Improving Gas Mileage

Significant fuel economy improvements can be had by performing simple maintenance on a regular basis.

  • O2 Sensor: Replacing a worn O2 sensor can improve mileage by as much as 40%
  • Ignition Components: A well-tuned engine can improve mileage by 4%
  • Air Filter: A clean air filter can improve mileage by 10%
  • Motor Oil: Using the correct grade oil can improve your mileage by 2%
  • Tires: Properly inflated tires can improve mileage by 3.3%

This could add up to more than a 50% increase in gas Mileage!  This is the easy stuff, folks, and puts money in your pocket!

information from

Oxides of Nitrogen (NOx)

NOx testing has become a major part of vehicle emissions testing. Even if you don’t live in an emissions program area, you still need to know what NOx is, what causes it, and how to reduce it.

NOx (oxides of nitrogen) is a product of nitrogen and oxygen combin­ing at high, sustained temperatures (2,500°F or more) inside the engine’s combustion chambers. NOx becomes a problem when it mixes with hy­drocarbons (unburned fuel) in the lower atmosphere and forms that brown haze that those who live in metropolitan areas know as smog.

Many factors are involved in NOx production. High sustained combustion temperatures are just one. Here are some others:

  • Engine Ping-Plain and simple, if the engine detonates (pings), it’s producing excessive NOx. As a general rule, if you correct the deto­nation, you fix the NOx problem.
  • Over-advanced Ignition Timing – This causes detonation, so it’s a re­lated cause of excessive NOx. Over-advanced timing creates an early buildup of combustion chamber pressure because the spark plugs fire too soon in the compression stroke. The still-increasing pressure ignites a secondary flame front inside the chamber that collides with the flame front of normal combustion. The collision of these flame fronts is the “ping.”
  • Lean Mixture – A lean air/fuel mixture causes a higher-than-normal temperature in the intake mixture, causing the pre-ignition that pro­duces high NOx. Any condition that makes the engine run lean may increase NOx.
  • Rich Mixture – A richer-than-normal mixture won’t increase NOx, be­cause the excess fuel in the combustion process actually “cools” the combustion chamber. This high CO (carbon monoxide) level that is created will mask excessive NOx. As a result, a rich mixture condition should always be corrected before checking or addressing the NOx level.
  • Carbon Deposits – If hot carbon deposits ignite the mixture before normal combustion begins, the resulting flame front collides with the flame front of normal combustion. The noise of this collision is pre-ignition, and as we’ve said before, pre-ignition cause~ excessive NOx.
  • Low-Octane Fuel – Low octane fuel is more likely to detonate than high-octane fuel. If you use a fuel with a lower octane level than is recommended for the engine. This can cause the detonation that produces NOx.
  • Fuel Injectors – The altered spray patterns of dirty fuel injectors can create hot spots in combustion chambers that increase NOx. A dirty injector causes more NOx because it increases the combustion cham­ber temperature. Dirty injectors also reduce the NOx-lowering capa­bility of the catalytic converter because they increase the amount of oxygen in the exhaust

A vehicle’s emission control system reduces NOx in two ways: during pre-combustion with EGR, and during post-combustion with the TWC. By injecting a small amount of exhaust gas into the intake stream, EGR reduces NOx by lowering the temperature of com­bustion. The TWC then uses a reduction method to lower NOx even more. (The TWC also lowers HC [hydrocarbons] and” CO levels through oxida­tion.) When the exhaust gas leaves the tailpipe, most of it has been con­verted to water vapor and carbon dioxide. On a healthy engine under load, the NOx level out of the tailpipe should be 200 to 600 PPM (parts per million).

Refer to TSB# HSN 0699-05 for more information.

Source: American Honda Motor Company

ASE Blue Seal Tech News ~ Volume 7. Summer 2001

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