sammytcl

iTrader: (1)

Did anyone try to remove permenantly the secondary air injection system? I found two versions on the function of the secondary air injection system:
1. pump air into exhaust to help burn the unburn fuel going into the cat.
2. pump warm exhaust gas to the engine to help warm up the engine when cold.

From looking at the service manual, it looks like the first function is what it does. If that's the case, then can we just remove the entire system for the following set up:

Turbo charged with no cat and a wideband o2 sensor - if a wideband is used to monitor the a/f ratio, having the pump blowing fresh air into the downpipe will result in inaccurate a/f ratio read by the o2 sensor. Hence remove the system and block the downpipe opening should give an accurate a/f reading, and thus more accurate for tunning.
If this theory is true, then is the stock computer going to do anything on the engine mangement, under both set-up: emanage & interceptor?

On the other hand, if the function is to blow air into engine/intake, then forget it.

Thanks and regards,

Sammy

StealthTL

iTrader: (1)

The air pump only functions for the first few minutes of a trip. It adds air, as you noted, to light-off the cat as soon as possible. The computer knows it is "doing it's thing" and is not confused by the extra air - the computer takes over the mixture adjustment, after the pump shuts down. Exhaust pressure and the check valve prevent air from the downpipe after it is stopped.

If you disconnect the piping, it will not affect the ECU, but if I recall, it will trip a CEL if it isn't connected electrically.

S

TeamRX8

iTrader: (25)

I thought somebody here installed the OBX header and got a CEL, seemed like the rear O2 sensor knows when the secondary air system is suppose to be doing it's thing and if it isn't the CEL is thrown

MadDog

If the air being pumped into the exhaust doesn't mix well before it encounters the WB02, then a CEL will be thrown. This is what happens to some GReddy owners. The GReddy downpipe put the air injection too close to the WBO2. The PCM sees the mixture as too rich since the air isn't mixed well - it should be reading quite lean when the sec. air inj. is operating. The PCM therefore thinks that the sec. air inj. system is not working and voila: CEL.

TeamRX8

iTrader: (25)

IMO this is exactly why the exhaust port/gasket/manifold has all the mis-sizing issues. I believe Mazda is intentionally creating shear turbulence as the exhaust gasses exit the engine to get the secondary air fully mixed in and exhaust gases homogenous.

MadDog

I just wanted to add something to this re the CEL. Apparently, the PCM doesn't look for the effects of the secondary air injection if the throttle is in use. If you get a secondary air injection CEL, clear it and then follow the procedure below to prevent it from returning.

When you start cold, the CEL won't be thrown if you keep your foot on the throttle lightly, or if you just start moving instead of letting the car idle at a standstill for too long. The secondary air injection system goes off in a couple of minutes, so you're in the clear after that time has passed. The idea is to make the PCM believe that the exhaust is rich for a reason.

TeamRX8

iTrader: (25)

interesting, thanks

Charles R. Hill

iTrader: (7)

I thought the pump only ran for the first 30 seconds after a cold start.

CRH

sammytcl

iTrader: (1)

i am using interceptor with the greddy turbo. so if i take out the secondary air pump completely and block the inlet on the down pipe, is there any concern/problem other than a cel (i am having one all the time anyway, so i don't care)?

Like Whoa

after engine is at operating temp it should shut off unless it fails the passive test. it then goes thro an active test which basically cycles air flow to exhaust manifold on & off during closed-loop. when it turns on STFT should read a rich condition. if the active test is failed 2xs MIL should turn on.