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  • Writer's pictureJoel Brown

Introducing the Banshee Intercooler Upgrade!

*First and foremost I would like to express my most sincere gratitude to my mechanic and friend Curtis Cowan at FAME Garage in Colorado Springs, CO.

If it wasn't for Curtis's knowledge and ability, this project would not have been as successful as it was. I originally had a more complicated and more expensive design planned and he advised to opt for this instead and it was the money shot! This couldn't have turned out better! This man doesn't miss!*

The 4.2 SC engines have one very specific design flaw... one, little, easily reversed feature of the intercooling system that completely negates all efficiency brought into the picture by Air-To-Water intercooling.

Typically... Air to water is one of the most efficient forms of intercooling. However in Jaguar's case, once the engine reaches operating temperature the entire system is already heat soaked. The base temperature of the coolant going through the system is 186* F.

This is due in part to Jaguar plumbing the intercooler system into the radiator system.

This keeps consistently hot fluid passing through the charge coolers (I know I'm not the only one who has suffered the burns from them).

The system has no reservoir aside from the expansion tank for the radiator which, on the supercharged models, is marginally larger to account for intercooler capacity.

But... it's a measly 0.6L of fluid that makes zero difference in coolant temps.

The factory system does use a heat exchanger paired with a hella pump to remove some of the heat from the fluid but it's a poorly designed single pass unit with a base level efficiency pump that seems to struggle to keep up with the 186* coolant temps heatsoaking the system, and once the coolant returns to the radiator, it reaches 186* F again fairly quickly.

As you can see, the factory heat exchanger is a single pass design that flows coolant straight through from one side to the other so the coolant does not spend enough time in the matrix to be cooled properly before being reheated to 186*. You can also see the stained areas where the cheeply made, porus material of the oem heat exchanger has been sweating out coolant. (Above)

We approached this solution with an all Aluminum, lightweight, 1" thick core, dual pass heat exchanger with end tanks that, fills the exchanger from top to bottom with the pump pulling from the low point in the system and exits the same side it entered in order to move the coolant through the matrix twice before exiting. Having two passes ensures the coolant takes slightly more time to reach the outlet, increasing time exposed to the cooling effects of the matrix. It also ensures the entire exhanger is filled with fluid to get the best cooling efficiency and usage of surface area.

The next order of business was addressing the hot coolant supply. By divorcing the intercooler system from the radiator supply and adding our own reservoir that we sourced from a Mustang Shelby GT500, we successfully created a fully divorced and standalone enclosed intercooler system with a total capacity of 1.5Gal of fluid that, the Stage 1 version of this kit, using the stock Hella IC pump, moves fluid VERY efficiently.

Stage 2 will come at a later date and include fans, a larger pump, and some other design improvements.

Pictured above you can see we mounted our GT500 Intercooler Tank where the airbox used to sit, positioned in front of the WOT flap hole behind the headlight to also keep constant airflow over the tank itself.

Fun Fact! We accidentally lowered IAT1 with this placement and I'll explain more on that in a little bit. Keep reading, it gets good.

But first... We're gonna get off track on another accidental improvement for a second. Bare with me... this came about after sucessfully installing and testing the IC Upgrade.

Tragedy struck (Pictured Above) and the original Coolant reservoir cracked in several places. I was able to duct tape it enough to hold fluid long enough to drive to the shop, which it did! It let go as I pulled into the bay 🤣🤦🏽‍♂️.

A replacement had been ordered because I had a feeling it was going to go soon but the order was incorrect and they sent me a reservoir from an XJ8. As luck would have it, the 0.6L smaller, more compact and attractive unit also lacked the return port for the intercooler that we capped on the original and it was an eyesore that I hated looking at anyway so, hurray for another plus!

We made a last minute decision to just try the XJ8 reservoir instead of waiting. It was more attractive, it allows you to see the supercharger snout, gives easier access to the area, and the 0.6L was no longer of any concern because we had a whole 1.5Gal in a divorced and enclosed system.

That, and... I had a date with a Twin Turbo AWD Maserati that night that, I WAS NOT trying to miss.

So, more about the accidental improvement of our GT500 Tank placement... by having it positioned in front of the air filter, we accidentally created a cooled air source as the air from the WOT flap hole behind the headlight draws over the 46* coolant tank before being fed to the air filter.

The 76mm Banshee Aluminum MAF Housing stays cold to the touch despite sitting in the claimed "Hotest part of the engine bay" just 10-12" from the exhaust manifold.

Data logging has shown a reduction of 30-40* F in IAT1 (Pre intercooler, intake temp)WHILE IDLING. This means an open element style cone filter or foam filter does not need any heat shielding with this configuration.

Another really cool accidental improvement is the sub ambient coolant in the heat exchanger draws COLD air from the fan into the engine bay and evacuates A LOT of heat which lowers under hood temps as well.

Once it was all said and done, our test results were absolutely astounding!

My mechanic, Curtis, sent me photos showing pump outlet temps of 53* F 😳 after 30 minutes of idling in 70* F ambient temps in direct sunlight! Unfortunately he wasn't able to grab a picture but after roughly 45 minutes of idling, pump outlet temps and Tank temps were locked at 46* F! IDLING with ZERO airflow over the exchanger. The system removes heat while sitting idle and makes it non existant when in motion. This is a great upgrade for anyone who sits in staging lanes at drag strips or deals with heavy traffic for sure!


The charge coolers are ice cold after driving and retain that as long as the engine is running and the STOCK PUMP is moving coolant through our beautiful dual pass exchanger. It's a little overkill considering the exchanger itself is rated to support 600-1200hp applications, but... it leaves a lot of headroom for those who don't want to stray from air to water intercooling. It's also perfect for our application considering these cats spend their lives never seeing what their intercooling system is truly capable of.

In data logging we have confirmed that IAT and IC Coolant temp directly impact boost and timing per the ECUs instruction. As most can confirm, these cars were claimed to make 13.1psi of boost in stock form... however, as most owners who have logged can tell you, they rarely see anywhere near that.

We have already observed this phenomena with our Screamer Intake. The material and construction works to dissipate heat and lower IAT as I've shown in previous write ups and videos. Our customers on average have experienced increases in boost from 1.5-3psi after installing our intake and we believe that is a result of lower IAT allowing the ECU to let up on restrictions.

In short, we believe we may have uncovered the secret to unlocking the maximum potential of the 4.2L Supercharged XJR and S-Type R by way of removing the heat from the intercooling system so the ECU allows the engine to operate at it's peak form at all times and not just in the short minutes before it reaches operating temp.

Paired with our Screamer Intake, the Stage 1 Intercooler Upgrade turns these cars into a completely different machine.

Let's not ignore how good it looks hiding behind those grills either...

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Dec 07, 2023

Sounds like a lot of work been going on. Im keen to know more.

Joel Brown
Joel Brown
Dec 07, 2023
Replying to

I love this platform and modifying it with a grassroots approach. Definitely been scheming and working up some new ideas. This is just the beginning. :)

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