Manually operate the SAI pump? - 986 Forum - The Community for Porsche Boxster & Cayman Owners

geraintthomas · 02-06-2020, 11:11 AM

Question: could I manually operate the SAI pump via a switch?

Reason being is quite a shameful one, but it's something I need to ask to weigh up the pro's and cons.

Basically, have you noticed when the SAI is operating, the exhaust pops and crackles due to the air flow? Not sure why this happens, but whenever I hear the pump switch on behind me, I normally give the throttle a tickle (in traffic) and it crackles quite charmingly. Yes I'm a kid.

I thought of an idea of buying the exhaust dash button and linking that up to manually operate the SAI, so that you can enable/disable the exhaust crackles.

Only thing is, I'm not sure if that would do any damage to the exhaust? Or if there's any valves that would also need operating to allow the air flow, or if it would just be a case of powering the pump?

I'm totally aware it's quite a childish request, but the end product would give me a sort of 'sports exhaust' button if I go on a blast on mountain roads.

Just a thought...

thstone · 02-11-2020, 08:58 PM

In normal operation, the secondary air pump will operate under two situations: (1) At cold start to reduce emissions, and (2) to pressure test the integrity of the SAI and fuel vent system. There are valves that need to be set for the system to operate as intended in each case.

It seems likely that you could set up a dash switch to power on the pump and set the valves to allow the system to operate in the cold start mode.

The SAI pump is controlled by a relay. Send power to the relay and the pump will turn on. Check a wiring diagram to see if the valves are also relay controlled or directly powered (my guess is they are directly powered) and similarly set them to the correct configuration.

Someone here on the Forum probably knows which valves need to be open and which are closed during cold start operation. Alternatively, you can manually check them by using a Durametric to manually power on the SAI pump and then checking to see if each valve is on or off.

I do not know what effect this modification might have on the catalytic convertor.

geraintthomas · 03-28-2020, 08:58 AM

Quote:

Originally Posted by thstone

In normal operation, the secondary air pump will operate under two situations: (1) At cold start to reduce emissions, and (2) to pressure test the integrity of the SAI and fuel vent system. There are valves that need to be set for the system to operate as intended in each case.

It seems likely that you could set up a dash switch to power on the pump and set the valves to allow the system to operate in the cold start mode.

The SAI pump is controlled by a relay. Send power to the relay and the pump will turn on. Check a wiring diagram to see if the valves are also relay controlled or directly powered (my guess is they are directly powered) and similarly set them to the correct configuration.

Someone here on the Forum probably knows which valves need to be open and which are closed during cold start operation. Alternatively, you can manually check them by using a Durametric to manually power on the SAI pump and then checking to see if each valve is on or off.

I do not know what effect this modification might have on the catalytic convertor.

Can't believe I missed this reply - thank you!

I'm not bad with electrics in general, but following automotive electrics is a minefield to me, so I'd need the help of another.

I wonder if anyone here would be interested in looking into this for me?

And you're right with the catalytic converters, but if this wouldn't have a huge effect, this could be a lovely mod to have indeed.