Poor-sha

I don't think official pricing has been released but I was told ~$400. Of course, we C7Z owners already have this part and I believe descartesfool already took a buy back on his Z51.

K B Vettin

Fan is 309 at Texas speed and is the stock fan for the z06.
http://texas-speed.com/p-4937-chevro...ngray-z51.aspx

What the z06 needs is a spal dual fan set up that has an aluminum shroud that covers the entire radiator.

K B Vettin

This is what the z06 needs, this is for the c6 but should offer the same results for the c7

Deuuuce

It's been my understanding that at highway speeds, cooling fans shut off as they become ineffective due to high speed airflow.

Which means on the track this upgrade would be nearly useless and what is needed is optimized airflow and higher capacity cooling.

Can anyone confirm?

Greg Quillen

Yes. Fan just restrict flow at high-speed.

Dr.Ron

I have no dog in this fight, and sadly I DO believe there are overheating issues with this car. Having said that, I was on track Monday with 2 C7Z's. I think both had stage 3 aero. 1 was manual, the other I didn't see for sure if he was auto or manual, but I think he was manual as well...The ambient air temps were a high of 53*.

Neither car overheated during the day.

1 car only ran 2 sessions (25 min.) for some reason, while the other car did 3 sessions.

Just adding data here is all.

Ron

jcthorne

This is not necessarily true. With the limited air flow through the small front grill relative to the size of the radiator, properly sized and pitched fans can indeed induce additional air flow above that from ram air.

Deuuuce

I believe it. Has anyone tracked what the lowest ambient temp was when an overheat occurred?

I'm sure it's possible, but just being a casual observer of the topic of cooling over the years, the velocity of the blades would be so high that I doubt any automaker offers such a set-up. The noise and current draw alone being prohibitive.

I'm speculating but I think 55mph is probably the highest road speed any manufacturer's fans operate. Perhaps the Veyron an exception.

jcthorne

You are still thinking the velocity of the air across the radiator is something close to vehicle speed. In a car with the front of the radiator more or less slab sided facing the incoming air, that might be true. Not even close with the air inlet to a 'box' high pressure zone in front of the slanted radiator. It slows considerable as it expands to cover the larger face of the radiator.

I do not think the Z06 cooling fan shuts down below 55 mph as you suggest. Sure there is a velocity where the ram air will overtake but its about time spent at that point or higher vs time spent below that velocity where the fan does assist. Even on most tracks, the car spends considerable time below 55 mph or what ever the velocity threshold is.

This likely why the Z06 has the more powerful fan than the Z51. Its not larger, just more powerful motor and different pitch blades. It was an attempt to overcome the front aero that is limiting air flow across the radiator.

descartesfool

It's not that the fan reduces flow at high speed, it's the fan shroud that blocks airflow. That is why you will never see a fan on a race car. Race cars have no fans behind the radiator and of course no shrouds. Half the area of the radiator is blocked by the shroud. Fan is round, radiator is rectangular. Place a circle over a rectangle and the area outside the circle needs to be covered with a shroud for the fan to work effectively at low vehicle speeds such that the fan can create enough pressure drop to pull sufficient air through the radiator core in very hot outdoor temps with the car stuck in traffic. The C7 has a series of small flaps in the shroud that open to let air flowing into the radiator bypass part of the shroud when the car is running fast, which increases total airflow through the radiator and thus improves cooling capacity.


The Z06 fan/shroud assembly is virtually identical to the one in the Z51 for which GMPP is offering the upgrade. So no more airflow at speed on track as the fan and shroud are all the same size, as are the bypass flaps. The only fifference between the two is that the Z51 fan motor is a 500 Watt motor while the Z06 fan motor is a 600 Watt unit, so just a few % points more flow. Radiator for the Z06 and Z51 are identical, as is the duct from the fan outlet to the hood vent. The airflow path is identical. GM probably only increased the fan speed power to compensate for the higher pressure drop across the radiator area due to the addition of the Z06's intercooler cooling core which increases pressure drop through the condenser/radiator assembly as it is placed in front of those 2 cores which are in the Z51 and Z06. Z06 has 3 cores in series and thus needs a slightly higher power fan to keep it cool when it's stuck in traffic.


This slightly higher power fan being offered for the Z51 will do nothing to solve the overheating issues on track. My Z51 overheats on track, with the coolant temperature gauge constantly rising until it hits the end of the dial and the "Engine Overheating- Idle Engine " warning comes on.


Car needs more airflow into the radiator, a larger area radiator, less pressure drop across the radiator, or a higher efficiency radiator, or some combination of those. It does not need a bigger fan to keep it from overheating on the track. The Z06 grille has less flow resistance than the Z51 front grille, so that is an improvement to reduce pressure drop and increase airflow. But that won't help a Z06 as there is no better grille on offer.


These parts were all shown almost a year ago at the SEMA show. I posted some of the pictures before, but here they are again in case you never saw them.

Poor-sha

Thanks descartesfool, I definitely missed that the first time around.

Mad Dog 24

Interesting, while investigating the Ford GT 40 cooling systems. Found some of their track specs and the very same issues as the new Z06 has. The GT has many similarities to our cars. High Perf. Supercharged big V8 with minimal fresh air because of body configuration and aero.

DYNAMOMETER
Engine dynamometer tests were conducted using early prototype engines to validate heat load assumptions made at the beginning of the program.
The results shown below validate the initial program design assumptions and the engineering models. The thermal bench and dynamometer testing provided confidence that the vehicle cooling system would perform to target.
WOT Heat rejection testing
Engine Control Targets for Testing.

WOT 1100 to 6100 RPM in delta 200 RPM steps
Engine Coolant Outlet Temp (°F)
Combustion Air Inlet Temp (°F)
Engine Oil Outlet Temp (°F)
195 77 240
210 77 250
220 77 260
230 77 270
240 77 280
WOT Heat Rejection

Note oil temps to 280 also some test where they reached 300! Many complaints by GT track rats and ideas thrown around. Same issues as us, where to put additional coolers and on and on. Oddly enough seems the GT owners complained with much less manufacture bashing. The new GT has some really "cool" engineering ideas to keep oil temps down.

RC000E

One definite means to reduce temps is the use of ethanol. I posed this question in the "Ask Tadge"...you guys mind backing me up and voting for it before Nov 1?? Voting option is C7 and E85. GM is heavily invested in Ethanol manufacturing, and Corvette Racing has used it for years. I have theorized why the Corvette didn't have it, but was curious right from Tadge what the reasoning was.

Vote here please...just real quick!

https://www.corvetteforum.com/forums...er-2015-a.html

SBC_and_a_stick

Good comparison. Indeed there are many similarities between the two cars. I've found the report and there are some higher targets set here by Ford than GM set:

"Performance targets are shown in this chart:
Maximum
Allowable
Temp (°F)
Ambient
Condition (°F)
Engine Coolant Outlet 245 110
Engine Oil Outlet 300 110
Combustion Air 200 110 "

So it seems that Ford wanted to design a car that keeps coolant under 245* and oil under 300* in 110* ambient. By contrast, Tadge stated goals for C7 Z were coolant under 262* (and I want to say 320* oil) in 86* ambient. Not directly stated as 262* by Tadge but that's when the car overheats.

It would be good to see a similar test for the C7. I managed to hit 246* coolant and 285* oil with super cold ambients in the 60*s. That's higher than everything in that chart for inlet temp 77*. My average RPMs were likely under 5,000 as well.

For both of these reasons I would think the Z runs much hotter than the Ford GT but I could be wrong. The GT is ultimately 10 years old so it was designed to satisfy the lower standards of a decade past. I think most manufacturers have upped their game in the last 10 years.

Link:
https://www.roush.com/portals/1/down...04-01-1257.pdf

jcthorne

No, I think you are reading the numbers correctly. Yes, the FGT could be pushed on the track to overheating but it seems not nearly as easily as the current design Z06. I think GM cut the margins more than a bit too close.

In this day and age, designing any car to only perform its intended purpose up to an ambient 86degF is pretty far from the mark when a large portion of the car's customer base lives in climates WELL above that temp.

LdkE

- AND - here in Germany we are on the one hand not that large (but increasing reasonable) portion of the Z06 buyers but on the other hand we have similar temps in the lower 100s in summer. That said and without a speed limit it is much easier for the Z06 owners/future owners here in Germany to get the Z06 to the boiling point and hence in the area of missing HP.

Had almost pulled the trigger this summer to order a '16 Z06 convertible, but with the ongoing serious information about the overheating probs from you guys in the and a missing GM solution I pulled the brake for my purchase until a solution, either by GM or after market, is proved and in place.

Until this happens I keep on driving my C6 conv. (what is not that bad )

Cheers

Lars

Telepierre

Interesting point. The autobahn factor..so the Z06 hits/handles 100Km/h @ 1300 RPM; 200Km/h @ 2700 RPM and the 300 Km/h (186) drag limited peak can be maintained at approximately 5500-5700 RPM.

Considering the massive air flow do we see overheating issues here as well?

Cheers

LdkE

What is reported in the German Corvette Forums is that as soon as you stop the car after a hard and extensive drive (e. g. for a fuel stop) the heat crowls into the charger and heats up the whole unit - the result is that the whole unit can't be cooled down again and runs into the "reduced HP/limp mode" and after that it doesn't matter if there is "massive" airflow or not - not enough to come to the normal temps witout a longer stop to cool down.
We can read here as well that it is more or less difficult to get to 300 km/h or above and/or it needs a lot of time to come close to this speed.

Curious where all the 650HP Z06 power is eaten up if the electronics is not hindering the horses to run.

Cheers

Lars

axr6

That is a very significant difference; At 110F, 245 coolant and 300 oil are very reasonable expectations. 110F is a full 24F higher than GM's spec of 86F. If we try to extrapolate the expected running temps for the Ford GT at 86F, it would be close to a reasonable 221F coolant and 276 oil.

Telepierre

The coefficient of drag coupled with the progressively increased down force of stage 1 - 2- 3 makes 300 long and hard to get. This is by design compromise though so nothing worrisome if curve/track prowess or 100 to 250 Autobahn runs are the goal here..

As for the post hard drive HGW/Autobahn overheat you mention I find it hard to reconcile/verify veracity as I know the 06 is "literally sleeping" at 200km/h @ 2700 RPM so if for "hard drive" we are talking multiple HGY runs in the 80 to 250 Km/h (1000-4000 RPM) causing overheat - I really don't believe it.

IF, the "guy" is trying the same on a 06 AT by constantly burning tires between first and third gear constantly pegged on the 6500 mark to reach his "goal" then I say it's an operator flaw as the torque on the 06 allows the same on taller gears.

All said, I would not take an AT to the "green hell" to beat on it...
A manual though should do fine.

Cheers.