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

[CrazyHippie]

Friendly reminder for everyone to keep it friendly...

Indeed! There's a lot of knowledge here and now that I'm past my smart-assery, I'm learning a lot!

 

[N7turbo]

Ground wires don't go bad like sensors. They are not wear items.

 

[AL Cx5]

While browsing broadly to learn, I came across grounding kits that are meant to replace factory wires, for the same reasons you replaced functioning sensors. So far the only factory grounding wire that I found to be stand-alone, is the cylinder-to-chassis on the passenger side. It looks thin next to my 6 gauge battery cable. I assume thicker is better. Are there any other factory grounding wires that are easy to replace? Most others seem to diverge from bundle of wires. Thank you!

I was off topic and was hoping to learn more about our engine sensors. When do they start losing calibration before a CEL comes on from an automotive engineer.

Honestly, I have done more than a cursory look for OEM grounds. I see them but don't pay much attention to them. My goal was to do the tried and true extra grounding for better FE. The car had less than 100 miles on it when I installed the grounds, started this post. The community was more critical than interested. I moved on.

After grounding my attention went to improving handling, picking wheels and tires. The suspension install was more involved that other cars I've worked on but got it done.

Next was installing a slight performance tune and we enjoyed the car. We are finishing the next upgraded tune. It's almost a hot rod. Needs another 100 HP and it would be a handful. LOL Honestly, the new power level is just right. Drives like stock until we turn on Sport mode. Then it gets fairly aggressive. FE with this tune is even better than stock or the first tune. The first tune was more FE than stock too.

 

[GFrosty]

Do they age though?

Ground wires' copper can corrode (though high-grade wiring that's tinned and wrapped helps). The ring ends can corrode. But I wouldn't think any more so than existing ground wires. I'd call it a "for the life of the car" type part. Unless seeing severe salt-laden air (near coastlines) or if getting wet frequently (ie, hosing down the engine bay), perhaps.

My own 2016 CX-5 doesn't have but light surface discoloration (hardly enough to call it "corrosion) on "ring" ends here and there. Several of the various bolt and screw heads have far more.

 

[AL Cx5]

Ground wires' copper can corrode (though high-grade wiring that's tinned and wrapped helps). The ring ends can corrode. But I wouldn't think any more so than existing ground wires. I'd call it a "for the life of the car" type part. Unless seeing severe salt-laden air (near coastlines) or if getting wet frequently (ie, hosing down the engine bay), perhaps.

X2 on age. If you live in an area that puts chemicals on the roads in the winter, ground connectors can corrod.

Using experience gained from a 20 year old truck. Battery power and grounds corroded under the insulation. I'll always pay extra for an agm battery for this and other reasons.

Guys with older truck is who live up north have way more electrical issues as the grounds and wiring harness corroded. Hard starts, poor FE and electrical gremlins. We always recommend to newbies to clean the ground connectors or better yet replace with a HD set.

I make my ground cables from tinned, fine strand 4 gauge wire, marine grade with water proof shrink wrap and tinned connectors. These should last longer than the car. But audio wire and copper connectors will work fine. Others made the grounds from welding leads.

The finer the strands the better it will ground is my rule.

 

[N7turbo]

Stranded is for sissies. Just use solid wire.

 

[Nevada CX5]

The chassis steel and welds are not great conductors. Thick copper wire has much lower resistance. When connected to well chosen grounding points there can be a benefit.

A obvious grounding point on my 2018 can be found by removing the plastic cover on the engine revealing a factory grounding point near but not on the the throttle body.

 

[Jmaz]

This thread on grounding caught my interest and after reading a few pages at a time to the end, I decided to put all of that aside and just see what readings I got on a few cables on my (stock, untouched) 2014 as installed from the factory. Didn't loosen any bolts or clean any connections. Just started it up and hung on the clamp meter. Engine was still at high idle as this only took a few minutes.
The engine was cold ~40*F and high idle as normal. Headlights on low beam and blower fan on high (heat setting so no A/C compressor load.
1) Thin ground wire on passenger side from fender bracket to bracket on side of head --- 15A
2) Thinner, short cable from battery negative post to fender --- 25A
3) Battery negative cable ---- 27A

Don't know if this is of much significance to this discussion but thought to put it out there for any possibly enlightening comments. Haven't decided to add any additional heavier cables as that would be a warmer weather decision/project, but just may at some point remove the bolts and clean up the surfaces and attach some star washers and seal the connections for corrosion protection.

 

[Jmaz]

Something must be wrong here. After all the engine block *IS* already grounded (even if not perfectly). I cannot believe there are 5+amps flowing through these grounds.

See my results above.
ETA : just to make sure I didn't misread the decimal point location on any reading, I just now did a recheck. It's dark and colder. Same conditions as above. All respective readings higher this time.
1) 18.9A
2) 32.5A
3) 33.9A
Time for dinner. G'bye.

 

[Nevada CX5]

Here is the other obvious grounding point, where the 2 factory wires are attached.

 

[N7turbo]

I just learned how Mazda manages battery charging voltage.

It seems like a lot of engineering work for fuel economy when they could have just added more grounding cables.


Copilot:

Mazda absolutely does adjust charging voltage based on battery condition, but it does it in a very Mazda‑specific, fuel‑efficiency‑driven way that’s different from the “smart charging” systems used by some other brands.

Here’s the clear breakdown of how it works.

Mazda modulates charging voltage, but not by directly measuring battery SOC​

Mazda does not use a dedicated battery current sensor (like Honda, BMW, Ford, etc.).
There’s no Hall‑effect sensor on the negative terminal, and no IBS (Intelligent Battery Sensor).

Instead, Mazda uses a charging strategy controlled by the PCM that adjusts alternator output based on:

• Engine load
• Electrical load (lights, HVAC, defroster, etc.)
• Battery temperature
• Alternator temperature
• RPM
• Acceleration vs. deceleration
• Estimated battery condition (inferred, not directly measured)

So the car does vary charging voltage, but it’s based on system conditions, not a precise measurement of battery state of charge.

How Mazda’s charging system actually behaves​

Mazda’s alternator is ECU‑controlled and uses a “smart-ish” strategy:

1. Low charging voltage during normal cruising​

Typical: 13.4–13.8V

Mazda intentionally keeps voltage low to reduce parasitic drag on the engine and improve fuel economy.

This is why your CX‑5 often shows ~13.7V even with a brand‑new battery.

2. Higher voltage during cold starts or heavy electrical load​

Typical: 14.2–14.8V

You’ll see this when:

• The battery is cold
• The battery was recently discharged
• You’re idling with lots of accessories on
• The alternator is cool
• The PCM detects high electrical demand

3. Voltage spikes during deceleration​

Mazda uses a mild form of regenerative charging (not hybrid-level regen).

During decel or engine braking, the PCM increases alternator load because it’s “free” energy.

You may see:

• 14.5–14.8V during downhill or throttle‑off moments

4. Voltage reduction during acceleration​

To reduce engine load, Mazda drops alternator output when you’re accelerating.

This is why voltage dips into the 13.2–13.6V range during normal driving.

Does Mazda measure battery health directly?​

Not in the way AGM‑optimized systems do.

Mazda infers battery condition from:

• How quickly voltage rebounds after starting
• How much voltage sags under load
• Temperature inputs
• Alternator duty cycle history

This is a “soft” estimation, not a true SOC measurement.

What this means for AGM batteries​

Mazda’s system will charge an AGM perfectly safely, but:

• It may not fully charge an AGM to 100% SOC
• It may keep the AGM at 80–90% most of the time
• Occasional topping off with a smart charger is beneficial

This is why many Mazda owners run AGMs with no issues, but the battery doesn’t always reach its ideal absorption voltage.

In short​

Mazda does adjust charging voltage dynamically, but:

• It does not directly measure battery SOC
• It uses engine load, electrical load, and temperature to decide charging voltage
• It prioritizes fuel economy over perfect battery charging
• It’s compatible with AGM batteries, just not optimized for them

 

[jadmt]

nice find

 

[AL Cx5]

I just learned how Mazda manages battery charging voltage.

It seems like a lot of engineering work for fuel economy when they could have just added more grounding cables.


Copilot:

Mazda absolutely does adjust charging voltage based on battery condition, but it does it in a very Mazda‑specific, fuel‑efficiency‑driven way that’s different from the “smart charging” systems used by some other brands.

Here’s the clear breakdown of how it works.

Mazda modulates charging voltage, but not by directly measuring battery SOC​

Mazda does not use a dedicated battery current sensor (like Honda, BMW, Ford, etc.).
There’s no Hall‑effect sensor on the negative terminal, and no IBS (Intelligent Battery Sensor).

Instead, Mazda uses a charging strategy controlled by the PCM that adjusts alternator output based on:

• Engine load
• Electrical load (lights, HVAC, defroster, etc.)
• Battery temperature
• Alternator temperature
• RPM
• Acceleration vs. deceleration
• Estimated battery condition (inferred, not directly measured)

So the car does vary charging voltage, but it’s based on system conditions, not a precise measurement of battery state of charge.

How Mazda’s charging system actually behaves​

Mazda’s alternator is ECU‑controlled and uses a “smart-ish” strategy:

1. Low charging voltage during normal cruising​

Typical: 13.4–13.8V

Mazda intentionally keeps voltage low to reduce parasitic drag on the engine and improve fuel economy.

This is why your CX‑5 often shows ~13.7V even with a brand‑new battery.

2. Higher voltage during cold starts or heavy electrical load​

Typical: 14.2–14.8V

You’ll see this when:

• The battery is cold
• The battery was recently discharged
• You’re idling with lots of accessories on
• The alternator is cool
• The PCM detects high electrical demand

3. Voltage spikes during deceleration​

Mazda uses a mild form of regenerative charging (not hybrid-level regen).

During decel or engine braking, the PCM increases alternator load because it’s “free” energy.

You may see:

• 14.5–14.8V during downhill or throttle‑off moments

4. Voltage reduction during acceleration​

To reduce engine load, Mazda drops alternator output when you’re accelerating.

This is why voltage dips into the 13.2–13.6V range during normal driving.

Does Mazda measure battery health directly?​

Not in the way AGM‑optimized systems do.

Mazda infers battery condition from:

• How quickly voltage rebounds after starting
• How much voltage sags under load
• Temperature inputs
• Alternator duty cycle history

This is a “soft” estimation, not a true SOC measurement.

What this means for AGM batteries​

Mazda’s system will charge an AGM perfectly safely, but:

• It may not fully charge an AGM to 100% SOC
• It may keep the AGM at 80–90% most of the time
• Occasional topping off with a smart charger is beneficial

This is why many Mazda owners run AGMs with no issues, but the battery doesn’t always reach its ideal absorption voltage.

In short​

Mazda does adjust charging voltage dynamically, but:

• It does not directly measure battery SOC
• It uses engine load, electrical load, and temperature to decide charging voltage
• It prioritizes fuel economy over perfect battery charging
• It’s compatible with AGM batteries, just not optimized for them

Omg! What a convoluted charging system. I might have passed on a Mazda had I known


Has anyone calculated who much HP an alternator uses? Well I made a swipe at a dumb 20 year old alternator. AI rule of thumb 1 HP for every 23 to 24 amps.

 

[Koko_Bandit]

Omg! What a convoluted charging system. I might have passed on a Mazda had I known


Has anyone calculated who much HP an alternator uses? Well I made a swipe at a dumb 20 year old alternator. AI rule of thumb 1 HP for every 23 to 24 amps.

I would rather have Mazda's solution than the Nissan VCCS on my truck.

 

[Mazdiod2]

Mazda modulates charging voltage, but not by directly measuring battery SOC​

Mazda does not use a dedicated battery current sensor (like Honda, BMW, Ford, etc.).
There’s no Hall‑effect sensor on the negative terminal, and no IBS (Intelligent Battery Sensor).

Instead, Mazda uses a charging strategy controlled by the PCM that adjusts alternator output based on:

In short​

Mazda does adjust charging voltage dynamically, but:

• It does not directly measure battery SOC
• It uses engine load, electrical load, and temperature to decide charging voltage
• It prioritizes fuel economy over perfect battery charging
• It’s compatible with AGM batteries, just not optimized for them

This might be why keeping my battery on a battery tender helps so much, the battery is chronically undercharged.

 

[AL Cx5]

I would rather have Mazda's solution than the Nissan VCCS on my truck.

I'd rather walk than drive a Nissan. I know I'll get there....

 

[AL Cx5]

AI suggests a CX 5 alternator load per the following.

Estimate, 60 amps to run the system pretty maxed out or a 2.5 HP penalty. On a NA that would be 1.33% drain at 187 HP. So why did Mazda build such a complex system to save a fraction of a HP??

MAZDA could have improved a few other areas. Better grounding has picked up 6 to 8 HP from my testing. Or a better air filter box on the turbos, I haven't tested a NA air filter box. And so forth...

AI gibberish

Typical Amp Draw of Components
The precise total amperage can vary based on the specific year and trim level (e.g., LED vs. HID headlights, blower speed), but here are general estimates:

• Air Conditioning (A/C) Compressor Clutch: Draws about 2.5 to 5 amps. The blower motor will also draw power depending on its speed setting (2 to 30 amps).
• Headlights:
  • High Energy Discharge (HID): 7 to 8 amps once warm (12-14 amps initially).
  • LED: Less than 1 amp per bulb.
• Other Running Lights and Small Bulbs: Small incandescent bulbs draw around 0.3 to 0.4 amps each.
• Other Essential Systems: The engine control unit, fuel pump, electric power steering (2-40 amps), and other electronics are all running

 

[CrazyHippie]

Thanks for connecting the dots! Makes sense!

OK. I've finished installing two new ground wires on my 25 non-turbo CX-5. One 24-inch 4-gauge to replace the factory cylinder head ground wire on the passenger side, and one 3-ft to ground the throttle body on the drivers side to the battery ground body connect point. So far absolutely zero difference in the way that the car runs, but I'm much better grounded.

 

[AL Cx5]

OK. I've finished installing two new ground wires on my 25 non-turbo CX-5. One 24-inch 4-gauge to replace the factory cylinder head ground wire on the passenger side, and one 3-ft to ground the throttle body on the drivers side to the battery ground body connect point. So far absolutely zero difference in the way that the car runs, but I'm much better grounded.

I'm a bit confused why yours is not responding like mine.

Do you own and tested the ground location with a clamp on DC amp meter. This has been my tried and true method. As discussed, putting a load on the electrical system, lights, fan on high, will divert some amps through the grounds. It reads like you landed the grounds in the correct location. I gave some values in the above posts.

Clamp on meters prices have come way down. Mine serves as a multimeter, has ports for test wire/probes. It's a real handy item to have in you box.

Maybe post pictures of the locations and we can troubleshoot or confirm all is well?

What is your test method, butt dyno? I used an app on my phone that connects to a bluetooth obd2 output. I ran the same test course on the same day and logged engine load. Emailed the log to myself, put the results in a spreadsheet and graph the results. I saw a definite increase in efficacy. It was a commitment on my part but easy to do. Carried a 10 mm wrench and connected and disconnected the ground at the car.

My butt dyno cannot detect the increase because the CX 5 Turbo has so much low end torque it's hard to feel. A NA would be detectable. I could detect better shifts after grounding the transmission.

All of this is subtle. We are not adding 10 more pounds of boost or changing camshafts. It's real but subtle.

Glad you gave it a try!

 

[jadmt]

I'm a bit confused why yours is not responding like mine.

Do you own and tested the ground location with a clamp on DC amp meter. This has been my tried and true method. As discussed, putting a load on the electrical system, lights, fan on high, will divert some amps through the grounds. It reads like you landed the grounds in the correct location. I gave some values in the above posts.

Clamp on meters prices have come way down. Mine serves as a multimeter, has ports for test wire/probes. It's a real handy item to have in you box.

Maybe post pictures of the locations and we can troubleshoot or confirm all is well?

What is your test method, butt dyno? I used an app on my phone that connects to a bluetooth obd2 output. I ran the same test course on the same day and logged engine load. Emailed the log to myself, put the results in a spreadsheet and graph the results. I saw a definite increase in efficacy. It was a commitment on my part but easy to do. Carried a 10 mm wrench and connected and disconnected the ground at the car.

My butt dyno cannot detect the increase because the CX 5 Turbo has so much low end torque it's hard to feel. A NA would be detectable. I could detect better shifts after grounding the transmission.

All of this is subtle. We are not adding 10 more pounds of boost or changing camshafts. It's real but subtle.

Glad you gave it a try!

For most the butt dyno is what matters most. Not like cx5 drivers are racing for pink slips. . Im in 2000 miles into a 3000 road trip and have been running only non ethanol 91 octane and have gotten the worst mpg i have gotten in the last 44000 miles.