Installing a Thrasher Cold Air Induction System

We have completed the removal of the factory air box.  Now it's time to install the CAI kit.

	The following two steps are optional.  This is where the kit really doesn't work in the Impala. Insert a clip nut into the grommet hole farthest back.
	Attach a L-bracket to the nut using a 1/4" bolt.  Install it with the long tab pointing up and facing the back of the car.
	Place the large black cushion on the shelf that the old PCM housing was attached to.  The cushion has an adhesive backing that will hold it in place.  Make sure you clean off the surface first.  Place the PCM on it.  The harness will be stiff and you might not think it will fit.  It will.
	Place the aluminum PCM cover over the PCM.  The cover is sharp so be careful.  I was concerned about it cutting the harness so I sanded all the edges with sandpaper then covered them with electrical tape. Here is why I said two of the above steps were optional.  In the Thrasher instructions, you are supposed to put another clip nut on the L-bracket and attach secure the PCM cover to it.  The PCM harness is too short and I couldn't get the PCM located where I could line up the holes.  I will go back in a few days and see if I can get it to move.
	Test fit the lower air box into place.  You will have to relocate the transmission cable a bit.
	The left side of the lower air box may come in contact with the A/C line.  See if you can push the lines out of the way.  Thrasher includes a length of fuel hose, split down one side, that you can use to cover parts of the line that looks like it will come in contact with the box.  I didn't think it would touch, but I used the hose to protect the closest line and used tie-straps to hold it in place.  Remove the lower air box when you are satisfied.
	Remove the metal duct clamp from the factory duct and install it on the Thrasher one.  Thrasher says that the clamp will fit under the molded tabs in their duct which will help keep the clamp in place.  They must have been referring to a different clamp because mine didn't match up.  It did fit in the groove and I recommend that you tighten it down so it seats nicely.  Attach the duct to the throttle body.
	Replace the lower air box.  Whoops, the duct and the hole in the air box do not line up.  Ok, so the kit is not perfect.  Rotate the duct until it lines up best it can and insert the aluminum air tube into the duct throught the hole in the air box. Remember how the IAT sensor holes in the two ducts were not in the same place?  This is where is gets tricky.  You will need to rotate the duct until the hole is pointing more or less up.  If you don't, then you will not be able to install the IAT sensor and electrical connector (which you should do now).  Of course, by doing this, the duct and hole in the air box will not line up again.  But since the aluminum tube is in place, it will force the alignment. Once you have everything in place, remove the aluminum tube and the lower air box.  In the kit you will find a large square of sticky back velcro.  Peel the protective film off one side of the velcro and stick the velcro to the top of the PCM cover.  With both pieces of velcro still stuck to one another, peel the film off the other side.  Replace the lower air box and aluminum tube and move everything around until it fits.  Once you are happy, push down on the lower air box so it sticks to the velcro that is between it and the PCM cover.  This way you don't have to worry about how to align the two pieces. Tighten the clamp around the aluminum air pipe.  How tight do you make it?  Tighten the clamp a little then try and rotate the air pipe.  If you can rotate it, tighten the clamp a little more and test again.  If it doesn't move, it's tight enough.
	The inner surface of the air filter flange has a lip on it.  The aluminum tube will not go past this point.  I point this out so you know where to place the clamp.
	Slip the filter on and tighten the hose clamp.  Do the same test as mentioned above to ensure a tight fit. Install the clear cover.  If you are happy with the fit, clean the cover and use the pieces of stick back velcro to secure the cover.  Then reinstall the fender brace.
	Check all around the box.  I noticed that the lower left corner of the cover touched the radiator hose.  Any contact will eventually lead to wear and eventual failure.
	I trimmed off the corner with a hack saw and cleaned it up with a file.
	Here is what it looks like when the installation is completed.
	Side view.

When I fired up the car, I heard the slight whistling sound that others have mentioned.  However when you rev the engine, it goes away and you can really hear the air being sucked into the engine and the familiar "whoop" sound of a V- engine rang in my ears.  When it hit 4000 RPM, the engine started to oscillate and wouldn't let the RPM go any higher.  I got worried but I took the car on the freeway and it pulled all the way through 6000.  I think it was the rev limiter kicking in.  I have to do more research on that.



Based on a subjective evaluation, I am really happy with the result.  My other cars have been 350 ci V-8 RWD monsters.  Moving to a FWD V-6 was a big step down in my eyes.  The price I pay for settling down and having a family.  While I was happy with the Impala, deep down I missed the sound of a V-8 engine.  Before, I couldn't tell that there was a V-6 engine under the hood.  Now I can hear it!  I could do without the whistling though.  I stomped on the gas and the wheels spun until traction control kicked in.  Even then the wheels were still spinning a bit.  I don't think I have ever been able to do that before other than when the road was wet.

I need to get some test equipment so I can get some objective numbers.  I got a couple of thermometers and took under-hood and air intake temperature readings using the stock air box.  I need to repeat that with the Thrasher unit.  Some day I will get a G-Tech and get some real comparisons.

Thrasher also sells an Intake Air Temperature (IAT) sensor extension harness.  The IAT is mounted in the rubber duct connecting the air box with the throttle body.  The purpose of the harness is to relocate the IAT to the new airbox where the air is cooler.  If I understand the theory behind it, if the engine thinks the air is cooler, then it will enrich the air/fuel mix.  Cooler air is more dense so more fuel is needed to maintain the correct ratio.  My thought was that the computer's programming was based on the air temperature in the duct since that is where they put the sensor.  If I move the sensor, then it would be providing a false reading.  The resulting fuel mix may turn out to be too rich and cause all sorts of problems later down the line.  However the extension harness would have come in handy so I could turn the duct back to where it fit nicely.

Someone had mentioned that after doing a mod like this, you should disconnect the battery for a few hours.  The car "learns" how you drive and by disconnecting the battery for a while, you reset it.  I forget who told me that and I don't know how true it is, but I figure it can't hurt.  I'll reconnect the battery tomorrow morning and see how it goes.


Go back to part 1.