Electric Water Pump questions ...

[RussMcB]

Last month at NCM (C4 Gathering) and Road Atlanta yesterday I couldn't drive more that a lap or two at speed without the coolant temps quickly reaching 124-127 degrees C.

I still have a stock radiator, which I plan to replace, but I'm not sure that by itself will solve the problem, which (I assume) is primarily due to the LT-5's unique high-RPM radiator bypass system.

If I switch to an electric water pump system (along with an improved radiator), will that solve the problem? Has anyone done that and confirmed it keeps an engine cooled during semi-sustained high RPM's?

Are there any good write-ups describing how to do it, parts needed, what to do with the original water pump, etc.?

Thanks.

[GOLDCYLON]

I suggest a Dewitts radiator with SPAL fans. Not sure if an electric water pump will solve your issue due the LT5s bypass system that you mention. However extra cooling capacity and faster fans than stock will.

[RussMcB]

Thanks. I'll look into that radiator.

I don't think fans come into play with my issue. I think they are just freewheeling at speed.

[GOLDCYLON]

Thanks. I'll look into that radiator.

I don't think fans come into play with my issue. I think they are just freewheeling at speed.

Take it from a Daily Arizona driver. The fans matter!!!!! Anything that can dissipate heat faster coupled with increased CFMs movement across the cooling surface matter.

[RussMcB]

I believe you, regarding street driving, especially stop & go, idling, etc. My problem is when I'm driving 70 - 150 MPH.

I'm assuming a C4 Corvette has sufficient airflow at speed (high pressure ahead of the radiator, lower pressure behind).

I do think better fans could help it cool faster after I come off the track, and I also think (based on what I've read today) that a better radiator, and perhaps holes in the t-stat will reduce the pressure, raise the bypass RPM and allow more coolant to go through the rad, but I don't think that is enough.

I wonder what Morrison, Rippie and others might have done to their race cars?

[secondchance]

I think for high speed driving high performance radiator and one or two 1/" holes on thermostat flange should keep engine coolant in check. I believe LT5 water pump moves sufficient coolant. If anything I suspect too much coolant at high RPM combined with relatively weak aluminum/plastic radiator may have resulted in radiator bypass. Once radiator is beefed up, Drilling one, two or three holes on the thermostat flange will allow more coolant into the radiator reducing bypass effect - non-cooled coolant back to the motor. Also, bear in mind that coolant moving too fast through the radiator will also return in sufficiently cooled coolant back to the motor.
I suggest high performance radiator such as Ron Davis or Dewitt and experiment with number of holes on the thermostat flange.
For street driving, especially in stop and go traffic in 90 plus day, higher flow fans become essential also.

[efnfast]

Have you checked to make sure the radiator isn't blocked? Our cars are bottom feeders. I'm not sure you want to defeat the bypass arrangement. The reason the radiator has a bypass is because at high speed the water pump will do over 100 gpm. The radiator can't handle that.

[XfireZ51]

You have warning if a mechanical water pump is going out. Not so w an electric one.

[Kevin]

After marker rad and a modded stat will do you just fine

[Pete]

Russ,i have done electric WP.

The issues your having at or above 5800 rpm the water does not go thru the radiator it goes thru the bypass back into the motor (never cools).

With a 55GPM electric you won't have to worry about the factory bypass.

I think for what your doing, a bigger radiator and 55 GPM should do you fine.

That 5800 RPM bypass is terrible i had done a few highway runs on a hot day and boy temp went up like a son of a gun.

I have used Meziere http://www.meziere.com/ps-1148-1116-wp336s.aspx
Then went with the Stewart inline http://www.stewartcomponents.com/index.php?route=product/product&path=63&product_id=69

Both worked same the Stewart fit nice over the cross member inline the lower radiator hose.

Send me your email i can mail you some pictures my email: petezr1@gmail.com
I still have the complete kit (no electric pump) i will tell you how to do this very simple really.

I also have Under Drive Water Pump Pulleys that will raise the bypass RPM to about 6100 RPM
Pete

[RussMcB]

Have you checked to make sure the radiator isn't blocked? Our cars are bottom feeders. I'm not sure you want to defeat the bypass arrangement. The reason the radiator has a bypass is because at high speed the water pump will do over 100 gpm. The radiator can't handle that.I straightened the fins (they weren't too bad) and blew out some junk/dust, but I know it'd need to come out to do it right.

You have warning if a mechanical water pump is going out. Not so w an electric one.Good point.

After marker rad and a modded stat will do you just fineYea, it sounds like those are two good steps in the right direction. I'll probably start with that and see how it does.

It's too bad they couldn't have done some type of blow off valve that only bled off enough to keep the pressure at a safe level but leaving most of the flow intact.

Thanks for the input.

[A26B]

Russ,
I'm going to echo some of what has already been said here, but here's my 2cents worth.

The LT5 bypass is a simple, spring loaded valve that begins to come off seat when coolant flow gets high enough to create back-pressure, from the radiator inlet to the water pump suction..... which includes going through the thermostat.

The solution is to reduce backpressure by increasing flow capacity through the restriction. Understanding your intended purpose is track related at speed, 70~150mph, I recommend the Ron Davis Radiator (I have one in my ZR-1) which is specifically designed for racing. With added flow capacity, you are also going to get more cooling capacity, so a 2 for the price of 1 special.

As for the thermostat, I have had 3 holes drilled in my thermostat for years and have never had a need to install the 160F T-Stat in my tool box. An open thermostat is open whether 160 or 185. Drilling the holes helps to reduce the restriction/backpressure at the thermostat.

At 70~150mph, I don't think the fans are going to be needed, but if they are, you can always add them later.

Keep us posted on how it works out!

I'm glad we got to meet at BG!

BTW, you can also remove the rubber seal at the rear of the hood to facilitate air flow under the hood.

[efnfast]

It's my understanding that the bypass is not an open or closed loop, but rather modulates to allow some water through/around. I would think if all the coolant bypassed the rad, the motor would over heat at lightning speed, plus that design wouldn't make sense at all for just that reason.

[A26B]

It's my understanding that the bypass is not an open or closed loop, but rather modulates to allow some water through/around. I would think if all the coolant bypassed the rad, the motor would over heat at lightning speed, plus that design wouldn't make sense at all for just that reason.

That is correct.

Bypass volume is directly related to water pump output which is related to rpm.

Increase radiator flow & thermal transfer capacity +increasing thermostat flow capacity (holes in flange) will = reduced bypass volume & increased heat transfer.

Caveat: There is of course a lot more involved in centrifugal pump flow characteristics, fluid velocity, thermodynamics, etc. but within reason, the above holds true.

[Dynomite]

I suggest a Dewitts radiator with SPAL fans. Not sure if an electric water pump will solve your issue due the LT5s bypass system that you mention. However extra cooling capacity and faster fans than stock will.
I do not see Dewitts Radiator in you signature??

Which Dewitts Radiator are you using and where did you get the Dewitts Radiator?

[RussMcB]

Appreciate all the responses.

The main reason I started this thread was because I've read posts suggesting that once the bypass is fully activated, the coolant is going to follow the path of least resistance and therefore not much of it is circulated through the radiator - It's much easier for the water to flow right back into the engine (because the WP is pulling it out, creating lower pressure).

So, while a better radiator and t-stat holes are great improvements, if the above is true, they alone might not solve the issue (under conditions where the bypass is open for extended periods).

[Mr Blue]

You might want to consider Pete's suggestion of larger water pump pulley to raise the bypass to 6100 RPM. I don't know what the low RPM flow will be... might be acquiring a different problem.

[secondchance]

I do not see Dewitts Radiator in you signature??

Which Dewitts Radiator are you using and where did you get the Dewitts Radiator?

I know you are asking Daryl but in my case I got 1139090M - double row/manual. These are $495 plus $50 shipping direct from Dewitts. However, the same radiator on Ebay put up by Summit Racing showed up at $495 including shipping.
It's a good quality unit.

[A26B]

Appreciate all the responses.

The main reason I started this thread was because I've read posts suggesting that once the bypass is fully activated, the coolant is going to follow the path of least resistance and therefore not much of it is circulated through the radiator - It's much easier for the water to flow right back into the engine (because the WP is pulling it out, creating lower pressure).

So, while a better radiator and t-stat holes are great improvements, if the above is true, they alone might not solve the issue (under conditions where the bypass is open for extended periods).

Russ,
The bypass is NOT an open or closed only valve ("snap valve"). It is spring loaded and starts to open when the back pressure in the stock radiator reaches a specific point called "crack pressure," i.e. a "throttling" type valve. For conversation sake only, lets assume that point is reached in a stock cooling system at 5500 rpm and the t-body bypass valve spring requires 5psi to move the bypass valve "off-seat".

At this point things begin to happen, 1. back pressure is maintained at 4 psi, which is the amount of pressure required to exert 5 lbs force, the force required to initially lift the bypass valve off seat.

If rpm is constant, a point of equilibrium exists and the bypass valve is allowing some amount of coolant to "bypass". Let's just say the T-Stat bypass aperture is at 10% of full open capacity. Further assuming that the water pump discharge flow rate is 75 gpm and 90% of that flow, 67.5 GPM, is going through the radiator and the balance, 7.5 GPM, is being bypassed

As rpm increases, flow rate increases, back-pressure increases and the t-stat bypass valve responds accordingly and at 6,000 rpm and Pump discharge is at 85 GPM. The additional flow rate is going to generate more back pressure and the bypass will open further, allowing the added volume to bypass. The flow through the radiator will remain relatively constant at pressures great enough to open the bypass valve.

This process continues until the water pump reaches its maximum GPM output which is not linear with RPM, i.e. the pump may reach its maximum flow rate before maximum rpm, depending on several factors.

Please remember that the values I used are for demonstrative purposes only and are not representative of actual or theoretical values.

The cooling system back pressure can be raised by increasing the flow rate through the radiator & thermostat, such as a Ron Davis Racing Radiator and the drilling of holes in the thermostat flange. It should be noted that removing the thermostat entirely may be counter-productive to overall cooling efficiency. There is a balance in the velocity of coolant through the radiator and air quality/velocity, to achieve the best heat exchange.

I agree with you, the fans would be most useful during cool-down at slower speed.

[A26B]

Re: Slowing down the stock Pump or adding an electric pump.

Reducing the coolant flow rate to impede or retard the bypass valve opening is not going to do anything to provide the additional cooling needed to compensate for the additional heat generated by running the engine at higher power levels.

The cooling limitation is the capacity of the heat exchanger/radiator. What is needed is more capacity, not less water pump volume. There's a lot more to cooling the LT5 than what goes on outside. The flow rate needs to be high enough to "scour" steam bubbles from hot spots.

Big pulleys & electric pumps are fine for more horsepower, removing parasitic engine drag, but they don't yield more cooling capacity.

[gbrtng]

At 70~150mph, I don't think the fans are going to be needed, but if they are, you can always add them later.
I thought the stock calibration turned both fans off above 40 MPH.
Correct me if I'm wrong ...

[A26B]

I thought the stock calibration turned both fans off above 40 MPH.
Correct me if I'm wrong ...

That may very well be true, I don't know about that. My comment about fans was referring to the addition of aftermarket fans. Thanks for pointing that out though.

[GOLDCYLON]

I do not see Dewitts Radiator in you signature??

Which Dewitts Radiator are you using and where did you get the Dewitts Radiator?

Im losing track of ALL my mods. Its the all aluminum 2 row replacement with the SPAL fans and from Dewitts

[cvette98pacecar]

I have the same setup as Jerry. I drove the car hard for 6 days straight above 5500 RPM for hours on end and had no issues. Ron Davis Radiator, Stock thermostat with 3 small holes drilled to reduce back pressure to keep the antifreeze flowing through the radiator.

[Dynomite]

I have the same setup as Jerry. I drove the car hard for 6 days straight above 5500 RPM for hours on end and had no issues. Ron Davis Radiator, Stock thermostat with 3 small holes drilled to reduce back pressure to keep the antifreeze flowing through the radiator.

I am thinking the radiator allowable pressure is increased with the Ron Davis (structural capacity of the radiator) or the Coolant flow resistance is decreased such that greater Coolant Flow will not contribute to higher radiator pressure. In the case where the Radiator has greater burst pressure capacity it would be time to increase the Return Spring Pressure on the Thermostat dis-allowing some Coolant to return directly to the engine. In the former case where the Coolant Flow Resistance is decreased through the Radiator, nothing would have to be done to the thermostat to realize the benefits of the larger capacity radiator.

Ron Davis Radiator w/o transmission cooling

Coolant temperature stays at a constant 185 deg (70 deg F ambient) with 180 deg thermostat.*
a. 1989-1996 C4 Type V8 All Part No. 1-16CV8996
b. Rated 800 Hp
c. Manual transmission
* Coolant Temperatures will climb a bit with AC on (100 deg F ambient).

http://i287.photobucket.com/albums/ll142/dynomite007/B%20Engine%20LT5/RonDavis_zps884504b8.jpghttp://i287.photobucket.com/albums/ll142/dynomite007/Dynomite12/8bd68add-fcb2-4c2e-abf0-c1ed7f69573b.jpg

[grahambehan]

I'll just leave this here.

[RussMcB]

Graham, thanks for joining the conversation.

I must admit, I'm not sure what the first graph is conveying.

I *may* understand some of the second attachment. It seems to show a dangerous situation at 6166 RPM, then (as the RPMs rise and the bypass opens), things get safer (from a pressure and HP point of view, but at the sacrifice of less coolant going to the radiator). Am I reading that right?

Hmm. Page 2 mentions cavitation. I'm guessing that can cause near-total lack of flow and possible engine harm.

Graham, what would you do to prep an LT5 cooling system for road racing (in addition to a better radiator)?

BTW, I talked with a couple of DIY Tune guys at Road Atlanta. They seemed impressed with your "next phase" LT5 project and were happy they were involved.

on edit:
It just dawned on me - Our (and all) cooling systems have a blow-off valve in our radiator caps, usually rated at 12-16 lb. How does that come into play? Are we pushing coolant out (via the cap) at 6166 RPM (and then hopefully pulling it back in when pressure drops)? Is that too insufficient to relieve enough pressure to save a radiator from bursting?

[grahambehan]

The first graph shows electric water pump flow vs press, typically the ratings on these pumps are against free air discharge, once some restriction and therefore pressure differential is present their "advertised" flow numbers diminish.

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.

Jerry's recommendations, earlier in the thread have proven to work well for track use.

The pressures are measured on the block side of the system.

Graham.

[5ABI VT]

Maybe I missed it but I find it odd after 24 hr record runs there's an issue with continuous high rpm use? What changes did they make to the car used in the record run?

[RussMcB]

The WRR was done with relatively lower RPM's.

From http://www.zr1netregistry.com/Information/PerformanceRecords/WorldRecords.aspx:

"With headers, open exhaust and engine controls calibration revised for racing gasoline, horsepower was 400-410. Tests showed the 190 mph necessary to reset the "24" came at 5500 rpm in fifth, so the gas pedal had a stop at 70% throttle. The car had transmission and rear axle coolers and 3.07 gears replaced the stock 3.54s."