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Old 08-13-2015, 04:03 AM   #1
X25


 
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GM's comment on tire pressure for track (From first drive event back in 2014)



Fast forward to 3:39. They state 28 PSI cold is what GM engineers recommended, and asked to shoot for 32-34 PSI hot from the TPMS pressure display. This is 100% consistent with what most owners do anyway, but nice to know GM also recommended similar settings.
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Old 08-13-2015, 07:48 AM   #2
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ditto...these #s felt right to me
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Old 08-14-2015, 01:06 AM   #3
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That's my absolute target, and once you hit 35 you can feel the tires starting to feel a touch "greasy". Working with a tire guy -- who shows up at HPDE events with a full crew and pyrometers -- has pretty much backed that up. Like GM needed independent verification...
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Old 08-14-2015, 03:51 AM   #4
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That's my absolute target, and once you hit 35 you can feel the tires starting to feel a touch "greasy". Working with a tire guy -- who shows up at HPDE events with a full crew and pyrometers -- has pretty much backed that up. Like GM needed independent verification...
I got to try my Trofeo Rs only once at the track (next one is this upcoming Monday!), and I used too much pressure. I set it to 32 PSI at home late night, and when I got to the track, just dropped them by 4PSI (so I don't need to calculate the impact of driving to the track on temps). The problem is, it was pretty cold at night, so those cold temps were a bit too much.

The result? The car was a bit hard to turn in (borderline understeer). I am looking forward to try with real 28 PSI all around. I might even try 27/28 F/R to aid turn-in; we'll see.
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Old 08-14-2015, 05:26 PM   #5
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Just finished an event this past weekend 33-34 Hot was the sweet spot.
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Old 08-14-2015, 06:06 PM   #6
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35psi & up feels greasy...the Toyo Proxes I ran on the ZL1 felt great at 35-37psi
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Old 08-18-2015, 04:40 AM   #7
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Just did my second track day with Trofeo Rs, and I honestly had issues when I started at 28 PSI cold. From my build thread:

Quote:
Originally Posted by X25 View Post
Finally got to try my new oil cooler at Oregon Raceway Park today (yesterday)! Ironically, the ambient temp was 88 degrees F, which is what GM suggested they test their products at for track duty.

I started the track event late (at 11 AM) spent the first session testing out the oil cooler, temps, and tire pressures, and did not care for lap times. This turned out to be a big mistake since it was the only session I had where ambient temps were at or below 80 degrees F. During that session, the flaggers clocked me at 1:56.xx! Unfortunately, I did not take the lap times during that first session. The following (afternoon) sessions had ambient temps climbing within every hour (up to 90 degrees F), and I could not do that time again. Blame it on me (heat exhaustion), engine, or the tires overheating; I'm not sure which.

Here is the 1:57.1 lap I made at 87 degrees F:


I've also met a fellow Camaro Forum member, Tom. He does have a ZL1, and we even played in one of the sessions, driving lead-follow back and forth. I do have a footage of chasing him within safe distance, but I forgot to ask his permission to post, so I'll have to ask first

Temps:
  • Oil:
    • Long story short, with the new oil cooler, the oil temp stabilized in 270s! It has never stabilized before (I used to start cool down before seeing 300s).
    • Yes, it would be better if it stabilized around 250s, but if I will see 280 max regardless of how much I push the car even at 90 degrees F, I'm OK with that!
    • I should also note that Tom stated he did not see oil temps above 250 degrees F at the same track. He is usually up-shifting much earlier than redline, though, and it seems to make a huge impact on temps.
  • Coolant:
    • This is a bit bizarre. I checked out my logs, and I realized that at every session without exception, at either lap 3 or lap 4, I hit 228 degrees F. After that lap, the coolant backs down, and never gets past ~221 again.
    • What's happening at 228 degrees F? Does it start using reservoir? Does the engine management change the engine map? If you guys log the coolant temps, it would be nice if you check and see if you see such a behavior, too.
    • Anyhow, besides that odd lap, it never gets past 221s, so I think it looks pretty good.

Tires:
  • I've read in multiple places, and even heard of it in a car magazine video (where they mention GM recommends 28 PSI cold, 32-34 PSI HOT target for Trofeo Rs on Z/28s), but this did not work for me.
  • First off, how can you guys get the tires to only have 4-6 PSI increase? Of all the cars I've driven at the track, except the 2500 lbs Miata, none of them had an increase of <7 PSI.
  • No wonder, I quickly hit 35 PSI during the sessions, and it crept up to 37 PSI(!).
  • I eventually dropped the pressures to 26 PSI cold (by just bleeding another 2 PSI from whatever pressure I read from tires at the paddock), and it seemed to help.
  • When you check out Pirelli's track prep docs for Trofeo R, you'll see that Pirelli recommends only 2 bar operating pressure, which translates to about 29 PSI HOT. This would mean 22-24 PSI cold, which would be dangerously low for a heavy car like ours. GM recommends minimum 26 PSI for our cars with whatever tire, so I did not go below 26 PSI, but I think it's fair to say that 26 PSI should work better per Pirelli's recommendations, too, even though it's not low enough, either.
  • This was my second track day with these tires, and they are so far holding up fine (I still see the grooves :P). We'll see how much longer they can last.
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Old 08-18-2015, 10:31 AM   #8
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nice driving !!! nice video !!! more please
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Old 08-18-2015, 09:17 PM   #9
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Awesome video ! ....what does everybody use to get these video's and all the data on the video. Thanks
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Old 08-18-2015, 10:21 PM   #10
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Quote:
Originally Posted by backtotintops View Post
nice driving !!! nice video !!! more please
Quote:
Originally Posted by serviceguy View Post
Awesome video ! ....what does everybody use to get these video's and all the data on the video. Thanks
Thank you!

I do have a Bluetooth GPS transponder for high accuracy (XGPS160), an OBD II reader over Bluetooth (VGate), and use RaceChrono app to log it all during the track session. I use RaceRender Windows app to overlay it on the (GoPro) video.
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Old 08-19-2015, 08:47 AM   #11
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Quote:
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Thank you!

I do have a Bluetooth GPS transponder for high accuracy (XGPS160), an OBD II reader over Bluetooth (VGate), and use RaceChrono app to log it all during the track session. I use RaceRender Windows app to overlay it on the (GoPro) video.
That is a great video with nice data overlay. You are an excellent driver too. Not many cars are going to pass you!!
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Old 08-19-2015, 09:09 PM   #12
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That is a great video with nice data overlay. You are an excellent driver too. Not many cars are going to pass you!!
Thank you! These are great cars to drive at the track.
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