73-25 DWP
Evaluation of the Atom Auto Pecos, Ltda.
Variable Venturi Carburetor and the
Fuel Inlet Vaporizer
April 1973
Emission Control Technology Division
Office of Air § Water Programs
Environmental Protection Agency
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Background
Atom Auto Pecos Ltda. of Brazil contacted the Office of Air
and Water Programs and requested an evaluation of a variable
venturi carburetor and a "fuel inlet vaporizer." Data was
presented from Olsen Laboratories compiled using the 1973
FTP on a 1973 Duster (225 CID engine, automatic transmission)
with the variable venturi carburetor and a 1972 Volkswagen
(Beetle) with the "fuel inlet vaporizer." Based on the Olsen
Laboratory results a test program on these devices was under-
taken by the Test and Evaluation Branch. The variable venturi
carburetor was of specific interest.
Device Description
Variable Venturi Carburetor: This type of carburetor supplies
an essentially constant air velocity through the fuel delivery
venturi section of the carburetor.. This is done by varying the
venturi cross-sectional area with engine load. At light load
when engine air consumption is low, this type of carburetor
allows for high venturi air velocity thus achieving higher
turbulence and potentially better fuel atmonization and dis-
tribution than is the case of the standard fixed venturi carb-
uretor. Thus, there is a potential for lean operation with
the variable venturi carburetor.
Fuel Inlet Vaporizer: This device incorporates modifications
to the carburetor jets. The jet or jets are modified in such
a way that an adjustable fuel venturi is used to control a
primary air bleed into the jet. It also provides for some
turbulence in delivery of this p-rimary air/fuel mixture .to the
carburetor venturi.
Test Program
Two tests were run on the 1973 Duster with the variable venturi
carburetor and one on the Volkswagen with the "fuel inlet
vaporizer." All testing was conducted in accordance with the
1975 Federal Emission Test Procedure as described in the
November 15, 1972, Federal Register.
Results
The results from the tests are reported in the attached table.
The Duster variable venturi tests show potential for meeting
1975 interim standards. It should be noted that tests on the
Duster were conducted with the EGR system disconnected. Test
results of the "fuel inlet vaporizer" did not show any. signi-
ficant emission control.
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Conclusions
1. The Atom Auto Pecos Ltda.'s variable venturi carburetor
installed on a 1973 Duster (225 CID engine) showed potential
for meeting the 1975 interim standards.
2. The Atom Auto Pecos, Ltda.'s "fuel inlet vaporizer" did
not show any significant emission control potential.
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Test Results
Atom Auto Pecos Ltda. variable venturi carburetor
Test car: 1973 Duster - 225 CID eng/auto. trans.
Comments: EGR was disconnected during testing, manual
choking was used.
HC CO NOx
1.51 gm/mi 7.03 gm/mi 3.28 gm/mi
1.68 5.79 2.33
1.5 15.0 3.1 '75 Interim
Std.
Atom Auto Pecos Ltda. "fuel inlet vaporizer"
Test car: 1972 Volkswagen Beetle
Comments: Manual choking was used.
HC CO NOx
4.05 gm/mi 53.09 gm/mi 1.54 gm/mi
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