Ted Breaux - "True dual exhausts explained"
Ted Breaux - "True dual exhausts explained" January 12, 1998
Just for the record, here are the facts as I have noted them since 1991:
The Borla exhaust power claims were a complete sham. The dyno facility which performed the 'test' was noted for this and went out of business shortly thereafter. The Borla exhaust is nothing more than a very expensive muffler change. The pipe diameters are the same. These are facts.
The Dynomax isn't a bad design, but is hampered by the sloppy weld work at the back split which leaves metal hanging in the wind at that area. Cut it open, and you'll see what I mean.
You can never get a very appreciable power increase out of your exhaust system until you fix the horrible factory catalytic converter problem. An aftermarket cat assembly is a major key to getting more power. If you like a nice sound out of your SHO, do the following: Replace the factory mufflers with two Walker #17796. The entire operation will cost you about $125, and will sound INCREDIBLY better than the Walker system, and will
make the SAME nominal power increase. Mark my words here, I know what I am talking about. I think every SHO out there should have this mod if nothing else. It will really put a grin on your face, and not be at all obtrusive.
The Sho Shop system with Y-pipe is plenty good enough for 98% of people out there. It is basically a much better and cleaner version of the Walker system. It is as fine a system that can be packaged and sold.
The Y-pipe is not 'tuned' to match pulses, nor can it be. The unequal length of the head pipes prevents this entirely. Let there be no question here. If the head pipes are not equal (tough on a transversly mounted engine), there is no real 'tuning'.
When I put true duals on my SHO back in 1991, there were no exhaust options. I put a press bent 2" dual system with aftermarket cats and Walker #17796 Super Turbos, and the car ran like all get out. The entire system cost me a grand total of $580 for parts and labor. With the advent of the LPM, I was able to tune the fuel curve, and the sound of the exhaust got mellower and the system continued to gain power.
A properly installed true dual system can be rattle-free, inexpensive, and sound great. If you listen to my car next to a Walker equipped car, there is no comparison. The car which sounds like an exotic is mine, while the one which sounds like a 2-stroke motorcycle is the Walker. The funny sound in 2-1-2 systems results from 6 pulses crashing unevenly down the same pipe. Hence, the dual exhaust has a distinctive exhaust note due to the better pulse separation, and this is does nicely, regardless of the cats. This is a phenomenon you can actually see, so don't take my word for it.
Additionally, if positioned correctly, the cats stay hot and work very well, thank you.
A true dual system will lean the mixture slightly in some rpm ranges, simply because it increases airflow (i.e. 1+1=2). This is why unless you use the proper mufflers to minimize, you will end up with some raspiness. Even so, you may still have some raspiness, depending on the particular car. The LPM makes the fuel correction, brings in the torque, and mellows the exhaust note.
The optimum crossover point for a balance tube as someone already mentioned will be at a different location on each pipe. The length of the tube to meet these points will cause further complications. I specified roughly where the tube worked best for me, but there will inevitably be variation. You may not even want a balance tube. Again, the Y-pipe is neither 'tuned' or 'balanced'. I mean, the Y-pipe is a very nice piece of hardware, but you can't tune it any better than you can tune a crossover tube for precisely the same reasons (i.e. unequal head pipe length). Let's not get confused here.
When you put a turbo, blower, or different engine configuration (i.e. Supra) in a car [Really? Supra? -ed.], the exhaust concept changes. With an inline six mounted longitudinally, or even a V8, a large single system can be made to be ultimately comparable to a dual system as long as even tube lengths are maintained. Even so, the (degree of) trade-off will vary with the specific application.
The truth is, if my recommendations are followed (as per the guidebook, which is why I wrote it), you'll end up with a big smile on your face every time you drive the car, and you WILL absolutely, positively feel the power difference....there's no mistaking it. With the true dual setup, my car had more low speed torque than factory (much more), and had top end for days. If you are not an experimenter, then don't go the experimenter's route. It matters not to me what exhaust you have on your car, so I feel pretty objective where this is concerned. If I had a SHO and I wanted it to run as best as possible for minimum dollar, I would get a true dual exhaust with aftermarket cats ($600), 80mm MAF, LPM, and UDPs. With that you've spent maybe $1200 and you'll have a fun toy to play with which will also have the virtues of being practical, economical, and dependable.
[Editor's note: Parts of this article directly contradict Vadim's article above. All I will say is that Vadim was ousted from the SHO world in disgrace, while Ted became a celebrated hero of the SHO world, then went on to brew some fine Absinthe, which you can drink in the US today largely thanks to him. I'll let you make your own conclusions as to which of these articles you should put more faith in. -Hawkeye18]
