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-   -   Testing methods for Light Misfires (http://productforum.autorepairdata.com/forum/showthread.php?t=11101)

crackerclicker 11-13-2015 01:14 AM

Quote:

Originally Posted by Crusty (Post 51069)
Cylinders would fire properly and then not fire properly and that older ignition trace used to show that if you watched closely. It's been one of my bugaboos for several decades and yes I am fully aware of what the new scopes can do, but I'm old enough to recognize what they don't do anymore as well

I'm fairly certain we've argued on this or a similar topic before, but I'm unconvinced you've truly explored all the options available. Personally I find only a little value in examining secondary the way you describe, however I believe what you desire is available in Picoscope's "rapid trigger" feature (other quality DSO manufacturers likely have a similar feature).

Crusty 11-13-2015 02:45 AM

Quote:

Originally Posted by crackerclicker (Post 51107)
I'm fairly certain we've argued on this or a similar topic before, but I'm unconvinced you've truly explored all the options available. Personally I find only a little value in examining secondary the way you describe, however I believe what you desire is available in Picoscope's "rapid trigger" feature (other quality DSO manufacturers likely have a similar feature).

I'm unconvinced you've stood in front of a vehicle watching the scope screen and both heard the misfire and seen the misfire at exactly the same time, and I do mean exactly, positively identifying the cylinder or multiple cylinders, which used to be a normal capability of older mainstream scopes prior to the digitizing that began in the early 1980's, not just one specialty scope using one feature.

Whatever else is going on, the desired result is in fact that secondary firing of the plug, in the hole, under compression, with fuel delivered, completing the burn and the expanding gasses pushing the piston down.
Whatever the primary ignition is doing does not always translate to the secondary doing what it is supposed to do.

snapon20r 11-13-2015 03:49 AM

Quote:

Originally Posted by diesel71 (Post 51099)

Thankyou diesel71 for your pictures and info, that will be a big help.

snapon20r 11-13-2015 03:50 AM

And thankyou to everybody else for your replies.

crackerclicker 11-13-2015 03:11 PM

Quote:

Originally Posted by Crusty (Post 51108)
I'm unconvinced you've stood in front of a vehicle watching the scope screen and both heard the misfire and seen the misfire at exactly the same time, and I do mean exactly, positively identifying the cylinder or multiple cylinders, which used to be a normal capability of older mainstream scopes prior to the digitizing that began in the early 1980's, not just one specialty scope using one feature.

http://www.mikejonesauto.com/

Give him a call, he's a big fan of Rapid Trigger.


Quote:

Originally Posted by Crusty (Post 51108)
Whatever the primary ignition is doing does not always translate to the secondary doing what it is supposed to do.


Agreed, not sure what your point is.

Joe Rappa 11-13-2015 04:47 PM

There are some folks that are VERY accomplished when it comes to analyzing vacuum waveforms from the intake and pressure waveforms from the exhaust. If it's a mechanical problem with the engine(and you're looking for sticking valves), you can certainly see waveform changes if you do those measurements. I've got a friend that swears by the Sen X First Look.

Joe

Crusty 11-14-2015 03:04 AM

Quote:

Originally Posted by Joe Rappa (Post 51137)
There are some folks that are VERY accomplished when it comes to analyzing vacuum waveforms from the intake and pressure waveforms from the exhaust. If it's a mechanical problem with the engine(and you're looking for sticking valves), you can certainly see waveform changes if you do those measurements. I've got a friend that swears by the Sen X First Look.

Joe

Good point Joe. I've been so used to hooking up vacuum gauges to see how the engine is breathing that it's second nature and I had forgotten to even mention it. Fundamentally the valves dictate how the engine breathes.
It is getting harder and harder to access a vacuum source on todays' engines but worth the effort.
Diesel engines don't need the spark plug to complete the combustion so I can certainly see where the pressure transducer in place of the glow plug would work just fine. It eliminates a very necessary part of the entire cycle in a gasoline application though.

Question; does the First Look system have a quick and easy way to measure both the air entering the engine (via air in the intake duct, OR, the vacuum) and the exhaust out at the same time, and then graph the two well on a scope screen-??

Crusty 11-14-2015 03:08 AM

Quote:

Originally Posted by crackerclicker (Post 51134)
http://www.mikejonesauto.com/

Give him a call, he's a big fan of Rapid Trigger.


Ummm it's still one system, not the mainstream norm the way secondary ignition scopes used to be


Agreed, not sure what your point is.

Ummm misfires...

crackerclicker 11-15-2015 01:40 AM

"You can lead a horse to water . . . "

Crusty 11-15-2015 03:58 AM

Quote:

Originally Posted by crackerclicker (Post 51160)
"You can lead a horse to water . . . "

Young bull, old bull...


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