HWLabs Black Ice GT Xtreme 360
3x120mm Radiator
by skinnee - May 4, 2009

First and formost, I want to thank Hondacity for donating the HWLabs GTX360 for testing. I was having some trouble rounding up a few radiators that the Liquid Community was looking for numbers on and Hondacity gladly offered up a GTX360 for me to test. Many of you probably know Hondacity from XtremeSystems.org or Overclock.net. I have thanked Hondacity many times for his generousity, but if you are glad to see this review, be sure to thank him as well!


The HWLabs GTX360 is the latest evolution in the long line of radiators from HWLabs. The GTX series follows the widely popular Black Ice Xtreme or BIX line of radiators. The GT Xtreme (GTX) line covers the full range of sizes including a 120 (Single), 240 (Double), 360 (Triple) and a 480 (Quad). A while back I owned the GTX480, but for some silly reason I sold it off. Looking back, what a dumb decision it was to sell off a heat dissipating monster. I was kicking myself as I started analyzing the data from testing. Oh well, I am sure the owner of the GTX480 has put the radiator to better use than what I would have.

Radiator Characteristics

This is my first review of a HWLabs product and to be honest, I do not know much of the HWLabs product history. HWLabs has always been known by me to cater their radiators to high CFM/RPM fans, which is not the type of radiator I personally look to use in builds. However, from the time I opened the box, the GTX360 has met or exceeded my expectations. Everything including barbs, fan and mounting screws and the paint job is a true high gloss finish.

  • Black High Gloss Finish
  • Copper Tubes and Copper fins
  • 2 row 4-pass design
  • G1/4 Barb ports
  • 20 Fins Per Inch (FPI)
  • 15mm Fan spacing (Standard)
  • M4 tapped screw holes
  • Dimensions: 133x54x397mm (WxDxH)

We all know the debate of low and high speed/cfm optimized radiators, and the GTX series is optimized to perform very well at high cfm sporting 20 FPI. Think about this for a minute, low speed optimized radiators have 8-12 FPI and the GTX flaunts 20 FPI. As with the low speed, this does not require you to run those specific fans as you can see when the low and high FPI radiators are compared on the same C/W charts. Staying on the topic of fins, there are two rows of fins between each row of tubes and giving each tube its own pair of fins. Every radiator I have reviewed only has a single row where the tubes share two rows of fins. The tubes are also not as wide or as deep. HWLabs states the tubes are 19mm x 1.2mm Maxflow. Another interesting design that makes the GTX series unique, the dual-pass dual-row flow pattern. The GTX flows front to back instead of side to side like most other. There is a hot side and a cold side flow configuration at work, placing your fans becomes a bit more important. Some planning on your build is necessary here, depending on if you want the barb side to be the first or second pass. Using the right port as inlet and left outlet, the barb side is the first pass or hotside and the back is the second pass/cold side. Left outlet and right inlet makes the barb side the second pass cold side.

Okay, so there is one more design feature is the side panels angle to the fan mounts. Other radiators have the fans flush againts the fan mounts and side panel lip. feature On the GTX the fans do not sit flush with the side panel lip and leave a slight gap. No this is not your fans, the gap is due to the angle of the side panel lip. The fan spaciing is the standard 15mm, no special requirements here.

Pressure and Flow Results

When building your loop there should be a list of things that come to mind, flow and pressure should be near the top of that list. Pressure drop is the measurement of inlet pressure minus outlet pressure, or the pressure lost of flow through the radiator.

Pressure Drop Data Table

The GTX was less restrictive than what I anticipated with the thin tubes and flow pattern. However, the thinner tubes and hot/cold side flow pattern do increase the restriction, so I included the pressure drop curve for the ThermoChill PA120.3 to show the increase. Just to give you some scale, popular EK and Enzotech chipset/mosfet blocks are more restrictive. While the GTX360 is more restrictive than a PA, that does not mean it is going to make a major difference in your loop, the Thermochill has an extremely low restriction curve. Charts below are PSI-GPM, kPa-LPH and mH2O-LPH to cover the imperial and metric audience.

PSI Drop per GPM of flow

kPa drop per LPH of flow

mH2O drop per LPH of flow

Thermal Testing Methodology/Specification


I chose to follow the standard methodology and procedures that Martin used time and time again in his excellent tests, that coupled with all of the mentoring he has provided his methods are the most logical and scientific out there. Not using Martin's methodology and procedures would be reinventing the wheel and ultimately result in confusing test reports for everyone to read.

For radiator testing, the best way to conduct the tests is to apply a heat load, just like your CPU, GPU(s) and other components you can put a block on and add to your loop. In order to supply the heat load for testing, I use modified aquarium heaters. Aquarium heaters are available in a variety of different wattages, lucky for us wattage is exactly what we are looking for in heat dissipation results. However, the tricky part with aquarium heaters is circumventing the safety mechanism that shuts off the heater when the set temperature is reached. Modifying the aquarium heater allows for a constant heat load to be applied to the loop rather than heating the water to a given temperature and shutting off.

Measurements and calculations, what exactly are we going for here? One of the best means to determine the capabilities of a radiator is C/W, Martin turned me on to this in one of his early tests. Ultimately, C/W is a calculation of Water Out temperature minus the Air Temperature being pulled or pushed through the radiator divided by the heat load (wattage). This calculation gives you the delta in degrees of the radiator leaving water for each watt of heat applied to the radiator. Confused yet? An easier way to think of C/W is the temperature of the water over ambient temperature for each watt of heat in your loop. Now that we have this equation and results we can specify a set delta and figure out what heat load the radiator can dissipate at that specified delta. In short, this helps answer the question, can this radiator handle a CPU and GPU and get me decent temps. A bit more on C/W, this time in relation to Fan RPM. On several charts later in the test report you will see Fan RPM charted with C/W. This is to show the effect on radiator performance in using different speed fans, some radiators perform very well using low speed/cfm fans and get better the more cfm you push/pull through the radiator. Where some radiators perform sub-par with low speed/cfm fans and require high speed/cfm fans to effectively dissipate heat from your loop. Yes this has a lot to do with how the radiator was design, but I feel it is an important piece of data to show as a misconception I had early on in the start of my liquid cooling addiction was low speed/cfm fans could not be used on radiators optimized for high speed/cfm fans. I was quickly shown how wrong my thinking was.

Besides the typical Fan RPM, air temps and water temp measurements you will see Air Capacity Used listed in the data table.

Test Note: Maintaing a constant wattage for each test is nearly impossible even with a AC Transformer (Variac). You will see slight wattage variations amongst the test results.


A total of 6 tests per round were completed with a total of 2 rounds (1 set wattage per round), each one of the tests used a different Fan RPM to represent different fan scenarios. This gives a best coverage of uses of the radiator out in the wild, not everyone will want to use the same fans or run their fans at a specific RPM, so I tried to cover 6 different RPM settings. Each test consisted of a 30 minute warm-up period with the heat load applied to the loop and a 60 minute logged test run. The heat load was applied by adding the modified aquarium heater in a custom built half-gallon reservoir. Below is list of all of the tools

  • Temperature Monitoring and Logging: CrystalFontz CFA-635 with SCAB attachment - Used to log 12 temperatures (9 air, 3 water) and three Fan RPM sensor at 10 second intervals.
  • Thermal Sensors: Dallas DS18B20 Digital one-wire sensors - .5C absolute accuracy overall with a .2C mean error between 20-30C.
  • Test Bench Sensors Deployed:
    • 1 air in sensor per fan (total of 3)
    • 2 air out sensors per fan (total of 6)
    • 2 water out sensors
    • 1 water in sensor
  • Flow Rate: King Instruments 7520 0-5GPM, 10" Scale - Accuracy 2% of scale. Flow Rate controlled by a brass gate valve with 1/2" NPT 5/8" Barbs
  • Water: Local Grocery store steam distilled water
  • Fans:
    • Yate Loon D12SL-12 120mm x 25mm - 47CFM/1350RPM/28dB
      • Silent Speed Fans - Undervolted to 600 RPM
      • Slow Speed Fans - Undervolted to 1000 RPM
    • Yate Loon D12SH-12 120mm x 25mm - 88CFM/2200RPM/40dB
      • Slow-Med Speed Fans - Undervolted to 1400 RPM
      • Medium Speed Fans - Undervolted to 1800 RPM
    • Scythe Ultra Kaze DFS123812H 120mm x 38mm - 133CFM/3000RPM/46dB
      • High Speed Fans - Undervolted to 2300 RPM
      • Ultra High Speed Fans - Volt Adjusted to 2800 RPM
  • Data Logging: Each temperature sensor and fan RPM channel is logged for 60 minutes after the 30 minute warm-up period. Having two sensors in one location (ie: water out) allows me to average the sensors together to rule out fluctuations. This also helps to ensure the system has stabilized and remained constant during the test.
    • Air Inlet Temperature Data: Each test uses one air inlet sensors per fan logged every 10 seconds for the duration of the test. The air inlet data is averaged using 1080 data points per test.
    • Water Outlet Temperature Data: Each test uses two water outlet sensors logged every 10 seconds for the duration of the test. The water outlet data is averaged using 720 data points per test.
    • Fan RPM: Fan RPM is monitored via the Crystal Fontz CFA-635 and logged at the same interval as all temperature sensors. The Power is adjusted via the CrystalFontz to an RPM setting and logged very 10 seconds during the test period.
    • Heat Load: Wattage for the aquarium heaters are measured via a KILL-A-WATT every 10 minutes during the test, I'm quite lucky to have stable power as this does not seem to fluctuate much at all during the test. The aquarium heater wattage is added to the pump wattage (volts x amps) measured by a Fluke 23 Series II Digital Multimeter with power and additional monitoring from a Mastech HY3005D Variable DC Power Supply. These two inputs give us the total heat load applied, then averaged for the test duration.
  • Test Lab Environment: Unfortunately, I do not have an environment test chamber. All tests are performed in 10x13 room in my basement which is temperature controlled via a wall thermostat and on a separate zone from the rest of the house. I am able to maintain a consistent room temperature this way. For the test fixture, I am using about 4' of 1/2" ID 3/4" OD Masterkleer tubing (un insulated). The loop consists of a custom 1/2 gallon reservoir, Swiftech MCP655 (EK D5 X-Top Rev.2 top), King Instruments flow meter (5/8" fittings) and a 3/4" brass gate valve (5/8" fittings).

Thermal Test Results

Heat Loads

Now that we have all of the methodology, specification and data explanation documented and detailed lets get on with what you all are looking for...the results.

Here is the main chart for bringing all of the logged data in and using this data to calculate Water Out-Air In, and C/W. Another column you see in the table is Air Capacity Used, this column shows the rise in air temperature relative to the water temperature.

You will obviously spot the higher watt run for 600RPM, I had to stop the test before the run could complete. I have had problems in the past where the radiator cannot dissipate the heat, the water temp rises to the point where tubes start melting and there is the lovely risk of an electrical fire (long story). So, my safety is 55C water temps. If I see water temps getting close I stop the test. I will not risk the equipment or my house for numbers.

With the explanation out of the way, the test data show can begin.

Now for the performance numbers and muscle flexing portion of the program...This chart plots the Water Out-Air In Temperature or Delta versus the Heat Load applied. This chart is the most useful in estimating the Delta for a given heat load (watts) to be applied to the radiator. Simply locate the wattage on the X axis and move up to find the Delta for a given fan speed. Add this delta to your ambient temperature, and that is what you can expect for a loop water temperature.

For information on calculating heat load for your loop here are two resources I have used in the past. Another method I have used in the past is to Google search TDP for a specific component, that should also help in estimating the heat load that will be in the loop for a specific component. The primary one for me is linked below, they take a lot of the google searching out of the equation and break everything down to just the numbers you need.

Please remember, calculating the power consumption and using that as heat load is not exact and is only an estimate. This estimate will be higher than actual heat load applied as you do transfer some heat to the air circulating in your case around the components. How much difference I cannot begin to speculate, but I just want to state that it is only an estimate and not an exact specification.

Applied C/W

Now that we have looked at the plotted results, lets apply the C/W results with a given Delta (Water Out-Air In) to find how much wattage can the radiator dissipate. Below is the data table for calculations of Deltas of 15, 10, 5 and 2. Here is my classifications for those deltas.
  • 15 Delta: Low Performance, an overloaded but capable loop.
  • 10 Delta: Average Performance, very capable of good temps and representative of an average system.
  • 5 Delta: High Performance, for those of you looking to achieve the best possible temps.
  • 2 Delta: Ultra Performance. extreme setups only, this would be an ultimate setup where you limit to dedicated block loops.

Here are the plotted C/W results over the fan RPM range, as you can see the results do follow close to a plotted trendline. This trendline might not mean much to you, but to me the trend line helps me see that my testing and resultant data are accurate. Additionally, if you plan on running your fans at a speed other than the ones I tested here is another reference point to estimate the results you will see.

With the C/W calculated, we can apply a specified wattage to give us the watts dissipated for our RPM range. This chart is just the plotted results for a 10 Delta or Average Performance from the data table in the beginning of this section. The GTX360 does not have the best performance and low RPM, but starting with the 1400RPM test, the GTX starts to show its amazing performance. The number my eye keeps jumping to is the 2800RPM test, over 1200watts of heat dissipation amazing for a triple radiator.

Here are the plotted results for a 5 Delta or High Performance from the data table in the beginning of this section. The 5C numbers in the mid speed fan range are still really impressive, the GTX matches or beats the PA120.3 with medium speed fans between 1400 and 1800RPM.

Here are the plotted results for a 2 Delta or Ultra Performance from the data table in the beginning of this section. This chart is purely to show what wattages and fan speeds you need to get really close to ambient water temps. I typically say this delta is not going to happen for most out there, but high speed fan numbers are impressive once again.

Price Considerations

What is the wallet damage for picking up this heat dissipation beast, lets look at the GTX360 pricing and other Triples. HWLabs pricing seems to be about the same around the globe, but the GTX360 is a bit more expensive than other radiators we've reviewed. However, the High CFM/RPM performance is worth the money. If having a tremendous amount of heat dissipation in a triple radiator is what you need, the GTX360 is worth the price.


I had a bit of experience with HWLabs going into this review, the GTX360 changed my opinion with the performance in heat dissipation. I was very surprised at how well the GTX performed in the medium speed ranges. You can see how the GTX360 performed versus the rest of the triples in the Triple Radiator Comparison report. One of the first things you notice on the radiator is the fins, the dual row 20 FPI configuration is a true performer. Yes the tubes are thinner and the radiator does introduce more restriction into your loop, though the restriction is not enough for you to be concerned about running multiple block loops with this radiator. A D5 or DDC is more than capable of keeping the flow rate up.

Now there was one thing that has bothered me about the GTX and that is the gap between the side panel lip and the fan housing. I have a suspicion that if that gap were eliminated and the fans mounted flush, the low speed fan numbers would improve. Although, the GTX was not designed for low speed fans and this gap provides a benefit to higher CFM fans. And speaking of those fans, the GTX does not have the screw to fin distance you have on most other radiators. The fins are very close to the side panel lip and fan mounts, be very careful on screw length when mounting your fans or to the case.

    • Extreme performance at high fan speeds
    • Medium speed fans performance
    • Hot Side / Cold Side flow pattern
    • Average restriction
    • G1/4 Barb ports
    • Standard Fan Spacing
    • Best paint on the market

    • Fin to Fan mount spacing, careful with those fan screws!

After running the tests on the GTX360 I kicked myself for days, I should not have sold that GTX480. My ears do not like high speed fans like the Ultra Kaze, but there are a variety of fans with better performance that are quieter. The HWLabs GTX360 surprised me honestly, I was not expecting the medium speed fan performance. The GTX meets or beats other triples with medium speed fans. This really is a great radiator, extreme high speed fan performance with pack leading medium speed fan performance. And the paint is the best on the market. I really wish I did not have to send this back to Hondacity, thanks again for loaning your GTX360 to for testing. Yes, I will run numbers on push/pull for you!

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