Project Civic SI

Project  Civic SI - Intake and Exhaust

By Aaron LaBeau

When it came time to succumb to the modifying bug with the Civic SI (FA5) I realized in modifying cars we are doing something reflective of ourselves.  One of the best parts about modifying a car is making it yours.  If you've been reading our publication for a while you know we favor racecar parts and function over stanced out showcars.  But, there's that line you cross when your street car loses the comfort and convenience in exchange for that performance that makes your car so different from every other one out there.  With this project we're going after that balance between street car and performance and more importantly, the ablity to pass a SMOG check since we live in the people's republic of California.  With these goals in mind, eeking out more performance from our SI will be no easy task with a normally aspirated engine that makes nearly 100hp per liter from the factory.

We're covering the bolt-on basics of helping the engine breathe better by adding a high-flow intake and exhaust.  Transitioning to the Honda world from compact Nissans is weird.  Instead of two or three intakes available for the venerable SR20DE market there are hundreds of choices for the Honda K series of engines.  Though, our choices are drastically narrowed when seeking SMOG legal intakes.   Enter CT-Engineering.

Civic SI Intake

Powder-coated heatshield and high-flow air filter goodness but most important is the CARB E.O. number on the MAF adapter that allows us to SMOG the car.

Civic SI Smog legal part
The Holy Grail in the automotive aftermarket!  CARB E.O. exemption

When you look at the CT-Engineering intake for the Civic SI on the web it frankly doesn't look like much compared to their carbon fiber air-box for the NSX but it doesn't carry the NSX pricetag either.  When the box arrived at my door step it was much larger than I expected, most of the size attributed to the large heat shield.  Short runner intakes for this car are known to get heat soaked, so in this application the heat shield makes a lot of sense.  There are only about two other manufacturers that I've seen with CARB E.O. numbers for their intakes and since we plan on using other CT-Engineering parts down the road, at this point we're going for a all parts designed to work together approach.

Civic SI intake .vs stock CT Engineering
Stock vs. modified with the CT intake; the stock hose shown above is re-used in this application


Howard at Technosquare

Howard at Technosquare is the man!  He didn’t need the instructions but looks much more official with them in his hand.


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Wednesday, July 11, 2012 10:32 PM
Hmmm... very curious to see which resonator you go with...
Thursday, July 12, 2012 6:30 AM
"Howards magic anti-seize"?
Is there a secret recipe?

Another good article.
Thursday, July 12, 2012 7:09 AM
@brian - I'm going to use the same one that CT-Engineering supplies as their mid muffler. Since space is tight it's either something like that or a bottle style resonator. I'm fairly confident that putting the resonator close to the CAT should quiet things down nicely.

@-pk386 - No I just thought it was funny he keeps the anti-sieze in a Merry Christmas can :)
Der Bruce
Der Brucelink
Thursday, July 12, 2012 8:46 AM
I enjoy the Honda stuff Aaron! I'm really looking forward to what you and Church find with the Hondata.....and CARB approved supercharger!? Um yes please! Now I just need to see if the world is gonna offer up some modern CARB approved 1.5L tuning in the Honda community. Although, technically I have no CARB issues here, it's still nice to be '50 state' legal even though most products might be '49 state' legal ;-)

PS What no BTiLC references!?
Thursday, July 12, 2012 11:01 AM
You should try upgrading the intake tube (the part that connects to the throttle body) to the CRV tube.

Also, there are plenty of Si sedan specific exhausts out there that don't need adapters. From what many owners claim, the Invidia Q300 exhaust is one of the quietest exhausts and has a 70mm diameter.

Either way, I'm always excited to see an 8th gen as a project car. I'm looking forward to future installments!
Thursday, July 12, 2012 11:34 AM
so on page 1 you say the CT intake reuses the stock tubes, on page 2 you say the CT intake is required with the SC cause the stock tube will collapse... i thought the stock tube was reused with the CT intake?
Thursday, July 12, 2012 12:51 PM
@ Bruce - Glad you liked it, I needed another story to drum up some chat time with you! As for the BTiLC reference I supposed Howard's anti-sieze could be compared to "Black Blood of the Earth!" or that magic drink they had before fighing Lo Pan but I'd never drink anti-sieze.

@ clutchshiftdrive - I think HPS makes a tube like your describing. Glad you liked the article!

@ warmmilk - Your right I did do that and it is a little contradictory I'm just relating what I've heard from Hondata about the intake tube collapsing under boost. I would guess the metal MAF adapter in the CT intake keeps the tube from collapsing but I haven't seen it first hand like the folks at Hondata have.
Thursday, July 12, 2012 1:28 PM
Didn't I tell you CT was awesome. Here's a direct quote from them. "In regards to a stock rubber intake tube collapsing under boost. It’s really not the tubes fault, the collapse comes from excessive vacuum between the air filter and throttle body. Introducing a free flowing air intake allows enough airflow to fix that."
Thursday, July 12, 2012 4:39 PM
I see the Hondata Flashpro smoothed out the stupid stock torque spike at the VTEC changeover. Looks like you increased the rev limit to 8500rpm too? Nice!
Friday, July 13, 2012 1:58 AM
I'm pleased to see you guys taking on this project. My '07 is still my dedicated daily driver (with an EG for my track duties) but I'd like to see what's possible with this platform. I look forward to seeing the progress!
Dusty Duster
Dusty Dusterlink
Friday, July 13, 2012 5:40 AM
"Modern OBDII cars fight to return the car to factory specifications"

Exactly. Intakes for power gains on NA engines are pointless because of this. I bolted a well-engineered AEM intake onto Project Mustang 5.0 expecting zero power gains; I did it only for increased throttle response. It did increase the throttle response (enough that removing the intake actually made my car feel sluggish to me).

AEM claims 8 additional horsepower from the intake. I call hogwash; 8 horsepower on a car with over 400 could be a rounding error.
Monday, July 16, 2012 8:52 AM
Cool project, looking forward to how it develops! Do you think your mods to the CT Eng exhaust were what caused it to be louder than expected? I'd imagine any change in length from the originally designed CT length would make a difference.
Monday, July 16, 2012 12:01 PM
@ speedball3 - I'm pretty convinced that the extra pipe length for the sedan is what's responsible for the loudness in the exhaust. CT's stuff isn't the cheapest and as such their customers don't have the tolerence for a overly noisy exhaust. Breaking a bit of new ground here for CT I expected some tweaks to get it right. I have an additional resonator hitting my doorstep today from CT Engineering. I may end up experimenting with a helmholtz type resonator (also used in the stock exhaust on the s2000) if it's still not quiet enough. I've done some measurements with a Radio Shack db meter with stock and before modification. Will be interesting to see how much difference a resonator close to the CAT will make. My goal is to get it close to stock for cruising around and respectably loud when stomping on it.
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