It’s no secret that enthusiasts like us want to pile more on to that acceleration. Once we dug into our donor vehicle, we found that the stock heat exchanger can be the weak link in the chain pulling the Q50 forward, and leaves something more to be desired. After some preliminary R&D, we determined just what needs to be done with the heat exchanger to bring it all together.

Bigger is better. When it comes to improving any form of heat exchanger, this mantra typically rings true. More volume and a larger surface area are both methods for transferring heat more efficiently, and when it comes to the Q50’s intercooling system radiator, we opted for both.

Once we peeled back the Q50’s skin, we found that there was plenty of room to expand into, and Ye wanted to take full advantage of that. Our plan is to let this heat exchanger sprawl across the front of the vehicle and take up the unused real estate. Core thickness is where we did hit a slight snag, however.

Infiniti utilizes a center support beam to cage the front cooling stack. The stock heat exchanger fits behind this beam since it’s not extending down as far, and it’s slightly thinner than our planned design. Ye is still planning on adding a few millimeters to the core design to squeeze in the extra cooling power. She also has a trick up her sleeve to allow the heat exchanger to slide in easier.

A larger core means larger end tanks. We have that covered too. Our fitment prototype might be sporting plastic, 3D printed end tanks, but our final version will be equipped with a sturdier set of all aluminum tanks, improving the overall look of the intercooling system and giving it a substantial boost in durability.

For those keen observers, you might have noticed that our prototype has two outlet ports. There is a reason behind this. When it comes to radiators, the most efficient means of cooling is by a corner-to-corner flow. However, there is a concern about putting too much stress and wear on the pump (or pumps if you have the S or Red Sport trim). Because of this concern, our engineering team wanted to make sure that we cover our bases and see that we’re achieving the best flow without causing any future issues with the pumps.

Showtime is quickly approaching for the Q50’s heat exchanger, but we’re confident that we have had plenty of rehearsal time. Make sure to keep your eyes on the horizon for more updates, and a look at our heat exchanger in the flesh. 

When you last saw our heat exchanger design, it was just the outer framework of what our engineer had planned, but now those plans have come to fruition. The obvious characteristic that carried over from our last post is the sheer size of our heat exchanger. When compared to the stock unit, we might not have gained much in the way of thickness, but the growth spurt still allowed for a whopping 196% increase in core volume and a 97% bump in external fin surface area.

Size isn’t the only improvement over the stock heat exchanger. Our engineer left the plastic end tanks behind in favor of a completely aluminum construction. In addition to adding more rows of fins to our core, our heat exchanger is sporting a tighter fin density for improved heat dissipation.

There’s more to this heat exchanger than meets the eye as well. Given the tight space restrictions and difficult install, we wanted to make sure our new design had all the bells and whistles. For starters, to give enough of a gap between the heat exchanger and the AC condenser, our engineer added an extra plate and foam to the rear side. This way there’s not three different heat exchangers directly on top of each other, and our unit fits like a glove.

Wiggling the larger core around this front support can be a challenge, so our engineer devised a removable outlet port on our end tanks in order to remove some of the difficulty to this installation.

To add to the daunting complexity of getting to and replacing the heat exchanger on these vehicles, the stock system has no clear-cut way of bleeding the intercooling coolant system. For this reason, we opted to add a captive bleed screw on the heat exchanger to aid in a bubble-less intercooling coolant system.

There’s only one last hidden feature on our Q50 heat exchanger design, and that’s how well it performs with the VR30DDTT. Make sure you stay tuned for our dyno testing results.

Pump it Up

First let’s take a quick dive into how the pumps operate in the VR30DDTT’s system. These are integral parts for ensuring the heat that is extracted from the intercoolers is properly transported from the charged air to the heat exchanger. The pump, or pumps if you opted for the Red Sport, is electronically controlled by the ECM with two speeds, low and high domain as noted above. The operating speed of the pump is determined by a calculation of the engine’s load and speed, or put simply, the manifold pressure and RPM. So, low domain covers most of your typical cruising where the high domain speed is when you put the hammer down.

How does the heat exchanger affect the pump speed? I’m glad you asked! During low domain, the size of the heat exchanger core doesn’t have that much effect on the cooling capacity since the coolant is cycling through at a low rate. This means it’s spending a little more time in the core, so more of a chance to transfer heat.

However, once the rate of fluid increases, it’s much more important to have an increased core volume and fin surface area in order to effectively cool the liquid that’s now gushing through the system. In short, the larger heat exchanger will be able to keep up with the higher coolant flow.

High Domain

In order to see just how our design affected the cooling during high domain, we strapped our Q50 Red Sport to our Dynapack system for a series of tests. Since the heat exchanger is in essence a radiator, we opted to put the stock unit and our design through the same series of testing.

Our first test, known as a load test, is designed to demonstrate the performance of each exchanger at a constant load over an extended period. For our test, the engine was held at 3000 RPM for 25 seconds, which forced the coolant pumps into their high-speed setting so we could monitor how the heat exchanger handles the increased rate of flow, and how core dissipates heat once off throttle.

At the peak of our test, the stock heat exchanger outlet spiked to 118°F and leveled off at 110°F, where our heat exchanger design peaked at 110°F and immediately shrugged off the heat. We also noticed that with the stock heat exchanger there was almost no difference in temperature across the core, which is not a good look for your intake air temperatures.

Next up was our heat soak test. This method puts the heat exchangers up against the worst conditions, in that our engineer runs a sequence of 4 back-to-back dyno pulls with no chance to cool off in between. From this test we saw a peak outlet temperature drop of 21°F over the stock unit, with an average 15–20°F difference across the test. Again, no temperature reduction across the core of the stock unit which ended the test at upwards of 140°F. For comparison, our design never went over 120°F on the outlet temperature reading.

Strongest Link

So, what does this mean for your VR30DDTT’s performance? Well, the stock heat exchanger is the weak link in the intercooling system’s chain. Without being able to properly dissipate the heat being pulled from the charged air, there’s less cooling capacity and your Q50 or Q60 doesn’t live up to its potential. Strengthening that link with an improved heat exchanger core keeps the 3.0T cool under boost pressure.