SBC_and_a_stick

The test with the hood off was definitely an eye popping result. I would have expected large cooling improvements with the hood off.

The difference between the coolant temps and oil temps tells me you guys are certainly fixing the coolant overheating problem. It took a huge amount of modifications to get to where it is. The C7 Z platform is a huge challenge. I remember when I first overheated 16 months ago I was being told an $800 radiator would solve it. Right...

NemesisC5

Great work

spearfish25

Regarding oil temps, you said you did 6 laps before going into limp mode at 302* and then added a second oil cooler the next session. You then made it 12 laps before limp with 302* oil, and you concluded the additional oil cooler didn't do anything. I don't understand. It seems like it made a huge improvement.

The improvements being made so far are slowing heat absorption by the system but aren't enough to completely stop it (still net positive). So with time we end up at the same overheat but that time is getting extended. You've made some huge strides!

I suppose the ultimate goal is a cooling system that will shed heat faster than its produced and thus have a steady state in the ideal ranges you've posted.

But that additional oil cooler helped!

SBC_and_a_stick

The longest run I see in the PM where the engine coolant temps are shown and the driver is pushing it without slowing down is 10 minutes, which is about 6 laps on this track. Maybe they ran the car for 12 laps but they took cool down laps so only 6 in a row are good for data.

spearfish25

Check out the third post talking about the Saturday test runs. They list the PDR info with number of laps completed. That's the section I noticed the oil cooler change and doubling of completed laps. But maybe other factors were at play too.

I'm reading on my phone though so seeing everything and interpreting things correctly is kind of a challenge.

arturox2

Subscribed.

GSpeed

Unfortunately that test day turned into somewhat of a mishmash, because we were thrashing to add the 2nd cooler. It did double the run length, but it was still a failure in our eyes due to still reaching 300+ Engine oil temp.

We have doubled the size of the cooler for tomorrow's test, but 1/3 does not get airflow at the moment.

We also improved trans cooler airflow, so hopefully we see positives from that as well.

We will get two model changes in tomorrow, provided no issues pop up.

Dabigsnake

Thanks guys I love to see real data, and not just seat of the pants stuff. Too many Wizards in Oz. You guys rock. Hopefully this will all end with a benefit and payback for your hard work. I'll sit back and listen for now.

descartesfool

As a scientist, I know that when you are measuring things, calibration of all your sensors and channels is a mandatory requirement. I would put all your sensors in a big tub of distilled boiling water and calibrate them all at the same time using the math channel adjustment of the Race Studio software. That way you know your temperature deltas are going to be good. Is there any way you can place one of your sensors in the same spot as the OEM sensor with a thread adaptor to see if you read the same temp at the same location. The 15-22 deg difference you have now is huge.


I think the overall solution will be good once the temperatures stop rising and level off with continuous lapping, basically taking the system out of thermal runaway it is in now. One wants a stable cooling feedback system, not an unstable one. If anyone was running this car in an Enduro, one would need all temps to stabilize at some acceptable values. My new AMG GT-S shows zero signs of overheating any fluid after 30 minutes flat out on track. Same thing for my GT-R on which I added a transmission cooler and secondary oil cooler. Temps hit a max and just stay there. But they don't have as much power as the Z06, however it's really nice to run a car on track and not have to constantly look at the temperature gauges.

GSpeed

We agree with you on the calibration. Unfortunately part of our discrepancy is probably the reporting differences between the Aim dash, which shows effectively instantaneous changes, and the PDR/dashboard which are pretty heavily filtered in comparison. It's tough to quantify the difference when there's so many other factors at play. SUPER frustrating we can't get a data export out of the PDR to compare apples to apples with our other datalogger, but that's just the way the game is played sometimes.

For example, as the car's coming off track and sitting in hot pits, the dashboard and Aim logger will indicate coolant temps within a few degrees, say 235° displayed on the dash, and 230° on the MXL2. As we're sitting there idling, however, the MXL2 reading will drop to 215° within 30 seconds or less, while the dashboard stays above 230°. It's no surprise to anyone here an OEM coolant temperature sensor doesn't give super precise readings, but for our purposes, we need to understand its characteristics better.

Today's agenda will entail wiring up OBD2 connection so we can log the ECU temperatures directly, calibrating at least SOME of the sensors to a known temperature, and squeezing all that in between test runs.

Jake

CGZO6

Could the ECT temp difference be due to the OEM temp sensor absorbing heat from the coolant AND the cylinder head, as opposed to the other sensor is installed (I assume) in out coolant line (no heat soak from the head)?

spearfish25

I noticed the dash gauges in the DIC are very slow in comparison to what I get from an OBDII monitoring device. I was using Dashboss and my oil temps in Dashboss shortly after startup will say 180F while the DIC was still reading 130F. After a few minutes more, the DIC gauge will better correspond to the OBDII connected gauges. My understanding was OEM computers/gauges do a lot of averaging so customers don't go bananas when their coolant gauge is swinging up and down with instantaneous values.

jim2092

This is a very interesting and probably important thread resulting in the eventual noticeable improvement in the ability of our ZO6's to race longer and faster. But it also causes me to see two other facts.

1. The very difficulty (and expense) of improving on the cooling of this format probably has a lot to do with why the car didn't come with it from the factory.

2. And sadly, why the alleged cooling improvements on the 2017 from the factory will not be sufficient for those who want to really race this car either.

GSpeed

Currently we are on track.

AIM system is pulling all data now, we left the PDR card out, mistakenly. Next session. AIM system does pull temps off the CAN bus, so my assumption is that it will have the same info as the PDR.


Notes as of this morning:

Ambient 86* (down from 96 last weekend)
Track temp 115* (down from 150 last weekend)
3/4 fuel

The ambient temp will rise today, we are just running as many sessions as we can to validate this.

JoesC5

Great information. Too bad GM didn't feel it was necessary to go to the trouble to do what you and LG motorsports have been doing.

You made a comment about all the horsepower the Z06 has and it's effect on the cooling abilities of the radiator, etc. The C6 ZR1 was only shy 12 Horsepower of the C7 Z06 and it didn't' have the cooling problems and it appears that the grille opening is actually larger on the C7 Z06 than the C6 ZR1.

I don't recall anyone having to cut up the front bumper of the C6 Z06 or ZR1 to solve any cooling problems(but some did remove the stock fog lights and install secondary coolers, or brake cooling ducts).

spearfish25

Intersted in everyone's thoughts on this too. There are a lot of high horsepower cars with intercoolers, superchargers, turbos, etc that don't seem to have this issue. And their front fascia openings or side intakes don't seem worlds larger than the C7Z's.

GSpeed

Quite possibly. When we calibrate both sensors, that would be my guess. Our sensor we added is isolated by a rubber hose from the engine, whereas the GM sensor is screwed into the head.

ZR1 actually have overheating problems too. They don't go into limp mode as harshly as the C7Z, but the problem is still there. One theory is that the lessons from the ZR1 prompted the limp mode behavior on the C7Z since they're similar supercharging systems.

Learned some good stuff from our last session. Should have a bunch of graphs up here shortly after lunch.

Jake

dar02081961

Are you sure about that?

I don't know of any other supercharged car that produces 650 ft lb of tq over as wide a power band while packaged in a 3500lb frame.

The ZR1 is the closest comparison. While as Joe mentions at the peaks its only 12 hp shy of the Z06 they overheat as well during extended track duty at high ambient temps. But that 12 hp is at the peak. At other points on the power curve the difference can be 20-30hp and up to 100ftlbs of tq from the same size engine. In other words there are times where the LT4 is producing gobs more heat which has to be dissipated as compared to the LS9.

The OP's efforts are to be applauded. What it has proven thus far is when keeping the appearance of the car and mass marketing in mind GM did a pretty decent job to satisfy fit form and function.
Could they have added more cooling? Yes but it would have been at the expense of the cars appearance or size. The other option would have been to give us the original 625hp/tq they planned for. I am glad they gave us the 650hp/tq instead.

DLC7

davepl

If you sync the clocks you should be able to align the data based on a timestamp. Just an idea. I imagine the Cosworth tool can export a time column with its data, ideally down to the second or better. If not, ignore.