So you just finished your 3vz-fe swap and are running open headers, obviously the last step is to make an exhaust. There are no exhausts you can buy pre-made that bolt into your mr2 although it is very easy to use the stock Y-pipe and and use your existing n/a or turbo muffler. I believe there are two parts to an exhaust in a mr2, the pre-crossmember which is your y-pipe, and post crossmember which includes your muffler and tips. I will start analyzing y-pipes and then mufflers.
First, the stock camry y-pipe. Here is a diagram from Toyota.
The reason the exhaust is split is so far down the pipe is so that the exhaust gases won't flow backwards or hit each other. However, that abrupt bend which 17410 is pointing is what makes the camry y-pipe poor from a performance point of view. It is an extremely abrupt bend and smooth or free flowing.
Also, there is baffling in the Y-pipe. Probably to further reduce sound. Who knows why but it definitely decreases flow and power.
Here is a picture of the stock camry y-pipe on a 1mz (it is important to note that the rear header locations on the 1mz are slightly different from the 3vz)
Note: It is impossible to accurately judge an exhaust sound from a video clip this is only to give you a rough idea
Here is my car stock y-pipe, stock na exhaust, which sounded great from 4-7k but under 4k it was so quiet I couldn't hear it at all.
Here is my car again with a mr2 turbo muffler with a small exhaust leak (skip to 7:10)
This one sounded similar to my n/a exhaust just louder and has a decent growl just cruising around at 2-3k.
So we should design our own y-pipe which is much more effective. There are many options here which I will discuss.
Option 1: Equal Length Y-pipe
This is a Y-pipe which mimics the stock design in that it has the rear bank go towards the front bank then do a 180 backwards to join the front bank. However, the abrupt bend is eliminated and a smooth bend is used instead.
Here is a good example:
Another shot on the car:
Here is Dave Mush's setup, equal length y-pipe into a 3UR-fe resonator into a magnaflow muffler (part #12266)
Here is a video of Dave Mush's exhaust
Here is Jim King's equal length y-pipe very similar
Now why go equal length Y-pipe? Well for one it evens out the exhaust pulses, but the counterpoint to that is that all the pulses merge in the stock headers and the muffler so equal length won't make a difference. I honestly don't know which is argument is right.
Option #2: Unequal Length Y-pipe
This is where the rear bank just goes straight backward and joins the front bank. This setup was used in the 1mz highlander shown here,
And here is Walka's unequal Y-pipe with an aero exhaust muffler
Here is a similar Y-pipe design by someone on Twobrutal
And here is Conor's unequal Y-pipe which actually has the pipe going underneath the crossmember
Rear shot on the car:
The advantage of this design is that it is easier to fit and easier to weld.
Option #3: Dual seperate banks
This is where each header just goes straight back into its own muffler/resonator. FabulousJ made a dual exhaust except his merged into a single X flow muffler and each outlet had a resonator on it.
Now that we have decided on the Y-pipe we have to choose a muffler and/or resonator.
Transverse Muffler (just like stock mr2)
Here are transverse mufflers, ie: mufflers that have a single inlet and dual outlet, exactly like the mr2 stock.
Brand In/Out Length Overall Part # Polished Price
Magnaflow 2.5in./2.25in. 18in. 24in. 12266 14266 $100 SS $137 polished
Magnaflow 2.5in./2.5in. 18in. 24in. 12265 N/A $97 SS
Magnaflow 2.5in./2.5in. 14in. 21in. 12277 14277 $110 SS $131 polished
Dynomax SupTurb 2.5in/2.5in 19in 24in 17739 $60
Flowermaster 80 2.5in/2.5in 15 21 42583 $92
Walker sound fx 28 18232 $44
Dynomax Ultraflo 18 24 17266 $165
Borla 2.5in/2.5in 19
Some notes about these mufflers:
I found it good to search for mufflers for a 82-92 Chevy Camaro V6 has it has the same exhaust setup as a stock mr2.
my flowmaster sounds good but has so much drone that I am
going to try something different
Clearance is tight (1/2") to the underside of the engine, and
3/4" in all directions over the cross member.
Used 2" pipe from the stock flanges, to 2.5" after the
collector, to 3" in/out from a tundra 5.7L resonator, to 2.5"
into the camero crossflow magnaflow muffler, to dual 2.25"
Some quotes I found interesting from people:
AndyA:I'm running a single in/dual out walker muffler just because it was cheap. No cat and a kinda crappy homemade y-pipe. It's real quiet till about 4000 rpm then it seems to really open up. You should try putting a pair of Supertrapps on it so I can hear what that sounds like.
John Caucasian: I think it depends on the muffler, my flowmaster sounds good but has so much drone that I am going to try something different this winter.
Bill Strong: turbo style muffler uses reflection, 2 or three tubes, redirection and packing to lower sound. It is not as free flowing. I'll draw some images. this is very simplistic. The bottom one flows much better. ?he turbo mufflers also have those ricey sounds...
There are many other mufflers out there, so I'll just post some sound clips:
Michael4age and his skytune muffler from Europe
There are so many single mufflers and you could always adapt any mr2 n/a or turbo exhaust to fit with your y-pipe as long as it comes over the crossmember.
Here is a sound clip by Sketch_hs of his single muffler exhaust
Size of the pipes, pre Y and post merge?
Size of the exhaust pipes is always a big debate in n/a applications
Gouky states, "if we do the numbers for 250HP at the flywheel which is about where i think the 3L V6s are.
intake air is about 370CFM
exhaust air is about 850CFM (using the same assumptions as the 2GR-FE above) (you divide by 2 because 2 banks)
380mph exhaust gases can be acheived in a single 2.16" ID tube. so 2.25" OD would be the minimum size you'd want to use after the merge to avoid restrictions."
I believe that on a 1mz/3vz application 2" pre-merge and 2.5" post merge is ideal. For reference the 2gr-fe comes with 2" stock pre merge and the 1mz/3vz-fe come with 1.75" stock pre-merge.