Modifying your Mazda Miata’s intake system is a popular upgrade for enthusiasts looking to enhance performance and engine sound. However, navigating the world of aftermarket intakes can be complex. Many owners, when monitoring their car’s performance through OBDII readers, might encounter readings that seem puzzling, such as “Miata Obdii Torque Reads 80hp”. This reading, while potentially concerning, often stems from a misunderstanding of OBDII data interpretation and the nuances of intake modifications. Let’s delve into how intake changes affect your Miata’s performance and what those OBDII readings might actually mean.
Understanding Miata Intake Modifications and Their Impact
The quest for improved horsepower and torque in a Miata often begins with the intake system. The factory intake is designed for quiet operation and adequate airflow for stock performance levels. Modifications typically aim to increase airflow, reduce intake air temperature, and sometimes, enhance the engine’s intake sound. The original poster experimented with a few different setups, highlighting common challenges and solutions.
Initial Experiment: AEM Style Intake and Power Loss
The first attempt involved fabricating an AEM-style intake using leftover parts. While visually appealing, the immediate result was a noticeable power loss, especially without the resonator. This underscores a crucial point: intake design is not just about looks. Removing components like the resonator, intended to optimize airflow and minimize pressure waves, can negatively impact performance.
The Importance of the Resonator and Stock Crossover Tube
The experimenter quickly reverted to the stock crossover tube, a key component in the factory intake system.
This “weird sensor thing” is likely the Mass Air Flow (MAF) sensor or Intake Air Temperature (IAT) sensor, both crucial for the engine management system to accurately measure airflow and air temperature. Properly integrating these sensors into any intake modification is essential for correct engine operation.
Drawing Inspiration and Refining the Design
Inspired by designs like “spitefulcheerio’s”, the next iteration aimed to refine the stock crossover setup.
This setup incorporated a “cool box” (heat shield) and a 90-degree silicone coupler to mount the filter while utilizing the stock crossover tube and sensor placement. The heat shield is critical to isolate the intake from engine bay heat, ensuring cooler, denser air enters the engine for better combustion. The experimenter also noted that despite appearances, the filter cleared the hood, and air temperature in the filter area was close to ambient, both positive signs for performance.
The Best Miata Intake Design Principles
Based on these experiments and observations, the author concludes that the optimal Miata intake design should:
- Barrier from Header Heat: Minimize heat soak from the exhaust header, which is a significant heat source in the engine bay. A cool box or heat shield is crucial for this.
- Utilize “Passive Harmonic Miniboost”: This likely refers to the tuned resonance within the intake system, potentially aided by the resonator, which can subtly improve airflow and cylinder filling.
- Coldest Air Possible: Source air from the coolest location, ideally outside the engine bay. Positioning the filter near the headlight opening is a common strategy to draw in ambient air.
The recommendation is to retain the stock crossover pipe with the resonator and focus on building a cool box and positioning the filter to access the coldest air. Ideas like a snorkel for ram air effect are considered but deemed unlikely to provide significant additional benefit in this context.
Interpreting “Miata OBDII Torque Reads 80hp”
Now, let’s address the “Miata OBDII torque reads 80hp” concern. It’s highly improbable that a healthy Miata, even with intake modifications, would consistently display only 80 horsepower when reading torque via an OBDII scanner and converting to horsepower. Here’s why and what might be happening:
- Misinterpretation of OBDII Data: OBDII scanners primarily read engine parameters like Mass Air Flow, RPM, and Manifold Absolute Pressure. Horsepower and torque are calculated values based on these readings, not direct measurements. The accuracy of these calculated values depends on the scanner’s algorithms and the accuracy of the sensor data.
- Context-Dependent Readings: OBDII readings are instantaneous snapshots. An 80hp reading might be observed at idle or low load conditions. Horsepower output varies significantly with engine RPM and load. A full-throttle, high-RPM reading is necessary to assess peak horsepower.
- Scanner Limitations: Budget OBDII scanners may have less sophisticated algorithms or slower refresh rates, potentially leading to inaccurate or misleading horsepower calculations.
- Units and Conversions: Ensure the OBDII scanner and any conversion formulas are using correct units (e.g., lb-ft for torque, SAE horsepower). Mistakes in units or conversion factors can lead to drastically incorrect horsepower figures.
- Underlying Engine Issues: While less likely if the car seems to run normally, consistently low horsepower readings could indicate an underlying engine problem. However, this would usually be accompanied by other symptoms and potentially error codes.
Likely Scenario: The “80hp” reading is likely a misinterpretation of OBDII data, possibly observed at low engine load or using a less accurate calculation method. It’s not indicative of the Miata’s actual peak horsepower, especially after intake modifications.
Focus on Performance Gains, Not Just Numbers
Instead of fixating on a potentially misleading OBDII horsepower reading, focus on the real-world performance improvements from intake modifications. A well-designed intake can offer:
- Improved Throttle Response: Slightly quicker engine reaction to throttle input.
- Enhanced Engine Sound: A more aggressive and sporty intake note.
- Marginal Horsepower Gains (at higher RPM): Potentially a few extra horsepower at the top end of the RPM range, though gains are often modest with intake-only modifications on a Miata.
Conclusion: Optimizing Your Miata Intake for Performance
For Miata owners looking to modify their intake, the key takeaways are:
- Prioritize Function Over Form: Focus on designs that provide cold air and minimize heat soak, rather than just aesthetic appeal.
- Retain Key Components (Resonator, MAF/IAT Sensor Integration): Understand the purpose of factory components and ensure proper integration in any modification.
- Heat Shielding is Essential: A cool box or heat shield is crucial to realize any performance benefits from an aftermarket intake.
- OBDII Readings as a Guide, Not Gospel: Use OBDII data for monitoring, but understand its limitations and potential for misinterpretation, especially for calculated horsepower figures.
By focusing on sound principles of intake design and understanding the nuances of OBDII data, you can optimize your Miata’s intake for improved performance and driving enjoyment, without getting misled by potentially inaccurate horsepower readings.
