Hi All,
I've shared this post in a FaceBook group and I thought it was about time I posted it here. This is a “comprehensive” analysis / review (ie. a long post). A “Too Long Didn’t Read” is at the bottom of this post. Disclaimer - I am not an engineer nor do I pretend to be one. This is a review / solution based on my personal experience and research.
Like some of you, I have removed my mid muffler/ resonator (whatever you want to call it) and replaced it with an X-Pipe. As a result, I have experienced exhaust valve rattle in Comfort and Auto mode while under load between 1,500 - 2,000 RPM while the valves are closed (at a certain threshold, the computer opens the valves). I’ve searched for a solution and I believe I have found one.
The B9 S4 (and I believe the S5, SQ5 and many other Audi/VW Group vehicles) uses a Küster manufactured exhaust valve actuator. These exhaust actuators work via a servo motor turning a screw shaft, which turns a gear, which turns a coiled spring, which turns the exhaust valve (see image). Küster is a valve actuator supplier for many auto manufactures and their valve actuators are used by Dodge, Ford, Audi, Volvo, Mercedes, and many others. However, their valves are prone to rattle due to an engineering design choice / flaw.
These actuators work as required under stock / OEM conditions but when exposed to enhanced / elevated exhaust “flow” they tend to rattle while in the closed position. The rattle is due to the play between the valve connecting shaft and the shaft opening hole to the actuator. As flow increases, it causes increased pressure on the closed valve and causes the shaft to bang against the opening for said shaft.
During my research, I was able to track down a Dodge Charger / Challenger Forum that discussed valve rattle on Chargers and Challengers that had the “active exhaust” equipped in 2015 / 2016 model year (Dodge active exhaust uses the same actuators as Audi). These forums discussed the rattle being due to broken coil springs, lack of downward pressure from OEM springs, and elevated flow when mid mufflers were removed. The largest contributor to the rattle were the broken springs. The springs, according to the forum, broke due to the heat exchange between the exhaust pipe and the spring itself - which ultimately brittled the metal leading to the breakage.
Dodge, becoming aware of this issue, contracted with Küster to manufacture “taller” and more robust springs to aid in this heat transfer starting with the 2016/ 2017 model year. As a result, breakages were less common and rattle was essentially eliminated due to increased spring pressure.
I’ve seen on the FaceBook groups and Audi forums that stretching the OEM spring helps but the issue comes back in a few weeks. This, in my opinion, is due to the initial state of the OEM spring being compressed and when stretched, the spring will attempt to revert back to its original form (and overtime it will). I have also seen a replacement spring manufactured by ASR used but the issue comes back with this spring as well. The reasoning, in my opinion, is because the ASR spring maintains the same pressure (ie. same height) as OEM and only simplifies the coils. THE SOLUTION, is to purchase a spring that is already stretched from the factory / applies more downward pressure.
Enter the DODGE spring. Because of Dodges change in spring design, they have created a spring, that when compressed in the B9 actuator housing, applies more constant increased pressure (over OEM). This increase of pressure causes the valve to stay in a more controlled / solid place while closed resulting in less / full reduction of rattle.
The upgraded springs fit the OEM actuators perfectly since they come from the same manufacturer and the install did not take long. The car does not need to be lifted but it would certainly help if you’re not okay with working in tight spaces. To make thing even simpler, I would suggest removing the entire rear muffler section if possible (but this will add additional time and steps.
I have included the DODGE part number below as well as the website I purchased the spring from. I supported a local small business that sells them in a pair and I would encourage you to do the same - if you are willing to spend a bit ($10) more. I have also included images of the OEM springs vs the Dodge upgraded springs (Dodge being the taller spring) as well as the actuator for reference.
Since making this adjustment (in July of 2021), I have not had my rattle return (and I’m hoping it’s truly solved). I’ve put a couple hundred miles on the springs and actuated the valves as much as possible to ensure they’re broken in properly. While reading through comments on the FaceBook group, some have noted that their rattle still exists but at a much milder level after this install. Some have also suggested plastic heat wrapping the springs. I will not recommend the heat wrapping as I have not personally done it and I believe you may have an improper “seat” of the spring into the valve. As for those that still have a rattle, ensure your springs are properly seated in the valve during installation and allow for a break-in period. If the issue persists, your actual valve may be bad, especially if you have a fully stock system. As an additional suggestion - there are some “breather holes” on the base of the actuator housing plate (4 in total - you can’t miss them) that members of the DODGE community have said that spraying some white lithium grease into helped alleviate additional rattle until the grease eventually dries out and you need to add more. However, I have not tested this since my rattle has gone away.
TOO LONG DIDN’T READ (TL/DR): To fix the exhaust valve rattle you need to increase spring pressure. Stretching the spring will not work as the springs want to return to their manufactured state. Dodge sells “taller” springs from the factory and when placed in the exhaust valve actuator, they add enough pressure to stop the rattle. The DODGE part number is below. However, please consider supporting a small business and purchasing the pair from the company linked below.
DODGE part #: 68319331AA - fyi if you search this part number you may find images that look different to the ones posted. Those images on google are wrong. If anything, confirm with your local Dodge dealer or use the link below.
Link to website where I purchased: https://mfer-1.com/shop/ols/products...xhaust-springs
How to:
1) Check down both side of the exhaust to see that the valves are open (the driver side - for LHD vehicles - may be a bit hard to see at first)
2) Unbolt the actuator (requires a bit of yoga to get in comfortably if you don't have a lift) from the base. There are 3 nuts in total.
3) Remove the actuator by lifting up. No need to unplug the actuator.
4) Keep in mind the orientation on the spring that's currently attached to the actuator.
5) Remove the old spring and replace it with the new one placing it in the same orientation as the old one.
6) Reinstall the actuator ensuring that the spring properly seats itself in the valve head. Since this is a stronger spring it may take a bit of finessing or an extra hand to help hold it in place.
7) Before it's all tightened up, check the valve orientation again to make sure they're both still open.
8) If so, tighten it all up but be careful not to over-tighten as the plastic can split.
9) Turn your car on and cycle between comfort and dynamic/individual to check that the valves are working as intended.
225768430_3632646590169088_3346322678509297893_n.jpg
224472695_3632646683502412_2321784871037714976_n.jpg
225119902_3632646783502402_2937486098015187978_n.jpg
224418924_3632646736835740_8066073373603800189_n.jpg
224388705_3632646633502417_7483420739744291567_n.jpg
Reply With Quote
Originally Posted by awdconnor
Bookmarks