I have a dummy temp gauge so I'll relay some dummy information, but you'll get the point. I run a stock G35 on R compounds and am seeing significantly higher coolant temps this year than last. The G temp gauge has unlabeled graduations from bottom to 3/4 scale, with a blank gap between 3/4 and "H". The car normally runs dead center (180F?) and used to climb 2-3 notches during a session on my old tires. This year, I watch the needle climb during each session until I'm halfway into the void between 3/4 & H. As soon as I let up for a cooldown lap it drops right back to normal. I know that the new wider, stickier tires generate more friction, but this is rediculous. I'm afraid if ambient gets much over 90 I'll overheat. Is anyone else having this issue?

I tried 1 bottle of Redline WaterWetter - no noticable difference (maybe a little slower ramp up), and am considering a refill of D.I. water and WaterWetter based on Redline's claims of 20+ deg. reduction in operating temps;

http://www.redlineoil.com/whitePaper/17.pdf

Any suggestions from those who've been there are welcome!

Thanks,

Tim

 

I don’t have any cooling issues with my Z. We had 95+ temperatures last week-end at MidOhio and the car never when higher than halfway up the temp gage.

Are you using more of the higher rpm than last year? Did you change anything on the body work? Are all underbody panels still there? Do you have a road kill on your rad? Is it clean? I’m assuming the water level is good?

As long as the needle doesn’t go all the way up, you’ll be fine. Engine damage is not likely, but it might shorten your track sessions.

How about that NISMO thermostat?

 

Interesting. Same nut holding the wheel, same bodywork and such, rad is clean and coolant level is fine. I had a coolant flush & fill done last fall, maybe it left an air bubble? Another change since last year is we are now using ethanol blended gas vs. MTBE here in the Northeast, maybe higher combustion temps? The thermostat seems to be responding fine on warmup and cooldown but I may change it just to knock it off the list. Still confused.

 

I'd think you may still have air in the system. try bleeding some more. it usually takes at least three heat and bleed cycles to get all the air out.

 

Thanks Arizzee.

I bet you're on target but I'm going to throw a little extra effort in anyway. This is a potential show stopper so I'm going to throw a 155 F thermostat (per Kolia's suggestion), a higher pressure rad cap and my own bleed session at it. Since nobody else seems to be having this issue I've got to hope that the flush & fill wasn't done right last fall, and the combination of this stuff will take care of it.

 

Putting in a lower temp thermostat will not do anything. Thermostats have no effect on coolant temp once the temp exceeds the thermostat preset temp. None.

Time to look into an aftermarket radiator.

 

That's what I thought too, but I waffled based on thermodynamic ignorance. I'm really hoping the bleed will do it, and using the thermostat for a little insurance. They're pitching a slower ramp up in temp. and I'm willing to give it shot for the above stated reasons. Here's the blurb;

"This NISMO thermostat helps to circulate chilled water to the radiator quickly in order to reduce power loss during circuit driving & sports driving by water temperature rise. In addition, the NISMO Low Temperature Thermostat also influences the engine control system by opening the valve at 68 deg C as compared to factory valve opening set at 76 deg C. As a result of opening the valve much earlier, the water temperature rise time is decreased, and the engine is protected."

If this doesn't work I'll certainly heed your advice. Nobody else seems to be having this problem so I'll hope for the best and try the cheapie fix first. Any recommendations on a true bolt in replacement if things go wrong?

 

If I'm not mistaken, only Power Enterprises makes a rad for the G35. All the 350Z rads need to have the top mounting prongs cut, moved, and re-welded. Given that, I would get the PE rad. Its a good piece. Koyo, Greddy and Stillen are quality parts as well, but required the above mentioned mod to fit a G.

 

Here's my story and conditions. I had a bit of overheating problems over the summer. I did a weekend at SOW in June and had no problems. I July, i had an oil cooler, 255 tires and a license plate. I was overheating after my 2nd session out each day. It would return to normal after a cooldown lap. The temperature was also over 100 degrees. The air coming out the oil cooler and into the radiator was much hotter, the tires had more grip and i was able to stay on the throttle much longer than oem tires and the license plate blocked just a bit of air coming in.

If i overheat again in a few weeks, i'll let you know. If it still is overheating, i will need to get another radiator.

 

Funny that you & I are the only ones to have this problem. I'm in an auto G and have done a couple of things to help:
1. Bypassed the tranny cooler loop in the radiator and installed a separate cooler.
2. NISMO thermostat & rad cap.

Getting the trans fluid loop out of the rad has bought me some more time on track (3-4 laps) before pulling off to cool down. The radiator hasn't burped since installing the cap, so those 2 changes helped. The thermostat change is invisible and a waste of money in my opinion. My next step was going to be an oil cooler, but since you have one and am still experiencing temp issues I guess the PE radiator is the next logical step.

I think this is related to track layout and driving style too. My "home" track is NHIS; short, lumpy and brutish. Not real fast and not real flowing (fits my style just fine though...). For contrast, I went to Watkins Glen for a 2 day event last month - very fast and flowing - no temp issues at all, but ambient was in the 60's.

Do you have an oil temp gauge? If so, what kind of drop did you see after adding the cooler? Thanks for the info and keep us posted on your progress.

 

A three core aluminum radiator ought to take good care of you. It not only holds more coolant mix, but is more efficient in exchange than the itty bitty stock radiator. I run a Koyo that has been modified as noted above, but any of the good quality aluminum racing radiators are worthy of consideration.

I do not think the nismo thermostat is the answer at all, and would not do it, as there are negative issues with running too cool.

The 1.3bar cap is a good idea.

Redline water wetter is good stuff. It works better with straight water, but going into the winter months you want the antifreeze protection, so you will have to run it with coolant/antifreeze mixture to protect your car.

You can also put in a lower oil pan spacer and pick up another quart of oil capacity.

A bigger oil cooler (Setrab for example) would be a very good idea, and also add yet more oil capacity.

Running a synthetic oil is highly recommended as well if you are pushing occasionally higher temps.

Coating the lower oil pan with a heat dispersant is not a bad idea either, to improve heat transfer or exchange. Some after market pans have finned case designs to increase the surface area exposed to air for a still better heat exchange (ARC for example).

By adding these modest features you should be able to tolerate much higher demands than your stock set up.

If you get into FI you have some real temperature issues, and I am having no heat issues with these types of mods, (and a few others) to attack the thermal dragon. The two big issues with high performance driving that are ever present are heat, and weight. You might consider looking into the strongest and lightest wheels that you can justify buying for your bigger tires, as those will improve both responsiveness of the car and reduce unsprung weight and strain.

 

Guys - After doing 11 track day events this year I have come to a few conclusions about coolant temps:

Your temps have a lot to do with the track you are on. For example - I ran Roebling road in 97 F heat and my temps where fine, yet I went to Sebring in 90F and I was on the verge of overheating. Since Sebring has some increadible long straight aways and the corners allow you to get on the power early there.

Water Wetter works! For summer run water wetter and water, in winter run Water wetter with coolant!

A screen in front of your radiator can cut down the air flow by more than you think!

 

Eagle1, i got most of those mods.

Setrab oil cooler
oil pan spacer
1.3 bar radiator cap
synthetic oil (10w30) going to use 10w40 this time

all i see left to do is
radiator
vented hood
water wetter

I did not have an oil temp gauge before or after i installed the oil cooler. it could be that i was in the higher revs for much longer than before. the tires gripped more and i was able to stay on the throttle longer. mostly deciding to stay at the top of 2nd gear or middle of 3rd. if problems are still there, i'm going to get a koyo radiator and vented hood. i also ran with my heater on to vent some of the engine heat. it worked for a while but if you set it to full blast on the hottest setting, the climate control system changes it from venting outside air to recirculating inside air.

 

The vented hood is a good mod; I certainly see a lot of heat signature coming out of the VIS one I have. The nose scoop at the high pressure area in front helps to draw lots of cool air in across the block and the gill slits release the hot air towards the A pillars (not directly onto the windshield). A small negative is that for daily driving, with the window down, if you put your arm on the window sill you toast your elbow....you really feel the heat! So it does some good.

The track matters as one of our comrades above noted. Streets of Willow is a short, twisty track with little opportunity to get a lot of air flow, relative to how much you are hard on throttle. There is the straight section up the hill after the pits, the straight after the bowl, with the chicane...and that is about it. Plus you have quite a bit of slow speed, uphill pulling, so you are really building temps on that circuit. Just across the way at the big track of Willow Springs you have a full race circuit with only nine turns.......and some of the highest velocities of any race circuit. The front straight delivers 140+ mph top speed and first turn of 80mph, the carousel Turn 2 is 90+, the back straight coming off the hill from Turn 6 is 135mph and the Turns 8-9 are 100+ (be very respectful of the diminishing radius Turn 9 track out limit leading to that front straight, as two wheels off at 100+ is potentially lethal)...............you probably could have run that in 100F air temps and been just fine, while SOW would boil you.

I think the high capacity aluminum radiator really is the way to go. If you take out the stock unit and set it down next to a Koyo or equivalent...you will be shocked at how small and narrow the stock unit is.....about a third the size. I did a multiple thread series of posts on the build of my car, and in this section there is a picture of the two radiators side by side.
http://forums.freshalloy.com/showthr...=142536&page=3

 

If you're driving the big track correctly, your top speed in turn 8 should be higher then your top speed at the end of the front straight. It took me a while to get to the point in my driving where my foot was flat to the floor all the way from the apex of 5 to the entrance of 9.

 

A cheap and easy mod that you can do in less that 5 min that will achieve the same results is to remove all the seal in the back of the hood. It comes off really easy and you can put it back on in less than 5 min if you want after track. If that is not enough air - you can add washers to the hood hinge to lift the back of it more.

 

just finished a weekend at SOW and the temperature never even got above 1/2. weather was cold saturday, rained a little bit with a strong wind coming into the front of the car down the back straight. it must've been the 108 degree weather this summer that had me overheating.

 

went out in march to horse thief mile and started to overheat again at about mid day. my car was pegged in the upper rpm ranges all day. im resorting to a 3 row from koyo. any other sugguestions? would i need a theromstat too?

 

Carroll Smith's book Prepare to Win goes into several chapters about how to design a proper cooling system. Read his book and then decided how best to improve your cooling before buying a larger radiator. You may find a really cheap way to cool the car before you shell out big money for a radiator!

 

+1

the removal of the rear weather stripping (near the windsheild) should help alot with underhood temps.

ALSO remember that a good underbody / undertray (i.e. your stock one) will actually help pull air out from your radiator due to airflow pressures under the car.

(cheap sensor for water temp: shameless plug: techtom CDX-100. plug straight into your obd2 port and reads RPM/speed/water temp/intake inlet temp/ignition timing/battery voltage... all for less than $150ish)