How to Solve CGW Exhaust Resonance?
3 Answers
To eliminate resonance, you can replace the original muffler and change both the mid and tail sections, using a silent muffler. Generally, the cause of resonance is that the muffler is too large, leading to insufficient exhaust flow, which results in turbulent exhaust gas inside the muffler. This turbulence impacts the edges of the muffler, causing the exhaust pipe to vibrate and subsequently leading to vehicle-wide resonance. The specific solutions are as follows: 1. Modify the muffler: For exhaust pipe resonance, you can change the muffler to a single-stage backpressure type and place steel wool inside the muffler. After this modification, the muffler's vibration frequency will change from vibrating three times per exhaust cycle to vibrating once. Additionally, the steel wool can absorb some of the exhaust energy, but its vibrations won't transfer to the muffler shell, significantly reducing the shell's vibrations compared to before the modification. 2. Exhaust resonance generally falls into three categories: The first is low-frequency resonance, which occurs at idle and below 2000 RPM. This is mainly caused by an improperly designed backpressure muffler that doesn't match the engine's RPM or issues with the flexible connection point in the header. The second is high-frequency resonance, which occurs above 2000 RPM or 3500 RPM, increasing with higher RPMs. This is usually due to poor car sound insulation, overly stiff vibration-damping hangers, thin exhaust pipe materials, or rough internal surfaces of the exhaust pipe. The third is hard connection resonance, which exists at all RPMs. This is typically caused by improper installation, where rigid connection points exist beyond the hangers, often seen in mismatched aftermarket exhaust systems.
I recently dealt with the resonance issue on my CGW exhaust system, and found that aftermarket exhausts most commonly develop a buzzing sound in the 2500-3500 RPM range. This is usually caused by improper exhaust pipe installation or worn-out hangers. Last week I helped my friend fix his old Focus - first we readjusted all exhaust hanger positions to ensure every joint was parallel and aligned, then replaced several rubber hangers with reinforced ones, and finally checked there was sufficient clearance between the exhaust pipes and chassis. The most extreme case was a heat shield aluminum plate that had gotten so hot from exhaust vibration it warped - just needed to pry it back into shape with a crowbar. Honestly many small modification shops don't understand the importance of proper exhaust angle adjustment. I'd recommend finding a truly experienced mechanic, though you can DIY if you have a car lift ready.
Speaking of exhaust resonance, I went through quite a bit of trouble when I installed the CGW mid-to-tail section on my car. Initially, once I hit 60 mph, the entire trunk would resonate, giving me a headache from the vibration. Later, I realized that during the modification, the exhaust pipe mid-section was too close to the subframe. The solution was actually quite simple: first, warm up the car for ten minutes to let the exhaust pipe fully expand, then jack it up and check all contact points. I recorded a video with my phone and found that the exhaust would scrape against the heat shield every time it vibrated. I simply inserted a high-temperature resistant silicone pad to separate them. Additionally, I replaced three reinforced hangers—remember to choose conical rubber ones as they are more durable than the stock ones. Now, when driving on the highway, it's so quiet that I can clearly hear the drum beats in the music.
