Can I get a Speedo reading from a Tach?
#1
Senior Member
Thread Starter
Can I get a Speedo reading from a Tach?
I'm just wondering is it possible to somehow get a speedo to read the speed from the tach isntead of the VSS on the tranny. I know it sound complicated but hooking up the speedo to the tranny is not an option so I figure if I can judge speed by RPM myself, shouldn't a gauge be able to do that as well...
#2
Moderator
Join Date: Mar 2001
Location: Doghouse ······································ Car: 1989 Formula 350 Vert Engine: 350 L98 Transmission: 700R4 Axle/Gears: B&W 3.27
Posts: 14,242
Received 170 Likes
on
125 Posts
Car: 87 Formula T-Top, 87 Formula HT
Engine: 5.1L TPI, 5.0L TPI
Transmission: 700R4, M5
Axle/Gears: Sag 3.73, B&W 3.45
I would not think you could convert your tach to work like a speedo. BUT you might be able to have someone drive next to you and figure out how fast you are going in relationship to your RPM's.
John
------------------
G O D BLESS AMERICA
http://www.3rdgenformula.com
87 Formula 5.1 TPI Auto Modified (Yellow/Black)
87 Formula TPI (5 Speed) Yellow/Gray STOCK
14.8sec 1967 Buick Riviera
1990 Buick Riviera (driver)
83 Camaro
83 T/A
John
------------------
G O D BLESS AMERICA
http://www.3rdgenformula.com
87 Formula 5.1 TPI Auto Modified (Yellow/Black)
87 Formula TPI (5 Speed) Yellow/Gray STOCK
14.8sec 1967 Buick Riviera
1990 Buick Riviera (driver)
83 Camaro
83 T/A
#3
Senior Member
iTrader: (4)
Join Date: Mar 2001
Location: Nebraska
Posts: 999
Likes: 0
Received 0 Likes
on
0 Posts
Car: 1985 Trans Am
Engine: 400
Transmission: 700R4
Axle/Gears: 3.70
You might be able to make it work, but say you calibrate it to read 65mph at 2000rpm, then it's going to read 65mph at 2000rpm, regardless of which gear you are in. For this reason, it won't work right, even if you can hook them together somehow.
#5
Member
Join Date: Jul 1999
Location: Malden, Massachusetts, USA
Posts: 479
Likes: 0
Received 1 Like
on
1 Post
Like okfoz said, it's probably best to get on the highway in top gear, have a friend with a known good car and cell phone drive alongside or behind, and log your RPM at various speeds, say, from 40 to 80mph.
Also, remember that leaving transmission inefficiencies aside, double the RPM equals double the speed........ if you know that 2000RPM gets you 60mph, and you're driving along at 3000RPM, you know you're doing about 90.
If you don't have a friend to drive alongside you, get a passenger with a stopwatch, and record the time it takes to travel between highway mile markers; a mile per minute is exactly 60 miles per hour, of course.
Also, remember that leaving transmission inefficiencies aside, double the RPM equals double the speed........ if you know that 2000RPM gets you 60mph, and you're driving along at 3000RPM, you know you're doing about 90.
If you don't have a friend to drive alongside you, get a passenger with a stopwatch, and record the time it takes to travel between highway mile markers; a mile per minute is exactly 60 miles per hour, of course.
Thread
Thread Starter
Forum
Replies
Last Post
Hotrodboba400
Firebirds for Sale
3
12-10-2019 07:07 PM
IROCZDAVE (88-L98)
Engine/Drivetrain/Suspension Parts for Sale
1
11-19-2015 07:03 AM