Cooley On Cars
Car Tech 101: Dual exhausts demystifiedBrian Cooley visits Johnny Franklin's Muffler in San Rafael, Calif., and shows you how a dual exhaust system works and whether you'd want or need one in your car.
[MUSIC] Well first of all before we get to dual exhaust, let's do a quick lesson on exhaust. In the first place they serve really three functions. The first is evacuation or scavenging as its known in the trade. That's the idea of getting the burned charred, that's the air and fuel that's been combusted, out of the engine. No good anymore and on its way quickly and rapidly. Doing it efficiently let's the engine generate more power by breathing more freely. It also can improve MPG. Your second major function and obviously a critical one is emissions. Your catalytic converters live on your exhaust system in line with the pipes. Now, back in the day before cats, you know, exhaust systems weren't really part of emissions so much. Now, they're a critical part of your vehicle's compliance with the law. And the last function, and the one that's the most fun, to be honest, is tone. Whether you want a really hush, quiet car or one that has, shall we say, a certain presence as you arrive. You get that done in the acoustic design of the exhaust system, either by the factory engineers. Or by the guy down at the muffler shop whose bent a lot of pipe. [MUSIC] I love muffler shops. In an auto world full of repairs that consist of primarily computer dictated parts swaps, what happens here is hand made and verging on art. Nowhere more true than at one of the best muffler shops in our San Francisco area, Johnny Franklin's in San Rafael California. Let's take a tour of the exhaust components. So in this case we've got an older car but it hasn't changed too much. No. Except no catalytic converters. Exactly Don Johnson is a third generation muffler man. Good choice to explain how it all works. So the first piece coming off the engine is? Is the exhaust manifold. Straight off this stoner head itself, four stoners on each sides for the V8. When each stoner's firing that exhaust, Yep. they've got their own port Exactly. to breathe that. Exactly and this all merges into a collector into the exhaust pipe. So now we're into the pipe and the first point Yes, both loop down each side, one over here, one over here. Yep. And then the front pipes come down to the cross member here H-5 or otherwise known as the equalizer pipe. That actually breaks the pressure between the right and left sides of the motor so this could be an X also, right? It can be an X, yeah And you would just kinda do that Yup cross over another and change sides basically Exactly But it's also helping as you guys in the bus say, helping it scavenge Absolutely Because each side is helping draw the other side's exhaust out Exactly Okay, kind of like a venturi effect, as this rushes by. It sucks some of the other stuff with it. Yep. These X or H pipes also do wonders to give the system a smoother, more muscular sound. Without it, you'll get that classic low rider sound. You'll get that [CROSSTALK] So like a machine gun sound, almost. You know, 60s Impala. Yeah. And now we just have some more pipe until we get to? The traditional duels glass packs here. They're a straight through design. There's no restrictions. So the tube actually goes through the center. It's a perforated core. So there's not much there to calm it down. And then we'll travel up and over the rear end and then we finish up with one last muffler here, the exhaust will come in on both sides and the exhaust will merge together again and then out, up the top. Out the tailpipes on each side. Okay, and then tailpipes are basically to keep the exhaust out from pooling under the car. Yeah, without it, you'll get. Fumes obviously inside the car but also without tail pipes you'll pick up a lot of harmonic drone inside the car customers that have us do no tail pipes we all kind of joke around on how many weeks before their back. Come back right>> Yeah because the drone is>> Is just the moo moo moo moo moo yeah Inside the car yeah. It's not a pretty sound. No it's horrible. Now a dual exhaust system is nothing more than a system that is two exhausts. They're identical on both sides of the car, typically running off two sides of the engine. That usually is predicated on the engine being a V configuration. But why a dual? Generally speaking, like on a, on a older vintage car, single exhaust to dual exhaust, you're gonna pick up probably about. 20 horsepower on a new modern day car you're only gonna pick up probably about 10. Still, it's a noticeable difference, yeah. And what about fuel efficiency? Does it help get better gas mileage? Pre 75, your fuel mileage is usually about two miles a gallon better. Newer cars and trucks really vary from. Nothing to a mile or two. Yeah. Lots of cars have bogus duals today. They look like duals or even quads at the rear. But they're, maybe, only dual from the catalyst on back, or even only at the tips for cosmetic reasons. A true dual is a parallel system from each of the two cylinder banks. All the way back to the end. If I see two or four tips on a car today whadda I read into that? Not so much. Most of the newer cars, you know, they'll come through the catalytic converters and then they'll split into two. In the rear of the car and it's little bit more of a fake tool. If it's a factory muffler system there's not usually a lot of performance gain. If the after-market performance mufflers got involved, yes, there is a gain there. And bottom line is using a lower restriction muffler versus a regular stock muffler. It's got a little bit more back pressure to it. So, there are a lot of ways to get a better performing exhaust without necessarily making a dual exhaust. Yeah. But a dual is kind of the more ambitious level Absolutely. Of letting an engine breathe. Yeah. Okay. Absolutely. I think the bottom line is the consumer wants to see dual pipes on the back the car. It's, it's, adds a little extra something something back there. It's, car jewelery. Great It just looks good, doesn't it? It looks great. Yeah. [MUSIC]