MicroSquirt.com read only forum (Jan.15,2018)

Hello again

I have a MS2 controlling fuel and ignition on a 4.0L Ford straight 6 with a broadband manifold with the intake runners switching from long to short at 3800rpm. At the moment I have a good (but safe) tune and will be looking to start squeezing a bit more out of it soon. I am wondering what changes I should be looking to make to the tune (particularly timing) for short and long runners.

Thanks,
Mark.

Set the AFR and timing on the short ports, then redo it on the long ports. These will be 2 separate maps.

Then, load the short port map and do a dyno run. Then, load the long ports map and do another dyno run. Where the torque curves cross between the two runs is where your switchpoint should be.

This gives you optimization for speed, but not necessarily for comfort. If you don't like the engine's behavior from a comfort point of view as it switches over, then you can either move the changeover point or add resolution in that changeover area and "detune" the post-switch area for a few hundred RPM to facilitate a smoother transition.