Topic: Throttle Body Porting How To

[Chavez]

I was gonna post this under mod of the day but decided to keep that post clean. Its pretty easy, took me an hour and 45 minutes start to finish and is probably the only thing Ive done that has gone 100% smoothly . Gains down low and up top are def worth the time. Not huge but car doesnt bog as much down low and seems to kick into second abit harder. I did not touch the throttle plate as I did not want to mess it up and have to replace the TB. I may go back and do the plate later and clean up my job a little.
Here is a quick step by step:
 
Tools:
-12MM socket and ratchet
-3" extension for socket
-Flat head screwdriver
-Couple grinding bits (a stone, a bur and a flapper wheel) and tool (drill, dremel, die grinder) of some kind
-Spray cleaner of some kind
-Can of Duster or air compressor
-Eye protection
 
1. Remove the intercooler
2. Unplug the 3 sensors on the TB
3. Unplug and cap/plug the 2 coolant lines
4. Remove the throttle cables
5. Unbolt the 4 X 12MM bolts holding the TB
6. The TB should pop off but be careful the gasket is fragile and reuseable
7. Plug the small hole near the butterfly with as minimal material as possible for working room but make sure its plugged well
8. Put on eye protection
9. At first I used a grinding stone to grind down/smooth the small lip fairly close to the butterfly. I did not go deeper than that. The aluminum will clog the stone.
10. I switched to a carbide bur as it is much faster, the filings are a lot easier to clean, it does not clog up to taper the leading edge and taper the walls. The bur will make it easier to mess up so go slow. I tried my best to knife edge the whole thing and make as smooth of a transition as possible. Don't go to crazy as it needs to be strong.
11. After I was happy I used a flapper wheel to quickly smooth the roughness down
12. Blow out the TB. If you use your mouth you'll get filings all over your face. LOL I know that
13. Use the cleaner on the TB mine had a lot of black gunk on it plus a couple stray filings. I used brake cleaner but Im not 110% its safe so I tried to evaporate it as fast as possible plus gave it abit of a wipe with a damp cloth.
14. Reinstall the TB steps 1-5 in reverse order.
15. Reset the ECU and enjoy
 
Evan

[wingless]

were there any pics with this... I've wondered how easy this really is...

[Chavez]

It is really easy if you take your time and are not worried about it looking perfect, I have a habit of taking off to much material and I did fine.

[Vancouver98STi]

No one here except for wingless way back in 2008 has wondered what the heck that Chavez was actually removing and where from?  Damn, I'm feeling inadequate.

[funk32]

Because it's not really worth the work. The TB is not a bottleneck. Plenty of people are making well over 500whp on the oem un touched tb.

[Vancouver98STi]

Because it's not really worth the work.

I guess I was just a little surprised that there was a seemingly thorough and well written "how to"... but with absolutely no images to clarify what was actually being done.

No, I won't be breaking out the Dremel. 

[GrantC]

<thread tidied up>

This thread (https://forums.nasioc.com/forums/showthread.php?p=14131078#post14131078) seems have pics that match up with the lip Chavez described.

I'd say we've almost all seen that lip when taking the TMIC off for one reason or another, so it's a fair thing to wonder about. (I've never touched it for the rules of the autox classes I tend to build my car for not allowing it.)

Every mod/maintenance/swap seems to start like:
-disconnect battery ground cable
-remove tmic
...

[Vancouver98STi]

This thread seems have pics that match up with the lip Chavez described.

Ah... excellent. Now I understand what Chavez was referring to. I've got much to learn about these cars. Thanks.

I've linked to a couple of images from that thread. They show quite well what the "before" and "after" TB looks like.

[Canuckrz]

It's not really so much a lip so much as a less than smooth transition. Even completely smoothed out the bottleneck remains at the valve on the throttle body. Imo I wouldn't expect to see much if any benefit from it in our application; though I doubt it would hurt anything to do it except maybe increase the chance if it cracking if you taper down the front edge of it as much as the guy in the picture did.

[seat safety switch]

I wish someone had a flow bench so we could get numbers on this port job before/after.

I have a feeling it's not as big of a restriction as the intake manifold is in general.

[Vancouver98STi]

I have a feeling it's not as big of a restriction as the intake manifold is in general.

That was certainly the situation with an engine I'm familiar with, the Fiero's 2.8 V6. It used to be a popular mod to bore out the TB... until it was clearly demonstrated that the major restriction was actually in the "neck" of the intake.

The first image below shows where the intake was cut open, and the second image shows a stock TB gasket placed over the end of the cut intake. In this particular example, it's quite obvious that opening up the TB was pointless unless this major restriction was also removed from the intake.

 

[Rathburn]

Pft, just use sand, like the pros:

Hey guys, I've got a 98 1.8T. I've had a k04 and chip for a while and wanted to get more performance. I was recommended to port and polish the intake and exhaust. We found out they used abrasive material to do it like gritty sand. So I got with my friend that tunes Hondas and we decided to try it ourselves. We got a bag of sandblasting sand and hooked up into the intake and started the car. We had to hold the gas so it would run. He wanted to let the engine suck in the sand through the intake so it would port it out and then push it out the ehxaust so it would port the exhaust manifold.
I was worried that it might cause problems but he figured it'd be OK as long as we didn't make boost and it get sucked in the turbo. After running the car and letting it suck in sand we got about half way through a 25 lb bag. The check engine light was on and the engine was bucking and kicking and sounding really weird. We stopped and hooked the car back up normal and took off the sand supply. We tried to start it again and it was really hard. Once started it couldn't idle and kept making weird noises. We took it out and drove it and it started to make scraping and knocking noises.
Help! Can anyone tell me what to do! My buddy only does Hondas so he doesn't know much about Audis.

http://www.audiforums.com/forum/off-topic-5/hey-guys-please-help-my-mods-gone-wrong-80267/

[Vancouver98STi]

Pft, just use sand, like the pros...

Heh heh... I think there's probably a version of that story in every automotive forum.