Hi all. I'm going to replace my exhaust and planning on going to 2" with a high flow muffler such as flowmaster. Does anyone know if I omit the cat in that scenario if that will be too much of a drop in back pressure? If I omit the cat should I stay with stock 1 3/4"? I'm looking to increase top end for highway speed and fuel economy but don't want too much of a sacrifice at bottom end either. (84 22r carbed pu)

I'd actually say leave the cat on there. There really isn't much of a back pressure difference on or off.
I don't know the numbers off the top of my head, but start with about 1/4" larger than stock for the cat, and go to the muffler.
Have the muffler be 1/4" larger than that, and go another 1/4" larger the rest of the way out.
If you keep your stock manifold and down pipes, you shouldn't loose anything on the low end, and it will flow better for your upper end.
Just about what I did for mine, been happy with it.

Todd

Leave the cat. I did 2.25" after the cat with a magnaflow muffler and it ran pretty good for an otherwise stock 22re.

I just upgraded my 22RE exhaust with 2-1/4" pipes, mandrel bends, cat and muffler. I went with 2-1/4" from just in front of the cat all the way back. Only my primary (head) pipe is 2". It runs noticeably better than it did with the 1-3/4" NAPA muffler and tailpipe and the sound is only slightly louder.

>>>*This is one I saw tested many times, even to a series of dyno tests on an older carbed 22R. The same results were seen on the EFI versions.

The factory manifold is excellent and holds the correct back pressure at the port exit to control crossflow at the valves. The stock exhaust pipe is a bit too small, a sacrifice the factory made for noise.

We found a 2" primary pipe size all the way to the muffler entrance, then 2 1/4" on exit all the way back is the best all around. Smaller restricts and some power/economy is lost. Larger frees her up a bit too much and tends to soften the lower end response. It's easy to do since a lot of mufflers are available this way right out of the box, directional flow gains are well known in the industry.

The small increase in pipe size at the muffler encourages directional flow since any restrictions or reversions in the pipe itself are always a detriment.

The drawback is the engine will make more sound, that depends of course on the muffler design, also.....*EB

so a muffler with 2 1/4 connections and adapt the 2" into it or a muffler with 2' in and out and then adapt to 2 1/4 pipe after muffler outlet? or makes no diff?

Ted, do you recall if this setup was using crush bends or mandrel bends?

Ted, do you recall if this setup was using crush bends or mandrel bends?
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>>>*We used crushed bends, the mandel will help if the shop has the equipment to do it....*EB

I've done this twice with the 22RE, and a third time will commence shortly. On my motorhome, it allowed me to take mountain passes in second gear when before it took third. Thrilled with exhaust swap results.

Stock downpipe to 2" Magnaflow 94104 cat. Flange from old cat removed with reciprocating saw and welded to front of new cat to enable use of stock bracket and donut gasket.

Rear cat secured to 2" stainless mid pipe with TorcTite stainless lap clamps from Verocious Motorsports ebay store. Mid pipe came from JC Whitney in 6' length. FexEx lost the first one when I was in a wrenching panic before a road trip, and they promptly sent me another one overnight at no charge. Yowza! About a month later, the lost one landed on my porch. Double yowza!

Mid pipe to 2.25" Raptor 50051FLT muffler using another TorcTite 2" clamp and a 2" to 2.25" adapter welded to muffler intake. Exit muffler to 2.25" stainless flex hose from JC Whitney, used another TorcTite clamp. Cat and muff astonishingly cheap from ebay seller.

Made exhaust tip out short piece of 2.25 from AutoBone. Assortment of hangers from AutoBone, OReilly, and Pep Boys. Each had distinctly different types of hangers. 4Runner had lots of empty threaded stuff underneath to enable creative hanging.

Especially on the motorhome, I've beat this setup to death for years on testicle-shattering washboard roads and logging trails that some normal people would hesitate to tackle with a 4x4 ("Are you REALLY gonna drive up there??"). Held together like a champ so far, and I can take the whole banana apart in two shakes with a ratchet and 2 sockets. Total cost was a couple hundred bucks and change.

Sounded so good that I decided it was a must to replace that fruity-sounding horn on such an outwardly macho ride.

Muffler and cat ebay seller Linky
I offered about $7 less than his BIN price and they took it and delivered very fast.

High falootin' exhaust clamps Linky

Flex tubing for muffler out to tailpipe Linky

Good luck with your project.