3onTree
Donating Member
- Joined
- Jul 5, 2010
- Messages
- 87
- Reaction score
- 11
- Points
- 8
- Location
- Melbourne
- Members Ride
- SSV Redline Sportswagon
Sharing recent experience sorting out my bimodal exhaust on my SSV (HM Headers aftermarket system).
Most bi modal exhaust systems, use a vacuum controlled valve in the rear mufflers to divert exhaust gases to baffled sections of the muffler and to alternatively bypass the baffles and shoot exhaust gases straight out, at full noise. Controlling this system is an electric vacuum solenoid valve. Simply, when it receives voltage, it opens vacuum to the second vacuum hose output, to vacuum charge the system and open or close the muffler exhaust valve. This is the same solenoid type that is used to actuate boost controllers in turbos. Now to diagnose: sharing the following:
1. Check voltage on the vacuum solenoid valve (normally in the engine bay) to see if your issue is electrical. In a normally open bypass valve system, voltage is needed to open vacuum to the output side of the vacuum circuit to close the muffler valve. The electronics in the RPM module automates the opening and closing of the vacuum solenoid valve - normally based on rpm.
2. Check vacuum on the supply side, normally T branched off vacuum lines off the master cylinder. To check, remove the vacuum hose from the solenoid valve and attach it to a tool like a brake fluid suction tool - these are normally used to suck brake fluid from brake calipers - and are cheaply available on ebay. There is normally a pressure dial on this tool. Check to see vacuum on the supply side. All being well insert the brake fluid sucker on the output hose that leads to your mufflers and pump the handle. If the system holds vacuum, then you have no leaks and your issue is your valves or electrical control of the vacuum solenoid valve. My case, the vacuum lines had perished due to nearby exhaust radiant heat between the mufflers. After replacing the vacuum lines , I pinched the vacuum lines putting the under body panels on, so look out for pinches.
Finally, I recommend getting shielding like insulation tape or other heat reflective / shielding conduit so the vacuum lines don’t fail again. Here are some pics.
Most bi modal exhaust systems, use a vacuum controlled valve in the rear mufflers to divert exhaust gases to baffled sections of the muffler and to alternatively bypass the baffles and shoot exhaust gases straight out, at full noise. Controlling this system is an electric vacuum solenoid valve. Simply, when it receives voltage, it opens vacuum to the second vacuum hose output, to vacuum charge the system and open or close the muffler exhaust valve. This is the same solenoid type that is used to actuate boost controllers in turbos. Now to diagnose: sharing the following:
1. Check voltage on the vacuum solenoid valve (normally in the engine bay) to see if your issue is electrical. In a normally open bypass valve system, voltage is needed to open vacuum to the output side of the vacuum circuit to close the muffler valve. The electronics in the RPM module automates the opening and closing of the vacuum solenoid valve - normally based on rpm.
2. Check vacuum on the supply side, normally T branched off vacuum lines off the master cylinder. To check, remove the vacuum hose from the solenoid valve and attach it to a tool like a brake fluid suction tool - these are normally used to suck brake fluid from brake calipers - and are cheaply available on ebay. There is normally a pressure dial on this tool. Check to see vacuum on the supply side. All being well insert the brake fluid sucker on the output hose that leads to your mufflers and pump the handle. If the system holds vacuum, then you have no leaks and your issue is your valves or electrical control of the vacuum solenoid valve. My case, the vacuum lines had perished due to nearby exhaust radiant heat between the mufflers. After replacing the vacuum lines , I pinched the vacuum lines putting the under body panels on, so look out for pinches.
Finally, I recommend getting shielding like insulation tape or other heat reflective / shielding conduit so the vacuum lines don’t fail again. Here are some pics.
Attachments
Last edited: