SBC_and_a_stick

Scope of work
Does this aftermarket radiator work better than the stock unit? If so, how much better?

This is a presentation of several lab results employing the C&R Denso high efficiency core in my C7 Z06 M7. This core is a straight replacement of the main radiator. C&R constructs 90% of the NASCAR radiators. This core is the same exact core technology used in the infield and short course NASCAR vehicles. The thickness of the radiator is the same or negligibly thicker than the OEM. The trick is in the fin spacing and construction. In any case, I bought it because I believe C&R has the high overhead needed to construct a quality piece and because I thought the DENSO core is the best on the market for roadcourse use. MSRP $1,300, compare this to the $225 cost for replacing the stock unit.

Background
The main radiator cools the water and the water in turn cools the oil through a liquid to liquid exchanger. That is, the C7 Z06 only has a single heat exchanger for both oil and coolant for the engine. The C&R piece replaces it.

I've overheated this car several times in the summer last year so I'm trying to approach cooling with the most effective options available from GM or otherwise.

The car overheats at 262* coolant, but gives early warning and shuts off access to A/C at 256*. Coolant overheats before oil, I never got an oil overheat although oil did go over 300* at times.

Pictures of the install:









Install detail

Fit and finish is perfect. There was no difficulty in installing the radiator. I had it done at a dealership so that it is done right and all the bubbles are taken out of the system with the right equipment. Water/coolant ratio was kept at 80/20 just like I had done with the OEM core. The car never sits in freezing temperatures so a coolant heavy mixture is not needed to ensure proper operation.

Testing conditions
Testing track: Thunderhill 3 mile
Driver: self
Time: January 24th stock; February 13th C&R
Transmission: manual; I optimize shifts for speed not for cooling; I use 3rd and 4th gears on this track
GPS receiver refresh rate is 10hz
Coolant temperature is read through Harry's laptimer using a high refresh rate OBDII reader and placed into a spreadsheet for the analysis
I record the max sustained coolant temperature in every lap; I ignore very short time span spikes as they may be recording errors
I drive in advanced group and I am competitive running middle of the advanced pack or slightly above depending on the organizing group.
Notes:
(1) The track configuration was w/bypass on January 24th and w/o bypass with C&R so the C&R laps are supposed to be 2 seconds slower; the rest of the track is the same
(2) The ambient temps were higher during C&R testing day, but the ambient temperatures do vary within each day so a proper comparison can be made
(3) The stock radiator runs are shorter at ~16 minutes compared to the C&R runs which are ~25 minutes. Speed SF runs shorter sessions than Hooked on Driving. You pay more with HOD but you get more track run time. Compare accordingly.

Preview of results
I do not find a large improvement from using the C&R radiator. I interpret this result as either (a) more data is needed for a proper comparison or (b) the radiator location has to little airflow for any radiator change to make a meaningful impact or (c) the radiator is no better than the stock unit. I'm leaning towards (b) being the most likely scenario.

Here are two graphs where I think I can display 99% of the relevant information in one go. This way we can visualize a whole bunch of data in the simplest way to digest. I can do a whole bunch more of data tossing around so hang tight.

On the Y axis (vertical) you can read the coolant maximum temperature in any given lap. On the X axis (horizontal) you can read run time, basically driving at speed on the track for up to 25 minutes. I propose we compare only sessions where the ambient temperature is roughly equivalent. As you can see from the C&R day, the ambient temperature makes a huge difference. I also propose we compare at similar run times since you can see the car runs the coolant higher and higher until it stabilizes. That said we still have to assume my driving is consistent. Since I'm the same guy driving within a 1 month period, basically back to back, I don't think there is much variance. However, I'm not as consistent as some of the best advanced drivers.








Disclaimer
I will do the best I can to interpret the results and analyze the data. Feel free to correct me if needed, ask for analysis, or to interpret the data in your own way. I do not work for C&R or have any interest in the company. I bought this radiator just like anyone else would. No skin in the game, except to cool my car better and prevent overheating.

SBC_and_a_stick

Detailed discussion of the two graphs
The best sessions to compare are 2,3,4 for stock radiator and 1 for C&R as all four are 49* to 53* ambient and about 15 minutes of run time. As you can tell in all four sessions the temperatures are very similar. Stock the car ran 212* to 214* in the three sessions max. With the C&R it ran 218* max. I don't see an improvement.

Aside from the sessions where the ambient temperatures are similar, we have a few laps where the C&R is tested in higher temps. In session #4 the coolant max temperature was a rather high 232*. The car feels significantly slower once the coolant passes over 230* threshold, and we know from the timing tables that there is considerable pull from the ECU at that threshold and beyond. Top speeds on the straight dropped. Since the ambient temp was only 69* I'd say 232* coolant is pretty hot. This is yet a second indicator that the car needs more than just a radiator upgrade. I think the car will still overheat in 90* or more ambient.

Let's see the four relevant plots in the same window on the same scale:



The C&R ramps up the heat about as fast or faster than OEM. This is even true comparing it with the OEM run at the bottom right where the ambient is higher. I don't see a difference.

One caveat is that ambient temps for the stock core were quite low, so there are not that many datapoints to compare.

Another data point
I drove on the same track (Thunderhill 3 mile with bypass) last year on March 21st with the stock radiator:https://www.corvetteforum.com/forums...lant-temp.html. I reported there 244* coolant in 73* ( I looked up an hourly historical ambient). Unfortunately, I did not collect the OBDII data every lap back then. I just watched the display for top temps. The C&R managed 232* in 69* ambient. I'd say once again I don't see a huge improvement given that the ambient temps were lower with the C&R by 4* a 12* improvement isn't much. The water mixture was also 40/60 back then so the stock radiator had a worst mixture to boot.

0D3PE

We actually use the same 27mm Denso Motorsport cores in all of our HX products and custom one off builds, with that said it is defiantly a much better cooling core, it is thinner and allows higher air speeds through it along with a much higher fin density to further aid. I will agree with you on the air flow part, we ran into the same issues on the C6 platform, as of right now we will be testing a bolt on part next Wednesday at the local road course to see if it helps with the air flow of the radiator itself along with our oil cooler upgrade.

Dave
Owner/Engineering

*Edit - I just realized you are running a larger core (36mm?), did they offer you the 27mm (which is the actual core used in Nascar?)

Snorman

Can you clarify what happened in "C&R, Session 1"? I'm guessing that perhaps it was a black flag or other incident, but appears that ECT is following the same pattern of the other three sessions. Also, ECT appears to peak, then stabilize or even slightly drop throughout the remainder of the session. By or before the ~16:00 mark (end of session with stock radiator) the C&R ECT seems to have already plateaued. I also don't think we can keep coolant temps below ~220* regardless of what radiator (or supplemental radiator) is used.
To me this might represent an improvement if coolant temps stabilize in the ~230* range with the C&R. My opinion is that these ECT's are acceptable on-track and will typically be accompanied by ~280-290* EOT's. It will be nice to see more data in higher ambient temps and thanks for posting this. Would also have been nice to see what happened to stock coolant temps past ~16:00 or with the higher ambient C&R sessions. Are you planning on running the same track soon with the GM supplemental radiator?

I know you've had performance degradation and stated that at 230* ECT the car "feels significantly slower". I'm not sure if that's unique to your car or if it's just a "feel" you get on track. However, note the following from a session at Sebring a few weeks ago (ambient temps in the low-mid 70's:

(lap 6 T16 exit around slower moving car decreased vmax)
Thinking that I might have realized a higher vmax as a result of simply lifting later into T17, I did screen grabs at every vmax point on the PDR video. They were achieved by substantially the same point, so the car made consistent power throughout the session. Other full sessions show the same thing, but that weekend I did have a power loss issue that I'm starting to relate to fuel level.

I'm very close to pulling the trigger on an AM radiator. In fact, I bought a first gen Dewitts last year within a month or two of their release (got a great deal from Summit) but never installed it as it was an impulse purchase with better options to follow.
S.

fleming23

Snorman, to clarify - what modifications have been made to your car? Is it 100% stock? Just want to know apples to apples here.

Snorman

Yes. The only "mod" is an oil cooler shield we fabricated out of sheet aluminum.
S.

SBC_and_a_stick

Dave, this is the standard issue C&R core, 27mm.

It's good to hear you guys believe in this unit too and that your explanation from what I'm seeing is the same. There really is not much to gain from changing the main radiator on this car. I had this suspicion. My initial reaction was along the same lines, just had to see the data to be sure.

Session 1 was indeed a flag. I believe I forgot to turn the recording back on when entering the track for the second time or Harry's Laptimer failed to record further in some way. Therefore, we only see the first 15 minutes of that run.

Indeed there is a plateau after about 16 minutes. That is, unless you are the type of driver that just drives faster and faster. It could also be a function of the ambient temperature. I haven't mapped what it does in higher ambients.

I do think we can keep coolant under 220* but it has to be a very cold day. Look at the stock data, it never gets above 215* in the low 50*s ambient. In the last session they kicked us off the road with a checkered flag 8 minutes in for absolutely no reason. I was so annoyed. Speed SF is cheapest but you also get shafted quite regularly on run time.

To me as well it would seem great to see the temperatures always stabilize around 230* coolant. But, I don't believe that to be true. First, Thunderhill 3 miles is the highest speed track around here imo, probably close to Laguna Seca. However, Sonoma and Thunderhill 2 mile especially are absolutely brutal on the cooling system. So I'd take this as a best case scenario. Sonoma is all concrete, intricate low speed turns, and has a fairly short straightway if you can even call it straight. Thunderhill 2 mile is a 110mph max track, tiniest with little airflow and stupid hot in the summer. Second, I do think the ambient degrees matter more than anything. 69* is cool around here, most summer days are high 90*s on this track.

What I'm going to do next is to predict when it will overheat based on ambient temps. I agree I would like to collect more data but there won't be any more with just the C&R. I'm installing the second core from GM tomorrow. I'd love to have raw data rather than extrapolate for higher ambients but that's all I'm gonna have. Eventually I will run the same track with the GMPP radiator and C&R but not in March. Sonoma and Thunderhill 2 mile instead. I do think I have a lot of Sonoma data to compare to stock.

Your data looks nice. We even use the same kind of formatting . I'll see if I have time to collect vmax, I have that. For some reason Harry's doesn't collect oil temperature data. Odd. All in all I agree with you in that I also get faster time toward the end of the sessions but I think it has more to do with getting comfy with the car, lower traffic, and getting in the zone. My "feel" is that I have to increase throttle application to make up for lower power and vmax is suffering.

I had no power loss until I ran out of fuel, literally. I got towed off. This car doesn't have pump problems on low fuel from what I can tell. It does however deliver power in chunks when you run it hot. It has to do more with fuel maps and timing I think. Some have had fuel pump defects as well.

0D3PE

We ran into the same issues on the C6 ZR1 platform, you could change radiators and it would simply just add time till it would heat soak, we found the issue to be airflow across the radiator. Where the C6 fell short was the OEM shroud did not cover the entire radiator and the fan didnt move enough air. We solved this issue by designing a full shroud/fan setup which we now sell to pretty much everyone:

https://www.corvetteforum.com/forums...d-control.html

The issue I see with the OEM shroud on the C7Z is it does not cover the whole radiator, it relies on the hood duct with the vehicle at speed to move air through that section, I will be testing our own shroud/fan kit next week to see if this helps the issue.

peterjank

Thanks for putting these results together. It is good to see someone else doing some thorough back to back testing. My gut feel is that you will see some benefit to the C&R radiator when you run it in the higher ambient temperatures that caused the car to overheat with the factory radiator. In your current tests the ambient temps were not high enough to max out the cooling capacity of either radiator. When I tested the Ron Davis radiator against factory on 80 degree ambient days, I didn't see much difference in performance until water temp climbed above 230 degrees.
https://www.corvetteforum.com/forums...-radiator.html

johnglenntwo

Done!

vtknight

Sigh...so, in short, my C&R rad was big waste of money?

SBC_and_a_stick

I can see that being the case. Unfortunately I won't risk going through a whole season with just the radiator swap to collect data. To me 232* in 69* weather is worrisome.

There will be a lot of GMPP rad+C&R rad vs. stock comparisons coming up. I've made every effort I could to have GM release a fix and I can't wait to try it! I would have done the GMPP unit first but it came so slow I got the C&R unit in the meantime.

vtknight

What I'm getting from this and other threads on the overheating problems is that 230 degrees is the threshold when the car takes timing out. So if the radiator differences are only seen above 230 degrees - I think it may be too late...

Being less dramatic - I was told that no single rad is sufficient and that the true combo/trick is the secondary added in combination (even with the stock unit which now seems to be true).

Hopefully this is the case...

SBC_and_a_stick

I'd say there is a chance it would work better than stock if (1) you remove the intercooler from the nose of the car or (2) you run it in very high ambient temps.

I won't get to try it in either of those scenarios by itself. Hopefully, someone else will report. I bet there will be a lot of A8 guys using just a radiator upgrade this summer.

Poor-sha

Thanks for the write-up and notes. I like what you guys are doing with dropping this stuff in to Excel. I'll have to go look at my Aim data and see about doing something like that.

vtknight

As I also bought the secondary rad as you did - I very much look forward to your testing...

Mad Dog 24

Sbc thanks for the information As I read through this thread discussing air moving across the radiator. I thought is it possible the grill in the hood is holding anything back? It is fairly massive. Possibly not but it would be an easy pit stop during a session to remove and test. What goes in must come out! Just a thought.

I was a bit surprised the C&R is the same width as the stocker. I have a short track C&R in a NASCAR and guess its almost double the width as a C7 rad. I guess just to me common sense is the more area the cool air has to pass over an object the more heat is released. Yes some mods would need to be done to install a wider unit but could be worth the effort. Do any aftermarket company's make a thicker or wider rad?

Oh how I wished this worked for you....

Did notice your intercooler res. has few air bubbles a good thing.

rsilver

[QUOTE=SBC_and_a_stick;1591634991]Scope of work
Does this aftermarket radiator work better than the stock unit? If so, how much better?

SBC, thanks very much for sharing this and for all the work that went into it. ( it all takes time) Was hoping this might be enough. Looks like oil cooler time, at least for the A8 guys. will be real interesting to see how the secondary radiator does for the M7 guys.

5thGear

Ron Davis radiator is almost twice as thick as stock and the only double pass radiator. They developed the radiator for the Bondurant school.

Two of my friends with manual Z06 had good luck with Ron Davis. At Auto Club speedway 25 minute sessions advance level and 88F ambient had no overheating issues. 235F coolant and 275F oil temp. My other friend with Z06 A8 on the same day same level overheated in less than 15 minutes with stock radiator. Oil temp was over 310F and coolant over 250F.

I just had the GMPP secondary installed. I was considering the C&R but i think I will go with Ron Davis radiator before the beginning of the summer.

ktoonsez

I live about 3 minutes from Bondurant, so awesome seeing a sea of vette's . Anyway I have a Ron Davis radiator in my C6 and is still amazing 7 years later, really keeps the car cool (oil temps get to 295 and coolant stays at a cool 190-210) and I beat the hell out of it at the Proautosports events. Havent heard anything direct about the C7 version as I have yet to see anyone else with a C7 Z06.

Sorry OP for the off topic, back to C&R talk