Isolating the case from ground

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jsdevel
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Isolating the case from ground

Post by jsdevel »

Not sure if this will be of help to anyone, but here's how I'm isolating my case from chassis ground. I obtained these 1/4" nylon bolts from the Depot.

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nathaninwa
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Re: Isolating the case from ground

Post by nathaninwa »

Good idea. I think though that nothing touches the case on the Inside, if anything, I've used the rubber isolater mounts like on the msd boxes to isolate from vibration in my chassis rail
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Re: Isolating the case from ground

Post by Rick Finsta »

I used the MSD mounts on mine.
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Re: Isolating the case from ground

Post by racingmini_mtl »

nathaninwa wrote:I think though that nothing touches the case on the Inside
The voltage regulator, through its metal tab, is grounded to the heat sink which is itself in contact with the case.

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piledriver
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Re: Isolating the case from ground

Post by piledriver »

The case is shielding, why are we trying to insulate it from ground?

It's might be possible if you use insulated tab (or ditch) the all mainboard drivers, but why?

A VR or other shielded cable can induce ground loop noise in some cases...
... and might be isolated on one end but the case is the end that stays grounded.

Every ground in my systems runs back to the MS,(mount plate, but the unit and stubby grounds of harness all join there)
... except for the LS2 coil power ground.

On my first system, the injector and coil drivers were in an external case, only connected by a shielded low current signal cable.
Always doing things the hard way, MS2 sequential w/ v1.01 mainboard, LS2 coils. 80 mile/day commuter status.
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Re: Isolating the case from ground

Post by jsmcortina »

piledriver wrote:The case is shielding, why are we trying to insulate it from ground?
Ground loops?
If the internal circuits are grounded to the engine or battery, but the case is connected to the body, there could be a potential difference.

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piledriver
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Re: Isolating the case from ground

Post by piledriver »

That's why I never ground anything to the engine except noisy high power grounds, if only to keep them short.
A short, fat ground is a good ground, I always try to keep them down to <6".
Makes more sense on a rear engined car with the battery under the back seat, ~next to the ECU.
I treat the ECU mount as the "engine" for grounding purposes.
(3mm aluminum plate)

A long high powered ground (or power feed) is also known as an "antenna".

On a car with the battery right next to the motor, the "standard" setup probably works, if only due to the short battery to block cable. Not an option for me, and grounding things through the engine as recommended made for a noisy mess.

Keeping the ground path short and fat, and keeping the high powered ignition noise out of the ECU did wonders.
(A few ferrites seem to have suppressed the remainder)
Always doing things the hard way, MS2 sequential w/ v1.01 mainboard, LS2 coils. 80 mile/day commuter status.
billr
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Re: Isolating the case from ground

Post by billr »

I have the other extreme... battery in the rear and no cable from it to the engine or MS "ground" point. I also run wiring in-and-around the coils; the (Hall) cam sensor and a fuel-pressure sensor even get power/ground from the coil driver module, in a harness common with the signals. I do use spiral-core plug wires, resistor plugs, and have some signal wires in shielded cable, but am still impressed with how tolerant my MS3X seems to be toward the "noise bogeyman".

Understand, I'm not trying to talk anybody into adopting "bad" grounding practices, but I feel grounding is too often blamed, and chased, when the root problem is unknown.
jsdevel
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Re: Isolating the case from ground

Post by jsdevel »

billr wrote:I have the other extreme... battery in the rear and no cable from it to the engine or MS "ground" point. I also run wiring in-and-around the coils; the (Hall) cam sensor and a fuel-pressure sensor even get power/ground from the coil driver module, in a harness common with the signals. I do use spiral-core plug wires, resistor plugs, and have some signal wires in shielded cable, but am still impressed with how tolerant my MS3X seems to be toward the "noise bogeyman".

Understand, I'm not trying to talk anybody into adopting "bad" grounding practices, but I feel grounding is too often blamed, and chased, when the root problem is unknown.
I'm really feeling this sentiment right now :D I've been chasing the cause of my secL resetting for months now which is what led me to isolating the case from chassis ground. Still chasing the secL reset, but that's another topic.
piledriver
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Re: Isolating the case from ground

Post by piledriver »

Pick up a selection of split ferrites fron Digikey, try them in different locations.
(power feeds mostly)

They can do no harm, and can fix odd, intermittent issues.

Put one on the coil power feed at least, near the coils with as many turns as will wrap around.
I also have one on my AC system feed as I would get a reset every time the AC cycled.
Stopped the instant i clipped a ferrite on.
Always doing things the hard way, MS2 sequential w/ v1.01 mainboard, LS2 coils. 80 mile/day commuter status.
jsdevel
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Re: Isolating the case from ground

Post by jsdevel »

piledriver wrote:Pick up a selection of split ferrites fron Digikey, try them in different locations.
(power feeds mostly)

They can do no harm, and can fix odd, intermittent issues.

Put one on the coil power feed at least, near the coils with as many turns as will wrap around.
I also have one on my AC system feed as I would get a reset every time the AC cycled.
Stopped the instant i clipped a ferrite on.
Interesting. So it's possible then that I have EMI / RFI interference. I suppose that makes sense.

I do have a lot of wires in my case for the P&H injector board and some additional prototype board. Is it possible to detect EMI/RFI intereference? Is there a tool for that?
piledriver
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Re: Isolating the case from ground

Post by piledriver »

jsdevel wrote:
piledriver wrote:Pick up a selection of split ferrites fron Digikey, try them in different locations.
(power feeds mostly)

They can do no harm, and can fix odd, intermittent issues.

Put one on the coil power feed at least, near the coils with as many turns as will wrap around.
I also have one on my AC system feed as I would get a reset every time the AC cycled.
Stopped the instant i clipped a ferrite on.
Interesting. So it's possible then that I have EMI / RFI interference. I suppose that makes sense.

I do have a lot of wires in my case for the P&H injector board and some additional prototype board. Is it possible to detect EMI/RFI intereference? Is there a tool for that?
There are, even an AM radio works pretty good (not tuned to any station) but its hard to localize noise sources that way.
...but since we largely know the sources, (alternator, ignition coils, electric motors or large coils like an AC clutch) its pretty fast/easy/effective just to hit the known offenders preemptively.

Physical separation also works... technique is to split the harnesses, sensors cable runs to one side, all drivers and 12v power down the other side of the engine/car. The less area in proximity the less potential crosstalk.

First MS2 I built has a 4 channel lowZ and a 4 channel ign driver in a spare MS1 box, mounted on other side of car, sensors went straight back from the MS2, all the high power stuff from the other box was on the other side of the car, only connected via a shielded cable with 5v logic and gnds.
Bit of extra work, ONCE.
Zero noise issues.
Last edited by piledriver on Sun Mar 12, 2017 1:01 am, edited 1 time in total.
Always doing things the hard way, MS2 sequential w/ v1.01 mainboard, LS2 coils. 80 mile/day commuter status.
jsdevel
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Re: Isolating the case from ground

Post by jsdevel »

Know of any good wire shielding? It would be nice to have my sensor cables wrapped up in some just to keep my harness going through the firewall at the same location.

I will say that MS definitely isn't for the faint of heart :D My wife has been driving me to work for the past 3 months. Boy am I thankful for her!

I'll order some ferrites. It would be nice though to peak inside the case while it's running, have a debugger hooked up to the controller and see exactly what's causing secL to reset. Process of elimination is a time consuming process (sorry to be calling for the wambulance here).
piledriver
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Re: Isolating the case from ground

Post by piledriver »

Its better/faster/easier to follow best practices.

You can buy wire braid in many sizes, its flat, but its also a hollow tube when expanded.
You shouldn't need that.

Also make sure you are running resistor plugs/wires etc.

My original VW alternators were putting out huge noise (tried a few, known good spares and a rebuilt) finally installed a late model GM alternator. Day and night difference on noise on 12v.
Always doing things the hard way, MS2 sequential w/ v1.01 mainboard, LS2 coils. 80 mile/day commuter status.
jsdevel
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Re: Isolating the case from ground

Post by jsdevel »

First MS2 I built has a 4 channel lowZ and a 4 channel ign driver in a spare MS1 box, mounted on other side of car, sensors went straight back from the MS2, all the high power stuff from the other box was on the other side of the car, only connected via a shielded cable with 5v logic and gnds.
Bit of extra work, ONCE.
Zero noise issues.
I like it. I'm definitely going to isolate my signal wires then and see if it makes a difference. If you have time, could you look at my logs? Do they look noisy to you?
jsdevel
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Re: Isolating the case from ground

Post by jsdevel »

Sorry, too many topics going on right now. This topic has my latest log files: http://www.msextra.com/forums/viewtopic ... 01&t=65464
jsdevel
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Re: Isolating the case from ground

Post by jsdevel »

piledriver wrote:Pick up a selection of split ferrites fron Digikey, try them in different locations.
(power feeds mostly)
So I tried this on my LC2 wideband controller to reduce the noise coming from that source. Check this out https://youtu.be/aMzkowv9awg. I'm thinking I'll need to move the relay right next to it to avoid it's power feed/ground from entering the ECU location. I can hear this noise like crazy with an AM radio!
piledriver
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Re: Isolating the case from ground

Post by piledriver »

Straight through? Nonononono...

You need a larger ferrite, and put as many turns of wire as will fit in it.
Put it as close as possible to the LC2 as well.


A ferrite with wire wrap is an inductor.
The more turns of wire, the more inductance, the more HF suppression.
Also note a small transformer works just fine too, as long as the coil can carry the current.
Stick a couple 50V 1uF chip caps to ground have you have a pretty decent noise filter.
Make sure the power ground on that thing is within ~6" of it, or its a broadcasting antenna.

I know its a switcher for the heater current, but you'd think they'd filter it better.
Always doing things the hard way, MS2 sequential w/ v1.01 mainboard, LS2 coils. 80 mile/day commuter status.
jsdevel
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Re: Isolating the case from ground

Post by jsdevel »

piledriver wrote:Straight through? Nonononono...

You need a larger ferrite, and put as many turns of wire as will fit in it.
Put it as close as possible to the LC2 as well.


A ferrite with wire wrap is an inductor.
The more turns of wire, the more inductance, the more HF suppression.
Also note a small transformer works just fine too, as long as the coil can carry the current.
Stick a couple 50V 1uF chip caps to ground have you have a pretty decent noise filter.
Make sure the power ground on that thing is within ~6" of it, or its a broadcasting antenna.

I know its a switcher for the heater current, but you'd think they'd filter it better.
Thanks for the clarification! Electronics noob here. I'll post back once I have the noise squelched.
jsdevel
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Re: Isolating the case from ground

Post by jsdevel »

I think I have noise out of the way. All my signals appear to be pretty stable. I'm STILL battling resets.

Here's my new theory: Invalid Closed Loop Idle Settings
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