Intercooler FYI

[BryanPendleton]

Part I

An intercooler should be considered an integral part of any good turbo kit. While it may not be necessary for a low boost application, I would still highly recommend it. The two main considerations when selecting a properly sized intercooler is of coarse it's effeciency and the pressure loss between the intercooler inlet and outlet.

One of the most obvious characteristics of a good intercooler is how well it cools the intake air. This characteristic is generally represented by the intercooler's effeciency, and naturally the more effecient the intercooler there better it is.

The pressure drop across the intercooler should also be considered. I would highly recommend that the pressure loss be minimized to at least 2 psi or less. Now, why is this pressure loss bad? Lets say you want to run 15 psi of boost, and your intercooler has a pressure lose of 3 psi. So you set your boost controller for 15psi and you only get 12 psi of boost at the intake manifold. You still want to run 15 psi, so you have to set the boost controller to 18 psi to get 15 psi at the manifold. Sounds simple to simply bump the boost up, but you have two problems with this. First of all, you have effectively increased the air charge temperature coming from the compressor and two you have increased the exhaust manifold pressure (backpressure). Though your intercooler may be more efficient than one with a lesser pressure drop, the above intercooler now has to cool the aircharge from a higher temperature, so in effect you could have a less efficient intercooler with a 1 psi pressure loss that could cool the intake charge to a cooler temperature than the 3 psi loss intercooler, because you would only have to set the boost controller at 16 psi to get you 15 psi of boost, which would have reduced the compressor outlet air temperature from the 18 psi setting. Similarily, with the lower 16 psi boost setting the wastegatewill be open more, relieving exhaust manifold pressure, and reducing the exhaust temperature, which would effectively reduce combustion chamber temperatures and chances of detonation, etc, etc. Its almost like a viscious cycle once you really start to thing about it. So the bottom line is to try and reduce pressure loses in the intake track between the compressor and combustion chamber.

.........

[BryanPendleton]

Part II

As far as intercooler design is concerned, I am aware of two basic types. The "bar and plate" design (your typically Spearco intercooler) and the "tube and fin" design (I believe the Starion intercooler is a "tube and fin"). While I am not familiar with the intricacies of the two designs, I do know that the tube & fin is more efficient than the bar & plate, but it also sacrifices the low pressure losses found on the bar & plate designs. Intercooler design boils down to a compromise. On one hand you want to slow the air velocity to allow heat transfer to occur and maximize the surface area with which heat from the air can be transfered to the aluminum core. On the other hand you want to minimize flow loses by stream lining the core and minimizing surface area which creates viscous drag (commonly called frictional drag, which occurs at surfaces). So you can see that intercooler design is clearly a compromise. I should also note that there are pressure losses due to density changes of the fluid medium also, but the losses are small relitive to viscous losses. Viscous drag is by far the biggest contributor to pressure losses in intercoolers.

For the sake of being a complete discussion, If you are interested in pressure changes due to density changes in the fluid medium, simply refer to the conservation of mass law. The law states that mass cannot be created nor destroyed, so what goes in the intercooler must come out. If m1 goes in and m2 comes out, then m1 must equal m2. Now what is m1 and m2? Mass Flow Rate. What is the mass flow rate? Mass Flow Rate is the amount of mass that enters the intercoolers per some unit of time, or simply the Volumetric Flow Rate X Density. If the inlet and outlet dimensions are the same, and there is no density changes you can clearly see that the Volumetric Flow Rate will not change, but if you increase the outlet density, you clearly see that the Volumetric Flow Rate must decrease to conserve mass. Now what is Volumetric Flow Rate. Volumetric Flow Rate is the volume of the fluid that enters the intercooler per a unit of time, or Area X Velocity and since we said that the areas are the same the exit velocity must decrease. As for the pressure increase due to density change simply look at Bernoulli's equation. For a demonstration of Bernoulli's equation in action, simply take a strip of paper about an inch wide and several inches long. Hold on to one end of the paper. Place it up to your lips so you can blow air across the top of the paper strip. Without blowing air you will notice that the paper strip falls limp, but if you blow air across the top of the paper, it will actually rise. This happens because the still air on the bottom exherts more pressure on the paper strip than the flowing air across the top, so the paper strip rises. While you may have a increase in pressure, don't forget these gains neglibible compared to the viscous losses.

Other things to also consider is your intercooler volume. It may be tempting to stick an huge Mack truck intercooler on there because it offers a 0.10 psi pressure loose and is 99.9999% efficient (exaggerating) but the intercooler has such a huge internal volume that it takes your T3 compressor half a minute to pressure it up to the set boost levels. Here you can see the advantages of running smaller intake plumbing between the compressor and TB, while the pressure losses from running 2" pipe over 2.5" pipe may increase the pressure losses by 0.1 psi, but the system will reach boost 0.5 second earlier (Note that these numbers are just examples).

I did not write this to choose your intercooler for you. I rather wrote it to help you make you own desicion. Please let me know if it helped.

[190km/h]

I'm not sure that intake volume is THAT much of a concern. When you consider the massive amounts of air flowing through a turbocharger, a bit of pipe shouldn't take too long to fill.

Say you have a turbo pushing 450 cfm filling about half a cubic foot of pipe (generous) and 1.5 cubic feet of intercooler (so imagine a 1' tall, 4' wide, 3" thick IC... droooool.)

450 cfm / 60 seconds = 7.5 cfs
2 cubic feet / 7.5 cfs = 0.2667 seconds to fill it.

I suppose it's worth worrying about, but I can't see a turbo taking 30 seconds to fill anything.

Edit: Actually, since only half the intercooler is exposed to the intake air, and a bit of that is full of fins, let's call it 0.6 cubic feet of intercooler.

So now it only takes 0.1467 seconds to fill that bad boy.

[92 SCd SHO 5spd LX]

I was ready to post the same exact thing....
Rule of thumb- Use as much frontal area as you can afford (and fit). Also remember most of the cooling takes place in the first 2 inches of the thickness of the core. And the thicker the core, the less air flow to the cooling system.

My 2 bits.

[BryanPendleton]

I am simply trying to convey all aspects. Most people do not consider intake volume, and it does impact the responsiveness of the turbo system, that cannot be disputed. That is the only point I am making. The impact may not be real significant, just like the density change is not real significant in the pressure drop accross the IC, but there is an impact.

I am simply conveying that if your interest is a low boost turbo application, you do not need to run 3" plumping and a GT-R intercooler, as this would simply reduce the responsiveness of the system and the benefits are negligable. Law of dimishing returns, is what is called.

[92 SCd SHO 5spd LX]

Originally posted by BryanPendleton


I am simply conveying that if your interest is a low boost turbo application, you do not need to run 3" plumping and a GT-R intercooler, as this would simply reduce the responsiveness of the system and the benefits are negligable. Law of dimishing returns, is what is called.

Right, I totally agree on the piping issue. 2" or 2" in, 2.5" out if you want to be fancy.
But I do have an example of a low boost kit using a BIG cooler for you. This isn't probe related, but that really doesn't make it any less valid.
Car- my stock 94 Celica with 7AFE (Family Engine, used in the corolla as well ), which is a 4V 1.8L eco-box engine.
Intercooler- Half of a Power Stroke IC, measuring 24 x 10 x 3 on the core (close to the GT-R IC you mentioned.).
Turbo- T3, std turbine, .48 A/R exhaust, TB0348 compressor wheel, T3 compressor housing.
System response-
Boost onset- 2000-2200 RPM (depending on load)
Full booost- 2600-2800 RPM (7 psi)
Watching a 97 M3 tring to pass (All most DEAD even) on the Highway.....
PRICELESS
:grin:

An intercooler is something you should only buy once, Something around a 19" x 7" x 3" Core will serve you well... All the way to around 450HP, more than enough for most people. And also consider at lower outputs, the efficeincy and pressure drop will be very favorable (giving you a margin of protection from knock, hot weather problems, etc).

[fpgt'91]

Well I'm by no means an expert on anything about IC's and the mathemtaics behind it but does size really matter if your IC efficiency is extremely high?
Which brings me a tad bit off topic in this thread, and if it ruins it im sorry it is a good thread...but, just as an idea to increase the efficiency of IC. Ive notcied that all of the cooling takes place inside the intercooler, then the air goes into the piping and then intot he intake and so on...but couldn't you effectively decrease the air temp. even more if the IC piping was cooler somehow? Not just by cermic coating, but what about wrapping some tubes around the piping that were able to flow liquid nitrogen with a small pump...woldn't that help to cool the air even more, and then in a sense, increase the efficiency of the IC (and its piping)?

[BryanPendleton]

Does IC size matter? Yes, in certain applications I believe it does matter. For reasons mentioned above IC size and intake plumbing volume effects the boost response. Would I be concerned about IC size on a race application? NO! Would I be concerned about IC size on a low boost street application? YES!, because I would want to design the system to be responsive.


As for cooling the intake plumbing. . . Yes thats possible. You will probably never even come close the matching the effeciency of an IC, unless you use fluid medium to cool the tubing. The total surface area in an IC, is HUGE, compared to the outside of a piece of tubing.

Oh, and coatings and wraps will only trap heat inside the plumbing.

[neverending626]

my .02

The best way to put this, now that all these facts are on the table is: don't get an intercooler that's too big for your turbo. Think of it this way... from the examples of good I/C's above:

19"x7"x3" IC with 4' of 2" piping has a total internal volume of approximately 650 cubic inches, whereas the 1'x4'x3" IC with 4' of 3" piping has a volume a little over 2000 cubic inches.

The first system listed would be pressurized in a third the time of the latter if they were used in the same turbo setup. The second system would have almost triple the time in the intercooler. The first system would have warmer air entering the motor, but it would be entering faster initially.
I think it all ends up boiling down to personal taste. There's just no need to crazy with a big IC if you're on a stock turbo, whether you're runnin' 8psi or 14.. in my opinion.. Well I also have I bias.. I'm poor. .. my 2 cents

[Probehead]

This has been covered a few times. Basically, they are more efficient at cooling the air until the water system temp hits ambient. This is why they are popular at race tracks, because they can stay cool for short runs. But say long freeway trips, street driving in traffic, ect..... the water heats up over time and gradually reduces their efficiency.

Try a search for more debate on this.

[HaddixRacing]

Starion intercoolers (like many I see on the front of Import cars) have one problem. They are inherently designed wrong. The air flows longways thru the intercooler. If the end tanks were top and bottom and the fins and tubes ran top to bottom, then the efficiency of the intercooler would be greatly increased and the pressure loss would be much less.

[cadvis3d]

Originally posted by fpgt'91
Well I'm by no means an expert on anything about IC's and the mathemtaics behind it but does size really matter if your IC efficiency is extremely high?
Which brings me a tad bit off topic in this thread, and if it ruins it im sorry it is a good thread...but, just as an idea to increase the efficiency of IC. Ive notcied that all of the cooling takes place inside the intercooler, then the air goes into the piping and then intot he intake and so on...but couldn't you effectively decrease the air temp. even more if the IC piping was cooler somehow? Not just by cermic coating, but what about wrapping some tubes around the piping that were able to flow liquid nitrogen with a small pump...woldn't that help to cool the air even more, and then in a sense, increase the efficiency of the IC (and its piping)?

There's a new NOS system that does just the, made by wizards of NOS i think...its a NOS kit which includes pipwork etc. It basically attaches to the intercooler and when switched on, flows the NOS throught the pipes, which being extremley cold, cool the intercooler down rapidly, thus cooling the air and giving you more power....i think its called 'internos' but i'm not quite sure..

anyone else heard of it?

[92 SCd SHO 5spd LX]

Intercooler brands are un-important.
They are all made by the same processes.
Types are a different story.

People make some claims about how bar/plate cores are more efficent (Mainly to increase sales). But if you look at most factory front mount coolers, they are tube/fin. The bar/plate supporters say its because they are cheaper... But they neglect to tell you that their high efficeincy core tend to seriously reduce air flow to the radiator (making people think the turbo is causing increased coolant tempature). Also bar and plate cores are very square which isn't good at directing airflow to the radiator. Also the japanesse intercoolers seem to the tube/fin and to say they haven't used them to produce high HP is just silly.

All in all...
beware of thick bar/pale cores (or cores thicker than 3" peroid) and don't doubt the usefulness of a good aftermarket tub/fin coolers.

[GTRacer93]

Intercoolers! All the same?

I sometimes ask myself if its worth worrying about the intercooler. No matter which one you get, design or size, its going to cool the air. Obviously, the larger the IC, the cooler the air, or atleast you'd think. Thats why I'm so curious about this Water Cooled IC's stuff. I don't know who makes one and what not, just that they can cool without needing air and they are smaller in size. Why not run both? Stick the Water under the car and the Air cooler up front? You can get stock intercoolers off used cars on ebay from $10 to $100 ($100 being a good one). I'm using the IC off of the Ford Thunderbird but am considering a water-cooled IC as well as I'm wanting to boost 10psi. I have an Eaton M90 which I heard was good up to 12psi? Don't know if thats accurate but I'll find out.

I'm all for the water IC's as thats what the Ford Lighting Truck has I believe and its a 400hp truck! Has to mean something.

[GTRacer93]

Is it boost?

When you consider what a supercharger accomplishes vs what the turbo accomplishes they are both BOOSTing the cars overall power. They both heat up the air. An intercooler is just a must in any case. How efficient you want to be is up to you. If you want 5psi and the intercooler robs you of 2psi then you just jump the boost up a little. This is why its not uncommon to hear one guy say, "I'm running 10psi of boost" or "I'm running 13psi of Boost" when at the end they have the same times and horsepower. Its all in the tuning and how efficient you want to be. If you want to get really efficient, go with Water Cooled. They tend to be about 30% more efficient then any air coolers out on the market. On avg they lose 1psi and less. Average Air Intercooler losses about 1 to 2psi. But are you really losing that psi if its cooling the air and adding to the overall hp level? Colder air means more HP. So thats 2 aspects you have to look at.

In short though, YES you can use this page to aid you!