[Topgun]

Getting ready to do an engine swap. I have a 2nd Gen Supercharger I am going to transplant from my original engine so I decided to go ahead and bite the bullet and install Thorley Headers while the motor is out. I am used to building vintage muscle cars and am considering running true dual exhaust with dual high flo cats & mufflers on my 99 TR4. Bad idea? Anybody running a SC and Thorley Headers running true dual exhaust? Is so, where did you locate your 02 sensor, in your x-pipe? If not true dual, what did you do for a down pipe ... custom, modifed OEM or is there an aftermarket option?

[Nate_GB]

Originally Posted by Topgun

Getting ready to do an engine swap. I have a 2nd Gen Supercharger I am going to transplant from my original engine so I decided to go ahead and bite the bullet and install Thorley Headers while the motor is out. I am used to building vintage muscle cars and am considering running true dual exhaust with dual high flo cats & mufflers on my 99 TR4. Bad idea? Anybody running a SC and Thorley Headers running true dual exhaust? Is so, where did you locate your 02 sensor, in your x-pipe? If not true dual, what did you do for a down pipe ... custom, modifed OEM or is there an aftermarket option?

Not sure what kind of dual exhaust you're picturing doing, but there really is no room on the driver side to run exhaust because of the gas tank and even if you get past the gas tank, getting around the rear suspension in any location besides the stock exhaust route is pretty much impossible, or at the very least, extremely cost prohibitive...

[gamefreakgc]

I've never seen a dual exhaust on a 4Runner for above reasons. I have the Doug Thorley headers and the supercharger and if you have a 96-98 get ready for a lot of tweaking a fabbing to get it to fit in the engine bay. Transmission kick down cable bracket and the transmission dipstick tube will need to be relocated, possibly others depending on fitment.

99+ are a little bit more bolt on, but even then not perfect. I've never seen an aftermarket downpipe anywhere, majority are cat back so the space between the end of the header collectors to the cat-back would have to be custom made. The front O2 goes in the headers, if you remove or modify the cat you'll need to run a simulator for the rear or it will throw a constant code.

Headers make a difference, the cat-back not so much. Honestly, a true dual exhaust would either entail a lot of work of a lot of money. If you looking to gain more power the 2.1" pulley plus larger injectors + a piggyback or the 7th injector kit will gain way more than any custom exhaust setup ever will. I paid more for the headers and installation than I did for all of the fuel and computer parts combined I have on.

Definitely swap out that stock muffler though.

[Hepar]

Agree with the comments above. I've seen a couple "dual" exhausts and they were really just for show. They were basically single-pipe systems that split at the rear.

[Sb08v8]

I just got my DT long tube headers installed and now I’m getting worse mileage around the city and terrible mileage on the interstate. I’m driving the same was I was before the headers and I was getting an average of 16.7 MPG. Interstate cruising at 65 getting low 12-13. Also getting 12 codes.

[heat]

You got intake and exhaust leaks. Work through your list, or get your
installer to do that, since they probably caused them.

[gamefreakgc]

Exhaust leak bonanza. And maybe some criss-crossed vacuum hoses. Take it back to get it fixed.