legacycentral bbs

In order to correctly size my heat exchanger radiator, I attempted to calculate the heat production in a turbo.

I came up with:

n = PV/RT (ideal gas law)
29 g/mol (molar weight of air)
723 J/kgK (specific heat of air)
E=c*m*t (heat energy calculation)

A vf34 puts out around 430 CFM at 14.7 PSI, which is about 200 litres per second. It puts it out at around 400 degrees kelvin. The absolute pressure is around 200 kPa

That puts the heat production of this turbo at that air pressure to be 50,000 watts

Thats 67 horsepower its sucking up to compress that air.

Does that seem right to you guys? Or have I missed something?

Hmm, are you planning on getting a vf34?

What kinda boost are you looking to run, I mean, its not gonna always heat the air to 400 degrees. If its out of its efficiency range it may be adding even more heat.

What kinda intercooler are you looking to run? A front mount?

Ive got a Deadbolt prepped VF34

Im running an Air/Water IC, trying to figure out how big my rad should be.

14-17 pounds of boost, probably.

What Air/Water intercooler are you going to use?

The stock JDM legacy.

Im using a coolant pump from a VR6

Well, in that case here is how I see it: You are gonna want the biggest but most efficient radiator you can get right? So its not a matter of how much your turbo is heating the air but how much heat you can take away.

I would look into the heat exchange efficency and design of the radiator. If you dont already know about all that stuff, try and look up info on what makes a good radiator and how thick it should be.

And then you need to make sure your coolant pump is going to be able to move the water fast enough. So to sum up all that I just blabbered out;

If you are going to get a custom radiator unit, find out how big you can go, where to place it, how well the pump you have will flow, and how much it will cool the water before reentering the AWIC.

So I would suggest on trying to create the most efficent coolant system you can instead of trying to figure out the specific size of the radiator, because you are going to want to cool the air as much as possible. Maybe go look at what other AWIC's use for a water cooler so you can get some idea. What did that AWIC come with originally?

The entire capacity of the stock AWIC system is like 2.1L or something stupid like that.

The reason I dont want to go for the biggest custom radiator I can get and fit is cost. Also, I want to it interfere with the engine rad as little as possible.

So if I can get a radiator with a cooling capacity of say, 70kW, and the turbo puts out 50kW, I should be ok.

At least, thats how its looking in my mind.

I see what you mean, and thats an evident constraint for most people. Well then it seems like you are on the right track, I'd try to find some info on that turbo on its efficiency and whatnot. And recheck your math to just in case.

How are you getting your radiator? Is it going to be custom?

Also, are you keeping your AC radiator? If you pull that off you will have plenty of room for another cool in there.

Yea, getting a custom one made.

The AC condensor is gone.

I sort of went through when looking at mine.

The question I have for you is, if you're getting a custom one made, are they going to be able to tell you its heat transfer capacity?

The next thing you need to look at is the sizing of the radiator based upon the cooling capacity of the intercooler.

The stock AWIC has a cooling capacity of 3,954 kW or 13,491 BTU/hr.

The stock radiator has a cooling capacity of 5,408 kW or 18,451 BTU/hr.

I am assuming these capacities are for the given pump flow rate of 15 liter/min or 4.0 gal/min with 2.0 m or 6.6 ft of water head.

If you bump up the flow rate, the cooling capacites of the intercooler & radiator will increase.


I'd have to double check your calcs, but if the cooling capacites are what I listed above, then I think your number is a little on the small side.

If I get time tomorrow or sunday, I'll see what I can come up with.

I have to talk to the guys at the shop, but if I can find out what percentage of waste heat the average car loses through the block (as opposed to the exhaust), I can deterine the size of radiator I need based on an equivalent sized engine (i.e. if an engine lost 1/3rd of its waste heat through the block, I'd need a rad big enough for a 200hp engine)

Just for my clarification, you are looking for a separate radiator for your intercooler system correct, and are not looking to combine radiators?

Correct.

Something that'll fit into the AC condensor location, most likely

Just based upon the size, that should be plenty.

I still haven't had any time to crunch numbers....sorry.

I am a little lost on what your getting custom (engine rad and/or intercooler exchanger?) but...

A while ago I was looking into increasing my heat exchanger effectiveness and found Mustang Cobra heat exchangers at reasonable costs... and Cobra upgrades as well (not as reasonable). All had dimensions that seemed workable for the lower half of the bumper opening.... 27" long x 7" tall x 1.5"thk or so.

sorry I have no input on your calculations.