Calling all input circuit genius type people - Page 2 - Miata Turbo Forum - Boost cars, acquire cats.

Welcome to   Members

MEGAsquirt A place to collectively sort out this megasquirt gizmo

LinkBack Thread Tools
Old 08-05-2008, 09:24 AM   #21
Supporting Vendor
Matt Cramer's Avatar
Join Date: Sep 2006
Posts: 2,266
Total Cats: 51

Take the heater ground out of the MS and run it straight to the engine block. Older LC-1s had a signal ground for running to the MS, but this one does not need to be grounded to the MS and would be better off grounding both its grounds to the engine block. However, running the logic ground to the MS isn't as bad as running the heater ground to it.
Matt Cramer is offline   Reply With Quote
Old 08-05-2008, 10:24 AM   #22
Junior Member
Thread Starter
iTrader: (1)
Join Date: Apr 2008
Location: Bristol
Posts: 442
Total Cats: 0

I'll be putting my NB O2 sensor back in for running the stock ECU so once the WB is out (not gonna cook it by running the engine without powering it) I'll try running the MS without the LC-1 and see what that does.

Grounds have always been a bit of a mystery to me. I understand how a ground loop works but my MS is grounded to the head (bolt near the TB) so if I ground the LC-1 to the same point how is it different to grounding it to the MS? I really should look into where all of my grounds go (2A,2B,2C,2D) One goes to the stud on the TB but the others im not sure.
Duckie_uk is offline   Reply With Quote
Old 08-05-2008, 12:02 PM   #23
Elite Member
Join Date: Jul 2005
Posts: 6,454
Total Cats: 80

If the MS has only one ground (the ground plane), all sensor grounds should return to it, without being connecte to the head/block/chassis on the way. IOW bring a wire from the MS circuit board ground plane out, and call this wire "sensor ground". Connect all sensor grounds to it and don't connect them to the head or block or chassis or anywhere else. This way the sensors have a direct, dedicated connection to the ground plane, so the MS sees a clean signal from them.

Bring a 2nd wire, a thicker one, from the MS circuit board ground plane out, (preferably near the pull-down MOSFET drivers) and connect this to the head, this will be your "power ground".

I do power and analog electronics design for a living (20 years now, I'm old), and I teach grounding and layout to the young 'uns in the company.

If someone can point me to a schematic and layout of the MS, and the schematic of the sensor input circuitry, I can make a more detailed grounding scheme, and design a better input conditioning circuit for the CAS.
JasonC SBB is offline   Reply With Quote
Old 08-05-2008, 12:28 PM   #24
Junior Member
Thread Starter
iTrader: (1)
Join Date: Apr 2008
Location: Bristol
Posts: 442
Total Cats: 0

Hi Jason, Thanks for the interest. I did try running separate wires directly from the CAS round the outside of the car to the MS without any success. But I'm not going to start running permanent extra wires or clipping away at the original harness because that kind of defeats my PNP goal. My thinking in the matter is if its good enough for the OEM ECU then its good enough for me.

I think that we have narrowed the candidates down to either poor construction (e.g. me grounding the LC-1 through the MS) or me having a sick/dead/dieing CAS (has happened to others though very subjective)

I'm not sure about the MS. I think they consolidated all of the grounding into a plane bacause the 2.2 boards kept killing traces.

I have attatched the wiring diagrams for educational purposes. It has quite a good over-view of the grounding layout.
Attached Files
File Type: pdf 94sys.pdf (644.7 KB, 50 views)
Duckie_uk is offline   Reply With Quote

Related Topics
Thread Thread Starter Forum Replies Last Post
Need help - Stock Balancer and Fastforward overlay pulleys Frank_and_Beans Supercharger Discussion 13 09-12-2016 09:17 PM
LucaCarMods's Boosted Dutch Miata Build! LucaCarMods Build Threads 11 02-14-2016 07:13 AM
My solution for Oiltemp and Oilpressure input into Megasuirt (MS3) Zaphod MEGAsquirt 41 01-24-2016 01:25 PM
"Chimney Ethanol" E100 MiataGarage Engine Performance 5 09-30-2015 12:04 AM
WTB HPDE miata - Texas Voltwings Cars for sale/trade 0 09-27-2015 07:40 PM

Thread Tools

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off

All times are GMT -4. The time now is 02:04 PM.