Ford XF Throttle Body Swap

For pictures and details of the Ford XF throttle body swap, go to the Ford XF Throttle Body Installation web page.

In the search for more power, a bigger throttle body (TB) was determined to be the next place to investigate given that the intake, headers and exhaust had already been improved. Since I have access to a lathe and other machinery, the first thing I investigated was overboring the standard Honda throttle body.

Upon investigation, the standard second generation B16A throttle body looks like it can only be bored by about 1mm, perhaps 2mm before you breach into the cavity that the throttle position sensor (TPS) lives. Such a small increase in diameter for the amount of other work that is involved just didn't seem worth it. So I decided to investigate the option of swapping in a completely different throttle body. Of course the best place to start looking is in the range of OEM throttle bodies that Honda produces. Unfortunately, the 60mm throttle plate in the second generation B16A TB is the largest size that Honda produces apart from the B18C Type R throttle body, which is only 2mm bigger at 62mm.

For all the potential hassle that could be involved with doing a TB swap, an extra 2mm just didn't seem like enough. Mainly because I don't like doing things in a small way. I figure that if you are going to do a modification, you might as well do it big to get a noticeable change. I started looking at what aftermarket throttle bodies were available to swap in for the standard B16A throttle body and found several:

The Spoon 70mm throttle body (despite its name) in fact only has a 62mm throttle plate. The 70mm refers to the internal measurement at the end of the machined taper intake. The RC Engineering overbored throttle body looks like a first generation B16A throttle body that has been overbored to 64mm. I am not sure how they got around the cavity breach problem underneath the TPS. I suspect they filled in the cavity with weld before overboring, which looks completely feasible (however, the MAP sensor vacuum pick up point may of had to be altered as well). The Erick's Racing throttle body looked fantastic, but it cost way more than that I was willing to pay for one. Also any of these throttle bodies would have to come from overseas, which makes the prices even more ridiculously expensive when you are paying with New Zealand dollars and have to pay US prices.

I remembered reading somewhere that someone had managed to use a throttle body off a Ford Falcon somewhere else in New Zealand (the land of Kiwi ingenuity) to get substantially more air. I did some more research locally and found out that a Ford XF throttle body can be obtained with either a 65mm or 68mm throttle plate. They can also be obtained at a pretty good price at the local Ford parts wrecker. This option seemed to satisfay all my criteria: relatively cheap with a pretty good increase in size. The only downside was that some fabrication may be required, but this didn't really bother me. After all, nothing comes for free. I think that these throttle bodies usually live on a Ford straight 6 engine.

Below is a table comparing the percentage air flow increase for all of the different throttle bodies that I found during my investigation. The air flow increase is based on the approximate difference in cross sectional area at the throttle plate (allowing for the size of the spindle) when compared to the first generation B16A throttle body.

Air flow increase measurements
Model Throttle Plate Size Air Flow Increase
B16A G1 58mm 0% (all comparisons to this)
B16A G2 and G3 60mm 7.6%
B16B 60mm 7.6%
B18C 60mm 7.6%
H22A 60mm 7.6%
B18C Type R 62mm 15.4%
B16B 62mm 15.4%
Spoon 70mm 62mm 15.4%
RC Engineering 64mm 23.5%
Ford XF Falcon 65mm or 68mm 27.6% or 40.5%
Erick's Racing 68-66mm or 70-68mm 40.5% or 49.4%

So, I ended up purchasing a wrecked 65mm Ford XF throttle body. It was harder to find a 68mm throttle body, and the approximate 27% increase in air flow sounded more realistic for the 1600cc engine than the massive 40% you would get with a 68mm TB. Once I had the throttle body I started trying to figure out what fabrication would be required to get it to mate with the Honda intake manifold and various electronic sensors.

Below is a picture comparing the first generation B16A throttle body with the wrecked Ford XF throttle body. The Ford XF throttle body (on the left) is visually much much larger than the stock Honda one. There is also enough aluminium in the Ford throttle body to bore it all the way out to a 70mm throttle plate. Click on the picture to get a larger view of it.

Birds eye view of a Ford XF throttle body next to a first generation Honda B16A throttle body

It ended up being a bit of a mission to install the Ford XF throttle body. Now things are finally running fine with it and I think the improvements to the torque curve were well worth it. There wasn't much drop in torque down low, and the increase in torque up high was reasonably substantial as shown in the latest B16A Dyno Runs.

For pictures and details of the Ford XF throttle body swap, go to the Ford XF Throttle Body Installation web page.