NJMP Lightning With Metro NY PCA Event Recap

Published: October 10, 2015

I ran my 1999 naturally aspirated Miata this event.

Tires

I used Maxxis RC-1 225/45-15 tires on 4th generation 15x9 6UL wheels. This is only the second day I had on these tires, the previous one being last Sunday at Palmer on my 2000 supercharged Miata.

The tires offered less grip than I expected. Because 2000 Miata has street suspension and alignment, it wore the outside edges of the tires more than the rest of them. Still, all tires had reasonable tread depth through the entire tread going into the Lightning event.

I found that the car struggled for grip in the lightbulb and had a hard time fitting into corner exits. I was experiencing understeer on most of the track with the exception of turn 3, oversteer in turn 3, and lightbulb offered both understeer and oversteer on the entry.

I started the car with the middle suspension stiffness front and rear and soon found myself softening high speed compression on the back to control oversteer in the lightbulb, which helped but was not a complete cure.

Toward the end of the day I softened all front shock settings in an experiment to see if the car would turn better. Softer front helped but again understeer remained in lightbulb. Interestingly, oversteer in turn 3 did not become significantly worse.

Tire temperatures were pretty wild. Early in the day I was looking at the edges being hotter than the center, suggesting an underinflated tire, with 48 psi of hot air pressure. As the tires felt greasy when they were hot, I figured the temperatures really reflected the tires sliding rather than gripping the pavement properly. I dropped hot pressures to 41.5 psi range toward the end of the day and that brought the center temperature closer to the edges, as well as created a semblance of a temperature gradient from inside to outside of each tire. Looking at tire wear I still wear both edges quicker than the center - suggesting I need more air pressure - but the car feels much better planted at 39-40 psi when I come on track than even at 44 psi after running several laps. I think 40-41 psi may be a good target hot pressure with these tires but I am doubtful they would wear evenly.

6UL 4th Generation Wheels

I found out that the 4th generation of 6UL wheels do not quite fit over V8 Roadsters 11.75" big brake kit in the front. I took a file to the calipers to create clearance but I am going to need to make a pass with a grinder on both sides of the car.

Suspension

After huge body roll and questionable corner entries at Palmer last weekend I was pleased to be in a Miata with Xidas. 1999 car is much flatter and I would say confidence inspiring in the corners, although somehow I do not think of it like that when I am driving it. A day in the 2000 car really highlights how awesome Xidas are.

Brakes

For this event I had Raybestos ST-43 front pads and PFC 08 rear pads. My previous front pad was Raybestos ST-42, I think the ST-43 fronts have too much initial bite for my car. The front felt easy to lock up and I was conservative with brake applications. I think I vastly prefer ST-42 on the front. The only issue with running ST-42 on the front is finding an appropriate rear pad as ST-42 is pretty low on friction coefficient list.

Power

I continued having the power issue I have had for a while. For this event I used 15w-50 oil and it did not seem to make a difference.

I was however able to add a data point to the symptoms: when the car lost power, if I lifted for 2-3 seconds and got back on the throttle the power would come back. Braking for 2-3 seconds would accomplish the same feat, however applying the brakes with the right foot on the throttle did not cure the power loss. My current theories are:

  • There is something sticking in an injector, or intake manifold etc. and air or fuel delivery gets clogged. Lifting moves the obstruction enough so that it gets temporarily out of the way.
  • The car is trying to run too lean and ECU is correcting that; however, sometimes ECU stops being able to do so and ends up pulling major timing, creating a power loss.
  • There is intermittent and massive brake drag somewhere. Brakes appear to be fine in the post-event inspection though.

Lap Times

I had many laps in 1:18 range. Even with the power issue I was able to run conistently in the 1:18s. I was looking at a 1:17 predictive lap time on a couple of laps but was unable to complete those laps at speed.

Communicator

I found out that one of the two headsets of the Nady communicator was virtually not transmitting sound from the microphone. I am having a pretty terrible luck with communicators lately. The plan is to find one of my other headsets from a Chatterbox and use it with the Nady intercom.