Fiero Exhaust Presentation given by David Kopielski

January 2002 Club Meeting

Forty NIFE members gathered on a beautiful 60-degree day in January (this is extremely rare!) for our Club Meeting that took place on the 26th when we discussed the Fiero exhaust system, its inherent problems, and improvement options available.

The Fiero 2.8 liter V6 engine is prone to developing exhaust manifold problems due to cracks, burnt gaskets, and loose or broken bolts. A common symptom for a problem manifold can be a loud engine exhaust sound, similar to a bad muffler. Another symptom can be described as a ticking sound from the engine. This sound can give you the impression the engine itself has an internal problem, such as a noisy valve. In reality, the engine is fine, but the exhaust leak at a manifold causes the engine to "tick".

Tighten all manifold bolts and see if the problem is resolved, as they can become loose over time. Missing or broken bolts must be addressed for a sure seal. Removing the manifolds is the only sure way to inspect for cracks and burnt gaskets. It is possible to weld a cracked manifold back into usable condition, but proper precaution must be taken to assure a good repair. Replace burned out gaskets with proper replacements that are spec'd for the V6 Fiero.

Assembling manifolds to the engine should be done with new mounting bolts, as the stresses over the years on the old ones may introduce premature failure. GM order numbers are 11509843 per bolt, and 373928 per stud which are used in place of a bolt to provide a mount for the cylindrical shaped heat shield located near the A/C compressor. Purchase off-the-shelf nuts and lock washers to mount the heat shield to the studs. During assembly, apply anti-seize compound to the threads of all bolts and studs to prevent a potential "rusted-in" condition later.

It is recommended to tighten the bolts at every oil change, as they often become loose. The bolts most prone to becoming loose are ones closest to the "Y" pipe, which are easily accessed.

Check the NIFE website (www.fierofocus.com) for more details on exhaust manifolds, and also for the exhaust manifold porting process for an increase in HP.

Many Fiero owners are always looking for bolt-on upgrades to increase performance and economy. With the wide range of available exhaust systems, it is hard to tell which is the better way to go. Dave Kopielski has researched the many systems and with the assistance of Engineered Performance in Georgia, has compiled actual data from testing done on a dyno. Dave gave a brief rundown of aftermarket exhaust components using the listing detailed below. On display were a set of Fiero Store Sprint headers, FOCOA headers that were ceramic coated locally, Chris West's Full Flow Headers, (supplied by member Steve Tannis), a Borla cat-back system (supplied by Bob Steiger), and a set of ported/polished Fiero Stock manifolds that were refurbished by Darrel Morse and ceramic coated locally. The varied headers and exhaust systems were discussed and many questions answered. The basic dyno testing data of the individual parts were noted as detailed below. It was found through dyno testing that the full header sets were more suited for the larger (3.1L/3.4L) performance engines rather than the stock 2.8L. The various cat-back systems were reviewed and the popular choice was the Borla system. Many were also very interested in Darrel Morse's ported/polished stock manifolds, especially after Ron Dittmer's detailed description of the problems and repairs involved with the stock manifolds.

Another point made during our meeting was that the catalytic converter is a very restrictive part of the exhaust system and is required by many states for emission control. It has been verified that removing the catalytic converter and replacing it with a straight pipe on a stock 2.8L, will increase horsepower, but you will lose low-end torque. It is better to replace the catalytic converter with a performance version such as a Catco Hi-flow unit. This will increase horsepower, but you will not lose any low-end torque.

Fiero Aftermarket Exhaust Systems In Detail

Various Catalytic converters were tested. All the "Hi-Flow" style units gain about 1% horsepower. Removing the Catalytic Converter results in about a 3% HP gain, but has a loss of torque on engines less than 3.0L.

Thanks to Engineered Performance of Kennesaw, Georgia for data complied and Dyno-testing. All gains are average as a result of 3 test runs.