I was talking to a service writer at my local Toyota dealer about replacing my stock single exhaust with custom true dual exhaust (Flowmasters or similar), leaving the catylitic converters on. He told me that on the V8 Tundras, it actually decreases torque/HP.
I really don't understand it (and he couldn't explain it either), but he maintains that he seen dozens of Tundras lose their punch by switching to dual exhaust. He recommended buying the TRD or Borla exhaust upgrade, but they aren't a "true" dual exhaust system (and are about twice as much). Anyone care to weigh in on this?

 

Typical Stealer bullcrap.

 

Not positive, but I think it has to do with "backpressure."

That is the extent of my knowledge...

 

Or, as <96_Runner> said, it could be typical stealer bullcrap!

 

I mean more along the lines of saying something and not backing it up.

Backpressure? Absolutely. You need it. So, you could theoretically screw up your powerband by going too big (dual). I would go with a custom single pipe system from an exhaust shop. That will save you a bundle. What type of sound are you looking for?

 

I don't know much about back pressure, but just a thought. If you want to go dual, couldn't you just decrease the size of the pipes you use to accomodate a dual system, to compensate for the extra pipe?

 

you could also get a dummy pipe like jason

 

I don't know if the same holds true for Toyotas, but true dual exhaust is'nt considered necessary on small block chevys unless you're making at least 300 horsepower.

 

Very few engines actually need dual exhausts; it's usually just for appearance. However I do get the feeling the dealer just wants to sell you a TRD piece so they can make more $$$. Having said that, there might be some truth to what he says; many trucks have deliberately constrictive exhausts because it makes more low end torque.

 

I'm looking for a deep powerful sound (as well as the look of duals). Also, if I'm going to put that air intake back on, I'd feel better with a less restrictive exhaust. And lastly, I'm looking to increase HP.

 

My vote is a custom 2.5" cat-back single into a 50 series flowmaster or 18" magnaflow.

If you just have to have duals, then you may want to go stock size into a single in dual out 2 - 2.25" and have the pipes custom placed (if they will fit).