The part is a critical component that directs exhaust gases from the turbocharger outlet to the exhaust pipe or aftertreatment system on the HOWO MAX 4X2 MC13 engine. This exhaust elbow integrates a braking butterfly valve that provides engine braking functionality, improving vehicle control on downhill grades. When you choose authentic Howo Parts, this exhaust elbow guarantees OE fitment, leak free sealing, and reliable exhaust brake operation. Below are detailed descriptions of every component included with this exhaust elbow assembly.
The part is a cast stainless steel or high silicon ductile iron component that connects the turbocharger outlet to the exhaust downpipe. This exhaust elbow incorporates a pneumatically or electrically actuated butterfly valve that restricts exhaust flow when activated, creating backpressure in the engine and providing engine braking power. The valve consists of a stainless steel butterfly plate, a shaft with bronze bushings, and a pneumatic actuator that receives air pressure from the vehicle’s air system when the driver engages the exhaust brake switch.
The part is designed to withstand continuous exhaust gas temperatures up to 800°C and pulsating pressures up to 4 bar. The internal bore is smooth to minimise flow restriction when the valve is fully open, reducing turbo lag and maintaining engine efficiency. The part includes a mounting flange with six threaded holes that accept the flange bolts. A correctly functioning exhaust elbow with braking butterfly valve can provide up to 100 kW of retardation power, significantly reducing brake wear on long descents and improving safety.
Six flange bolts are used to secure The part to the turbocharger outlet flange or to the exhaust pipe flange. These exhaust elbow bolts are made from heat resistant alloy steel with a property class equivalent to 10.9 at elevated temperatures. Each bolt features an integral flange that distributes clamping load evenly across the flange, eliminating the need for separate washers. The bolts have a zinc nickel coating to resist corrosion from exhaust condensate and road salts.
The thread size is typically M10 x 1.5 with a length of 30mm or 35mm depending on the specific application. These exhaust elbow bolts must be torqued to 45 Nm in a crossing pattern to ensure a gas tight seal of the exhaust joint. The bolts are single use fasteners; once they have been torqued, the thread locking patch is crushed, and they should not be reused. A loose exhaust elbow bolt can cause exhaust leaks, which result in loss of turbo boost pressure, increased noise, and the risk of hot gas damage to nearby components.
Exhaust elbow – genuine HOWO high flow exhaust elbow with integrated braking butterfly valve for MAX 4X2 MC13
This exhaust elbow incorporates a pneumatically actuated butterfly valve that provides up to 100 kW of engine braking power. The exhaust brake reduces the load on the service brakes on long downhill grades, preventing brake fade and improving vehicle safety. The valve is controlled directly from the cab switch and engages within 0.2 seconds.
The part is cast from 309S stainless steel or high silicon ductile iron, capable of withstanding continuous exhaust gas temperatures up to 800°C and intermittent temperatures of 900°C. The material resists oxidation, thermal fatigue, and cracking, ensuring long service life under heavy duty conditions.
The mounting flange of The part is machined flat to within 0.05mm, ensuring a perfect seal when mated to the turbocharger outlet. The six flange bolts provide even clamping force, eliminating exhaust gas leakage that would cause loss of turbo boost and a hissing noise.
The six flange bolts supplied with this exhaust elbow are made from heat resistant alloy steel (equivalent to grade 10.9 at high temperature) with a zinc nickel coating. They include a pre applied thread locking patch that activates during installation, preventing loosening under the extreme vibration of a diesel engine.
The part is mounted directly onto the turbocharger turbine outlet. Under normal driving conditions, the butterfly valve inside The part is fully open, allowing exhaust gases to flow freely to the exhaust pipe and out through the tailpipe. When the driver engages the exhaust brake switch on the dashboard, a solenoid valve sends compressed air (typically 8 bar) to the pneumatic actuator mounted on The part.
The actuator rotates the butterfly shaft, closing the valve to a calibrated position that restricts exhaust flow. The restriction creates backpressure in the exhaust manifold, which opposes the engine’s pistons on the exhaust stroke, effectively turning the engine into an air compressor that absorbs power. The result is a strong retardation force that slows the vehicle without using the service brakes. The butterfly valve never closes completely; it typically stops at 80–90% of full closure to prevent excessive backpressure that could damage the turbocharger or push exhaust past the piston rings.
The part’s internal bore is designed to maintain laminar flow when the valve is open, preventing turbulence that would reduce turbocharger efficiency. The integrated braking butterfly valve can be activated and deactivated repeatedly without damage, making it ideal for long downhill descents. In the HOWO MAX 4X2, the exhaust brake is interlocked with the transmission and foot throttle; it automatically disengages when the accelerator pedal is pressed or when the engine speed falls below a preset threshold (typically 1000 RPM).
Before installing The part, allow the exhaust system to cool completely. Remove the old elbow and clean the turbocharger outlet flange and the exhaust pipe flange. Inspect the gasket surfaces for damage. Apply a thin film of high temperature anti seize compound to the flange bolt threads. Place a new exhaust gasket (sold separately) between the turbo flange and The part flange.
Position The part so that the butterfly valve actuator is oriented correctly (usually facing outboard for access). Insert the six flange bolts by hand to ensure they do not cross thread. Torque The part bolts in a crossing pattern to 45 Nm using a calibrated torque wrench. Reconnect the pneumatic line to the actuator (ensure no kinks). Start the engine and check for exhaust leaks around the flange;
a soapy water solution will bubble if there is a leak. Test the exhaust brake by engaging the switch at 1500 RPM; a distinct change in engine note should be heard, and the vehicle should decelerate when coasting. The part installation is now complete.
If the exhaust brake does not engage when the switch is activated, first check the pneumatic supply to the actuator. Listen for a click from the solenoid valve; if no click, the switch or solenoid may be faulty. If the actuator moves but the valve does not close, the butterfly shaft may be seized due to carbon buildup. Remove The part and inspect the butterfly plate; clean with a wire brush and high temperature penetrating oil. If The part produces a hissing noise under load,
the flange gasket may be leaking or one of the flange bolts may be loose. Retorque the bolts to 45 Nm; if the leak persists, replace the gasket. A rattling sound from The part when the brake is not engaged indicates a loose butterfly plate or worn shaft bushings; replace The part immediately, as a detached plate could enter the aftertreatment system. If the engine loses power even when the exhaust brake is off,
the butterfly valve may be stuck partially closed. Remove the actuator linkage and manually check valve movement; if it does not return to fully open, replace The part. Loss of exhaust brake effectiveness over time may be due to carbon deposits reducing valve sealing; periodic cleaning (every 150,000 km) is recommended.
The part itself has no fixed replacement interval, but it should be inspected at every major service (every 100,000 km). Check the butterfly valve for smooth operation by moving the actuator arm by hand (when the engine is cold and air supply disconnected). Inspect The part for cracks, especially around the welds where the actuator bracket attaches. The flange bolts should be checked for tightness; retorque to 45 Nm if any are loose.
The exhaust gasket should be replaced whenever The part is removed for any reason. The pneumatic actuator and solenoid valve are serviceable components that can be replaced separately; they are not included in this exhaust elbow kit. If the exhaust brake becomes sluggish, the actuator diaphragm may be leaking; replace the actuator. Apply a small amount of high temperature grease to the butterfly shaft bushings every 200,000 km to prevent seizing. Keep the area around The part free from oil leaks, as burning oil can cause carbon deposits that interfere with valve movement.
This exhaust elbow is specifically designed for the SINOTRUK MC13 engine used in HOWO MAX 4X2 tractors, SITRAK C7H, and HOWO T7H trucks. It fits all production years from 2018 onward and is compatible with both Euro 5 and Euro 6 emission engines. The part is also suitable for the MC11 engine platform, though the downpipe connection may differ.
This exhaust elbow is not compatible with older WD615 or D10 engine series, which use a different turbocharger outlet flange pattern. Always verify your engine serial number before ordering this exhaust elbow. For vehicles equipped with a compound turbocharging system, a different exhaust elbow may be required; consult the vehicle’s parts catalog.
Aftermarket exhaust elbows are often made from lower grade cast iron that cracks under thermal stress, leading to exhaust leaks and potential turbocharger damage. Generic butterfly valves may not have the correct shaft seal material, allowing exhaust gases to leak past the bushings and into the engine bay, creating a hazardous environment.
The flange bolts in copy kits may not be rated for high temperatures and could fail, causing The part to separate from the turbocharger while the engine is running – a serious safety risk. Non genuine exhaust elbows may not have the precise internal bore geometry required to minimise backpressure, reducing engine power and fuel efficiency.
Genuine HOWO exhaust elbow components are manufactured to SINOTRUK’s exact specifications, using certified high temperature alloys, precision machined flanges, and heat treated fasteners. The small additional cost of a genuine exhaust elbow is insignificant compared to the cost of a turbocharger replacement or, worse, an engine fire caused by an exhaust leak igniting oil or fuel vapour.
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