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B18 throttle body swap (D series motor)

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B18 Throttle Body swap on Honda D series motor

Spdweb.net 1999 Honda Civic y7/z6 Mini-Me engine

Goal
To swap the stock 56mm throttle body for a 60mm throttle body from a B18 motor. This doesn't sound like much of a change but it will provide better throttle response and high end performance. This swap will also work with a 62mm Type-R throttle body but 62mm is actually a little 'too' big. Since this motor also is running nitrous the extra air flow will make quite a large difference.  Also no Fast Idle Thermo or IAC to block off YAY!

Getting started
In order to do this install correctly the intake manifold will have to be port matched to the throttle body. This Z6 intake manifold is already slightly larger at 58mm, then the stock throttle body which is 56mm at the base. Using a sanding wheel or grinding wheel carefully widen the intake manifold to about 62mm. Be careful not to egg shape the manifold.

MAP sensor issues
Since this throttle body is from a pre '94 B series motor it uses an external MAP sensor. It is quite easy however to use the throttle body mounted MAP sensor from the D series. Just remove the MAP from the D series throttle body and use a short piece of vacuum tube to hook it to the B series as the images to the right show.

Reusing the gasket
Unless you purchase a B series gasket you will also have to modify the gasket to accommodate the new throttle body. Just trim the edges a bit until it fits.  Most of the time the gasket is damaged when it is removed so just be sure to purchase the B series gasket.

Throttle pulley and cable
I first tried this install using the pulley that came on the B series throttle body but I found this not to be a good choice. The pulley is much bigger and does not allow for fast throttle response. Also the D series cable does not have enough travel to open the gate to 100% WOT (Wide open throttle). I eventually replaced the pulley with the one from the D series throttle body.

Finishing up
Once installed I secured the MAP sensor to the cruse control position on the throttle body just to make it neat looking.  Eventually I will fabricate a aluminum bracket to hold it more securly in place.

Testing
The faster throttle responce is very noticeable although I did find that retuning my ecu will be necessary.  This is because the B series throttle body allows much more air to enter the engine at the same % of throttle.  A quick example would be, the B series allows as much air at 1/4 throttle as the D series did at 3/8, get it?  All-in-all I think this mod is WELL worth it.

If you have any questions feel free to post them in this web sites forum.