Fly911

FVD and possibly others offer a bigger throttle body for the 993, both for NVR and VR motors. As far as I know, FVD bore out a standard throttle body, from 68mm to 71mm on the NVR and from 65mm to 70mm for the VR, and install a new butterfly accordingly. To me this looks like a job any carburator shop could do for a fraction of the price.
For the NVR increase from 68mm to 71mm gives a 6% increase in throttle body area, and in theory a 6% increased air flow, that again in theory should give a 6% increase in HP as long as the air/fuel mix is still correct. Also, in theory each 1mm increased bore should give around 2% air flow increase.
My question is; are there anyone out there that can bore out the throttle body to let's say 75mm, and install a new butterfly flap to match?

Steve Nagata

I'm running a 75mm powerhaus throttle body.

See attached pictures.

Stealth 993

Well, unless other things are done on the motor, you most likely will see 0hp increase, or only slight increase at the last range in the RPM. But if you have cams, exhaust & other stuff, it might give you a little bit.

You might loose some low end torque, & you will totally change the throttle modulation. Your A/F will be fine, & the ECU will keep it in the happy zone.

I've built a few motors, the TB is usually one of the last things you do. I had a fully built BMW engine, increase bore, big head, big cams, race header, etc. I then went & put on a $5000 set of bigger TB's (there were 4) I gained like 4hp from it. You only get the HP if the TB's are getting maxed out currently & are the bottle neck.

Kika

I had the throttle body on my SC bored out by Ed Mazula (lives a few blocks from me, used to advertise in Excellence, not sure if he still does throttle body work or not)

I had it done when my engine was apart, and honestly, I don't know that it made much of a difference. I think it would have been beneficial in conjunction with other mods, like higher compression P/Cs or larger displacement, but in and of itself, I didn't notice a bump in power, but the engine did seem to run smoother.

On another note, I thought that the 993 throttle body used a hot wire set up and didn't use a butterfly valve?

If Ed is still doing these, (Don't see him advertised in Excellence anymore) he is a good option, I was pleased with the customer service, quality of work etc... Not to mention he had a sweet Shelby Cobra. his number used to be (800) 792-9338.

TheOtherEric

I would expect pretty modest gains, and only at high rpms, from this mod.

Remember, there are MANY sources of air restriction. The throttle body is just one of them. Perhaps it's a major contributor, so I'd like to hear experiences with this mod. Hopefully one of our engine experts will chime in.

Stealth 993

I think you are confusing the MAF for the TB (throttle body). The MAF does the air metering, & they used to use a AFM, that had a "barn door" to meter air.

Of course all the engines, have a TB, but I also thought on the 96+ cars there are a primary TB with a small secondary TB?

TheOtherEric

You're thinking of the mass air flow sensor, which is hot wire. You still need some type of valve to control the amount of air that's let into the engine.

ChaseN

Sport Evo TB's on an S14?

Stealth 993

Yup, then I had them cleaned up for another $4-500. Next worst bang for the buck was the Rally 2pc header, that also did like 3hp for $1400.

Makes Porsche stuff look cheap!

RDS928S

I considered this mod until the guy's at 9M noted & loss in power with just the throttle body on a stock motor!!.
They reccomended ECU/X-Pipe,or lightweight flywheel for doccumented gains.
Next would be cams & the throttle body.

ChaseN

Yup, hence my engine swap when my S14 grenaded. It was either spend $20k on a 2.5 that makes 280hp (maybe), or spend 10k on 321hp + boatloads of torque (comparatively) and the same rev-happy nature.

Pisses off about 1/2 the fellow owners I meet though. Oh well.

Stealth 993

LOL, yea, I kept the S14, invested around $30k, & had 305hp (crank). But I learned a ton, & know what works, & what doesn't.

ChaseN

Definitely. I wish I had the money to build (and maybe rebuild at those power levels) a wild A/N 2.5.

BTW your sig definitely seems familiar from s14.net

Stealth 993

Yup, that's me, been there since the start. The A/N did build a ton of HP! That was well worth it!

ChaseN

All I can say to you, owning an e30 M3 and a 911, is you have impeccable taste