Originally posted by Spoolinup
Cas's is NEW and extruded tube. Plus, making the stock IC with more stock rows is so late 80's. It just plain worked in 1985 when they designed the intercoolers for the buicks the year later. Things have changed in the intercooler industry since 85.
Its 2002 and guys are still selling the stock IC for good money and saying it will compete against newer technology, ya.
New extruded 21 row vs. larger stock 15 row?
From Speaco.......
The most consistent method of charge air heat transference is Extruded tube. This is because the aluminium is forced through the extrusion die during manufacture, giving a 100% wall to wall bond as there is no join in the material. The next most consistent is the "U" shaped fin, as it is stamped with a flat surface to fuse onto the tube wall, giving up too 30 times the surface area to bond to the tube over the least consistent, folded fin, which is the most common in bar & plate, & all that's seen in plate & fin cores. We have seen intercoolers where the tolerance of the fin fold width is too narrow & so the fin didn't fuse too the tube wall, resulting in little heat transference in that area. Also the fins can bunch up, leaving a gap either side, very inefficient. Another reason for the difference in the price of cores - quality control or sloppy manufacture.
The most efficient method of Charge air heat entrapment is folded fin, because louvered fin configurations &/or very close fin per inch ratios can be utilized, resulting in higher surface areas to "grab" the heat. Note that these also cause the greatest pressure drop. It really comes down to manufacturing quality & specifications between folded fin & extruded tube efficiency as they can give similar results. Some folded fins have holes to break up the air flow, some have louvered fins to channel the air & some are flat but they usually have higher fpi. ratios. Extruded tube dividing walls are either flat or have ridges running length ways for increased surface area.
One last thing to remember is the strength & repairability of the cores. The weakest core by a very big margin is the plate & fin core, we get allot of these through our workshop (including oil coolers of the same construction), but they are relative easy to repair as they mostly crack in the centre of the end tank concertina. They have to be hydrogen brazed as the heat from TIG welding is too concentrated, usually resulting in a weep at one/both ends of the welds. Bar & plate cores are weaker than tube & fin & the other worry is that Garrett paperwork says that it is acceptable to have leaks in the core, as long as it doesn't exceed 4 psi drop from 30 psi in 15 secs !!! We may have had a leak in a tube & fin core over the years, but no new intercooler has ever left our shop with a weep, let alone leak. Bar & plate cores are very difficult to repair leaks anywhere on them, but tube & fin are only hard when the leak is in near the centre of the core. This advice is from our shop, that is one of the few set up too repair properly as well as fabricate new assemblies - in fact there is not another shop set up anywhere near as comprehensive as us, for repairs !
COOLING CAPACITIES (following are two very contentious paragraphs)
As a general rule, with a level playing field (manufacturing quality, both fpi's, tube size, thickness, & a hundred other variables), bar & plate intercooler cores dissipate more BTU's than plate tube & fin & then tube & fin cores - per square centimetre. Please stop, go back & read that sentence again, as it is the most often asked question, but the most misquoted answer of all time. Please also note that it is very easy to change just one specification of a core to make it better than the other two, & it must be remembered right now that heat dissipation is only one parameter of overall intercooler performance. If there is enough area & volume available, I quite often recommend a tube & fin core to do the job, as it will get the temperature down too within very close of the other two, but at less pressure drop & less chance of leakage.>>>>>
