Tech Article: Z Exhaust System Upgrades
by Ben Pila Jr.
This article is aimed at the 1989 and older Zs as the 1990 and up Zs have a more complex exhaust system that is already well designed. What does the exhaust system do? It essentially controls the exhaust gasses that leave the engine by directing them usually toward the rear of the car. So why upgrade your stock exhaust system? The benefits of an upgraded exhaust system can net an increase in horsepower which you might feel and a produce a more sporty sound.
Now about headers and exhaust manifolds. Most headers are a tubular style with calculated tubing size (called primaries,) and have equal length runners that meet into a collector at another calculated length. The purpose of headers are to allow the exhaust gasses to exit each cylinder faster and more efficiently than the original cast iron manifold does. The stock manifolds usually have uneven length passages and smaller sizing. In many cases headers aren't smog legal in California. Check the current laws on this issue. Headers do improve the flow but the drawbacks are more exhaust noise and increased under hood temperatures. Headers come in a variety of styles. There is the 6 into 1 style and the 6 into 3 down to 2 collectors. Which style depends on what your needs are and the power band as each effects it differently. If your Z is to remain mostly stock, then I'd recommend not installing a header(s.)
On what size of exhaust pipe to use? Most inline Zs like to have a 2.2" system whereas the early V6 Zs like 2.4". One thing on sizing is that too large of a tubing size may cause less power at mid and low range rpm driving due to the exhaust gasses slowing down too much as they exit the manifold or header. Mandrel bends? Mandrel bending uses a special exhaust bending machine that doesn't put a crease at the bends like regular exhaust benders do. The result is a clean, smooth bend that doesn't change the size of the exhaust pipe. Mandrel bending is nice but some might not feel the difference between it and the regular bending so it is a matter of preference. I prefer the mandrel bending. Mandrel bent exhaust usually cost more to fabricate at the muffler shop. Many systems available through mail order companies are mandrel bent. Exhaust tubing comes in a few types of materials. The most common now is the aluminized tubing which is very resistant to rust and low in cost. The mild steel tubing does rust so stay away from it if you want your system to last longer. The stainless tubing is nice but in California is isn't needed and is very costly.
Mufflers come in many varieties and serve different needs. It is known that the stock mufflers on the early Zs are quite restrictive. Some of the most common muffler styles are the Turbo mufflers, glass packs, Monza, Super trapp and flow through styles. The best all around mufflers have been the turbo styles. Turbo style mufflers allow less back pressure and have a nice sound. Glass packs are usually loud and many don't flow as well as turbo style mufflers. Monza style mufflers (actually tips) are usually two small glass packs designed to look like the tips some Ferrari cars use. The Monza style tips are more for looks than flow. Super trapp mufflers are a unique design in that it is a glass pack style with a difuser cap on the end that has multiple plates on the end which can be removed or added for a change in power and noise.
I recommend these only for the racers. The flow through style mufflers do flow well but their straight through design means lots of noise. Many of the modified Honda subcompacts making noise use these style of mufflers.
Many Zs use a resonator in the original exhaust system. I'd recommend removal of it if your exhaust system is being upgraded. The resonators are usually the same size in its core and any increase in pipe size will be useless with resonator left in. If you prefer a more quiet but larger exhaust, have a 2.2" glass pack put where the resonator used to be. The resonators purpose is to cut out the higher exhaust's frequencys that Zs make at certain rpms. A glass pack in place of the resonator probably won't hurt the flow enough for you to feel. Again installing a resonator is a preference. It can always be added later if needed.
Catalytic converters are the large muffler like devices that lower the emissions to meet smog requirements. They are required by law to remain on the car. One thing though that can be done it to upgrade it to install a high flow style which along with the larger exhaust behind it will help improve exhaust flow. If you choose to leave the existing converter in place, the piping ahead of the cat (called a head pipe,) remains in place since changing it won't improve flow with the stock converter. The "cat-back" system installation is quite common at muffler shops.
So where do you go to get the upgraded exhaust system? There are the mail order companies like Motorsport Auto, Tweeks and Victoria British (they do have a Z catalog,) only thing is the exhaust system still needs to be installed. There are the local exhaust shops. I have always liked Ed Hanson's Muffler in Spring Valley and can say they do excellent work. There are many quality muffler shops in San Diego county. Maybe talk to other members who have already had their exhaust systems upgraded for their thoughts and recommendations. I hope your search for an upgraded exhaust isn't an exhaustive one. Pun intended!