Muffler bypass switch on vs off - more power?

[Wryfox]

Tried searching this topic here many ways but come up with nothing.

Is there more power with the exhaust bypass on?

 

[BarneyM]

Tried searching this topic here many ways but come up with nothing.

Is there more power with the exhaust bypass on?

No.

 

[Overkill]

I wouldn't think there would be a power difference when stomping on it since all it does is block the vacuum signal that is coming from the engine and that vacuum signal goes away when you are on the gas hard. So, the exhaust would be open no matter if you had the switch off or on when stomping it so no difference there. Just normal driving where the exhaust is closed when the switch is off, could theoretically be different power. But, I would think it wouldn't be much difference.

 

[Wryfox]

I wouldn't think there would be a power difference when stomping on it since all it does is block the vacuum signal that is coming from the engine and that vacuum signal goes away when you are on the gas hard. So, the exhaust would be open no matter if you had the switch off or on when stomping it so no difference there. Just normal driving where the exhaust is closed when the switch is off, could theoretically be different power. But, I would think it wouldn't be much difference.

Thanks, didn't know the valve opened under full power automatically. I've never run it in closed mode

 

[OldVetteGuy]

Interesting, so if you don't care about the extra power (if there actually is any) and all you want is quiet tie wrap the valve closed, this way the exhaust note and noise never changes. I might just have to try this. So this brings another question, does this opening happen because of vacuum loss at full throttle? If so, maybe Jeep should have used and electric actuator instead of vacuum. lol

 

[Viking Jeeper]

Interesting, so if you don't care about the extra power (if there actually is any) and all you want is quiet tie wrap the valve closed, this way the exhaust note and noise never changes. I might just have to try this. So this brings another question, does this opening happen because of vacuum loss at full throttle? If so, maybe Jeep should have used and electric actuator instead of vacuum. lol

Im thinking it was done on purpose with the vacuum so it would always be open at full throttle.

 

[riverjeep]

So this brings another question, does this opening happen because of vacuum loss at full throttle? If so, maybe Jeep should have used and electric actuator instead of vacuum. lol

My theory is that it does, vacuum always drops under hard acceleration. This is also why during initial startup the exhaust is always louder until the vacuum builds and closes the valves.

 

[riverjeep]

Tried searching this topic here many ways but come up with nothing.

Is there more power with the exhaust bypass on?

No, the valves open under hard acceleration.

 

[Winston]

All the manual mentions is that the valves will be commanded open at high engine speeds and loads.

 

[Huckle Monster]

Yes, it adds 20 HP. Anyone stating otherwise probably has a duck on their dash.

 

[OldVetteGuy]

Yes, it adds 20 HP. Anyone stating otherwise probably has a duck on their dash.

I would absolutely love to see dyno results for both HP and torque, sometimes reducing back pressure also reduces torque.
I won't hold my breath on the results though, lol

No ducks on my dash, my 2018 JLUR use to get lots of ducks, my 392 is nearly identical including the color but the 392 gets none. Maybe the 392 is eating them when im not watching. haha

 

[Huckle Monster]

I would absolutely love to see dyno results for both HP and torque, sometimes reducing back pressure also reduces torque.
I won't hold my breath on the results though, lol

No ducks on my dash, my 2018 JLUR use to get lots of ducks, my 392 is nearly identical including the color but the 392 gets none. Maybe the 392 is eating them when im not watching. haha

As they say, your results may vary. FWIW, I have one duck on my dash and it's from a niece, so it's staying.

 

[station378]

I haven’t seen any measurable gains with the bypass open. It definitely feels quicker because of the sound, but on the 392 the valves are really there for tone more than power. At wide open throttle they’re open anyway, so the ECU isn’t holding anything back. If there’s any difference, it’s tiny and mostly just the louder exhaust tricking your brain

 

[YGBSM]

Yes, it adds 20 HP. Anyone stating otherwise probably has a duck on their dash.

And it adds 1 mpg to the fuel economy.

 

[Bhodi11]

Certain there is zero HP difference but I have noticed it’s more snappy off the line with the exhaust open vs closed. Eventually it will open on its on if you get on it enough. So I am not saying gunning it but some light spirited driving. There is a difference 100% you are not imagining it.

 

[guruman]

I haven’t seen any measurable gains with the bypass open. It definitely feels quicker because of the sound, but on the 392 the valves are really there for tone more than power. At wide open throttle they’re open anyway, so the ECU isn’t holding anything back. If there’s any difference, it’s tiny and mostly just the louder exhaust tricking your brain

Technically at anything less than WOT (and during the delay on opening the valves after you peg WOT) the closed valves will add some amount of back pressure. that added back pressure should affect power and mileage a tiny bit.