I am planning on putting a new exhaust system on my truck from the header back. I was wondering what size pipe you guys would recommend 2 1/4, 2 1/2, more or less? I plan on using a 40 series flowmaster muffler, and when I get enough money I am going to bolt up a LC header. I would like to find a good exhaust size that can be used with the stock manifold but still provide good flow with a header. Also i am going to ditch my cat until emissions comes around again, is there any negative effects to running with no cat? This if for a 93 toyota truck with a 22re

2" or 2-1/4" works well. The LC header is 2" output, stock cat is 2" in/out so I kept it to 2" the rest of the way back (Flowmaster 50 series) since I had enough 2" pipe and fittings left over from from other projects:
- http://www.4crawler.com/4Runner.shtml#Engine

Some folks go with 2-1/4" from the cat back.

how loud is your flowmaster??

Not too loud, there is a link to a sound clip on the page I posted earlier. It is just audible above the road noise.

Yeah, the 50 series on 4Crawlers truck actually sounds really nice I listened to the clip online. Made me decide I wanted the 40 series, for a little more of that grunt noise! <img src="/forums/images/graemlins/cheers.gif" alt="" />

Stock manifold to 2" pipe to cat to 2.25" pipe to some cheap napa muffler, no tail pipe. No cat: It's bad for your own environment & the same air you breathe. Just get a new one if yours is all plugged up. A cat isn't that expensive if you can afford a header. <img src="/forums/images/graemlins/kewl.gif" alt="" />

this is what i posted to someone else when they said they were going to run w/o a cat.


i would think the emissions released would be directly proportionate to the amount of fuel burnt. also the gov. does not try to enforce people putting cats on older vehicles b/c they did not come w/ them from the factory. they were not manditory until 1981. putting a cat on a vehicle which was not made for one would require alteration modification of the fuel/air ratio and/or fuel pressure system in order for it to run efficiently. if you are taking the cat off you are going out of your way to pollute the enivronment and could be making your vehicle run worse. the engine management system is precisely calibrated to deliver optimum gains and efficiency w/ the some amount of back pressure. so taking the cat off is directly affecting all the calibrations and settings from the factory which makes your vehicle run less efficiently and could dampen performance.

It's not the size that matters. It's how you use it.


<img src="/forums/images/graemlins/ignore.gif" alt="" />

When discussing gasses and emissions, SIZE does matter. A little squeeker from betwixt the cheeks might get the cats attention, while a full blown cheek burner coulda sworn I ate chili earlier exhuast emission is guarenteed to get the wife outta bed.

~Darin <img src="/forums/images/graemlins/baby.gif" alt="" />

PS- For 22R-E exhuast systems, I like to run 2" from thte downpipe straight into a 2-1/4" in/out Flowtech Raptor and finish off with a 2-1/4" tail pipe....exiting stock location on my 88' 4x4 and routed to the back on my 4Runner.

Thanks for the responses, sounds like i am going to have to run some 2 1/4 from the cat back.