Honda Civic SiR

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Ford XF Throttle Body Installation

This section contains the installation details of the Ford XF throttle body into my Honda Civic (including photos). The Ford XF throttle body was obtained from a local Ford wrecker. It is from a straight 6 Ford XF Falcon.

Dimensions - Installation Steps - Problems - Results

Dimensions

Below is a table containing a series of dimensions used to compare both the first and second generation B16A Honda throttle bodies and the Type R throttle body with the Ford XF throttle body. The Ford XF throttle body is much larger than any of the stock Honda ones.

Throttle body measurements
Measurement B16A G1 B16A G2 B18C spec.R Ford XF
Opening - Front 62mm ID, 69mm OD n/a n/a 71mm ID, 81mm OD
Opening - Back 59mm 63mm n/a 67.5mm
Butterfly 58mm 60mm 62mm 65mm (68mm available)
Butterfly to back 20.5mm 20.5mm 20.5mm 53mm

Installation Steps

Installing the Ford XF throttle body is by no means an easy task for the Honda intake manifold. If you do want to use a Ford XF throttle body I suggest getting a second intake manifold (preferably the second generation model), because there is a possibility that it could all turn to custard since there is quite a bit of welding and grinding involved if you want to do it properly.

Here are the steps that we went through to install the Ford XF throttle body.

  1. Fill the existing TB mounting holes, and the existing air supply lines to the Idle Air Control Valve (IACV). You'll need to know someone that is competent at welding aluminium for this step.

    Weld filled mounting holes in the second generation B16A intake manifold

  2. Clean up the face of the intake manifold taking care not to mark the face too much. Otherwise you may end up with an air leak between the intake manifold and the throttle body when it is put back together again. 
  3. Line up where the new TB will be mounted, taking care that you will be able to port match the intake manifold without breaching any of the existing cavities. On the second generation intake manifold the right hand side of the original hole was left and all of the material was taken out from the left.
  4. Mark the locations of the mounting holes and where the manifold has to be port matched to.

    Marked locations for the new mounting holes in the second generation B16A intake manifold

  5. Port match the intake manifold and drill and tap the mounting holes. You need to remove a lot of aluminium during the port matching because the back of the Ford XF throttle body is much larger than the stock Honda one.

    Port matched second generation B16A intake manifold

  6. Drill a hole into the back of the intake manifold that will breach the old IACV air supply line. This is not required if you don't mind the car idling low on a cold morning, or when the air conditioning is on. Weld on a spiggot that will be used to connect the air supply line from the existing Ford XF TB arrangement.
  7. Below is a comparison of the port matched second generation intake manifold compared to a first generation intake manifold (the one that is stock standard on the 1990 Honda Civic SiR).

    Comparison of port matched second generation B16A intake manifold with first generation intake manifold

  8. Now you have to drill a hole into the Ford XF throttle body that will be used for the vaccum line that connects to the Honda MAP (Manifold Absolute Pressure) sensor. We drilled a hole through the side of the manifold in the big square bit at the back and epoxied in a stock Honda vacuum line pickup that we pulled out of an old Honda throttle body that was lying around.
  9. The stock Ford XF throttle body contains two large air lines before the throttle body. One of these will be used to supply air to the IACV valve, but the other one is not needed. We just pulled out the brass pickup and got some aluminium rod the same size as the hole and then plugged it up.
  10. Create (or purchase) the gasket for the Ford throttly body and then attach it to the intake manifold. We just made a gasket out of some gasket paper. We also sprayed the intake manifold and throttle body with a high temp ceramic white paint in an attempt to prevent the intake from heating up through the conduction of the underhood air temperature.
  11. The next part was to get the throttle position sensor (TPS) sorted out so that it will register the correct voltage at closed, WOT and every where in between. Upon measuring the resistance of the Ford TPS at both the minimum and maximum rotation angles it was quite different to that of the Honda TPS at both minimum and maximum rotation. To prevent any problems with the TPS and so we could use the stock Honda wiring harness we decided to see if we could make up an adapter so that we could use a standard Honda TPS. The picture below shows the Ford XF TPS next to a chopped up Honda one. 

    Cut apart Honda throttle position sensor (TPS) next to Ford TPS

  12. To make the adapter we needed to remove the bit that contacts the Honda TPS from the end of a Honda butterfly spindle and attach that to the end of the Ford XF butterfly spindle. That bit is attached with a sleeve that slides over the Ford spindle and is secured using the standard split pin that normally turns the Ford TPS. We also needed to fabricate a block that could be attached to the Ford XF throttle body, but allow us to use the Honda TPS. The pictures below show all of the bits for the adapter, and the adapter installed in place on the Ford XF throttle body.

    Honda TPS adapter for the Ford XF throttle body The Honda TPS adpater installed on the Ford XF throttle body

  13. The next step is to make sure that you get full throttle and adjust the butterfly stop if you are not. Note how much bigger the opening of the Ford throttle body is compared to a stock Honda one. Note also the hose that connects the air supply from before the throttle plate to the IACV valve.

    Full throttle check for the Ford XF throttle body

  14. Below are some photos of the finished intake manifold compared to the stock second generation intake manifold and throttle body that used to be on the car.

    Ceramic painted second generation B16A intake manifold with Ford XF throttle body attached Finished intake manifold next to original intake manifold End on view of the finished intake manifold next to original intake manifold

Problems

After installing the new throttle body and intake manifold on the car, we had massive problems trying to get it to idle at anything below 2000rpm. It turns out the the Ford XF throttle body is not machined to similar standards as the stock Honda throttle body. After taking the throttle body off the car and looking at how well the throttle plate seals with the rest of throttle body, it was clear that there was probably enough air getting past it to cause the problem. We also checked the idle bypass screw and that too was letting quite a bit of air past when it was completely closed.

To remedy the problem the Ford XF throttle body was bored out to 66.5mm and had a new throttle plate created to fit the new surface. The throttle bypass screw was also altered so that it actually closes and shuts off (well almost) all of the air.

So, when purchasing a Ford XF throttle body, be sure to check how well the throttle plate shuts. This can be done by looking at the plate with a strong light behind it. Any gaps between the throttle plate and the throttle body will be apparent as light gets past. Also check the idle bypass screw. This is a little harder to do, but can be done by trying to blow through the throttle body when it is closed and feeling for air escaping where the idle bypass exits on the other side of the throttle plate. A bit of moisture on a finger can help detect the air.

Results

With the car now running properly and having dynoed the car, there were some pretty good gains. The car gained 5kW at peak and 10Nm at peak. The torque curve also looks a lot better and is shown in the B16A Dyno Runs section.