Intake Filter Mod
*Applies mainly to 85-86 NA MR2s. 87+ MR2s have
their Intake filter mounted in the trunk. However, if you wish
you can follow this writeup & move the filter into the engine
bay like the 85/6s.
This is a very common modification for the MKI MR2s
and usually the first people do. The stock air filter setup is
quite restrictive to airflow. There are quite a bit of writeups
for this one, but hopefully I can provide you with more detailed
pictures for performing the mod. Things may be slightly different
for newer year MKIs.
Results after doing this include faster revving
& a louder note from the engine above 3000 rpm and this mod
has been dyno'd (not by me and my setup though) and showed about
a 5HP peak increase in the upper rpm band. One thing I did notice,
is that there is a slight buzzing from the intake between 4000-4200
rpm. Nothing to worry about though, it's just resonate frequency
being induced into the system from removing the factory resonator
Here's what you need to do the basics (there are
a few places that sell the entire kit online, particularly Ebay.,
I went the separate purchases route myself):
Total cost is around $50.
1) Here's the stock setup. Begin by removing the air filter & its cover:
2) Remove the snorkle, by removing the 10mm bolt and unclipping
it from behind the battery.
3) Pull the hose pointed to by the green arrow up and out. Unbolt
the 4 10mm bolts (red circles). Remove the yellow & blue circled 10mm
bolts. You need to remove the blue circled bolt for when you pull the air
filter plate and resonator box out.
Here's another bolt that you need to remove:
4) Now all that junk should be out. Next is removing the AFM.
Remove the bracket by undoing the green circled bolt. Remove the AFM wiring
plug in the red box. To do this take a small flat-tip screwdriver to pull
the clip in the direction the yellow arrow is pointing. The plug should then
pull straight out. Loosen the blue circled bolt holding the hose onto the
5) Loosen the bolt (green circle) for the hose clamp holding
the hose to the TPS. Also, remove the AC idle-up line (if you have AC) by
loosening the hose clamp (red circle) with a pair of pliers.
Note: Since you have gone this far in the process, you will
notice a nice coating oily residue inside the throttle body and on the butterfly
valve. If you would like more info and pictures of cleaning out the TB check
out my TB & TPS page.
6) Now here's all the crap that you have just removed and will
not be putting back into the car:
And here's the newer, simpler system that's going in:
1) Place the 2" coupling onto the AFM. This is the toughest
part of the whole process. You will need to work the coupling so that it will
stretch over the AFM. I found that by inserting a pair of pliers and pulling
the handles apart was an easy way to stretch the coupling.
After doing this for a minute or so, putting the coupling on
the AFM was quite easier. Tighten down the hose clamp.
2) If you do not have AC, go to step 3. Now you will need to
tap into the coupling with the fitting that you decided upon. (You could also
tap into the AFM itself to use a screw type fitting, but I do not have the
tools to do this). I used a tiny Phillips screwdriver to start my hole, and
gradually made the hole bigger until it was a real tight fit with the fitting.
Here's the AFM with a purple hose attached to the other end of the fitting.
And here's a view looking into the AFM, you can see the brass
3) Connect the AFM back to the TPS, using the circled hose clamp.
Ignore the bracket pointed to by the red arrow. I put it there to temporarily
support the weight of the AFM
4) Lots of steps here. Connect the AC idle up lines in green
circle (if you have AC), attach the AFM adapter pointed to by red arrow by
four 10mm bolts, fabricate some brackets (I redid this with strong metal,
see the bottom of this page for the new ones), connect the AFM plug (blue
arrow) and the diagnosis plug bracket (blue circle).
5) Finally, attach the filter and tighten the circled hose clamp.
Also, find a place to attach the VSV that the AC idle-up line
isconnected to. Mine is temporarily twist-tied to something else, until I
get a longer piece of silicone hose.
Rainshield & Better Brackets
To make the AFM & Filter alot stiffer, I redid
the brackets from some stiffer aluminum stock pieces.
The first one is attached to the bottom of the decklid release
bracket and to the back side of the AFM:
The other bracket attaches with bolt & nut to a hole, found
under the bracket for the diagnosis plug, and to the AFM adapter plate.
And finally the finished setup with the rainshield made out
of plain old clear plexiglass, cut with a Rotozip and smoothed with a file.
Here's another view. Circled is a piece of green felt, as the
plexiglass contacts the top of the filter. This stopped some vibration and
possibly scratching of the plexiglass.
Here's how I did the brackets for the plex. To remove the plex,
it only takes the removal of the below circled bolt.
The other bracket is just slid over the decklid prop rod rest
pin. This way you don't have to mess with touching the bolts that attach the
brackets to the plex. (In the below picture you can see where the metal bracket
attaches to the AFM adapter plate.)
And here's why you need the rainshield:
Jan 3, 2002
Replaced temporary vacuum hose with a longer piece (about 5")
and remounted VSV properly to where the battery sits.
Also, here's how I have to store the prop rod when the engine
lid is down.