Grounding Cylinder Head Test Results (2024 CX-5 Turbo)

[N7turbo]

In home electronics (audio) sometimes we get a hum from speakers from a ground and it is an undesirable result. I'm sure you could see the noise on an oscilloscope. Could there be a reason automakers don't have all these extra grounds?

 

[Koko_Bandit]

Using an *accurate* millivoltmeter, check the voltage from the battery negative post to the engine block with the engine running. Check it before and after adding the extra grounds to see if there is a difference.

 

[CrazyHippie]

Aren't you supposed to check for resistance? Ohms?

Amps is current. You know the voltage. So calculate resistance if you want to. V=IR
The higher the current at a fixed voltage, the lower the resistance.

High current is good.
Low current is bad

 

[AL Cx5]

In home electronics (audio) sometimes we get a hum from speakers from a ground and it is an undesirable result. I'm sure you could see the noise on an oscilloscope. Could there be a reason automakers don't have all these extra grounds?

I had an electrical engineer use his oscilloscope when grounding his car. Unfortunately we didn't find any change. It's been 6 or 7 years and I forget what were measuring for, amps, volts, resistance.

 

[Koko_Bandit]

I had an electrical engineer use his oscilloscope when grounding his car. Unfortunately we didn't find any change. It's been 6 or 7 years and I forget what were measuring for, amps, volts, resistance.

Oscilloscopes are designed to measure voltage unless you have a special current probe.

 

[AL Cx5]

Oscilloscopes are designed to measure voltage unless you have a special current probe.

You would think it would be just a matter of connecting a ground to one side and a body connection on the other. Maybe we flubbed the test.

 

[ADS-B]

Amps is current. You know the voltage. So calculate resistance if you want to. V=IR
The higher the current at a fixed voltage, the lower the resistance.

High current is good.
Low current is bad

View attachment 380210

I know what amps is and I know the formulas, thank you very much.

 

[Koko_Bandit]

You would think it would be just a matter of connecting a ground to one side and a body connection on the other. Maybe we flubbed the test.

Since you can see the voltage fluctuations on an o-scope and they are pretty accurate at measuring small voltages it would be a great tool to use for measuring the voltage difference between battery ground and the engine block. Many car shops that had the huge 'diagnostic machines' back in the 70's & 80's were just an o-scope.

You would be able to see the ingition pulses and measure the peak amplitudes. Adding the grounds would hopefully decrease the ampltude meaning more power to the injectors and spark plugs. The beefier grounds would also have less inductance which can add impedance (resistance at a frequency) and delay the signals to the coils and injectors. The other fundamental law of electronics is that voltage (E) moves faster than current (I) in an inductor (L). Current (I) moves faster than voltage (E) in a capacitor (C). The memory tool was ELI the ICEman.

My apologies to all for the rant.

 

[ruthrj]

In home electronics (audio) sometimes we get a hum from speakers from a ground and it is an undesirable result. I'm sure you could see the noise on an oscilloscope. Could there be a reason automakers don't have all these extra grounds?

I had a similar concern as well (ground loops). The kit shared earlier in the thread with that spider/star pattern design must have been wired that way to prevent that from occurring.

 

[RedBaron]

Nothing wrong over here. This typical. I've seen from 5 to 10 amps for 15 years.

If there's nothing wrong, then where is that current coming from? 8amps flowing through a ground strap? What the...?

 

[Jmaz]

Since you can see the voltage fluctuations on an o-scope and they are pretty accurate at measuring small voltages it would be a great tool to use for measuring the voltage difference between battery ground and the engine block. Many car shops that had the huge 'diagnostic machines' back in the 70's & 80's were just an o-scope.

You would be able to see the ingition pulses and measure the peak amplitudes. Adding the grounds would hopefully decrease the ampltude meaning more power to the injectors and spark plugs. The beefier grounds would also have less inductance which can add impedance (resistance at a frequency) and delay the signals to the coils and injectors. The other fundamental law of electronics is that voltage (E) moves faster than current (I) in an inductor (L). Current (I) moves faster than voltage (E) in a capacitor (C). The memory tool was ELI the ICEman.

My apologies to all for the rant.

Never learned anything about voltage being faster than current. Didn't know voltage had a "speed". I do understand that the speed of electron propagation through conductors varies at somewhat less than the speed of light however.
The ELI the ICE man refers to voltage (E) leads current (I) in an inductive (L) circuit and current leads voltage in a capacitive circuit. In "ELI" the "E" precedes "I" so it "leads" as it is written. In "ICE" the "I" is written before the "E" so it leads. The "leading " (and lagging also) has to due with the phase difference where the voltage and current don't rise and fall together but are offset in time relative to each other because of inductive or capacitive components/effects. Inductors and capacitors store and release energy which causes the phase difference between E and I.

 

[ruthrj]

If there's nothing wrong, then where is that current coming from? 8amps flowing through a ground strap? What the...?

Ground can be a confusing term. In
this case it’s not the scenario where you are “grounding” something like a home appliance to a ground rod. The ground straps are using the vehicle chassis to complete the circuit back to the negative terminal on the battery. You’ll see amperage across ground straps if they’re working properly.

In the case of my neighborhood, I found we actually had a problem with amperage across our “ground” in the safety sense where we had a bad neutral. Our water spigots and gutters were electrocuting us. A neighbor found his home was pulling 10 amps across their ground rod. It turns out we had a bad “neutral splice” on the line up the mountain that supplied our neighborhood. Our homes were completing the circuit back to the electric company through the earth instead of through the neutral line on the power poles.

Not sure if that helps illustrate the difference. Trying not to further confuse the matter with DC vs AC and such. I had to get a better understanding of this stuff when the Tennessee Valley Authority didn’t think it was an issue. Their engineer was convinced our homes on a “rocky” mountain didn’t “ground well”.

 

[N7turbo]

In the case of my neighborhood, I found we actually had a problem with amperage across our “ground” in the safety sense.

Does this mean the chassis becomes "live"?

 

[ruthrj]

Does this mean the chassis becomes "live"?

It’s part of the circuit and yes, technically that means it’s live. It doesn’t shock you though if you touch it. The chassis should have no difference in potential with respect to you. Even if you touch the positive terminal on a battery (don’t try it!) you still don’t get shocked unless you grab something else to complete the circuit (say the negative terminal or the chassis).

This is pretty much the reason my aftermarket backup camera worked. Hooked up the positive to the vehicles wire and snugged the “ground” to the chassis. Camera wouldn’t power on until I found a good ground as the circuit wouldn’t be complete without it.

 

[RedBaron]

Ground can be a confusing term. In
this case it’s not the scenario where you are “grounding” something like a home appliance to a ground rod. The ground straps are using the vehicle chassis to complete the circuit back to the negative terminal on the battery. You’ll see amperage across ground straps if they’re working properly.

Yeah, also a retired electronic engineer with 45 years of experience here...

Note that I simply said "ground strap". I know it's a negative 'ground' chassis. My point is that the engine block is already at negative potential based on the factory "ground straps". Adding another strap might improve that, but not to the extent of sinking 8amps of current. That's HUGE!

In the case of my neighborhood, I found we actually had a problem with amperage across our “ground” in the safety sense where we had a bad neutral. Our water spigots and gutters were electrocuting us. A neighbor found his home was pulling 10 amps across their ground rod. It turns out we had a bad “neutral splice” on the line up the mountain that supplied our neighborhood. Our homes were completing the circuit back to the electric company through the earth instead of through the neutral line on the power poles.

This is (obviously) a completely different scenario where the neutral circuit was busted, and not comparable to adding more 'ground' straps to an engine block.

Even if you touch the positive terminal on a battery (don’t try it!) you still don’t get shocked unless you grab something else to complete the circuit (say the negative terminal or the chassis).

You cannot (will not) get any shock from a 12V battery, even if you grab the +ve terminal with one hand and the -ve with the other. The potential is way too low. It would have to be 50-60 volts to even be noticeable, yet still safe (unless if maybe your heart was extremely unstable)

 

[ruthrj]

Yeah, also a retired electronic engineer with 45 years of experience here...

Note that I simply said "ground strap". I know it's a negative 'ground' chassis. My point is that the engine block is already at negative potential based on the factory "ground straps". Adding another strap might improve that, but not to the extent of sinking 8amps of current. That's HUGE!


This is (obviously) a completely different scenario where the neutral circuit was busted, and not comparable to adding more 'ground' straps to an engine block.


You cannot (will not) get any shock from a 12V battery, even if you grab the +ve terminal with one hand and the -ve with the other. The potential is way too low. It would have to be 50-60 volts to even be noticeable, yet still safe (unless if maybe your heart was extremely unstable)

My apologies! This is what happens when you get a physics BA that had more foreign language requirements than electrical instruction, AND you don’t know your audience I hope my response wasn’t too dumbed down or offensive in an attempt to make this as accessible as possible.

Resetting. I’m thinking the amperage we’re seeing across that new ground cable is current no longer being routed through the factory ground strap. If we put an extra strap there that was identical to the factory strap, I’d expect the current to find its way through both straps. With the new strap being chonky, I’m guessing it’s finding its way primarily through that new strap vs the factory strap. It didn’t jump out to me as an issue. 8 amps at 12 volts through the cable? Didnt seem to crazy to me for an engine at idle but I could be wrong. Hope you chime in with your background! 120 volts and 8 amps and yeah, we’re talking vacuum cleaners running vs enough power for your headlights.

And agreed on 12 volts and shock potential. Again, attempt was a very high level discussion and not accidentally suggesting folks go out and grab battery terminals . Skin resistance is a very real thing vs accidentally shorting your battery with a wrench.

 

[RedBaron]

If we put an extra strap there that was identical to the factory strap, I’d expect the current to find its way through both straps. With the new strap being chonky, I’m guessing it’s finding its way primarily through that new strap vs the factory strap. It didn’t jump out to me as an issue. 8 amps at 12 volts through the cable? Didnt seem to crazy to me for an engine at idle but I could be wrong. Hope you chime in with your background!

Even with the two straps having (presumably) different resistances, any current will still be split across both as a ratio between the two resistances. That means if 8amps is really running through that new strap, then the other(s) is/are carrying something less than, but approaching, that as well!

I really don't have anything more to add, but that high a current doesn't make sense. Even if it's simply the return for charge current to the battery from the alternator, it shouldn't be charging the battery at a constant 8 (or up to 16, with multiple straps!) amps, or you'd have a dead battery pretty soon.

 

[CrazyHippie]

I'm struggling a bit visualizing the circuit involved in this. If we have a nominal 14.6 volts from the alternator when the engine is running and there is a 7.5A current running through the added grounding strap vs one amp with the stock strap, then the resistance of the new strap is around 2 ohms vs 15 or so for the stock strap. Not a huge difference in resistance at all.

What I don't see is how the voltage difference that drives this current between the engine and chassis occurs. How can the engine be electrically isolated from the chassis? Do the motor mounts and exhaust hangers do this? Even if the engine is isolated, how can the engine block acquire a positive charge? Its not attached to the positive terminal of the battery, so it must be due to various electrical components that are connected to the positive side using the engine block as an isolated ground. (So I guess that I've answered my own questions.)

Interesting.

 

[ruthrj]

I'm struggling a bit visualizing the circuit involved in this. If we have a nominal 14.6 volts from the alternator when the engine is running and there is a 7.5A current running through the added grounding strap vs one amp with the stock strap, then the resistance of the new strap is around 2 ohms vs 15 or so for the stock strap. Not a huge difference in resistance at all.

What I don't see is how the voltage difference that drives this current between the engine and chassis occurs. How can the engine be electrically isolated from the chassis? Do the motor mounts and exhaust hangers do this? Even if the engine is isolated, how can the engine block acquire a positive charge? Its not attached to the positive terminal of the battery, so it must be due to various electrical components that are connected to the positive side using the engine block as an isolated ground. (So I guess that I've answered my own questions.)

Interesting.

Hah, I think you did! I had the same questions and conclusions. Never thought too hard about it until I stumbled on this thread.

For your next trick, you could try to explain the difference between ground and grounding to a retired EE

I’m revoking my internet license thru the end of the week.

 

[Koko_Bandit]

The ELI the ICE man refers to voltage (E) leads current (I) in an inductive (L) circuit and current leads voltage in a capacitive circuit. In "ELI" the "E" precedes "I" so it "leads" as it is written. In "ICE" the "I" is written before the "E" so it leads. The "leading " (and lagging also) has to due with the phase difference where the voltage and current don't rise and fall together but are offset in time relative to each other because of inductive or capacitive components/effects. Inductors and capacitors store and release energy which causes the phase difference between E and I.

That is what I was trying to say, I just didn't do a very good job of choosing my words.

The Holidays have been brutal, I can't wait until Wednesday to get back to my routine.