Hey all,

Looking to do some calculations on my cooling system to determine if it will handle the HP.

Any know what % of the heat is transferred from the heads to the water and what % is through the block?

I was estimating a 75/25 split heads/block but would like other opinions.

Thanks,
Ben

 

I don't even know how you'd arrive at separate numbers for a closed system like that. Sorry....

 

What kind of HP are you running?
What exactly are you considering, a larger radiator, water pump??

BTW looks like a fun combo in that RX7..

 

Sounds like I need to add some clarity. We have 2 separate temp sensors on our engines:

One sensor is located on the WP and monitors the water temperature from the engine after it has passed through the heads and then the block (NOTE: this is an assumption and can anyone absolutely verify?). This can be read via data logging software.

The second sensor is located on the heads between cylinders 1 and 3. I have this set up to a digital gauge to give me as high a resolution as possible.

If I know what the split in heat transfer is between the heads and block, I can then calculate my real inlet temperature of the coolant to the engine. As it stands, I am not reading the true inlet temperature but the temperature after the water has passed over 1 cylinder.

Example: right now while cruising, I am reading with the datalogger a temperature of 194 and a head temperature of 185. This is a delta T of 9 but not a true delta T which allows me to calculate water and air flow requirements.

I need to see if my current setup can handle the 450 RWHP I will be doing at the track...road racing so this is not a drag run and done.

I hope this helps.

Thank you.
Ben

 

The heat generated in the combustion chambers leaves the engine via three different paths - some converted to mechanical energy via the crank, some out the exhaust and some through the coolant. How are you going to divide the BTU content of the fuel between those three paths?

There is an SAE paper that goes into some details on the design of the LT1's reverse flow colling system. It has a diagram that shows the "Bore Temperature Distribution", and another that show "Coolant Temperature Gradient" from the front to the rear of the engine. Also charts showing the water pump flow vs. (pump) RPM, and the split of water pump flow in GPM between the left and right sides of the engine, and the heater core. There are also diagrams of the block, heads and water pump, with detailed flow arrows.

The difference in bore temperature as a function of height is fairly linear, and covers a range of about 6*C. Variations are plotted as a function of "inboard" and "outboard" surfaces of the bore. The part of the cylinder bore facing inward is about 1*C warmer than the part of the bore facing outward. The block temperature, as a function of cylinder number, varies by about 3*C, from #1 to #7, and the head temperature varies by about 5*C from #1 to #7.

Might be worth getting a copy if you plan to attempt to calculate heat load to the radiator. Paper is #920673 and can be purchased online from the Society of Automotive Engineers. I think its $15. You authorize the money against a credit card, and they e-mail you the file. Does not require being a member of SAE. The paper is 30 pages, and while most of the pages are devoted to the cooling system, there are sections on lubrication, mechanical components, head and valve train, the Optispark distributor, fuel injectors, idle air flow, etc. Since it was written in 1992, it describes the Corvette engine in detail.

One interesting thing is the claim that ".... this system automatically dearates the engine continuously by offering a free coolant surface to the heater retrun line." The Corvette cooling system incorporates a pressuized coolant reservoir, at the high point in the system, in order to prevent problems with air in the coolant system. Guess the F-Body engines got the short end of that stick.

 

A good read on cooling systems can be found @ Summitracing.com by HP books. Author: Ray Bohaz. It also has much data on cooling media. From that source, the thermal break down is around 20% rad cooling, 20% torque/ power generation, 60% exhaust waste. I used Ray's book to help mod my cooling system to Evans waterless. evanscooling.com also has good information on IC engine thermodynamics and heat transfer. Also, some history of the gm reversed cooling. From my use of Evans (2 years), it has helped my FI application, and, I will not return to water-glycol media. B.