Just got a quick question, I current have an apexi noir exhaust system in my EK which has I believe 2.36" diameter (inside) piping (with hollowed out cat). I like it because its quiet and doesn't attract too much attention however its been recommended to me to go 2.5" all the way back. How much power am I being robbed of by not going 2.50" all the way back? Motor specs below

Motor
- B18c Jdm TYPE R
- Chipped ECU (tuned by TEKNOTIK)
- Big Tube Hytech rep (on its way, not installed)
- Apex-i noire exhaust
- Skunk2 pro 2 series cams
- Skunk2 valve springs and titanium retaners
- Skunk2 adj. cam gears
- Skunk2 68mm throtle body with boared out intake man.
- Precision 310cc injectors
- password jdm intake (whale *****)
- Shaved head (to service line)

Once I get my header I'm taking it to get retuned (head has been shaved more, new header and new intake since it was tuned last). I would rather keep this exhaust but if I'm really being robbed of a lot of hp I might consider upgrading to 2.50".

Any input? Thanks :d

E

 

I don't know if shaving the head to the service limit is a good idea b/c u are playing the the cam timing. Seems u are trying to up the compression a cheaper way use the cams.

O and to answer ur question maybe 5 whp 5tq maybe i'd say

Me i'd try 3 inch exhaust let it breath.

I have an h23vtec 11.5 compression with 3 inch exhaust with not cat but moroso spiral flow muffler 3 inch into a flowsound muffler its and off brand flowmaster nice deep and quiet sound and no restrictions.

 

I have that same exhaust. From what I've read it's not necessarily the piping that is so restrictive, its the muffler. I've heard the mugen twinloop is just as quiet and is much less restrictive.

 

I honestly think that with your setup, its still able to flow enough air through it, therefore not being robbed of any power. On my 1.8 with 11.5:1 compression, ported head, header, IM, cams, etc, I made the same HP through the muffler as i did open header, both tuned. And thats through a RS-R Ex Mag.

I know for a fact that the RS-R can support 230 whp no problem. Thats from dynoing it on my 2.0L now. And when i ran it open header on my 2.0 i gained 6-13 whp in the 6k rpms to 11k rpms.

So unless the Apexi is way different i would expect similar results.

 

The head was originally shaved 0.30mm and tuned. I recently got the HG changed and the head had to get decked, it was decked down to the service line (wasn't a choice)

Will look into it thanks.

What cams were you running on your 1.8?