Rebuilt engine now installed and starts, but will hardly idle even at 2000RPM.

With the new half bridge and the related drop in vacuum, makes sense that the E8 is badly in need of retune.

Until May 26 when scheduled for Steve Kan tuning event, need to tune enough for the break-in to withstand the rigors performance tuning.

Will avoid boost until then, but can someone point me to the what to change to support idleing and running for break-in?

I have the software and maps on my laptop and I printed the manual.

 

Got over 800 miles on the halfie rebuild with the old street port map. Did an oil change at 400++ miles. Still idles badly and runs rough, but it looks like I'll have the 1000 miles and be ready for the Sunday Steve Kan tuning session and dyno run.

 

The increased overlap would require more fuel, since it's not as efficient at the very low RPM's anymore.
I'd recommend to add more fuel to your idle ranges to get it to stabilize.


-Ted

 

Have you modified the delayed opening of the stock TB secondaries? The stock TB holds the secondaries fully stut at idle & light throttle. You shouldn't be having these kinds of idle problems on a half bridge if the secondaries throttle plates are fully shut like they should be.

 

Actually with a BP you will have to decrease the idle fuel amount due to it having lower vacum and now the motor will idle in the area where you would normally add fuel on a street port map. Most likely decrease fuel in the -4 to -6 psi area. Start with what you had with the street port at say -7 to -8psi and apply that to the lower vacum area basically making all the load ranges flat from -8 psi to -4 psi.
One of things that helps a BP to get an even better idle would be to use the zero TPS idle map. In doing so the normal load map abovef zero TPS position won't affect the idle.

 

Also, another little thing to try is bumping up the timing just a bit around the Idle load/rpms that way you get a little better throttle response and better idling.