Okay, it's been established that cams on a stock car are safe because of factory rich conditions. What if I wanted to install cams in between custom tunes? Since my A/F has been leaned out will the extra air from the longer duration cams (272) take me dangerously lean? I'd have to drive the car at least a month like this FWIW.

 

I would wait.

l8r)

 

You'll be fine.

Any extra air will be metered air, so the corresponding fuel based on your tune will be added.

The only issues would be if you are now moving more air than your fuel supply can keep up with.


Eric

 

Shouldn't be a problem with the walbro. I considered setting my mbc lower as an extra margin of safety during that time.

 

[QUOTE=l2r99gst]You'll be fine.
Any extra air will be metered air, so the corresponding fuel based on your tune will be added.
The only issues would be if you are now moving more air than your fuel supply can keep up with.
Eric[/QUOTE]

The MAF meters all air passing through it. Under partial throttle conditions, the ECU constantly is adjusting the fuel being injected to achieve the Stoichiometric ratio based on residual oxygen as interpreted via the O2 sensor.

However, AFAIK, the above adjustments only hold true for partial throttle conditions. Once the TPS indicates wide open throttle..then the O2 sensor is out of the circuit and the ECU reverts to the particular values in your fuel map. It relies on predetermined fuel lookup values and no longer does any adjusting toward stoichiometric take place.

So, It could be that your flash is too lean for the extra air from your cam upgrade. But, I may very well be mistaken. Better to ask your tuner.

 

The open-loop (WOT) fueling does use the fuel tables for look-up, but the tables are RPM and load. The load is roughly proportional to mass air flow. It uses the airflow from th MAF, so you will still get the same amount of open-loop fueling with new cams as with the old ones.

You may be in new load cells if you are flowing more air, but the same tune will be in effect. If anything the higher load cells would be tuned more conservatively, so they would be richer as well as the timing maps would be a bit more retarded.

As I said, he will be fine.


Eric