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Throttle Body Swap 
2G Eclipse Turbo 4G63 to 1G Eclipse Turbo 4G63

The second generation Eclipse Turbo ('95-'99) comes with a smaller throttle body (TB) than on the earlier Eclipse Turbo. The 1G Eclipse Turbo ('91-'94) came with a 60mm TB plate, while the 2G Eclipse Turbo TB plate is 52mm in diameter. The TB on the 2G Turbo can be swapped for the larger 60 mm 1G Turbo TB with a minimum of modifications.

1G Manifold
2G Manifold


1G Throttle Body


2G Throttle Body



You will reuse the 2G  4 wire Throttle Position Sensor on the 1G TB. Follow the instructions in the repair manual for adjusting it. If you do not have access to a manual, mark its' position as best you can before you remove it. The 1G TB has a switch with a single connector on the throttle stop adjuster, this will now be unused and can be removed.

These same instructions for opening up the intake manifold flange apply if you are  installing a larger modified TB. A 2G TB may be ported out to 58mm for about $250.

Prices for the 1G TB range from free (from a friend) to $100-$200 at a wrecking yard. Sorry, we don't have any.

Parts needed:



Remove the TB and place the new larger gasket on the manifold so that you can mark the manifold opening. The hole needs to be opened from 52 mm to 60 mm.



Stuff the opening with rags and seal it as best as you can. Keep in mind the consequences of sucking them or aluminum shavings into the motor. 

Another tip is to tape up the rags with duct tape so you don't wrap the rags around the dremel bit. If you double some tape front-to-front, it can also catch some of the shavings on the sticky side.



Use a Dremel-type porting tool to open up the opening, using the larger 1G gasket as a guide. It is best to use a shop vacuum to help suck up the shavings as you are cutting.



Clean up as much as possible before you begin to remove the rags from the manifold.



Again, after the rags have been removed, carefully clean ALL the aluminum chips from the manifold.



The three straight vacuum fittings are marked the same as the 2G fittings. The fourth angled one will be unused, cap it off.



One at a time, remove the old short vacuum lines and replace them with longer ones. 

If you are still running with your EGR, the following will be necessary for proper EGR 
It's simple, cap off the E line as well as the angled line (marked A1 or something). Then with a T, split the P line to go to where P and E used to go. 

In effect drive the E line, (EGR) with the source from P. 

The problem is that the 1G EGR and the 2G EGR are sourced differently inside the throttle body. The 2G EGR has vacuum at idle but the 1G does not. 


Closed TP Switch and TP Sensor Adjustment [2G] 

1. Disconnect the connector of the TPS. 
2. Connect ohm meter between terminals 3 and 4. 
3. Insert a feeler gauge with thickness 0.45mm (.0177 in.) between the throttle stop and the throttle lever. 
[Fold a piece of paper in half 4 times if you don't have the feeler -Ed.] 
4. Loosen the TPS mounting bolts. Turn the TPS all the way counter 
5. Check for continuity in this condition. 
6. Slowly turn the TPS clockwise until the point where continuity and 
non-continuity is found (pins 3 and 4).  
7. Tighten the TPS mounting bolts. 
8. Check the voltage between pins 2 and 4 of the TPS with the ignition 
switch on, but the engine not started. 
9. Standard value: 400 - 1000 mV 
10. Remove the feeler gauge. 


Port out the Throttle Body Elbow at the flange where it bolts to the TB. At the same time you should smooth out the sharp edge inside the elbow. Don't get too greedy in porting the elbow, it is very thin. Check for vacuum leaks and be sure you are getting full throttle actuation when you push the gas pedal all the way to the floor.


Thanks to Stephan Probst for additional text forTPS adjustment and EGR vacuum line info.


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Last Updated 4/04

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