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Old 08-12-2008, 06:31 AM   #7
58mm of Bliss
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Join Date: Jul 2003
Location: PEI,Canada
Posts: 4,360
My Ride: 330i, 330Ci
Originally Posted by F1004fun View Post
when the secondary air ground signal is sent from the DME it triggers the relay for the pump. Well I used that ground to energize a DPDT relay that interupts the front 02 sensor signal line with a voltage signal of my own
I'll explain what I'm getting at in greater detail:

On cold startup, the engine needs more fuel to run smoothly. The air injection pump adds air after the combustion process to an exhaust mixure that is still fuel rich. This allows the cats to more effectively burn off excess fuel. The volume of air added is actualy in excess of what is required for a stoich burn, the result is a higher burn tempurature in the cats. The purpose of this is to bring the cats up to proper operating temperature sooner.

The DME looks at the post cat sensors at a certain point in the warmup sequence, and if the signal doesn't match what it's expecting, it will trigger a code. The front, or pre-cat sensors have nothing to do with this. They are expected to be "off" until the warmup sequence is complete. Using a dual pole/dual throw relay is a bad idea.

Originally Posted by TxZHP04 View Post
You picked an interesting member to debate weight removal with....
What the heck do I know?

Last edited by PEI330Ci; 08-12-2008 at 06:33 AM.
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