Power Limits of the S550 Coyote

• The block: all aluminum, with thinner walls than the previous iterations
• Forged steel crankshaft
• Hyperutectic pistons with oil jets underneath for cooling
• 4 valves per cylinder
• Powdered oil pump gear which doesn't always play nice at high RPMs

As already mentioned, the Coyote 5.0L is an all aluminum motor. Lightweight and strong, the block is cast from 319 aluminium with a bore spacing of 100mm, a deck height of 227mm and a deck thickness of 13mm. The cylinder walls feature thinner, pressed-in iron sleeves, resulting in a bore diameter of 92.2mm, which is 2mm larger than the previous 4.6 engine. This extra 2mm was achieved by the above mentioned thinner cylinder sleeves. However, despite the cylinder linings being thinner, overall integrity was not compromised. Released as a naturally aspirated engine, Ford originally did design the new Coyote engine to be capable of accommodating a power adder down the road. Therefore, at 435 horsepower, the Coyote is nowhere near tapped out. The aftermarket has shown that these blocks remain in one piece even when harboring double the stock output.

2011 5.0L engines rolled out of the Essex assembly plant with a forged steel, counterweighted crankshaft. The connecting rods, of the I-beam variety, are powdered-metal. Connected at the top end are hypereutectic pistons. Ford engineers have specified the weakest link in the Coyote engine to be the powdered-metal rods, and have since corrected the design in the S550. S550 Mustangs harbor Forged rods rather than powdered metal.

Most people groan when they hear about hypereutectic pistons being used, and it’s true. They are not as robust as their forged counterparts. However, Ford integrated oil cooling jets that spray the bottom of the piston at all times, helping keep their temperature down which increases their overall durability. The stock hypereutectic pistons are very comfortable at 435 horsepower, and definitely have more room to grow. On the other hand, those wishing to slap on a power adder and push some serious boost through the motor will definitely want to change the stock pistons with a forged variety. In stock trim, it seems the realistic limit of the stock rotating assembly is around 600 horsepower to the wheels (depending on drive train loss, can equate to 750-800 horsepower at the crank). Nonetheless, that is mighty impressive!

The cylinder heads on the Coyote are game changers; there is no doubt about that. The aluminum, 4-valve per cylinder heads are a major reason the Coyote engine is able to produce over 400 horsepower from a displacement of only 5.0L. These new heads are highly efficient and have excellent flow. Actual flow numbers are hard to come by, but it is highly speculated that they flow around 300 CFM out of the factory. As a production piece, this is an astonishing number! Unlike the previous E7TE cylinder head of the Foxbody generation, the S550 are not a restriction.

Ah, the oil pump gear – a blast from the past! Considerable concern has risen regarding the stock powdered-metal oil pump gear that comes equipped with a stock Coyote engine. Like previous modular Mustangs, at higher RPM and power levels (particularly with a boosted Mustang), oil pump gears are failing. High power loads at high RPM (usually from a supercharged or turbocharged engine) can cause the crankshaft harmonics to change and be passed on to the oil gear pump. Subsequently, the stock powdered gear is quickly fatigued and ends up shattering, leaving a big mess inside the engine. For Mustangs that spend a lot of time at the track and in the upper RPM’s, changing the oil pump gear is considered a wise choice. Unfortunately, it is a pretty big job!

Unfortunately, it is very hard to define a be-all-end-all limit for the new Coyote engine. Like the old 5.0L pushrod V8, numbers vary all over the place. However, the general consensus is the new Coyote can live comfortable and reliably at 750 crank horsepower. Getting this kind of power out of the S550 will of course necessitate the addition of a power adder, but as long as the car is configured and tuned properly, the stock pieces should be fine up until then. As mentioned, the major weak point in the S550 as it stands the hypereutectic pistons.

As far as the rest of the drivetrain is concerned, a general rule of thumb is that of the engine itself. It is always a good idea to add a driveshaft safety loop for any higher horsepower application. The higher stress levels (hard launches, wheel hop, etc) will cause failure faster, regardless of horsepower levels.

How much power can the MT-82 take? The ​transmission is rated to handle 383 ft/lbs of torque in stock form. Though, with all the power of the mighty Mustang, Ford has beefed up the trouble child transmission for the S550. The issues Ford has addressed deal with bad hardware and shift response, not necessarily how much power can be run through it. If you plan on tracking your car frequently you will want to address the internals or move to a beefier transmission. The Mustang is a passenger car built for daily driving after all. If the limit is pushed and the transmission if left be, broken input shafts are a common result of beating on this particular transmission.