What have you done to your Miata today?

[chiefmg]

Maff, that is amazing. It's been fun following all your work on the car over the past years, and now getting to see you reap your reward.

Yesterday I swapped out the coils to see if I could cure the erratic steady-state operation. Went to the post office, after leaving there everything was warm so I proceeded to get on it. At approximately 4000 rpm I got a stutter and power was not there. The exhaust note had changed as well. I backed off the throttle then eased into it again but it didn't go away. With a sick feeling in my stomach I limped her home watching the gauges and listening for any signs of an increase in the problem. Parked her in the garage and left her sit overnight.

Since the last thing I did was change the coils, I put the other set back in. Checked the spark plugs as I went, and sure enough the #3 cylinder showed signs that it wasn't firing. Started her up and everything was back to normal. That was a big load off my mind. I've already ordered a new set of coils off Rock Auto so I can be sure that everything is up to snuff.

FYI, a Miata running on 3 cylinders sounds like a constipated Subaru.

 

[thejeans]

FYI, a Miata running on 3 cylinders sounds like a constipated Subaru.

i coulda told you that...

https://www.youtube.com/watch?v=bw-f9UsIQ80


mine was running on 3 cylinders when i first fired the car after the rebuild too. i had a couple connections missing, and now have a new ECU, ignition system, and injectors... i was about to say, the first thing id check would be wires, coils and plugs, while reading your post.

 

[chiefmg]

I'm just glad it wasn't anything worse. I'm running Toyota COPs so don't have wires to worry about.

 

[chiefmg]

New coils came in, I sanded down the sides so they would fit within the valley on the cam cover and installed them. Fired her up and even before she warmed up idling was lumpy. I put the other Toyota coils back in and she ran fine. Signed up for an autocross on Sunday, ran her around town on Saturday and was getting that intermittent weird change in the AFRs with the rough running. That shot the autocross plans in the ass. I didn't really mess with her over the last few days outside of thinking about possible causes and what I could do about them. Figured I should get a datalog so ran an errand tonight to do that. Unfortunately I didn't set it up properly beforehand so the data was not saved. On the plus side, I did buy Megalog Viewer so I can have a look at things when I do get a log and hopefully see what is going on.

 

[aMaff]

Damn, that's weird. The Toyouta COPs are typically pretty reliable. I know at least 2 top-tier SSM cars that are running them (and a F**K load of boost) without issues


Is it possible that the dwell time is set too high and they're overheating?

 

[chiefmg]

It was set a little high. Silly me, I thought when I sent it off for updating that my basic settings would be brought over but they were not (I've found a few other things that needed correcting too). I changed that to the settings deemed conventional last week (3.5 ms dwell for cranking, 2.1 ms nominal dwell w/0.7 ms spark duration) but was still getting the stumble/stutter/AFR dancing. The intermittent nature of the problem makes it hard to pinpoint.

 

[aMaff]

Couldn't hurt to drop another .5 ms or so and see if things improve just to test.

 

[chiefmg]

You're talking about the nominal settting?

 

[aMaff]

Yessir. I wouldn't start changing too many things in a row without testing in between.

 

[JamesCH]

Do you have a capacitor to help manage voltage at the coils? That solved a number of ignition symptoms on mine when I went COP.

I have an extra CAP and no Miata if you need one!

 

[chiefmg]

Thanks for the offer, but I'm using a Megasquirt so can set my dwell to whatever I want.

Took Maff's advice and tried reducing the nominal dwell setting for the coils down to 1.8 ms. Had a drive, did some tuning and then took a datalog. Haven't looked at the log yet but she ran pretty well. The AFR gauge was doing a little dancing but the car wasn't jerking as it was before. I may be onto something here...

Picked up my most recent eBay purchase from the post office today. Love it:

 

[chiefmg]

The other day after some research I changed the dwell battery correction table in Tuner Studio to match my COPs. Since that I have not had a repeat of the issue I was seeing with the AFR weirdness. I'm not ready to call it fixed just yet though. I did find out that you have to start a log from the menu at the top of the TS page. This will give you a file with a .msl extension and shows whatever parameters you have set to record. I was doing it through the Diagnostic and High Speed Logger tab at the top of the gauge panel, however this only records specific parameters in a .csv file. I'll be taking another log the next time I go out.

Since I was already on the garage floor this morning changing the oil in the CX-5, I decided to try changing out the exhaust hanger at the back of the mid-pipe for a urethane one I had lying around. First time I've used those, and damn are they hard to get into place. It didn't help that it was slightly shorter than the rubber one it replaced. I used WD-40 for lube and ended up having to use a large screwdriver in the slot in the middle of the hanger to lever it up enough to get it over the chassis mount. It is holding the rear of the mid-pipe very nicely now, no more chance of it moving around allowing contact with my rear subframe brace.

 

[Reitrof]

Swapped out the plugs. Old ones look good and show normal wear. PDR guy comes monday to take out the dents in the door.

 

[Reitrof]

Pulled the nose off and cleaned the air filter and retorqued the towing brackets.

 

[aMaff]

Started building some stuff for Front Splitter V2.0. No idea if I'm going to use this piece yet or not, but I needed something for mock-up / proof of concept.
But I think mostly I was just itching to get in the shop and make something

 

[aMaff]

The right way to do something the wrong way. "How do you mill a slot in a tube...only without a mill?"

 

[CTt3P5]

^^^^Not to shabby.

Another used GWR mid-pipe is for sale and I've been eyeing it up for a few days but couldn't pull the trigger. Glad I didn't as I just ordered this from GWR. My stock tank is a nice yellow hue and upon removing the cap, there appears to be stress marks within the filler neck. Replacing the tank was on my to-do-list so I figured it was a good investment to spend a little more for this vs. a new plastic one and the mid-pipe. What good is a mid-pipe if the tank fails me?

http://www.good-win-racing.com/Mazda-Performance-Part/61-2037.html

 

[chiefmg]

That's nice Jeff. I like the little level bullseye. I love my metal coolant reservoir, got it powdercoated so it matches the valve cover.

 

[Reitrof]

Nice Jeff. Finally got the dents out of the door my mother put there. PDR did a great job.

 

[CTt3P5]

Thanks guys. It is a beautiful piece. I got lucky and stumbled across the thread for it over on m.net. Have a feeling their initial stock wont last long.

A little too much bling for me so going to look into getting it powdetcoated and possibly the FSTB to match.

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