Hi guys, I got to drive my 327 tpi conversion today for the first time. It runs surprisingly well for a chip I had burned through mail-order.

Question: Do I set the minimum air flow with the engine in closed loop or open loop? With the engine in warming up in open loop, I set the minimum air such that the engine was idling around 600 rpms with the iac closed and disconnected. My target idle speed is 750 rpms, and the engine actually stays right around 750 in open loop. When I get into closed loop, the idle rises until its about 1000 hot. Should I have set the minimum air flow hot (I'm guessing I might have the throttle blades open too far and the iac, which is probably closed, can't do anything to bring the idle speed down. )

Other than the idle speed issue, the car runs excellent. My semi-siamesed and heavily ported base has no problem letting the engine wind to 6000 rpms with stock runners. Its pulling strong to 5500, when I shift (My cylinder heads are waaaay overkill for TPI, but still, I'm impressed that the TPI is just as strong up to where my hydraulic cam runs out of power as a carb with a performer RPM manifold.)

 

Get the engine fully warmed up and then set the min. idle speed. 600 RPMs cold could easily be 900+ RPMs warmed up.

Only way to know for sure would be to put a scanner on it and see where the ECM is trying to get the idle (i.e, IAC setting).

 

Hi Damon, thanks. By the way, you're located near me. I am a senior mechanical engineer at Villanova. You're right, my nearly cold 600 rpm base idle is probably around 900 hot. What I was trying to correct adjusting the minimum airflow cold was surging during open loop. I guess this may just be normal considering I'm running a long duration flat tappet hydraulic cam thats pulling ~12" at idle with 22 degrees BTDC timing pulled in.