Intercooler questions (kind of long)

[YellowMaranello]

Just a couple of questions on intercoolers. Answer any of them as you see fit. Also, if anyone has a picture of a cross-sectioned intercooler, it would help me out greatly, as I'm not exactly sure what an intercooler looks like on the inside and it would help me out greatly to understand the airflow through the intercooler itself.

1. Would an intercooler be more/as/less effective if it was like this, as opposed to the longer, traditional way?
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2. An intercooler is placed so the the air goes through it after it goes through the compressor section of the turbo (correct me if I'm wrong, please)? What if you put the intercooler as part of the turbo's intake, so that the air travelling from the compressor would have a more direct route to the cylinders, because it wouldn't having to go through the intercooler (because it already did)? Or, what if you put one before and after the turbo?

3. Not really a question, but looking for oppinons on it. Say we have a rear-engined, turbo'ed car. Now say that we want to use a MASSIVE intercooler, and the only place it will fit, is in the front of the car. The problem with that is, getting the air from the turbo in the back of the car, to the front and through the intercooler, and back to the back of the car. I think that it would tak too long to get the air back to the engine, and there would be WAAYYY too much turbo lag. This is where my #2 question comes into play. What if you used that setup? As is, the intake starts at the front of the car. So the air hits the intercooler before it hits the turbo... Would it work?

4. Intercoolers are generally flat. What about if they were made more cube-like? Would it be more effective? I think the F40 has more boxy intercoolers now that I think about it....

5. What if the 2 pipes that went into the intercooler (technical term?) were closer so the ends of it? like this (requires an intercooler like the one in my first question):
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6. Should question 5 work without too many disadvantages, then on a mid or rear engined car, then why not put a huge intercooler in the roof of the car?

[454Casull]

Originally posted by YellowMaranello
Just a couple of questions on intercoolers. Answer any of them as you see fit. Also, if anyone has a picture of a cross-sectioned intercooler, it would help me out greatly, as I'm not exactly sure what an intercooler looks like on the inside and it would help me out greatly to understand the airflow through the intercooler itself.

1. Would an intercooler be more/as/less effective if it was like this, as opposed to the longer, traditional way?
|------------|
|------------|
|------------|
|------------|
=|------------|=
|------------|
|------------|
|------------|
|------------|

2. An intercooler is placed so the the air goes through it after it goes through the compressor section of the turbo (correct me if I'm wrong, please)? What if you put the intercooler as part of the turbo's intake, so that the air travelling from the compressor would have a more direct route to the cylinders, because it wouldn't having to go through the intercooler (because it already did)? Or, what if you put one before and after the turbo?

3. Not really a question, but looking for oppinons on it. Say we have a rear-engined, turbo'ed car. Now say that we want to use a MASSIVE intercooler, and the only place it will fit, is in the front of the car. The problem with that is, getting the air from the turbo in the back of the car, to the front and through the intercooler, and back to the back of the car. I think that it would tak too long to get the air back to the engine, and there would be WAAYYY too much turbo lag. This is where my #2 question comes into play. What if you used that setup? As is, the intake starts at the front of the car. So the air hits the intercooler before it hits the turbo... Would it work?

4. Intercoolers are generally flat. What about if they were made more cube-like? Would it be more effective? I think the F40 has more boxy intercoolers now that I think about it....

5. What if the 2 pipes that went into the intercooler (technical term?) were closer so the ends of it? like this (requires an intercooler like the one in my first question):
|-----------|
=|-----------|=
|-----------|
|-----------|
|-----------|
|-----------|
|-----------|
|-----------|

6. Should question 5 work without too many disadvantages, then on a mid or rear engined car, then why not put a huge intercooler in the roof of the car?

An intercooler won't do anything upstream of the turbo, as the air is at ambient temp. Only after it is compressed does it need to be cooled.

With those setups that you drew, I think there would be way too much pressure drop, and low cooling efficiency.

[replicant_008]

1. Generally, the longer distance the air has to travel across the intercooler then theoretically it is exposed a greater cooling surface area (which increases the efficiency of the intercooler in cooling the charge.)

2. The purpose of the intercooler is to reduce the temperature of the compressed air (compressing air adds heat like a bicycle pump gets warm). The warmer the air the less dense it is - reducing the temperature of the charge (ie the compressed air) increases its density and provides more oxygen per a given cubic volume of air. This in turns increases the efficiency of the swept volume of the engine.
Putting an intercooler in front of the turbo would be better than no intercooler at all but as the ambient air entering the turbo will about the same as the cooling air flow the intercooler will have a limited effect. Placing the intercooler after the air has been compressed (ie the charge temperature > ambient temperature) is more efficient.

3. See 2 - you'd have to experiment but in theory even a massive intercooler mounted before the turbo would be less efficient that one after the air is compressed. Why not use a side pod/side entry for the air or side entry for air and mount the intercooler above the engine?

4. Intercoolers are usually flat to maximise the cooling effect of the airflow in the same way radiators are this shape. As the air passes through a heat exchanger (eg intercooler/radiator) the air is warmed and less able to provide the cooling effect. Having a flat shape enables the maximum cooling area for a given cubic volume.

5. In theory, the intake to the intercooler should be at the top and the outlet at the bottom - I guess this encourages the air to travel throughout the intercooler rather than creating a short path between the inlet and outlet.

6. The air passing over rather than through the intercooler is probably less efficient is terms of airflow.

Hope this helps...

[arcadiabc]

Reasons why you want to install and intercooler after the Turbo is due to the fact that the pressurize air is hot and needs to be cooled. And why do we need to cool the air? because of heat buildup and the cooler the air the more it can be compress when it reaches the combustion chamber allowing more air to be pack inside the cylinder.

[ales]

Originally posted by arcadiabc
Reasons why you want to install and intercooler after the Turbo is due to the fact that the pressurize air is hot and needs to be cooled. And why do we need to cool the air? because of heat buildup and the cooler the air the more it can be compress when it reaches the combustion chamber allowing more air to be pack inside the cylinder.

I'd have to say not quite. When you pu the IC between the compressor and the engine, you actually lose somewhat in terms of pressure (the internal volume of the intercooler is wider tahn a pipe). But you gain more in the density of the air (as was noted before) and you gain more by that than you lose by a slight decrease in pressure. So to summarise it - with the IC you actually have a bit less air in your cylinder, but the air that you do have there is denser and is more efficient than the larger volume of air straight from the compressor.

Alex

[SaabJohan]

A few more reasons to use an intercooler:
Colder inlet air temperature means colder combustion and cooler exhausts. This means that it will be harder for the fuel to knock, and the lower temperature means less stress on the exhaust valves and turbine. A lower combustion temperature also means that there will be less NOx in the exhaust.

But remember that the air can be too cold also, if that happende there will be a problem to get the fuel to vaporise. This can however be solved with an intercooler bypass function.

[ales]

Originally posted by SaabJohan


But remember that the air can be too cold also, if that happende there will be a problem to get the fuel to vaporise. This can however be solved with an intercooler bypass function.

Could you please tell more about this?

Alex

[SaabJohan]

Heat energy is needed to vaporise the fuel. Fluids don't burn you know, gases do. So if we want a combustion to occur in the cylinder we must have an mixture of vaporised fuel and oxygen there. To get the fuel to vaporise heat from tha intake air is used, how much heat neccesary depends of which fuel is used and of course the amount of fuel injected.
The vaporisation will cause a drop in intake air temperature and if the fuel used have a high "heat of vaporisation" you will need less or maybe no intercooling (like the CART engines which run on methanol).
"Vapour pressure" is a measure of how much the fuel will vaporise at a mentioned temperature.

If the vaporisation is poor you can inject more fuel to solve the problem (like when the engine is cold), but this is not a good idea since we want high effiecy and much power from our engine. So if a intercooler is used a simple bypass valve controled by intake air temperature can be used to let uncooled air by the intercooler and on that way increase the intake temperature.
But to get too low, really large and effective intercoolers must be used.

On Hondas old turbocharged F1 engine it's intercoolers could reduce the intake temperature to 36 C but the ic bypass increased it to 40 C. In a later more efficient but less powerful engine a intake temperature of 70 C was used (also increased CR, less boost and heated fuel), this engine is still today the most efficient F1 racing engine in history with it's 32% effiency.

[YellowMaranello]

Thanks for all the help guys, its been most enlightening. Another question:

What about twin intercooling a single turbo? Like, what if you used front mount intercooler AND one on top of the engine that uses a hood scoop (technical term for this kind of intercooler?)?

[SaabJohan]

Originally posted by YellowMaranello
Thanks for all the help guys, its been most enlightening. Another question:

What about twin intercooling a single turbo? Like, what if you used front mount intercooler AND one on top of the engine that uses a hood scoop (technical term for this kind of intercooler?)?

Two intercoolers can be used, but I don't recommend an ic on the top of the engine using a hood scoop if the car have the engine in the front. Remember that all air that goes in must came out, and many times this air is going down under the car and that is bad.

If it's tight about space, use a watercooled IC instead.

[YellowMaranello]

Originally posted by SaabJohan


Two intercoolers can be used, but I don't recommend an ic on the top of the engine using a hood scoop if the car have the engine in the front. Remember that all air that goes in must came out, and many times this air is going down under the car and that is bad.

If it's tight about space, use a watercooled IC instead.

Lets say we had a WRX, do you feel that it would be better to use a front mount intercooler instead of the top mount, and then replace the hood so you no longer had the scoop there? I'm just wondering...

[SaabJohan]

Originally posted by YellowMaranello

Lets say we had a WRX, do you feel that it would be better to use a front mount intercooler instead of the top mount, and then replace the hood so you no longer had the scoop there? I'm just wondering...

I think that the best solution here would be to put the IC in the front and build air outlets in the hood. In that way all hot air that is led through the IC will be evacuated and will also help to create downforce on the front wheels. Also, the enginebay will not be ventilated with hot air from the IC. This arrangement can for instance be found on HKS:s Altezza.

[YellowMaranello]

Originally posted by SaabJohan
...and many times this air is going down under the car and that is bad...

Back on this subject... Could there be a way to funnel the air that is going under the car in a way to create downforce? I know that there are diffusers on the bottoms of some cars that create downforce (not quite sure how, but I'll figure that out later somehow), like on the Lotus Elise.

[ales]

Here is something that will help you understand aerodynamics and other aspects of cars as well http://www.mulsannescorner.com/ Make sure to check out the links section.

And here are a couple of articles on aerodynamics:
http://www.atlasf1.com/2000/feb16/gray.html
http://members.tripod.com/~del_jones/f1_tn.htm

Alex

[YellowMaranello]

Excellent links. Thanks a ton! And thanks to replicant, SaabJohan, 454, and arcadiabc for all the info. I think I'm done asking questions for now, but I can assure you I'll be back later.