Slightly Glowing Series II Cat
 

Noticed a very faint glow of the cat only from the drivers side and the glow was coming from above the sensor - illuminating the left side very faintly.

I noticed a unique smell on the way home tonight - a mixture of unburnt gas and likely premix (Lucas JASO FD) at 0.4 oz./gal. Air temp was in the mid 30s °F. We had just been idling on the highway for about 10 min in heavy stop and go traffic. Once on the interchange on-ramp between two highways I drove it all the way home in the 5-8K rpm range.

Then I checked and noticed that very faint glow of the cat on the top.

2K miles ago (I now have 44K miles on my 2010 GT) I replaced the ignition coils, wires, and plugs all with OEM (coils were C part numbered from MazMart). I also reset the ESS and cleaned it while in replacing the ignition. I've been religious on oil changes (1000-1500K OCI) and N3R1 filter changes. I run 93 RON fuel always from reputable sources.

Should I be worried?

I'm not getting CEL/MILs and notice no performance related issue sother than typical winter MPG loss? (I do warm up the car and it blinks off the first red warm up light just as I take off in the morning - about 2 min idle time).

Thought S2 owners?

Yes a glowing cat is a bad cat. Test it (google, use a laser thermometer) or get it tested right away.

Yes, my cat glows after a hard drive (2009 sport model). I do not have any performance loss or CEL, but I am still planning to switch to BHR midpipe. How many miles on your cat??

A bad cat COULD destroy your engine if it gets badly clogged.

Also, by premixing you are accelerating the clogging of your cat significantly. I do not premix my S2, though I will start once I have switched to midipe.

Get rid of the cat asap. In our experiences the stock cats ALWAYS fail. Its not a matter of if, but when. When the cat clogs it can overheat the motor and ruin it. We usually go with the Magnaflow direct replacement. The are significantly cheaper than the stock cat, flow better, and run cooler. We've installed them on cars and 5 years later+ they are still functioning. We usually try to keep them in stock.

Now tonight I recreated the drive and conditions and NO GLOWING CAT whatsoever. I did measure the actual metal surface of the cat from front to back and will post the temperatures of the actual cat skin temps (not the shroud that surrounds it). Net no temperature differential from inlet to outlet.

Again I'm not having an power loss, no starting issues, just replaced all ignition components 2K ago including cleaning the ESS and MAF (with MAF cleaner). No symptoms other than last night I noticed a smell of sweet unburnt gas and organics (no sulfur) and looked at the cat last night (slight glow from on top of cat above the O2 sensor.

Just over 45000 miles on the original cat on my S2

The quick and dirty test is to remove the front 3 bolts and pull the cat down for inspection. The white honeycomb should be clean and clear. To investigate further, you can remove the rear 2 bolts and take the cat out. Shove a bright flashlight up its butt and inspect the front for light. If you see light all around, it is good.

The better test is a flow and sniffer test at the dealership. If it fails and is still under emissions warranty (8 years / 80K miles), they will replace it free.

If you go aftermarket, whatever cat you buy needs to be rated for 1500F mean and 1800F peak temps, or it will fail quickly. Most cats are rated for 1200F mean temps.

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SD - thanks for these tips. I will do the inspection after I rule out fuel/air mismanagement. This "one day it has a faint glow above the O2 sensor" then "next drives it has no glow" seems like fuel/air or compression (input to the cat issues). I will also re-clean the MAF and re-clean and reset the ESS this weekend once I drain the 3-4 gal of premixed fuel in the tank and put 100% hi-test fuel with no premix added.

I only have 45K miles on the S2 and 2K ago recently installed OEM: C-part coils, NGK plugs, and OEM wires. I did check that everything is nice and torqued and snug on the engine and bedded on the coils.

Thanks 9K - I didn't catch this one (from the awesome Eric the Car Guy of Cincinnati)

I have learned a few things watching his vids.

So have I - He really has taken the time to help even a novice understand and work through a repair. Not many people take this time. He has been very well compensated for his effort and rightly so.

This is track data, so it is not wholly applicable, but look at the left side of the graph. My EGT is over 1100F while just sitting in grid. My first lap is taken lazily as I let my oil reach operating temp and put some heat into my brakes and tires. My second lap isn't driven much harder. Even when taking it easy, the temp shoots right past 1700F. The inch or so on the right side of the graph is my cool-down lap and return to paddock. Still much hotter than what Magnaflow specifies as the operating temp of their replacement cats.

The graph represents about 12 laps, including warm-up and cool-down laps.

https://cimg9.ibsrv.net/gimg/www.rx8...8347de5a39.png

This has me curious, so next time I drive the car to work, which is about 21 miles of mostly city driving, I will try to remember to run my data logger and post what EGTs are recorded during normal driving.

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Thanks SD - I can't figure out why my OBD2 reader doesn't list EGT as a monitor. All I have listed is O2 Sensor voltage (which I'm sure I can convert to temperature).

Torque has it in the extended PIDs section.

I remember doing the street driving experiment a couple years ago, in which I logged the RX-8 on the drive to and from work one day, then did my Tacoma the next day. The difference was very dramatic--almost double, IIRC. I can't find the data now.

So is that Torque Pro's extended features?

I think my limitation is my ELM327 reader https://www.amazon.com/gp/product/B0...90773217bde8a2. It only captures these:

ELM327 Functions:
1.Read diagnostic trouble codes, both generic and manufacturer-specific, and display their meaning (over 3000 generic code definitions in the database).
2.Clear trouble codes and turn off the MIL (“Check Engine” light)
3.Display current sensor data, including:
4.Engine RPM
5.Calculated Load Value
6.Coolant Temperature
7.Fuel System Status
8.Vehicle Speed
9.Short Term Fuel Trim
10.Long Term Fuel Trim
11.Intake Manifold Pressure
12.Timing Advance
13. Intake Air Temperature
14.Air Flow Rate
15.Absolute Throttle Position
16.Oxygen sensor voltages/associated short term fuel trims
17. Fuel System status
18.Fuel Pressure

Yep. get Torque with extended PID's and a good adapter, I use the OBlink MX (something like that). It was pricey but worth it.

The saga is just starting...car is at the dealer and the cat was being overworked. They are claiming that the (full) tank of Shell V-Nitro power 93 octane gas is really (tested as) E85 and that the fuel management is dumping fuel to maintain engine run state.

What's in the tank is 93 Shell with no premix. I'm working with the Shell station to investigate.

If it was straight E85, the car would not run.

I know - I think they're pulling my leg or they think something else is causing the cat to work overtime. They've confirmed that the ignition system is very healthy and that there are no other fuel/air issues. Short of a "going but not gone" O2 sensor, I cannot fathom anyhting other than the cat has to be replaced under warranty and they're looking for an out.

They now say that the fuel sample taken at the engine is milky (sample taken but I've not seen it). What would cause this?

Could be a few things. Bad fuel from a gas station tank is pretty rare these days due to the amount of filters required and the inspections done.

Sounds like dealer bullshit to me.

Car fixed accd to dealer - net was that bad gas was causing the cat to run out of parameters (hot). Details:
(1) bad gas sample taken at engine (milky) - will have it analyzed
(2) tank emptied and refilled with dealer confimred "good" gas
(3) cat temp issues went away after driving and idling
(4) rotary tech said running PREMIUM fuel in Winter may be one cause and that I should only run premium in Summer and operate on 87 RON all other times
(5) out $USD 349

I'll have them add all this documentation on the statement I pick up and will post for you to review.

Only run premium in the Summer? What a truck load of BS. I would demand to see that gas so you can take a sample to the gas station for reimbursement if that is true. But I suspect it's dealer bullshit.

https://cimg2.ibsrv.net/gimg/www.rx8...6dd02b9eaf.jpg
Here's the actual Mazda dealer invoice and the gas sample that took some time to materialize. Help me with their logic:
(1) PREMIUM fuel should not be used (owners manual states premium is required)
(2) car was found to be running 15% lean (wouldn't excessive alcohol in fuel cause it to run rich)
(3) gas sample took 11 minutes to show up after I asked (hmm...and no test data available)
(4) gas sample appears to have a large volume of water in bottom phase (how did the car run?)
invoice from today's dealer visit

https://cimg3.ibsrv.net/gimg/www.rx8...918c25d114.jpg

bad gas from my running 2010 GT

Yes, more E85 would lean out the mixture. It does look the way water looks in fuel though. But who knows with some tech trying to prove a BS theory.

The reason I took the car to the dealer was to confirm issues with the cat (glowing on top). Now I'll have to invest in a better OBD-II reader to monitor a bunch of functions and hope the cat throws a code before the dealer spends even more money on a new cat and engine under warranty.

Would premix cause any of this from a fuel standpoint or taxing the stock cat more?

I'm not sure about premix... and I rail the shit out of my 8 once it gets warm... annnnnnd as far as premium fuel goes we max out at 91 out here in good ol' Colorado... sooo I don't know what to tell you aside from horse shit. Granted, I'm no longer running the stock cat and I premix.

correct E85 is leaner but the sensor would then way over enrich the fuel to air to get stoichiometric right. The dealer said that this so-called E85 leaned the mixture.

I was doing that yesterday. Just cruising around I was seeing mid 1300F to Mid 1400F EGT temps. One quick pull in second to about 6500RPM in second and the temps shot to low 1600F. My 09 R3 has 90K miles now, I have a RB DR midpipe that just waiting to go on when I get time to do it.

OP, spot on advise from 9K, as always.
He will always look out for you and others, just don't muck him around.

I drove my 8 to work this morning and logged the trip in Torque. Ambient temp was 48F. Shift points were around 5000 RPM. The trip was 20.5 miles of city driving, with many stop lights, and top speeds reaching 55mph.

As you can see, just daily driving an 8 produces EGTs high enough to kill most cats, assuming Magnaflow's operating temp of 1200F is to be believed.

https://cimg7.ibsrv.net/gimg/www.rx8...191ba283df.png

Yeah the ECU would try and correct but it would take a lot of E85 to really lean it out since it is so rich on the factory map. And like I said, with straight E85 or even a large quantity of it, it would not run or would sputter and stall and just run like shit.

I really have to monitor my E85 mixture because "E85" can be anywhere from E50 to E85 depending on the station and when mine is off, the car runs like shit since it is tuned for it. I use the same station test it fairly often.

What are the requirements for inlet and outlet gas temps and other specifications for the RX8 cat to say whether a cat is failing or has failed?

A quick update that still has me questioning the dealer's diagnosis. I called and talked over the issues with the Service Manager and the techician who worked on the car - net I'm still suspecious that this $99 diagnosis was run up for extra cash to meet the "weekly quota" on income.

PREMIUM - dealer still stands behind that PREMIUM gas in an RX-8 is overkill especially in Winter (lie)

BAD GAS - they mentioned that they used water to determine that the gas was very high in ethanol near E-85. Milky organic (gas) phase indicated to them that the gas was high in ethanol content. No quantitative measures no record of the ST/LT fuel trims nor exhaust temperatures were recorded in their system. In my line of work, no data is just that.

I will invest in better tech to monitor the health of the catalyst and the car and do it more myself. I'm not going back to that Mazda dealer, even for an oil change. They made $250 extra on me and lost a client. PM me if you want to know what dealer this was (or look closer at the invoice).

Yeah man, it's BS. They are just so used to taking advantage of people who don't know shit.

As for the temp range, I am not sure but if the difference is significant, then I would say the cat is bad from what I have seen because it just means that the heat is staying in the cat.

BTW rotarheads - mazda has an email address to address complaints: MazdaCustomerExperience@mazdausa.com

I just filled out my Mazda survey honestly and told them I wold have been better off purchasing a OBD-II reader and tablet than to spend the $349 to hav ethe car returned to me with "fresh" gas and the cat still "slightly" glowing on occasion.

Just install a race pipe keep your cat, re-install cat for emissions if you have to in your area. Dont get a resonated mid pipe or anything with packing, let your 8 breathe for once. Buy an extra read o2 sensor for when you do emissions. Dont keep the cat on.. my 8 blew a hole right through the center of the packing about the size of my fist..

I finally had a chance to monitor the cat temps today on my 14 mile - 45 min commute home. Here's the catalyst temps and coolant temps from ~ 30 % stop and go traffic and the rest spirited highway miles. See any issues in the Series II (S2) coolant temps or cat tempos on this average day?
https://cimg1.ibsrv.net/gimg/www.rx8...a0adbc39d6.png

IAT = 75 °F, 40% rh

https://cimg2.ibsrv.net/gimg/www.rx8...4cf2484657.png

IAT = 75 °F, 40% rh

I am guessing the stop and go was towards the end, around where you've spent $61,500 on your car :D: ?

Cat temps seem pretty typical to me.

Jastreb: Yes the last portion of the trip was stop and go traffic. I need to fix the macro that imports this specific data into my stats software (SAS) so that the date/time doesn't appear like I drive a Land Rover.

^ LOL at wannawankel thinking that owning an RX-8 is less expensive than owning a Land Rover.

Those temps look normal to me.

Thanks - just getting the car and monitoring ready for my trip to DGRR

Have you done a visual inspection on the cat yet?

I suspect those "cat temps" are more like exhaust gas temps, and so may not indicate a bad cat.

Also, are your STFT and LTFT's reasonable now?

Short Term and Long Term Fuel trims
 

I have and on occasion I can still see a faint glow coming from the top of the cat. I see this glow indirectly along the "ceiling" of the underbody. ST and LTFT are
https://cimg7.ibsrv.net/gimg/www.rx8...2c7571d2bb.jpg