Exhaust size and components for 1UZFE in 4Runner/Surf

[cebby]

I've got an engine on the way to me and I've been reading up on sizing and cats etc. To maintain optimal torque, what is the best size/pipe config for a 1UZFE. Keep in mind, this is for an off-road rig (still will be a daily driver though).

My current 3.0 V6 has a single 2.25 or 2.5 dia single cat setup (Borla catback in place currently)

A single outlet is desired due to space, but I will make whatever is best work/fit.

 

[JBrady]

Small pipe will help torque. You can keep your Borla. Make certain to join both sides of the engine with a GOOD 2-into-1 merge pipe. Your question on what is THE best size is not one that can be easily answered as the 1UZFE ranges from 230hp-300hp stock and 240tq-310tq. My 300hp 1UZFE engine has dual 50mm (1.97") pipes that join to a single 60mm (2.36") center pipe that is squeezed even futher down to a single 50mm center resonator. Your single 2.25-2.50" Borla will work fine on an early 1UZFE for strong low to mid RPM torque.

 

[cebby]

That sounds great! I should have clarified - engine will be a pre-94 model with an auto trans.

Do I need to run (2) cats? I saw the LS400 had two, but mine came with only one. My rig gets an emissions check, so it needs to pass. Is the number of cats dependent on the displacement or what was OE from the factory?

 

[thefastj]

as long as all the exhaust gas runs through a cat it is fine.
so either have a cat for each bank, or have a single cat just after the pipes merge into one.

dont go any smaller than single 2.25" whateva you do.
that is the minimum you'd want it for a single system.
i'm actually doing a twin 2.25" on mine.

 

[JBrady]

That sounds great! I should have clarified - engine will be a pre-94 model with an auto trans.

Do I need to run (2) cats? I saw the LS400 had two, but mine came with only one. My rig gets an emissions check, so it needs to pass. Is the number of cats dependent on the displacement or what was OE from the factory?

Well, in terms of passing emissions tests you may want to research the state laws. You will probably find that you must run an engine that was both originally emissions legal and no older than the recieving vehicle. In your case the 94 auto engine in a 93 truck will probably qualify. From there they usually require that ALL emissions equipment that was with the original vehicle must be installed and functioning. In the case of catalysts their are additional rules. I think you are ok in replacing the factory cats but if you have them go ahead and run them. The stock engine used 2 catalysts (if it was California certified it had 3) so you definitely want to run one on each bank. On the manifold outlet was the factory location and that is probably the required placement.

All the above said, it comes down to your area and how strictly the inspection station is. You may find that as long as the engine LOOKS emissions legal and passes any gas analyzer test that you are fine. You may want to confer with others that have done this swap and passed.