The Subaru SVX World Network   SVX Network Forums
Live Chat!
SVX or Subaru Links
Old Lockers
Photo Post
How-To Documents
Message Archive
SVX Shop Search
IRC users:

Go Back   The Subaru SVX World Network > SVX Main Forums > Technical Q & A

Reply
 
Thread Tools Display Modes
  #1  
Old 03-10-2005, 08:01 PM
Beav's Avatar
Beav Beav is offline
Not as old as Randy
 
Join Date: Nov 2001
Location: Louisville, KY
Posts: 3,883
Significant Technical Input
Lightbulb Vibration, Revisited

O.K., I'm fresh back from NVH class. Noise, Vibration & Harshness. I made mention in an earlier post about software (w/15 day free trial: http://www.vibratesoftware.com/) that helps pinpoint vibration sources. What is needed to be successful with the software, at the least expense, is a sirometer (look here for a picture of the tool: http://www.vibratesoftware.com/html_...ols_Needed.htm - at the bottom of the page. Available new around $20 or one on ebay currently @ $6. http://cgi.ebay.com/ws/eBayISAPI.dll...sPageName=WDVW)

This is a basic tool that identifies the frequency of a vibration. Using this tool, knowing the engine rpm when the vibration occurs and plugging in some easily obtained measurements will pretty much pinpoint where to look to find the source of a vibration in a vehicle.

The nice part of the software is once you enter the basic info a page will open with these instructions:

~~~~~~~~~~~~~~~~~~~~~

Road Test Procedure


PRINT THIS PAGE AND TAKE IT WITH YOU!
STEP ONE Print a vibration worksheet. See the tutorial for instructions on printing a vibration worksheet. Bring the worksheet, the EVA, and a scan-tool on the road test. Place the EVA’s sensor with the magnetic attachment on the seat frame to begin the road test. It may be necessary to move the sensor to other locations on the vehicle to obtain good readings of frequency and amplitude.
STEP TWO Road test the vehicle at the speed the vibration is most noticeable. You must maintain a steady speed to reduce torque converter slip to a minimum.
STEP THREE Shift the transmission into neutral for several seconds, then back into gear. This procedure may need to be repeated for an accurate diagnosis. If the vibration was not present in neutral, the vehicle has an Engine Speed Related Vibration, Click Here to Diagnose. If the vibration was still present in neutral, the vehicle has a Vehicle Speed Related Vibration.
STEP FOUR Bring the vehicle back up to the speed where the vibration is most noticeable. Obtain and record a vibration frequency (RPM or Hz) reading from the EVA's live data screen in the "Normal Mode" and an engine RPM reading from a tachometer or scan-tool. Mark these readings on the vibration worksheet. For more information on diagnosing these type of vibrations select Vehicle Speed Related Vibrations.
When Road testing a vehicle it is important that the following precautions are taken:

Inspect the vehicle to insure it is safe to drive.

Road test the vehicle on a smooth level road.

A steady throttle must be held in order take accurate readings on vehicles equipped with an automatic transmission. This will keep torque converter clutch slippage to a minimum.

Take several measurements at different vehicle speeds to verify the type of vibration.


You must first determine which category the vibration fits into to accurately diagnose an automobile vibration. A road test is the best way to make this determination.

Most vehicle vibrations can be classified into two categories:

Vehicle Speed Related Vibrations. A vehicle speed related vibration will usually always occur at the same vehicle speed regardless of engine RPM. This type of vibration cannot be detected with the vehicle stopped.
Engine Speed Related Vibrations. An engine speed related vibration will usually always occur at the same engine RPM speed regardless of vehicle speed. This type of vibration can usually be detected with the vehicle stopped, although sometimes it may only show up under a load.

~~~~~~~~~~~~~

Whenever the instructions refer to 'EVA' (an OTC tool, E lectronic V ibration A nalyzer) substitute the sirometer, unless you are lucky enough to have an EVA, reed tachometer or similar device.

Also included in the software is a 'Vibration Diagnosis School' that will teach you the basics of vibration detection and diagnosis. Great stuff. It really isn't that difficult to understand once you read the underlying basics. After spending a few minutes measuring some pulleys and plugging their diameters into the software we were able to take a few quick readings and find a small weight welded into the back of a water pump pulley (how did that get there? ) that was only slightly noticeable at idle speed.

For those that are interested I'd suggest just installing the software and plugging in a few numbers to gain some quick insight of what is capable.
__________________
ASE Certified Master Automotive Technician w/L1.
ASE Certified Master Medium/Heavy Truck Technician.
Certified EVT (Emergency Vehicle Technician)
Reply With Quote
  #2  
Old 03-11-2005, 06:25 AM
RSVX RSVX is offline
Network Design Administrator
 
Join Date: Feb 2002
Location: Boiling Springs, SC
Posts: 4,344
wow... just wow...
__________________
Chris
SVX World Network Administrator
-1993 Subaru SVX LS-L, Barcelona Red, #46, 160,000+ Miles (Sold to SomethingElse)
-2011 Toyota Sienna SE, Black, 30,000+ Miles (Swagger Wagon )
-2002 BMW R 1150R ABS, Black, 26,000+ Miles (Daily Driver )
SVX Owner from February 1997 to March 2008
SVX Online Community Member since February 1998
SVX World Network Member since February 2002, Member #520

Life is a game. Play to win.
The world belongs to those who can laugh at it.
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 Off

Forum Jump


All times are GMT -6. The time now is 01:01 PM.


Powered by vBulletin® Version 3.8.7
Copyright ©2000 - 2024, vBulletin Solutions, Inc.
© 2001-2015 SVX World Network
(208)-906-1122