Aluminium Radiators & Engineering Pty Ltd
Unit 11 / 60 Kremzow Rd
Brendale QLD Australia

Ph +61 07 32054620 Email info@are.com.au

Intercoolers
A must read....

Obviously if you've landed on our website, then you have some interest in our cooling products.  It can be seen from the content and effort put into our website that it is designed not only to promote our products but also to educated you, the customer.  

The information below is our opinion on intercoolers, based on the experience and sights we see everyday at work.  We hope this will help you in choosing what type of intercooler you want fitted to your car.

Bar & Plate vs. Tube & Fin    |    Tank Shape    |    Can an intercooler be too big?    | 
Intercooler Maintence   
|    New Truck Intercooler Cores    |   Used Truck Intercoolers    |
|    Glossary    |


It seems that due to the cost of new fabricated intercoolers, a lot of people are looking for a cheap alternative.  However, as the old saying goes, 'you only get what you pay for' and the same applies to intercoolers.  There are significant differences in intercoolers, not only in core construction (bar and plate or tube and fin), but also their design (especially tank design).

There is a reason for the cost involved in buying a new intercooler (whether it be ARE or another company), and they do offer advantages over other options especially truck intercoolers.

Bar and Plate or Tube and Fin?

Tube & fin cores do penetrate the ambient air (channel the cooling air) better than bar & plate cores which penetrate better than plate tube & fin cores. Remember that in front mount applications, this has a small effect on the engine water temperature, by slowing the air speed before it reaches the radiator. This is because the rounded leading edge of the tube & fin tube parts the air with less turbulence than the square leading edge of the bar & plate tube, which parts the air with less turbulence than the "W" shape of the tube & fin tube. The following drawings illustrate the turbulence caused by the three tube shapes. 

Tube and Fin

 

Bar and Plate (below)

Plate Tube and Fin (below)

 

Tanks

Square edged tanks are frowned upon by performance conscious enthusiasts for two reasons:- 

1) A square edge concentrates stresses along that fold, which, depending on several factors, will shorten the life of the tank to a some extent. It's surprising the number of small weeps that can go undetected for months, especially if the turbo seals are good, resulting in a loss of economy/performance. This applies more to a sheet metal tank than cast tanks, due to their thinner wall construction. 

  

 

 

 

 

Square edged intercooler tank and resulting flow                                     Better designed intercooler tank and resulting flow

 

2) Most importantly is that the square edged tanks hurt air flow & increase "static" pressure drop. The intake charge does not want to make a sharp turn with the majority of the air taking a radiused path out off the edge, causing some of the air to eddy back around through an elongated 360 degree tumble. This causes friction with both the wall surface & the following air, really hurting flow figures. 

A few factors should be remembered with air flow. A street car is not in high boost that much of the time (maybe20% max. or no licence, no tyres!), and for possibly 20% of the time in vacuum, with maybe another 30% at less than 5psi boost, so the engine operates as a naturally aspirated engine for approximately 40% of it's life. 

Now, how many hundreds of hours a year do the Group A Supercar teams spend on the flow bench trying to find even a half a percent increase in flow? A square edge tank can easily cause a 20 percent drop in flow, in vacuum !! Some people confuse the result of poor tank/pipe design with turbo lag, when it actually may have little to do with the turbo's performance.

 This has been reinforced with our Air/Water intercooler R&D. program, where much shorter/straighter pipe lengths are used (reduced turbo lag). A crisper throttle response with increased "driveability" can actually be felt driving the vehicle, also very important in Rally, Hillclimb, Jet boat, type competitions. 

The importance of squared tanks exponentially decreases with boost pressure increases. If you see a car at the drags that runs 35 plus psi, with square tanks on it's intercooler, don't worry about it after the car has launched & is revving out as power loss is minimal ( maybe 3%), but if the engine could not spool up quickly, or needs nitrous to spool up, then the tank shape plays a very definite part in this problem, with Rotary engines seemingly affected more than 4 cylinder engines. 

Can an intercooler be too big?

In street driven applications, an intercooler can definitely be too big, not for 'attitude', but for maximum performance. It is not an argument to say that Joe Blow's RX2 runs 9.6 @ 132 with a monstrous intercooler because that car may run 9.4 @ 134 with an intercooler that is engineered very close to the overall requirements of that combination. The same may be said for Fred Nerks TX3 that runs 13.8 @ 100 with his headlight to headlight monster intercooler jumping out of the grille. The car may run 13 flat @ 108 with a proper engineered setup. This is because if a 13,500 cu. cm. core drops the intake temperature to 40 degrees @ 1.3 psi. "static" pressure drop, a 8,550 cu. cm. core may drop the temperature to 41 degrees @ 0.82 psi "static" pressure drop, which will produce more power. 

The closer to ambient temperature the intake charge gets cooled to, the exponentially higher the internal surface area of the core is needed, also exponentially increasing the friction (drag) of the air in the larger core. 

Make an effort to suss out the best overall intercooler & pipework for your car, usage & driving style. It may make a worthwhile gain, possibly at less cost! 

Intercooler Maintenance

An intercooler that has been in service for a couple of years will definitely provide more cooling if it is cleaned properly. That is, soaked in a degreaser bath to remove the interior oil film that has accumulated (which may be ever so thin with a new turbo), then power flushed with water. The exterior fins should sprayed with a proper aluminium acidic cleaner to remove the surface oxidation that will have formed. Both the oil film & oxidation inhibit the transference of heat to the ambient air. 

If not sure of the proper procedure & products to use, we strongly recommend having this done by a professional business. 
Please see the below picture, which is a 9 month old intercooler that was soaked in a water based degreaser mixed with kero. The caustic base of the degreaser attacked the alloy & rendered the core completely useless, a new core being the only alternative - expensive mistake. Specific acid cleaners must be used on the external cooling fins as the average thickness is only 0.08mm - that's paper thin. Any bent over fins should be straightened so full air flow is allowed through the core. Last word. Intercooling a forced induction intake charge is a compromise. We direct all our energies at minimising the negative compromises & maximising the positive compromises!

(insert ill-cleaned intercooler picture here)

Truck Intercooler Cores

There are numerous differences between a 'truck intercooler' and an intercooler fitted into a performance car application.  However, 'truck intercoolers' is a broad term and does not sufficiently categorise the product.  Just like other types of products, truck intercoolers come in both bar and plate and tube and fin design.  However, due to their specialised application truck intercoolers have a noticeably courser internal fin or external fin pitch (depending on whether tube and fin or bar and plate), than their cousins fitted into normal performance car applications. 

This means that although a new truck core can be used in performance applications, the core surface area/volume must be large enough in proportion to that of a standard 'performance core', because although it will give good temperature drop it will be at the cost of a medium/ high "static" pressure drop. 

A truck intercooler core has to be larger because as with any intercooler, the heat from the intake charge is dissipated by contact with the surface of the interior walls (fins or extrusions), and then is transfers through the thickness of the exterior wall to the surface of the exterior fin, and is then transported away by the passing ambient air.

The larger volume of a truck intercooler has three main drawbacks:-
1)  Higher 'static' pressure drop
2)  Increased 'turbo lag'
3)  Higher engine water/under bonnet temperatures - in front mount applications as the large truck intercooler blocks more of the flow through to the radiator.

Therefore, if money is a major issue than new truck cores in a performance car are a viable BUDGET alternative, especially if tanks can be fitted at "mates rates"! 

Used Truck Intercooler Cores

It is our opinion that used truck intercooler cores should not be used in a performance car.  Using a used truck intercooler core is a huge gamble, are you prepared to risk the welfare of your engine because of a cheap intercooler.  Why put a $100 core in front of a $2000+ engine?  

Because most truck intercooler cores fit straight into a performance car application, they are usually modified.  During this modification process, whether it be when the old tanks are being cut off, or when the core is being cut down in preparation for welding tanks on, swarf and fillings can get lodged in the core, some of which can be up to 600mm in length and can be imposible to blow or clean out.  The result is that they dislodge days or weeks later, after working their way through the intercooler tubes and intake piping and end up passing into the engine.  I'm sure you can imagine the result of that!?

Another point is that bar & plate and finned tube cores are much, much harder to clean any solid particles out of as they get trapped in the fins & have to "travel" through the length of the tube, interestingly, the exact same reason why per sq. cm., these cores dissipate heat better, but at a higher "static" pressure drop.

Used truck cores in a performance car are a stupid desperation alternative.

 

Short Glossary (for a our full edition click here)

* Static pressure drop - The measurement of the drop in pressure of the air travelling through the core, friction or 'parasitic drag' measured on a flow bench (of capable capacity) at ambient temperature.

* "Dynamic" pressure drop - The measurement of the drop in pressure of the air travelling through the core, friction or 'parasitic' drag plus the drop in pressure caused by the cooling of the intake charge (closer molecular structure of the particles resulting in a denser, smaller volume exiting) due to the mechanical design of the intercooler, or in more engineering terminology, thermal matrix heat exchanger!

 

 

 

 

Aluminium Radiators and Engineering Pty Ltd (ARE Cooling)
 While every effort is made to ensure details and information is correct at time of publishing Sunday, 05 August 2012
please contact ARE by phone, fax or email to confirm prices before order
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