LS coils - Tach Issue - Miata Turbo Forum - Boost cars, acquire cats.

Welcome to Miataturbo.net   Members
 


ECUs and Tuning Discuss Engine Management, Tuning, & Programming

Reply
 
 
 
LinkBack Thread Tools Search this Thread
Old 03-30-2013, 11:51 AM   #1
Junior Member
Thread Starter
iTrader: (10)
 
Join Date: Jun 2011
Location: Detroit Burbs
Posts: 300
Total Cats: 3
Default LS coils - Tach Issue

I have done some searching, and some troubleshooting, but can't figure out how to make the stock tach work.

Details:
-'90 1.6L car (now has 1.8L VVT engine)
- Custom standalone ECU - uses 0-5V digital outputs for spark control. Stock ECU gone.
- GM LS coils - the badass ones with the heatsink on each coil. Standalone wiring between the ECU and these coils - no stock wiring interaction.
- I have the ECU driving both the stock 1.6L coilpack through the factory wiring and the GM LS coils in parallel. Ignitor and factory wiring harness has not been touched. Jumper harness used for ECU.
-Pin 2I on the ECU side is not connected to anything (BLK-WHT wire Pin E on the ignitor) - Ignition sense?
- I just physically unplug the set of coils I am not using - unplug the 1.6L coils at the 3 pin plug, and the GM coils at the stock GM 16? pin plug. Plug in the coils that I want to use.
- This provides me with the ability to use either ignition source, and no factory wires have been hacked. Yes - it was probably more work than required, but I really dislike hacking the harness if I don't have to.
-The engine runs just fine with either set of coils


The problem:
-The tach works fine with the 1.6L coil plugged in.
-The tach does not work at all with the GM coils plugged in, and 1.6L coil disconnected.

Based on some reading on here, it looks like I might need a 12V pullup for the ECU pin 2I. But, I put a 1K resistor in the diagnostic connector between B+ and IGN- and no help there. Also, since the tach works fine with the 1.6L coil plugged in - this wire isn't needed??

So, I'm looking for some advice. I understand that I could use the tach out pin on my ECU and run that to the diagnostic connector in order to drive the tach. Maybe I will do that. But, I still don't understand why the tach doesn't work - when the only difference is the fact that the 1.6L coil isn't plugged in...

Why would the coil need to be plugged in if the ignitor is still wired up?
Frank_and_Beans is offline   Reply With Quote
Old 03-30-2013, 12:03 PM   #2
Ich verstehe nur Bahnhof
iTrader: (3)
 
psyber_0ptix's Avatar
 
Join Date: Mar 2012
Location: Northern VA
Posts: 3,700
Total Cats: 319
Default

If I recall (and I'm still a noob of all noobs) the 1.6L equipped cars never needed the 1k resistor?

...or am I thinking about the capacitor on the +12 and gnd.
psyber_0ptix is offline   Reply With Quote
Old 03-30-2013, 12:25 PM   #3
Junior Member
iTrader: (1)
 
Join Date: Feb 2009
Location: Kamloops B.C.
Posts: 206
Total Cats: 24
Default

I'm running a home brew LS3 coil setup in a 1.6 car , I just used FM's big spark installation instructions to make up my harnesses and its worked prefect for the get go .The instructions are available on their web site ,product support /ecu and peripherals/big spark. Cheers Fred
fredb is offline   Reply With Quote
Old 03-30-2013, 12:38 PM   #4
Junior Member
Thread Starter
iTrader: (10)
 
Join Date: Jun 2011
Location: Detroit Burbs
Posts: 300
Total Cats: 3
Default

Quote:
Originally Posted by fredb View Post
I'm running a home brew LS3 coil setup in a 1.6 car , I just used FM's big spark installation instructions to make up my harnesses and its worked prefect for the get go .The instructions are available on their web site ,product support /ecu and peripherals/big spark. Cheers Fred
Yeah, I read the instructions here: http://www.flyinmiata.com/support/in...ra%20coils.pdf

It looks like they connect the Black/White wire (ECU pin 2I) to the tach wire (Yel-Blu). But, that doesn't help me, 'cause the Black/White wire isn't connected to anything in my setup. What does the Black/White wire do on the Hydra? Does it go to the tach control pin?
Frank_and_Beans is offline   Reply With Quote
Old 03-30-2013, 12:45 PM   #5
Junior Member
iTrader: (1)
 
Join Date: Feb 2009
Location: Kamloops B.C.
Posts: 206
Total Cats: 24
Default

Quote:
Originally Posted by Frank_and_Beans View Post
Yeah, I read the instructions here: http://www.flyinmiata.com/support/in...ra%20coils.pdf

It looks like they connect the Black/White wire (ECU pin 2I) to the tach wire (Yel-Blu). But, that doesn't help me, 'cause the Black/White wire isn't connected to anything in my setup. What does the Black/White wire do on the Hydra? Does it go to the tach control pin?
I'll have to check the pin out on my set up but you're probably right about the black/white wire ,I check and get back to you. Fred
fredb is offline   Reply With Quote
Old 03-30-2013, 12:46 PM   #6
mkturbo.com
iTrader: (24)
 
shuiend's Avatar
 
Join Date: May 2006
Location: Charleston SC
Posts: 13,775
Total Cats: 1,106
Default

What ECU do you run? On a 1.6 you have to have the ECU outputting the tach signal signal when you run the LS coils.
shuiend is offline   Reply With Quote
Old 03-30-2013, 12:59 PM   #7
Junior Member
iTrader: (1)
 
Join Date: Feb 2009
Location: Kamloops B.C.
Posts: 206
Total Cats: 24
Default

Just checked the pin out, Mazda pin 21 is connection to the rpm signal on the the Hydra . Fred
fredb is offline   Reply With Quote
Old 03-30-2013, 01:42 PM   #8
Tour de Franzia
iTrader: (6)
 
hustler's Avatar
 
Join Date: Jun 2006
Location: Republic of Dallas
Posts: 29,114
Total Cats: 351
Default

I'm not sure if I understand, but I recommend cutting the wire at the cluster, then running that to the computer for the 21st century tach signal.
hustler is offline   Reply With Quote
Old 03-31-2013, 07:32 PM   #9
Junior Member
Thread Starter
iTrader: (10)
 
Join Date: Jun 2011
Location: Detroit Burbs
Posts: 300
Total Cats: 3
Default

I thought that maybe the ignitor needed to see a pullup on the coil outputs. So I took an old 1.6 coil side harness and hooked up some resistors to simulate a pair of coils. Tried 1k, and some 10 ohm resistors. Still no luck.
Frank_and_Beans is offline   Reply With Quote
Old 04-03-2013, 12:29 AM   #10
Junior Member
Thread Starter
iTrader: (10)
 
Join Date: Jun 2011
Location: Detroit Burbs
Posts: 300
Total Cats: 3
Default

Quote:
Originally Posted by hustler View Post
I'm not sure if I understand, but I recommend cutting the wire at the cluster, then running that to the computer for the 21st century tach signal.
Well, I finally gave up on troubleshooting, and took your advice. 21st century tach to the rescue.

On another note - it seems that the stock tach is pretty optimistic. At a commanded 5800 rpm it reads 6000. POS.
Frank_and_Beans is offline   Reply With Quote
 
 
Reply

Related Topics
Thread Thread Starter Forum Replies Last Post
Back to Stock Part Out!! Turbo Parts, MS2 Enhanced 01-05, Suspension, and MOAR! StratoBlue1109 Miata parts for sale/trade 16 10-02-2015 10:39 AM
Bizarre connection issue? nick470 MEGAsquirt 1 09-30-2015 11:32 PM
Odd Steering issue interestedofold Suspension, Brakes, Drivetrain 5 09-29-2015 02:42 PM
Are my coils failing? viriiguy General Miata Chat 5 09-28-2015 08:39 PM


Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off



All times are GMT -4. The time now is 02:10 AM.