Quote:
Originally Posted by brucepick
OK, I'll try to keep the background writing brief.
I asked my mechanic friend if he'd install a smaller muffler in a different location, to enable me to do a better job covering the underside for aero improvement. The OEM muffler sits behind/above the rear bumper and I'd like to relocate a smaller muffler over on the side instead.
He says that the only muffler one could find that would fit would be a "performance" fart can. And that the reduced backpressure would fool the fuel management system into messing up the mixture which would defeat my purpose.
My '89 Volvo uses a Bosch Air Mass Meter between the airbox and throttle body, and an oxy sensor located in the cat converter.
He's basing his judgment partially on his own experience in his '85 Volvo that's turbo'd and has significant performance mods on top of that. When he opened up the exhaust system he had to remap his fuel management system. Both of us have 2.3 liter engines, his is turbo and has a mechanical air flow meter vs. my amm. My exhaust is 2" piping + cat + resonator + muffler. His is 3" piping plus cat + 3" exhaust pipe. No muffler.
What do you guys say? Should I go ahead and ask him to do it anyway? Or hunt for a restrictive fart can or add restriction to typical one?
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If changing the muffler is going to open a bigger can of worms,I had a thought you might consider.Adding a undertray/bellypan only works if it is continuous to the front of the car,or the carmaker has already done such a good job at the vehicle's front,that it can provide attached flow to any additional underbody structure you might add.If you can get the belly of the Volvo clean,up to within striking range of the muffler,you probably won't miss the difference at the gas pump for not having the last and final section.The flow WILL separate a little early,but it will basically have all the useable kinetic energy of a fully paneled car.A fairing could also be attached to the muffler itself.I had to do this on the CRX.Subaru did alot of research with this sort of thing in the Eighties on their XT sports car,and found that bits and pieces of paneling perform close to that of a perfect pan as long as flow is clean in the forebody.You've got to respect heat buildup,however heat-blocking wraps,as used on racing headers,could get you around that one.It would be a real service to mankind,if all mufflers were rated for pressure differential at a uniform flow rate.There'd be no need for guessing about swaps.Perhaps SEMA will wake up one day,and get their members to provide potential customers with useful flowbench criteria for which to select aftermarket equipment.