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Quick Summary
I had fully functional OEM cats and I wanted to free up the exhaust. I was not ready to commit to a full RB system, so I installed the Bonez straight pipe (no sniff test here in MA if >15 years old). But the exhaust smelled really strong. So throwing more money at it, I bought a Bonez high flow cat/presilencer. I am very pleased with the result and have reviewed the pipe and the cat below.
Note regarding Ari at rx7.com, I can't say enough good things about them. Ari called me when I ordered the straight pipe to make sure I knew that it would smell more than stock and he did suggest that I might want to just get the high flow cat. I pressed ahead thinking why not eek out the most from my little 12A. So plenty of informed consent involved. They really are customer service oriented and super honest. I have no skin in the game with them, I am just a happy customer and want to let you guys know they are a good vendor.
The Straight Pipe
As you can see, it's a big presilencer. It's got a perforated pipe inside the big fat section. The perforations are like small scoops intruding into the pipe but positioned so the exhaust flows over them. It is *really* solidly constructed and the welds looks functional and burly. I lapped the face of the flanges because I had leaks when I first installed it, but I think the problem was redressed more by lining up the flanges better (the flange holes are a bit generous and it allow you to adjust the centerline). I bought the bolt/gasket kit as well. 14mm bolts and 15mm nuts.
The exhaust note is gutsy and burbly in the low rpms, much louder than stock, not pingy at all. A bit wearying with the windows open (if you're 50 something) and super exhilarating and flashy (if you're something-teen). It's not an immature sound as it's got throat, but it's loud enough to be annoying to folks around you in a quiet suburban neighborhood :P. With the windows closed, you don't get a drone at all and it's not oppressive in the cabin.
As noted above, an un-catalysed 12A exhaust produces a very strong burnt gas smell, like a 2 cycle leaf blower. Nature of the beast as folks here in the form have confirmed. I've got a low tolerance for that and it was bad enough in my situation that my wife wouldn't ride in the car, and it would seriously stink up the garage. I would shut off the ignition and coast in to minimize it. You get the idea so I'll shut up about the smell.
The performance is great! I used to joke that turning off the AC was like pushing my nitrous button. A small nitrous button but you get the point...with the stock exhaust the AC really drags down the acceleration off the line. With the pipe, the extra power made that problem go away. And it revs freely. Very fun to drive and with my stock everything else setup, a little power bump makes a nice difference.
The High Flow Converter
The converter has a shorter presilencer ahead of a big version of the OEM style pre-cat, the honeycomb ceramic stuff. In the cat section there are two distinct blocks of that honeycomb with the air feed tube in the central area feeding air from air pump/ACV into the area between them. The air feed tube intrudes into the central area and is perforated, spreading the air into that section, rather than just dumping it freely into the edge of the space. This thing is also super solid. Compared to the OEM cat assy, it is much lighter.
To install it, it's the same four bolts as the pipe above, and I just reused them and the gasket of course. The air tube, though, has no flange and the recommended installation method is to cut off he flange from air pump's air tube and join them with the high temp silicone hose included with the kit. I like to be able to put things back as they were from the factory, so I built a short flanged pipe to attach to my OEM air tube. Because of the new flexible tube section on the cat end and the rubber hose from the ACV the air tube assy would swing side to side, I had to make a bracket to hold it still. I used a copper pipe mount from my household plumbing parts box.
The exhaust note is really smooth, much quieter than the pipe and very comparable to stock but with a bit more throat. I've only logged about 20 minutes with it so I'll get to know it better. I did pick up some nice rumble launching in the low rpms. I really like it. Again, no pinging or annoying drone, just a nice respectable note with some occasional *****.
The performance is still great, I don't really feel a difference between this and the straight pipe. Free revving and the AC being engaged doesn't seem to kill it.
The holy grail though is the exhaust smell is completely eliminated. Far superior to the OEM system. It's like a can of Carbon Monoxide Febreze, still deadly but now tasteless and odorless too.
Very nice write up and review. It's intriguing as I'm very close to ordering a RB header. This may be a nice alternative. I too don't care for the strong exhaust smell. I would need to do something with the exhaust manifold though, all the heat shielding is gone.
08-24-20, 09:23 PM
