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Aftermarket performance parts

By Jim Kerr

Thursday August 28 9:15 AM EST

Cars built in the 1960's and 70's were easy to "hop up". Big V8's filled the engine bays of many vehicles on the road and the manufacturers offered several special high performance models. Many of the parts used on these high performance models could be easily bolted onto the family grocery getter, and there were no electronics or emission controls to get in the way. Today, performance vehicles are again image leaders, attracting buyers to new car showrooms, but it is much more difficult to just add these high performance parts to the family sedan. Fortunately, for those that can't afford the newest "hotrod" on the market, aftermarket suppliers are ready to fill your needs.

While hard core enthusiasts will battle crowded engine compartments to change camshafts, install higher compression pistons or bolt on high flow cylinder heads, most enthusiasts don't have the time, money or expertise to venture that far into performance modifications. Simpler "bolt on" changes that offer more power and improved economy are the most popular. Exhaust systems have to top the list.

Cat back systems, from the catalytic converter to the tailpipe, are the most common exhaust modification. These systems leave all the factory emission controls such as oxygen sensors and catalytic converters in place so the engine computer still operates correctly.

Factory exhaust systems are built with two things in mind: ease of assembly and keeping the cost low. They use exhaust pipes that are "necked" down in the area of the bend. This restricts exhaust gas flow and hinders performance. Aftermarket performance Cat Back systems typically use mandrel bends. Special pipe benders produce full diameter (mandrel) bends with no necking or wrinkles in the pipe. Add in a high flow rate muffler and you have more performance.

Performance exhaust doesn't have to be loud. When housing development started encroaching on the local stock car track, the racers were forced to use mufflers to keep noise levels down. There was a lot of complaining at first, but then the racers noticed that they were going faster with mufflers than they did before! Using the correct parts such as large volume mufflers and mandrel bent pipes are keys to performance - not having a loud exhaust!

With the exhaust system flowing freely, its time for improving intake airflow. Factory air intake systems are designed to keep noise levels down, heat intake air during cold weather and separate rain and snow from the intake airstream. They work well but are a compromise for performance. The simplest modification is to add a high flow air filter. K & N air filters have to be the best known brand of performance air filter on the market and increase airflow while still providing effective filtering.

Other modifications may include ducting cold air into the intake system. Approximately every 5 degrees C drop in intake air temperature will increase power about 1 percent. Intercoolers are used on some turbo and supercharged engines to lower intake air temperatures but ducting outside air to the intake will have similar benefits on non-turbocharged engines. Under hood temperatures may be in the 70 to 80 degree C range in tight engine compartments so even on a hot 35 degree day using outside air will provide substantial performance gains.

Unfortunately, if the ducting doesn't separate water out well, driving in heavy rain could be a problem. So could cold weather, where too much cold air can cause stumbles, hesitations and throttle icing. Be prepared to change back to the original air intake system in winter or drive only on nice days!

"Super chips", electronic devices that alter the engine computer's programming are another popular aftermarket performance part. These chips enrichen fuel delivery and advance ignition timing for increased performance, but at the expense of fuel economy and emissions. Premium gasoline may also be required for engines modified this way.

On the dyno, my experience shows that these chips often do not increase an engine's maximum horsepower but the crispness of acceleration is improved. Of course, these chips will void new car engine warranties and may prevent a vehicle from passing emissions certification, so they are not for everyone.

Obtaining performance isn't difficult. It just costs money and with enough money, even the most basic car can be transformed into a high performance model. The big question is "how fast do you want to go"?

Jim Kerr is a master automotive mechanic and teaches automotive technology. He has been writing automotive articles for fifteen years for newspapers and magazines in Canada and the United States, and is a member of the Automotive Journalist's Association of Canada (AJAC).

This article belongs to its respective owners, and we(mazda626.net) are not attempting to take credit for it in any way, shape, or form. The following is a link to the archive article: http://web.archive.org/web/20050408031830/http://ca.autos.yahoo.com/030828/11/ugs0.html

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