Usage:
3406B Truck Engines
- SUPPLEMENT: 09/30/85
SERVICE MAGAZINE, JANUARY 21, 1985, PAGE 9, "Exhaust Brake Performance Increased". In the article, manifold back pressure should be 345 kPa (50 psi) instead of 240 kPa (50 psi) that is given. This appears three times.
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The exhaust brake performance capability of the 3406B Truck Engines has been increased. The maximum exhaust back pressure at maximum braking rpm is now 345 kPa (50 psi). The maximum exhaust back pressure was 240 kPa (35 psi) at 2100 rpm on the former 3406 (92U) Truck Engine.
Back pressure for exhaust brake application is measured at the 1/4" NPT hole in the exhaust manifold closest to the turbocharger.
Differences in available exhaust braking devices vary from those with little or no leakage to those with considerable leakage. Sliding gate type exhaust brake devices allow minimal leakage and must have a relief orifice to limit the maximum exhaust manifold back pressure to 345 kPa (50 psi) at maximum engine braking rpm. The orifice sizes required for 3406B Truck Engines are shown in the chart.
With a "flapper-type" exhaust brake, there is usually leakage around the moveable plate and a smaller hole is needed to obtain 345 kPa (50 psi). Use the method that follows to obtain the correct exhaust back pressure when using a "flapper-type" exhaust brake.
1. Drill a 8.46 mm (0.333") hole in the plate.
2. If there are adjusting screws, back them out so there is no clearance between the plate and housing.
3. Connect a pressure gauge to the 1/4" NPT at the exhaust manifold outlet flange.
4. Operate the truck and read the back pressure when the exhaust brake is applied.
5. Modify the hole in the plate to obtain 240 kPa (50 psi).