Exhaust Restriction

TM 9-2320-312-24-2

Testing and Adjusting Section

e. Multiply the value from Step 4.d by 1.8.

f. Compare the result from Step 4.e to the

appropriate values that follow.

The air flow through a used engine air cleaner

may have a restriction. The air flow through a

plugged engine air cleaner will be restricted to

some magnitude. In either case, the restriction must

not be more than the following amount:

Maximum restriction .... 6.2 kPa (25 inch of H2O)

The air flow through a new engine air cleaner

element must not have a restriction of more than

g00293196

the following amount:

Illustration 54

1U-5470 Engine Pressure Group

Maximum restriction .... 3.7 kPa (15 inch of H2O)

Refer to Special Instruction, SEHS8907, "Using

Exhaust Restriction

the 1U-5470 Engine Pressure Group" for the

instructions that are needed to use the 1U-5470

Engine Pressure Group. Refer to Operation Manual,

NEHS0818, "Using the 198-4240 Pressure

Indicator Tool Gp" for the instructions that are

The muffler and converter will become extrem-

needed to use the 198-4240 Pressure Indicator

ly hot during engine operation. A hot muffler

Tool Gp.

and converter can cause serious burns. Allow

adaquate cooling time before working on or near

the muffler and converter.

Hot engine components can cause injury from

Excessive idling can cause the catalytic

burns. Before performing maintenance on the

converter/muffler to plug. A plugged catalytic

engine, allow the engine and the components to

converter/muffler will lead to an increase in

cool.

exhaust back pressure. Operating the engine in

extremely cold conditions may cause the catalytic

converter/muffler to plug. One indication of a

plugged catalytic converter/muffler is poor engine

response.

Making contact with a running engine can cause

burns from hot parts and can cause injury from

If the engine is operated at low idle or at low load

rotating parts.

for 24 or more consecutive hours, the engine should

be run at rated conditions for five to fifteen minutes.

When working on an engine that is running, avoid

Running the engine at rated conditions should clean

contact with hot parts and rotating parts.

out the catalytic converter/muffler.

Exhaust Back Pressure

Back pressure is the difference in the pressure

between the exhaust and the atmospheric air.

Table 7

Required Tools

Part

Part Name

Quantity

Number

1U-5470

Engine Pressure Group

198-4240

Digital Pressure Indicator