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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Tuesday, June 03, 2014 5:43 AM
You should add some small Gurney flaps in front of your hood vents to see if that helps extract more air and improve temps. Also, we had tons of issues stacking the oil cooler and radiator. Both temps rose significantly over having them in separate locations. Is there any other place it can go?
Tuesday, June 03, 2014 9:49 AM
I think you should clarify that "225 water temp is getting toward the danger zone" only when hard driving is concerned. (I'm fairly certain the increased heat of the coolant and thus intake air temperatures would eventually cause some knock under load; the "dangerous" amounts of knock are audible to most people, though.)

But these higher coolant/intake air temperatures are good for fuel economy. In fact, I've read on this very site that:
"In the last decade, car manufacturers have improved engine emissions by increasing the engine operation temperature. 230 F is not uncommon on late model engines"

That being said, I think people should stop worrying about coolant temperature as much (as long as it isn't boiling, ie 275ºF or so with a 70/30 mixture of coolant/water and a 15psi radiator cap), and start worrying about changing the temperature of their intake air directly. Hot for fuel economy, cold for performance driving.
Tuesday, June 03, 2014 10:01 AM
Great article! Quick question, I would also like to monitor these coolant/oil/water temps as well. I would like to also add this to my track checklist.

How are you monitoring these numbers? Are you using something like a multi-function display?

Tuesday, June 03, 2014 10:13 AM
Convert the drain and fill plugs on the diff to accept -AN (probably NPT -> -AN, or weld something on) and run an external pump like we did for Project G20?
Clint Boisdeau
Clint Boisdeaulink
Tuesday, June 03, 2014 10:37 AM
@Rawkus, the vent angle on the Seibon hood is lower toward the front then the back to achieve the effect you're mentioning. Adding a gurney on top of that may help a bit, but its also my street car and i dont want it looking like that every day ;)

@monkius, Sorry i thought since the whole article showed on track testing, that my dialog was pertaining to hard driving. But i do agree with you that having a engine at a proper temperature during daily driving is good for efficency.

So you would track with water temps in the 275 F range? i know SOME fully built race engines can survive such temps, but considering my engine is 100% stock and its my daily driver, id rather keep my temps under that 230 F threshold on track. In regards to IAT's i will be doing another article soon that will cover that. Also, when i track i mix a significant amount of 100 octane with the 91 in my tank to help reduce the chances of detonation.

@Mr. Domo, we used the PLX Kiwi with Wifi capability in conjunction with the Torque App for Android for both this test and the single pass radiator testing in the past.

@Rockwood, yes id like to do something along those lines. I have a decent idea where i can fit all the related diff cooler parts while still being low profile.
Tuesday, June 03, 2014 1:13 PM
@Clint, you wuss, daily drivers need aero too :p

@Monkius, running high coolant temps is very common practice in high end racing engines, but a big exception is they also run the cooling systems under much higher pressures than an average daily-driver automotive engine. The big concerns are localized boiling due to pressure drops within engine passages. If you aren't running high enough overall pressures, you can risk overheating certain areas of the engine while running acceptable engine temperatures elsewhere. Also, most daily-driver engines aren't built with the idea of extra high pressures or with a water pump that can build the pressure anyway, so one must be aware of those limitations before trying crazy ideas.
Tuesday, June 03, 2014 2:41 PM
I don't see the 370 as being less robust than my Corvette which I've tracked with coolant in the 230s and oil in the 270s (WITH an oil cooler, it was 300+ before) without lifting. They just run hot, and people track them that way for years on end. Did I like it? No, but I wasn't about to miss some track time over it. The motor is no worse for the wear with 2 seasons of such use. 250 is not going to kill bearings. That said, ideally I would pursue lower coolant and oil temps, but to advertise certain death for these temps is subjective and innacurate IMO. I now race a Camaro whose coolant rarely exceeds 215 however the oil has been creeping up toward 275 (this is pre cooler, so may be a non-factor depending on how much heat the cooler takes out). I may look at adding another cooler this winter, but for now I'll just let the Redline oil do what I pay it to do.

This is not intended to take away from the measureable gains you've made, but it seems to me you're cheating yourself out of valuable hot laps by lifting too early. Add some transmission and differential cooling and go beat your car!
Tuesday, June 03, 2014 4:03 PM

Okay. Fair point that this is an article about track testing, lol... Mahbad.

I have no idea whether I was running 270º coolant temps when I was at that one track day five years ago, but I had about 3-1/2 hrs track time in 20-something minute bursts, and when I got off track, the coolant gauge was almost always nearly pegged max and the cooling fans were on. It was a rainy day though, so the temperatures were probably around the same as yours (my cooling system is stock). I had zero issues with knock or whatever, and my car/engine is still fine, 5 yrs later. So like I said, people should stop worrying so much about coolant temperatures varying by something small(ish) like 20 degrees.

On the subject of worrying, if you are not concerned about knock, then what is it that makes you think your engine won't "survive" those temperatures? Aluminum melts at 1200ºF, iron (cylinder liners) at 2800ºF. I don't think a few extra degrees of coolant temperature is going to compromise anything.

Rawkus, do you know what temperature this cooling system cavitation tends to occur at and/or can you provide a link? By all means, I am not condoning that people do crazy stuff like that, but freaking out over a few degrees seems like it's the opposite extreme, especially since modern (production) cars run those extra 20º hotter consistently, albeit under lower loads.
Tuesday, June 03, 2014 5:18 PM
So, the real question is.....How do you run for hours on end like an endurance car? Is the AC condenser the only thing stopping full cooling effect from occurring? Is the water pump insufficient? Is there a bottleneck elsewhere in the cooling system stopping efficient flow?
Tuesday, June 03, 2014 5:30 PM
Interesting data. I have been doing something similar with my truck at the track. With my stock radiator and 170 t stat my coolant temps hover around the 183-188 f mark and dont exceed that. Oil temps before I install my oil cooler were around 250-260 f mark. With my oil cooler I have yet to see them go over 240 f. These were with outside temps around the 80- 95 f. I would love to see how hot my transmission and rear end get and address those areas.
Clint Boisdeau
Clint Boisdeaulink
Tuesday, June 03, 2014 6:05 PM

Nissan VQ engine bearings specifically don't handle high heat well because of there construction, Kojima can confirm this. The bearings specifcally are less stout then the LS in your Corvette( im assuming its a LS powered Vette)

@Monkius, blame it on the fact i prefer the reliability on my cars that see track use to be more then i need rather then "just enough to survive", and the more you take components close to there thresholds, longevity dwindles over time. My 370 turned over 69k miles last week, i want it to hit over 100k without a catostrophic engine failure, so i play it on the safe side
Clint Boisdeau
Clint Boisdeaulink
Tuesday, June 03, 2014 6:06 PM
@Tom, im planning to do some bumper modifications to get more airflow to more areas of the radiator, oil cooler, and intakes. But that will be another article all together :D
Clint Boisdeau
Clint Boisdeaulink
Tuesday, June 03, 2014 6:08 PM

here is a quote from a past article from Mike Kojima regarding late Nissan engine bearings.

" The most oil temperature susceptible parts are the engines crank and rod bearings. The engines bearings are made of soft metals, such as aluminum, tin and zinc with other trace alloying agents such as indium which refines the metals grain for better mechanical properties. The reason why soft metals are used is that they offer good embedability. If hard contaminates are present in the engines oil such as casting sand, metallic particles, hard carbon bits and dirt, a soft bearing surface will allow the particles to become embedded into the surface of the bearing where the damage to the bearing and crankshaft can be limited. The contaminating particle will be soaked up by the soft bearing instead of being ground into the hard steel journal surface of the crank with damaging effect.

Soft metals can be used as engine bearings because under normal conditions, the crankshafts journals never touch the bearings surface. Since the liquid oil layer is not compressible, the crank rides on a pressurized hydrodynamic film of oil a few thousands of an inch thick that is maintained on the bearings surface by the engines oil pump. The oil pump must maintain pressure (this varies for as low as 5 psi at hot idle to more than 60 psi at higher rpm) and continually replenish the oil because the oil leaks out at the edges of the bearing and is flung out by the centrifugal pumping action of the rotating rod journals. This circulation is necessary because the shearing action of the oil in the boundary layer between the rotating crank journal and the static bearing surface creates heat and this heat must be dissipated. Most of the heat is removed by the oil as it passes though the interface between the bearing and crank.

The bearings, although soft still have to bear a heavy load because the incompressible liquid oil film transfers the forces acting upon the engines reciprocating parts to the bearings, thus the bearings have to withstand thousands of pounds of force even though direct contact does not happen. The best engine bearing have high embedability with a high load bearing capacity.

Usually everything works fine until a couple of things happen. In the case of modern late model engines, the green movement is to blame for part of the problem. In the last few years, Nissan has worked hard to make their cars green and more recyclable. In an engine traditionally one of the most toxic areas was the bearings. A few years ago, many Nissan bearings were made of trimetal construction using layers of lead, zinc and tin alloys of different percentages. This tri metal construction has been a mainstay of heavy duty bearing construction and composition for decades. The old Nissan bearings were very strong, heat resistant and durable. It’s a little known secret that old L-Series Nissan bearings are so strong and durable that many race engine builders use them, adapting them to other engines. The Infiniti IRL engine used in Indy cars used off the shelf L-Series bearings for this reason."

Wednesday, June 04, 2014 7:26 AM
I do remember that article, but are people reporting failures over this? I won't argue that it's bad in the long term, but I guess I would have just said screw it that day, press on, and try to fix it for the next event. Yes, my vette is an LS6 but the Camaro is an LT1, unopened, from a 96 vette. No idea what they were using for bearings back then, but I see cases of aggravated ignorance where racers run without oil coolers and without oil temp gauges and these guys just aren't blowing their stuff up. It kind of pisses me off to be honest because I know for a fact their oil is going past 300 every single time. I wouldn't be surprised if Nissan wasn't the only one changing up their bearing formula. I guess my point is that I hate to see people miss track time if they're lifting for temperatures that might not threaten the integrity of the engine. I'd have to look at that article again, because I know Mike called out specific temperatures in it. There's a lot to be learned by pushing the car for 30 minutes straight as opposed to 15. The car and driver start to deteriorate and being fast in that condition to me is key. I spend a lot of money to go to the track to not push myself and get every last possible minute of seat time. IMO, your biggest worry now is the diff, followed closely by the transmission.

Endurance cars put more effort into cooling and aren't dual purpose cars, so no AC condenser, larger holes in the hood, whatever it takes to keep temperatures in check. Half the fun of doing a dual purpose car is making a street car withstand track abuse while still retaining those street manners.
Clint Boisdeau
Clint Boisdeaulink
Wednesday, June 04, 2014 2:57 PM
there are 350s in the past that have seen track use that have had bearing related failures from high heat, and its verified from engineers and engine builders that the stock bearings are weak. I dont want to be the guy to find out in the 370 that i over extended the capabilites of the bearings. This wasnt my first event with the car, ive been combating the engine heat since i started tracking the car years ago, so i have a good amount of high heat run sessions on this motor. To say "screw it" and press on for something that isnt a competition event, on a daily driver street car, seems bold in my book.

Like i mentioned in the article, im going to do some revisions to the oil cooling and sort out a differential cooler. The trans should be fine, world challenge and grand am teams that field 370s dont run trans coolers to my knowledge. But i can verify that.
Wednesday, June 04, 2014 5:55 PM
I get caught up in the heat of the moment, I found myself banging gears harder and harder even in HPDE if I was on the chase so lifting has always been a difficult concept for me. I know on a 95 degree day on a particular 30 minute session my DIC gave me the message that my transmission had overheated, it was at 276*. I believe the 370s have similarly poor air circulation under the car. My diff will exceed 300* on a hot day too. Eventually those explode, the trans not so much. I may be likening the Z06 a little too much to the 370, but I know what poor circulation does under my car so I figure it's got to be a factor for you to an extent too. Now I've gotta dig up that article, I think it was the one all about the 370's new engine.
Clint Boisdeau
Clint Boisdeaulink
Wednesday, June 04, 2014 6:09 PM

but being that you have a Corvette, your trans and rear diff are all housed in the same transaxle correct? so doesnt your rear diff temps have a more direct effect on your transmission temps?

Mike Kojima
Mike Kojimalink
Thursday, June 05, 2014 8:48 AM
Yes Nissan bearings do get flaky with damage starting at around 260 degrees. Coolant temperature varies depending on where you measure it but on a Nissan if the coolant temp in the radiator output exceeds 230 degrees, it won't be running much longer. 230 on the radiator out is like 260 or more going in.

Last Corvette I drove on the track (C5) overheated with me driving 7/10's and went into limp mode in 3-4 laps.
Thursday, June 05, 2014 9:40 AM
AH. Thanks for clarifying that, Mike. That explains a lot.
Mike Kojima
Mike Kojimalink
Thursday, June 05, 2014 11:24 AM
Also in competing with LS engines, If we see 230 we have to do something fast or something bad will happen. Not sure where or how the Corvette measures temp OEM but the LS starts to mess up at about the same point the VQ does.
Clint Boisdeau
Clint Boisdeaulink
Thursday, June 05, 2014 12:16 PM
For the sake of more information, the VQ water temp sensor(which is where I was pulling the data via the PLX kiwi) is located after the water leaves the heads before returning to the upper radiator hose. So the water temp measurment is at peak heat. 230 water temp as far as my experience and info goes is rolling the head gasket failure dice.

on the other end, the Oil temp sensor picks up its temperature data AFTER the oil has gone through the oil cooler so its at its lowest point. I plan to get a aftermarket oil temp gauge/sender and place it in route before the oil cooler to know how hot the oil is coming out of the engine. So I think letting off at the temps im seeing now i feel is required for the safety of the engine.
Thursday, June 05, 2014 12:32 PM
Does the 370z have an oil-water cooler? If so, maybe try bypassing it?
Clint Boisdeau
Clint Boisdeaulink
Thursday, June 05, 2014 12:43 PM

09-11 370z's dont have a oil-water cooler, 12+ do. I have a 2010, so i dont have one.
Pablo Mazlumian
Pablo Mazlumianlink
Friday, June 06, 2014 2:51 PM
Clint, have you tried running higher % water and little coolant? When I lived in SoCal, I tracked a turbo E36 M3 numerous weekends without a hiccup. It had a large Fluidyne at the time, and no oil cooler, and lap after lap at WSIR or BW I'd see 190F Coolant and oil from the digital SPA gauges (and they'd read to the nearest degree of ambient when parked overnight). But no way my car would survive one night out in 25F either. I was using coolant as anti-corrosive only.
Perhaps if you're never seeing below 32F ambient in your area and parked outside overnight, running water with 1-2 bottles of Water Wetter or Royal Purple's stuff should help. I've also tried Earl's waterless coolant, which has like a 480F boiling point (to avoid those boiling hot pockets on the metal itself), but hadn't on track.
Not sure which oil you're using but as long as it's the good stuff, should be good from starting to break down at around 260F safely, if memory serves. I like it under that of course, and coolant no more than 220F. I never had to lift on the M3.
Oh I also had louvers as well as two small NACA ducts on the hood, though, ;). Really helps!
Clint Boisdeau
Clint Boisdeaulink
Friday, June 06, 2014 3:57 PM

Water mixture is 80% distilled 20% coolant, with a bottle of Redline Water wetter.

Did your E36 have a factory Oil to water cooling donut? i think they do, if so then that large Fluidyne(i like their radiators too, i used to have on on my turbo focus track car) is prolly doing a good amount of oil cooling as well as water.

Oil I was using was redline synthetic 5w40. the VQ37 is notorious for high oil temps by design, so they need a heafty amount of oil cooling even in stock and NA trim.
Tuesday, December 16, 2014 6:01 AM
Where is the water and oil temp sensors located on the 370?

I woildnt be concerned at 230 for water and 270 for oil if those measurements are pre-coolers (as they should be).
Clint Boisdeau
Clint Boisdeaulink
Wednesday, December 17, 2014 8:48 AM
@Stuntman, water temp sensor is pre-radiator, oil temp is post-cooler
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