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stealthy1ss
10-23-2008, 06:07 PM
Is the butterfly valve in the exhaust controlled by the PCM?
Adamsy87
10-24-2008, 01:41 AM
not sure. I do know that on my boss's car all we had to do was pull a fuse and they now stay open all the time.
BAD LS1
10-24-2008, 06:32 AM
yeah the "NPP" exhaust, by like 3500 rpms it opens valves in the muffler and is pretty much a straight pipe.
TransAm12sec
10-24-2008, 03:48 PM
"The system is controlled by the Exhaust Flow Control Module (EFCM). When the engine is running the EFCM commands the vacuum solenoid ON, which in turn results in engine vacuum being sent to the exhaust valves, thus holding them closed.

When engine speed exceeds 3,500 rpm, or throttle position is equal to or greater than 25 percent, the EFCM commands the vacuum solenoid OFF and the exhaust valves open.

The system is not as simple as it may appear because in addition to the EFCM it also uses the ECM (AKA "PCM"), BCM, EBCM and the serial data circuit. It also uses the exhaust flow control valve vacuum solenoid; vacuum reservoir, vacuum lines and the two exhaust control valves."

http://www.z06vette.com/forums/f64/exhaust-valve-wont-close-112369/
stealthy1ss
10-24-2008, 08:56 PM
"The system is controlled by the Exhaust Flow Control Module (EFCM). When the engine is running the EFCM commands the vacuum solenoid ON, which in turn results in engine vacuum being sent to the exhaust valves, thus holding them closed.

When engine speed exceeds 3,500 rpm, or throttle position is equal to or greater than 25 percent, the EFCM commands the vacuum solenoid OFF and the exhaust valves open.

The system is not as simple as it may appear because in addition to the EFCM it also uses the ECM (AKA "PCM"), BCM, EBCM and the serial data circuit. It also uses the exhaust flow control valve vacuum solenoid; vacuum reservoir, vacuum lines and the two exhaust control valves."

http://www.z06vette.com/forums/f64/exhaust-valve-wont-close-112369/


Damn, my idea will not work them.
A B4C Z
10-27-2008, 12:28 AM
Pretty sure you can just yank the vacume line off the valve and it will stay open all the time.
stealthy1ss
10-27-2008, 06:45 PM
Pretty sure you can just yank the vacume line off the valve and it will stay open all the time.

What I want to do is stay somewhat quiet but have it open up when I get on it. With my little ass 122ci motor it needs backpressure in the low end but there is a lot to gain in the upper end with it wide open. This idea is still on the table, I just need to figure out how i can control the valve without pushing a button. Right now I am thinking about hooking it up kind of like you would with a meth pump.
WhatsADSM
10-27-2008, 11:52 PM
You just need an RPM based switch? Something like an window switch for nitrous would work. They even make TPS + RPM switches:
http://store.summitracing.com/partdetail.asp?autofilter=1&part=NOS-15982NOS&N=700+4294849264+115&autoview=sku
TransAm12sec
10-28-2008, 02:26 PM
With my little ass 122ci motor it needs backpressure in the low end but there is a lot to gain in the upper end with it wide open.

Backpressure is bad, velocity is good.

http://www.miata.net/garage/KnowYourCar/S4_Back.html
http://www.dsmtuners.com/forums/frequently-answered-dsm-questions/168578-exhaust-straight-scoop-backpressure.html