Warning:

Ford does not look kindly to the installation of exhaust brakes on the Powerstroke. Regardless of what any after market manufacturer claims, unless they are willing to pick up where Ford says NO, installation of ANY exhaust brake may cause you to be left in the dark if Ford feels your exhaust brake constitutes voiding of the warranty. Though this may not correlate with the theory of the Magnisum Moss act, it is the practical reality.

 

Background

Anyone that drives a Diesel will soon realize that compression braking is not as significant as when driving a gasoline powered truck; the reason for this lies in the fact that the diesel does not utilize a throttle body to regulate airflow. When the accelerator is lifted on a gasoline engine, the throttle body (or carburetor) closes to restrict airflow. This generates pumping drag on the motor, which is ultimately felt in compression braking. Because the diesel works off the principle of regulating fuel and is allowed to pump as much air as needed (or possible), it does not have any throttle valve to restrict airflow at idle. Therefore, the only compression braking felt is that from the engine compression or energy dissipated through losses in the drive line, such as accessories and cooling fans. For this reason the infamous Jake brake was developed for big rigs and exhaust brakes have been developed by after market manufacturers for the light duty diesels. It should be noted that Jake Brakes are not the same as Exhaust Brakes. This article focuses on Exhaust brakes, for more information on Jake Brakes visit ??.com .

All an exhaust brake does is create a restriction in the exhaust flow to help generate pumping drag on the motor. Several forms of exhaust brakes are available, but most of them utilize an actuated valve that plugs the exhaust flow. While several brakes mount directly to the turbo housing (BD, ??.com & Pac Break, ??.com ), others mount downstream on the exhaust pipe (US Gear, ??.com). As an additional benefit, exhaust brakes can also be used to help warm up the motor during cold starts by generating additional pumping restriction. Based on this warm up principle, Ford incorporated a warm up valve directly into the stock turbo housing on the PSD. When the conditions are right, the ECM will raise the idle and close the valve to help warm the engine. While aftermarket exhaust brakes from various manufacturers provide superior compression braking, as an inexpensive alternative this factory warm up valve can be wired to operate as a mild exhaust brake.

In the OEM fashion, this factory warm up valve is actuated by oil pressure from the turbo pedestal. To close the valve, the ECM sends a signal to the EPR (exhaust pressure regulator), a solenoid that directs high-pressure oil to the EBV (exhaust back pressure valve) to close it. The ECM also utilizes an exhaust backpressure (EBP) sensor to close the control loop, allowing it to control backpressure under cold conditions. Because of the electrical / hydraulic actuation, the EBV takes ~2 seconds to fully close once a signal is sent to the EPR. By manually providing a signal to this EPR, the driver can close the EBV, using it to help increase pumping loss for compression braking. Though this can be accomplished through several different wiring schemes, one specific approach will be outlined. Features to minimize any permanent modification to the factory wiring harness, implement cancellation of cruise control operation during usage, use of the factory IVS (idle validation switch) to engage the exhaust brake, and retention of the OEM warm up valve operation will be worked into the circuit. Information regarding locking the torque converter will be mentioned, but not illustrated. Some alternative wiring schemes for activating the "exhaust brake" through the brake peddle, manual foot switch, or factory converter lock up signal will also be touched upon.

 

Explanataion of Key Components

Picture of IVS Connector

IVS Circuit

The Ford Powerstrokes utilize an Idle Validation Circuit (IVS) to help tell the engine computer that the accelerator is not depressed and the engine should maintain an idle. This little circuit is simply a micro switch mounted to the accelerator peddle assembly. When the pedal is depressed, 12 volts are sent to the ECM. When the accelerator is not depressed, the switch is open so 0 volts are sent to the ECM. Since the IVS circuit is fed by a hefty power source the 0 / 12 volt signal can be used with relays to activate various accessories. For example, besides using it to activate an exhaust brake, the same signal could be used to activate a propane system or the "10 K resistor trick"

Picture of MC Pressure Switch

Brake Pressure Switch

If you have ever used cruise control, you should have noticed that it cancels when the brake is applied. Ford accomplishes this through use of a pressure switch mounted in the front of the brake master cylinder. When the brakes are not applied, the switch is closed; allowing electricity to flow through the circuit. As soon as the brakes are applied the pressure in the system opens the switch, opening the circuit and preventing the electricity to flow. When the ECM sense this, it cancels cruise control.

Picture of EPR

Picture of EBV

EPR & EBV

Please refer to the background section for a description of these components. Figure ?? and ?? illustrate their respective locations.

Figure??: Diode

Diodes

Diodes are one way electrical devices, similar to one-way air check valves. Essentially a Diode allows current to flow through in one direction, but block current in the opposite direction; that is until the reverse break down voltage of the diode is surpassed. In the diode shown in Figure ?? electricity is allowed to flow in the non banded end and out of the terminal (side) that has the silver band.


Figure ??: Relay

Relays

Relays are simple electrical devices that act as switches. Instead of physically switching the relay, a small power source is used to electrically switch it. By doing this, small power sources can be used to switch on power to components that require more electrical power then the small source can deliver. Aftermarket driving lights are a perfect example of this application. Lastly, relays allow the high power circuit to be isolated from the low power switching circuit.

Relays are very simple in operation. Essentially a small coil inside the relay physically moves a switch through electromagnetic properties generated by the coil when it is powered. There are 5 possible connections to a relay, numbered 1 through 5 in figure ??. Alternatively another common labeling scheme for automotive relays is 85, 86, 30, 87A, and 87 respectively. The first two connections are the coil. One end of the coil (1 or 85) is connected to the switching power source while the other end (2 or 86) needs to be grounded. The remaining three connections are for the "relay switched" circuit. The first is for the source to be switched (call this common), the remaining two are the possible switch connections. When the coil is not powered, the relay’s switch will connect the common (3 or 30) to one of the two remaining terminals (4 or 87A). This allows electricity to flow from the common to terminal 4 (or 87A). When the coil is energized by a low power source, the relay’s switch will now connect the common to the last terminal (5 or 87). This disconnects the power from terminal 4 (87A) and allows it flow out terminal 5 (87).

Based on this simple design, the relay can be used to either open (disconnect) or close (connect) a circuit when a low power electrical signal is applied to the relay’s coil.

Lastly, when coils are suddenly de-energized they produce a reverse voltage spike that can damage electrical components in the system. Often this reverse voltage spike does not create a problem. Regardless, by shunting the relay’s coil with a diode (banded end on the coils positive terminal, 1 or 85), any reverse voltage generated will be immediately grounded; alleviating any possible damage to other components.

 

Wiring Schematic & Component Functions


Figure ??: Wiring Schematic

SPST Switch:

This is a Single Pole / Single Throw (SPST) switch used to activate the system. This switch should be connected to an ignition switched source. For this article a PainlessWiring Accessory Fuse Block is used as the ignition switched source. For details on the Painless Wiring Accessory Fuse Block, see the article written outlining its installation.

Relay #1:

This relay is used to connect the IVS signal to the coil of Relay #2 when the system is activated (relays coil energized). Without it, the IVS would always activate Relay #2, whether or not the system is activated. This could prove to be annoying if a relay with audible clicking was used.

Relay #2

This relay is what applies the voltage to the EPR when the accelerator pedal is not depressed (IVS = 0 volts). A diode is used to help isolate the "Exhaust Brake" circuit from any voltage applied to the EPR by the factory warm up circuit.

Relay #3

This relay is used to open the "break pressure switch" circuit used by the ECM to cancel cruise. It works in series with the factory brake pressure switch, so that cruise control can either be cancelled by applying the brakes or by applying power to relay #2.

EPR Activate LED

This LED is optional and used to show when voltage is sent to the EPR, whether from the ECM or "exhaust brake". This is an optional component.

Figure ??: EPR extension harness

EPR Extension Harness

This is a harness fabricated so that the EPR circuit can be tapped into without cutting the factory wires. The original EPR warm up signal is sent through a diode to isolate the ECM from any voltage applied by the "Exhaust Brake" circuit.

Picture of BPS extension harness

Brake Pressure Switch Extension Harness

This is a harness fabricated so that the brake pressure circuit can be tapped into without cutting the factory wires.

System Operation

When the system is activated by the SPST switch, voltage is applied to Relay #2’s common terminal (to eventually power the EPR) and Relay #1’s coil (triggering it to connect the IVS signal to Relay #2’s coil). Thus when the accelerator is not depressed, Relay #2 will send voltage from the common terminal, through the diode, to the EPR. Simultaneously, voltage is sent to Relay #3 to open the "break pressure circuit", telling the ECM to disengage cruise control. After voltage is applied to the EPR, oil is allowed to flow to the EBV; closing it in ~2 seconds. As soon as the accelerator is depressed causing the IVS to go to 12 volts, Relay #2 will disconnect voltage from the EPR and Relay #3, opening the EBV and allowing cruise to function once reset. This is important when the idea of using the brake peddle or foot peddle to activate the "exhaust brake" is touched upon.

 

Example of Components Used

The following is a list of sample components used to implement this home built exhaust brake. Several of these components are generic and equivalent components may be substituted. In addition, depending on what custom features you choose to add, different components may better suit your actual application.

Part Description

Where To Purchase

Part or Model Number

SPST Switch

Electronic / Hardware store

 

Diode – 100 V, 3 A

Radio Shack / Digi-Key

1N5401

Diode – 1000 V, 1A

Radio Shack / Digi-Key

1N4007

12 Volt Red LED

Radio Shack

 

EPR Male Conn

( what is it for??)

Napa

Pep Boys

Echlin #2-18462

????

Bake Pressure Switch Conn.

(What is it for)

Napa

Pep Boys

Echlin #

Conduct Tite #85850

Three 20 A, 12 V Relays

Radio Shack

 

EPR Female Conn

( ??????)

Radio Shack

 

EPR Female Conn

(?????)

Napa

Pep Boys

Echlin #

Conduct Tite #85197

Male & Female Spade Conn

(0.25", 0.18", & 0.20")

Electronic / Hardware store

 

Assorted Heat shrink tubing

Electronic / Hardware store

 

Assorted Zip Ties

Electronic / Hardware store

 

3M Taps

Electronic / Hardware store

 

3M Industrial Velcro

Electronic / Hardware store

 
     
     
     
     
     

 

Most of these components can be purchased from Radio Shack (whether at your local store or online), Digi-Key, Napa Auto Parts, or hardware store.

Some custom components used in this installation is the shifter switch & LED mounting bracket for a 6 speed shifter; along with a length of 4 wire, 18 ga wire bundle.

 

Fabrication & Installation

Figure: RS connector

EPR Extension Harness

First the straight leads of the "Radio Shack" connector are shortened to be even with the plastic tab and filed to de-bur, while the angled leads are straightened. Directly solder the Napa connectors "A" wire to the respective straightened terminal on the Radio shack connector. Solder both a longer extension wire and 100 volt, 3 amp diode to the other wire (wire "B") of the Napa connector. Make sure the banded end of the diode points toward the Napa connector. The longer extension wire will be used for tying in the "Exhaust Brake" activation power. The other end of the diode (non banded end) should be soldered to a short extension wire that is then to be soldered to the remaining pin on the Radio Shack connector. All solder junctions should be sealed with heat shrink tubing.

An alternative is to use the ???? connector instead of the Radio Shack connector. This connector comes with wires and is the general shape of the factory EPR plug, unfortunately the pin spacing on this connector are slightly wider then the EPR plug. If this connector is to be used, just substitute it for the Radio Shack Connector in the directions above and slightly bend the pins together to close the spacing to match the factory EPR plug.

Picture of components

Brake Pressure Switch Extension Harness

Match up the wires from the factory brake pressure switch plug to the new connector. Solder the wire on the new connector that corresponds to the ???? wire on the factory connector to the Ford mini spade connector. Solder the other wire from the new connector to an extension wire that will be used to route the circuit to your "cruise cancel" relay. Solder another Ford mini spade connector to a second extension wire that will be used to return the circuit back to the factory plug. The required lengths of the extension wires will depend on where you mount the relay.

Picture of Relays # 1 & 2

Connection of Relays

Though it may not be required, a 1000 volt, 1 amp diode was soldered across the coil leads of all the relays to help drain any back voltage when the relays trigger in and out. Relays # 1 & 2 were taped together and the wires were connected to make a compact unit with only the IVS signal (yellow wire), Exhaust Brake activation (green wire), system power (red wire), cruise cancel relay activation (orange wire), and ground wires (black) coming off. These relays will be mounted under the dash. One diode was soldered inline with the IVS signal wire with the banded end towards the relays. Another diode was soldered inline with the Exhaust Brake Activation wire, but after the cruise control cancel relay activation wire, with the banded end facing the EPR.

Figure ??: Mounting Bracket

System Activation Switch and Activation LED Mounting

Because this particular installation was made on a 6-speed truck, it was decided to mount the switch and LED on a bracket fabricated to clamp on the shifter lever. The drawings used to machine the bracket can be viewed in figure ?? and ??. To prevent any scarring of the factory shifter lever, the clamping surface of the mounting bracket was lined with electrical tape. To complete the wiring a 4 wire (18 ga) gray conduit that was picked up at a local electrical store was used to run the wires down the lever and under the dash.

Drawings of both Bracket Pieces

An alternative to the shifter bracket is to mount a switch somewhere in a free part of the dash. One popular location is the flat shelf like area directly left of the steering wheel or the ESOF switch plate.

Installation

For this installation industrial Velcro was used to mount the relays. The 12 volt switched power was picked up from the Painless Wiring Accessory fuse box (see Painless Install article), run through the system switch, and then connected into the relays. The ground wire was connected to an existing ground point under the dash, and the factory supplied customer accessory wiring was used to run the cruise control cancel signal to the engine compartment. The EPR activation wire was run through the accelerator cable hole (see Painless Wiring Install) because this application was a 6-speed, but the clutch mounting hole knock out would be another appropriate location for trucks equipped with an automatic transmission. The LED activation wire was tied into this EPR activation wire (downstream of the diode) so that it will illuminate whenever the EPR is activated by the Exhaust Brake or the Warm up Circuit. The IVS signal was tapped into by using a 3M ??? taps. The tap was used with a small extension wire that had a spade connector on the end so that it could be zip tied to the factory wiring bundle, cutting down on any wire tension that may causes the junction to go bad. This also allows the signal wire to the relays to be disconnected at any time without having to remove the ??? tap.

Mounting Pictures for Relays & Connection Wires

The Cruise Control Cancel relay is mounted near the master cylinder with industrial Velcro. The activation signal was picked up from the factory accessory wires and extended to the relay, while a small sheet metal screw was used to provide a grounding point on the fender.

Mounting of Cruise Relay

Lastly, the EPR and BPS extension harness’s were installed, the EPR activation wire connected to the EPR extension harness lead (green wire), and the extension wires from the BPS harness (yellow wires) were connected to the appropriate relay terminals.

Installation of the Extension Harness’s (2 pics)

 

Testing System Operation

Explain how to do a quick road test

Some system experimentation

Deceleration tests using a G-Tech like device to determine change in braking affect with varying voltage / current to the EPR.

Alternative Wiring Variations

Introduce and discuss wiring variations for interfacing with the converter lock up; such as only activating the Exhaust Brake when the ECM locks the converter or manually locking the converter when the Exhaust Brake is activated. Lastly, possible alternatives that can be developed with the proper electronic knowledge will be touched upon, as well as some available products for converter lock up control that are already available on the market.

 

 



Some temporary links to pictures until the article is completed


Look at the exhaust brake wiring diagrams Bearwasel posted

Here is a picture of the extension harness

Here is a picture of the harness plugged into itself, demonstrating how the modified Radio Shack connector should plug into the factory EPR connector.

Here is a picture of the Radio Shack connector. The top one is after modification and the bottom is as purchased.

Here is a picture of the bracket, switch, and LED mounted to the lever.

This is another picture from a different angle