Conversion To Throttle Body Injection (TBI)

TR6 Home

TBI - 1 Year Later

Emissions Test

TBI Home

Removing Old Stuff

O2 & TPS Sensor

By Pass Block Off

Carb Adapters

Injector Installation

Fuel Tank & Lines

Fuel Pump

Fuel Lines


ECM Connections

1st Start Check List

1st Start Results

Driving Impressions

Reliability & Parts

ECM Trouble Codes

Flashing A Chip


Connecticut Emissions Test

Any car 25 years and older is exempt from the Connecticut Emissions Test, but I was curious as to the impact of converting the car to Throttle Body Injection. Does having all these "modern" components make the car cleaner or wouldn't it matter seeing as there's no catalytic converter. So I stopped by one of only two test stations in town to find out. It was quite an interesting experience for both the garage and me. The car gets backed on to rollers and the front wheels chocked. Then the proctologist visits the tail pipe with his magic wand and inserts it. Next up was plugging into a 12V outlet which luckily I have. Finally it was time to enter the car info into the computer. VIN# CF38503U gets entered and ............BURP..... invalid number! No problemo...........just switch over to the manual mode and enter it again. Now a 1975 Triumph TR6...........BURP.........why are you testing a 33 year old exempt car?!? Invalid, invalid. Not allowed. Now what? Ah mode.....and this takes the local PC offline from the big mother State computer in the sky. Try again.....1975 Triumph emissions data available for 1975. now I'm driving a 1984 Triumph TR6 which isn't a valid car but it's good enough for testing training mode. Go figure.....but here's the scenario......we have a 1975 car/engine being tested against 1984 standards.

Sorry about the picture quality but I took it with my cell phone.

OK.....if you've read this far you must really be curious as to how this all turned out....... well, 2 out of 3 ain't bad. I easily passed the HC and NOx tests but failed the CO test. The chart below shows the Upper Limit and my results.

Emissions Tested 1975 Standards - grams/mile 1984 Standards - parts/million 1975 TBI TR6
HC 0.41 GPM 208 PPM 116 PPM
CO 3.4 % 0.67% 1.3%
NOx 0.4 GPM 1458 PPM 790 PPM

So while I failed the CO test as based on 1984 standards, it did pass relative to the 1975 standards. And while I passed the other two based on 1984 standards, one set of standards is in grams/mile while the newer one is in parts/million. Is it possible to convert one to the other? In talking to Rick Patton, I could do another data logging drive and submit the log file for analysis but the car runs great as is, gets good fuel mileage and...........I don't have to be tested in Connecticut!

Some "definitions"

CO too high = Car runs rich, burns too much gas.
Bad carburetor adjustment, float too high, carburetor flooding, sticking secondary throttle, leaking fuel injector, leaking fuel pressure regulator, feedback system malfunction (oxygen sensor, coolant sensor, throttle position sensor), emissions vapor system malfunction (purge valve, canister clogged) Be aware that NOX will RISE after you fix a CO problem. This must be checked after a successful CO repair.

HC too high = unburned fuel in exhaust; car runs very rich or very lean. This is the trickiest condition because there are different causes. If the car is running rich (high CO), the HC can be high also. If the CO is very low and HC is high then the vehicle has a lean misfire.

If The CO is high, fix that problem first. If CO is low and HC is high look for engine skipping, misfire due to vacuum leaks, ignition timing set too advanced, ignition misfire problem (plugs, wires, cap), low fuel pressure, carburetor adjusted too lean. If you canít find a reason for the high HC then perform balance test then compression test to check for engine mechanical problem.

NOX too high = NOX forms in normal combustion. NOX too high indicates high combustion chamber temperatures or malfunctioning post-combustion emission controls.

CO and HC must be normal before attempting to repair NOX failure. Anything that can create high combustion chamber temperatures will make NOX reading high. Engine overheating, air cleaner hot air door stuck closed, egr vale not functioning, clogged egr valve passage, lean fuel mixture, ignition timing set too high. The two main systems that reduce NOX on a car are the egr system and catalytic converter. If your car is pinging, the NOX will be too high. Pinging is a symptom of high combustion chamber temperature. If all the test readings are just a little too high (slightly high CO, HC, and NOX) it is likely the catalytic converter is damaged or empty. If your converter is supposed to have air injection and it is disabled, the converter will not function properly.

The History of Reducing Tailpipe Emissions

1970-1975: The First Standards In 1970, Congress passes the Clean Air Act, which called for the first tailpipe emissions standards. The pollutants controlled are carbon monoxide (CO), volatile organic compounds (VOC), and oxides of nitrogen (NOx). The new standards go into effect in 1975 with a NOx standard for cars and light-duty trucks of 3.1 grams per mile (gpm).

1977-1988: Tightening Standards for the First Time In 1977, Congress amends the Clean Air Act and tightens emission standards again in two steps. First, between 1977 and 1979, the NOx standard becomes 2.0 gpm for cars. Then in 1981, the NOx standard for cars is reduced to 1.0 gpm. Effective in 1979, pursuant to the Clean Air Act requirements, EPA tightens standards for light-duty trucks to 2.3 gpm. Effective in 1988, EPA then sets the first tailpipe standards for heavier trucks at 1.7 gpm and revises the standard for lighter trucks to 1.2 gpm.

1990-1994: Tier 1 In 1990, Congress again amends the Clean Air Act, further tightening emission standards. The NOx standard is set at 0.6 gpm for cars, effective in 1994. The new standard called "Tier 1"is a 40 percent reduction from the 1981 standard. For trucks, the new standard ranges from 0.6 to 1.53 gpm, depending on the weight of the vehicle.

The Clean Air Act Amendments of 1990 also require EPA to assess the air quality need, cost effectiveness, and feasibility of tighter emission standards for the 2004 model year and beyond.

1998: Voluntary Agreement For Cleaner Cars In 1998, the Clinton Administration with the auto industry and the Northeast states strike an innovative, voluntary agreement to put cleaner cars on the road before they could be mandated under the Clean Air Act. The new cars are called National Low Emission Vehicles (NLEV). The first NLEV cars under the agreement reach consumers in New England in 1999 and will reach the rest of the country in 2001. NLEV cars operate with a NOx standard of 0.3 gpm, a 50 percent reduction from Tier 1 standards. The NLEV agreement also calls for a 0.5 gpm NOx standard for lighter trucks only, a 17 percent reduction from Tier 1 requirements for these vehicles.

In 1998, as required by the Clean Air Act Amendments of 1990, EPA issues the Tier 2 Report to Congress. The report contains strong evidence of the need, cost-effectiveness and feasibility for tighter tailpipe emission standards in the future beginning in 2004. Three main factors support EPA's decision:

1) currently vehicles make up 30 percent of smog-forming emissions nationally, and because the number of miles driven is increasing (up 127 percent since 1970) they will continue to be a significant contributor to pollution;

2) larger vehicles like SUVs, that currently do not meet the same standards as cars, pollute 3-5 times as much and make up 50 percent of the vehicles sold today; and

3) the technology to meet tighter standards is available and cost-effective.

In 1998, EPA also determines that sulfur reductions in gasoline are needed to enable the full performance of low emission-control devices.

1999: Tier 2 In 1999, EPA proposes Tier 2 tailpipe emissions standards beginning in 2004the first time both cars and light-duty trucks are subject to the same national pollution control system. The new standard is 0.07 gpm for NOx, a 77-86 percent reduction for cars and a 92-95 percent reduction for trucks beyond the NLEV agreement. EPA also proposes a reduction in average sulfur levels to 30 parts per million (ppm) (maximum of 80 ppm) to achieve the full performance of vehicle emission control technologies.

As part of these new standards, EPA has included several measures to ensure maximum flexibility and cost-effectiveness. These flexibilities include:

  • allowing averaging to meet both the car emission and gasoline sulfur standards;
  • allowing extra time for larger vehicles between 6000 and 8500 pounds and smaller refiners to meet their respective standards; and
  • allowing for a market-based credit trading-and-banking system for both industries to reward those who lead the way in reducing pollution.

Source: History of Reducing Tailpipe Emissions