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For those of us who are building high powered LET's, I thought you guys might benefit from some of my technical insight into Intercooler design. Ill update this thread every now and again with a new aspect of charge air cooling but for this first post, lets have a look at ....

Core design

There are two types of Intercooler cores in common circulation today...

Plate and shell

Easily recognisable, look down the end of your inlet pipe and if you see....



...then you have a plate style intercooler core.

Extruded core

I bit more fiddly, look down the end of your inlet pipe and if you see....



...then you have an extruded core intercooler.

Which is better?

Extruded by miles, without question.

Plate style intercoolers are ok for Honda civics boosting round california making about 5psi (any more boost would blow the lambo doors off lmao ) but start talking 10/15/20 PSI you might as well not have it at all. The reason for this is two fold...

1) Because of the ease of which the charge air passes through the cooler, it dosnt stay in the core long enough to cool down sufficently. Its a bit like holding your hand under a tap (when its burnt) for 0.5 seconds, then holding it under there for 3 seconds.

2) Beacuse of the chunky style of the core, it tends to store any heat that is removed from the charge air as it passes through.

Extruded cores get around these two problems like so...

1) The extruded core disturbs the airflow sufficently to slow it down and increase the length of time it takes to get across the intercooler. Before any one shouts LAAAAAAG! We are only talking about 1.5 seconds here and is not noticable but it makes a hell of a difference to the charge air temp.

2) The thin core and heat exchanger set up works very well and is able to disperse lots more heat. Remember, heat can only escape through outer facing surfaces, the more of them you have, the more heat escapes.

This diagram illustrates my point better :



Now you may have been brought up to believe that turbulant air is hot and is bad for flow but you can clearly see in this example, that turbulating the air flow before it gets to the intercooler core is sooooo much better. Besides, the diagram above only illustrates what happens when the air first gets to the core. Half a second later and whats called the "Venturi" effect takes over and sucks the air in through the extruded core but keeps the air speed down so as to maintain a high efficency.

There is of course one fly in the Extruded core ointment..... Price. Most (about 99%) of the universal E-bay intercoolers going for around the £100 mark are of a plate and shell design. The equivalent Extruded core would be around £180 (for arguments sake) but in my estimation, can you put a price on something that works???

I also have ready for publication :

Intercooler Positioning
Charge Colling

Hopefully up loaded soon.

Dave BB
 
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