Critique my exhaust shopping list

I'm building a new exhaust for my 82 Datsun 280zx out of mandrel bends. I've got a 2.5 inch downpipe from the T3 turbo currently going to the stock cat and then it becomes 2" out to a straight pipe in the back. I'm planning to replace the cat and go 2.5 inches all the way, and add a muffler. I want to tone it down at idle but keep a growl at higher RPMs. What do you guys think of this shopping list?

MagnaFlow 12616 - MagnaFlow Performance Mufflers 2.50 in. Inlet/2.50 in. Outlet, Stainless Steel, Natural, Each

MagnaFlow 53956 - MagnaFlow Universal Spun Catalytic Converters Universal, Stainless Steel, 2.50 in. Inlet, 2.50 in. Outlet, 8.0 in. Length, Each

Summit Racing SUM-622003 - Summit Racing® Exhaust Tubing Mandrel Bends Exhaust Tubing, 180 Degree, U-Mandrel Bend, 2 1/2 in. Diameter, 5 in. Radius, 16-Gauge, Steel, Each

Summit Racing SUM-690052 - Summit Racing® Stainless Steel Exhaust Tips Exhaust Tip, Stainless, Polished, Slant/Rolled Edge, 2.5. in. Inlet, 3 in. Outlet, 8 in. Long, Each

Summit Racing SUM-692250 - Summit Racing® Band Clamps Exhaust Clamp, Band-Style, Lap Joint, Stainless Steel, 2.50 in. Diameter, Each

Walker Exhaust 31900 - Walker Exhaust Flanges Flange, Exhaust, 3-bolt, Low-carbon Steel, Natural, 2.5 in. Diameter, Each

Looks good, but I hope you know that muffler isn't going to tone it down a whole lot. You might want to go with a bigger volume glasspack.

Also I hope you know mandrel bends are crazy-expensive, the extra labor expense can be worse than the extra parts expense. I went with regular crush bends because of the cost, the shop did a good job with them, no crimping and the diameter reduction is so small that they almost look like mandrel bends, but I don't know what tool they used to do that.

It's turbo'd with a cat. He might not even need a muffler.

I'm getting a couple of U-bends and cutting then welding it together. It takes a long time, but is straightforward enough to do.

With the turbo and cat now, the car isn't very loud. I don't want to make it any louder. I need to pass tech at limerock ("muffled to 86dB") and autocross ("must be muffled").

I would buy the bends and hardware from http://mandrelbends.com, but that looks fine to me otherwise.

And yes, a turbo car doesn't need as much muffling as a NA car, it also doesn't need much of any back pressure in the system (the turbo provides enough of that). I've run that same muffler on my street turbo cars and passed noise regulations here in the PNW (92db).

The only caveat I'd make you aware of is that sometime an open exhaust can cause boost creep. So be prepared for the potential to make adjustments to your wastegate control solution.

I don't think any engine needs any backpressure in the system...

turboswede wrote: I would buy the bends and hardware from http://mandrelbends.com, but that looks fine to me otherwise. And yes, a turbo car doesn't need as much muffling as a NA car, it also doesn't need much of any back pressure in the system (the turbo provides enough of that). I've run that same muffler on my street turbo cars and passed noise regulations here in the PNW (92db). The only caveat I'd make you aware of is that sometime an open exhaust can cause boost creep. So be prepared for the potential to make adjustments to your wastegate control solution.

About the turbo car not needing as much muffling as an NA car, I have to slightly disagree and say it depends. My room mate and I thought this a few years back, and he ended up with an SR20 + turbo + small muffler that was more than 100 dB at 50 feet at autox while on the same day my 302 + tubular headers + mandrel bends + small muffler never touched 90 dB. 10 dB = twice the volume I think.

His was rough to ride in on the highway too because it was so loud.

Take it from someone that has owned 3 z's two 280zx's and a handful of other datsuns. The L28E isn't a loud motor to to begin with. Now strap an N42 head and triple mikki's and it'll be nice and rambunctious. The L-junktronic efi quiets that's motor nicely. You won't get "growl" up top. Not with a factory cam and turbo. You get it low range. That's the nature of the efi L28e. Turbo will be even quieter. Open her up. Straight exhaust. No cat if possible.

Mouse, car is a NA to T conversion. So I swapped the manifolds, bolted up the turbo, and am running Megasquirt n Spark for fuel and timing. I do need a cat, my state does a visual check at annual inspection.

I'm almost set to place my order. Just need to make up my mind on using collector flanges and copper or aluminum gaskets, versus band clamps, to hold the segments together. Hmm.

Everyone always says band clamps...but I put one in my exhaust and it hasn't been foolproof, leaked right off the bat. I readjusted it but I haven't been able to run the engine a second time to confirm whether it's still leaking or not.