UKrunner

Guys just wondering if any of you run a completely separate dual exhaust system or if you join up somewhere?

I have a swapped '91 with a 3.4. I run duals down each side of the transmission and connect the pass side to the drivers side at the bell housing, where it then connects to the stock exhaust.

The exhaust shop really messed this up. They crushed the 2.0 inch dia pipe down to clear the sway bar and they didnt put the flex section in I asked for so when snow hit the hot exhaust is put a nice crack in one of the welds.

I have enough stock bends and lengths and 2 spare nib flowmaster 40 series mufflers to run true duals all the way back. I believe there is little to no scavenging going on in the stock exhaust as the distance is just to great, so I cant see any disadvantage to not joining the two heads together.

What do you think about this?

250000_yota

The two sides of the exhaust have to connect to hit the pre-catalytic converter oxygen sensor, the catalytic converter, and the post-cat oxygen sensor. After that, dual exhaust would be possible, but kind of un-needed in my opinion.

xxxtreme22r

actually the h-pipe between the two is better than a true dual setup. Give more power as it equalizes both exhaust pulses. Resulting in better low to mid RPM power. Not to mention a bettr exhaust tone. Thing of it this way a true dual on a v6 engine is gonna sound like two 3 cyl geo metros sitting next to each other.

But 250000_yota beings up a good point, the exhaust has to join at the cat anyway unless your running two cats one on each side. This is assuming your even running a cat to begin with. By your description sounds like you are not.

mt_goat

The main disadvantage as I see it is the front O2 sensor would only be reading 3 cylinders instead of 6. That may not be a problem as long as both banks are doing exactly the same thing air/fuel ratio wise, but what if for example you have an injector malfunction on one side and the ECU doesn't have a sensor to detect it?

Last I heard Jasond was running true duals on his truck without problem, might ask him if its still working out for him or not.

UKrunner

Yes the O2 sensor would be the only reason to connect the two sides together. I am not running cats at present.

I cant see a H pipe, 4 ft away from the engine really doing much for torque, it would be more of a sound and resonance benefit. H pipes sound more throaty then X pipes.

The only reason I'm considering this is because I cant weld and have a ton of slip fit parts lying around, and that one side of the block must be really struggling to breath vs the other side due to the crush.

I actually like the way it sounds right now, very lopey and off timed pulses due to the longer length pipes on one side of the engine. Kinda like the unequal length headers on Subarus.

I'll see if I can post up some audio of it.

mt_goat

Well I wouldn't say the only reason, just the main reason. There is also a disadvantage to having 2 hot pipes running to the back, one I presume next to the gas tank and possibly fuel and brake lines. Two cats/mufflers or angry neighbors...etc

UKrunner

Plenty of space under there to run a 2"' pipe and keep everything cool.
There would be two mufflers. It might actually be quieter running the duals than just the rear muffler thats on there now. Its quite raspy on the over run.

I also wonder if having 2 pipes exiting at the rear bumper would help with the exhaust smell when the back window is down.

brian24

I currently run a flowmaster with a tundra resonance silencer welded in. This has reduced about 80% of the truck humming in the rear of my 97 4 Runner.