I hate to jump in late, but I would be afraid of ANYONE who thinks a restrictive exhaust would actually bend valves, etc. Last time I checked, air was compressible. Even a restrictive exhaust cannot generate extreme pressure enough to deform metal. Even completely blocked, the engine would not perform any revolutions once the exhaust pipe is pressurized. An exhaust seal would blow before pressurization great enough to bend valves occurred. What is a "jake brake" someone might ask. This device actually restricts exhaust flow which provides this same backpressure we are discussing, which then retards the revolution of the engine, to decelerate a vehicle. This is the stuttering Da Da Da Da Da Da noise you hear when a dump truck, tractor trailer, etc is slowing down. A restictive exhaust will do nothing more than "bog" your engine, and retard its revolutions. Several GM(
) cars have a problem with crap blocking the ceramic honeycomb in the cat. They merely run like they have a clogged fuel filter. I misdiagnosed one for that reason as the symptoms are identical, plus this particular car had 90,000 miles with never a filter change- go figure. Idles great, bogs down when the accelerator is pushed more than 1/2 throttle, or when the rpms are up. No known bent valves have occured to my or sevral knowledgeable friends.
None of this is a direct relationship to your issue, but when dealing with people with a lack of knowledge in physics- especially your mechanic, "Be afraid, be very afraid" lol. I would probably go somewhere else and deal with someone who seems to know more about these systems. Of course gasses need to flow out of the darn thing, and unless you actually choose to install something MORE restrictive, which is never the case. Why would anyone talk about less restrictive cats to a customer? Are there secret societies driving around with tiny riding lawnmower sized cats meeting in the woods at night?We are always looking for less restrictive cats. Why the heck would anyone go out of their way to put on something MORE restrictive? Hell, even if you did, no mechanical devices in your engine would be damaged at all. You would just lose power, and engine efficiency.
This person should be telling you that of all the options he has produced, if any, how the flow should be the same as stock or greater. The only real hair splitting you should be dealing with is how much catalyzing and earth friendliness your new higher flow converter, giving you more power, still gives the gas escaping your tailpipe. How about just buying a high performance cat, and just having that installed?
When I have to deal with mechanics, I always remember what a buddy of mine told me once. To claim superiority during a certain situation, he stated, "I was a mechanic for eleven years". My reply was, " and I was smart enough to NOT be a mechanic for eleven years". Good luck with whatever happens.
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