fullmann

so, i've searched and found that the normally aspirated 3.4 v6 seems to like a 2 1/4" exhaust, and the supercharged engines like a 2.5" exhaust.

is there going to be a drawback to putting on a 2.5" exhaust in prep for a supercharger that has yet to be purchased (and may or may not really make an appearance), or will my power and mileage suffer?

I also wanted to find out if there is any problem with ditching the dual cat setup and going with a single high effeciency unit? my truck is a california emmission spec (although not in california??) and I realize that it will probably set a check engine light, but that will be remedied by the urd o2 signal piece.

any other input for a header/cat/exhaust combo would be greatly appreciated, as my cat is on its way out and I figure nows the time to do the whole system, rather than pieces that may or may not work together.

ETA: the rig is a 00 4runner sport, 4X4, 5-speed, 95k miles.

kevin444

Your going to lose some low end tq going to 2.5 piping for the time being. Your going to lose even more tq getting rid of the cat since that truck was tuned for cali emmisions and running 2 cats originally. Let me know how ur cat thing goes. I was planning on test piping the 2nd cat in my 4runner along with the urd o2 simulator.

TRDatVT

I currently am running the the supercharger with NO cats on my california emission truck... runs much better up top and no noticable loss in low end power... needs headers though!

kevin444

Remember you are supercharged

Elkaholic

As for it being tuned to Cali standards couldnt he dump the cats then just retune using more URD goodies?

kevin444

Yup,


cali standards= power robbing

Elkaholic

hmmm then I might need to try this someday, since I was thinkin about buying the tuning supplies anyways

rimpainter.com

Guys, it would be a good idea to chill on the "ditch the cats altogether" talk. Let's get back to the original question(s). 2.5 should be ok for now. I assume you have already done your research on the fuel/timing mods needed to make the 3.4 run properly (and safely) with the SC'r, correct? Because I will tell you one thing, exhaust won't mean squat if that thing is running lean all over the place (which it will if you don't get a fuel/timing kit on there) and the engine blows.

fullmann

unfortunately I do know that I will hafta spend the extra dough for the fuel/timing mods with the s/c. what I was mostly interested in was the potential drawbacks to putting a 's/c ready' 2.5" exhaust on a vehicle without the actual s/c. also wondering if dumping the second cat is gonna hurt or help. I dont need to worry about emissions stuff as where I live is not regulated. more along the line of what the truck will work best with, I also dont want to be 'that guy' and drive a pollution creating machine when I dont have to, especially if the truck runs better with all the emissions stuff intact. Im currently getting a pretty regular 20-21mpg with the ethanol/winter gas, I was getting 22-23 with regular non winter gas.

I guess im really trying to not have to spend $2k+ for a factory cat(s) replacement without any other exhaust stuffs. when I can hit up my local muffler shop and spend $500 for new cat(s) and full system all the way back, and be better equipped for a possible s/c upgrade in the future.

midiwall

Like Christian said, you'll be fine... The power will drop a bit, but it'll come back up nicely when you put the SC on. _DO NOT_ put on headers without an SC. I made that mistake.

What's your timeline from the exhaust to the SC?


Don't pull the 2nd O2 sensor. The ECU needs one in front and one in back.


Ummm... dude, $56 delivered, and they're highflow:

http://search.ebay.com/Carsound-Magn...ytic-Converter

Be sure to buy the right size.

fullmann

what happens with the headers and no SC??

Im not sure what the timeline between exhaust and SC is, just kinda toying with the idea of the charger right now but I dont want to buttonhook myself in the future by having to re-exhaust my truck.

will the ecu still need two cats between its two sensors, or will one of the high flow units off of ebay work good enough? I know the truck came factory with two, but I kinda figured it might be overkill, and toyota covering their a$$ when it comes to EPA guidelines.

midiwall

There's not enough back-pressure, which reduces the scavenging effect (getting the exhaust out of the cylinder), which has the net effect of dropping your power band by about 800rpm. That might may you think "Oh WOW... LOW END TORQUE!" but it doesn't work that way - you end up with a boggy engine because of the exhaust not clearing the cylinder before the next intake stroke.

I made this mistake... I drove like that for almost a year. It _sucked_.


Well, it's not Toyota CYA, it's Toyota having to meet the California _STATE_ emissions guidelines.

If you have two cats, then that truck was originally delivered in (or destined to be delivered in) CA. You need to search around the forum for folks that have gone through this. It's not pretty and it may require replacing the ECU with a non-CA version. There are a couple of threads here from about 9 months ago (I think) where people have documented the experience.

There are O2 simulators out there that have worked for some people, but mostly not. There are people that have made it through this, but there are as many people that are still throwing MIL codes every time they start the truck.

Search on "two cats", "mil cat", "cel cat"... that sort of stuff.