3.2 conversion cars, Public service announcement Options

[mepstein]

We have 20 bad ecu's (3.2 engine computers) in the shop. I sent a couple to Steve Wong / 911 Chips for repair. He asked if they were from a 914-6 conversion car since they had a particular defective part. They weren't but most of our cars are 3.2's into early 911's so sort of the same idea. Steve said the reason we were blowing ecu's is because we were mixing the ecu's with a non 3.2 tach. It's very common for a 914 conversion to either modify their 4 tach with an electronic unit or modify an early tach to work with the 3.2. Steve said it may work for a short time, sometimes longer but failure often happens at high rpm. Go to the track, ralley or just some spirited driving and the higher rpm's kill the ecu's. I have to believe him since we have a pile of them to prove it. We had one burn out after 1.5 miles. Even hooking up the shift light wire on the 3.2 tach incorrectly will burn up the ecu's. Not right away but over time. A rebuilt ecu runs $900 and the burnt core is worthless. It's a known problem so it isn't accepted by most, if not all of the ecu rebuilders. You also must use a coil for a 3.2. No substitutes. All of this was unknown to me and the guys at my shop until today but you can be sure they will be more careful about this in the future. 1 more thing and it's something we did already know and practice, always remove the battery terminal from the battery when connecting your ecu.

[larryM]

WOW - thanks!

curiously - Steve never raised the issue when i b'ot the chip a couple months ago - and he knew it was going in a 914-6

has anyone yet checked to see if NHS or PAS can put new 3.2 guts in our older tachs? - at what price?

last nite i b'ot the only used 3.2 tach on ebay from msroadrace -
expensive but half the price of replacing my 28-pin 082 DME with Wong chip in it - - call it insurance


fwiw - currently running oem 911/914-6 tach that is orig'l to car; it's been fine with the 3.2 for 3 yrs, but not many miles, nor sustained high rpm like we'd do on track-

i have 2 good spare 3.2 DME's as well - looks i can let one go now!

, (and dump the spare SC tach as well - sounds like it is useless with the 3.2 DME)


wiring diagram for 3.2 tach here
http://forums.pelicanparts.com/porsche-911...tml#post3972081


p.s. - here is a good link from one of our colleagues http://forums.pelicanparts.com/porsche-911...lity-chart.html

to wit:

"5. 1978-1983 Tachs. These are driven from the "TD" tachometer drive output from the six-pin CDI box because the points were eliminated in favor of a magnetic reluctor. According to the following thread, the SC tach signal is the same as the later Motronic:SC Thread

6. 1984-1989 Tachs. These are driven from the Motronic box. Chris Bennett posted the Motronic signal here: Motronic Thread"