ASC

OK, so you got rid of the throttle cable slack, installed a CAI and said "wow, this car really came alive!" Well, here's one more thing I did yesterday that really did help the throttle tip-in and smooth the overall power curve: Knife-edge the throttle plate and grind down/level the two screws that hold the throttle plate to the center shaft.

Sorry I don't have pictures, but I do have a link to a similar DIY for a Honda. The overall process is not hard, but you do have to be careful: this is not for the faint of heart, nor those with a wobbly hand. BTW, here's the link for the Honda DIY:

http://www.redlineam.com/forum/showt...ght=knife+edge

For our cars, you'll need the following tools and parts:

12mm socket and extension (for the throttle body/intake manifold bolts)
10mm socket and extension (for the airbox bottom half)
pliers (for the coolant hose clips on the throttle body)
shop towels (to wipe up any possible coolant drips)
Dremel with grinding bits (to level the screw tips, knife-edge the plate)
File to clean up the rough grinds made by the Dremel
Really fine sandpaper to polish the plate after knife-edging

two (2) M3x5mm screws (to replace the one's that will shear off)

For the actual knife-edging, I'll refer you to the above link. In the meantime, here's the rundown to get to the actual knife-edging:

1) Remove the airbox and associated tubes/hoses, and disconnect the two electrical connectors if you have a stock system. To remove the lower part of the airbox, you'll need to unscrew three 10mm bolts.

2) Once the entire airbox assembly is out, unplug the two electrical connectors on the throttle body (one is for the Idle Speed Control, the other is the Intake Air Temp Sensor)

3) Rotate the throttle rotor clockwise about 90 degrees. This should give you enough slack to remove the throttle cable from the rotor.

4) With the 12mm socket and extension, remove the two nuts and one bolt holding the throttle body to the intake manifold.

5) Gently pull away the throttle cable bracket, then the throttle body from the manifold. Notice the two coolant hoses clipped onto the throttle body.

6) Using the pliers, slide the two clips away from the throttle body. Making sure the hoses are pointing upwards, gently pull them off. As long as you don't point the tubes downward, and the engine is cold, almost no coolant should flow out.

7) Now comes the heart-stopping part. The two screws holding the throttle plate on are M3 metric screws that have been glued in such a way that unscrewing them will cause them to shear. I don't think there's any way around this, the screws have a tiny threaded shaft. I sheared off both of 'em, and broke out my drill with a 1mm titanium bit.

8 ) Here's where the steady hand comes in: CAREFULLY (and slowly!), drill out the remainder of the screws. You MUST stay on center or you'll flatten the threads. Once the holes are clear, breathe a sigh of relief. The hardest part is done.

9) Turn the throttle rotor 90 degrees to slide out the throttle plate. From here, please refer to the link I posted above for the instructions on which edges/sides to bevel/knife-edge, as well as how to flatten the center bar. The assembly is the exact reverse of the steps above. Just remember to use a drop or two of Blue Loctite on the throttle plate screws for the "just in case" factor.

This really did make a "zippy" difference in my xA. We have small motors, so anything that can make them breathe better and more efficiently has got to be a plus. This is NOT a horsepower maker, simply a way to get better throttle response. I've done this to most of my previous cars with great success. It shouldn't change your gas mileage, either. As far as the science behind it, searching Google for "knife edge"+"throttle plate" will get you plenty of information.

Good luck!

Al

superfreestyle

dont know about this one...

apexjr

I think it might be easier to just get a bigger TB. =)

ASC

It might be easier, but the intake manifold mating surface would need to be enlarged as well. This cost less than $1.00 and about 1.5 hours of my time.

BTW, the opening on the intake manifold is half-filled with a grid of some sort, most probably to straighten the airflow in a similar way to the screen in the tube just before the MAF.

Fushyuguru

This is always a good mod, and these style throttle plates are commonplace on very expensive ITB's.

I'll be doing similar on my tC soon.

I'ts too bad for us, Scion threw some epoxy on the screws but I prefer this over the riveted domestic TB-plates.

hotbox05

seems like a bit of time for maybe a half horsepower? eh . nah.

Fushyuguru

Theres more to putting together a great tuning package than horsepower.

hotbox05

true but i doubt that this mod changes anything horsepower , throttle response or just about anything.

Rickisan

My question is this... How much for a new throttle body if my hand slips and creates unrepairable damage? LOL

Fushyuguru

You just answered any of your reservations right there. This isn't for you. Throttle bores and plate modifications aren't new. If this is your warrantied grocery getter, you probably won't want to get into the guts if you don't plan on fixing any of your mistakes out of pocket.