home register FAQ memberlist calendar

Go Back   Turbobricks Forums > Mechanical > maintenance & nonperformance

Reply
 
Thread Tools Display Modes
Old 05-03-2017, 12:04 PM   #1
FezMonki
Board Member
 
Join Date: Jun 2015
Location: Italy
Default 90-93 Cruise system on K-jet.

So a friend of mine would like to install cruise control on his K-jet 245, but we have some questions.
Is the signal from the tach the same? Would it/should it work fine?
I wired a year ago a 90-93 system in my (non prewired) 91, and it was pretty straighforward, and from what I remember the only thing the system cares about is the speed signal.

There is also a Dana system available nearby, but from what I read they are pretty crappy (and this one is particularly expensive).
__________________
Looking for wagon third stop and complete cruise system (auto or manual) for 240.
FezMonki is offline   Reply With Quote
Old 05-03-2017, 09:41 PM   #2
Wren
Porkchop Sandwiches
 
Wren's Avatar
 
Join Date: Jun 2006
Location: Athens, GA
Default

The tach signal is exactly the same, but the cruise control uses a signal from the speedometer. No idea if the signal from an old k-jet era speedometer is compatible with one from a newer car. If you had access to both clusters and a oscilloscope you could compare the two signals.

I've wondered about this myself and would also like to know.
Wren is offline   Reply With Quote
Old 05-04-2017, 08:46 AM   #3
FezMonki
Board Member
 
Join Date: Jun 2015
Location: Italy
Default

Quote:
Originally Posted by Wren View Post
The tach signal is exactly the same, but the cruise control uses a signal from the speedometer. No idea if the signal from an old k-jet era speedometer is compatible with one from a newer car. If you had access to both clusters and a oscilloscope you could compare the two signals.

I've wondered about this myself and would also like to know.
Yeah, of course, that was a distraction error, I meant the speedometer signal of course.
FezMonki is offline   Reply With Quote
Old 05-05-2017, 09:13 AM   #4
FezMonki
Board Member
 
Join Date: Jun 2015
Location: Italy
Default

Anyone know about the speedo signal?
FezMonki is offline   Reply With Quote
Old 05-08-2017, 11:16 AM   #5
FezMonki
Board Member
 
Join Date: Jun 2015
Location: Italy
Default

No one?
FezMonki is offline   Reply With Quote
Old 05-18-2017, 11:12 AM   #6
Centsableone
SNAFU - BOHICA
 
Centsableone's Avatar
 
Join Date: Oct 2011
Location: Nunya Bizness, USA
Default Cruise Control

ttt
__________________
1983 245T, 1986 244, 1990 745T, 1990 245,
Currently: 1992 244

Sale and Purchase Feedback

Centsableone is offline   Reply With Quote
Old 05-18-2017, 12:26 PM   #7
ZVOLV
<Master Tech>
 
ZVOLV's Avatar
 
Join Date: Nov 2002
Location: California
Default

Quote:
Originally Posted by FezMonki View Post
Anyone know about the speedo signal?
Uh it's a spinning cable in a kjet 240.... there is no Speedo signal in, or out, that I know of.
__________________
No Start Thread
ZVOLV is offline   Reply With Quote
Old 05-18-2017, 12:32 PM   #8
Khrrck
Professional Amateur
 
Join Date: Mar 2015
Location: Beaverton, OR
Default

If it's mechanical, one could get a pick-up off the cable, in theory, but you would need to do a lot of electrical engineering.

Alternatively, you could swap a electronic speedo setup onto the car, but you would have to replace the diff with one that has a tone ring and sensor.

There might be a GPS speedometer available which will output a pulsed signal like the diff sensor, but if so it'll be expensive and not work in tunnels / canyons.
__________________
'87 240 budget wagon.
Quote:
Originally Posted by Dirty Rick View Post
Navigating the Siskiyous in a 3 wheeled Volvo will not end well.
Khrrck is offline   Reply With Quote
Old 05-18-2017, 12:47 PM   #9
VB242
Dinky nuts, squirrel jam,
 
VB242's Avatar
 
Join Date: Sep 2011
Location: Virginia Beach
Default

Quote:
Originally Posted by ZVOLV View Post
Uh it's a spinning cable in a kjet 240.... there is no Speedo signal in, or out, that I know of.
There's a pickup on the speedometer that gives a pulse signal for the Dana cc. Not all early speedometer have the signal generator. I couldn't get my 1980 parts car cc to work, I'm not sure if the signals are compatible. I did try getting a signal from my later model swapped rear end to the Dana cc but that didn't work either, however I think there was something wrong with the cc box itself.
__________________
snabb tegelston
VB242 is offline   Reply With Quote
Old 05-18-2017, 01:01 PM   #10
hiperfauto
Board Member
 
hiperfauto's Avatar
 
Join Date: Nov 2011
Location: So Cal
Default

It depends on what year K-Jet car this is. -'80 they used a cable driven speedo sensor/regulator. '81-'85 speedos have a provision for a sender to be installed in the back.
hiperfauto is offline   Reply With Quote
Old 05-18-2017, 08:58 PM   #11
bobxyz
Board Member
 
bobxyz's Avatar
 
Join Date: Aug 2014
Location: Boulder, Colorado
Default

Quote:
Originally Posted by FezMonki View Post
Is the signal from the tach [correction: speedo] the same? Would it/should it work fine?
Short answer: no and no.

Long answer: The cable driven speedo's have what looks like an optional module that can be added on the back of the speedo -- 2 spade terminals, 2 screws, and a coil of wire. This module senses a rotating magnet(or magnets?) within the speedo. It's an early version of a VR sensor. The output is low amplitude (few volts at most). The Dana cruise control boxes have a sensitivity adjustment that can work with the speedo magnetic pickup.

The newer speedos use a VR sensor in the rear differential instead of a mechanical cable. The cluster includes some conditioning circuits and a chip that, in addition to driving the electronic speedo needle, drives the VSS output to cruise (and LH2.4 VSS). The signal out of the cluster is open collector -- it will swing 0 to 12volts when connected to a pullup resistor in cruise/LH box.

I think that the output of the rear differential VR sensor is higher amplitude than what comes off an early speedo sensor. If you connect an early speedo output to the circuit board from a late speedo, it might work to generate a late cruise control VSS signal, or it might not if the amplitude isn't big enough.

For LH2.4, you need a VSS signal for good idle control. I don't know if anyone has tried using the early cable speedo sensor, through a late speedo circuit board, to successfully generate a VSS signal for LH2.4. I also don't know if the pulses per MPH would be the same, or close enough.
__________________
'85 245glt aw71 k-jet -> ms
bobxyz is offline   Reply With Quote
Old 05-19-2017, 01:44 PM   #12
ZVOLV
<Master Tech>
 
ZVOLV's Avatar
 
Join Date: Nov 2002
Location: California
Default

One could measure frequency of the output signal and see if it's the same at, say, 60mph as a 2.4 cars speedo output at 60mph. I don't think amplitude really matters as much, but I can't say for sure.
ZVOLV is offline   Reply With Quote
Reply

Thread Tools
Display Modes

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 On

Forum Jump


All times are GMT -4. The time now is 02:23 AM.

Powered by vBulletin® Version 3.8.9
Copyright ©2000 - 2017, vBulletin Solutions, Inc.