cujet

My 2004 AP2 Inline Pro stage 1 is in need of a larger throttle body. The car requires too much throttle movement to come up on boost. I've adjusted the throttle cable for a higher pedal and everything is OK mechanically. It simply feels sluggish due to oversized turbo, lag issues and small throttle body. I'd like it to feel more like my other turbo cars where about half throttle results in boost. Plus, if I gain some HP, that would be OK too.

I've been able to improve the overall performance of the system by reducing exhaust restriction in the normal way. I've also recirculated the wastegate, as it used to dump right on to the side of the engine, causing re-ingestion of exhaust gasses.

What I'd like is more airflow at half throttle. Hence the desire for a larger throttle body.

There are many options available. I have no idea which is the best for a street car running 19 pounds boost.

Science of Speed touts their sealed shaft, allowing the use of water/meth injection. Skunk2 has a billet 70mm that looks nice too and appears un-sealed (but I'm not sure)

I have a small machine shop, so I can weld the intake manifold if necessary. But it might be nice to have a plug-n-play.

staylor725

I have the skunk2 74mm throttle body it is a very nice looking but I found it is not sealed on the shaft. I boost leak test my car every time I remove the charge piping. After I installed it I pressure tested it smoke tested it and found that it leaks on the cable side. I contacted skunk2 and this is normal, I guess they use no o-ring on the shaft to seal it. My buddy just got a hyper tune 77mm throttle body for his sr swapped 240, it looks very nice but has not installed it yet because they are universal and needs to modify the intake manifold. They are supposed to be really good but go for $600 bucks. Sos sounds good just make sure whatever you get is sealed.

Jin_SK

I doubt a bigger throttle body will make nearly the difference you want, if anything it'll be worse. You will gain some top end but probably won't see any better spool. Seems like the most obvious answer is get a more properly sized turbo (i.e. smaller, but is a 30R really THAT slow?), but I'm assuming that's not an option so a quick spool valve might get want you want. Basically greatly reduces the A/R of the turbo until a certain RPM. Can you post a boost plot?

Chitoki

OEM or SoS

6spdap1

I have a brand new in the box 74mm black pro series skunk2 throttle body for sale. Lmk

6spdap1

located in SoCal

cujet

I've been doing turbo cars since 1979, both professionally (back then, for Ford) and for play now. A larger throttle body will get me exactly what I want. More airflow at half throttle.

I don't need more power. I simply hate the feeling of depressing the pedal so far to achieve anything. A "more touchy" throttle is exactly what I desire.

A quick spool valve won't fit easily on my setup. I'd considered doing this, but decided against it.

As much as I like to complain, the car really does drive well now. I'm quite happy with it. Even the spool up is live-able. I simply want to tweak it into a more refined car.

baZurk

Try posting in the marketplace

Jin_SK

Flow will increase, but as the expense of velocity though right? If a more responsive car is what you want then a larger bore TB doesn't seem to match with your goal. I don't know if they still do it, but Urge had a head that supposedly accomplished exactly that. Increased velocity resulted in faster spool. If you do decide the TB route, I'd be genuinely interested in a before/after boost plot to see what difference there is.

cujet

Since my goal is to change part throttle performance, not full throttle performance, the TB makes complete sense.

As far as velocity goes, the intake runner pressure and velocity will be the same at any given, specific, part throttle output. The difference will be pedal position. With a larger throttle body requiring less pedal input for a given engine output.