Ford F-250 Bolt-on Exhaust Brake

Diesels are great engines for tow vehicles. They twist out enough torque to get any load moving without the bad fuel-gulping habits of a big-block engine. But when you ask them for some compression braking to slow you down on a steep grade, they can't hold a spark plug to a gas engine. Now you know why diesel trucks come with such big service brakes!

The reason diesels run away from you on hills is simple: Gasoline engines have throttles that close when you lift your foot from the accelerator pedal. Diesels don't. Sure, you can take your foot off the accelerator pedal in a diesel truck and that will limit the fuel supply to the engine but it does nothing to limit the amount of air being sucked into and pushed out of the engine. In a gasoline engine the closed throttle plate causes a massive restriction that the pistons have to try to suck air past. This restriction causes drag in the engine that slows the truck. For all intents and purposes diesels have an unrestricted air supply at all times, so in order to produce engine drag the exhaust brake was developed.

The Banks Brake system for Power Stroke engines redefines the word "complete." The base kit shown here for '99-and-up Super Duty trucks costs $1,199 and includes the brake, down pipe, compressor, and every single zip tie, electrical connector, and hose clamp you could ask for to complete the installation.

Knowing that many of you own diesels (or want to) and experience diesel engine runaway, we wanted to see first-hand how well an exhaust brake upgrade works. We borrowed Off Road Unlimited's F-250 and drove out to Azusa, California, to follow along as Banks Engineering installed its Banks Brake and SmartLock transmission controller. Typically it takes five hours for Banks to install this system on a Super Duty, but plan on a day if your truck is lifted like ORU's. With the system installed we experienced a drastic improvement in engine braking whenever we turned it on. When the Banks Brake closes its restrictor valve there is a distinct but muted whoosh sound accompanied by a tremendous amount of engine braking (more than any gasoline engine could produce). The system is designed to work seamlessly with the rest of the truck and will disengage the brake when vehicle speed is less than 15 mph or engine speed drops lower than 1,600 rpm. Banks reports that some drivers will leave the system on at all times, and that doing so has no ill effects on the system or truck.

For more information on the Banks Brake (systems for Cummins and Duramax engines are also available) or any Banks product check out www.bankspower.com. The gas truck guys already admire your diesel's pulling power; now Banks will make them beg for its braking power too.

You don't have to remove the turbocharger from the engine to install a Banks Brake, but don't be afraid to if you're working on a lifted truck or run into some stubborn fasteners. Either way you'll need to remove the seven bolts that hold the stock warm-up valve/exhaust outlet combination from the turbo and replace it with the new Banks Brake/exhaust outlet combo.	There's a shortage of workspace in the engine compartment of Power Stroke-equipped Super Dutys and Excursions. Take your time and mark everything that you have to remove to gain access to the turbo when installing the Banks Brake.	With the new hardware in place it's time to move on to plumb the vacuum lines and electric switch to control the Banks Brake. When energized, the vacuum-operated canister (arrow) will pull the brake valve closed to restrict exhaust flow as it leaves the turbo. This restriction builds exhaust pressure in the engine and drastically increases the engine braking available with diesels.
Diesel engines don't produce manifold vacuum like gasoline engines do, so Banks supplies a vacuum pump to power its brake. This compressor mounts under the truck to the passenger-side framerail, but don't worry; it draws filtered air from high up in the engine compartment.	As a bonus the Banks Brake is actually less restrictive than the stock turbo exhaust outlet. So much so that Banks offers the cast elbow and down pipe without the brake as an exhaust upgrade for $295. In order to take advantage of the new flow potential (and to adapt the exhaust to match the new turbo outlet) Banks includes a new exhaust down pipe that must be installed in the exhaust system. Installation of the Banks pipe is easy--removing the Ford piece may require an acetylene torch.	To get maximum performance from the Banks Brake on automatic-transmission-equipped trucks you'll want to buy the optional Banks SmartLock transmission controller ($395). This unit works with the factory powertrain controller to lock up the torque-converter clutch in all four gears and to increase transmission line pressure whenever the Banks Brake is activated. It not only improves the performance of the brake, it also decreases transmission temperatures by limiting the amount of transmission slippage during hill descents.

So How Does It Work?
Flip the dash-mounted switch to the "On" position and the Banks Brake will close its exhaust valve to slow the engine and vehicle whenever you take your foot off the throttle. The higher the engine rpm the more impressive the effect. Even with our test vehicle's 38-inch tires the Banks Brake slowed the truck down (in Second gear) like we were caught in a tractor beam. With a trailer attached the brake improvement is even more noticeable--it's like the difference between having trailer brakes and not having them. This upgrade is essential for diesel owners who need more braking power.