After years of development, USRT is now in the homestretch with regards to plug n' play ITB kits for Volkswagen crossflow 8v, 16v, and 1.8T engines. We are also looking very closely at the Audi B6 V8 engine and, finally, the early Mazda Miata 1.6l + Mazda 323 GTX (BFMR).
Kits for modern engines will feature a drive by wire (DBW) control. This permits use of the FACTORY ECU -an aftermarket WORLD's FIRST. VW 6-cylinder systems are under consideration but will utilize a different throttle design.
Throttle response is greatly improved over single TB designs by placing multiple throttle plates immediately before the intake valves. The air charge must only travel a few inches rather than a foot or more with a conventional manifold.
High-rpm power is greatly enhanced due by eliminating flow-restrictions and special timing of intake air pulses. Each individual throttle plate is smaller than a stock throttle. This accelerates air flow into each cylinder. However, the sum flow area with ITBs is huge compared to even an upgraded single unit. Thus, ultimate flow potential is improved substantially but without the "tip in" jumpiness associated with a huge conventional (single) throttle.
Upwards of 200hp can be made with normally aspirated 16v or even all out 8v engines. Forced induction ultimately delivers more power for the dollar. However, ITBs are much simpler, lighter, and compact. And, then there's that wicked sound!
- Equal-length intake sections.
- Straight air paths to intake valves for superior breathing.
- Intake passages are each smaller in volume, yet larger in total volume. Port velocity is increased for enhanced response and torque. Total flow is increased for maximum horsepower.
- Velocity stacks can be custom-tailored to match cams. Torque/power peaks can be tuned for a target rpm. A supercharging effect can also be produced within a narrow rpm range.
Increased Bottom-end Torque and Mid-range
Each cylinder fills more efficiently with air/fuel. Greater port velocity and improved breathing means a broader/flatter torque curve across the entire rev range -especially in the midrange. A properly-set up ITB'd engine can be very tractable in "normal" driving while delivering a screaming top end. This is a major improvement over regular manifolds.
Acceptable idle quality may be retained even with wild cams since individual cylinder's air pulses do not affect adjacent cylinders. Those converting from CIS (Bosch mechanical fuel injection) get a double benefit in that the restrictive airflow meter plate is eliminated. DBW idle is mostly unchanged from stock.
Video shows VWMS testing Extrudabody 45mm ITBs on F1 engine dyno with Macau Grand Prix track simulated (2.0l 16v FSI with non-direct injection).