Page 9 - Donaldson - Exhaust product guide for medium and heavy-duty vehicles and equipment
P. 9
Engine Exhaust Flow Rate
& Airflow Calculations
Engine Exhaust Flow Rate Calculation
The calculations on the Exhaust flow rate may be calculated using the following formula. OVERVIEW
right are provided as a
reference and may be ( Exhaust Temp. (°F) + 460 ) x Intake Airflow
helpful as you validate and (CFM) = Exhaust Flow
select Donaldson mufflers 540
and components.
Exhaust temperature and intake airflow rate must be determined
For the most accurate to calculate the exhaust flow rate. Exhaust temperature and
engine airflow and exhaust manufacturers maximum backpressure may be approximated using
flow rates, Donaldson the table below.
recommends using the
information supplied by Engine Maximum
your engine manufacturer. Engine Type Temperature Backpressure
Diesel 2-Cycle Naturally Aspirated = 900º F 4" Hg
Diesel 2-Cycle Turbo = 750º F 3" Hg
Looking Diesel 4-Cycle Naturally Aspirated = 1000º F 3" Hg
for Diesel 4-Cycle Turbo = 900º F 3" Hg
Engine Gasoline (all types) = 1200º F >4" Hg
Exhaust
Flow Note: If you are spec’ing a dual muffler system, remember to divide engine’s exhaust
flow (CFM) by two
Guide?
See
Exhaust Engine Airflow Calculation
Flow Reference Section of CFM intake rate is available from the engine manufacturer. If CFM
this catalog, page 173. specifications are not available, use the volumetric efficiency
calculation. A simple calculation for CFM is to multiple the
horsepower of your engine by 2.5.
4-Cycle Engine Airflow Calculation
Airflow guide should only
be used as a reference ( Engine Size (CID) x RPM ) Volumetric Intake Airflow
document. For proper x =
muffler application, look 3456 Efficiency (CFM)
to your engine supplier
for the most accurate and
current information. 2-Cycle Engine Airflow Calculation
( Engine Size (CID) x RPM ) x Volumetric = Intake Airflow
1728 Efficiency (CFM)
Volumetric Engine volumetric efficiency ratings are best obtained from your
engine manufacturer. Engines operating with electronic controls
Efficiency could have volumetric efficiency ratings of more than 2.0. Airflow
on these engines should be verified by the engine manufacturer.
4 Cycle GAS Engine Naturally Aspirated = .70 - .80
2 and 4 Cycle DIESEL Engine Naturally Aspirated = .90
Turbo* = 1.50 - 3.00*
* If VE rating is not available, Donaldson recommends using the
highest value to insure proper airflow.
donaldsonfilters.com Exhaust Product Guide • 7
