Sound impact
10-01-2015, 10:14 AM
#17
Former Vendor
With a valved side muffler bypass the opening and closing of the valves is barely noticeable. It's a linear transition.
If you a running a stock setup and don't like the defined opening and closing point you can have the valves bypassed. This also sounds good with a center muffler bypass. The drone is minimal and completely tolerable.
With single piped straight side deletes there is drone.
If you a running a stock setup and don't like the defined opening and closing point you can have the valves bypassed. This also sounds good with a center muffler bypass. The drone is minimal and completely tolerable.
With single piped straight side deletes there is drone.
10-01-2015, 10:33 AM
#18
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The valves are controlled by the DME in the 991, just like it was on the 997. The DME tells the valves to open and close at specified engine speeds - that's it.
From Porsche Literature:
Like its predecessor, the 911 GT3 (991) has a function for increasing torque in the
middle rpm range. This function is not activated by pressing a SPORT button as was
the case for the previous model, but instead using the button with the twin tailpipe
symbol (1) in the center console. When this button is pressed, the torque is
increased in the middle rpm range. The exhaust backpressure in the variable
exhaust system is additionally reduced and the gas cycle is improved, resulting in a
noticeable boost in torque in the rpm range between approximately. 3,000 and
4,000 rpm. The torque levels are increased by between approximately 22 and 26 ft.
lb. (30 and 35 Nm). The maximum torque of 325 ft. lb. (440 Nm) at 6,250 rpm
remains unchanged.
The switching point of the exhaust flaps depends on the load and engine speed. As
on the 997 GT3 II, the switching point from closed to open at full throttle is 3,200
rpm (exhaust flap button (1) pressed) and 4,000 rpm (exhaust flap button (1) not
pressed).
From Porsche Literature:
Like its predecessor, the 911 GT3 (991) has a function for increasing torque in the
middle rpm range. This function is not activated by pressing a SPORT button as was
the case for the previous model, but instead using the button with the twin tailpipe
symbol (1) in the center console. When this button is pressed, the torque is
increased in the middle rpm range. The exhaust backpressure in the variable
exhaust system is additionally reduced and the gas cycle is improved, resulting in a
noticeable boost in torque in the rpm range between approximately. 3,000 and
4,000 rpm. The torque levels are increased by between approximately 22 and 26 ft.
lb. (30 and 35 Nm). The maximum torque of 325 ft. lb. (440 Nm) at 6,250 rpm
remains unchanged.
The switching point of the exhaust flaps depends on the load and engine speed. As
on the 997 GT3 II, the switching point from closed to open at full throttle is 3,200
rpm (exhaust flap button (1) pressed) and 4,000 rpm (exhaust flap button (1) not
pressed).
10-01-2015, 12:51 PM
#19
Rennlist Member
10-02-2015, 02:17 AM
#20
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10-02-2015, 12:10 PM
#21
Rennlist Member
If you delete the side mufflers, you get even more power/torque between 3-5k, at the expense of less power/torque below 3k rpm. Above 5k, you get slightly more power/torque without side mufflers, but the difference is very minor - I would call it a wash.
As soon as you delete the side mufflers, you exhaust button no longer has any function (unless you have some of the valved bypass pipes which I have no experience with and have never seen any kind of dyno charts from any of the vendors).
The only way to significantly increase peak power and peak torque is to go with high flow cats. These occur at approx. 8.5k and 6.5k rpm engine speeds, respectively.
As soon as you delete the side mufflers, you exhaust button no longer has any function (unless you have some of the valved bypass pipes which I have no experience with and have never seen any kind of dyno charts from any of the vendors).
The only way to significantly increase peak power and peak torque is to go with high flow cats. These occur at approx. 8.5k and 6.5k rpm engine speeds, respectively.
10-02-2015, 12:45 PM
#22
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If you delete the side mufflers, you get even more power/torque between 3-5k, at the expense of less power/torque below 3k rpm. Above 5k, you get slightly more power/torque without side mufflers, but the difference is very minor - I would call it a wash.
As soon as you delete the side mufflers, you exhaust button no longer has any function (unless you have some of the valved bypass pipes which I have no experience with and have never seen any kind of dyno charts from any of the vendors).
The only way to significantly increase peak power and peak torque is to go with high flow cats. These occur at approx. 8.5k and 6.5k rpm engine speeds, respectively.
As soon as you delete the side mufflers, you exhaust button no longer has any function (unless you have some of the valved bypass pipes which I have no experience with and have never seen any kind of dyno charts from any of the vendors).
The only way to significantly increase peak power and peak torque is to go with high flow cats. These occur at approx. 8.5k and 6.5k rpm engine speeds, respectively.
10-02-2015, 06:10 PM
#23
Rennlist Member
10-02-2015, 06:38 PM
#24
Rennlist Member
Tubi Style. The TPC unit is a more cost effective unit of similar construction.
I would be interested in hearing feedback from those who installed a valved bypass. I suspect that it would be very slightly quieter with the valves closed and potentially have more power below 3k rpm, compared to a typical bypass pipe.
I would be interested in hearing feedback from those who installed a valved bypass. I suspect that it would be very slightly quieter with the valves closed and potentially have more power below 3k rpm, compared to a typical bypass pipe.
10-02-2015, 07:05 PM
#25
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i recently installed the 997 cup exhaust on my 991 gt3. (fits nicely)
which is a side muffler delete and valve delete as well. i do notice some torque loss below 3500 rpm. its not a huge difference, but its noticeable. above 3500-4000 rpm the acceleration seems to be about equal. but below 3500 rpm i would say you do lose some acceleration/torque.
however the trade off with the elimination of the annoying valves opening/closing and the gain of "maximum sound all the time" is well worth it, IMO.
as well the "crack" of the up-shifts with the cup exhaust are addictive. and the downshifts even below 2000 rpm are huge fun,. because you have the full deep exhaust note all the way down to idle. the car sounds more like a 997 with this exhaust.
10-02-2015, 08:26 PM
#26
Nordschleife Master
i certainly didn't read your entire post, but im not so sure about your above statement.
i recently installed the 997 cup exhaust on my 991 gt3. (fits nicely)
which is a side muffler delete and valve delete as well. i do notice some torque loss below 3500 rpm. its not a huge difference, but its noticeable. above 3500-4000 rpm the acceleration seems to be about equal. but below 3500 rpm i would say you do lose some acceleration/torque.
however the trade off with the elimination of the annoying valves opening/closing and the gain of "maximum sound all the time" is well worth it, IMO.
as well the "crack" of the up-shifts with the cup exhaust are addictive. and the downshifts even below 2000 rpm are huge fun,. because you have the full deep exhaust note all the way down to idle. the car sounds more like a 997 with this exhaust.
i recently installed the 997 cup exhaust on my 991 gt3. (fits nicely)
which is a side muffler delete and valve delete as well. i do notice some torque loss below 3500 rpm. its not a huge difference, but its noticeable. above 3500-4000 rpm the acceleration seems to be about equal. but below 3500 rpm i would say you do lose some acceleration/torque.
however the trade off with the elimination of the annoying valves opening/closing and the gain of "maximum sound all the time" is well worth it, IMO.
as well the "crack" of the up-shifts with the cup exhaust are addictive. and the downshifts even below 2000 rpm are huge fun,. because you have the full deep exhaust note all the way down to idle. the car sounds more like a 997 with this exhaust.
10-02-2015, 09:32 PM
#27
Rennlist Member
i certainly didn't read your entire post, but im not so sure about your above statement.
i recently installed the 997 cup exhaust on my 991 gt3. (fits nicely)
which is a side muffler delete and valve delete as well. i do notice some torque loss below 3500 rpm. its not a huge difference, but its noticeable. above 3500-4000 rpm the acceleration seems to be about equal. but below 3500 rpm i would say you do lose some acceleration/torque.
however the trade off with the elimination of the annoying valves opening/closing and the gain of "maximum sound all the time" is well worth it, IMO.
as well the "crack" of the up-shifts with the cup exhaust are addictive. and the downshifts even below 2000 rpm are huge fun,. because you have the full deep exhaust note all the way down to idle. the car sounds more like a 997 with this exhaust.
i recently installed the 997 cup exhaust on my 991 gt3. (fits nicely)
which is a side muffler delete and valve delete as well. i do notice some torque loss below 3500 rpm. its not a huge difference, but its noticeable. above 3500-4000 rpm the acceleration seems to be about equal. but below 3500 rpm i would say you do lose some acceleration/torque.
however the trade off with the elimination of the annoying valves opening/closing and the gain of "maximum sound all the time" is well worth it, IMO.
as well the "crack" of the up-shifts with the cup exhaust are addictive. and the downshifts even below 2000 rpm are huge fun,. because you have the full deep exhaust note all the way down to idle. the car sounds more like a 997 with this exhaust.
10-02-2015, 10:18 PM
#28
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as far as i know, there will be no impact on warranty (when does a simple exhaust install ever void a warranty anyway?)
especially since its an OEM part and he Porsche dealer installed it for me.
unless youre talking about the warranty on the exhaust itself of course.
especially since its an OEM part and he Porsche dealer installed it for me.
unless youre talking about the warranty on the exhaust itself of course.