVERSION Here is a link to the Rotary Resurrection website with all the info you need to convert the 5th and 6th ports to compressed air.
