Toyota Corolla AE101 GTZ Levin Buildup

3SGTE Throttlebody Conversion

As you may be aware, one of the most restrictive sections of the 4AGZE intake is the throttlebody. At only 50mm in diameter, it is quite smaller than 3SGTE throttlebody's 55mm diameter. The rest of the intake system is about 55mm or so, so I decided it would be a good idea to have a go at installing the 3SGTE throttlebody on my car, especially seeing as I can retain ECU idle control, something the 4AGE throttle body didn't allow.

You can see the difference here. The 4AGZE throttlebody is on the left, and a 4AGE throttlebody in the middle (same size as a 3SGTE, shown at far right). The difference of 5mm in diameter may seem small, but it equates to a decent 17% increase in area.

This mod should take about a day if you've got everything on hand.

Parts you will need to complete this mod:

• 3SGTE throttlebody (Make sure it's 55mm, the later 60mm ones won't fit. 55mm 3SGE ones should work too, email me if you find it doesn't :) )
• Gasket sheet
• 1/2 meter of 5/16 (8mm) inside diameter hose for coolant lines
• 1/2 meter of vac hose for power steering
• 2x short amd 2x long bolts for 3SGTE throttlebody with washers (M8 bolts, measure the depth of the holes and add 10mm or so).
• 2.5" rubber or silicone 90deg elbow
• 2.5" duct or pipe for intake, or adapter or whatever.

Tools you will need:

• Pliers
• Phillips & Slotted screwdrivers
• Die grinder/Dremel/etc
• Stanley Blade
• Socket set
• Feeler Gauges
• Hammer
• Scissors
• Multimeter
• Small files ('Rat-Tail')
• Araldite (The 5 minute stuff)

Step 01

*** I'll be reusing some of the photos from the 4AGE throttle body install, the steps are the same, I'll note if anything is substantially different. ***

First thing is to remove the intake piping, original throttlebody and the alloy J-pipe that runs from the throttlebody to the supercharger.
Now, using the gasket from the 3SGTE throttlebody as a guide, trace the size of the hole onto the J-pipe opening where the new throttlebody will sit. Remove the 2 studs as you won't need them anymore. I was able to easily remove them with my pliers.
Take your die grinder/Dremel/whatever you've got, and grind out all the metal to the line until you have a smooth transition to the new throttlebody. Using WD-40 or Inox etc. will help with the removal of alloy if you're using a grinding stone.
You will also have to grind a little off the side of the J-pipe to clear the bracket for the throttle cable. Line up the throttlebody on the J-pipe and you'll see where it has to be taken from.

You can see where the metal was taken from in the pictures above. If you take a little too much, it doesn't really matter. You just don't want the air to be hitting a ledge.

Step 02

Now it's time to modify the throttlebody.

First of all, remove both the TPS sensors from the throttle bodies. Now take the one from the 4AGZE TB, and put it on the 3SGTE TB, but turn it around.
What you need to do is make sure that the TPS has been turned by 180deg. By feeling how much deflection the tabs make when it's in its stock location and copying that to the new location you should be able to get it pretty close. Don't worry about it being a little out, we'll adjust it perfectly in a sec.
Now, remove the throttle cable bracket from the 4AGZE throttlebody and swap it with the one on the 3SGTE throttle body.

You should now have something that looks like this.. (This is a 4AGE TB, but the TPS sesor needs to be facing up like this).

If you try to install the 3SGTE throttle body now, you may find that some of the vacuum line fittings foul on the intake piping from the intercooler.
That big fat pipe that is sticking out the side of the TB is for the cold start. Use a Torx bit to loosen off the screw and orient it wherever you need it. I pointed it straight down and put a crank case breather filter on. Best idea would probably to plumb it back into the intake before the throttle body.
There is also a smaller pipe that sticks up, I removed it and plugged it up, it's not needed.
Now, if you look at the underside of the throttlebody, you'll see a rectangular slot. This is for the air bypass. If we install it as it is, the gasket will block the air and it won't work...
What we need to do is grind it out so there is a passage for the air. If you look at the second pic below, you'll see what I mean. I used my dremel and some 'rat-tail' files to do this. Remove as much metal as the port is wide, so it's the same cross sectional area.
Now we need some araldite. In the pic below right, you can see a round hole recessed in a V shaped cutout at the bottom right of the butterfly. If you follow this, find the end and mask it off. Now fill it with Araldite. Use a paperclip to push it in and remove air bubbles.
There is another one to block too. See that little bent pipe just near the throttle linkage, pull it out with some pliers and do the same with the Araldite and let it dry (I use 5 minute epoxy so I don't have to wait :) ).
One last thing, the rubber adapter for the intake pipe. If you are using the stock 4AGZE intake pipe, it may bolt up. If so, make a gasket and you;re done here. If not, I filed out the inside to make it smooth (I filleted the edges) and slipped my 2 1/4" silicone bend over the lot. It's not ideal, but I'm getting a metal adapter made up. I'll include the dimensioned drawings below.
Once it's all done, you should have something resembling the pics below.

Intake adapter for the 4AGZE to 3SGTE throttle body conversion - pdf - 16Kb

This will print out at 1:1 scale on A4 paper.

Step 04

The next thing to do is clean out the cold start valve.

Unscrew the screws holding it to the side of the throttlebody and remove the valve. Clean the old gasket off and remove the old O-ring. Give the whole thing a thorough clean.
Now take some sealant (I use sensor safe stuff out of habit) and reseal the valve back onto the throttle body. Only use just enough to do the job, I test fit and have a look to make sure there is even coverage with no 'squish out' just to be sure.

Step 04

Time to adjust the TPS..

Make sure you have the TPS connector disconnected, and oriented as the pic above.
Insert a feeler gauge between the throttle stop screw and stop lever.
Using the multimeter, measure the resistances between the pins in the TPS as per the table in the pictures below.

Step 04

Now to fit the throttlebody.

Reinstall the J-pipe to the supercharger. Make sure you reinstall all the hoses and vac lines correctly.
Put the throttlebody in place and use the new M8 bolts plus washers to secure it to the J-pipe. Don't forget the gasket. Use the one to suit the 3SGTE throttlebody, otherwise you'll have to cut the hole in the 4AGZE gasket bigger to suit or make a new one.

You will find that there are two coolant lines going to the 4AGZE throttle body. The 3SGTE TB doesn't use these (the idle is soley controlled by the ECU). Just loop a bit of hose from one coolant line to the other to bypass the TB.

Now for the power steering lines. There is no provision for them on the 3SGTE throttle body either, so just loop a bit of hose from one port on the steering rack to the other.

Connect the throttle cable to the bracket and test for correct operation. You'll notice that the bracket is offset slightly from the cable. All you have to do to fix this, is slightly bent the bracket that holds the cable towards the throttlebody, and slightly bend out the groove that the cable runs in on the bracket on the throttlebody.
Adjust as required to achieve smooth operation and full throttle.

The PCV line is where an oil catch can goes if installed, so now would be a good time to install one.

Step 05

Adjusting Idle.

Now, here's the tricky bit. To make the 4AGZE Idle Control plug fit, you have to break off a bit of plastic from the Idle Control Motor on the 3SGTE throttle Body. Try to plug it in and you'll see. Just use some pliers to remove it.
Once it's plugged in and everything is connected, start the engine. Take note of what the idle speed does (give it a few minutes to be sure of what it does).
If the idle speed starts high and drops off as the engine warms up, it's all good.
If the idle speed starts low and increases as the engine warms up, the idle control motor is operating backwards. In this case, what you need to do is swap the two outer wires at the plug around (the middle one doesn't get touched). Just snip them with enough length to work with, swap them, solder them and heatshrink.
Now test again, it should all work fine.

Setting idle speed his is a lot easier to do with the 3SGTE throttle body than with the 4AGE TB swap. You'll see a screw from the top of the throttle body, when the engine is warm you can play with this, also the stop on the throttle can be adjusted to suit.

Step 06

Test Drive.

Now for the fun bit... :)
Take it for a test drive and see how it goes. If you have a boost gauge, monitor it for leaks. Rectify any problems and you're done.