Fuel Pump EMI Noise Suppression

[Spittybug]

In the continuing search for the reasons why the Megasquirt 3.57 surface mount boards have sync issues that the 3.0 component board does not, the focus continues to be on the noisy fuel pump. The attached article helps to illustrate the point.

Calling all the electrical wizards out there (Bitsyncmaster, do you read me? ), can you help to translate this into an actionable item so that we can give another try at eliminating the high RPM sync loss? What would it comprise of, where to wire it in and how?

Much appreciated!

[Bitsyncmaster]

I did not download that PDF since my work internet is crawling today.

EMI is electro-magnetic-interference. Anything that creates a spark (brushed motors) will produce it. Then it gets radiated by the power wires powering the pump. Best fix for that is to install a choke in each wire up near the pump. You would need a choke that can carry 10 amps. The highest inductance is best but your limited as to the size of the choke. One of those ferite donuts or the clamp type may work with existing wire.

Another option is to filter the noise at the ECU. That would be less problem since you're dealing with low currents. But you cannot put a choke on the ignition coil signal if that's what your using for RPM measurement. If that's the case then you need to filter at the source of the noise (fuel pump).

Are you sure it's EMI and not noise on the power into the ECU?

[Spittybug]

Thanks Dave.

Not we aren't sure. The DIYautotune guys claim that there is power feed conditioning into the unit however. We've seen the o-scope output of the VR signal prior to going into MS and even at high RPMS it doesn't break down while the resulting squared tooth signal does. This got us looking the DC issue and not ignition signal issues. It's possible the noise could be from radiator fans or blower fan too I suppose. Is there a way to measure such noise to track it down?

Can you expand a bit more on adding the choke? Simple to do?

[dmc6960]

Anyone have a spare battery you can direct wire into the fuel pump for a test run to completely isolate it from the rest of the car's wiring?

[Bitsyncmaster]

Thanks Dave.

Not we aren't sure. The DIYautotune guys claim that there is power feed conditioning into the unit however. We've seen the o-scope output of the VR signal prior to going into MS and even at high RPMS it doesn't break down while the resulting squared tooth signal does. This got us looking the DC issue and not ignition signal issues. It's possible the noise could be from radiator fans or blower fan too I suppose. Is there a way to measure such noise to track it down?

Can you expand a bit more on adding the choke? Simple to do?

If you can get a large doughnut type ferite core (maybe Radio Shack) then all you do is pull the pin, and wrap as many turns of that wire in the doughnut then put the pin back.

If you can not find some cores, pm me your address and I can send you some.

[lazabby]

It's very curious as to why the 3.0 Megasquirt runs fine but the 3.57 does not.

[Spittybug]

pRS1C-4471473w345.jpg as in one of these from Radio Shack? Just snap it on the 12v supplying the fuel pump, as close to the pump as possible? Or try and get both + and - wires through it? Boy wouldn't that be great if it ends up being this easy?

http://www.radioshack.com/product/index.jsp?productId=3012599#showFullReviews

Shannon, it could just be minor differences in the circuits or perhaps my fuel pump isn't as noisy as yours and Ian's. Who knows? We're still digging!

[Bitsyncmaster]

It's very curious as to why the 3.0 Megasquirt runs fine but the 3.57 does not.

Maybe they changed the filter values for the RPM input. Or they have a bug in new software. If they run interrupts, those bugs are so hard to trace down problems.

[Spittybug]

Maybe they changed the filter values for the RPM input. Or they have a bug in new software. If they run interrupts, those bugs are so hard to trace down problems.

It's the same software on both boards.

[Bitsyncmaster]

pRS1C-4471473w345.jpg as in one of these from Radio Shack? Just snap it on the 12v supplying the fuel pump, as close to the pump as possible? Or try and get both + and - wires through it? Boy wouldn't that be great if it ends up being this easy?

http://www.radioshack.com/product/index.jsp?productId=3012599#showFullReviews

Shannon, it could just be minor differences in the circuits or perhaps my fuel pump isn't as noisy as yours and Ian's. Who knows? We're still digging!

You can try those.

The more loops passing through the core would give you higher inductance and attenuate not only the high frequencies but low ones also. Yes, I would clip one on each pump wire.