Analog is the red. Default LC-2 settings (500ms reporting I believe). I think the sampling rate looks lower on the digital in this graph because it was a 2nd gear pull vs a 4th gear pull.

 

It's been a while since I posted in here, but I took the car out to Road Atlanta last weekend. Since last post I've ditched the LC2 altogether and moved to an AEM x-series WBO2 wired to the megasquirt over CAN. Way more stable than the 0-5v analog output I never really trusted from the LC2.


Weather was 95 degrees with ~72 degree dew point. Hot and humid, as Atlanta usually is in the summer. Running wastegate pressure (~8.5psi, 220whp/200wtq on a dynojet), with my 10+ year old suspension and 3 year old BFG Rivals I managed a 1:47 and change. I've got no doubt with some real suspension and better tires I would be under 1:45. The car ran with no issues except for the need to manage heat. Coolant temps reached 220F after about 15 minutes of hard running, at which point I would cool down for about half a lap and temps would return to 205 or so. Staying in 4th for turns 3 and 5 seemed to help.

I've got the top and bottom of the radiator pretty well sealed but I still have to do the sides, and come up with some kind of ducting to the oil cooler (mounted in the FM steering rack location). Does anyone else run track days with their cooler in that location? Looking for some ideas. Also, what is the consensus of running an oil temp gauge in the drain plug slot until I have reason to remove the pan to drill another hole?

All in all, pretty happy with the car's performance. I was able to drive it back on the trailer, which is a success in my book.

 

A video of a couple of laps in which I cruise around and water temps get pretty high. Transient response is pretty great on this setup - check out the near-direct correlation between throttle and boost. Intercooler seems to be doing a good job too given the ambient conditions.

 

Finally got the car back out on the street again. Spent quite a few hours (and dollars) overhauling the suspension - wasn't pushing it at this track day, but my annual bonus was burning a hole in my pocket and my 170k bushings were quite sad. Out with the old business:


In with the new


XIDAS, 800/500, yadda yadda. Dual purpose alignment. Running the stock front bar with no rear bar until I find an RB front bar for cheap. I've had the chance to drive them around on some local (mostly city, poorly maintained) roads and let me say those of you who say "XIDAS on full soft are so comfy!" are full of ****. I had to stiffen them up about halfway before the bouncing stopped. Surprise! Higher spring rate requires more damping. You guys running around on full soft are morons. That said, they're still not what I'd call "comfortable" - my Mazda 3 with Koni FSD shocks on stock springs is comfortable. Tolerable is the right word. But, we buy these to go fast, not to be comfortable. Will have to take it to the track to confirm, but I'm not sure 800/500 is the correct rate for a car with no cage because it seems that, without one, the chassis isn't rigid enough to properly make use of rates that high. Anyone else run rates that high on a street-driven car with no cage?

 

My XIDA GS at 5.5" ride height are cadillac comfy on full soft, though the front tire hops if I try to push the car too hard.

If you turn it up a few notches, the wheel hop stops and the car is still tolerable over large bumps (but noticeably stiffer).

I would imagine that 800 front would probably hop even more at a given shock setting. But if you're setting them to full soft, you're not supposed to be driving fast. That's a setting for taking grandma to church.

 

I had same shocks & springs on my car with no cage. I'd agree- the ride was punishing on the street and possibly too stiff on the track (the tracks I ran didn't have the best asphalt). Hitting aprons on the track upset the car more because it was SO stiff. But the car cornered real fast. Wish I'd have gone 700/400 or even softer on the springs and run the car 1/2 inch higher.

 

I love watching you guys videos on track because it is often ones I've played in driving games. This is one of them. Possibly Forza learning track i think. Always loved the chicane to anger people for late braking

 

I've got door bars, frame rails, and a roll bar with 800/500 xidas. Chassis feels great.
I only run at +2-4 clicks from the softest on the street. There is no way I'd run +10-12 from soft, I'd bounce right off the road. Maybe my old, worn out bushings add enough compliance. The image broke so I can't see what bushings you put in, but I'll assume it's poly or SadFab Delrin.

 

How do you like the door bars? I'm considering those next. I already have the FM frame rail braces and I've welded the door/A pillar seam and the seam under the front fenders. I put in energy bushings. The bushings only really effect the higher-frequency impacts - think expansion joints, cracks in the road, etc. Those aren't what are so bad, it's the larger inputs like potholes that make the whole cowl shake. I'm wondering if a three-point strut tower/firewall brace might also help close that box in as well.
I spoke with an FIA cage designer this weekend and asked what the biggest bang-for-buck would be on an NA with a 4-point roll bar already and he recommended a petty bar. Too many options...

 

Door bars helped me significantly.

 

So much that I think I wasted money on the butterfly brace . It'll make seat mounting more tricky, but there should be plenty of space to the door and the seat.

 

They don't interfere with the seats in my experience. And yes, they are much more useful than butterfly braces.

 

Another great weekend at Road Atlanta - this time with Chin track days. The weekend was not without problems, but I had a great time nonetheless. It was my first weekend with Chin and they are definitely a top notch group! First things first, I bought a truck, so I'm no longer borrowing one from my generous friends.


This was also my first weekend on the new Xidas, and because it would be a waste to run fancy new suspension on tired old tires, a fresh set of BFG Rival S 1.5 tires. Weather this weekend was set to be in the 60's, so I picked up a "low boost" actuator to hopefully fix the overboost issues I've intermittently experienced in cold weather over the last couple years. With 4mm preload and no boost control I was seeing a solid 6.5-7psi. More than enough for me to have some fun with, and I was rewarded in my second session with a 1:44 lap, a solid 3 second improvement over the best I achieved last weekend. I would attribute most of that to the tires, but the car felt pretty stable with no snap tendencies, and some mild turn-in understeer. This was with the stock front sway bar and no rear bar. An upgraded front bar is probably in my future.
The car ran solidly for the majority of Saturday, with the exception of the power steering belt slipping off one rib. I'd feed it back on, and by the next session it'd be off a rib. In the last session on Saturday it launched the belt off completely, so I spent the rest of the weekend without power steering as the Miata gods intended. Neither the crank nor the p/s pulley had any visual runout, so I'm not sure what the root cause is... but I'll just take it as a sign that I should remove the P/S completely.
More seriously, on Sunday AM during my look over the car, I noticed a bit of an exhaust leak around the manifold to head connection. One of the nuts was loose, so I tightened and...



It wasn't the first time I'd found this nut loose, and it looks like the face of the manifold isn't quite flush where the nut is supposed to seat. So I'll have to either grind down that nub on the manifold, or come up with a spacer of some sort so the nut has something to bite on. New studs and nuts are on the way from Mazdaspeed. I still managed to put in about an hour and a half of track time on Sunday, including a successful check ride for Chin's red group. I still can't keep up with a well-driven 911 or Corvette, but I can give some of the Mustang and Camaro guys a hard time. Hopefully my gopro caught the 1:44 lap and I'll have it posted soon.

Next up, air management... Splitter, under tray, brake ducting, hood vents and likely a rear spoiler. Has anyone used a NACA duct from a splitter/undertray to feed brake ducts and/or an oil cooler?

 

I think you'd then need to put the rear bar back on. From Supermiata: "Disconnecting the rear sway bar on a lowered Miata allows the inside wheel in a turn to droop further...For track use, save yourself the headache and leave it on."

Paraphrasing from the aero thread, there's not much air under the splitter if its doing its job. The under splitter design only works if you've got fans pulling air. You should be pulling air from as close to the center of the bumper as possible. Mine are far out and don't do much.

 

Yeah, the plan would be to put the stock rear bar back on with an upgraded front bar. I didn't have the upgraded front bar in time for this event, and leaving the eibach rear bar I had on there before would make it super tail happy.

So I'll probably nix that idea for the brake ducts and run some from the front grill opening. For the oil cooler, I was thinking of something almost diffuser shaped to feed air up to it. Maybe a small ecu-controlled SPAL fan? Trying to think of ways to mount it without taking flow from the radiator or exceeding my fabrication skills...

 

Video from last weekend. My fastest lap was when it was spritzing rain - I must be a mad man, lol.

 

You can see the witness marks in your photos where the bolt head was interfering with the manifold:


It was the combination of that cantilever load on the bolt and the vibration of the manifold that lead to the crack. You can see the clamshell pattern where the bolt failed, that's a fatigue fracture.

Just grind the spot off the manifold where it was interfering and you should be good.

Chin does do awesome track days, they're my favorite. That's a fast time for RA!!

 

Yep, that's the conclusion Andrew and I came to as well. Pretty interesting failure. Going to be a pain to basically remove everything to get to it.

 

Well I still haven't fixed the exhaust (made some progress, but not much). I did however find this picture from the last track day, which I thought was pretty sweet.


Another thing.. My bumper was clean before that weekend. There's no black smoke when in boost, but it does shoot flames sometimes when I shift (I'm told). It very rarely pops. Any suggestions for reducing that?
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Shift less? Drive FLATOUT more.

I think there are some adjustments in TS if you are running a MS to get rid of that.