Too big of exhaust?

86Gram

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I have a 2003 Honda Civic EX. I put a cold air intake on and then installed headers. I noticed an noticeable increase in power and was pleased. I bought an two and a half inch catback exhaust. I was told bigger exhaust would mean less restriction and better performance, I didn't notice an increase and actually thought it might be less. I don't like that raspy sound so I'm adding a resonator. I looked on the internet and saw that it shouldn't be this large diameter exhaust. So did I go to large that I lost horsepower? and if I did is there anything I can do to remedy it like making more restriction? I do have the end tailpiece cap on which it's a little restriction on it. That tailpiece is a couple inches long and I took some boiler insulation rope and wrapped around inside to quiet it down some which it did help.
 

nd4sped

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The cap you inserted in the muffler is to reduce overall noise. It will reduce power but you may not notice a difference since your car is effectively stock.
 


86Gram

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Yeah, I know that the cap is to use for noise and I also thought it would hinder performance but my question is about the size of the exhaust. What I was seeing on other websites is that two and a half inch is too large for my Civic. So if that is true and too much flow would decrease horsepower, would somehow making more restrictions help ? And would it be possible to somehow make more restriction?
 

nd4sped

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The size is fine. The butt dyno is not always the best dynamometer. I/H/E (intake/header/exhaust) is the most typical first steps and sometimes the most disappointing power to dollar ratio there is.

Generally enlarging the exhuast can reduce max RPM power output. You may see mid-torque gains but generally torque is the factor that tends to drop on the stock D series and B series engines with bolt on exhaust systems. Now once you get a set of camshafts and a tune you will find that lost power.
 


86Gram

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Hey thanks for your help. What would be the approximate cost of doing cams? And the approximate cost of a turn over? Would I see I noticeable increase if I just did a tune over only?
And how would I find a shop that would do a turnover? When I search online for a shop, I can't find any..
 

nd4sped

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Whats the goal? Also you cant just take your car to any shop and have them "tune" the ECU. The 2003 D17's, I dont recall if that was much aftermarket ECU support. Firs you need to see if a reflash or a complete tune of your ECU is even an option.

You can try looking into Hondata and what options they offer for your platform. I would highly recommend you do more research before throwing money at it.
 


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