Heat Exchanger Information and Comparison

Posted by Alex Darmos on

The current ZZP heat exchangers are the best solution available on the market! They cool better, hold more water, and offer advantages not offered by any other unit!

Below you will find technical data on our heat exchangers:

Water rows
ZZP has 14 water rows @ 28 x 2.25 x .08″
OTT Gen 2/FB/China has 11 water rows @ 23.25 x 3.5 x .17″
Stock has 69 water rows @23 x .58 x .075”

Fin count
ZZP has 14 rows of ~380 fins = ~5320 .335” fins
OTT Gen 2/FB/China has 12 rows of ~238 fins = ~2856 .400” fins
Stock has 70 rows of ~280 fins = ~19600 .25” fins

Fluid capacity
ZZP  1.80 Liters
OTT Gen 2/FB/China 1.75 Liters
Stock  .95 Liters

Water tube surface area in square inches
ZZP 1764
OTT Gen 2/FB/China 1790
Stock 1841

Cooling fin area in square inches
ZZP 4010
OTT Gen 2/FB/China 3998
Stock 2842

Thermal transfer insulating thickness on fluid walls
ZZP .0155
OTT Gen 2/FB/China .030

ZZP  6.4 lbs
OTT Gen 2/FB/China 17 lbs
Stock  5 lbs

Exposure to air

The water tubes are required for any radiator to work but inherently block some of the frontal area on a given radiator. The ZZP and OEM radiators have water channels with a radius on the lead edge and measure .075”. This makes for very little blockage, and channels nearly all the air into the radiator fins where cooling takes place. The China core is a bar and plate type. This is normally reserved for high pressure applications such as intercooler cores exposed to boost. The bars on this core have a flat surface and measure .18”. Comparing them to the .4” radiator fins reveals that 30% of the radiator is a wall that air cannot pass through. This is not ideal for maximum airflow through a radiator.

The other drawback to an extremely rugged core is that the aluminum is thick. Aluminum has excellent heat transfer ability but any material is an insulator and the idea is to transfer heat from the water to the air. This means that the less aluminum between the water and air there is, the better the cooling. This must be balanced with strength though, or a stone would rupture your core. The China cores have coolant channel wall thickness of .030; which is twice the factory and ZZP cores. This greatly reduces cooling and is unfortunately made worse by the painting of the entire piece.

So in the real world how much does this matter? Turns out, not that much. Nearly any 2nd HE cools the fluid enough to make the differences small when tested. However, it is accurate to say that the ZZP HE does give the absolute best temp drops. The extra weight of the China IC over the ZZP makes a difference. How much? The equivalent of 1 WHP on a 260WHP vehicle. So all things being equal, your car with a ZZP HE will be faster than another car running the China/OTT HE. It’s just simple physics.

The factory HE is actually the best pound for pound, and in the number of cooling fins. The problem is that it doesn’t hold enough fluid because it isn’t large enough to keep temps at ambient and is sandwiched in between the AC condenser and the OEM radiator. So it makes sense and gives good gains to add another heat exchanger. Should you run only the aftermarket HE? No, the factory unit is cooled by fans when standing still and performs well for what it is. Fluid out of the intercooler should enter the factory radiator first and then the 2nd HE.

Update Feb 2010: To add the ‘new’ HE by OTT, their 3rd offering for this market. Touted as the best unit on the market, we decided to buy one and put it through some testing. What we found was a unit quite different than what was described.

Advertised weight: 14 lbs
Actual weight: 16.6 lbs
Advertised fins/inch: 14
Actual fins/inch: 12

Below is a cut-away of the OTT heat exchanger, which allows us to inspect inside construction. What we find is that this is an air/air core modified with end tanks to be used for a water application. The problems with this are numerous. First; an air/air core is not nearly as effective as a standard radiator for heat transfer to a liquid. Second; the divider is just set in place to ‘kind of’ direct the water through the core, as you can see from the below picture (OTT HE pic of each side of the divider) the divider isn’t sealed. It is placed in the center of a coolant row allowing leakage around it. This means all the hot water doesn’t travel through the core but goes right around the divider and back out of the HE! In comparison notice the superior construction on the internals of the ZZP S3 HE. Basically American quality vs. Chinese mass production.