improve on dual cooling

[crammit442]

I think you guys misunderstood me some. If you are cooling the engine, the engine is heating the water. The heat has to go somewhere which is from the heated combustion gases to the engine metal then from the engine metal to the to the water in the engine.

True if you wanted really hot water, you would keep it in the engine longer. My point was more along the lines of which scenario was better.

A lot of water running through the cooling system where the contact time between the water and engine is less.

Or a longer contact time between the water and the engine.

There are many factors that can play into this such as water density (salt or fresh), dual cooling (changes water velocity), water temperature, ect...

That is why I was going to find what formula would be used to calculate the heat transfer energy where I could vary the formula parameters and see which had the biggest effect on the final result.

Speaking of cooking foods on your engine, did anyone watch the Winter X games where teh guy was lookign for a muff pot? Look on espn.com videos for the explanation

I understood what you were saying, but if you think it through a bit further you'll see that the "leave it in the motor longer for greater cooling" idea looks ok superficially, but has no merit.:bigok:

 

[Freakrider]

Question for Supertune: Do you run both pump cooling lines to the exhaust manifold or one of them to cool pipe only and one split to both sides of manifold ? Also one guy in this thread is going to try reverse cooling by sending water first to the head (on a spare motor)...anyone ever try this and could it even work ? thx...

 

[SuperJETT]

True if you wanted really hot water, you would keep it in the engine longer. My point was more along the lines of which scenario was better.

A lot of water running through the cooling system where the contact time between the water and engine is less.

Or a longer contact time between the water and the engine.

You're still missing the point.

Higher flow will transfer more heat out. Colder water will transfer more heat out.

Warning: physics ahead

Here's what you're looking for I think, but you'll see there isn't much to it.

heat transferred = mass flowrate * temp difference (there are some constants that factor in but they don't apply here)

This would be the water side only. The engine side is just going to be heat transferred to the water jacket, fluid flow doesn't apply.

Let's say the engine in in steady state operation at 5000rpm and flowing 20gal/min, and we want to maintain the running temp and the river/lake/ocean is 70F and our exit temp is 120F right where it should be.

(btw, I'm not doing exact calculations/units here, but the equation is correct)
heat transfer = 20gal/min * (120F-70F)
heat transfer = 1000

So, 1000 units of heat transferred keeps us at 120F out. If we stick a restrictor in to drop the flow to 15gal/min then
1000 = 15gal/min * (xF - 70F)
xF = 1000/15 + 70
xF = 136.7F is our new outlet temp

However, that means closer to where the water exits the engine, the engine temp is going to be hotter than it was.

If you double the water flow to 40 then
xF = 1000/40 + 70
xF = 95F

The engine will be colder than before even though it's still creating the same heat inside, it's just being carried away faster.

I could get into more detail but it's hard to explain via typing. One other thing is you do want to maintain good pressure to prevent/minimize localized boiling in the head which can cause hot spots/detonation.

 

[SUPERTUNE]

Jump On iT,
On a 'B' pipe system, I run both cooling in lines to the bottom of ex. manifold and 2 out on head, one feeding headpipe, one feeding pisser out. Just normal setup. Just make sure you have the piston clearance set correctly, not too tight for high performance applications.
I re-invent the setup with other stuff...

 

[McDog]

Posting so I can find this thread for Chuck's setup in two months when I set up my cooling.