Playing with crystals in 2ZZ-GE engine ECU
Based on a topic posted a week or so ago wherein someone had eliminated their fuel cut-off in a 2002 GT engine, I decided to tackle the ecu in my 2002 GTS (which has the low 7800 rpm cut-off). Here's how it went:
Based on the original article, I replaced both of the 16 MHz (#1 and #2 in the photo) crystals with 18 MHz. I went out for a drive and to my delight discovered that the 7800 rpm fuel cut-off was gone, or at least high enough that I didn't want to go there. Unfortunately, on the next trip through the tachometer I realized the VVTL-i kick in went up about 1000 rpm to 7200; sort of defeating the purpose of the higher redline. This made me think that perhaps one crystal controls fuel-cut off and the other, valve lift threshold.
I next put the original 16 MHz crystal back in position 2, leaving the 18 MHz in position 1. This caused both the fuel cut-off and valve lift rpms to go back to the original 7800 and 6200 resrectively. i.e. no different from having the two stock 16 MHz crystals.
I then swapped the 16 and 18 (16 in position 1 and 18 in position 2). The fuel cut-off was again gone and the valve lift started at 7200 rpm. Again, pointless.
Both of the original crystals (16 MHz) are now back in the ecu and my fuel cut-off is still 7800. If anyone else has discovered how to get rid of the fuel cut-off while retaining the same VVTL-i threshold in the GTS engine I'd like to hear about it.
...and before you respond "buy an APEXi Power FC", I'm saving up for one as a Christmas present to myself. I also already know about swapping in a 2000/01 ecu and oxygen sensor. The motivation for changing crystals is that they cost $2 apiece and the work takes 10 minutes.