Been looking at sp quick spool valves but don't want to change my doe pipe and hard lines for oil and coolant, plus they're price is ridiculous.

Since the sp qsv is proven technology, but I've seen people who have broken these as well, I wonder why the s4 turbine housing with built in quick spool for twin scroll is not as good as this.

Is it only because it is operated by stock solenoid. Can you change from operating off a solenoid to a wastegate and boost controller, which I have extra of?

Currently running s5 hybrid but will gladly run s4 manifold and custom wastegate actuator for the twin scroll flap. Trying to reduce lag and increase torque so please let me know from experience you're conclusion. I know people always say eliminate the s4 flapper, but I want to make this work.

 

s4 system: stock turbo manifold with two different A/R passages and a vacuum-controlled valve that switches them based on engine speed. Turbine housing is single scroll.

s5 system: stock turbo manifold with equal sized A/R passages and matching twin scroll passages.

Quick spool valve: aftermarket system meant for larger twin scroll turbos and single scroll manifolds (open collectors). Closes off one scroll and switches based on pressure control, similar to an internal wastegate.

Who says the s4 system is worse? It's not designed for the same purpose compared to a quick spool valve. It's designed for torque under 3000rpm on a 182 horsepower engine for a specific turbo. It's going to vary with the setup, but I don't see going to an s4 manifold as improving spool. The quick spool valve is a universal part.

You didn't give any major details on your setup, like your porting, what you're using for boost control, what your exhaust system is, what your intercooler is.

 

I just put together an S4 hybrid setup and I kept the quick-spool/twin-scroll/flapper. When the car is running right, I can do some back to back runs with functional valve vs 100% open valve, and get some log data on this little thingy.

 

Id appreciate the data logging.
Car is s5 t2. Stock ports
Rtek 1.7 but have a power Fc sitting on my desk
Pan speed hybrid t04b with unclipped turbine wheel
Greddy profec b spec 2
Fmic (too large for what turbo I have)
3" exhaust
3" intake

Was talking to friends about the sp qsv and how dang expensive it is. Drive in California so I like having hidden power adders. Have a hx35 and manifold I can use in my garage that would allow me to use the sp qsv. But if I can better control the s4 setup, I'd be interested.

Threads years ago always said ditch the s4 flapper or run s5 turbo, but I wonder if they've been overlooking good technology with the s4 design.

 

Colinshark when do you think you'll have your car running straight to datalog? No rush just curious

 

Absolute best thing you can do on your set-up for spool from my experience with similar set-up (s5 hybrid) is go to a bigger exhaust or at least the downpipe/midpipe.

I had RB RevTII 3" turbo back and it spooled like crap compared to 3.5" turbo back or even just the 3.5" downpipe/midpipe connected to the RB 3" rear.

Full boost 500rpm later on the RB downpipe/midpipe and much less boost 1,000rpm-2,500rpm.

The RB RevTII is very restrictive despite the 3" diameter because it has 3 or 4 cheated radius cuts/bends on the way to the Y-pipe.

If you buy two Ebay $150 FC downpipe/midpipes and have them fabricated into a dual tube downpipe/midpipe system to the rear section of your 3" exhaust you will have tremendous spool while keeping boost creep at bay (restricted by your exhaust rear section).
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My TII was S4 and I can tell you the S4 dual scroll system is not the droid you are looking for.

The primary exhaust passage is 0.40AR so it chokes the engine VE killing torque even at low rpm if you try to move more air through the engine than the stock turbo could. The 2ndary passage is 1.20AR for a combined AR of 0.80 with both open.

S5 turbo has both scrolls the same 1.00AR and even on a stock turbo Mazda found letting the engine breath was an improvement.