is there a radiator we can buy that will take the full gpm of the waterpump at wot

[VikingTrad3r]

recent acquirer of a 91 zr1. love it. taking it to the track for some hpde.

ive read about the bypass, studied dynomites posts and read about other experiences.

the root issue as i understand it is, and fill me in if im wrong, is that the orifice sizes of the radiators are too small and therefore the pump cavitates and excess pressure is built up and the pressure relieve operation in the crossover was a way to get around this.


so my question is, is there a triple or double core that has been designed to accomodate higher gpm flow rate at wot? this would avoid the cavitation. avoid the pressure. avoid the bypass and recirculating of some uncooled fluid.

if i had to install a swedge to expand the size of the coolant hose i would do it. the bottom would be tight but id find a way.

thanks.

[Dynomite]

the root issue as i understand it is, and fill me in if im wrong, is that the orifice sizes of the radiators are too small and therefore the pump cavitates and excess pressure is built up and the pressure relieve operation in the crossover was a way to get around this.


Pump cavitation in an impeller is the result of a drop in pressure of a moving liquid through the impeller's eye. This reduced pressure causes bubbles to form, as the pressure of the liquid continues to fluctuate and drop, the bubbles collapse. This starts at around 5,000 rpm and would actually reduce the increase in coolant flow and resulting radiator pressure buildup. Which increase in radiator pressure is too much for the seals on each end of stock radiator. The problem is the inherent 7,000 rpm capability of the LT5 and having a water pump that is a bit low on gpm at 2,000 rpm while a bit too much flow at 7,000 rpm (ignoring the effects of cavitation for a moment).

Now having said that, I would expect the various aluminum radiators to not have this inherent weakness not having the same end seals as the stock radiator. Further, the flow characteristics would be different for each radiator (head loss, coolant paths, and heat transfer).

As Per Marc Haibeck graph provided to the ZR-1 Net email list by Graham Behan about ten years ago, the Coolant Pump flow rate through the engine (not the radiator or thermostat) is:
15 gpm at 800 rpm
18 gpm at 1,000 rpm,
44 gpm at 2,000 rpm,
65 gpm at 3,000 rpm,
90 gpm at 4.000 rpm,
120 gpm at 5,000 rpm at which time cavitation is starting.

We do not know water pump flow after cavitation starts and we do not know head loss of coolant flow through various radiators. We do not know current pump flow through stock radiator as the test above was pump flow through engine only.

I have not seen the design pressure characteristics of Aluminum Radiators listed and would assume which pressure is greatest at the top and reduced by head loss as coolant is forced through radiator.

This whole discussion is a bit complicated by a water pump that does not function well on either end of the rpm range of the engine and a radiator with an inherent weakness because GM did not want a unique radiator for the circumstances 😜

Instead GM settled on a most unique thermostat housing and thermostat to solve the high coolant temperature issues (Warm Climates) associated with high engine rpm and the radiator pressure using a conventional water pump impeller which works for most of us. That is except for HOT desert climates and traffic (we then go to Aluminum multi core radiators keeping rpms above 2,000 rpm in traffic) :p

Some guys have even modified fan function for higher air flow rate which definitely will help coolant high temperature issues in traffic :thumbsup:

If we determine that our multi core aluminum radiators will take the pressure we still have the cavitating water pump as a secondary issue.

[VikingTrad3r]

Thank you for the reply Dynomite!

Ive noted your path for an increased radiator cooling has been the ron davis, lately.

My circumstance is that i want to build an LT5 road track car for lapping and track days.

If possible, id like to “”let the beast out” in those higher rpms and when i learned about the whole waterpump issue castrating an otherwise incredible piece of equipment it bothered me.

i havnt found a well documented solution, which, now that you have refreshed me on cavitation, it sounds like an electric waterpump which controls the impeller rpm in a nonlinear relationship to engine rpm is the only solution. combined with the ron davis or dewitts.

do we have members of this forum currently running electric water pumps and have they demonstrated it as being the fix?

[Dynomite]

Thank you for the reply Dynomite!

Ive noted your path for an increased radiator cooling has been the ron davis, lately.

My circumstance is that i want to build an LT5 road track car for lapping and track days.

If possible, id like to “”let the beast out” in those higher rpms and when i learned about the whole waterpump issue castrating an otherwise incredible piece of equipment it bothered me.

i havnt found a well documented solution, which, now that you have refreshed me on cavitation, it sounds like an electric waterpump which controls the impeller rpm in a nonlinear relationship to engine rpm is the only solution. combined with the ron davis or dewitts.

do we have members of this forum currently running electric water pumps and have they demonstrated it as being the fix?

Pete has done that :thumbsup:

http://zr1.net/forum/showthread.php?p=227285

More Electric Water Pump Discussions follow:

http://zr1.net/forum/showthread.php?t=25524

http://zr1.net/forum/showthread.php?t=25219

http://zr1.net/forum/showthread.php?t=16562

In this post grahambehan verifies that Cavitation reduces water pump flow at high water pump rpms.

http://zr1.net/forum/showthread.php?p=227422



The cavitation is present on the LT5 pump at high rpm reducing flow, it is actually a pretty efficient pump, even by todays standards, prolonged high rpm use could present problems.

Graham.

[Karl]

You can also run Pete's underdrive and lightweight water pump pulley and increase the useable rpm of the water pump before cavitation happens.

I have one on my '93 and had one on my '92 and no issues.

Granted I do not do road racing or such, I do drive my Z agressively on a regular basis.

[Ccmano]

:happy1:

[VikingTrad3r]

You can also run Pete's underdrive and lightweight water pump pulley and increase the useable rpm of the water pump before cavitation happens.

I have one on my '93 and had one on my '92 and no issues.

Granted I do not so road racing or such I do drive my Z agressively on a regular basis.

Furthermore, would an underdrive pully not exacerbate the low rpm low flow rate issues which also result in an overheat solution.

[VikingTrad3r]

Here is my plan:

1. drill 3 x 1/8th holes in the stock 180 tstat, with factory radiator. see what happens at the track.

I took the time to pull the oil cooler and radiator and clean them all up, they were full of crap, so i'd like to have my own baseline experience of the stock system with the 3 1/8th hoes. The 1/8th holes are to help increase pressure transmitivity through the thermostat restriction and thereby an attempt at eeking another few hundred rpm before the bypass reaches its relief pressure. I will log this.

2. install a ron davis or dewitts 2 row x 1' wide radiator. If any of you have a used one that has been pressure tested and would like to sell it, let me know i will buy it.

3. try the electric pump. my idea for the "warning light" if the pump is not turning, is to install 2 x large RED LED bulb and place them into the ventilation louvers, so they are out of sight and totally un-noticable, UNLESS the electric pump has failed then they will light up and the car can be immediately pulled over or off the track in my case.

any ideas on the right type of sensor to detect normal operation of the e waterpump? i was thinking as long as the circut is completed then the light will be off. if it fails, then it lights up. however, it occured to me that similar to the secondary vacuum pump, it could seize, but still take power. so then i was thinking a pressure sensor, as long as the waterpump maintains a certain pressure in the system, then the circut to the light isn't completed. but if it drops below the rating of the sensor, it lights the lights. but then i was thinking if you don't catch it in time, you could easily boil your engine, and the pressure from the excess heat would keep the warning lights off.

thoughts please.

[A26B]

Another factor in heat transfer that has not been discussed, is retention time. When velocity increases, the contact time for thermal transfer is reduced. Increasing the flow rate through the engine with a higher capacity electric pump will result in higher pump discharge pressure, due to the fixed restriction area of the engine. So there will be a point of diminishing returns that we really don't have data on.

The cavitation, described by Dynomite is an inherent characteristic of centrifugal pumps due to insufficient suction head pressure. This is frequently solved by multistage centrifugal pumps, i.e. more than 1 centrifugal pump in series. The differential pressure across the radiator may be rectified with a higher flow capacity radiator. I contacted Ron Davis years ago about the radiator flow capacity, gpm at max rated working pressure of the radiator. They had not performed that test at that time. I think that needs to be established as it may solve a portion or even all of the cavitation issues with the stock water pump, depending on how the flow rate through the engine is affected by the higher flow rate. From my conversation with Ron Davis, their primary design focuses on racing. For NASCAR, that means sustained high speed which pushes a lot of air through the radiator. Road track racing isn't going to be quite the same. Maybe someone (Dynomite??) will take the chance, by blocking off the bypass and running some high rpm passes at different speeds to see how much the cooling system will take.

And then there's always the thermostat to consider. Will it ultimately be the restriction that is to blame? Will it even handle 120gpm or even 90gpm?

How about the engine's flow characteristics? What is the maximum flow rate that can be achieved within the pressure limitation of the system?

[VikingTrad3r]

Pete has done that :thumbsup:

http://zr1.net/forum/showthread.php?p=227285

More Electric Water Pump Discussions follow:

http://zr1.net/forum/showthread.php?t=25524

http://zr1.net/forum/showthread.php?t=25219

http://zr1.net/forum/showthread.php?t=16562

In this post grahambehan verifies that Cavitation reduces water pump flow at high water pump rpms.

http://zr1.net/forum/showthread.php?p=227422

Thank You again Dynomite for replying with that list of threads.

I've read them all and I now have a "pathway" to a solution. I will gather data along the way. It does appear that I could get to a sustained 5800~ish rpm with dewitts or ron davis and a few holes drilled in the tbody flange and not overheat.

truth is i am looking to wind this baby up to her potential as a track superstar and therefore looking for a cooling solution all the way up to the late 6000's and early 7000's. we shall see and I will surely report findings back here.

[Karl]

Furthermore, would an underdrive pully not exacerbate the low rpm low flow rate issues which also result in an overheat solution.

I never had a cooling issue with my '92 in traffic with the AC on. Granted I usually run 70/30 distilled water to antifreeze and had a fluduine radiator also.

The AC on my :93 does not work but no cooling issues.

Edit: Pete also drilled a few holes in my t-stat to increase flow and I have a DeWitt aftermarket radiator.

Ultimately a electronic water pump is best but do you want to risk the pump not working for some reason and risk blowing an engine?

[klork]

So if you get a better radiator that can withstand more pressure could you take apart the bypass and shim the spring so it doesn't bypass till a higher pressure?

[VikingTrad3r]

im going to find out! just bought a dewitts.

[A26B]

So if you get a better radiator that can withstand more pressure could you take apart the bypass and shim the spring so it doesn't bypass till a higher pressure?

Assuming operating temp is reached and the thermostat is functioning and fully open;
Installing a different radiator with increased flow capacity, will reduce the back-pressure at the bypass loop. In turn, the bypass valve spring on the thermostat will remain closed until the flow rate is increased sufficiently to once again create sufficient pressure to open the bypass.

Bear in mind that the thermostat at the discharge side of the radiator also contributes to back pressure and will at some point, yet to be determined, become the next critical bottleneck to eliminating the bypass system.

[Jagdpanzer]

Before you start changing the cooling system design a full understanding of the original system is essential. The original system relies on significant flow of coolant to be continuously circulated through the engine at pressure to eliminate hot spots and steam pockets from developing. The spring loaded bypass control valve on the thermostat plays a important role in this by partially blocking the bypass flow so coolant pressure will build inside the engine. Once the engine discharge temperature is in the control range of the thermostat it begins to open allowing cool water from the radiator to mix with the water making its way around the bypass control valve which shifts due to the pressure differential to compensate for flow now going through the radiator. Another important role of the bypass control is to limit the maximum pressure on the cooling system during sudden high rpm operation. The thermostat by itself is not capable of reacting fast enough under these circumstances to control the peek pressures that can develop.


Sent from my iPhone using ZR-1 Net Registry (http://r.tapatalk.com/byo?rid=90383)

[VikingTrad3r]

Coming back to my 2019 post with an update.

I found for quite a while that I simply wasn't a good enough driver on track that I would even push my car to the point of overheating the factory system.

This year (after acquiring data, via the Garmin Catalyst) i reached the max capacity of the factory system. I removed the factory unit and installed the full aluminimum unit.

Furthermore, I did the Tyler Townsley mod and cut the spring in my thermostat.

Results are:

Highway cruise is no longer an issue in 6th, it easily holds 70-80c at highway cruise.
My AC is actually COLD.

sustained high rpm runs where the LT5 is allowed to run up several times per lap above 6000rpm have resulted in a max temp of 113c on and ambient 30-34 day on the tarmac.

Typically, temps are not higher than 104 on track. But sustained high rpm will hit 113c. My prior trip to the track they hit 110c. I think I am pushing the car harder and harder (and my performance on track is showing it) and i might bump up against the limits of this setup too.

Any comments from the experienced crowd appreciated!!!

I suppose the Pirate Team removed the crossover, installed a monster high GPM flow rate rad, and let er buck hey?