So, I bought a probe pyrometer, which I’ve now used to collect data at several events.

I’ve read Emilio’s “How to use a pyrometer” page on the Supermiata site.

I’ve been using that info to dial in my tire pressures, and things are working great so far, but I’ve gotten to the point where I’m not sure how to interpret the data, and I’m looking for advice from those in the know. The only threads I've found here have been about the pyrometer itself, not so much about interpreting the results, other than pointing to Emilio's excellent primer.

Car details:

’92 NA w/ VVT swap, naturally aspirated.
Xida 800/500, RB 54107 front bar, SM 14mm rear bar
Front camber -3.2 / zero toe
Rear camber -2.8
Nitto NT01, 225/45 on 15x9 6UL

The track for these particular readings is AZ Motorsports Park, a 2.3 mile CW track, much heavier on right turns. I’m currently running ~ 1.8 seconds off the NASA spec Miata lap record.

My procedure is to pull in from a session, exit the car and immediately take tire temps, followed by tire pressures. The following tire temps were taken yesterday and are *F. Air temp was ~92*F, tires were 29 psi hot.

LF ...................................RF
Out / Ctr / Ins...........Ins / Ctr / Out
125 / 126 / 123....... 125 / 126 / 123



LR ...................................RR
Out / Ctr / Ins........... Ins / Ctr / Out
133/ 134/ 129.......... 133 / 136/ 132

The higher temp in the center would seem to indicate I should continue to drop the tire pressure, but the small gradient is what I'm wondering about. With only a 1-2% gradient across the tire, should I just be happy? Anything else I'm missing?

Looking forward to hearing input from the experienced folks, and maybe this can be a good discussion thread for using a pyrometer for tuning?

 

Honestly the temp variations across each tire are money. You're grasping for straws at this point. Interested to hear others chime in as well though about the front to rear variation, but if you like the balance of the car no use in trying to mess with it further would be my opinion. I can tell you my readings are definitely not as good as yours lol.

 

Thanks for the reply. I was hoping to hear that, but being a noob to the pyro thing I wanted to hear it from someone who knows what they're doing, LOL. I spent a lot of time watching your lap record lap at AMP on YT the other night to work on my lines and braking points. It definitely helped, and I took ~ 1 sec out of my previous best.

I'm also interested in input on the F/R spread. The car tends more toward oversteer in steady and lift throttle, which helps the car rotate. I think the slightly higher temps in the rear are from my tendency to back it into the corners a bit. It has really good grip on the throttle, and I'm able to get on the gas early in most corners. I'm pretty happy with the balance, but I wouldn't mind a little more rear grip on lift/steady throttle, as I think it would allow me to turn in harder. Maybe I just need to get on the throttle even sooner...

Hopefully others will share their thoughts as well, and we can keep the discussion going.

 

Add camber at all 4 corners.

 

Following with interest, as I'm about to start using a pyro as well.

I was going to say that the camber seems less than other track car setups I've seen. Hotter temps in the centre does seem to indicate that the pressures could be dropped a bit more. Have you tried other pressures?

How are the tires wearing?

Assuming you are happy with the car balance?

 

^^^ This could be an option to try out and see what happens, but I would also take tire wear into consideration. If wear is even, I wouldn't touch it for an HPDE environment. If outside edges wear a little faster, maybe throw a tiny bit of camber at it.

 

Thanks to all for the responses.

Andrew, is there something in the pyro readings I posted that suggests a need for more camber with the NT01s? I'm getting very even tire wear currently. I would think I would need more tire (Toyo RR, R7) to make use of more camber, but I'm not ready to make that jump while just doing HPDE.

As for pressures, I started high, and have worked down to 29 psi hot. Next time out, I'll keep going down to see what happens, but I haven't gone lower than 29 hot as of yet. Pyro readings kept getting better as I was decreasing pressure, up to what I posted above. The small gradient is what prompted me to ask for others' opinions.

I'm not unhappy with the car's balance currently, though as I noted above a little more rear grip on lift and trailing throttle might be beneficial.

 

For a CW track, the left side is more loaded so you should use that to judge camber vs. temps. On the left side, you'll see that the outer temp is still higher than the inner. Increasing camber will even it.

But, I must say, your temps looks really good to me -- you are approaching the noise range in the deltas. I'm not surprised that you have good wear with these readings. Anything you do from here would be the finest of tuning.

 

Thanks. This was really the clarification I was looking for. The info on Supermiata gives examples of much larger deltas across the tire, and I wanted to be sure I wasn't interpreting things incorrectly.

 

my understanding has been that you want the insides approx 10/15* warmer than the outsides, with even delta between out/center, and center/in.

 

Balancing tire wear against pure pace.

A 5-10* step between readings, inner hotter, is usually faster. You'll see the steps because the middle/outside are in free air on their way to the pits and cool faster.
You'll see it first on the less-loaded side of the car, pertaining to clockwise/counter track direction.

 

 

Temperatures seem extremely low for a 92 degree day at a fast pace? Hot pit would give much better idea.
What bushings? I found I needed much less camber with delrin.

"The ideal operating temperature for the NT-01, according to Nitto, is about 200 degrees Fahrenheit for maximum adhesion to the tarmac"

http://www.superstreetonline.com/how...rnia-speedway/

 

Excellent article! Thank you for posting that.

I had the desired temperature gradient backwards in my head, so increasing camber makes sense now. Duh.

My 'pit crew' availability depends on when my wife goes out for her next session...

In this case temps were taken in the pit as soon as I could get out of the car. Not ideal, but better than nothing. The way the sessions are flagged at this track, there's only about 3 corners before the pit exit. I do try to keep corner speed up if I'm not pulling off from a hot lap.

To my knowledge it still has the original bushings... SadFab bushing kit is the next project.

Thanks again for all the responses, it's been very helpful!

 

Honestly going to a smaller rear bar may alleviate some of your lift-oversteer issue. I rarely see people without aero going to something stiffer than the stock rear bar.

 

x2, my tires are 120 when the car isnt moving on a hot day like that. Something's up.

 

Hot lap temp is all that really matters. If you're getting anything else, that's fine, but don't treat it as usable/comparable data. If it's end of session stuff after a cooldown lap (even at 8/10ths) it's useless.