Tachometer Reads Low ? - BMW Luxury Touring Community
 
LinkBack Thread Tools Display Modes
post #1 of 26 Old Jul 25th, 2014, 5:59 pm Thread Starter
Enjoy The Ride
 
saddleman's Avatar
 
Join Date: Sep 2008
Location: Huntersville, NC, USA
Posts: 3,893
Tachometer Reads Low ?

It appears the tach. on my 2000 reads low. According to a gear ratio speed calculator chart with these spec's, FD gear 2.75, Tire dia. 25.625, 5th gear 1.511 & 3500 rpm my speed should be 64 mph. On my GPS I'm at 71 mph at 3500. At 71 mph the tach. should be at 3850 rpm. My rev limiter doesn't always work either. I've noticed a few times the tach past the red zone in third gear without the limiter kicking in. Other times the limiter works just fine.

On my 2004 with the 2.62 FD gear my speed should be 67 mph @ 3500 rpm & the GPS has it at 66 mph. That is only 50 rpm off and I would consider that normal.

I don't know of any way to correct the tach on my 2000.

Dave Selvig
2004 Black LT
2000 Canon Red LT



To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.
saddleman is offline  
Sponsored Links
Advertisement
 
post #2 of 26 Old Jul 25th, 2014, 9:53 pm
Wrencher Extraordinaire
 
jzeiler's Avatar
 
Join Date: May 2004
Location: Hazel Green, AL, USA
Posts: 13,300
Re: Tachometer Reads Low ?

I don't know what you could do. I do know that one half of the coil driver from the ECU is fed to the cluster for the tach. But not sure if the ECU uses that signal or the hall effect sensor to determine RPM for the limiter.

John
2009 K1300GT Red Rocket
2009 R1200GS (Gone)
2005 K1200LT Ocean Blue Blue Wizard 110 K and counting...
2006 Bushtec Turbo+2 Spell
2004 330 Ci Convertable
K4AN

Have ridden a Motorcycle in all 48
But lack DE, MA, RI and CT with the 2005 LT

To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.
jzeiler is offline  
post #3 of 26 Old Jul 25th, 2014, 10:40 pm
Lifetime Supporter
 
deanwoolsey's Avatar
 
Join Date: Aug 2008
Location: Topeka, KS, USA
Posts: 3,105
Re: Tachometer Reads Low ?

The speedometer on my 2000 has been corrected and is consistent with my GPS. At 80 I show about 4000 RPM, 70 is 3500, and so on. I've always been happy with that since it's an easy way to see when the clutch might be slipping, since the speed in fifth gear should always be twice the amount of the first two numbers of the RPM.


To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.
deanwoolsey is offline  
 
post #4 of 26 Old Jul 25th, 2014, 10:50 pm
Senior Member
 
oldmopars's Avatar
 
Join Date: Apr 2014
Posts: 242
Garage
Re: Tachometer Reads Low ?

I also have a 2000, how did you correct the speedo? Mine is off by 10%.
oldmopars is offline  
post #5 of 26 Old Jul 25th, 2014, 11:06 pm
Lifetime Supporter
 
deanwoolsey's Avatar
 
Join Date: Aug 2008
Location: Topeka, KS, USA
Posts: 3,105
Re: Tachometer Reads Low ?

Quote:
Originally Posted by oldmopars View Post
I also have a 2000, how did you correct the speedo? Mine is off by 10%.

http://www.bmwlt.com/forums/faq.php?...0lt_faq_speedo


To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.
deanwoolsey is offline  
post #6 of 26 Old Jul 26th, 2014, 12:53 am
Senior Member
 
casualemt's Avatar
 
Join Date: Jun 2009
Location: Oak Harbor, WA, USA
Posts: 676
Re: Tachometer Reads Low ?

I myself, prefer the incorrect speedometer reading, most times it makes me think I am going faster than I really am, and when I pass a state patrol and freak out a little, I do the mental calculation to determine what my speed really is, and figure out why I didn't get a speeding ticket....not going as fast as I thought. Kind of like setting your clock fast, thinking you're late, and finding out you were on time for your appointment afterall! I guess you could say I use it as a crutch...Ahhh, the things these Germans think up to help us speed thirsty american motorcycle fanatics!!
As far as the Tach goes, as many manual transmission cars as I have owned without a tach, I am more intune with the sound of the engine as it revs anyway, although I DO respect the red line. Yea, its late, and I'm rambling..

RICH CANNON
2000 K1200LT "a great ride"
2002 GL1800 powerful, but boring..(gone)
1979 XS1100 (gone)
1986 VT500 Ascot (gone)
1972 Honda 500-4 (gone)
1961 Lambretta (way gone)
1962 Allstate Compact (gone but not forgotten)
To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.
casualemt is offline  
post #7 of 26 Old Jul 26th, 2014, 8:53 am Thread Starter
Enjoy The Ride
 
saddleman's Avatar
 
Join Date: Sep 2008
Location: Huntersville, NC, USA
Posts: 3,893
Re: Tachometer Reads Low ?

This has nothing to do with the incorrect reading speedometer.

Dave Selvig
2004 Black LT
2000 Canon Red LT



To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.
saddleman is offline  
post #8 of 26 Old Jul 26th, 2014, 9:50 pm
Senior Member
 
BecketMa's Avatar
 
Join Date: Jul 2002
Location: Tucson, AZ, USA
Posts: 3,522
Re: Tachometer Reads Low ?

Did u do the speedo mod? If yes with the SMD pcbs its easy to melt the solder on near by devices or just get a strand of multi strand wire out of place. with that descrepency I assume that you would have noticed it early on.

Only other oddity was where the speedo cable was straped to the rear "swing arm", many speedos started bouncing as the cable cut into the line.

bob

"He was a foul caricature of himself, a man with no soul, no inner convictions, with the integrity of a hyena, and the style of a poison toad." H. S. Thompson
BecketMa is offline  
post #9 of 26 Old Jul 26th, 2014, 10:39 pm Thread Starter
Enjoy The Ride
 
saddleman's Avatar
 
Join Date: Sep 2008
Location: Huntersville, NC, USA
Posts: 3,893
Re: Tachometer Reads Low ?

This is a tachometer issue & not a speedometer issue what part of that don't you understand.

Dave Selvig
2004 Black LT
2000 Canon Red LT



To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.
saddleman is offline  
post #10 of 26 Old Jul 26th, 2014, 10:41 pm Thread Starter
Enjoy The Ride
 
saddleman's Avatar
 
Join Date: Sep 2008
Location: Huntersville, NC, USA
Posts: 3,893
Re: Tachometer Reads Low ?

If you want to post about speedometers start your own damn thread.

Dave Selvig
2004 Black LT
2000 Canon Red LT



To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.
saddleman is offline  
post #11 of 26 Old Jul 27th, 2014, 8:07 am
Lifetime Supporter
 
Voyager's Avatar
 
Join Date: Jun 2007
Location: Lawrenceville, PA, USA
Posts: 7,172
Re: Tachometer Reads Low ?

Quote:
Originally Posted by saddleman View Post
It appears the tach. on my 2000 reads low. According to a gear ratio speed calculator chart with these spec's, FD gear 2.75, Tire dia. 25.625, 5th gear 1.511 & 3500 rpm my speed should be 64 mph. On my GPS I'm at 71 mph at 3500. At 71 mph the tach. should be at 3850 rpm. My rev limiter doesn't always work either. I've noticed a few times the tach past the red zone in third gear without the limiter kicking in. Other times the limiter works just fine.

On my 2004 with the 2.62 FD gear my speed should be 67 mph @ 3500 rpm & the GPS has it at 66 mph. That is only 50 rpm off and I would consider that normal.

I don't know of any way to correct the tach on my 2000.
Hmmm. The calculated value should be pretty close, but do you have an independent way to directly measure RPM such as a tach that will use a spark plug pulse?

2017 KLR650 "Mule"
2007 K1200LT "Starship Enterprise", VOICE II, Navigator V, Motorrad Communicator
1987 Kawasaki Voyager XII
1976 Kawasaki KH400
1973 Kawasaki 100 G5
1970 Rockford Chibi (the orange one)

To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.
Voyager is online now  
post #12 of 26 Old Jul 27th, 2014, 8:44 am
Senior Member
 
gunny's Avatar
 
Join Date: Aug 2003
Location: Kings Mountain, NC, USA
Posts: 3,089
Re: Tachometer Reads Low ?

Dave, if you have an electrical schematic, I'd like to take a close look at it.

See where that signal is generated and what else it may be used for/by. If just the tachometer, be pretty simple but if used for other things and I suspect it is, it might be move involved.

If it were the pick up, would think it would either work of not work. A hall effect type pick up is either good or its not, very rare for them to work intermittently. Most often the problem with them is they are not adjusted correctly. If too close to the trigger, will give a higher voltage than the device it is signalling will be expecting and may cause problems, especially at higher readings (rpm). If too far away, lower voltage but would expect erractic operation at lower rpm.

Then there is the issue of how the signal from the trigger processed. Look at the signal from the trigger, it will be AC. I'd expect to see around 1.5 or so at cranking speed and 20 or so with the engine at a high rpm and steady. The frequency wil change with engine speed.

I have a Fluke 123 Scope meter (with the manual) I'd be happy to let you use.

B D R
gunny is offline  
post #13 of 26 Old Jul 27th, 2014, 2:54 pm
Senior Member
 
BecketMa's Avatar
 
Join Date: Jul 2002
Location: Tucson, AZ, USA
Posts: 3,522
Re: Tachometer Reads Low ?

Has it occurred to you that your prose might not be as clear as it could be?

I won't be reading any reply you post to my question since you seem to be very angry. Associating with angry people is something I avoid

"He was a foul caricature of himself, a man with no soul, no inner convictions, with the integrity of a hyena, and the style of a poison toad." H. S. Thompson
BecketMa is offline  
post #14 of 26 Old Jul 27th, 2014, 5:36 pm
Lifetime Supporter
 
Voyager's Avatar
 
Join Date: Jun 2007
Location: Lawrenceville, PA, USA
Posts: 7,172
Re: Tachometer Reads Low ?

Quote:
Originally Posted by BecketMa View Post
Has it occurred to you that your prose might not be as clear as it could be?

I won't be reading any reply you post to my question since you seem to be very angry. Associating with angry people is something I avoid
I am curious as to what part of Saddlemans very first sentence was unclear? He wrote, "It appears the tach. on my 2000 reads low." I don't see how he could have been more clear than that. Well, I guess he could have written out tachometer...

2017 KLR650 "Mule"
2007 K1200LT "Starship Enterprise", VOICE II, Navigator V, Motorrad Communicator
1987 Kawasaki Voyager XII
1976 Kawasaki KH400
1973 Kawasaki 100 G5
1970 Rockford Chibi (the orange one)

To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.
Voyager is online now  
post #15 of 26 Old Jul 28th, 2014, 2:11 pm
Senior Member
 
Join Date: May 2014
Posts: 230
Re: Tachometer Reads Low ?

The original post says "tach".
Any Questions?
Technical FYI... A tachometer is NOT a speedometer.




later..Randy
2006lt is offline  
post #16 of 26 Old Jul 28th, 2014, 5:11 pm
Lifetime Supporter
 
deanwoolsey's Avatar
 
Join Date: Aug 2008
Location: Topeka, KS, USA
Posts: 3,105
Re: Tachometer Reads Low ?

My point was the correlation between tach reading and speedometer with a corrected speedometer. Your mileage may vary. Yea, it got off topic. Dave did you double check your math? If you're certain of the figures, looks like BMW built some error into the tachs, only on the wrong end.


To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.
deanwoolsey is offline  
post #17 of 26 Old Jul 28th, 2014, 5:52 pm Thread Starter
Enjoy The Ride
 
saddleman's Avatar
 
Join Date: Sep 2008
Location: Huntersville, NC, USA
Posts: 3,893
Re: Tachometer Reads Low ?

I'm going to put a 2.75 gear in my 2004 LT and see what the RPM reads.

Dave Selvig
2004 Black LT
2000 Canon Red LT



To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.
saddleman is offline  
post #18 of 26 Old Jul 28th, 2014, 6:11 pm Thread Starter
Enjoy The Ride
 
saddleman's Avatar
 
Join Date: Sep 2008
Location: Huntersville, NC, USA
Posts: 3,893
Re: Tachometer Reads Low ?

Quote:
Originally Posted by deanwoolsey View Post
My point was the correlation between tach reading and speedometer with a corrected speedometer. Your mileage may vary. Yea, it got off topic. Dave did you double check your math? If you're certain of the figures, looks like BMW built some error into the tachs, only on the wrong end.
No problem Dean. I'm not using math but a gear ratio & speed chart. I've been using them for over 30 years on race cars. You can google it and add the numbers. The only variable is the tire diameter. Some tires grow more diameter at speed than others. We use to do it with a slide scale but the internet has made it much easier now.

Dave Selvig
2004 Black LT
2000 Canon Red LT



To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.
saddleman is offline  
post #19 of 26 Old Jul 28th, 2014, 6:31 pm
Senior Member
 
lkchris's Avatar
 
Join Date: Feb 2012
Location: Albuquerque, NM, USA
Posts: 1,012
Re: Tachometer Reads Low ?

Of course you know there's no mechanical connection between your driveline and the tachometer--it's electronic. So only problem is likely internal friction in the tach's gears, needle shaft, etc., as electronic failure is likely all or nothing. How does it perform at idle? Does it appear to respond correctly when blipping throttle in neutral? Can you hook up another tach (e.g. on a timing light) to compare the two? I'd call one of the usual instrument repair places, North Hollywood Speedometer, etc., and discuss.

Kent Christensen
Albuquerque
'12 R1200RT, '02 R1100S, '84 R80G/S
lkchris is offline  
post #20 of 26 Old Jul 28th, 2014, 7:37 pm
Lifetime Supporter
 
deanwoolsey's Avatar
 
Join Date: Aug 2008
Location: Topeka, KS, USA
Posts: 3,105
Re: Tachometer Reads Low ?

Quote:
Originally Posted by saddleman View Post
No problem Dean. I'm not using math but a gear ratio & speed chart. I've been using them for over 30 years on race cars. You can google it and add the numbers. The only variable is the tire diameter. Some tires grow more diameter at speed than others. We use to do it with a slide scale but the internet has made it much easier now.
No problem. Just letting you know that mine seems to be the same as yours. I do have a portable digital tach. Might have to hook it up and check it out later this week to see what it says.


To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.
deanwoolsey is offline  
post #21 of 26 Old Jul 28th, 2014, 10:32 pm
Lifetime Supporter
 
Join Date: May 2003
Location: Phoenix, AZ, USA
Posts: 1,305
Re: Tachometer Reads Low ?

Quote:
Originally Posted by saddleman View Post
No problem Dean. I'm not using math but a gear ratio & speed chart. I've been using them for over 30 years on race cars. You can google it and add the numbers. The only variable is the tire diameter. Some tires grow more diameter at speed than others. We use to do it with a slide scale but the internet has made it much easier now.
Maybe a check of your actual rear wheel rolling diameter would provide the answer.

Motor On ,/'


To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.


To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.
jkersh1 is offline  
post #22 of 26 Old Jul 29th, 2014, 4:31 am Thread Starter
Enjoy The Ride
 
saddleman's Avatar
 
Join Date: Sep 2008
Location: Huntersville, NC, USA
Posts: 3,893
Re: Tachometer Reads Low ?

Quote:
Originally Posted by jkersh1 View Post
Maybe a check of your actual rear wheel rolling diameter would provide the answer.
I have done that.

Dave Selvig
2004 Black LT
2000 Canon Red LT



To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.
saddleman is offline  
post #23 of 26 Old Jul 29th, 2014, 8:56 pm Thread Starter
Enjoy The Ride
 
saddleman's Avatar
 
Join Date: Sep 2008
Location: Huntersville, NC, USA
Posts: 3,893
Re: Tachometer Reads Low ?

I just finished assembling a 2.75 gear ratio FD for my 2004 LT. I'll install it Friday after work & go for a ride.

Dave Selvig
2004 Black LT
2000 Canon Red LT



To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.
saddleman is offline  
post #24 of 26 Old Aug 2nd, 2014, 8:07 am Thread Starter
Enjoy The Ride
 
saddleman's Avatar
 
Join Date: Sep 2008
Location: Huntersville, NC, USA
Posts: 3,893
Re: Tachometer Reads Low ?

With the 2.75 FD gear ratio in my 2004 LT I show a speed of 62 mph at 3500 rpm & 72 mph at 4000 rpm. That is close to what I expected with the gear change from a 2.62 to a 2.75 ratio. The tachometer is off enough on my 2000 LT that I now will make sure I don't rev it over 7500 before I shift to the next gear.

Dave Selvig
2004 Black LT
2000 Canon Red LT



To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.
saddleman is offline  
post #25 of 26 Old Aug 2nd, 2014, 9:08 am
Lifetime Supporter
 
Voyager's Avatar
 
Join Date: Jun 2007
Location: Lawrenceville, PA, USA
Posts: 7,172
Re: Tachometer Reads Low ?

Quote:
Originally Posted by saddleman View Post
With the 2.75 FD gear ratio in my 2004 LT I show a speed of 62 mph at 3500 rpm & 72 mph at 4000 rpm. That is close to what I expected with the gear change from a 2.62 to a 2.75 ratio. The tachometer is off enough on my 2000 LT that I now will make sure I don't rev it over 7500 before I shift to the next gear.
Are these indicated speeds (speedometer) or actual (GPS)?

My 2007 with stock ratio (2.62, right?) indicates almost exactly 20 MPH/1,000 RPM in 5th gear. So 3,000 = 60 and 4,000 = 80. However, if I use the more accurate GPS speed, 3,000 = 56/57 and 4,000 = 75/76.

If mine had the lower 2.75 ratio, my actual speeds would be pretty close to yours for your 2004.

2017 KLR650 "Mule"
2007 K1200LT "Starship Enterprise", VOICE II, Navigator V, Motorrad Communicator
1987 Kawasaki Voyager XII
1976 Kawasaki KH400
1973 Kawasaki 100 G5
1970 Rockford Chibi (the orange one)

To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.
Voyager is online now  
post #26 of 26 Old Aug 2nd, 2014, 11:13 am Thread Starter
Enjoy The Ride
 
saddleman's Avatar
 
Join Date: Sep 2008
Location: Huntersville, NC, USA
Posts: 3,893
Re: Tachometer Reads Low ?

Per post #1 all speeds are with the GPS I never use the bike speedometer.

Dave Selvig
2004 Black LT
2000 Canon Red LT



To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.
saddleman is offline  
Reply

Quick Reply
Message:
Options

Register Now



In order to be able to post messages on the BMW Luxury Touring Community forums, you must first register.
Please enter your desired user name, your email address and other required details in the form below.

User Name:
Password
Please enter a password for your user account. Note that passwords are case-sensitive.

Password:


Confirm Password:
Email Address
Please enter a valid email address for yourself.

Email Address:
OR

Log-in











Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)
 
Thread Tools
Show Printable Version Show Printable Version
Email this Page Email this Page
Display Modes
Linear Mode Linear Mode



Similar Threads
Thread Thread Starter Forum Replies Last Post
K1200LT TRIP COMPUTER READS "PPP"? Swampdonkey K1200LT 1 Oct 9th, 2012 6:49 am
Tachometer won't tach davek100rt K1200LT 5 Jul 4th, 2011 8:10 pm
Tachometer Gremlins UltraLT K1200LT 9 Mar 12th, 2010 4:59 pm
Is this really what he reads? dwsdad Chit Chat 10 Oct 14th, 2008 10:57 pm
A woman who reads bushj1 Humor 0 Mar 22nd, 2006 11:27 am

Posting Rules  
You may post new threads
You may 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 On
Pingbacks are On
Refbacks are On

 
For the best viewing experience please update your browser to Google Chrome