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

[CrazyHippie]

Hah, I think you did! I had the same questions and conclusions. Never thought to 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.

I think that 'ground' describes the result of using a mortar and pestle, while 'grounding' is the process itself.

 

[AL Cx5]

It's gratifying you guys dove into why I'm reading 5 to 10 amps at the engine to chassis ground. The other question is why do these ground cables improve performance ever so slightly?

When I took these readings, the motor was running, HVC fan on high and headlights were on. It would have dropped about 50% if I had turned these two items off. The headlights and HVC fan motor are not attached to the engine but are part of the entire chassis ground circuit.

On my race car, we run a small nicad 16v battery. We have separate power and grounds to the ECU, TCU and coils, {16} 40,000 volt coils in this case, wired directly from the battery terminal. This avoids "noise" from electric motors like the fuel pump and radiator fan. The other devices, fuel pump, trans and rad fans and all the other sensors are powered from the battery and ground to the chassi.

The dirty circuit and clean circuits overlay each other where they attach to the battery terminals.

Maybe you will explain why this works. My theory, the battery absorbs the noise from the electric motors and the noise does not backfeed to the ECU, TCU or coils.

 

[Koko_Bandit]

It's gratifying you guys dove into why I'm reading 5 to 10 amps at the engine to chassis ground. The other question is why do these ground cables improve performance ever so slightly?

When I took these readings, the motor was running, HVC fan on high and headlights were on. It would have dropped about 50% if I had turned these two items off. The headlights and HVC fan motor are not attached to the engine but are part of the entire chassis ground circuit.

On my race car, we run a small nicad 16v battery. We have separate power and grounds to the ECU, TCU and coils, {16} 40,000 volt coils in this case, wired directly from the battery terminal. This avoids "noise" from electric motors like the fuel pump and radiator fan. The other devices, fuel pump, trans and rad fans and all the other sensors are powered from the battery and ground to the chassi.

The dirty circuit and clean circuits overlay each other where they attach to the battery terminals.

Maybe you will explain why this works. My theory, the battery absorbs the noise from the electric motors and the noise does not backfeed to the ECU, TCU or coils.

The battery is essentially a big capacitor so it does filter out a lot of noise. The ECU and TCU are designed with internal filtering and grounds to block or eliminate noise from getting in or out.

I worked for the automotive electronics division of GM for 24 years. The EMI/RFI testing was the hardest part of validating a new product design.

 

[AL Cx5]

The battery is essentially a big capacitor so it does filter out a lot of noise. The ECU and TCU are designed with internal filtering and grounds to block or eliminate noise from getting in or out.

I worked for the automotive electronics division of GM for 24 years. The EMI/RFI testing was the hardest part of validating a new product design.

That had to be interesting work!

 

[Koko_Bandit]

That had to be interesting work!

It was. I got to drive the first prototypes of the ZR1 while it was being developed.

 

[AL Cx5]

It was. I got to drive the first prototypes of the ZR1 while it was being developed.

It says alot for Mazda an automotive EE owns one.

What are your impressions of the Mazda wiring system? I've been impressed with the attention to detail, supports and attachments. I compare it to my 06 Dodge Ram diesel. The Mazda wiring makes the Ram wiring look like a high school kid wired the truck.

Maybe wiring doesn't have to be supported as often or loombed as well as Mazda. My truck just turned 20 years old. I keep repairing everything but the engine. It runs great. LOL

Also, do you replace engine management sensors at some mileage/time intervals or maybe you don't keep your cars that long? I've kept this truck longer than any vehicle. Living in Alabama, we don't have the corrosion issues. The body and frame are rust free.

 

[CrazyHippie]

I wonder if the engine block also acquires some sort of capacitive charge (due to all of the moving parts or some such) that interferes with the injectors, throttle body controls, etc., and when discharged to the frame, improves performance of the engine electrical devices. 5-10 amps of current through the ground wire is not trivial, and the engine surely must be electrically isolated by rubber mounts for the potential difference to develop? I'm not very smart with these things; Koko, any additional insight?

 

[Koko_Bandit]

I have not dug into the wiring on our CX-5, I have not had a need to do so. We usually keep our cars about 6-8 years so replacing sensors has not come into play. Being retired, I hope to keep this car longer. Our previous car was an Audi Q5 which practically fell apart (engine mounts and turbo failed) right after the warranty. It will be the last Audi we own. Our CX-5 is our 4th Mazda, all of them have been trouble free. My daughter had a 2016 CX-5 that she just traded to get a minivan for their growing family. Her CX-5 was trouble free as well.

 

[CrazyHippie]

It's gratifying you guys dove into why I'm reading 5 to 10 amps at the engine to chassis ground. The other question is why do these ground cables improve performance ever so slightly?

When I took these readings, the motor was running, HVC fan on high and headlights were on. It would have dropped about 50% if I had turned these two items off. The headlights and HVC fan motor are not attached to the engine but are part of the entire chassis ground circuit.

On my race car, we run a small nicad 16v battery. We have separate power and grounds to the ECU, TCU and coils, {16} 40,000 volt coils in this case, wired directly from the battery terminal. This avoids "noise" from electric motors like the fuel pump and radiator fan. The other devices, fuel pump, trans and rad fans and all the other sensors are powered from the battery and ground to the chassi.

The dirty circuit and clean circuits overlay each other where they attach to the battery terminals.

Maybe you will explain why this works. My theory, the battery absorbs the noise from the electric motors and the noise does not backfeed to the ECU, TCU or coils.

Do you see any current at all through the ground with the alternator unloaded? This makes me wonder how the alternator may contribute to the engine ground current.

 

[CrazyHippie]

Oh, and apologies to all for my propensity to be a smart-ass at times. Its my nature, I guess!

 

[Koko_Bandit]

I wonder if the engine block also acquires some sort of capacitive charge (due to all of the moving parts or some such) that interferes with the injectors, throttle body controls, etc., and when discharged to the frame, improves performance of the engine electrical devices. 5-10 amps of current through the ground wire is not trivial, and the engine surely must be electrically isolated by rubber mounts for the potential difference to develop? I'm not very smart with these things; Koko, any additional insight?

I have never heard or seen any capacitive issues other than stray capacitance that can be the result of how the ECM/TCM circuit board is designed. We had to be careful how signal traces were routed on the circuit board to not cause stray capacitance in circuits that were sensitive to capacitance and signal rise/fall times.

The rubber engine mounts do offer some electrical isolation of the engine block depending on the design of the mount. A rubber cushion sandwiched between an engine block and metal frame won't isolate the engine electrically if a bolt goes through the cushion and contacts the block and the frame. You do want a good connection between the block, chassis, and battery negative terminal. Wire has resistance and smaller wire has more resistance for a given length. That is why I said measuring voltage from the battery (-) to the block would be a good test of how good the block is grounded. The voltage drop in that ground path is voltage taken away from the injector, etc. that is being actuated.

 

[AL Cx5]

I have not dug into the wiring on our CX-5, I have not had a need to do so. We usually keep our cars about 6-8 years so replacing sensors has not come into play. Being retired, I hope to keep this car longer. Our previous car was an Audi Q5 which practically fell apart (engine mounts and turbo failed) right after the warranty. It will be the last Audi we own. Our CX-5 is our 4th Mazda, all of them have been trouble free. My daughter had a 2016 CX-5 that she just traded to get a minivan for their growing family. Her CX-5 was trouble free as well.

I started replacing engine management sensors at 7 to 8 years at 100k mi on our 09 Accord. I always hand Calculate FE per tank. I noticed better FE after replacing sensors such as O2 and map. Starts were better and so forth.

I have replaced all the sensors on my 06 ram. I picked up about 2 mpg changing out engine management sensors. I changed the other sensors so I didnt have to chase CEL codes, one after another. Stuff like wheel and transmission speed sensors.

On the Cummins forum, we started comparing resistance across old vs new and counterfeit sensors. Is this a valid test?

I have an efi managed drag race car. I learned that tuning with old, out of calibration sensors, the tune was effected when replacing with new sensors. On a new engine we start with a known quality and new sensors. No parts store or from a questionable source.