Educate me please. Intercoolers.

This may seem like a dum question, but I just have to know:

I have never really thought about this until my brother asked me how an intercooler works. I don't know exactly how it works, but understand the principle of cooler air being denser which means more air can be forced into the turbo charger.

But how does it work? The 930 intercooler looks much like any other oil/water cooler which of course cools a liquid flowing inside it. Here we're talking air coming from the outside of the car. How is the air cooled and how is it trapped and forced into the turbo charger? Could someone please explain this to me?

[k9handler]

damn just when I though I understood how the intercooler worked, you make me realize I may be completely wrong! Ha Ha But I really don't even understand the turbo competely either.

I thought the heated air from the turbo was cooled by the intercooler on it's way to the intake? I have no idea...damn, now I will have to find out cause you have asked a very good question. Thanks, I will follow up on this.

[tryan]

the path of the air used in the motor is sucked from the atmosphere, through the air filter, through the turbo,through the intercooler and then into the intake and motor.


freshman chemistry. when you compress air, you heat it. the intercooler is used to cool the "heated" air. an intercooler is used to keep the cylinder temperatures down.

the air that flows over the intercooler is not mixed with intake air.


in the case of my power stroke, the intercooler is used to hold all the oil that blows out of the block vent . junk.

[carmad]

When the air is compressed by the turbo it heats up, and becomes less dense. It then passes through the intercooler,which cools it using the outside ambient temperature as the cooling medium, air/air intercooler. That is why you see huge intercoolers on modified turbo's, larger surface area for heat transfer.
Porsche did use air/water intercoolers on some of their race cars.

[k9handler]

ok...so I was on the right track, great answers guys.

Ahh now I get it Thanks for the lesson.

[Kemo]

Quick side question:
Since the exhaust spins the turbo, would that add some heat as well, aside from the compression portion of the equation?

[Emission]

The turbo does restrict the flow of exhaust. The smaller the turbo, the more restrictive (in the case of the 930, the turbo is quite large so restriction is minimal). This may cause the engine to run a bit hotter.

In addition, the turbo 'bearings' do get hot from spinning, but (hopefully) the oil lines that run directly to it will keep them relatively cool.

On the 930, the intercooler sits above the engine. When the engine is running, fresh air is pulled through it by the engine fan. When the car is parked, the hot engine quickly heats the aluminum intercooler (like a huge heatsink). Mine takes a few minutes of driving before it becomes effective again - and there is a huge difference between a hot intercooler that was parked and an intercooler on a cold night on the highway!

[dean]

Yes there is some heat transfer from the hot side to the cold side, but it doesn't really matter because the charged air is cooled by the cooler. Engine driven superchargers don't have this heat transfer problem.

[RarlyL8]

The exhaust heat contributes minimally to the heat of the air being pulled into the turbo.
The heat is caused by compressing the air - lots of heat. When you see pictures of red hot turbos you are seeing the result of boost pressure vs time. The exhaust of a normally aspirated engine does not typically get red hot.

Supercharging also produces lots of compression heat. Intercooling must be used on high boost motors to prevent detonation. Those blown big blocks on magazine covers are mostly garage or track queens. A massive cooling system would be needed to run them on the street.

COLD DENSE AIR = HORSEPOWER

[cstreit]

See this article for basic information...

http://www.howstuffworks.com/turbo4.htm

Try the Garret Turbo-chargers website for more detail.

[Overpaid Slacker]

Mikkel -
Great question, actually.
Allow me to second Chris' recommendation and refer you for the how the turbo works section to: http://www.howstuffworks.com/turbo.htm
The intake charge is compressed by the turbocharger, which is supposed to make a positive pressure in the manifold (upstream of the intake valves) which usually works at a partial vacuum.

Having taken the intake charge from what would be just under atmospheric pressure and compressed it (ie more fuel/air for the same volume), you've caused it to expand -- like the reverse of adiabatic cooling that occurs when you release a gas that's under high pressure -- please, engineering geeks, cut me a break with this explanation.

The intercooler is an air-to-air heat exchanger, with the intake charge on the inside and the atmospheric air on the outside -- trading heat from the intake charge to the atmosphere, cooling and further densifying ( that word is the result of half a bottle of Tanqueray) the intake charge. By way of reference, a radiator in a water-cooled automobile is a water-to-air heat exhanger, cooling the coolant water with the atmosphere. Now, water doesn't expand/contract nearly as much as air when subjected to temperature differences, but that's the beauty of an air-to-air intercooler and the effect on charge density.

Not to confuse issues here, but one of my soon-to-be-drafted projects is to add water injectors to my intercooler (spraying water onto my intercooler), in order to improve the efficiency of my Kokeln and add a few more hp....

Check out the following site for some tech. data re: intercooler efficacy: http://www.kokeln.com/products/911turbo_7689/intercooler.shtml

Best,
JP

[RickM]

I've seen guys packing ice on their intercoolers before a 1/4 mile run. To me this seems to be of little value. I'd think that thehot compressed air would quickly heat the intercooler back up. Is this a correct assumption on my part?

Rick

[47silver]

that is a good idea jp, you will be taking advantage of evaporation effect of the water,
we use cooling towers called evaporative coolers, they have convection, (rely on temperature differential for air movement, induction (they have a fan that blows air across the coil) and evaporation, a pump pumps water over the coil it is very efficient but you will use a lot of water, you may put a sump on the coil to catch the water and a pump to scavege the water and pump it again over the coil. when the oat is high and humidity is low you will use mucho water.

[pjv911]

To answer that question, a discussion of thermodynamics is involved.A turbo compresses an engine's intake air. By laws of physics, compressing air also heats it. For a combustion engine, heating the intake air is a bad thing. For one, it raises the combustion chamber temperature and thus raises the likelihood of detonation. Another bad thing is that air expands as it is heated. So in other words, it will lose some of the compression effect and the turbo must work harder to maintain the desired level of compression.
Thus enters the intercooler into the equation. An intercooler is a heat exchanger--sort of like a radiator except that it cools the charge (your intake air) . Now that the charge is being cooled, two benefits appear: combustion temperatures decrease (along with the likelihood of detonation), and the charge becomes denser which allows even more air (21% oxygen) to be packed into the combustion chamber. Exactly how much heat is removed varies greatly; some factors include the type of intercooler used, its efficiency, and its mounting location. From what I've seen, getting your intake charge temperature within 20 degrees of ambient(outside air temp) is excellent; consider this a practical limit (meaning you might get closer but not without spending tons of money) for a street-driven car. If anyone has any other turbocharged related questions fire away. This is my area of expertise.

Kurt Williams


BTW RarlyL8 your responce was on the money.

[Overpaid Slacker]

Rick -
Although I don't know about icing my i/c, I suppose in short bursts what it could do is artificially lower ambient temperature and create a larger delta-T (difference in temperature) between the charge and the (artificially lowered) ambient air, resulting in lower charge air temperatures - and therefore denser charge air.

This is something hp nerds have been working with forever -- witness the ram-air systems of 60's muscle cars -- taking air directly from outside the hood into the carburetor (rather than intake air that's run in through the grille/radiator and been heated up/expanded).

47Silver --
I just figured a couple-of-gallon tank of water/antifreeze with a H/D washer fluid pump, shooting onto the i/c -- just to see what would happen; other than shorting out my ignition, hopefully. Nothing too premeditated (read: "scientific") at this point....

Kurt -
I just moved into Slow-folk county from NYC, and though my 930 is up for the winter, we ought to get together out here for beers or other adult beverages sometime.

'Night all...

JP

[pjv911]

Sounds like an idea JP . My car is up for the winter as well.

Kurt Williams

[cstreit]

If you don't want to build you own, check out

www.seinesystems.com

[47silver]

chris
thanks for the link the water mister looks like it would do the job and it has a 2.5 gallon resevouir. i guess they could give an idea of water useage.
gary

[RickM]

If you rig your own water delivery system I have an idea for the mister component. (Please don't laught but...) at Sears I've seen "personal" misters that are comprised of a coiled tube (which can be bent to accomodate any position) and a Stainless & brass misting nozzle. The are very inexpesive but designed to deliver a very fine mist. I can speak for the heat tolerance of the tubing but the business end of the mister could be useful. Nozzles can also be purchased separately for a couple of dollars.

http://store6.yimg.com/I/mistymate_1703_346069

Look for "Twist & Mist" on the page