When you cram a big engine into a smallish car there’s a lot of time, effort, and planning that must go into developing a system that properly cools the beast. That’s the challenge we faced in properly cooling the Coyote engine we’re fitting into our project T-Rex, a small British sports car with a big motor.
First, a little background. The M-series TVRs from the 1970s came from the factory with a squatty, wide radiator that was barely large enough to cool its 115 horsepower, 2.5-liter, Triumph-supplied six-cylinder engine. The radiator’s shape was dictated by TVR‘s compromise of mounting the spare tire horizontally above the radiator in order to meet U.S. crash-test mandates. The solution allowed TVR to import its cars into the U.S., but at the price of reducing the efficiency of the vehicle’s cooling system.
It was clear that the TVR’s factory radiator wouldn’t provide the cooling capacity required for our Coyote V-8. But what would replace it? T-Rex’s fabricating guru, John Schiess of Custom Built Machines in Chatsworth, California, has completed several Coyote swaps (see the article on Steve Sanett’s ’58 Ford). He succeeded by essentially mimicking the setup of a late-model Mustang GT. That said, the engine bay of early Coyote-powered FoMoCo cars is decidedly larger than the area available in the T-Rex. An OEM Mustang radiator is nearly 24 inches in height. The accessible space in T-Rex is about two-thirds of that.
How To Fit A Big Square Peg In A Small Round Hole
Now what? Given the limited space, how could we configure the entire cooling system for maximum efficiency?
To provide a solution to T-Rex’s cooling dilemma, two respected specialists lent their expertise: Garry Bell of FSR Products in Memphis, Tennessee, and Don Meziere of Meziere Enterprises in Escondido, California. Not coincidentally, both men are known for their racing acumen.
Bell fields a strong-running ASCS Sprinter, driven by his son Brian — who is a feature race winner in the thick of the Lucas Series Mid-South Region points battle. Don is an NHRA stand out, having most recently won Top Sportsman Eliminator at NHRA National events in Las Vegas and Sonoma. The Meziere family has been winning races for decades and proudly displays eight NHRA “Wallys” in their collective trophy case.
While an OEM Ford mechanical water pump could have been retained, the benefits of an electric water pump were simply too enticing. By eliminating the parasitic drag of a mechanical pump, about 8 to 10 horsepower are freed up — a fairly significant gain. Moreover, the coolant flows through the engine on a more consistent, controlled basis — not dependent on engine RPM — and the engine can be cooled down just sitting in the pits with the electric system running.
The Meziere pump is like a piece of automotive jewelry; it’s machined out of billet-aluminum, polished, and black anodized. Inside is a large diameter stainless-steel mainshaft with high-performance ceramic seals. It moves coolant at up to 55 gpm (free flow) and is powered by a 12v electric motor which has a service life expectancy of 3,000 hours — far more than T-Rex will ever see in a decade or more.
Because a modified serpentine belt system will be employed to drive T-Rex’s repositioned Powermaster Performance alternator, the standard Coyote pump was augmented with an idler pulley to help route the belt (back side contact). Meziere also offers models with an idler pulley to facilitate the use of the factory serpentine accessory belt, as well as a 12-rib blower setup.
Determining the size and configuration of a radiator required to cool the anticipated 550 to 600 horsepower from the Livernois Motorsports-built, 5.0-liter Coyote engine brings several factors into the equation. The available space for the radiator is about 32-inches wide by 16-inches tall. Another limitation is that there is only about 250-square-inches of intake area to feed air to the radiator. To make matters even more difficult, the front sway bar is mounted immediately behind the radiator where it limits fan/shroud positioning.
Given these difficult parameters, Bell and his team came through with a two-pass-radiator design with a thickness of 3 inches and just over 1,000-cubic-inches of core area. With the coolant flowing across the fins in one direction, then doubling back for the second pass, the inlet/outlet configuration of the radiator differs from the OEM Ford design. Now they’re both on the same side.
The radiator-design process itself is rather complex, as there are more parameters than just engine horsepower. The folks at FSR essentially focus on two factors: power and load — which can consist of the car’s weight, application (cruising, racing, etc.), and type of drive (2WD or 4WD). According to Brian Bell, T-Rex falls into the “high power, moderate-to-low load” category.
By employing a custom-built radiator, we had the luxury of choosing the location and size of the inlet and outlet, as well as the type of hose. For the bottom outlet, both Meziere and Bell recommended 1.750-inch inside diameter port. Meziere says, “Any centrifugal pump will rely on a solid column of water present at the center of the impeller, if the low-pressure hose is too small it will not perform to its true potential.” For the top inlet, Bell specified an AN-20 fitting and braided hose. An important consideration is that the coolant is at its hottest here and the braided line provides an extra measure of protection — not to mention that it’s visually compatible with T-Rex’s lubrication system plumbing.
XRP’s popular XR-31 3-ply hose, which is rated to 300-degrees-plus F, and fittings were employed. Then there was also the matter of the lower radiator hose and the routing between cylinder heads, the Moroso expansion tank, and the radiator. Rather than use factory-type rubber hoses, T-Rex was upgraded to silicone hose from HPS, a quality hi-temp hose that’s rated to 350-degrees and exceeds SAE J20 specs, with routing accomplished using 1.250-, .750- and .312-inch elbows, tubing, and hose all secured with HPS stainless steel clamps. A reducing elbow facilitated the transition from the 1.750-inch radiator outlet to the 1.500-inch water-pump inlet line.
A variety of OEM Ford components were also required to route the water, while a Moroso Aluminum Expansion Tank (p/n 63806) supplies the coolant to the radiator. It’s a replacement unit for the 2015-2017 Mustang’s plastic tank and uses an OEM vented cap. The billet-aluminum neck has a built-in overflow.
Incoming Airflow Is Key
However, circulating the coolant is only half the battle. Getting air across the radiator fins is of equal importance. Given the small TVR grille opening, much of the work will have to be done by powerful “puller” electric fans positioned behind the radiator.
According to Meziere, “It’s important to consider airflow, making sure there is a well-defined high-pressure area in front of the radiator when a vehicle is at speed, and a well defined low-pressure area to help the hot air escape once it has passed through the radiator.” Don went on to say, “In my opinion, a complete core support and spoiler is essential for directing air into the radiator and then capture as much as possible.”
Dual Fans To The Rescue
An initial look at industry offerings proffers up all manner of blade designs and counts, plus electric motor and control options. To get the most efficient setup we turned SPAL, the world renown Italian firm with U.S. offices in Iowa.
Cooling fans are considered to be big “amp-eaters,” and can easily draw over half of the electrical system’s current. In recent years though, this situation has been mitigated through a new generation of brushless motors that feature magnets positioned on the spinning rotor inside of a stator (winding), instead of the standard design with a commutator rotating inside of electrically charged brushes that contact the windings — adding friction. Brushless advantages include high-output power, compact size, better heat dissipation, higher-speed ranges, and more quiet operation. Of course, there are trade-offs for this efficiency, as a complex controller is required that adds to the expense. But, given the added performance and long service life, the new technology won out.
Temperature control is, of course, extremely important. Brian Bell at FSR recommended the engine be equipped with a 160- to 170-degree thermostat, which would allow the engine to build a modicum of heat early on. Then the temperature control of the Spal cooling fans would take over; his choice was a 185-degree setting. With T-Rex’s dual fan setup, the controller starts with one fan operating at 50 percent. As the temperature rises so does the fan speed, subsequently, the second fan kicks in.
Racetrack Legal Coolant
Of course, everything depends on the coolant itself. In the case of T-Rex — which will compete in some venues that prohibit the use of glycol-based coolants because of potential discharge of the slippery stuff onto the track — T-Rex’s cocktail of choice is water fortified with Purple Ice from Royal Purple. The product elevates the system’s boiling point and also helps prevent corrosion in the aluminum engine and radiator.
So, thanks to a cadre of aftermarket companies and Ford, we now have a cooling system that is designed to keep T-Rex cool and happy in all environments from cruising to racing.