Throttle Body Restrictor Plate Removal
I did this modification with the throttle body still attached to the engine. Unfortunately, I did not take any pictures of it at the time. The following pictures are from Gary Westover's install in which he removed the whole throttle body from the engine. The other difference between what I did and what Gary did is that he ground off the restrictor and left in the stock rivets. I had done this on my 97 and had often wished that I had not destroyed the old one. So, on my 2000 I drilled out the rivets and kept the restrictor for reinstallation if need be.
If you do this carefully and ensure that the throttle will stay closed while you are working with the screws, you should not have to worry about dropping the screws into the intake. If you're still not sure, Gary's method is the ultimate safety measure. The first picture in each row shows the "TB off" method while the second one shows the "TB on" method that I used. The "TB off" pics came from Liquid's ZR2 site.
Disconnect your battery before you begin the mod, after an hour or so, hook the battery back up and turn the key to run, wait a few seconds, and start it. This will reset the computer and allow it to recalibrate for the new air flow.
First I removed the intake piece above the throttle body (the tall, black thumb screw). Next I removed the 2 retainer screws that hold the butterfly valve to the rod (Torx head) and put them in a safe place. Then I just opened the throttle, and pushed the plate out if the slot in the rod.
This is the throttle plate after the restrictor was removed. The second picture shows the TB installed with the PowerAid TB spacer (the orange part) in place. In order to remove the restrictor I placed the plate on a solid surface and drilled out the two rivets. While doing this be careful and work slow. If the drill grabs the plate or restrictor it can cause either one to bend or break.
Now that the restrictor is removed, I needed to fill the two holes that were left in the plate. The center hole is a base air bypass hole that is calibrated into the PCM. If the other two are left open, you may confuse the computer. I used two new rivets of the proper size to fill the holes and ground the ends smooth to retain decent air flow.
To reassemble the throttle plate into the throttle body, open the throttle and gently slide the throttle plate down into place. Then gently close the throttle being careful not to score the bore. Open and close it a little a few times to make sure it's centered. Then re-install the retainer screws with a little Loctite. Open and close it and check for binding.
Results: More high RPM power - small, but noticeable. This mod works well with my AirAid and PowerAid TB spacer. It will work even better with my cat back system once I get it on.
2000 ZR2 1997 ZR2 1994 Z28 1989 ZX750R 2000 NHRA Trans Am
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Questions, comments, suggestions? Send mail to: Scott BraemerLast Updated 06 September 2002 12:53
