trigger wheels

I ended up going back to the original trigger wheel. This is a 12-1 wheel (that is teeth spaced at 30degrees but only 11 of them, so 12 teeth minus 1).

I rebuilt the LM1815 trigger circuit, this time putting in the proper input filtering 15kOhm with 2nF(why do they refer to these as 2000pF) capacitor. This yields a low pass filter with a cut-off of f = 1 / (2*pi*2nF*15kOhm) = 5.3kHz. As there are 12 teeth and max RPM is 12000rpm, this corresponds to 200 engine rotations per second, and hence 2400 teeth per second, each tooth gives sinusoid so the cut-off seems to make sense.

I am also using the adaptive functionality of the LM1815. My hope is that this will be less sensitive to slow cranking (something that can happen as the battery goes a bit flat). This does seem to work, and I have blipped the throttle to give just over 6kRPM.

Keen to test, but too many other things on at the moment.

In other news:

Refitted the exhaust and bolted in a baffle at the back end. The car is a bit loud at the moment, and also I am having some boost creep problems. A little more back pressure may help with the boost creep, and the baffle does help with the noise.

Also welded up a couple of holes in the down pipe next to the Lambda probe.

Next plans:

Sort out the tuning. Bit worried about the spark timing, as it is a pain to configure.

Paint underside of bonnet and fit heat resistant shield

Install intercooler brackets, work out pipe runs and get intercooler welded up.