Question about backpressure

SON240sx Automotive
1

I did some searching but never really got the information i was looking for.

Im planning on going KA-T in the next year or so, and my current exhaust pipe and cat need replacing. Instead of going stock I would like to throw in an exhaust that will still work nicely when turboed, currently my ka is near bone stock, only an injen intake.
Now, my question: Would the stock cat provide for enough backpressure with a 3" exhaust system (Apex’i N1 Single)? If not, how much hp/tq would be lost in the swap?

Thanks

2

the stock cat is pretty restrictive, even still, when i was planning to put the SR in i had to replace my exhaust. i ran 2.5" with a high flow cat and straight though muffler on the stock motor with an intake. i didnt have any problems. however that motor was knocking and i didnt care about it. it still made a 3000km road trip like that, plus the KMs i put on in town

mike

3

http://forums.neo240sx.ca/viewtopic.php?t=1811

4

Just go straight 3" with a high flow cat.

You should gain some top end power and lose a bit bottom end. There shouldn’t be any real disadvantages, I know there are a bunch of stock ka guys on here with 3" exaust…

5

Alright thanks guys, I just needed some clarification on the subject. In my searches i found many contradictory comments, its hard to find a credible source for some things on the net.

Now for an NA engine you would still recommend a high flow cat? So am i just trying to minimize backpressure?

6

Pretty much.

I think Jantos had/has 3", so do I, but I’m not stock ka, I think Mr.Skinny has 3" too, try checking with one of them.

7

If you go too large a diameter on an NA motor, the low end of the powerband won’t push enough air to get a good flow; the flow will be really slow and there will be turbulence. The bigger the exhaust, the more low end power will suffer… but high end power will increase. And vice versa.

8

yup, i have a 3" JDM Bee*R catback on my basically stock ka at the moment, i don’t even have a cat but that’s going to change… other than noise there are no serious ill effects, if you plan to turbo go with it forshure… actually it’s rather hilarious the tone of this system is so low it jsut nuts, it’s loud but good loud, and when turbo ought to be quite nice

9

mmm 3in test pipe to 3in straight through exhuast…

10

mmmm… 4" downpipe, 4" cat and oooeeee here it comes… 4" Exhaust :wink:

11

hehe yeah you got a deal on that man, that was some good luck i wish my 3" exhaust turned out to be 4" when it got here

12

Ok, now does anyone know a good reliable place to get a custom exhaust made? Im considering this option to compare prices, so any approx prices on what is out there would be a big help.

13

Metalex Motorworks in Mississagua

Contact Radim at 416-894-4457

Tell him Adam from Neetronics Highly Recomended you…

14

Yah, Adam recommended me there for some welds I needed done…
Just from talking to the guy and his workers, and looking around at their cars/projects, i was very impressed… Give him a call.

15

I will do so, thank ya sir.