The above is an advertisment. If it asks you to download software or create an account, please ignore it.
Site News - 11/25: Special Ad Rate | 11/1: Members: Log In to See Fewer Ads!
[General | Members | C900 | 9000 | NG900 & OG93 | 93 | 95 | NG95 | 99 | Sonett | Vintage Models | Clubs | Other Cars | FAQs | Gifts | Member Photo Galleries | Member Directory | Classifieds | Manuals | *Buddy Registry | *Mileage Registry | Polls | What's New | Raffle | Photo of the Month | Sponsors]

C900 Bulletin Board
1979-1993 & 94 Conv [Subscribe to Daily Digest]
(Search Author's Posts: e.g. Keyword:username)*Members Only

[Main C900 Bulletin Board | BBFAQ | Prev by Date | Next by Date | Post Followup ] Member Login / Signup - Members see fewer ads. - Latest Member Gallery Photos
Let's start again, with new info!
Like This Post: - Subscribe to Daily Digest for this Bulletin Board
Posted by Justin VanAbrahams [Email] (#32) [Profile/Gallery] (more from Justin VanAbrahams) on Thu, 31 Mar 2016 15:56:00 Share Post by Email
In Reply to: Replacing the Speedometer, Justin VanAbrahams [Profile/Gallery] , Mon, 28 Mar 2016 14:32:33
Alert me when someone posts in this thread:
Members do not see ads below this line. - Help Keep This Site Online - Signup

On the way to work today I remembered I have a half-dismantled transmission in the garage, so at lunch I checked it out.

The speedometer drive gear on the 900's inner driver has 16 teeth, the gear on the speedometer pickup itself has 13 teeth. I have a LOI of c900 pickups, they're all 13 teeth. :) A 1.23:1 ratio.

I also found a 9000 speedometer gear which has more teeth (14, IIRC), but I don't have the drive gear so that's useless info. :)

2485 square pulses per kilometer = approx 3965 square pulses per mile

VSS is 4x the square pulse rate, or approx. 15860 sine pulses per mile

Indicated drill speed was 700rpm, divided by the 1.23:1 ratio of the speed drive, that approximately 569rpm at the wheel.

195/60-15 tire is approximately 76.0194" around. 569rpm * 76.0194" tire circumference is 43263" per minute, or approximately .68 miles per minute

.68 miles per minute * 15860 sine pulses at one mile per minute is approximately 10829 sine pulses per minute

10829 sine pulses per minute divided by 60 seconds per minute = 180 sine pulses per second.

I measured 189.4Hz. 189.4Hz is SO CLOSE to the expected 180Hz I think it's fair to say it's close enough. That's 4% error, well within speedometer inaccuracy and possibly explained by a different tire size (195/60-15 c900 vs. 195/65-15 or 205/55-16 9000) or possibly explained by a slight error in the speedo drive ratio, 900 vs. 9000.

I am pretty satisfied this is an accurate test with good math.

The only thing I'd enjoy discovering is what the 9000's speedo gear ratio is, just for grins.


posted by 12.195.130...

Posts in this Thread:
Alert me when someone posts in this thread:
Members do not see ads below this line. - Help Keep This Site Online - Signup
Post a Followup

No Site Registration is Required to Post - Site Membership is optional (Member Features List), but helps to keep the site online
for all Saabers. If the site helps you, please consider helping the site by becoming a member.

Name: Member Login / Signup - Members see fewer ads. - Latest Member Gallery Photos
E-Mail: (Optional)
Re-Enter E-Mail: (Confidential & Secure - Not revealed to other users!)
Note: Please check your spam folder for BB responses.

Subject:

Posting rules are simple - No for sale/wanted ads may be posted here - use the site classifieds.
You may not cross-post your message to multiple BBs.
Not permitted: political/religious topics and being disrespectful (personal attacks, insults, etc...).
 Site Members do not see any red text, inline ad links, bottom of page anchor ads, box ads, or anti-spam check.

Message: (please no for sale/wanted classifieds - post those in the Saabnet.com Classifieds)
Links are now automatically made active, no need for any special code (or use the Option Link field below) - don't put links in () or end with a '.'
To add inline images to your post, use [img]http://www.domain.com/img.jpg[endimg] (or use the Optional Image Link field below).

Links are now automatically made active, no need for any special code (or use the Option Link field below) - don't put links in () or end with a '.'
To add inline images to your post above, use [img]http://www.domain.com/img.jpg[endimg] (or use the Optional Image Link field below).
Optional Link: (e.g. http://www.saabnet.com/)
Link Title: (Optional)
Optional Photo/Image Link: (e.g. http://www.saabnet.com/img.jpg)
Photo/Image to Upload: (Please be patient while file uploads)



StateOfNine.com
SaabClub.com
Jak Stoll Performance
M Car Covers
Ad Available

The content on this site may not be republished without permission. Copyright © 1988-2026 - The Saab Network - saabnet.com.
For usage guidelines, see the Mission & Privacy Notice.
[Contact | Site Map | Saabnet.com on Facebook | Saabnet.com on Twitter | Shop Amazon via TSN | Site Donations]
Random Saabnet.com Member Gallery Photos (Click Image)

This is a moderated bulletin board - Posting is a privilege, not a right. Unsolicited commercial postings are not allowed (no spam). Please, no For Sale or Wanted postings, SERIOUSLY. Classifieds are to be listed in The Saab Network Classifieds pages. This is a problem solving forum for over 250,000 Saab owners, so expect to see problems discussed here even though our cars are generally very reliable. This is not an anything goes type of forum. Saabnet.com has been a moderated forum since 1988. For usage guidelines, see the Saabnet.com Mission and Purpose Page. Please remember that you are not anonymous. Site Contact | Site Donations | Other Sites by SP - Poverty2Prosperity.org | Run Club Menlo Park | ScreenBot
Site Members do not see red text instructions, bottom of the page anchor ads, or box ads.
Click here to see all the Site Membership Benefits!