Input RPM signal

'Microsquirt' Transmission Control development and support.

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BMBenz
MS/Extra Newbie
Posts: 3
Joined: Mon Aug 21, 2023 3:48 am

Input RPM signal

Post by BMBenz »

I'm trying to get an input rpm signal tapping into the stock VDO tach on my Mercedes 300SD. I hear its 0-5v signal not 12v. I'm getting very erratic tach readings. is there a way to configure it to 5v or do I need a booster to get my signal to 12V?
1983 Mercedes 300SD OM617 Holset HE200wg, 7.5mm Injection pump. working on a 4L60e swap to gain overdrive and a lockup converter.
rickb794
Super MS/Extra'er
Posts: 6155
Joined: Sun Dec 21, 2008 10:28 am
Location: Portland OR

Re: Input RPM signal

Post by rickb794 »

Id put a scope on the tach signal and see what you have.

It also depends on what hardware you have.

I need a wheelbarrow full of clues to even guess.

:msq:
Correctly identify your MS ecu here
Read the Do's and Don'ts to avoid the common pitfalls before starting your install or asking for help
Use only these manuals other manuals may cause brain damage or worse.
rickb794
Super MS/Extra'er
Posts: 6155
Joined: Sun Dec 21, 2008 10:28 am
Location: Portland OR

Re: Input RPM signal

Post by rickb794 »

The MS will take a 5v signal, I d guess the trigger level is 2.5v (MS2 per setting of R56)
Correctly identify your MS ecu here
Read the Do's and Don'ts to avoid the common pitfalls before starting your install or asking for help
Use only these manuals other manuals may cause brain damage or worse.
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