Understanding Individual Throttle Bodies

Individual throttle bodies (ITBs) represent a fundamental shift in how an engine breathes. Instead of a single throttle plate that meters air for all cylinders through a common plenum, each cylinder gets its own dedicated throttle plate and often a short intake runner. This design dramatically reduces intake air restriction and eliminates the cross-cylinder air disturbances that can occur in single-throttle setups. The result is an immediate, linear throttle response and a crispness that is difficult to replicate with any other air intake modification.

ITBs were historically found on high-performance racing engines and some iconic sports cars, such as the Ferrari 308, Lancia Delta Integrale, and early Honda NSX. In recent years, aftermarket kits like those from APS Racing have made this technology accessible to a much wider range of enthusiasts. By allowing the intake system to flow more freely and by sharpening the airflow signal to the fuel metering system (carburetor or EFI), ITBs unlock power at every engine speed, especially in the mid-range and top end.

APS Racing ITB Kit: Features and Build Quality

APS Racing has established a reputation for cost-effective yet well-engineered hardware. Their individual throttle body kits typically include:

  • Aluminum throttle bodies with precision-bored bores for consistent airflow per cylinder.
  • Tapered or straight intake runners designed to match a specific engine's port geometry.
  • Mounting flanges and gaskets for a secure, leak-free seal to the cylinder head.
  • Throttle linkage to sync all plates simultaneously, often with adjustable stops.
  • Velocity stacks to smooth incoming airflow and enhance low-end torque.

While the $1,200 base kit price positions APS as a value leader, the quality of materials and machining is generally on par with mid-range competitors. The kit is available for a variety of popular inline and V‑engine layouts, including the Toyota 4A-GE, Honda K-series, BMW M50/M52, and many others.

Full Cost Breakdown: From Box to Running Engine

The advertised $1,200 is only the starting point. A complete, successful ITB upgrade requires several additional investments—both financial and procedural. Here is a realistic breakdown of all costs involved.

APS Racing Throttle Body Kit – $1,200

This covers the core hardware: the throttle bodies, runners, linkage, velocity stacks, and basic mounting parts. It does not include a suitable intake air filter setup, which must be purchased separately (typically $50–$150 for pod filters or a custom airbox).

Installation Labor – $400 – $800

The installation complexity varies widely depending on the vehicle and the engine’s original induction system. A do-it-yourselfer with mechanical experience can perform the swap in a weekend, saving $400–$800. However, most enthusiasts choose professional installation to ensure proper fitment and to avoid vacuum leaks or damaged parts. Rates average $100–$150 per hour, and the job often takes 4–8 hours when prep, removal of old manifold, and reassembly are included.

Engine Tuning – $300 – $700

ITBs change the engine’s airflow characteristics completely. A standalone ECU or a piggyback controller is almost always required to recalibrate fueling and ignition timing. Professional dyno tuning is recommended—and in many cases mandatory—to safely realize the power gains. A dyno session with a skilled tuner can cost $300–$700 depending on the region and the complexity of the engine management system. Some tuners charge an hourly rate of $100–$200, and a thorough tune may take 3–5 hours.

Additional Parts – $150 – $300

  • Intake filters or airbox: $50–$150
  • Vacuum hoses and fittings for intake manifold connections (MAP sensor, PCV, etc.): $20–$50
  • Throttle cable adapter or custom linkage if the original cable doesn’t fit: $30–$80
  • Gaskets, sealants, and fasteners: $20–$40
  • Fuel injector adapters (if converting from carbureted to EFI): $100–$200

Estimated Total: $2,050 – $3,000. The wide range accounts for DIY vs. professional labor, tuning cost variations, and unforeseen hardware needs.

Expected Power Gains: Realistic Dyno Data

While the manufacturer may claim peak gains of 15–25 horsepower, real-world results depend heavily on the engine’s baseline state and the quality of the tune. Here are typical dyno results from documented APS Racing ITB installations.

Stock Engines (unmodified)

On a naturally aspirated, stock engine with a restrictive single throttle body, adding APS ITBs plus a proper tune generally yields:

  • Mid-range torque: +10–15 ft-lb between 3,500 and 5,500 rpm.
  • Peak horsepower: +8–12% (e.g., 10–15 hp on a 150 hp engine).
  • Throttle response: noticeably sharper, especially during part-throttle transitions.

Engines with Camshaft and Exhaust Upgrades

When ITBs are matched with a sport camshaft, header, and free-flowing exhaust, the volume of air the engine can move increases dramatically. The ITBs then act as a minimal-restriction path, allowing the engine to breathe fully. Reported gains in this scenario:

  • Peak horsepower: +15–25% (20–40 hp on a 200 hp engine).
  • Red line power: often holds up much better, with less drop-off beyond peak rpm.
  • Sound: a distinctive, aggressive induction roar that many enthusiasts consider priceless.

For example, a 2000–2005 Honda S2000 (F20C engine) fitted with APS Racing ITBs, a set of Toda camshafts, and a custom exhaust has been documented on dynos to exceed 260 whp, compared to a stock baseline of 220 whp—a net gain of 40 horsepower at the wheels.

Limitations and Expectations

ITBs do not create an instant “turbo-like” torque curve. The gains are more pronounced at higher engine speeds. Engines that rely heavily on intake resonance (such as Honda VTEC) may lose some low-end torque if the runner length is not carefully matched. Proper tuning can minimize this trade-off, but it is a reality of ITB upgrades.

Factors That Influence the Final Power Outcome

  • Engine displacement and head flow: Larger engines and heads with good port design will gain more from the improved airflow.
  • Camshaft profile: ITBs work best with camshafts that have moderate to aggressive duration and lift, as they allow the engine to fill the cylinders more effectively at high rpm.
  • Exhaust system: A choked exhaust negates ITB gains. A high-flow exhaust is nearly a requirement.
  • Carbon cleaning and valve sealing: Any existing intake carbon deposits or poor valve seal will reduce the effectiveness of the ITB upgrade.
  • ECU and tuner skill: The tuning is the single most important factor. A conservative tune on a stock ECU may leave 10% of potential power on the table.

Installation Process: A Step-by-Step Guide

Installing APS Racing ITBs is a mechanically intensive but straightforward project if you have the right tools. Always consult the kit’s specific instructions, but the general process is as follows:

  1. Disconnect battery and drain coolant if the coolant lines run through the original intake manifold.
  2. Remove the intake manifold and any attached vacuum lines, throttle cable, and sensors. Label everything.
  3. Clean the cylinder head mounting surface of old gasket material using a plastic scraper—do not scratch the aluminum.
  4. Install the supplied gaskets and mount the ITB baseplate (if separate) or the entire throttle body unit to the head. Torque to specification.
  5. Attach the velocity stacks and any included plenum or air filter mounting brackets.
  6. Reinstall the throttle cable, adjusting it so that the plates open fully when the pedal is to the floor and close completely when released.
  7. Connect vacuum lines for MAP sensor, brake booster, PCV, and any idle air control valve if used.
  8. Mount intake filters or a custom airbox. A proper airbox can reduce IAT rise on hot laps.
  9. Refill coolant and check for leaks around the new gaskets.
  10. Quickly sync the throttle bodies using a manometer or smoke tester so that the idle speed is even across all cylinders.

Do not attempt to start the engine without a baseline tune file in the ECU. Running a stock tune with ITBs can cause lean conditions and engine damage.

Tuning Considerations: Unlocking the Full Potential

Tuning an ITB-equipped engine differs from tuning a standard single-throttle system. The primary challenges are idle quality and throttle tip-in. With individual throttles, the intake manifold vacuum at idle is typically much lower, which can confuse a MAP sensor and cause a rough idle. Experienced tuners often switch to a speed-density tune (MAP only) or blend speed-density with alpha-N (throttle position based). Alpha‑N tuning uses throttle angle and rpm as the primary load inputs, which can provide a stable idle but requires careful calibration at small throttle openings.

Critical tuning parameters:

  • Ensure the air-to-fuel ratio stays between 12.8:1 and 13.2:1 under wide-open throttle for naturally aspirated engines.
  • Adjust ignition timing to take advantage of the improved cylinder filling without causing detonation.
  • Set idle speed to 800–1000 rpm with appropriate idle air control (if retained) or with a throttle stop screw adjustment.
  • Use a vacuum gauge or synchronized manometer to balance each ITB’s idle flow—this step is often done iteratively with tuning.

Helpful resources: For more on ITB tuning strategies, read this guide from EFI Tuning University or check the detailed forum thread on Honda-Tech.

APS Racing vs. Other ITB Options

The aftermarket ITB space includes several well-known players such as Jenvey, DCOE (Weber/Dellorto), and custom fabrications. Here’s how APS Racing compares:

  • Price: APS is roughly 30–40% cheaper than Jenvey kits, which often cost $1,800–$2,500 for a similar four-cylinder set.
  • Material finish: Jenvey uses billet aluminum with anodized finishes; APS uses cast or machined aluminum with a brushed finish. Both are durable, but Jenvey parts have a more polished appearance.
  • Fitment: APS kits are known for requiring some minor fabrication on certain vehicles (e.g., custom TPS mounting bracket or throttle cable adapter), whereas Jenvey often provides a more bolt-on experience.
  • Backward compatibility: APS offers adapter plates for older casting patterns, making them a favorite for budget builds.

For racers or track-day enthusiasts on a tighter budget, APS Racing offers an excellent price-to-performance ratio. For concours-level restorations where aesthetics and perfect fitment matter, the higher-cost alternatives may be worth the premium.

Is the APS Racing ITB Upgrade Worth It?

The answer depends on your goals and your vehicle’s overall setup.

  • Yes, ITBs are worth it if you are chasing throttle response, top-end power, and the visceral intake noise that transforms the driving experience. If your engine already has good supporting mods (camshaft, exhaust, ECU), ITBs will magnify those gains.
  • No, ITBs may not be worth it if you primarily drive in city traffic, care more about low-end torque than peak power, or are not prepared for the additional tuning complexity and potential idle fussiness.

A $1,200 base kit that ultimately costs ~$2,300 installed and tuned is still a competitive upgrade in the world of performance modifications. For reference, a set of aftermarket performance camshafts alone can cost $600–$1,200—and without ITBs, the engine may not fully exploit them.

Conclusion

Upgrading to APS Racing Individual Throttle Bodies involves more than just the headline $1,200 price tag. When you factor in labor, tuning, and ancillary parts, the total investment typically lands between $2,000 and $3,000. In return, you can expect a 10–20% increase in peak horsepower on a properly matched engine, dramatically improved throttle response, and a sound that alone can justify the expense for many enthusiasts.

For those willing to put in the work—either on the side of the car or paying a professional to do it—the APS Racing ITB kit is one of the most cost-effective ways to experience the driving benefits of individual throttle bodies. As with any high-performance modification, the key to success lies in careful installation, thorough tuning, and an honest assessment of your vehicle’s overall potential.