12v noise

[Suprazz]

I'm having big issue with noise on the 12v of the car.

I installed a ms1extra last year. Everything was working fine. Then this winter, the owner of the car rebuilted the engine.
Engine: 2jz-gte
running ms1 with low impedance injectors with a resistor pack
3x MSD twin towers coil pack drive by original igniter.

After the rebuild, the guy was having troubles with hard cuts on with the ms. There is so much noise that the ecu reset everytime he hit boost and fews times at idle...
I double checked all grounds and everything is like before. I'm already using a capacitor on the igniter.

I can add a capacitor to the MS but this wont solve my problem... I will try to add a capacitor near the twin towers coils pack.

But I still dont understand why is was running well last year.

This is what it look like at 1000 rpm. Noise increase with rpm

[Matt Cramer]

Where is the MS getting power and ground?

[Suprazz]

From b+ (factory ecu 12v) and a good body ground.

[Matt Cramer]

From b+ (factory ecu 12v) and a good body ground.

In my experience, there's rarely such a thing as a good body ground. I recommend grounding the MS to the engine block or cylinder head. There's a reason most OEM wiring harnesses do this.

[Suprazz]

ok I'll try this.

BTW this is what it look like when I hit boost. I add a 220uF capacitor to the ms so it help a little bit for the noise at idle. You can see while rpm are growing, noise increase and at ~10 psi I always have a big glich and the ecu reset and I'm also loosing the communication with TS.

[Suprazz]

little update.

You were right, a good engine ground is a WAY better than a body ground.

But I still have my problem.

This time, I kept the pedal to the floor and it keeps resetting.

[Matt Cramer]

Can you post a data log of the resets?

[Suprazz]

yes but almost every time I'm loosing communication after the first "cut"...

[Matt Cramer]

Try soldering a 0.1 uF capacitor across the boot header.

[Suprazz]

I added a 0.22uF between pin 2 and 6 of the CPU and also between pin 1 and 2.

I also added a 1nF to the bootloader jumper.

And a 220uF on the 12v input of the megasquirt

[jsmcortina]

I also added a 1nF to the bootloader jumper.

Why so small?

James

[elaw]

Is your fuel pump powered from the same line that feeds the Megasquirt?

I fought with similar issues for a long time and finally set up the fuel pump to draw power from another circuit and the problems vanished.

[Suprazz]

Ok, I'll try bigger on the bootloader jumper.

Yes the fuel pump is on another circuit.

[Suprazz]

I made other tests, It changed nothing. I added a bigger capacitor on the bootloader jumper.

I dont know why but yestesday, the car was running a way too rich. The day before yesterday, idle was a 14,7. Yesterday, I after the warmup, i was running less than 11 a idle and idling was hard.

And Same problem, I have an other datalog.

[jsmcortina]

Lets get back to basics here.
Nothing changed with the Megasquirt over the winter but now the car is running badly ?
Don't look at the Megasquirt! Look at what else changed on the car.

James

[Kmsgli]

I had a simmilar issue with my VR6 turbo when i first got it running and i have a noisy 12v Batt signal and I chased my tail for months only to find out I carelessly put factory Spark plugs in the car and under boost they where detonating as they run hot (platnum +4's). Im not saying that is your issue but the wrong spark plugs in a car that boosts more then it should will give you a nasty bucking hesitation during boost but drive regular while cruising.

Its worth looking at your plugs before you start ripping your MS apart like i did. May be wrong but its easy enough to try.

[Suprazz]

good to know.

I noticed yesterday that the car is running with ngk g-power spark plug and normally I use ngk copper type or v-power but I didn't try to change the sparkplugs.

Now car is running a way better (I moved few other grounds but I'm still don't understand what's happening). I can make pulls and run the car run great but the ms reset is still happening under boost.

[Suprazz]

Ok,

I changed the megasquirt for an other one of a friend.

Car is running a way to rich with the exact same progarmmation.

The megasquirt of my fried don't reset but I'm always loosing communication with tunerstudio 1.50

[Peter Florance]

MegaSquirt installations should pass this test:

if you unplug MS box and measure resistance from any sensor's (MAT, CLT, TPS) ground to car/engine ground , you should not have continuity.

[Suprazz]

Thank you. This solve my problem. I realised that the MAT and TPS were grounded on the intake manifold.

Now everything work a way better.

Btw with all this problems, I realised that the maximum and minimum baro correction limits don't seems to work on 029y4 because when the ms reset, baro was at ~140 kPa and my maximum was set a 105.