firstgear

interesting thought about the steam.....is this system a closed system? If not then the question would be at what temperature does the coolant in the system boil?

CGZO6

Increasing the pressure in the system will help prevent cavitation (and raise boiling point), how to do that would be complex.

Would need a cylinder with a sliding seal on the inside placed into the system. On one side would be coolant, the other would be air that could be pressurized with an air chuck. During the vacuum bleed procedure you would want the minimum amount of air in the cylinder. After the vacuum bleed, add about 5 psi to the cylinder. This way the system is always starting with 5psi, and the pressure would go up as the system heats up. (Vacuum bleed when the system is cold)

How about putting another stock pump in the circuit? 2nd pump down by the stock reservoir? Having two pumps might solve your issues, assuming they don't both shut down at the same time.

Also, I believe that fluid cavities more readily the closer to boiling point it gets.

CGZO6

Yes closed system, boiling point depends on the water/coolant ratio and pressure. Lower pressure lowers boiling point, higher pressure raises boiling point.

The fluid in the system is at the lowest pressure where it gets sucked into the pump. When the coolant gets warm/hot it is more likely for the fluid to cavitate at pump entry. This is why I think it would be beneficial to pre pressurize the system when cold.

GSpeed

Not sure? The pump has a PWM function, but it is not PWMed, and it has a diagnostic function, that is not connected. Empty pins in the plug for that. This is a 2015.




We Too saw the harness replacement threads. We can make a call to the dealer, and see if there is anything available.



Its a closed, and sealed system. We are running 50/50 coolant/water, with a few psi on top. How much, were not sure. Its completely sealed once full, and cold. shooting from the hip, Id guesstimate 3-6 psi. We can put a gauge on it today.

We have our concerns with a twin pump design, not when running, but when a pump is lost. It starts to get messy if one shuts down. It also adds cost at this point, which we are trying to stay away from (for now) until we simply cannot move forward with out a redesign.


Back in the mid 2000s, Daytona prototypes would run a pressure relief valve on the coolant. No radiator cap. They ran 25-35 psi of water pressure, and pre-charged the system to 15 psi.

We can add a schrader valve, and see what effect it has, if we bump pressure up a few psi.

currently buttoning up the car, and hope to be on track before lunch.We will add the schrader valve to see what steady state, natural pressure rise is, and we can add a few psi in the pits, if we continue to have a problem.

GSpeed

We would need to isolate the pressure bump, like mentioned above. We can try to adapt a shock canister, and see how much pressure we gain in the system.

CGZO6

You could try adding a small inner tube to your expansion tank with the valve on the top. That would isolate the air in the tube from the coolant. Don't know if the inner tube would last being in the coolant tough.

GSpeed

Car is currently complete, bled naturally, and ready to go. We found that how we had filled the system prior, had allowed roughly 3oz of air. We did not vacuum fill it, nor pressurize it. Filled as best one can if he were in his garage with no tools.

Hopefully water quality remains high enough to not cavitate.

Results after lunch.

NemesisC5

Only 3 things I know of that cause cavitation; 1. Pump speed too high 2. Vapor caused by steam (highly unlikely) 3. Air in the system by some means.

What is water temp exiting the intercooler bricks?
What is water temperature exiting the front heat exchanger?

GSpeed

GSpeed

Pump stops when the temp spikes, and pump starts when the temp drops. Hump in the middle is the pump in shutdown mode.

Dabigsnake

Hey G-man. Just want to compliment you on your level headed professionalism. You seem to have a great way of dealing with all these arm-chair /back-seat posters. You sir are a gem. You obviously accept the fact that two heads are better than one, and are truly open to anyone's suggestions, or opinions. That shows your commitment to this project. It is really exceptionally nice to see someone with such knowledge, and no real ego/attitude that usually accompanies that. My hat is off to you, and THANKS from our Z family.

GSpeed

Good news and bad news:

Car ran 16 minutes straight.

Cliffs:

91* air

Water temp max 224 (still climbing 1.5*/lap)
Oil temp max 282 (climbing 2*/lap)
Trans temp max 228 ( plateaued)


Blower pump shutdown occurred 12 minutes in, 4 times as long as previously, but still reached shut down mode.

We can see that the temps begin to swing, 8 laps in, and then compound, eventually swinging 20* plus, and then shutdown mode.

We're making two changes, because the car now takes almost a full session to develop the issue.

Will update next session mid afternoon. We're running with "the drivers edge" track day guys, and very thankful they let us have run time in the fast sessions whenever we need it!

davepl

In your logging do you see a spike in CTS after the intercooler pump stops, or just in IATs?

I'm wondering if the increase in IAT leads to reduced timing which leads to more heat, or does the coolant temp not track the IATs at all?

GSpeed

We don't see any increase in engine coolant temp when this occurs. Only IAT2, and blower water temps, then a dead throttle pedal.

The next two changes are easy, the change after that, should this next run not work, will require the car to be taken down. we can't do that model change in less than 2 hours.

Will keep everyone posted

BigBird440

my whipple system never cavitate's big bosch pump well fed by reservoir
through the cooler and into the beast, on the spill down in the circuit there is a bleed hose that brings air from the tank back up to the fill it also acts as an overfill spill down kinda smart really

GSpeed

8 laps session 2, cavitation is better. No pump shut down.

Went right back out in the next session, and see if it'll do it again.

GSpeed

Car completed its first full session.

Ambient 96*

Engine coolant max 221
Trans temp max 249
Oil temp
Max 279

We did a total of 23
Laps over almost 35 minutes, with a stop between sessions for me to download data, check systems, and send him on his way again.

Full report coming soon. If you have questions, ask away. Still some validation to go, and beta test it.

GSpeed

Would also like to add that today is 4* warmer than the last test sequences. Track temp 155, ambient 98. IAT into blower 105.

Higgs Boson

Nice! Well done!

What about IATs? How are you logging boosted air temp? (sorry if I missed it)

jim2092

Looks like those "two changes" worked!