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Several guys have said their first mod will be to de-activate the valve on the muffler. I assumed its purpose is to satisfy a sound certification at partial throttle positions, but I've also seen it posted that it is to maximize low RPM torque.(thats one reason an 8L Viper has a 2.25 inch exhaust as OEM) Anyone able to enlighten us on this?
 

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Ferrari has done the same thing on some cars to maintain low end torque. Exhaust opens up at higher rpm. With 3 inch pipes on the street this set up makes sense. IMHO.
 

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i was thinking the same thing. i'm sure within a short period of time we'll see dyno sheets with it stock and with the thing open the whole time.
 

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I don't think I'm going to disable mine. Here's why.
Engines produce more torque at lower rpms with a little back pressure but produce more hp up top when the exhaust flows freely. I think this is nice because it gives us the best of both worlds. Part throttle will have more back pressure while WOT will induce free flowing thus creating more HP. ;)
 

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petegtsv10 said:
measure your pipes....
Here was the confusion....

From the headers to the resonators, the exhaust pipes are 2.50" in diameter. From the resonators to the muffler, the exhaust pipes are 2.25" in diameter. I assumed they were 2.5 the whole way, but they do shrink to 2.25. In any case, I've got 3' the whole way which I've found to be only advantages. It's amazing how good the Viper sounds with a aftermarket exhaust, when stock it is just so-so.
 

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PerforminNorman said:
I don't think I'm going to disable mine. Here's why.
Engines produce more torque at lower rpms with a little back pressure but produce more hp up top when the exhaust flows freely. I think this is nice because it gives us the best of both worlds. Part throttle will have more back pressure while WOT will induce free flowing thus creating more HP. ;)
I'm with you on that one Norman! :thumb:

BTW, I meant to quote you not edit you on your post. In case you were wondering.
 

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The new beast is a very sophisticated piece of engineering. I would mess with it only if equally sophisticated engineering went into the mods, IMHO. This is not a 1973 Camaro Z28 350 we are talking about here. If I get one, I doubt I'll mod it at all.
 

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The new beast is a very sophisticated piece of engineering. I would mess with it only if equally sophisticated engineering went into the mods, IMHO. This is not a 1973 Camaro Z28 350 we are talking about here. If I get one, I doubt I'll mod it at all.

RIGHT ON!!!
 

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me...I just like it because of the sound :D But I have the mild to wild switch on mine.
 

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The new beast is a very sophisticated piece of engineering. I would mess with it only if equally sophisticated engineering went into the mods, IMHO. This is not a 1973 Camaro Z28 350 we are talking about here. If I get one, I doubt I'll mod it at all.
If I get one, I doubt I'll mod it at all.


:lol:Easier said than done :yeadog:.

I take the fuse out on the track because It would always be opening and closing and may wear it out sooner and may be delayed in openning and slow me by that 0.00001 sec / 1000000 miles. Oh, and it sounds better. I doubt the torque is any worse with them open as the stock exhaust (and cats) probably have plenty of back-pressure. May be true for freer flowing systems. I don't know though.
 

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Several guys have said their first mod will be to de-activate the valve on the muffler. I assumed its purpose is to satisfy a sound certification at partial throttle positions, but I've also seen it posted that it is to maximize low RPM torque.(thats one reason an 8L Viper has a 2.25 inch exhaust as OEM) Anyone able to enlighten us on this?
I actually tested this on the dyno, and open made about 8 more ft lbs of torque than closed. Two runs, back to back, from same ECT and RPM, the open flap made more power till the computer opened the flap, then both runs were the same.
 

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I actually tested this on the dyno, and open made about 8 more ft lbs of torque than closed. Two runs, back to back, from same ECT and RPM, the open flap made more power till the computer opened the flap, then both runs were the same.
By any chance do you have a dyno graph showing the comparison of fuse?

I assumed a dyno pull is done at WOT, so the valves would be open the whole time during the test, so how could there be any difference? Or, are you saying the test occurred at only partial throttle and you saw a difference in TQ below 3500rpm?
 

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Dyno at WOT, part throttle might favor closed exhaust, don't know there.

When the valve is closed it is controlled by the PCM and opens at 3500 rpm and WOT, so the only difference is below 3500 rpm, and open definetily mde more power.
 

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Just pulled my fuse, and... Yeah, she breathes easier, and loves it! Throttle response and low end torque seem to be enhanced too. Love it, now for Airaid intake, and she's good to go screamin fast!!!
 

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I dynoed mine from 2000 rpm and on and when the computer opened the valve HP and TQ jumped up about 5 rwhp and 5 rwtq. Corvettes of Dallas has a mod where they cut open the muffler and remove the baffle and they got another 5 rwhp from that.
It was very noticable on the graph, the jump in power when it opens up!
 
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