Am I the only one who very much does not like dual exhausts on inline engines?

29 Jun 2016

Dual exhausts were originally created for V shaped engines, as they had two exhaust manifolds and could therefore benefit from two mostly separate exhaust pipes. Over time, the dual exhaust became a fashion piece on cars. Some vehicles that had a V shaped engine were single exhaust up until the end of the system, where it branched into two separate tips. This is what is known as “fake duals”. Recently, inline engines have been leaving the factory with the fake dual exhausts. Is it for performance, or just looks?

An excellent example of a fake dual exhaust on a stock vehicle is the Subaru WRX and STI. The dual portion of the exhaust starts right as the passenger compartment of the vehicle is ending. Does it matter if it’s a fake dual exhaust, though? Will it still give a performance increase?

The simple answer is no: A fake dual exhaust on an inline engine will not give a proper performance benefit. The reason for this is that, although it may breathe more freely than the stock one outlet exhaust, a single larger diameter exhaust would be more efficient. An exhaust system with two pipes effectively doubles the weight of itself for as long as it has the second pipe. This adds weight that is unnecessary, which we all know ruins performance. A dual exhaust also splits the exhaust flow in separate directions, which impedes the straight flow that would be ideal and easily done with a single pipe.

In conclusion, a larger diameter single exhaust is better for all aspects of performance on inline engines than a dual exhaust system. Is it still worth it for you guys to have the looks of a dual exhaust, even while compromising performance? Let me know why in the comments below.

Comments

I have to agree with you on that one, my car was delivered with 2 manifolds (inline 6), which are going into one catalytic converter and back to 2 exhausts. And its never been designed to be a performer in the first place, so a lack of power is there from the factory. But a car thats over 2 meters wide doesn’t look food with a single exhaust pipe imo

But it seems like such a bad place to cut expenses, when it could have been a true dual exhaust for only a little more. I know quite a few V8 trucks from the ‘90s and so came with true duals all the way until the very back. Even having two mufflers, and yet still only one exhaust outlet.

You have a point. Dual exhausts like mine that never converge make sense although they add weight, but I wouldn’t want one large diameter pipe for aesthetic purposes. Dual exhaust provides symmetry.

Symmetry is all well and fine, but I prefer functionality over looks. Even on mundane DD, I’d like everything on my vehicle to add something to it.

I saw a car earlier with one exhaust smoking badly and the other exhaust tip was completely clean

If it was a v shaped engine, that means that one bank was (presumably) leaking oil into the cylinders while the other one wasn’t. For an inline, it’d be because of one outlet putting out the majority of the gasses. Or it could be a complete fake, but those aren’t common.

Honda S2000 :v

Yeah, that’s another good example.

Since when do Subarus have “inline” engines… Anyways you have a good point and I think fake duals are silly and manufacturers should end the trend. The WRX and STI could be a candidate for true duals if sized appropriately as their systems both start and end with dual pipes but you would still add unnecessary weight.

Excuse tiredness. Meant to compare inline and flat. Thanks for pointing that out.

Dude WRX’s rnt inline

Someone beat you to it. Thanks though.

Does this count? Only dual tips

Not a big deal. Adds almost no weight, nor does it much disrupt the flow.

If the design calls for dual exhausts then use duals,if not,don’t use them.As far as aesthetics are concerned,if it’s a performance car than it should have two exhaust tips,twins or duals,whatever the design dictates

I don’t think that a class of car should dictate it’s design. Putting a design piece on to make it look fast is rice.

Have cylinders 1&3 on the left bank, 2&4 on the right bank

Talking about a V4?

Most german I6 from around the 80s & 90s do use separate pipes for each manifold, one for 1, 2, 3 & the other on 4, 5, 6 cylinders, both go side by side all the way back & joins the resonator or silencer.