One the biggest bang for buck bolt-on you can get is a throttle body upgrade. If you think about it, it makes sense. The TB is the biggest restriction in your intake path, as it is itself a variable restrictor... as that is its purpose.
It is sheer luck, and pure Honda style, that a 06+ TSX TB is a straight bolt on upgrade. Actually its my sheer bad luck that this is my second time writing this! The first time low and behold the mighty save button froze... and I lost everything. Since I am done smashing my keyboard... I shall continue.
This is my TB as it arrived:
Note the "Default Thottle Valve Position" (quotes to be explained later) is open a fair ways allowing the light around it. We will come more to that "set screw" later.
According to some basic math the area of a circle is Pi-R-Squared. If we punch in the numbers a 64mm TB gives us a 13.8ish% increase in two dimesional surface area over the stock 60mm TB. Given this and the fact that the TB came from a 2.4L engine... were gonna have to adjust that default position set screw at some point.
First lets remove the old TB:
1) Disconnect negative terminal of the battery.
2) Disconnect the two wire clips on the TB holding MAP sensor and DBW lines to the TB.
3) Remove as much of your intake as you need to, to get access to the TB. I had to remove just my silicone connector on my Injen CAI.
4) Remove the DBW connector.
5) Remove the two coolant hoses from the bottom of the TB and connect them together. Your must plug them or connect them together or they will leak... alot.
6) Remove the two bolts and two nuts holding the TB onto the IM.
7) Slide off stock TB and compare (stock left, TSX right):
I measured 64.5mm on the output side of my TSX TB, and 67mm on the input side.
The stock TB measured 60mm on the output side and 63mm and on the input.
The stock IM measured 64mm:
Well... thats a 60 and 4 dashs anyways, not that you can read it. Sorry for Iphone pics!
Now there is a 0.5mm difference between the IM and the TSX TB. It doesnt matter. Why? Because the 64.5mm TSX TB has a massive throttle plate running through it... even at WOT. Skipping the math... this eats up a whole lot more surface area then a 0.5mm ring around a 64mm circle. The TSX TB will still be your greatest restriction. So don't waste your time dremeling...
Now lets say you have a 06+ Civic Si P2R kit...
Dont worry it fits fine. The gaskets measured 64mm... and the P2R spacer itself measured 65mm:
You can see the 0.5mm ring from the difference of the 65mm P2R spacer to 64.5mm TSX ouput.
And here is the spacer on the stock TB:
You have about 4.5mm extra space there.
One thing to note is that I obtained about 85% heat blockage (as measured with laser temp gun) with the teflon gaskets alone... in the P2r Kit. So I didn't install the spacer, as I wanted the stock look, and I didnt want to have to deal with the spacer move the intake back.
Now that you know everything is going to work... You can start reinstalling it. The reverse of removal above. Since this is my second time writing this I am not going to write it all backwards again I will add however, that it took me an HOUR to CLEAN the TB from the wrecker... and another hour to remove all the old gasket material with a razor. Important to get that clean and smooth before install.
Don't forget to strech your intake boot to make everything fit, it will be a tight squeeze over the new 64mm TB. I had to use the butt end (not the business end) of a small propane tank. Seemed to work good (do not try at home).
Now... after you install this thing.. and get it running there is a problem.
I have NEVER had rev hang on my car. People complained about it, I never had it from day one. After this install I had BAD rev hang. BAD and a rough (ish) idle.
If you think back to the 13.8% increase... and the light around the TB ring, you know that the default position of the TB requires adjustment.
Now... as of today and my knowledge while writing this article, this is not a straight forward adjustment. Our ECU is complicated. It does things that I sometimes don't comprehend so my adjustment procedure may change.
Skipping the math, logic would state give the set screw (hidden, circled) 1 to 2 turns to the left and it will close the TB a bit, and were good. (I tested the before install).
This is NOT the case.
It appears when the car is moving forward... and you are not on the gas the TB uses the default position to BASE (being the keyword) a cruising idle off of. It does NOT return to the default position, it simply uses that position to BASE a cruising idle off of. The cruising idle is an idle obtained above 5mph, with foot off the gas.
How do I know? Well at first I removed the DBW cables, started the car and adjusted the RPM down to 700 ish and the reconnected everything, and it jumped back up to 850 (my idle point). BUT EVERYTHING WAS WORSE, rev hang etc. CEL. This did not make sense. Left is close... right is open, as verified. So if I closed the TB how could it be worse? After all it was bigger, it needed to be closed.
I also noticed after doing this, the "cruise idle" (valid from 5mph+) was 1200 RPM. Now when I stopped and undid my changes by turning the set screw to to the right a turn, the "cruise idle" dropped to 1100 RPM. Of course my idle, while stopped, during this adjustment, stayed at 850 RPM which is MY TUNE set point.
This means that the "Default Throttle Valve Position" is only just that, the ECU can actually close the TB further then default if it wants to. Hmmmmm. Complicated.
So this is what I did:
I adjusted my set screw with a 2.5mm hex key a half turn at a time, going for runs in between with the car running and warmed up. I was looking for the BEST or LEAST rev hang and a low cruising idle of 950-1000 RPM. In my case I was turning to the right. With the DBW connected undone I would idle 1200 ish, connected it would close the TB to 850 ish. So when I turned the screw, (DBW connected of course) the idle would not change as the ECU regulated it instantly.
So I had to go for a drive between half turns to see the cruising idle... (1000ish). I started at 1200ish... RPM and after adjustment came down to 1000ish.
THIS SOLVED REV HANG for me. Yes, it actually removed it near completely, back to the way I was before. This is a senitive adjustment and at first that screw is TIGHT. VERY TIGHT. ALMOST STRIP TIGHT. Be sure to do this when its warmed up, it will turn easier, and use a 2.5mm key, nothing else or you will strip it!
Honda Techs can step in here, what is the adjustment procedure? This is what worked for me.
That aside, I made a 13.8% adjustment to my low RPM throttle tables and phased it out to no adjustment by 6000 RPM. This gives the bottom end a stock Type R feel, as I already had Type R mapping, this TSX TB made it really too sensitive.
I also made a 1% increase adjustment to my coldstart fuleing Low V-Tec values as now I am flowing more air, and you could feel the car more inclined to "buck" when cold as the TB was bigger and more easily overwhelmed a cold engine with air. This helped alot.
Good luck with your install. I will edit this post with update set screw information as I find it. I threw quite a few P0168 error codes at first (Default Throttle Valve Position Incorrect). Now things are looking good.
Now... At the end of day... what did we gain?
Map Pressure... as graphed comparing old to new. More is better! Big gains from 7000 RPM up. Butt dyno agrees!