Upgrading The Exhaust

[ Manifolds | Exhaust Pipes | Catalytic Converters | Mufflers ]

Description

This page describes the available options for upgrading the exhaust system on 2.2L and 2.5L engines. You should read the Turbocharger Concepts page if you are not familiar with Chrysler's various turbo configurations.

Exhaust Manifolds

There are no readily available exhaust manifold upgrades other than porting the existing manifold. Although the blow-through intake setup exhaust manifold differs from the pull-through manifold, there is no performance advantage for either. The difference is in how the turbo mounts so that it can clear the different intake manifolds. As always, port matching the manifold to the head and turbo is always a plus. Generally, the Turbo II manifold runners are smaller than the ports on the head, so port matching can help significantly. Porting is also helpful if you are going to install a larger turbocharger. This will help reduce turbo lag.

There are headers available for these engines, but they do not seem to show a performance gain large enough to justify them on turbo charged engines. In order to fit them, they are constructed of fairly thin material and don't last very long.

If you are going to a large exhaust system, then you might consider upgrading the flex joint to better match the new exhaust pipe size. A 2 1/2" down pipe is usually sufficient, even if the rest of the exhaust system is 3". Such fabrication is usually complicated and expensive. If you are upgrading the turbo, then chances are it will accommodate a 2 1/2" downpipe with no trouble.

Exhaust Piping

The rule here is simple: the bigger, the better. There is no need to maintain back pressure on these engines, even though they are turbocharged. This statement is based on the years of experience of hundreds of people. As a rule of thumb, 3" piping is ideal for racing (greater than 300 hp), while 2 1/2" piping is sufficient for most other applications (less than 300 hp). Even with a 3" exhaust, a 2.5" down pipe is usually sufficient. The exhaust gasses are still quite hot and are moving quickly at this point. You can wrap the down pipe with header wrap to aid this effect, if you wish. If your catalytic converter is located very close to the turbo, then you can do the size change there. Most Turbo II engines came with a 2 1/2" down pipe, while most early Turbo I engines had a 2 1/4" down pipe. It depends on the turbo size and model year. To find out what you have, measure it. :)

A less expensive alternative is to install a cat-back system. Here a larger diameter pipe, equivalent to or greater than your downpipe, is installed right on the stock catalytic converter. Keep in mind that the stock catalytic converter is quite restrictive, so a high flow replacement would be a good idea.

Catalytic Converter Options

DISCLAIMER: I am in no way responsible for your decisions on this matter. I am providing this information with the understanding that it is for off-road use only. Tampering with the emissions systems on street-driven vehicles in against the law.

There are quite a few options available for catalytic converters (or "cats"). If your state does not inspect and look for a cat, then you can probably make due without one. These engines, when properly tuned, can usually pass emissions without a cat. The stock cat has a lot of restriction, so it is best to get rid of it. A way to make the inspectors happy is to cut the cat open and gut the catalyst out. If your engine can pass without the catalyst, then you might consider this. Probably the best option for most is a high-flow cat. These are available for anywhere between $50 and $100 and are street legal.

To increase performance at the track, cut the exhaust pipe about six inches on both side of the cat and either have flanges welded on with stainless steel bolts, or use stainless steel sleeve clamps to mount it back up. Another way is to install a dump valve near the down pipe. These can be the cable-operated type, or the bolt-on cover type. This way, you can remove the restriction of the system while at the track.

Mufflers

There are a few options in terms of mufflers. The easiest is no muffler at all. The turbocharger actually acts as a fairly good muffler and a 2 1/2" exhaust system with a high flow cat is fairly quiet with no muffler.

The next option is a straight-through muffler design, such as the Dynomax Race Magnum or Borla Sportsman. These offer zero restriction because the gasses pass straight through. They work by absorbing some of the pressure waves in the exhaust stream into a fiberglass pad that surrounds it. They aren't all that effective on turbo engines because a lot of the energy in the waves is already absorbed by the turbocharger, but they will take the edge off of a noisy exhaust.

Another option is a high-flow baffled muffler such as the Flowmaster. There is a small amount of restriction because the gasses have to pass through a series of baffles that are designed to reflect the pressure waves so that they cancel each other out. These mufflers are more effective than the straight-though type, and are a better choice for street performance. They don't work the same way as conventional mufflers, which use diffusers and chambers to stop the pressure waves, so they don't create nearly as much back pressure.

Probably the best choice for street performance is a high-flow version of a conventional chambered or "path" muffler. They do have more restriction than any of the above, but still flow much better than the stock unit. The most popular muffler of this type is the Dynomax Super Turbo. These have two chambers with three tubes, but the tubes are perforated to further reduce restriction. There are also many other brands that make similar mufflers, but beware of some of the cheaper units. Some to not maintain the inlet and outlet tube diameters inside the muffler (usually 3" mufflers, which only get 2.5" internal tubes). Others, while aluminized on the outside, are just raw steel on the inside. The internal tubes and baffled rust out quickly and the muffler "blows out". Dynomax Super Turbo mufflers have arc-welded internal parts and are fully aluminized and padded with fiberglass. Since the Dynomax Super Turbo is one of the most popular mufflers used, here are the Dynomax part numbers that fit well on these Chrysler FWD vehicles.

17741: for 2.25" exhaust pipe, round, 6" diameter, 14" long, 2.25" legs, with OEM hanger mount

17708: for 2" exhaust pipe, round, 7" diameter, 18" long, 3" legs
17709: for 2.25" exhaust pipe, round, 7" diameter, 18" long, 3" legs
17710: for 2.5" exhaust pipe, round, 7" diameter, 18" long, 3" legs
17698: for 3" exhaust pipe, round, 8.375" diameter, 18" long, 3" legs

Avoid diffuser disc type mufflers such as the Supertrapp. They basically work the same way as conventional mufflers: by diffusing the exhaust at a steady rate to contain the pressure waves. In order to do this, they have to produce some back pressure. The more discs you add, the more the muffler flows, but the louder it gets. Creating back pressure at the muffler defeats the whole purpose of having the larger exhaust system.

You can always add an exhaust cutout to your system for use at the track. One way is to cut a section of pipe out near the down pipe and either have flanges welded on with stainless steel bolts, or use stainless steel sleeve clamps. Another way is to cut out a hole in the pipe near the down pipe and cover it with a sleeve clamp when not at the track. Another way is to install a dump valve near the down pipe. These can be the cable-operated type, or the bolt-on cover type.

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This page is maintained by Russell W. Knize and was last updated 06/11/99. Comments? Questions? Email minimopar@myrealbox.com.