I have done a bit of reading and see that people seem to be divided on the issue of venting blow off valves to atmosphere with the FC's AFM. Can I get some comments on the issue, maybe from personal experience? Anyone tried it and then had to change to a recirculating setup?

Thank you,
Daniel

 

You can run a atmospherically vented bov on both s4 and s5s no issues on either of my cars just buy new not used because if they leak teu can cause all sorts of issues

 

With the OEM mass airflow type of engine management system, the air-fuel ratio will go rich whenever the BOV vents to the atmosphere. This will cause a slight hesitation under acceleration, but there is no documentation of any damage caused to an RX-7 by this effect. Most people who vent the BOV to the atmosphere do not have the driving experience to tell the difference, and they are just happy making noise. Therefore, there is not a debate about what happens, but rather a choice about whether you care or not.

In order to vent to the atmosphere without throwing off the air-fuel ratio, you would need to either install a piggyback fuel computer that will compensate when the BOV vents, or convert to a standalone EMS that uses a speed-density or alpha-N fuel metering system.

 

? Slight hesitation under accel? But your not accelerating when the bov is venting :s

 

The BOV vents during shifts. If you are upshifting, then you are accelerating. The faster you get back on the gas after the shift, the more you will notice the hesitation. If you upshift like a grandma, then you will not notice it. The effect is also reduced at lower boost levels.

Also, if you let off the throttle while still in gear and the BOV vents, and then quickly get back on the throttle, there will be a bit of hesitation or stumble as the car attempts to accelerate. However, this situation is not a likely event unless you are road racing, in which case you will probably be running on a speed-density standalone EMS anyway.