ECU & Tach Signal

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reckedracing

reckedracing

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Does anyone know if the ECU receives a tach signal?
The manual Says the tach signal is something like 100 rpm for every 250 pulses from the igniter, but I would think the ECU receives a signal too.
What pinout is the signal?

I am also wondering what pinout on a P28 is the O2 signal?
 
blue wire off the tach on obd1. not sure for obd0

pinouts are in the reference scetion.... but you knew that, right?
 
yea, i pulled the pinouts from above from the refrence section...
i'm confident on the O2 singal...
but i'm still thinking the "tach signal" doesn't enter the ECU at any time...
i think the ecu sends the ICM (ignition control?) signal, but that does not correspond correctly to the rpm's
am i wrong? should i just run a tach straight to the blue wire in the engine bay?
 
tach singal does enter the ecu - has to. how else will it know when to rev limit? :p not sure on what wire brings it though. but the blue wire goes to the cluster. tap off that for your tach lead.
 
ah yea, that does make sense...
i figured it had to for the vtec switch-over, never thought of the rev limit, but i'm thinking the ECU gets the ICM signal which does not correctly correlate to RPM...
i dunno, nevermind
lol

thanks for the help B
 
I can't add the image, but the engine speed output signal (RPMs) does not enter the ECU at all. It leaves the Ignition Control Module in the distributor via a solid blue wire and from the splice goes to the tachometer, the cruise control box (if installed), and the tach test connector (white 2-pin connector) on the driver strut tower.
 
I have an obd1 civic dx. For my tach install, I had to tap into the blue wire on the engine harness. The wire is located on the drivers side shocktower set of plugs.
 
I need to clarify myself before I am corrected. The RPM signal from the dist does not enter the ECU. I would imagine the ECU gets RPM input from the CKP or creates its own using output to the injectors.
 
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