Login   Register

It is currently Tue Oct 23, 2018 8:05 pm




Post new topic Reply to topic  [ 13 posts ] 
Author Message
 Post subject: New Tachometer in an old car
PostPosted: Wed Apr 14, 2010 2:28 am 
Offline
Site Member
User avatar

Joined: Tue Mar 02, 2010 6:21 pm
Posts: 260
Location: SE Portland
So I know my stock tach senses current or voltage waves or something of that sort off of the coil. When shopping around for a new aftermarket one, they are all marketed with newer cars in mind that get their signal off of the ECU. Instructions are typically "connect signal wire from tach to wire/pin #blah-blah on your ECU wiring harness."

My question is, is the signal produced by the ECU on newer cars the same as what's coming off of the coil on older cars? In other words, can I buy one of these newer tachometers, wire it to my coil in place of the old one, and have it work?

_________________
Sean - 1970 1800E

Image
genacys wrote:
I made it through college, that means I should be totally equipped with the mental facilities necessary to deal with this.


Top
 Profile  
 
 Post subject: Re: New Tachometer in an old car
PostPosted: Wed Apr 14, 2010 1:08 pm 
Offline
Site Member
User avatar

Joined: Thu Feb 19, 2009 10:19 pm
Posts: 476
Location: Lake Oswego, OR
I can't necessarily answer the ECU question, but I can say that modern 12V tachs that get their signal from the coil are still common and easily obtainable.

_________________
Image


Top
 Profile  
 
 Post subject: Re: New Tachometer in an old car
PostPosted: Wed Apr 28, 2010 1:15 pm 
Offline
Site Member
User avatar

Joined: Tue Mar 02, 2010 6:21 pm
Posts: 260
Location: SE Portland
For anyone who was interested, I picked up an AutoMeter tach (#2301) and it appears to be a voltage-sensing unit as opposed to the current-sensing Smiths tach that came stock in the car. It has one constant 12v hot lead, one ground lead, and one signal wire that goes to the negative side of the coil. And because it's not current-sensing (doesn't add any additional load to the current that's already going through the stock tach), they both function together. Woohoo!

Also, according to the very rudimentary instructions, it looks like the signal terminal on the ECU of a newer car is the same voltage signal as from the negative side of the coil.

_________________
Sean - 1970 1800E

Image
genacys wrote:
I made it through college, that means I should be totally equipped with the mental facilities necessary to deal with this.


Top
 Profile  
 
 Post subject: Re: New Tachometer in an old car
PostPosted: Thu Apr 29, 2010 12:56 pm 
Offline
Site Member
User avatar

Joined: Mon Mar 07, 2005 4:57 pm
Posts: 7289
Location: SW Portland, OR
w00h00! Nice work. So, your original died then?

_________________
Kyle - '91 244? - '68 142(SOLD!?! :()? - '06 Ninja 250R? - My Galleries?
Image


Top
 Profile  
 
 Post subject: Re: New Tachometer in an old car
PostPosted: Thu Apr 29, 2010 2:03 pm 
Offline
Site Member
User avatar

Joined: Tue Mar 02, 2010 6:21 pm
Posts: 260
Location: SE Portland
Nah the original still works great, but when I replaced the giant hoola-hoop of a steering wheel with a smaller aftermarket one, it was the perfect diameter to obstruct my view of the stock tach. I've been driving around with it like that for a year and a half and finally got fed up of having to either turn the music down or move my left hand and peek down underneath the steering wheel to find out what me revs were, haha.

_________________
Sean - 1970 1800E

Image
genacys wrote:
I made it through college, that means I should be totally equipped with the mental facilities necessary to deal with this.


Top
 Profile  
 
 Post subject: Re: New Tachometer in an old car
PostPosted: Thu Apr 29, 2010 2:38 pm 
Offline
Site Member
User avatar

Joined: Thu Feb 19, 2009 10:19 pm
Posts: 476
Location: Lake Oswego, OR
I can one up that. On my 145, the stock steering wheel horn bar was just at the right height to completely block the horizontal row of the fuel gauge, temp gauge, and all the warning lights. I had to peer up and over or down and under to get a shot of anything when going in a straight line. Getting some nice GT gauges fixed that!

_________________
Image


Top
 Profile  
 
 Post subject: Re: New Tachometer in an old car
PostPosted: Thu Apr 29, 2010 3:37 pm 
Offline
Site Member

Joined: Mon Sep 24, 2007 8:12 pm
Posts: 831
Location: Oregon City
drj434343 wrote:
I can one up that. On my 145, the stock steering wheel horn bar was just at the right height to completely block the horizontal row of the fuel gauge, temp gauge, and all the warning lights. I had to peer up and over or down and under to get a shot of anything when going in a straight line. Getting some nice GT gauges fixed that!


At least you didn't bounce it off a curb to tweak the alignment enough that the steering wheel was a bubble off center.

On purpose.

_________________
1987 745T, 1988 744NA, 1989 744, 1985 764 V8 project, 2000 Chevy PU, 1992 VW Cabriolet, 1985 Porsche 944, 1970 Jeep Commando, 1969 VW Bug, 1967 122, 1965 220 wagon, 1964 VW dunebugy, 1963 Chevy PU, 1960 Corvette, 1957 GMC 2 1/5 Ton, 1937 Chevy PU


Top
 Profile  
 
 Post subject: Re: New Tachometer in an old car
PostPosted: Thu Apr 29, 2010 4:06 pm 
Offline
Site Member
User avatar

Joined: Tue Mar 02, 2010 6:21 pm
Posts: 260
Location: SE Portland
Omg don't tell me someone actually did that... On purpose..

_________________
Sean - 1970 1800E

Image
genacys wrote:
I made it through college, that means I should be totally equipped with the mental facilities necessary to deal with this.


Top
 Profile  
 
 Post subject: Re: New Tachometer in an old car
PostPosted: Thu Apr 29, 2010 7:44 pm 
Offline
Site Member

Joined: Mon Sep 24, 2007 8:12 pm
Posts: 831
Location: Oregon City
I was tempted but settled by taking off the steering wheel and putting it back on slightly crooked. Crude but it worked.

_________________
1987 745T, 1988 744NA, 1989 744, 1985 764 V8 project, 2000 Chevy PU, 1992 VW Cabriolet, 1985 Porsche 944, 1970 Jeep Commando, 1969 VW Bug, 1967 122, 1965 220 wagon, 1964 VW dunebugy, 1963 Chevy PU, 1960 Corvette, 1957 GMC 2 1/5 Ton, 1937 Chevy PU


Top
 Profile  
 
 Post subject: Re: New Tachometer in an old car
PostPosted: Thu Apr 29, 2010 8:29 pm 
Offline
Site Member
User avatar

Joined: Thu Feb 19, 2009 10:19 pm
Posts: 476
Location: Lake Oswego, OR
My solution was just never to drive in a straight line.

_________________
Image


Top
 Profile  
 
 Post subject: Re: New Tachometer in an old car
PostPosted: Thu Apr 29, 2010 10:40 pm 
Offline
Site Member
User avatar

Joined: Mon Mar 07, 2005 4:57 pm
Posts: 7289
Location: SW Portland, OR
:lol: *pictures someone swerving back and forth down a straight road*

_________________
Kyle - '91 244? - '68 142(SOLD!?! :()? - '06 Ninja 250R? - My Galleries?
Image


Top
 Profile  
 
 Post subject: Re: New Tachometer in an old car
PostPosted: Fri Apr 30, 2010 10:48 am 
Offline
Site Member
User avatar

Joined: Thu Feb 19, 2009 10:19 pm
Posts: 476
Location: Lake Oswego, OR
It's pretty easy to do anyway, with the monster ruts along the 84.

_________________
Image


Top
 Profile  
 
 Post subject: Re: New Tachometer in an old car
PostPosted: Fri Apr 30, 2010 11:37 am 
Offline
Site Member

Joined: Mon Sep 24, 2007 8:12 pm
Posts: 831
Location: Oregon City
KLR142 wrote:
:lol: *pictures someone swerving back and forth down a straight road*

That's the only way to stay awake heading through some parts of Eastern Oregon and going down the Valley in CA on I5. That is if your car won't go fast enough to make your eyes water.

_________________
1987 745T, 1988 744NA, 1989 744, 1985 764 V8 project, 2000 Chevy PU, 1992 VW Cabriolet, 1985 Porsche 944, 1970 Jeep Commando, 1969 VW Bug, 1967 122, 1965 220 wagon, 1964 VW dunebugy, 1963 Chevy PU, 1960 Corvette, 1957 GMC 2 1/5 Ton, 1937 Chevy PU


Top
 Profile  
 
Display posts from previous:  Sort by  
Post new topic Reply to topic  [ 13 posts ] 

It is currently Tue Oct 23, 2018 8:05 pm


Who is online

Users browsing this forum: No registered users and 1 guest


You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot post attachments in this forum

Search for:
Jump to:  
cron



Powered by phpBB © 2000, 2002, 2005, 2007 phpBB Group  
Design By Poker Bandits