Project V8 RX-7: Part 9 - The Exhaust

by Jeff Naeyaert

The title picture already gave it away, so I’ll save the prose, it’s time to build an exhaust!  This isn’t going to be a sissy grandma exhaust either like on Project G35 whose owner couldn’t stand how loud the Berk exhaust they originally installed was… in fact, it's the same folks at Berk that are gonna kick it up a notch and help us make a super bitchin’ set of pipes that’ll make children cry and leave no question in any Rotard’s mind that our dead Wankel was replaced with a big ol' hunk of American Iron aluminum!

The only caveat is this has to be able to pass a smog referee’s inspection. To our knowledge, they only look at the stuff that effects emissions—not sound regulations.  This is only based on our personal experience dealing with them the first time I went through inspection with the LS1 powerplant.  Either way, we’ll know soon enough when we try to pass!

We do know for certain that we are required to use all 4 catalytic converters that came with the E-ROD kit—so no headers (yet). 

The exhaust manifolds and secondaries provided with our E-ROD kit.

There is however NO way that the secondaries with the cats on them are going to just bolt up and fit as is on our RX-7 (unless we make it a Donk car) so that means we gotta chop ‘em.  This is a gray area that we don’t have a lot of solid information on (feel free to comment if you know something we don’t) but it is our understanding that you can chop and turn things to fit but the cats and oxygen sensor locations relative distance from the manifolds must remain the same.  In other words, we can’t chop the cats up and move them back 2 feet farther down the exhaust stream.  Makes sense, and that’s something we can live with!

We decided in order to save money (not time) that we’d fabricate the exhaust sections from the manifold down past the cats ourselves using just the parts we chopped up.  We’d then order new tubing to do the cat-back portion and let a professional handle that part (saving money because we’d inevitably ruin a lot of good new material AND time!)

Time to hack!


All chopped up, we separated the cats from the flanges.  Where possible we plan to just rotate and change the angle of the existing pipes so we maintain the catalytic converter and O2 sensor distances from the heads.
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Blair Ellis
Blair Ellislink
Tuesday, May 29, 2012 2:42 AM
Was the reason for using the oval tubing to increase ground clearance, just unique cool factor, or...?
Tuesday, May 29, 2012 4:16 AM
Looks to me like ground clearance. You'll notice in the last pic the exhaust sits under the driveshaft. Oval tubing allows a bigger exhaust diameter without hurting ground clearance.

Looks good. Between this car, the Miatabusa, the LSR 240SX, and the ARK GT-R, it's looking like MotoIQ has the craziest and most awesome project car stable on the net!
Tuesday, May 29, 2012 5:22 AM
The exhaust looks a little like some sort of sea monster in the title shot. Keep it up Jeff! I'm enjoying following along on this project.
Tuesday, May 29, 2012 8:07 AM
I noticed you guys had to move one cat a bit further out. Do you think it will pass inspection like that?
Wes Dumalski
Wes Dumalskilink
Tuesday, May 29, 2012 8:26 AM
Badass all the way around!

Tuesday, May 29, 2012 10:12 AM
I've always bought Burns Stainless Steel (exceptional quality).
How would you compare Vibrant to Burns?
Tuesday, May 29, 2012 10:12 AM
Oval tubing for better aero, amirite? ;)
Jeff Naeyaert
Jeff Naeyaertlink
Tuesday, May 29, 2012 10:58 AM
Oval does have better clearance, but also looks better too--fits the cutout on the rear bumper better than a round tube :)

Kaane, it's impossible to say without actually visiting the Ref, one might say its fine and another could fail it. From what I've heard, as long as the front O2's are basically the same distance from the heads as the kit provided and the rear O2's are immediately after the first cat I think it will be OK. You'll have your answer soon though!

JDM I've not personally used Burns on any of my stuff yet (but if I put headers on this thing that will change) and I didn't do the welding on the Vibrant tubing but it LOOKS really high quality. Check back in a year!

Dusty Duster
Dusty Dusterlink
Tuesday, May 29, 2012 12:02 PM
I'm told inspection stations in Northern California are more lenient...
Tuesday, May 29, 2012 2:56 PM
One day, they will make LS3 manifolds that fit my E36 and I can get my swap fully legal :(
Jeff Naeyaert
Jeff Naeyaertlink
Tuesday, May 29, 2012 3:08 PM
frame rails too narrow? you try LS1 manifolds?
Tuesday, May 29, 2012 7:04 PM
Steering shaft is in the way. Tried every combination of LS based manifolds, nothing fits. Using custom longtube headers that go around it. I might try some carb approved shorty headers in the future.

Here is some pics of the finished project with a dynosheet.




Tuesday, May 29, 2012 10:46 PM
Wow, serious tube work! Any plans for heat shielding around the cats? They look awfully close to those solid fuel lines... and that oil filter... and just... everything! The local legislation obviously makes it necessary to pack the cats in like that, but I'd be freaking out about the such a high-temperature and heat-soaked component being hemmed in so tightly.

Just always drive fast for good air cooling!
Wednesday, May 30, 2012 7:17 AM
I am sure the cats will only stay on the car until inspection lol....
Der Bruce
Der Brucelink
Wednesday, May 30, 2012 8:20 AM
Jeff - I may noy be a CARB ref but I did stay at a Holiday Inn Express once.....
Anyway, If memory serves me, you are not allowed to remove or alter any of the antipollution devices. Technically, you are not removing or altering any actual anti-pollution device. You are merely altering the angle at which the intermediary pipe connects the two. I could go on with more but I can't imagine you being in the wrong here.
Jeff Naeyaert
Jeff Naeyaertlink
Wednesday, May 30, 2012 10:00 AM
Damn kaane, that's a BEAUTIFUL car! Where did you get your LS3? be careful putting your plate out there for the world to see, never know when big brother is watching! So nowhere to relocate the steering column either? Is that a stock LS3? Just wondering if GM underestimated the power on those too!

Messiah, yep there are plans for heat shield, we just didn't get it in time. Maybe next time everything comes off.

Bruce, first lol, second you also must maintain the approximate distances for the O2 to work properly. I hope I'm right too! :)

Wednesday, May 30, 2012 12:11 PM
I put the motor together myself. Found a low mileage LS3 shortblock, bought some LS3 heads and LS3 intake. It is running LS1 electronics since I had a LS1 in it before. Cable throttle.

It has only a small cam 222/230 Duration 114LSA, around .600 lift. Full exhaust and that's it. Makes decent power for just cam.

Not much room to relocate the shaft, too much work either way. I'll try some shorties, they might work.
Wednesday, January 06, 2016 6:38 AM
Get you South Dakota plates, shorty headers and cats have no place on a hot rod. Having paid a 700 dollar "back registration" ended me caring about the water air or ground in California.
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