Reading Spark Plugs While Tuning? 2024 CX-5 Turbo

[AL Cx5]

I'm working with DRT tuning our '24 CX 5 Turbo. I understand, DRT is an accomplished tuner. I have confidence in his tune for upping the power a bit for our DD CX-5.

I've been "reading" spark plugs on drag racing motors to confirm the O2 sensors AFR, timing, knock and heat range. We compare this to our O2 AFRs, timing and such. We have an EGT per cylinder to compare as well. We can tune each cylinder fuel and timing independently. We have picked up 20 to 30 HP at WOT changing heat range, gape along with fuel and timing. After melting holes in a new set of pistons, relying on O2 sensors, we confirm by reading plugs.

I'm considering putting a set of new plugs in the 2.5l T in a parking lot. Make a WOT 2nd through 3rd, cut the ignition, coast to the shoulder and pull the plugs. Install the originals. Then photograph the test plugs and read them in the shop. Then I'll have a base line for a healthy engine and confirm if AFR/Timing/Heat Range are happy with the tune. Four plugs seems like a piece of cake compared to changing 16 plugs in the race motor!

Each cylinder gets a different amount of air through the intake manifold. The exhaust back pressure is different on each "hole" as well. Injectors input fuel slight differently as well. On a DD tune, this should not be critical but could yield some info for the tuner.

I'd be interested to know if others have done this exercise and what they found. Each engine, fuel and spark plug combo have a different plug signature. I'd like to compare my test to another.

Thanks

https://honda-tech.com/forums/forced-induction-16/***-basics-reading-spark-plug***-3063102/

 

[skid00skid0]

In the '70's and '80's, I did it on two-strokes...

You won't be able to account for lean at part-throttle, or specific rev ranges, though.

 

[AL Cx5]

In the '70's and '80's, I did it on two-strokes...

You won't be able to account for lean at part-throttle, or specific rev ranges, though.

Agreed. It's a snap shot when the ignition is turned off. Partial throttle is less likely to melt a piston or have sever KR vs. Wot.

It can confirm if that cylinder is lean or rich and timing vs what is commanded.

This info works hand in glove to cofirm the logged values. And since we get an average afr it would be nice to have another reference.

 

[sm1ke]

I haven't done this, and as far as I can recall I haven't seen anyone else do this either (on these forums, at least). Maybe if you can provide a step-by-step procedure of what needs to be done, someone nearing their spark plug replacement interval can run through the exercise and post the results?

Make a WOT 2nd through 3rd, cut the ignition, coast to the shoulder and pull the plugs. Install the originals.

It sounds simple and straightforward enough, but are there any other factors to note? Use 91+ only? OEM plugs only? Etc.

 

[AL Cx5]

I haven't done this, and as far as I can recall I haven't seen anyone else do this either (on these forums, at least). Maybe if you can provide a step-by-step procedure of what needs to be done, someone nearing their spark plug replacement interval can run through the exercise and post the results?



It sounds simple and straightforward enough, but are there any other factors to note? Use 91+ only? OEM plugs only? Etc.

It's straight forward. I will use the fuel that I'm tuning to. The hardest part is dealing with a hot plug. I have pliers, gloves and rags for this step.

Another point of interest, as the engine management sensors age, they don't send the Ecu correct info. I've tuned around old sensors that was a waste of time and money.

As an example, as the O2 sensors age they read lean so the Ecu adds more fuel and it runs rich. We think all is well because we trust the electronics.

A $25 plug is a cheap way to cross check the above. Our O2 is reading an average of 4 cylinders. It doesn't give any indication of if it has the correct timing and plug heat range. Power maybe available with this simple test.

I change out engine management sensors on my gas burners at a 100K. It's like doing a major tune up. My gas mileage increases 2 MPG and it's way more fun to drive. There is a pay back to have fresh sensors.

Note: only buy Mazda or Denso/NTK from a trusted source. There are a lot of counterfeits floating around.

I run with the fuel the tuner and I agreed to use. In my case we tune with 93 octane.