Air fuel ratio affected by air pump
 

Hi

I have a 305 tpi with paxton sn2000. Everthing stock except for injectors and full exhaust with air tubes on headers.

I am assuming the air pump will give an articially lean afr based on the air being pumped in. I am not sure what percentage of air is from pump and what percentage is from cylinders.

Is this being to detailed or will the air pump have an impact

I think the paxton can deliver 850 cfm

Re: Air fuel ratio affected by air pump
 

I think it switches pumping air to the cat after warm up. Do you have a Wideband 02 sensor somewhere in there?

Re: Air fuel ratio affected by air pump
 

I am installing a stand alone wide band downstream of narrow band in cat area to help with tuning (innovate mtx wideband afr meter)

Re: Air fuel ratio affected by air pump
 

The AIR pump doesn't put air into the exhaust upstream of the O2 sensor during closed-loop operation.

Re: Air fuel ratio affected by air pump
 

Just keep it away from the cat and you should be good. Also, before the switch to closed loop your afr will be off like you were thinking.

Actually, that's a good question. I'd think whenever the air pump is discharging to the manifold tubes, the sensor will see the added air and it'll go slightly rich. Should have no effect when it shifts to the CAT....assuming it's shifting as it should...

Re: Air fuel ratio affected by air pump
 

So in closed loop air pump goes to exhaust manifold and power enrichment air goes to CAT?. I am more concerned with what is happening in PE mode

If anyone can confirm that would be great

Re: Air fuel ratio affected by air pump
 

i would like to know those answers too.

Re: Air fuel ratio affected by air pump
 

No. Air is pumped into the exhaust manifold during startup... to help burn any still unburned fuel. This also helps heat/light off the cat. There are time and temp sensor measurements programmed in to the memcal, at which time the computer goes into "closed loop" mode.

The O2 sensor will NOT be accurate while pumping unmetered O2 into the exhaust upstream from the sensor (manifold), so this is cut off once the computer wants to use the O2 sensor.

The air pumped into the cat makes the 3-way converter more efficient. This will have no effect on the O2 sensor since it is downstream.

I cannot say with authority whether the O2 sensor is used during PE mode. I tend to think not.

Re: Air fuel ratio affected by air pump
 

BLM is however. in the PE calc of AF it looks at the last BLM recorded just B4 going to PE. If over 128(adding fuel) it uses that BLM and if under 128 is uses 128.