Air Injection effect on AFR's?

[911st]

Was wondering if there is a factory procedure to disable the 930 air injection system when setting CO or testing AFR's.

Seems injecting air would through off readings for any wide-band system we might use.

Never thought about this before. Some run them, some do not.

[RarlyL8]

Is the air valve open when the engine is warm and at idle?
Never paid much attention to the event timing of the system but it may be a factor. I would think this also an issue if using air injection to reduce turbo lag. May need to disable or re-route some of the hoses for optimal performance enhancement.

[stevie 77 930]

After many years and dealing with rich condition, I had my Leask WUR dialed in from the guys at TRE. The AFS at idle 14.7 w/ air injestion blocked off. AFR's w air injection working 15.7 my car is a Calif car so I need the smog stuff intact.....

BTW..... my cruising AFR's 14.5 and WOT are 10.9 my MPG 's have gone from a miserable 10 mpg to 15 + mpg on my last trip.

[911st]

Interesting.

Then we have the later 930's with Lambda circuit. So if they are trying to maintain about 14.7 AFR, the motor might be running as much as a point richer.

If one keeps the air pump and is running a Wide Band O2 the info is going to be misleading.

I suspect it would be good to take the belt off the injection pump and set or verify the AFR's. Then reinstall.

I was wondering if this was addressed in the factory procedure for setting CO or checking AFR's?

I am wondering if the factory CO is what, 1 to 1.5% on a stock car and we set it at 3% on a car w/o the air pump, are they pretty close to the same thing?

I am also interested in the air pump reducing lag.

[911nut]

Originally Posted by 911st

I suspect it would be good to take the belt off the injection pump and set or verify the AFR's. Then reinstall.
I am also interested in the air pump reducing lag.

The Bentley manual says to disconnect the inlet hose on the air diverter valve before making adjustments.

On the 964 Turbo air is injected into the exhaust ports during warm-up only, then is diverted to the cat.
Even if one was to continuously inject air into the exhaust ports during running operation, the air on it's own would not energize the exhaust flow. Fuel would need to be added since the turbine is powered by rapidly expanding gas.

[911st]

Thanks Paul.

Lot easier disconnecting the inlet hose.

There is a graph of a study of he effects of the air pump on sool around here that indicates a positive effect of air injection on a 930. It dose reduce spool. However, it is belived to take about 5hp up top.