I have wanted to put a true dual exhaust on my TA
since it was new. I also wanted it to (hopefully)
pass CA emmissions. The main hold up all this time
is that there were no CARB approved ODDII catalytics
in the aftermarket area. Once I found out that
Magnaflow had them I went for it.

Here is the basic data on my car for the "before"
dyno run:

1997 WS6
Convertible
T56 w/ 3.42:1 Rear Axle
HPP+ (w/ 160° thermostat)
3” Cat-back Exhaust w/Flowmaster 80 Series
TPIS Adjustable Fuel Pressure Regulator
Granatelli MAF
K&N Air Filter
Airfoil
Accel 300+ Digital Ignition
GMPP Hot LT4 Valvesprings
Comp Cams Pro Magnum 1.6:1 Rocker Arms
Crank Reduction Pulley
LT4 Knock Sensor Module
Bosch Platinum +4 Spark Plugs
TPIS Spark Plug Wires
Throttle Body Coolant Bypass
17x10 WS6 Rear Wheels w/315/35/17s

Dyno Results: 298 rwhp / 316 rwtq

I then installed the true dual exhaust system shown
in the pictures below (thank you again Brent):


http://www.bfranker.badz28.com/misc/td02.jpg
http://www.bfranker.badz28.com/misc/td03.jpg
http://www.bfranker.badz28.com/misc/td04.jpg
http://www.bfranker.badz28.com/misc/td05.jpg
http://www.bfranker.badz28.com/misc/td06.jpg
http://www.bfranker.badz28.com/misc/td07.jpg
http://www.bfranker.badz28.com/misc/td08.jpg
http://www.bfranker.badz28.com/misc/td09.jpg

Dyno Results: 310 rwhp / 324 rwtq

I am waiting for someone to send me a video of the last
pull and will try to post it later.

This is expensive horsepower but I was doing it for
many reasons and the extra HP is just gravy. The
exhaust system cost $1,200 and is 2.5" mandrel bent
throughout. $85 for tips, $20 for base flanges, $15
for gaskets, $450 for catalytics, $120 for mufflers
all adds up to $690. When you consider the above parts
necessary to make this happen, the labor by the shop
is very reasonable. I don't know what 2.5" tubing
costs but there is a lot of it in this system.

Considering that the shop spent close to 12 hours
working on the system it all adds up. I have known
the owner and have had many systems done there so I
know he treated me well.

I spent quite a bit of $$ to gather this information
so I hope it's useful to some of you considering a
similar setup. You will notice that I do not have
headers on the car. As you can see, you do not need
headers to make over 300 HP on an LT1. And my mod list
is just typical bolt on stuff (exc. for the 1.6:1 rockers).
I love this car!

 

Wow, that's impressive #s especially since you didn't have headers. I'd say those were good numbers even with headers! Put some 1-3/4" LT headers and you'd have 330 rwhp on a bolt on LT1. That's insane for a bolt on LT1! Gotta get me some true duals.

 

I bet at least half that gain after the duals was due to getting rid of that crappy flowmaster. You would have probably seen at least an 8hp gain by just swapping to a borla as well.

None the less.....awesome numbers!!! I love the sound of true duals. Maybe Ill have to do that to compliment my LT headers one day....my borla sounds like **** now days IMO anyhow. Ill have to start looking into this.

 

the main power improvement from duals is that it gains power in the entire area under the curve.........not just the peak numbers as you would see swapping out the flowdisaster.


this post is nice proof though, for those people who say that true duals is too much for a bolt-on car.

 

i lost 10hp going from true duals back to 3" ypipe/loudmouth

 

Truedualws6....I need some help now. After a hr of thinking I have decided to do a setup like this while the car is down.

I just called my local muffler shop(Jaks House of Bends)....and asked him if he could do a true dual with 2.5" pipe for me. I told him I have an LT1 and he said....thats impossible to do, not enogh space over the axle.

So, I said...well if I send you pics and a post of a setup thats done on a LT1 could/would you copy it. He said...yeah, if you can manage to find someone thats done it. HeHeHe, lol. He obviously doesnt know about these awesome message boards

So, I emaild him the pics and link to this post a few min ago, then called him. He couldnt believe it. He said,..."Im so stupid for never thinking of that"<--meaning run both pipes over the one side of the axle then their sepearte ways.

To sum it up....he said, bring in your beast when its ready and well do the dual setup for you. Without this post and the pics...I would have been up **** creek.

Thanks for this post!!! I have hated my catback but never really though it would be as easy as you made it seem to do a true dual setup. Now, will you let me in on any part numbers/names of the parts you used(ie, the mufflers cats, etc). Im going to setup like your(but with my LT heades) but have flanges welded in to remove cats for offroad pipes, hummm or maybe I can use cutouts as Offroad pipes and have flanges welded to them for that exta 2hp at the track

 

Here is the dynograph up for you too

http://www.bfranker.badz28.com/misc/Dynographs.pdf

 

Nice system,and gains.How do you like the sound?

 

this is great. I'm doing the same thing for the new motor. Turn downs at the axle though, but I might try over the axle like you did.


Neal

 

Your car was impressive BEFORE the dual exhaust, now it just sounds even better I bet! 298 with manifolds, without knowing any better I'd guess that was an LT4. I know the SS Camaros in 97 were, what about the WS6? Anywho, great numbers and post some sound clips!

 

It does sound great but it's too loud for me too
keep my sanity. The sound outside is really nice
but the internal drone and resonance is hard to
handle (typical Flowmaster). It's so bad that I
have about 5 new rattles and vibration points.

I am trying to come up with a way to record a
nice sound clip and will post once I do so. I think
the video of the last dyno pull is lost. If anyone
has recommendations for a different muffler to
cut back the noise please let me know. It has to
fit in the same general area as the little race
mufflers in the pictures.

 

Tough fitting anything else in there that is gonna quiet it down significantly. You could replace them with dynomax bullets but it's still gonna be loud.
Or you could leave the flowmasters and add a couple of bullets somewhere upstream. The long straight going to the driver side is a good place but the passenger side pipe isn't as easy. You need to see where you have the room. Maybe in that stretch after the cat before it joins up with the other pipe?

They come in 12 and 18 inch length so you might be able to find a spot where one or the other will fit. Longer is better for muffling but something will be better than nothing, thats for sure.

Looking at the system design, it would have been easy to incorporate the bullets with a little forethought. Just take a close look at what you've got and I'm sure you can work it out.

Nice clean setup by the way.

Good day!

 

could also put in some chambered pipes, not real big and dont take much room. or twister

 

How can true duals be too much for bolt on cars if corvettes have true dual exhaust from the factory?

 

Nice numbers