Can't stop noise issues

Tuning concepts, methods, tips etc.

Moderators: jsmcortina, muythaibxr

Post Reply
smokey212
Helpful MS/Extra'er
Posts: 59
Joined: Sun Jul 15, 2012 11:16 am

Can't stop noise issues

Post by smokey212 »

So listen up folks. I've moved my grounding points and cleaned connections and tried lots of different sizes and lengths of ground wires. I read the proper grounding rules given in the ms2/extra manual but I run the relay board so I can't really run individual small wires to help reduce the voltage drop of the ground. Below is the configurations I've tried.

1. Blue white LC-1 grounds and relay board ground all grounded at the neg batt cable.
2. same wires grounded to engine head with neg batt cable grounded (0 ga wire) to frame w/ ground wire from frame to engine block(4 ga wire). I also have a 4 ga grounding wire from the alt case to this same point. I run a 1 wire alt on this setup.

3. Properly cleaned all grounding locations with bonding brush and cleaned with alcohol just like we do on aircraft.

Oh and currently I am pulling the tach signal from the MSD 6AL tach pin that is built into the box. I am not controlling the ignition yet, but that is my next move as soon as I can get the noise issue solved.

I cannot get the spikes to go away in my battery voltage and RPM. They are not so bad I can't tune because the truck is running good right now but I am trying to finalize the VE table. I upgraded the firmware to MS2/extra 3.3.1. See below for full specs and msq/msl.

MS2 w/ 3.3.1 firmware
Ford 302 V8 w/ GM TBI 55lb hr inj

MSD 6AL w/ MSD magnetic pickup dizzy.
I will post my tune and msl in the morning. I had them uploaded in the ms2 forum but my post was moved due to the fact I'm using the new firmware.
mustangjp
MS/Extra Newbie
Posts: 20
Joined: Thu Mar 14, 2013 10:37 pm

Re: Can't stop noise issues

Post by mustangjp »

I too run an MSD 6AL box triggered off of an MSD dist and had a similar issue to what you described. I spent a lot of time checking and redoing grounds and connections with no improvement. My problem mainly showed up in the MAP signal, but eventually it started to show in the RPM as well. I would get random spikes showing in the data logs. The problem got progressively worse. Right before I discovered the problem I would see momentary RPM spikes up to as much as 60,000 rpm. Needless to say the MS didn't like that and would actually cut the fuel off at that moment. Last trip out with this problem I thought I'd be coming home on a tow truck because it got so bad. Anyway once I saw the RPM spikes in the data log I decided to run a temporary tach signal wire from the 6AL to the MS-2. Ran perfect with the new wire. Seems that I had the original tach signal wire too close to the 6AL output wires(orange & black) and that energy was bleeding over. I've since rerouted the tach signal wire well away from the output wires and it has been perfect ever since.
MS2 on Ford 351C, custom internal crank trigger, FAST EZ-EFI TBI, LS truck coils in wasted spark
DaveEFI
Super MS/Extra'er
Posts: 4175
Joined: Sun Apr 15, 2012 12:55 am
Location: SW London, UK

Re: Can't stop noise issues

Post by DaveEFI »

Try the trick of unplugging the MS (leaving the lead between it and the relay board in place) and checking all the sensor grounds on the relay board to true ground with a DVM set to resistance or continuity. If it is showing a ground you have your problem. Did you make up the DB37 to DB37 lead that goes from MS to relay board or buy a ready made one? What you need to check on that is Pin 19 at the relay board end has a wire running to one of the ground pins at the MS end, and not connected to anything else.
Rover SD1 3.5 EFI
MS2 V3
EDIS
Tech Edge O2
London UK.
slow_hemi6
Super MS/Extra'er
Posts: 4122
Joined: Fri May 07, 2004 3:33 am
Location: Australia

Re: Can't stop noise issues

Post by slow_hemi6 »

Are you using the fancy msd low resistance wires and non resistor spark plugs with that set up?
Find the Manuals up top under Quick links: Manuals. :RTFM:
Cheers Luke
arran
Master MS/Extra'er
Posts: 617
Joined: Mon Oct 29, 2012 2:34 am
Location: Brisbane Australia
Contact:

Re: Can't stop noise issues

Post by arran »

Yes, my first thought is ignition rather than grounds.

What happens to the observed noise if you run the ignition system in test mode with the engine off?
slow_hemi6 wrote:Are you using the fancy msd low resistance wires and non resistor spark plugs with that set up?
RX7 Series 2 13B Turbo. Megasquirt 3 with 3X Expander and V3 CPU. Firmware 1.4.1
Knock module, twin EGT, real time clock, WBO2, full sequential fuel and spark
http://web.aanet.com.au/arran
smokey212
Helpful MS/Extra'er
Posts: 59
Joined: Sun Jul 15, 2012 11:16 am

Re: Can't stop noise issues

Post by smokey212 »

As promised below I posted the msq and msl. To answer the questions above:

1) No continuity between sensor grounds and ground w/ relay cable unplugged from MS.
2) I Checked all connections on the relay board just for fun and found 236 ohms between the tach in and batt neg. When I unplug the tach in from the MSD box pin it goes open.

3) I'm not running and fancy low resistance wires, they are regular auto parts store plugs. The plugs are Bosch Platinum DR8BPX resistor plug.
mustangjp
MS/Extra Newbie
Posts: 20
Joined: Thu Mar 14, 2013 10:37 pm

Re: Can't stop noise issues

Post by mustangjp »

I looked over your datalog briefly. I saw a some instances of random rpm spikes that looked the same as the problem I was having. I would definitely be looking at spark energy bleeding over from the 6AL output into the tach wire. Try running a temp wire from the tach terminal to the MS. Keep it a minimum of 10" away from the output leads, spark plug wires and coil. Same goes for any of the other sensor wiring. Also don't assume that a problem seen on one sensor is caused by interference on that channel. Could be picked up on one and seen on another.
MS2 on Ford 351C, custom internal crank trigger, FAST EZ-EFI TBI, LS truck coils in wasted spark
smokey212
Helpful MS/Extra'er
Posts: 59
Joined: Sun Jul 15, 2012 11:16 am

Re: Can't stop noise issues

Post by smokey212 »

I'm running shielded wire from the tach output on the MSD to the relay board. It is also not close to any other high current wiring. I do have the shield grounded in the same pin as the clt ground though.

As I said before I've moved the grounds all over and multiple configurations with no change in behavior.
arran
Master MS/Extra'er
Posts: 617
Joined: Mon Oct 29, 2012 2:34 am
Location: Brisbane Australia
Contact:

Re: Can't stop noise issues

Post by arran »

Is there some reason you are reluctant to try this very simple test?
You've investigated grounds in detail, no fault found, move on
arran wrote:Yes, my first thought is ignition rather than grounds.

What happens to the observed noise if you run the ignition system in test mode with the engine off?
slow_hemi6 wrote:Are you using the fancy msd low resistance wires and non resistor spark plugs with that set up?
RX7 Series 2 13B Turbo. Megasquirt 3 with 3X Expander and V3 CPU. Firmware 1.4.1
Knock module, twin EGT, real time clock, WBO2, full sequential fuel and spark
http://web.aanet.com.au/arran
Post Reply