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Old 07-31-2011, 04:50 PM   #68
Bullet Ride
Cars in Perpetual Repair
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Join Date: Nov 2007
Location: Guelph
Posts: 5,995

I was able to get the LM1815 circuit figured out (thanks to Matt Cramer). The Opto GND needed to be off, and the Relay 3 output needed to be wired to Opto -. with a 470 ohm, 5 volt pullup in the R3 slot.

However the I still had the same issue as before when using the LM1815, I was getting a sync loss which was preventing the car from revving past 2500rpm.

So I switched back to the original circuit and started playing with the resistor in series with the VR+ signal. Originally I had a 16k resistor. The application guide on diyautotune said 18k, which I didn't have, so I tried the next highest one I had which was a 22k. No change, same issue. So I tried the next highest one which was 33k and with that it was even worse, the car would experience the sync loss around 1500rpm. So that made me figure it's not an issue with the voltage in the signal being too high, it was being pulled down too low. I tried switching over to a 10k resistor and guess what.... she can rev freely now!!!

I was so relieved to get past this hurdle. I took the car for a quick rip up the road so I could finally feel some boost. It pulled nicely, but I wasn't in it too long until my car all of a sudden wanted to rev up to redline by itself. I shut it off and pulled over, a quick look at the engine showed that the tube from the ICV popped out of the manifold, I shoved it back in and drove the car back home. Time to buy some RTV, make sure everything is sealed up and start tuning
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