eractic reading from tach while starting
 

Ive recently got my 13bt E6k powered 1st gen running and have a few problems. I have downloaded one of Hitmans maps 13bt 4 720s and stock ignition. First time I went to start the car it took about 10 sec and then fired up. I noticed during cranking the the stock tach would somtimes bounce around between 1000 and 5000 rpm. The haltech manual says to check if you are getting a clean signal from the CAS by cranking the car with the injectors off and watching the rpm on the data screen it should be between 100 and 300 rpm and not be eractic. I did this and its at about 150-160 while cranking yet the stock tach somtimes bounces around is this ok? The other problem im having is at around 5-6k rpm and 5psi my car starts misfiring like crazy and bucking a little could this be the timing. Reving with no load from idle to redling is fine no misfiring or hesitaion at all. I did zero out the timing like it said on hitmans site but I dont know if I did it correctly. With the timing locked at -5 and the trigger angle at 65 I rotated the CAS until the timing pointer was on the yellow mark then I turned the timing lock off. This is all I did to zero the timing i changed nothing else and im unsure if i did this correctly.

how did you wire up the tach? is it the stock tach wiring or the haltech tach output? my 20b uses the e6k output for the tach and it seem to be flakey, sometimes its really low and sometimes its high.

mike

The tach is wired to the negitive side of the leading coil just like the original tach.

You should wire the stock (FB wire) tach wire to the 2nd gen coil packs tach output... I beleive its yellow?> on the FC coil pack

The stock t2 coil packs tach output is on the trailing coils. I was told that if I wire it to the trailing it would only read half of the rpm that the engine is turning because the 1st gen tach reads from the leading coil. On the T2 coils leading coil there is a small bullet connector that does not go to anything on the original t2 harness. That wire I traced to the negitive side of the coil so I wired it in there. It reads fine while the engine is at idle or reving it only bounces around somtimes while trying to start the car. Thanks for the input though maby just for the hell of it ill try it on the trailing coil stock output. Does anyone have any ideas on the upper RPM misfire while under boost? Or if I set the base timing right? This has me more worried than the thing with the tach. MIKE-P-28 I read your thread on setting the timing and inserting the CAS maby ill try the method that the hitman suggested to you.

when crankings, isn't the tacho on a 1st gen a voltage meter? when ya turn the key on it gives a voltage reading then the RPM signal over rides it or something along those lines

I have a S3 84-85 it has a seprate voltage meter. I think its the S1 that does that.

the stock fc has the tach output on the trailing coil, its a yellow wire with a tracer (either white, or black), the leading coil on an fc outputs twice as fast/much as the leading on an fb.

mike

79 and 80 (SA) only do that, 81-85 has a voltmeter that reads all the time :)