Having Trouble with Megasquirt WI - Miata Turbo Forum - Boost cars, acquire cats.

Welcome to Miataturbo.net   Members
 


MEGAsquirt A place to collectively sort out this megasquirt gizmo

Reply
 
 
 
LinkBack Thread Tools
Old 08-07-2011, 08:56 PM   #1
Elite Member
Thread Starter
iTrader: (3)
 
Join Date: Mar 2008
Location: Granbury, TX
Posts: 6,009
Total Cats: 583
Default Having Trouble with Megasquirt WI

I implemented WI control through my MSPNP9093 as described in the MSNS-Extra Hardware Manual. See attachement. I only implemented the X2/JS0 circuit to turn the WI pump on and off with a relay ("relay 1" in the diagram). The circuit was implemented internally to the MSPNP with the "12V Ignition Feed" tied to internal, unregulated power and the "0V" tied to MSPNP ground. The only modification to the circuit is the use of a 1N4004 instead of the 1N4002 depicted.

Anyways, my issue is tied to flyback from the relay. Almost every time the WI shuts off, flyback from the relay causes noise that resets the MSPNP. The flyback diode protects the circuitry so nothing is damaged, but it is really annoying. Usually, it happens on throttle lifts for gear changes -- no big deal although I can see my tach go to 0 for a split second. However, every so often it happens on acceleration as the boost bounces around my turn-on set point (currently set a 120kPa). Since there is no deadband in the circuit, if the boost signal bounces from, say, 121kPa to 118kPa, I get a flyback event. The engine cut REALLY gets your attention.

I have some ideas to try (including the KISS method of decoupling from the MS and using a plain old boost switch). However, I wanted to see if anyone had some ideas on this. Surely, I'm not the first to try to control WI from the MS?
Attached Thumbnails
Having Trouble with Megasquirt WI-water-circuit.jpg  
hornetball is offline   Reply With Quote
Old 08-08-2011, 12:20 PM   #2
Supporting Vendor
 
Matt Cramer's Avatar
 
Join Date: Sep 2006
Posts: 2,264
Total Cats: 51
Default

You could try running the flyback diode to an external 12 volt source instead of the MSPNP's 12 volt plane.
Matt Cramer is offline   Reply With Quote
Old 08-08-2011, 12:37 PM   #3
Boost Czar
iTrader: (61)
 
Braineack's Avatar
 
Join Date: May 2005
Location: Chantilly, VA
Posts: 72,833
Total Cats: 1,786
Default

To clarify, you are only using the top p2n2222 circuit?

where exactly on the board is your diode attached to?
Braineack is offline   Reply With Quote
Old 08-08-2011, 09:05 PM   #4
Elite Member
Thread Starter
iTrader: (3)
 
Join Date: Mar 2008
Location: Granbury, TX
Posts: 6,009
Total Cats: 583
Default

Quote:
Originally Posted by Matt Cramer View Post
You could try running the flyback diode to an external 12 volt source instead of the MSPNP's 12 volt plane.
I'll give that a shot. Any thoughts on adding capacitance between the MSPNP's 12 volt plane and its ground?
hornetball is offline   Reply With Quote
Old 08-08-2011, 09:10 PM   #5
Elite Member
Thread Starter
iTrader: (3)
 
Join Date: Mar 2008
Location: Granbury, TX
Posts: 6,009
Total Cats: 583
Default

Quote:
Originally Posted by Braineack View Post
To clarify, you are only using the top p2n2222 circuit?

where exactly on the board is your diode attached to?
That's correct. Only the top circuit.

I've attached a drawing of the internal mod. The diode goes from the 2N2222 collector to what I think is unregulated 12VDC of a v3.57 board.
Attached Thumbnails
Having Trouble with Megasquirt WI-visio-mspnp-internal.jpg  
hornetball is offline   Reply With Quote
Old 08-09-2011, 09:22 AM   #6
Ben
Supporting Vendor
iTrader: (33)
 
Ben's Avatar
 
Join Date: Jul 2006
Location: atlanta-ish
Posts: 12,689
Total Cats: 99
Default

Quote:
Originally Posted by hornetball View Post
I'll give that a shot. Any thoughts on adding capacitance between the MSPNP's 12 volt plane and its ground?
It already has 3300uF.

I'd try adding a diode across the relay itself, from the coil to the high current 12V. Or replace the relay for one with built in protection.
Ben is offline   Reply With Quote
Old 08-09-2011, 11:36 AM   #7
Elite Member
Thread Starter
iTrader: (3)
 
Join Date: Mar 2008
Location: Granbury, TX
Posts: 6,009
Total Cats: 583
Default

This AM did a quickie and added an external flyback diode across the relay coil. However, wasn't able to remove the internal diode. "Seems" a bit better. When I get more time, I'll open the MSPNP and remove the internal diode from my grandaughter board. Hopefully, that will do it.
hornetball is offline   Reply With Quote
Old 08-12-2011, 06:34 PM   #8
Elite Member
Thread Starter
iTrader: (3)
 
Join Date: Mar 2008
Location: Granbury, TX
Posts: 6,009
Total Cats: 583
Default

So, finally got a chance to get inside my MSPNP and clip out the flyback diode on my "granddaughter" board. That leaves the relay in question powered by an external switched 12VDC source with a local flyback diode.

Bottom line . . . problem solved. No more noise or resets of the MSPNP.

Thanks guys.
hornetball is offline   Reply With Quote
Old 08-12-2011, 07:03 PM   #9
Ben
Supporting Vendor
iTrader: (33)
 
Ben's Avatar
 
Join Date: Jul 2006
Location: atlanta-ish
Posts: 12,689
Total Cats: 99
Default

Glad to hear.
Ben is offline   Reply With Quote
Old 02-18-2013, 10:33 PM   #10
Elite Member
 
Join Date: Jul 2005
Posts: 6,454
Total Cats: 80
Default

To avoid having to clip the internal diode, use a Schottky diode across the relay winding, such as an SB340 (3A, 40V Schottky).
JasonC SBB is offline   Reply With Quote
Old 02-18-2013, 10:36 PM   #11
Elite Member
 
Join Date: Jul 2005
Posts: 6,454
Total Cats: 80
Default

The 100 ohm resistor in the gate of the IRLZ44 should be increased to 1k in order to slow down its switching speed and noise generation. And said resistor should be mounted physically close to the MOSFET, and the trace connecting it to the gate pin should be short, as in < 1 inch. If not it can oscillate in the MHz range and cause all kinds of weird EMI problems.
JasonC SBB is offline   Reply With Quote
 
 
Reply

Related Topics
Thread Thread Starter Forum Replies Last Post
My solution for Oiltemp and Oilpressure input into Megasuirt (MS3) Zaphod MEGAsquirt 41 01-24-2016 01:25 PM
Any pnp megasquirt for 2001 Big_gumby WTB 0 09-30-2015 04:34 PM
1996 Turbo Build Goldwar DIY Turbo Discussion 2 09-29-2015 10:20 AM
First gen (white) megasquirt pnp 90-93 Miata firmware reflash Johnny Tater MSPNP 1 09-27-2015 01:38 AM
Megasquirt died mid operation psyber_0ptix MEGAsquirt 4 09-22-2015 10:35 AM


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 12:54 AM.