The Outdoor Power Equipment Institute

1
Product and engine integrated
The engine constitutes the major part of a
handheld product. Thus, significant changes in
emissions legislation will in most cases result
in development of an entirely new product.
2
1990 - 42cc Catalyst Equipped Chainsaw (Europe)

• Catalyst equipped chainsaw
• Developed for Nordic winter conditions
• Sold in Europe only
• High HC conversion
• High exhaust temperature
• Does not meet USFS heat requirements
• Heavy - adds 0.65 lb
• High cost - 30 cost increase
• Problems
• Heat and muffler temperature very high due to the
  high HC conversion
• Heat/Temperature control very difficult
• Exhaust system surfaces
• Exhaust gas
• Surrounding components
• Safety issues not satisfactory for all climatic
  conditions
• Husqvarna ultimately pulled the product from the
  market

3
Line Trimmer
Spark Screen
Chainsaw
High Conversion Catalyst
4
Catalyst Issues

• Heat generation and gas/surface temperatures
  difficult but important to control
• Due to heat issues, HC conversion rates must be
  reduced with increased displacement and power
• Restricted oxygen content in the exhaust (phase 1
  type engines) means a built-in limitation of the
  HC conversion
• Restricts heat and temperature
• Potentially higher CO levels
• Higher oxygen content in the exhaust (phase 2
  type engines), e.g. due to redesigned scavenging
  systems or secondary air supply
• Higher, more unpredictable HC and CO conversion
• Risk for higher gas and surface temperatures

5
Catalyst issues

• Heat effect on surrounding components
• User contact with hot surfaces
• Exhaust system legislation, such as USFS
• Performance issues associated with heat transfer
  into the engine and carburetor from a higher
  muffler temperature hot soak issues.
• Climatic and usage conditions

6
Catalyst Heat35 cc engine, scav. loss 12, A/F 11
Additional Exhaust Temperature as function of
Catalyst HC conversion
350
300
250
200
Temperature increase F
150
100
50
0
0
5
10
15
20
25
30
35
40
HC Conversion
7
Handheld Product Lessons for Non-Handheld Products

• The much larger non-handheld engines already
  generate greater overall heat and greater heat
  density compared to smaller handheld engines.
• Dramatically larger and hotter catalysts would be
  required to convert the greater mass of HC and
  NOx emitted from larger non-handheld engines.
• Handheld engines, due to their low CO levels, did
  not have the extra heat generation resulting from
  the conversion of CO
• The larger the displacement and higher the
  horsepower, the lower the catalyst conversion
  rate must be to prevent excessive temperature
  issues.

8
Handheld Product Lessons for Non-Handheld Products

• With the difficulties in adapting catalytic
  technology to a fully integrated product such as
  chainsaws or line trimmers, non-integrated
  adaptation will be even more difficult
• Engine and equipment manufacturer typically not
  the same
• In many wheeled applications, heat mitigation
  strategies implemented by integrated handheld
  manufacturers will not be available (ex.,
  redirecting cooling air from around engine into
  exhaust system).
• Engine fitted in a narrow engine compartment
  close to surrounding surfaces and functions

9
Handheld Product Lessons for Non-Handheld Products

• Routine maintenance no longer routine!
• Failure by the operator to perform maintenance as
  instructed in the Owners/Operators Manual can
  overwork the catalyst. Surrounding components
  (i.e., fuel tank, etc.) exposed to excessive
  heat.
• Significantly greater efforts are required in
  design and integration to assure product safety.

10
Handheld Product Lessons for Non-Handheld Products

• With engine displacements from 16cc 120cc,
  handheld products have realized that product must
  be developed with catalyst in mind from the
  beginning of the design process.
• It is not a drop-in technology.