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Weldini
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Discussion Starter · #1 · (Edited)
Anyone have the pinout for the 2JZ-GE distributor plug? Trying to get an aftermarket external tach hooked up and not having much luck. The car runs on LS1 coils using the distributor as a cam/crank sensor and is running on a 30-1100 AEM box. Yes I realize I can get the stock tach to work, no I'm not interested in doing so. We've gotten the tach to read 500rpm via a few different tap points, but the car idles around 1000rpm. This is the tach I'm using:

http://www.oreillyauto.com/site/c/detail/EQU0/6088.oap?ck=Search_N0531_-1_-1&pt=N0531&ppt=C0134

Any suggestions where to tap into the wiring to get a good RPM signal?
 

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Speed limits = Guidelines
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From my understanding most afternarket tachs run off the coil pulse...not the cam sensor as that would differ for differnt makes/models

Coil packs are differnt as u can't get the 3 pulses per rev needed to generate a tach signal by tapping off a single coil

Ls1 coils have built in ignitors don't they?

If this is the case the tach output on the aem box is what you need
 

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Speed limits = Guidelines
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its not an issue of interpreting the signal...the tach should function from the pulse of a single coil...the problem is how many times that coil fires per 1 engine revolution

a universal tach made or set for a 6 cylinder engine is converting 3 coil pulses into 1 engine revolution on the gauge...the reason for it being 3 is that a 4 stroke engine requires 2 revolutions to complete a cycle

if you tapped off the a single coil on a wasted spark coil pack set up, you would be only getting 1 pulse per rev instead of 3...the reading on the gauge would wind up being a 3rd of the actual rpm...so at 3k engine rpm the gauge would read 1k

you need a tach signal that pulses for all the coils, not just 1 wasted spark pair

normally the igniter would provide this signal, but having individual igniters that leaves only the AEM box capable of sending the output signal

if you search around a bit you should find the info you need on which pin to tap the signal off of
 

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Weldini
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1,290 Posts
Discussion Starter · #9 · (Edited)
I've been searching and looking at schematics for an output that will work but haven't found anything conclusive. From what I can tell, pins 57B/58B are RPM signals, but I have yet to find somewhere to verify this. Am I looking in the right spot?
 

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Speed limits = Guidelines
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looking at the pinout it says 57b is another output for coil 1 and 58b is unused...the problem with 57b is its only coil 1, to get an accurate signal you need all 3

maybe its possible to join all 3 secondary outputs into 1 signal wire...this would only work if they are not connected to the other set of coil outputs, or you'd be firing all the coils all of the time...definitely needs to be confirmed before attempting

it would be a good idea to talk to an AEM tech about this
 
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