[JimMueller]

I took my daily driver to a little road race practice course today. Each lap was only a minute and I'd stay out there for only 5-10 minutes. The first session I just wanted to work on tire temps, then I let it cool down. I actually logged the second session and have some questions.

Water temp: I live in Florida, so I run 100% distilled water with maybe 1-2 bottles of water wetter. After 7 laps, I noticed the coolant temp was at the 3/4 mark so I brought the car in. The scan tool later revealed the temp had peaked at 244*. Isn't that a bit warm? Solutions?

Brakes: In the front I have standard C6 calipers, Trackbrackets, DTC-30 pads, new standard C6 rotors. In the rear I have Powerslot rotors and HPS pads. All stainless lines and using SRF fluid. While it didn't have a problem stopping, the pedal became easier to depress and started grabbing hard closer to the floor. I didn't like the feel of this, how do I remedy it?

The log also shows it was pulling 4* of timing on all WOT sections. I bet I have a knock sensor code (IMG:http://www.frrax.com/rrforum/style_emoticons/default/mad.gif)

[JimMueller]

I forgot to mention there seems to be a conflict in opinion on cooling solution between Dennis @ Ron Davis & Anthony @ LGM. When asked for the recommended coolant solution for their radiators, Dennis says it is OK to use green coolant, but said pure distilled water works better with a lubricant/anticorrosive additive. He said that although coolant raises the boiling point, that's not necessarily beneficial.

Anthony at LGM said race teams would prefer to use coolant on the track if they were allowed to do so because it works better, but they do not use coolant due to track rules. He said he's not had a problem with DexCool and it's fine to use.

I found a couple of thread which talk about the chemistry... but my lab partner got me through chemistry LOL
http://www.newton.dep.anl.gov/askasci/chem03/chem03987.htm
http://www.fordmuscleforums.com/all-ford-t...ter-better.html

How is raising the boiling point beneficial to a motor?

[Blainefab]

I forgot to mention there seems to be a conflict in opinion on cooling solution

How is raising the boiling point beneficial to a motor?

I think/hope that they all agree not to mix the yellow with green. I had a local customers car in that had a LS6 swapped into a LS1 WS6 - it had green coolant in it and a huge amount of brown sludge in the radiator and recirc tank and had been running hot. The orange and green, when mixed, combine to form a sludge that clogs the bottoms of the rad/tank and presumably the heater core and engine block. The sludge will inhibit thermal transfer.

All the coolant in a system is not at the temp that the gauge indicates - that is only one spot in the system. Other areas are hotter, others cooler. A boiling fluid loses most of its thermal transfer capacity, so if any part of the system starts boiling it will tend to raise the temp until more parts are boiling, and the resulting pressure rise pops the cap. The boiling point of a fluid is higher at higher pressure, so when the cap pops and lowers the system pressure, all of a sudden the whole mess starts boiling and you're parked.

So our goal is to prevent boiling from starting: the chemistry of coolant additives + water improves thermal transfer on a micro level, and the radiator pressure cap raises the boiling point of the entire system. Racing systems typically use a 20+ psi cap to operate the system at a higher pressure than a street car.

With a leak in the system, the pressure is lower, ergo the boiling point is lower, and you are operating closer to the point of thermal runaway.

This post has been edited by Blainefab: Apr 23 2011, 08:21 PM