here is a post from the 1Addicts Australian forum, that will provide you with some very interesting specs on the oil coolers we have chosen for our 135i kits.
Originally Posted by TimMc
Picture comparo would be good, but may not tell the story of efficiency of each of the three. As the 20 row unit extends below the air duct, the extra 5 rows will not have the same effect as the 15 above, but will still provide some extra cooling. Could the cooling duct be extended lower? May not look OEM then.
I hope you found the pics I posted to be useful.
The extra 5 rows present in the 20 row core will most definitely improve the efficiency of the oil cooler.
Whilst frontal surface is critical to improved efficiency, total volume also plays an important role in heat transfer.
As an example how many upgraded intercoolers on the market actually have unobstructed airflow across the ENTIRE
front surface of the core, when installed on a 135i or 335i?
To the best of my knowledge none.
The KL Racing aka "Big Tom" intercooler has been reported to be a very nice upgrade, over the ineffecient OE intercooler.
I can assure you there is no way in hell that clean air will see every square centimetre, of the front face of that intercooler.
the core volume of the BMW OE oil cooler is approximately 595 cubic centimetres.
The Stage 1 (15 row) core volume is approximately 1,678 cubic centimetres.
The Stage 2 (20 row) core has a volume equal to approximately 2,288 cubic centimetres.
This puts our 15 row cooler at 2.82 x the core volume of the OE unit.
The 20 row cooler is a very impressive 3.85 x the core volume, of the tiny BMW OE oil cooler.
the cooling duct cannot be extended lower, as the face of the oil cooler is in close proximity to the plastic cowling on the inside of the bumper.