Interesting heat problems

[rbpeirce]

I was at BeaveRun last Friday and the temp was in the high 80s. I ran into two interesting problems.

First, I run Sumitomo tires. (These aren't good for the last second or so of lap time but they are about half the price of the tires that are, and they wear about the same.) I mention this because it could be a factor. Places where I normally have great grip with these tires were slippery at 5 mph slower speeds. I even bled the pressures down to normal levels after the first stint. That helped but the problem was still there. I don't know what effect heat has on track tires or other street tires, but it isn't helpful for these street tires.

There was a really bad storm moving in so I double stinted on the first outing after lunch so I could leave early. Instead of being out for 20 minutes I was out for 40. When I came in, the oil pressure at idle was down below the second bar. Normally it is at three or a little higher. That scared the hell out of me but after the car cooled down it reverted to normal. Pressures were okay on the track, but something was going on that I don't think was good.

On the plus side, last year I was getting a soft brake pedal late in the day. I was told it was probably brake pads but could be fluid. Well, I put in ATE this year and there were no problems whatsoever. I also had no problems at Mid-OH in April, but I don't get to that track very often so I couldn't draw any conclusions.

 

[L8apex32]

When I came in, the oil pressure at idle was down below the second bar. Normally it is at three or a little higher. That scared the hell out of me but after the car cooled down it reverted to normal. Pressures were okay on the track, but something was going on that I don't think was good.

Oil pressure at idle is supposed to be 0.7 kg/cm^2 or higher (less than 1 bar).
Oil pressure at 3k rpm is supposed to be 3 kg/cm^2 or higher (3 bars).

If you trust your oil pressure indicator, it sounds like your oil pressures are just fine. There are many threads on NSX Prime about oil pressure and associated causes and effects if you'd like to do further research.

 

[Ponyboy]

I don't know what effect heat has on track tires or other street tires, but it isn't helpful for these street tires.

Excessive heat will only add to the lack of grip in both street and track tires. If the tire (street or track) gets above the optimal heat range then you'll feel like the tires are "greasy" and the car may have some strange handling characteristics depending on each tire's temperature. You may have unexpected understeer and oversteer in various parts of any particular corner. I've found it's best to take the corners easier, brake much sooner, and generally be slower in any input - which gets the tire temps down to an acceptable level and back to predictable handling and braking. However, I've also found that the street and track tires I've tracked on, once they get overheated are much easier to overheat on future occasions.

 

[CL65 Captain]

Bob, if I remember correctly you are running stock pads. Stock pads are not up to the task for track work - they WILL FADE. I removed the dust shields and have Dali air deflectors for the front brakes and the OEM will still fade after a couple of laps. I was talking to a MI State Trooper (don't ask) and he told me that one of the few upgrades on their cars are better pads - requirement is 3 repeated stops from 90-0 with no fade. I am not sure the NSX OEM pads could even do this... Check into a track pad for the track and use your OEM pads for the street. Swapping them is an easy 30 min job that you can DIY pretty easily.

Mid Ohio isn't especially hard on brakes. You really only have to brake hard on the back straight and then they get a good lap to cool back down again. I switched from OEM to Cobalt Sport GTs and the difference is night and day when it comes to brake fade.

 

[rbpeirce]

Bob, if I remember correctly you are running stock pads. Stock pads are not up to the task for track work - they WILL FADE.

Maybe I don't use them hard enough. My pedal was getting soft last year at BeaveRun and ATE brake fluid seems to have solved the problem. I ran two back-to-back 20 minute stints there a couple Fridays ago with no brake problems.

I had heard brake fade was a problem with the earlier NSXs but pretty much went away when Honda went to the one inch bigger wheel. At any rate, I have never noticed anything beyond a little pdal softening after hard use. BeaveRun is harder on brakes than Mid-OH. it is only 1.6 miles and has two hard braking zones where you are coming down from about 125 to 40-60 with the ABS buzzing.