Supergoat Garage

In today’s adventure I talk about swapping my spark plugs for a set of NGK Ruthenium ones, tackle fixing the touch screen and make my exhaust a little happier.

First: Making My Exhaust Happier.

I love my Cobalt axle-back exhaust system. It really does sound great, look great and possibly adds a horsepower or two. I never measured it so who knows, but general consensus says an aftermarket muffler on these cars is good for about 5-8HP depending on design. The higher gains being with a muffler delete, so I expect mine to be in the 5hp range. Of course, it could add 0 for all I know but I’m not worried about that. I just love how it sounds. Deep, smooth and no rasp or drone. However, I have noticed a vibration at idle. If I’m at a stop, clutch in and on the brakes, the cabin definitely vibrates a bit. This is a lightweight sports car and some of that is going just be part of the charm, but this felt a little too much even with PowerFlex diff inserts.

I didn’t really do much research on it, but I did recall reading a few posts regarding the Cobalt muffler and the OEM exhaust gasket. So went and searched for those again. I found that people were reporting that if you reuse the OEM gasket instead of using the one supplied by Cobalt, the exhaust is too rigid and does not allow for any flex which will cause more vibration and harshness. This, I imagine, is due to the OEM gasket being taller/thicker than the Cobalt one.

When I installed the muffler, I was having a hard time removing the OEM one so I left it on there not thinking anything of it as, even after 139k miles at the time, it was in good shape. So I chucked the Cobalt one in a drawer in my garage and carried on.

That brings me back to today. I dug it out and decided to swap it over just to see if it made a difference. But first I wanted to test the idea of it making the exhaust too rigid. Per Mazda, when tightened down the exhaust should have some flex at the joint allowing the exhaust to move a bit against the midpipe. Mine was solid. No give at all. Time to swap gaskets and see if it helps.

I unbolted the muffler and pushed the flange aside. As it turns out, the OEM one just needed a good pry with a flathead screwdriver and off it went. To be fair, I used a lot more force this time since I wasn’t trying to save it. I bolted it back together and the first thing I noticed was that joint now had some flex. The muffler could now move at the flange as designed. Maybe there was something to this after all.

All back together, I cranked the car up and let the idle settle and warm up some. The vibration will still present but slightly less. Result! I did not eliminate it, but I did make it better. I’ll take that.

Second: Replacing My Touch Screen.

A common issue on these cars pre-2024, is the center infotainment screen. The digitizer on it “spiderwebs” and gets artifacts in it in the corners as it internally separates. This not only looks bad but interferes with the touchscreen operation as well. In my case, my screen didn’t respond to touch at all.

The good news is, you don’t have to replace the whole screen when this happens, just the digitizer itself which is readily available on Amazon, eBay and other sites for around $30-$50. If you’re not familiar with that term, it’s the outer most screen that you physically touch. It’s more involved that just peeling it off and slapping the new one on, but it’s doable at home in about an hour. Sorry for the lack of pictures but once I started the repair, I forgot to stop and take pictures along the way.

First, I removed the screen and trim panel it sits on. This is pretty straight forward and there are plenty of guides on YouTube that will walk you through it. After I got the screen off, I separated it from the trim panel and then had to further remove it from the control unit it was bolted to.

I had to remove several screws and a few brackets until I got to a point where I could peel off the outside digitizer. The glass cracked and I had to scrape off a lot of excess adhesive but I finally was able to apply the new one. It was similar to applying a screen protector to a cell phone. Next step was to put everything back together. The new digitizer is glossy where the OEM one is matte. I thought this might introduce more glare and make it harder to see with the top down, but so far it has not made a difference and I actually prefer the glossy look.

Back together, the touch screen now works flawlessly, and it is spotless. Well worth the $40 I paid for it and the hour of my time.

Third: Ruthenium Spark Plugs

If you’re like I was a week ago, you probably have never heard of these. I definitely hadn’t. I was reading random threads on Miata.net and saw them mentioned, which then turned into an afternoon of googling. I decided for $40 for a pack of four, I’ll give them a try. So I visited my local auto part store and walked out with a pack, ready for install.

You may be wondering what the big deal is about Ruthenium plugs. Well, they advertise a smoother idle and better spark. A few people on Miata.net were singing their praises saying they could feel a difference. They were even referred to in a post as a legitimate, cheap performance upgrade. For $40, that seems like a low-risk part to try out.

Luckily it’s a quick job on these cars, I had the old ones out in under ten minutes. And when I say old, they have about 4k miles on them so not really all that old. But I wanted to give these new ones a try, still I saved the old ones just in case.

The new ones were in and I fired up the car. True to the forum, and NGKs marketing team, I did notice a smoother idle. It wasn’t Lexus smooth, but definitely smoother. I have no instrumentation or measurements to scientifically back that up, but I absolutely felt a better idle. And with the old plugs still being so fresh, it wasn’t just because of having new plugs. So that was a plus.

Next came the test drive. The first thing I noticed was the natural snappiness of this engine seemed to be lacking. Normally even the slightest tip-in of the throttle made this car want to surge ahead. I’m used to a very eager throttle response. With these new plugs that turned into a slight delay. The powerband felt smooth, but had more of a “rubber band” feel. Less snappy, but then you would feel it pull.

I was very confused by this. I would not think spark plugs would cause such a change in how the car drives. I pulled them and checked the gap again. It was within spec so I put them back in and decided to put some miles on them to see if the car needed to get used to them. Seemed unnecessary for a set of spark plugs but I did it anyway. After 300 miles, no improvement.

So unfortunately I pulled them out. I put the old iridiums back in and that car woke back up. The snappiness was back and the car felt great. So these did not work for me. Which I find very odd considering the feedback they were garnering online. But every car is different, and mine said no to these.

Don’t get me wrong, I’m not saying it was a massive difference. But I did notice it. The average consumer may not have even realized the difference but I know this car. I know it very well. The very small lag in response drove me crazy for those 300 miles. I wish they had made a positive improvement in driving feel and I’m jealous of those that say they have for them. But that’s cars for you.

This just about catches my blog up with the state of the Miata for right now. But there is more on the horizon. I have a trip to Miata’s at the Gap coming up in August and all the preparation of the car leading up to it so stay tuned!