Types of Exhaust Systems

[Nix]

If you're not running gaskets, there is a chance you are creating an exhaust leak at the joint. If exhaust gasses are leaking and disrupting laminar flow with eddy/turbulence you could be losing power. You want them to go as quickly as possible from engine to exit.

I doubt you're losing much power with it. Just sometimes low in the rpm range you lose some tq which you will feel but gain hp on the high end.

 

[Brooksie365]

do you have the silencer in? i had the same exhaust but due to design flaw and volume i sent back, when the silencer was in there was a definite power loss..

 

[323]

I feel I gained a lot of tq from mine.
After my intake, exhaust, and downpipe, even before a tune, I could get a chirp going into 3rd at about 35 mph

 

[Sinub]

No no silencer and I got my gaskets yesterday, im gonna try to put em on today

 

[Sinub]

Still no gaskets on ): I have to wait until Monday so I can use my school's lift

 

[Sinub]

Got the gaskets on yesterday!!! Loving it, now I'm feeling some gains, exhaust tone changed, a bit deeper now, smoother and sway bars came in today!!

 

[Sinub]

Normally, NA cars don't have downpipes since the exhaust side of the head will have outlets connected to a header, or headers depending on the engine size. The 2012 Si's K24 engine is an exception with having a downpipe since the engine's head has an integrated header collector on the exhaust side which has only one outlet.

I know this is a late post on this but can you go into more detail on why we have downpipes or how what you said works?

 

[Dar-Dar]

The exhaust side of the K24 head is collected into one outlet. For example:

While the K20Z3 has 4 outlets (one from each cylinder) on the engine head:

 

[Sinub]

The exhaust side of the K24 head is collected into one outlet. For example:

While the K20Z3 has 4 outlets (one from each cylinder) on the engine head:

It all makes more sense now!! That's why we there's no aftermarket exhaust headers or manifolds and thats why our's is integrated correct?

 

[Dar-Dar]

It all makes more sense now!! That's why we there's no aftermarket exhaust headers or manifolds and thats why our's is integrated correct?

Pretty much. Aftermarket downpipes are offered for the 2012+ Si's though.

 

[Sinub]

Ok last question, why do turbos have it? Is it so it has unrestricted airflow into the turbo for the exhaust gases to power it? If so can you show me a picture too?(I'm a visual learner)

 

[Dar-Dar]

Well, with a turbo charger, the total collected outflow from the engine goes to the turbine which forces more air going back to the engine. Since the K24 already has one outlet (total engine outflow), a turbo manifold would be simple in design. Turbo manifolds are used so the total outflow on an engine will be directed to one outlet.

For example:

^This turbo manifold K20 example collects the outflow to the turbine.

An example turbo manifold for the 2012+ Si would be something like this:

 

[Nix]

nicely summed up Dar-dar.

 

[WhiteWillie]

Very informative thread guys. Many of my questions were answered.