Why people use the FD and FC throttle bodies on 20B's
 

I was just wandering if anyone could explain to me the advantages of switching out the original 20B throttle body for an FC or FD one. It just doesnt make much sense to me because wouldnt the original TB fit better? and if you wanted to you could bore it out right? Or is it a general unavailability issue with the 20B swaps these days? I just really want some clarification because i saw a friends car that "supposedly" had a 20B in it but it had the FD throttle body so i thought he was full of it, and of course he didnt know shit about the car. Please help me on this lol.

I don't know about the switching of throttle bodies, I've seen plenty of people use the 20B TB. Also, did you try counting the rotors on your friend's car? if there are 3, I'm fairly sure its a 20b lol. Also fyi a 20b says "20b" on it too.

FYI: stick with counting rotor housings ... some people build 20Bs with 13B rotor housings. :)

as for the original question ... i don't know.

i've never come across a case where anyone had used a 13B-T throttle body on a 20B. i was under the impression that the 20B shared the same throttle body with the 13B-RE and -REW engines, but all are different from the 13B-T unit. perhaps i'm mistaken.

The 20B/13B-re throttle bodies are not the same as the FD. The TPS is on the opposite side as well as the linkage. There is also an air bleed screw on top of the 20B/13b-re like a 13B N/A TB. The ISC/BAC is mounted to the bottom of it as well.

http://www.banzai-racing.com/20B/Eng...0B_lg_blk1.jpg

i'd assume that most people run whatever throttle body they can come by in the simple aspect that not all 20B engines come to the US complete, many people piece theirs together and cannot easily find a 20B throttle body. when installing it into another car anyways, it sometimes is easier to use the stock throttle body for that series since the linkage routes properly(however the 20B UIM doesn't have a mount for the bracket so i really don't know why aside from scarcity of parts).

thanks for clearing that up.

do they at least share the same bolt pattern? i ask because a few years ago, when i was looking for a throttle body for my REW, i almost bought an RE throttle advertised as a direct fit.

They have the same bolt pattern, but the mating surface is different. People that install FD TB's on the 20B need to modify the back side or they have vacuum leaks. So it is not a direct fit. Also there are only 2 studs for the intake elbow, so it would have come close to being a direct fit on an FD.

To answer the OP question, I think some of it comes down to being able to install a Greddy elbow. Additionally the TPS is different so sourcing the connector can be more of a task when installing the engine management system.

I made a custom Greddy elbow by welding on the 20B elbow flange

http://www.banzai-racing.com/20B/Par..._20b_elbow.jpg

Oops. Should have been

......so it would NOT have come close to being a direct fit on an FD....