Originally Posted by hal brodmann
Grape - Oops!, I mean Purple,
I don't want to beat this topic to death, but..........
What would the benefits be for the following scenarios:
Replacing my stock CAT with a Goerlich 608227 in the same size as the stock one.
Replacing my stock CAT with a 3" DP and 3" Goerlich cat and stock exhaust.
Replacing the entire exhause like you have done.
What are the benefits in MPG? In performance?
I appreciate your patience with me on this.
Money is tight, but I don't want to spend the outrageous price for an OEM converter if I can buy an aftermarket cheaper that provides better flow also. Also, what is the life expectancy of the aftermarket converter.
Thanks for all of the info. I greatly appreciate your advice.
Mainly by opening the exhaust you are removing back pressure restrictions and allowing the engine to exhale easier. The true benefit is to allow for future mods that require more air intake, greater boost pressures, and more elaborate PCM tuning. The better an engine can breath in and out, the better performance gains in HP as well as MPG you can achieve.
HP gains are marginal, but you can expect 5 to 15 HP. It'* not really a true gain, your actually removing HP loss by removing the back pressure. But, you can still feel the giddy up and go.
There are lost of other engine, tuning and driving factors that influence MPG, but I did see a slight improvement when I gutted the air box and opened the exhaust.
A converters life expectancy is based on fuel/air ratios (exhaust gas) and the heat that the engine exhaust outputs. If you keep you car tuned and replace O2 sensors when they are defective, you should not expect to have to replace a cat for the life of the vehicle.
The benefit of a hi-flow cat will be lost if the rest of the exhaust system is restricted. My entire exhaust rebuild ran me $690! If you can handle the costs, do the entire exhaust. Additionally a set of headers will help as well. Those are next on my list and will be installed in about two weeks.