HT! I have a B16 and recently purchased a header with a 2" downpipe. If I connect the 2" downpipe to a 2.25" catback, am I losing tons of power here with a smaller 2" downpipe?

Does it even matter? Should I cut that small pipe and change it for a 2.25"?

Any feedback would be great, thanks!

 

You are perfectly fine with those sizes - it's actually the preferred largest you should have to go while N/A. (Given things can be tweaked upon, but you are too close to stock to worry about it.) Enjoy the gutless wonder!

 

awesome. thanks for the reply. I kinda figure that but wanted some further opinion. Appreciate it!

 

My opinion 2in is way to small even for a stock B16. I have done a lot of work here at Bisimoto see what works well on small displacement Honda motors and have seen minimum of 2.5 inch collectors and even up to 2.75in to prevent horse power being robed by back pressure.

Here is a picture of the Bisimoto V2 Header design on a relatively stock B18c with a 2.75in down pipe.



Also here is a dyno of a stock B16 with a Bisimoto header:

Stock head
Stock Bottom end
Bisimoto V2 Headers vs DC
440 cc injectors
Test Pipe
AEM Cold Air Intake
AEM EMS
2.50" exhaust
Stock Cams
Bisimoto Cam gears
Made 9 whp peak gain with V2, and 6 wft/lbs of torque

 

^ Shameless plug?

I'm personally running a DC Stainless header with the 2.5" collector mod, 2.5" True Catalytic Converter (not test pipe), and 2.5" Thermal R&D Stealth on my B18C1. She breathes wonderfully up top though I lost a little bit of my "off-the-line" *****. Honestly though, you should be just fine.

 

Oh everything was so stock with thousands of dollars in add ons... Nobody was talking about running a header that was tuned... he bought some garbage off eBay and wanted to know if it would work for his application. For all around driving in a street car without losing bottom end or greatly sacrificing top end, 2"/2.25" is where you want to be. I thought a company that puts so much time into R&D would know this already? Why would you step in to try and confuse somebody while shamelessly trying to promote your product? Go and put a 2.75" collector on a B16 with an untuned header and watch what happens to the powerband... especially for a car that is for the street. We aren't talking dyno queens either - or "street cars" that sit in the garage either.

 

n/a hondas work best with 2-2.25 pipes, boosted 2.5-3.0, the thing is, that once you put too big a pipe on you have no backpressure, while backpressure isn't necessarily a good thing, you need some, if not then you lose VELOCITY...that's why you'll get less power and torque. Too big a pipe just lets the exhaust more so drift out and let it go wherever without actually pushing it out the exhaust efficiently. READ THIS http://www.8thcivic.com/forums/bolt-...le-sticky.html

 

I just posted a completely stock B16 motor with good header and ecu for tuning. For information purposes about back pressure can rob power even on a stock street car.

With a dyno chart of direct comparison of a regular of the shelf street DC header vs a Bisimoto V2. The Bisimoto headers showed power gains both HP and Trq through out the entire rpm band with no drop of low end power what so ever. Even picked up torque between 2000-3000rpm which a street car would appreciate.

Any engine modifications should always be tuned appropriately to compensate for air/fuel rations if you want to have a reliable setup for either daily driving or racing and I would highly recommend tuning with a Bisimoto V2 header or any other header as well.

 

good point here.