Project 370Z – Heated Battle, Testing the CSF Triple Pass Radiator

Project 370Z – Heated Battle, Testing the CSF Triple Pass Radiator

by Clint Boisdeau

Last Year Project 370Z received some much needed cooling modifications thanks to CSF race radiators.  Their single pass/higher capacity radiator and AC condenser combo made for improved water cooling and retained the factory AC performance.  But as the year went on into the hotter months during summer,  water temperatures started to again fall victim to over heating.  The 370Z front end design only has one opening for radiator air flow.  So from the get go the top half of the radiator's surface area does not get fresh air.  On top of that, I have an external oil cooler taking up the left half of that single opening.  So even though the CSF radiator is a large improvement over the OE unit, there is still alot of factors working against it.  Top it off with 90 to 100+ degree summer track weather in SoCal, an engine known for high heat production and decently quick pace on track with a significant amount of time spent at wide open throttle, you have a recipe for overwhelming the cooling system.  There were a few things we tried before the CSF triple pass unit was implemented though.

Rewind back to September at Autoclub speedway where we tested the Stillen brake duct kit.  At the time project 370 was still on the stock, non vented hood and factory pressure radiator cap.  This day was extremely warm, mid 80s in the morning and 95 to 105 by noon.  Project 370 was running laps around 1 minute 56 seconds which is a decent time for a street car on the AutoClub “Roval” configuration.  Even with an extremely mild warm up lap to keep temps down and the heater blasting, one hot lap would get the water in the 215 range and the oil into the 230 range, then one more hot lap the car would already be at 225 water temp and 245 oil.  I was able to do a cool down lap to get about 10 degrees out of each fluid to be able to do one more hot lap.  But then that would get me back to 225 water and 245-250 oil temp range, which is not a happy place to be on a 370.  Nissan VQ engine bearings don't handle heat well past 250 oil temperature, and 225 water temp is getting toward the danger zone even for an all aluminum engine.

 

With the ambient temps very high, a stock hood with no venting whatsoever, and a track configuration that keeps you at wide open throttle for prolonged periods, the single pass CSF radiator was overwhelmed.  I could not imagine what the performance of the undersized OE radiator would have been under such conditions.

After that Autoclub Speedway event, I went to Buttonwillow Raceway Park in October.  80 to 90 degree ambient temps and lap times in the 2 minute flat per lap range which is also a quick time for a full weight/no aero street car.  This time I had a Seibon vented carbon fiber hood to give the engine heat extra routes to dissapate.  I also added a Nismo high pressure radiator cap from Nissan race shop at Fontana Nissan to help raise the boiling point a bit and reduce the chances of localized boiling in obscure sections of the water passages throughout the engine.  This got us to about 3 total hot laps before I hit the 225 water temp and 245 oil temp range.  An improvement for sure, but still barely 10 minutes of total time on track including the warm up lap.  With the size of the wheels/tires and the brakes on project 370Z, the car is capable of going much longer per session but is still limited by the engine cooling.

 

The Seibon TS vented carbon hood helped a significant amount of engine heat to escape. With the stock hood in place, the only route for the heat to go was out of the bottom of the car which is counter productive to heat's natural behavior to rise.

In late December I went back to Buttonwillow, ambient temps this time were 65 tops but sunny, so perfect track conditions.  With these temps I was able to get 5-6 hot laps in a row before hitting the 225 water and 245 oil temp range.  One cool down lap would get 10 degrees out of both fluids then i could go for another 2 in a row.  I had a great time that day because of the multiple hot laps per session, but it really came down to it being a cold day at the track which is a rarity in SoCal.  Also still hitting the 225 degree range was not desirable despite the fact it took more hot laps to get to that point.

 

Being able to run full tilt for a majority of the run sessions was extremely fun, but could only really be attributed to the fact that the ambient temperatures stayed low through out the whole day.  A true solution needed to be devised.

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