(Click For Larger Image)
By Matt Beazer
For some time, people believed that bigger than a
stock 52mm throttlebody from a automatic
car didn't get much of a gain, if any. Finally, Sport
Compact Car did some Neon articles, and found a 56mm unit added
5hp over a stocker on an SOHC, and a good gain from 2500rpm-on.
The difference was that they ported the throttlebody opening in the
intake manifold to match the throttlebody opening.
So, I
ordered my unit from Modern Performance. I sent in a core, so
it only cost me a hundred bucks.
Bored Throttlebody from someplace like Howell Automotive or Modern Performance.
Common Tools (6" extension, 13mm, 15mm sockets as I recall). You'll also need a Torx bit to remove the sensors.
Dremel tool with a sanding roll or similar. If you're the old fashioned type, you could probably do it with a round file or sandpaper if you want to take the time.
Shop vac or other vacuum with a "Wand" attachment and a clean shop towel.
Bear with me, it's been a few months since I did this,
so if something is a bit different than what I say, forgive
me!
First off, here's a picture of the stock vs. bored
throttlebodies:
(Click
For Larger Image)
As you can see, there is a
big difference. The one on the left is a stock manual
transmission model, with a 52mm throttle plate with an odd
venturi.
This is to reduce flow at low throttle openings to make the car less
"jumpy" in traffic. It also hurts flow at wider
throttle openings.
If you're sending in a core, DO NOT
SEND IT WITH THE SENSORS ATTACHED. I did this not
thinking, and it came back minus sensors, so I had to pull 'em off my
old throttlebody and lost the spares. Thank you Modern
Performance!
This is based on my experience with my MTX car.
If you have an auto, you'll also have to deal with the
kick down cables.
Installation
First
step, remove the tube that runs from the throttle body to the
air box or remove your cold air intake if you have one.
If you don't, I suggest you get one to get the full benefits of this
modification. I have the common "Iceman" air intake
myself.
Next you need to unbolt the stock throttlebody.
To do this, remove the plastic cover from the throttle body arm, then
use your fingers to pull it to wide open throttle. Thread the
gas pedal cable end out through the provided notch. If you have
cruise, do the same with that cable end.
Pull off the vacuum
line hoses that connect to the throttle body, and any others that may
be in the way, noting carefully which line goes where. Also
disconnect the TPS and AIS leads.
Unbolt the two 13mm or 14mm
bolts (as I recall at least) that hold it to the intake manifold.
You'll also have to unbolt it from the aluminum bracket on the side,
as I recall it's a couple of 10mm bolts. You may have to remove
the battery to easily get to these, however. I had to, though I
have the Iceman battery tray.
Lift the throttlebody clear
gently, in case you missed some small connection. You should be
able to look down the throat of the intake manifold. You'll see
it's rather gunky in there. Say "thanks" to the EGR
system for this boon of carbon buildup. My ported head will
have this corked at the head itself when I tap it, keeping stock
appearance while keeping the nasty crud out. As I recall, my MP
PCM disables EGR anyway, or at least, when I went to emissions it
said "EGR not ready" and I still passed fine!
Take
the stock throttlebody back to your workbench. The AIS and TPS
are held in by a couple torx head bolts
each. Did I ever mention I
Stupid things always strip even if you have the right bit.
These are some odd size I didn't have a bit for at the time. I
ended up messing up the heads trying to work with the wrong tools
(always a bad idea) since I was pissed at Modern Performance for not
giving my sensors back, and I already had the damn thing off and
didn't want to put it back on! I got the AIS out fine, but got
stumped at the TPS.
So, I resulted to some of my favorite
power tools. First I tried to slice
the head off of the torx heads using a cutting disc on my dremel.
This didn't work, it barely made a dent and
shredded the multiple discs I used.
Next I tried to
drill out the bolts. I went through three
drill bits trying, and still failed to get the last one
out.
At this point I realized I was dealing with some kind of Mopar
Super Alloy (tm)!
Finally, out came
the Sawzall. Yes, the Sawzall!
If you don't own one of these suckers or don't have a friend who owns
one, I suggest buying one. It will save you much time and
effort in destroying car parts! I sliced through the aluminum
easily behind the sensor, but then I hit the super-alloy bolt and
progress stalled. I kept going anyway. The blade started
smoking. I kept going. Finally, I was through!
VICTORY WAS MINE! Er, um, I mean, I got it out. The
Sawzall blade was, well, toast. Oh well. The TPS was a
little mangled, but I used some torx bolts from an old 2.2/2.5L Turbo
throttlebody that used a half normal size torx bit. Of course,
this was fun since some bastard had used blue loctite
on the bolts for some stupid reason.
Finally I got it all
assembled. I hope you had more fun than me. If you don't
have the right tool for the job, take the thing with you and go to a
tool store and buy the proper bit.
Next up comes some dremel fun. If you don't
have a dremel, it's a fun tool, go get one. If you're el cheapo
like I can be sometimes, you could in theory use a round file and
some time. If you have a dremel, I'd suggest a sanding roll, I
used 80 grit, but it doesn't much matter what you use, though.
First
off, stuff a clean shop rag down the throttle body hole in the intake
manifold. Don't shove too far, if you lose it you'll have fun
getting it out. Just pack it in so the shavings have no place
to go.
Take your dremel and shave the plastic to the
far edge of the rim that holds the rubber gasket. Don't go too
far, I'd also recommend not cutting too far into the
separator between the main "circle" and the AIS
passage. Fit the throttlebody loosely in place to be sure that
you don't have any plastic blocking the smooth bore of the
throttlebody, if there is, keep going. It doesn't take much
pressure, just brush it around in slow circles to keep the hole
even. When done, it should look something like this:
(Click
For Larger Images)
You can also see in these pictures where the two
10mm bolts that go into the side of the throttle body go, in the
aluminum bracket. The EGR tube is below that.
When
you're doing, use a shop vac or similar to carefully suck out the
particles. Don't get close enough to suck up the rag.
When you've got as much out as possible, pull the rag out and use the
vacuum again to suck around inside the intake manifold as far as you
can reach. This will keep any plastic gunk from going into the
motor.
Bolt back up in reverse order. Position the
throttlebody as central to the hole in the intake manifold as
possible. It shouldn't matter much, but the extra 30 seconds
won't hurt. Make sure you reconnect all vacuum lines, wires,
etc. Replace the battery if you took it out. If you
didn't, you might want to disconnect and reconnect it to reset the
PCM, or pull the proper fuse from the distribution block if you don't
want to reset your radio presets, etc.
Start it up, listen for
any vacuum leaks, and take it for a test drive.
Last modified:
09/08/03
