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using a "scope"

General engine tech -- Drag Racing to Circle Track

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fastfan

using a "scope"

Post by fastfan »

Do any of you use a "Scope" to evaluate how your race motor is functioning? One person who owns one says his hand held unit is not consistant. Any other comments would be helpful. Thanks.
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steveD
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Post by steveD »

Are you referring to an oscilloscope?
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Post by tmoble »

18 or so years I used to use a Snap-On Counselor on the dyno some. it was not long after they came out. they were about the first digital scopes I saw. Mine was portable, but not handheld. Used it to run down some nasty plug wire issues. At one point I could correlate firing voltage and spark duration with rich/lean cylinders, but it was nothing you couldn't find with EGTs. That scope, and it was an early model, didn't like MSDs at low RPM.
fastfan

Post by fastfan »

Yes, I think the "scope" I am refering to is called an oscilloscope. When a motor seems to be down on power, the first thing I do is run a compression test, and put in new spark plugs. Will an oscilloscope tell me if my plugs are firing well? Thanks again for the advice.
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Re: using a "scope"

Post by jake197000 »

i préfère an anolog scope,its a direct patterns not a manufactured one.been usine them since the 70's.i do like a digital for checking séniors and such.i do a lot of classic car engines and transmissions you can diagnose just about any engine problem not to mention ignition.
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Re: using a "scope"

Post by dannobee »

I prefer the old analog scopes, too, but they do take up a lot of room in the shop. The digital ones don't give the same output to someone who was raised on the analog scopes. Pico scope makes a version for your laptop.

MSD's read fine on an analog scope. You really see the shortcomings at higher rpms, were they're only firing once per cycle, whereas at idle, it might fire 5 times per cycle.
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Re: using a "scope"

Post by Schurkey »

Snap-On Counselor II (MT3000) "Ancient" digital-scope technology, but the most-complete diagnostic machine available in a roller-cart size rather than a giant cabinet. Does cylinder shorting, (individual, manual or automated sequence, and even/odd) dwell, dwell variation, alternator waveform, charging voltage, primary and secondary ignition, etc., and with optional accessories can do electronic compression testing via cranking rpm, low-amps probe, high-amps probe, cylinder-by-cylinder vacuum probe, and will mate with the similarly-prehistoric MT2500 scan tool to display results.

The MT3000A is very similar, has some added protection circuitry, and mates better with the exhaust gas analyzer.

I used to love working with 'scopes for ignition systems; but coil-on-plug kinda did that in. Even waste-spark/coil pack was something of a PITA, although I can get a secondary waveform from 'em.

Digital scopes are still the hot ticket for fuel pump diagnosis (along with other electric-motors--HVAC blower, electric rad fan, etc.)

Photos are blurry 'cause I couldn't use camera flash--reflected on the 'Scope screen. So longer exposure than optimum.
Examples:
Single-cylinder pattern, primary, HEI (Secondary pattern similar)
2010Feb26 002.jpg

Multi-cylinder (Parade) pattern, secondary, HEI (Primary pattern similar)
2010Feb26 007.jpg

Single-cylinder pattern, low speed, MSD 6T
K1500_6T_004.jpg

Single-cylinder pattern, higher RPM, MSD 6T
K1500_6T_006.jpg
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rebelrouser
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Re: using a "scope"

Post by rebelrouser »

I use a scope all the time. When teaching at tech school the best scopes we had were the Pico scopes installed on laptops. Since semi-retired my home shop I have an older Snap-on Modis scan tool and scope. As mentioned, anything that operates using electricity can be checked with a scope, if you know what the correct operating waveform will look like. I am a member of IATN and they have a large library of wave forms to look at and compare. Sad thing is a lot of shops and dealerships kind of got away from using ignition scopes, I remember back when I started in 1974 using a Sun scope, one of my first purchases when I bought my own shop in 1980. One problem is flat rate, takes time to set up and read a scope, especially if the computer or components are hard to get at. I always recommend taking any wave forms right at the computer, not at the sensors.
As far as being constant, good connections and interference can mess with your waveforms. And when checking sensors always use the sensor ground, not battery or chassis ground, much cleaner signal. At school our test leads took a beating from our students, many times weird patterns could be traced to a messed up lead. One of the things I have seen is that some shop lights can actually cause issues if laid too close to a scope. And while I kind of know what MSD ignition patterns should look like, most regular technicians don't have a clue. The other thing that makes me made that in dealing with tech people over the phone on like Holley and FiTech injections systems I have emailed them wave forms and asked if this is right or wrong, and it is way above their head, I think to my self really?

https://www.picoauto.com/
https://www.iatn.net/
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Re: using a "scope"

Post by David Redszus »

Without a modern digital USB scope, we would close up shop and head to the local tavern.
Of course, we do that anyway. :)

We use an eight channel, recording scope for a number of applications such as:
Ignition,
primary, secondary, voltage, current
Air mas flow
Cam sensor
Crank sensor
Lambda
Throttle position
Alternator
voltage, current
Injection
voltage, current, period, frequency
CAN bus
Brakes
ABS
Inlet air
temp
pressure
Fuel pump

We can collect data while on a dyno, parked at idle, or while on the track.
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Re: using a "scope"

Post by Racer97 »

They work great for current ramping fuel pumps,Finding Mechanical engine problems , like timing chain issues causing cam codes. I don't have a chassis Dyno but it would be a great tool for that also.
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Re: using a "scope"

Post by GerryP »

rebelrouser wrote: Sat May 21, 2022 9:49 am I use a scope all the time. When teaching at tech school the best scopes we had were the Pico scopes installed on laptops. Since semi-retired my home shop I have an older Snap-on Modis scan tool and scope. ...
You might be the guy who knows the answer to this question. To wit: Is it possible to use a standard electronics oscilloscope to capture ignition waveforms? I have a couple of analog scopes. I have a collection of probes for automotive use including inductive secondary ignition clamps. I have tried to get a viewable waveforms on the ignition and I just can't get a full waveform using any combination with volts/div selections. It seems I can see some of the coil oscillation, but nothing really discernable. Is it possible to use a standard electronics oscilloscope to get an ignition pattern? Also, I set up to parade the ignition by using the trigger on #1, but again, nothing is really useful.

The scopes work fine on other automotive waveforms, but not ignition.
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Re: using a "scope"

Post by rebelrouser »

All the old Sun scopes were analog, like a standard electronics scope. I believe the deal is the timebase of an electronic type scope. You are viewing voltage over time to get the wave form. So the scope has to be able to display the complete wave form. If the screen is too small the pattern will get too compressed to view well. An ignition pattern is fairly long as waveform go. And how you trigger the start of the wave form as well. Ignition wave forms trigger on a distributor system off number one plug for example. I know if using a magnetic pickup the resistance of the pickup really affects the wave form. I broke the pickup on my Modis and snap-on did not have them for a while I tried a couple generic ones and I got a pattern but not very usable. Several of features of the Modis did not function as well. The Modis can display the firing KV in a bar graph which I like to use, and with the generic pickups, it would not work.
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Re: using a "scope"

Post by jake197000 »

back in the 70"s my boss bought a brand new huge allen console machine.it had exhaust anilizer on it i left the probe in the tail pipe and backed the car out belly flopped that poor thing.boss said,it happens in best of families.
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Re: using a "scope"

Post by Firedome8 »

A good test is worth a thousand opinions.
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Re: using a "scope"

Post by rebelrouser »

Firedome8 wrote: Tue May 24, 2022 8:20 pm https://youtu.be/vOmPW-ze3Tc
The pattern on the scope showed some weird KV firing lines, it cleaned up under a load, but it either had some fouled plugs, or spark plug wires that are not up to snuff. Usually a short KV firing line indicates a fouled plug.
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