:::RHMT::: Real Home Made Turbo

General Category => Engine Management => Topic started by: Joseph Davis on October 28, 2011, 01:25:34 PM

Title: Intro to diagnostics
Post by: Joseph Davis on October 28, 2011, 01:25:34 PM

The site is there to sell you something, and looks like an ad-infested shithole designed in 1997, but the tech articles it directs you to via the hyperlinks on the right hand side are really quite good.

http://www.diycardoctor.com/ (http://www.diycardoctor.com/)

Title: Re: Intro to diagnostics
Post by: mrgreengenes on October 29, 2011, 12:17:58 AM

needed:  1 oscilloscope... could have used it a couple times this week.  good info on electrical diagnosis.

Title: Re: Intro to diagnostics
Post by: t_cel_t on October 29, 2011, 02:38:33 AM

cool stuff
i actually just got a scope like a week ago and immediatly ran outside and started scopeing shit on the car. i did have trouble getting it to trigger on the coil fireing(single coil) and it had a lot of shit added on(maybe interference from the coil fireing and current reversing?). know how i could clean it up?
the MS does give a perfectly square wave to the bosch igniter.
cant wait till i get another probe.

neg side of the coil
(https://realhomemadeturbo.com/forum/proxy.php?request=http%3A%2F%2Fi30.photobucket.com%2Falbums%2Fc304%2Fagent_jwa%2Fscope%2FIMG_20111027_154718.jpg&hash=0ab2489624705624503c51b67840a99dcb89f1b7)
(https://realhomemadeturbo.com/forum/proxy.php?request=http%3A%2F%2Fi30.photobucket.com%2Falbums%2Fc304%2Fagent_jwa%2Fscope%2FIMG_20111027_154715.jpg&hash=66fcba425e6ccc1037ebb669baa20efc9800e033)

and the output from the ms
(https://realhomemadeturbo.com/forum/proxy.php?request=http%3A%2F%2Fi30.photobucket.com%2Falbums%2Fc304%2Fagent_jwa%2Fscope%2FIMG_20111027_155206.jpg&hash=857ee7824a9cced8ea3e6622d1462607c8902bbe)

Title: Re: Intro to diagnostics
Post by: Joseph Davis on October 29, 2011, 02:42:56 AM

Yeah, the spike is flyback.  It's a no-no to scope the coil if you don't have a HV probe meant to deal with that sort of thing, you might wipe out the scope.

Title: Re: Intro to diagnostics
Post by: t_cel_t on October 29, 2011, 03:10:05 AM

even if its just the primary side of the coil?, probe is an older tek that says 1kV rating.

Title: Re: Intro to diagnostics
Post by: Joseph Davis on October 29, 2011, 08:02:45 AM

Flyback happens on the primary, too, which is why the ECU uses an ignitor to switch the coil. 1kV should be fine, tho... IIRC you get ~600v flyback on the primary?