Called the shop where my car is, and they said they were useing a scope on my distributor? What is a scope and what does it do. Sounds like a tool that would come in handy..-TK

 

Off the topic, is that original paint and if so, does it really look that good?

I like that car alot, thought about getting one but i like my ragtop just a bit more. ;)

 

A scope is a piece of test equipment where they can look at the waveform your distributor is putting out... Kind of like that machine you always see in the movies that shows a patient's heartbeat.
That's my assumption, anyways... Am I correct guys?
-Jason

 

Yep, original paint...
does it look that good?-Looks like it does in the picture. :yesnod:
But right now it looks like visa will love me again :sad: -TK

 

A 'scope' is a short diminuitive for Oscilloscope...which is an electronic instrument much similar to a small screen TV set, that will display the exact voltages of a waveform...such as when in movies, quite frequently they will display a 'sine' wave or 'square' wave or some such garbage having NOTING to do with the story line....
in a medical type TV show it's the display on which the heart rate or other vital signs are/is displayed.....

as an electronic diagnostic tool it's invaluable for tracing computer/digital/analogue/switched pulses-waveforms, ...and get a sense of the timing/frequency of events....
good 'scopes today can read into Giga hertz....IE into Cell phone bands directly without any processing.....mean feat there....
yesterday's good lick was 50 mhz....and back in the dark ages, before cave men a 'scope could be a hot lick at 5-15 mhz input display power....

to the totally tech challenged, it's that 'thing' with the wiggley lines on it....;-))) :D :D :eek: :eek: :cool: :jester :jester

Nerd

 

Ok...so the scope will tell them if there is a problem with my distributor/coil....right?-TK

 

TJK ,,,, a scope is the ultimate diagnostic tool for cars such as the vette. It measures two things ,,,, time and voltage and yes it can check all aspects of your distributor ,both mechanical and electrical . I use a sun 2001 diagnostic unit that has a very large scope that will read 50kvs. The neat thing is the speed of your ability to diagnose problems ,ie: I can check relative compression without pulling plugs. Great play toy to have in your home shop!

Geo :rolleyes:

 

Well, there is the funny thing, I have found histerically, that using a common electronics diagnostic scope on a car to be nearly meaningless....and in fact the displays are similar , exact....just a manner of the 'rep rate' that is how many cylinders are displayed in a row....a dedicated automotive 'scope will have a certain setup to display only 4-6-8-10-12 cylinders.... and a 'parade' of just those pulses in sequence...triggered (started) off #1 cyl and following through..
now my comment on the uselfullness of the display....I personally never saw anything about the display what indicated a definate malfunction in any distributor setup....now for sure a total failure in say a plug or shorted wire could be seen...but NOT clearly and not obvious....since an arc over is an arc over, and damn if I can see the differance....
now I have read the books too, but that's MY experiences....

GENE

 

An arc over is normally seen as a shorter voltage line...

A lot does show on a scope. It does take training and using one to get to know what to look for though. A person can not just pick up a book and use one to full effect, you have to learn the cause and effect of problems so when you see something you know what is wrong. Nothing pops up and tells you anything.

A good scope will let you do more than just electrical problems. It should allow you to kill any cylinder and see what effect it has. This can show what percentage each cylinder is giving you at idle by comparing idle speed drop for example. If you have a dyno, you can do the same at speed, under load.

Scopes are not new, they have been around since WWII in aircraft use. My mechanic puts every car he tunes on a scope both before and after he tunes it. It only takes him a couple minutes and lets him see things he might normally miss. He's an older guy (about 68 or so), is fair and does good work on whatever anyone brings him, from an old Ford 8N tractor to a late model Mercedes.

 

There are three modes that the ignition can be viewed ,raster,display,and superimposed . A good example of a classic mechanical distributor malfunction would be worn shaft bushings,or perhaps a worn cam lobe in the old points style distributor . This problem is readily apparent in a raster pattern where each cylinders waveform is shown in a horizontal format. The individual cylinders are shown in firing order in a vertical stacked display . All time functions are shown horizontally and allow easy diagnosis . It is very interesting to watch the hei system adjust its own dwell to adjust to the demands of the engine .

A foul plug can be easily found by examining the firing voltages for each cylinder . These are best seen in the display or parade pattern. A good scope such as a 2001 also will print this info for easy diagnosis on the attached crt . The firing voltages show the voltage required to start a spark across the rotor and plug air gaps. They tend to run in the 7/12kv range!

The firing line is the section to watch in order to find fouled plugs and is indicated by a pronounced downward tilt . The firing line averages app.1/4 the firing voltage and shows the voltage required to maintain a spark across the rotor and plug gaps .

Relative compression readings are taken by measuring the current loops
required to compress the mixture in each cylinder while cranking the engine
this info is also supplied to the operator via the crt .

If anyone has any questions just drop me an e/mail,, I enjoy yacking with tech freaks or nerds !

Geo
:rolleyes: :rolleyes: :rolleyes: :rolleyes: :rolleyes: :rolleyes: :rolleyes:

 

This could be one of them old guy things ,,,,

Geo :rolleyes: <------------------ is really old


[Modified by ram82fire, 7:23 PM 4/16/2002]