Why is there no sound at high RPM after modifying the exhaust?
4 Answers
Due to the presence of sound-absorbing cotton, there is no sound at high RPM. Here is more relevant information: 1. Only modifying exhaust backpressure: Simply modifying the exhaust backpressure and changing it to a straight pipe can increase the upper limit of the engine's net power output at high RPM. However, the improvement effect is not significant, generally ranging from 5% to 10%, which means recovering the power lost due to the original exhaust backpressure, and it only takes effect at high RPM. 2. Modifying backpressure combined with ECU tuning: This stage marks the entry into the threshold of modification. ECU tuning can increase net power output, and when combined with low backpressure, it can further expand the range of net power output, allowing the vehicle's performance to be further enhanced.
After modifying the exhaust, my car didn't produce sound at high RPMs, and I went through a major repair. Inspection revealed that a massive muffler was used in the mid-section of the exhaust, swallowing all the sound; the exhaust pipe diameter was as small as a funnel, causing airflow blockage at high RPMs and preventing proper release. During installation, the workers were careless—joints weren't sealed properly, leading to severe leaks that reduced noise. Later, I learned that exhaust modifications must match the engine's displacement—too small, and airflow gets restricted. The ECU might also struggle to adapt, requiring a retune of the computer parameters. I recommend choosing a straight pipe or a minimal muffler system, measuring dimensions carefully before installation, and avoiding cheap, low-quality parts. During test drives, avoid risky high-speed testing—safety first—and preferably have a reputable shop double-check the work. Regular exhaust maintenance can prevent sudden failures.
The common reasons for modified exhaust systems not being loud at high RPMs can be categorized into several types. Installation issues are the most frequent: loose connections or insufficient sealant causing air leaks and sound loss; exhaust pipes that are too narrow, restricting airflow and preventing loud high-RPM sounds. Poorly designed mufflers, either too thick or made of highly sound-absorbent materials, can also dampen all exhaust notes. Choosing the wrong aftermarket parts is another common issue, such as purchasing cheap counterfeit parts with excessive internal silencing or engines with insufficient output affecting airflow. Sometimes, the ECU settings are not updated, leading the system to mistakenly enforce quiet operation. For DIY modifications, it is recommended to match the vehicle's characteristics: accurately measure pipe diameters and select an appropriate silencing level. Ensure tight installation and proper sealing with tape. Test at low speeds before high-RPM runs to avoid safety hazards. If high-RPM performance is poor, first check for leaks and exhaust system integrity.
While modifying the exhaust system to pursue a roaring sound, having it remain quiet at high RPMs might actually be a good thing. Reasons include optimized exhaust design with effective noise reduction, high-quality materials for superior sound insulation, or loose installation causing excessive air leakage and dispersed airflow, resulting in less noise. An oversized muffler or narrow pipe diameter can also suppress noise, creating a quieter ride. Vehicle engine characteristics, such as a small-displacement engine paired with an oversized exhaust system, may lead to insufficient airflow at high RPMs, resulting in less sound. However, if the installation is incorrect, it's advisable to check sealing and exhaust compatibility: pipe dimensions should be appropriate—not too narrow—and connections should be tight. A quieter exhaust benefits noise reduction compliance and ensures safer, less disruptive driving. Regularly inspect the exhaust system and address any issues promptly.
