at what vacuum reading do you need to switch to Alpha-N mode with DFI?

  • Thread starter SingleTurboIroc
  • Start date


Just curious. i'm helping pick out a wicked cam for an all motor car but i have no idea how to tune in Alpha-N mode and wanted to know at what vacuum reading is it necessary?

i was told at about 5" of vacuum and below. sound about right?

Hey Mr turbo;) You sure it ain't for your car.:cool: very very quiet.....i'm huntn' rabbit in here ;)

I already got some answers on good old trusty
thank you very much :D
I run speed density with about 4.9" - 5.3" of vacuum and am getting the tune up dialed in quite well. I messed with tuning in Alpha mode for a few days but it seems to work just as well with the speed density. I talked to Mike about this at F.A.S.T and he said it sould work just fine at 5".
Deciding what level of vacuum is acceptable for speed density operation is largely a matter of personal preference. You will run into dynamic range problems without a big change in manifold signal but the interpolation really helps out here. With the FAST system speed density mode, the injector resolution works out to be 8 microseconds and this also helps out. That's ultra-fine control for small changes in signal.

So try it. If you can live with the throttle response and driveability, your good to go. :cool: