While the car was on jack stands I took a look around the underside.

Key points for XD exhaust.

- Stock header is decent, cat is NOT apart of the header!

- Car has two cats and a resonator

- Car has only ONE O2 sensor!!!!

- O2 sensor is just after the first cat!!

Here is the part to pay attention to....
The xD has a NICE sized exhaust pipe all the way to the resonator! Stock pipe to the resonator is 2.4" OD!!!

Now at the end of the resonator, the pipe reduces a HUGE amount. It dropes down to 1.7"OD WTF hahaha.

The good thing is you can add on an exhaust just before the resonator / add a new resonator that is equal diameter input and output wise. This means you can have a 2 1/4" exhaust all the way back and NOT get a cell as there is NO secondary O2 sensor after the first cat!!! Hope that sinks in and is understandable.

Lots of room to improve flow!

XD stock header


XD Box muffler


XD Muffler input and output.

 

hmm... looks like my TRD exhaust will be going up for sale and a custom 2 1/4" job will be going in after that o2 sensor! im sure that 1.7" taper doesnt help at all, especially for a motors that i imagine can open up pretty good with the vvti

 

My motor feels choked down past 4K rpm stock... I imagine ID on the pipes would be a 2.25 - 1.5" which is a major difference.

 

from what you described... is the below exhaust schematic that i spent at least a few hours on drawing up pretty accurate? i have not looked under the car myself much.



and on second thought, maybe keeping the TRD exhaust would be perfect. i would just need a shop to chop the pipe right upstream of the resonator (get rid of it completely), and run it 2 1/4" all the way back to the TRD axle back, which is 2 or 2 and 1/4" isnt it?

nice discovery though... ive been too busy/lazy to take the time to get the car on jacks and look at all the monkey business under there.

my other question was, where are the flanges at? are the cats welded in, or flanged in?

 

Bingo VERY strange there was not a 2nd O2 sensor on the car but it is what it is!

The 2nd cat and resonator are SUPER close together when you take a look.

All the cats & resonator are welded together

 

hmm... off-road pipe could be a little more difficult then for that second cat. im not much of a welder.

i think ill take the car over to the exhaust shop and get a quote for replacing that 1.7" pipe. i had the dealer throw my stock muffler in the trunk after i bought the car, and the piping on it did look awfully small now that i think about it. surprisingly small.

it is strange that there is only one o2 sensor. most new cars have two, and compare the readings between the two to check the functionality of the cat. well, that makes it that much easier to prevent a CEL with any future exhaust work in that neck of the woods!

 

only one o2 sensor...so does that mean it doesn't check the engines a/f ratios and make corrections like the tc does, which means that you have to retune as it relearns and changes the tune?

how does it even check if the cat's are working with only one sensor? what other systems have cars used to detect the functionality of cats?

 

Going to double check again tommorow and see if there is one hidden on top of the header, only other place I can think of, otherwise there is only 1 and it is just after the first cat Definitly nothing after that!

 

Not bad for a stock header. i'd probably still want to upgrade to a 2.5 later on along with the exhaust though.

 

im gonna take the xD into mineke in the next few days and get a quote and possibly get that 2 1/4 pipe installed from behind the second cat all the way to the TRD axleback. of any of the exhaust mods out there right now, that will probably be the one to get the best, if any, gains - a full 2 1/4"+ catback. im sure that 1.7" pipe bogs like a **** once you pass 4k rpms.

 

The ID on that pipe is about 1.5" hahaha.

 

just got back from the exhaust shop...

i did end up running the 2.25" from directly behind the second cat to the TRD exhaust. ive got some key points here though.

first off, if you have not looked under your car yet, the stock exhaust piping is small enough to make you puke. its even squished in a few sections even smaller than the 1.5" for only reasons god knows. were talking piping about the size of what might come on an 18hp briggs.

secondly, there are two O2 sensors. one directly before and after the first cat. the upper one is kinda hard to spot without having the car up on a lift.

thirdly, the resonator, which looks like a third cat but longer, is a straight-through design for anyone that may have been worried. i had this removed when i put in the new, larger piping.

forthly, for those who have the TRD exhaust, the piping on that is 2.25", except for at the very beginning where the flange is. it tapers down to the measly 1.5"... and for this reason, i had the flange cut off, so im running a true 2.25" all the way from the collector back.

fifthly, it does sound a bit louder now than with just the TRD exhaust. idle and cruise is about the same, but once you get over 3k rpms, it noises up pretty good. i would definitely say its a sound that not everyone is going to like. still not as high pitched as most of the hondas i hear driving around. and if it bugs you bad enough, there is plenty of room to put in another resonator, or to leave the stock one in there to help quiet it back down without restricting flow.

and finally sixthly, i definitely noticed a gain past 3.5l-4k rpms. low end still the same, but once you really start pushing a lot of air through, you can really feel how restrictive even just the back half of the stock exhaust is.

its not really worth it to get sound clips up, as it sounds pretty much the same as the TRD exhaust idling/revving, but just a little louder. and i dont know anyone with skillz good enough to get a sound clip of it while im accelerating to 70mph from outside the car.

 

Right on man, good eye spotting the 1st o2 sensor..! I could not see it just sliding under the car on a creeper. And yeah, the rear section of exhaust is about the same size as my old riding lawnmowers haha.

For mine, I am keeping the resonator & doing a larger magnaflow to keep it quiet.

 

sweet... the output on the resonator is only 1.5", but the exhaust shop should be able to chop a little of the end to make it a 2.25 or whatever size you were going with. from what i remember, the inside of the resonator is also at 2.25" and doesnt get shrunk down till the very end. i may actually put a resonator on down the road, well see how well i adjust to the sound.

 

Awesome work fellas!!!

 

I've had a custom catback 2.25 system for 3 months. The project was a low budget experiment so I just used off the shelf galvanized stuff except the tip. Replaced the resonator with a 20" glasspack and an used an 18" glasspack at the rear. Finished it off with a nice tip. Managed to keep the stock hangers/locations. Tried to keep the resonator at first, but was too loud for me. Twin glasspacks are better. (The resonator is tuned for the stock pipe size and Toyota mufflers.)

Sound is deep and fine. Highway mileage improved 2-3 percent (and incidently made the mpg calculator more accurate). This means it should be putting out a bit more power on top but don't know for sure. No apparent sensor related problems. Exterior loudness is not at all obnoxious. Interior loudness is more than I would prefer. (I'm an old guy.) The problem seems to be acoustic coupling of exhaust frequencies with the internal volume of the xD. (Can't feel any mechanical vibration.) Wouldn't be a problem in a Sedan. Not any louder than a friend's TRD muffler though. Might play with a bit of soundproofing but nothing outrageous. Or maybe not...

As an experiment it was fun and interesting. The galv'd glasspacks - the rear one anyway - won't have a terrific life but the whole project was less than 200 bucks. The stock system is certainly extremely restricted - at least after the resonator. Suspect a freer stock exhaust is the reason Toyota rates the same motor in the 09 Corolla at 135 hp. Still haven't decided whether to keep it or not, but I do like the better mileage and deep exhaust note.

 

Two more things.

1. There are two sensors with the hot O2 between the two cats. Never seen that before!

2. Thanks to the other posters. I should have shared my experience earlier. A catback system of some sort is well worth considering with this car.

 

Thanks for the info!

 

the stock headers look good enough where i wont consider getting aftermarkets until there is a dyno proven gain of at least 7-10hp. or they are being sold for a ridiculously low price. i think removing the cats or free up the exhaust more may hurt the bottom end a little too much. we need that intake manifold, dynatek!

 

Sounds to me like the first half of the exhaust line is pretty well set up. You don't want to remove too much from the car since you'll kill all your backpressure, which will hurt the engine.

If I were to modify the exhaust I would chop everything off after the 2nd cat, weld on 2.25" ID piping with a new resonator (can you fit a 24"?) and a canister muffler at the back, trying to keep everything as straight as possible for free movement. That ought to keep it quiet enough while freeing up your higher RPMs...