Electric Water Pump questions ...

[RussMcB]

Originally Posted by 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.

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.

Originally Posted by XfireZ51

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

Good point.

Originally Posted by Kevin

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

Yea, 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]

Originally Posted by 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.

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]

Originally Posted by 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.

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]

Originally Posted by Dynomite

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]

Originally Posted by 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).

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.