H23 throttle body overbore – Worth it?

[H.M.]

I have all the parts to install a H23 plenum and TB with A6 runners, A6 butterflies, a gutted A6 butterfly spacer, Bisi gasket and proper ECU on my 90 EX A4.

Having the TB overbored costs $100 and having the plenum port matched to the overbored TB brings the total to $190.

Will I notice the effect of the overboring and port matching?
Would I notice if I just did the TB overboring and didn’t port match the plenum?

I know that asking if it's "worth it" is kind of subjective. I'm just trying to get the most bang for my buck and, given that I'm not trying to improve the speed of the car too much, trying to find out if $100-190 would be better spent elsewhere.

Either way, I’ll have the injectors cleaned when I do this install. This will probably be the only “go fast” mod I will make to my car, which is a daily drive.

Here are the other mods I’ve done or planned so you can see where the intake fits in.

Done
New timing belt and related components. Short ram with HK air filter.
Tokio springs & Struts. Front and rear upper sway bars. Replaced all suspension bushings throughout. Installed 91 wagon discs in front, 93 discs in rear.

To Do
Alarm (have, installing now).
New intake Manifold (have all components)
17” wheels (have rims, need to get tires). HID lights (need to get).

[Jarrett]

Please don't be one of these idiots that just installs HIDs without projectors. They're going to blind the crap out of everyone on the road.

I don't really think the boring and port matching is worth it. Especially not the port matching. They're charging you $90 to do something you could do with a carbide bit at home.

The intake itself is great by itself. What about complimenting that with a 2.25" exhaust?

[H.M.]

Here is what is involved in Maxbore's TB boring. It sounds like a rebuild and overhaul in addition to the boring:

Now some information about what it is Maxbore does. The TBs are disasembled, that includes all the sensors and all moving parts. Then the TBs are thoroughly degreased and cleaned. TBs then go to the lathe where they are bored, then ported and finally polished. The opening of the throttle body gets a taper that begins at 6 degrees then 3 degrees then it is hand blended. A new bigger custom butterfly is machined out of brass. We do not use aluminum or steel. The brass we use is a special type of oil impregnated metal that lubricates itself. It is more expensive but provides long lasting operation without binding. The butterfly is then carefully fitted to the throttle body. Once the proper seal is achieved the TB is reassembled. The throttle position sensor (TPS) is reinstalled (if included) using new screws and it is set to factory specifications.

[deevergote]

Maxbore's reputation is quite good, and the price is very reasonable compared to some other companies out there. However, the engine is a giant air pump... so the only way to really see any gains is to increase airflow from beginning to end... the intake filter all the way through to the muffler. Increasing just one part to a greater extent than the rest won't do much good. The H23 manifold and TB will flow pretty well as-is for an F22a that has regular bolt-on mods. If you do some work to the head and internals, then an overbore may be worth it.

[H.M.]

If you do some work to the head and internals, then an overbore may be worth it.

Thanks deever,
do you mean smoothing and port matching the head? Or something else?
I've looked around this site but haven't seen too much regarding that.

And regarding the exhaust, I thought I'd read here that the stock exhaust provides the proper back pressure for our engines. Or is that only true before the H23 plenum install?

So exhaust work needs to be on my mod list? Header also, or just cat back?

[deevergote]

I mean a full port and polish, performance valve job, etc...

If all you modify are the parts bolted to the engine, the engine itself becomes the bottleneck in the system.