Injector Dead Time 2/4 Squirts

Today I had a look at a few things to do with the tune of the EFI.

  • I never had time (unless I did but have forgotten) to find out how accurate my dead time settings were after my previous static testing. Well, one way to test if you have the dead time right is to tell the ECU to squirt only 2 squirts per cycle (I’m currently running 4 per cycle), and see if the engine idles smoothly and at the same A/F ratio (14.0:1 is what it is set at). When I first did the change, I thought I’d done something wrong, as the idle and AF ratio stayed the same. I then noticed that the injection pulse width had nearly doubled when on the 2 squirts, this meant that the dead time was spot on! Yeah! On the MegaSquirt extra forums they constantly say to get your dead times right.
  • I and ran the auto tune program, whilst driving around the local area and down to Werribee South for lunch by the sea. Initially it was a bit reluctant to rev out past 4000RPM, but soon no problems going to 6500 RPM (I don’t like taking past 6K, but I just had to see if it would go there!) and AF correct. The VE table now looks like it should, especially at the lower load points, also it has less peak and troughs. I need to do a bit of further tuning, mainly in the higher load/RPM areas, but It’s quite drivable as is. Wish there was more hills around here!
  • In the process of tuning the car, I checked and set the fuel pressure to 14.7PSI (same as the Rover SPI… 1Bar). I noticed that above 11PSI or so, that the needle of the fuel gauge started to shake by a bout 1.5 – 2 PSI. I have a feeling that the SPI pump is a bit up the shit, or maybe it’s the fuel pressure regulator. Either way it’s about time I got the fuel pressure sensor screwed in and wired up to the MegaSquirt MSX board that I have recently purchased. The MSX board has additional A/D inputs and digital I/O’s needed for this and when I go the MAF route. The ability to monitor the fuel pressure will allow me to see if I have sufficient pressure/volume.

Cheers, all comments, criticism welcome!


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