991.1 overrun (pops & crackles) vs none in gt3
07-01-2017, 12:41 PM
#31
Rocky Mountain High
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The first time that I ever heard loud overrun pops and gurgles from a street car was the first time that I drove a Ferrari 458. I thought it was awesome. It reminded me of the noises that you hear from F1 cars. Now it seems that most performance car manufacturers are adding this "feature" to their cars.
07-01-2017, 01:01 PM
#32
Technical Guru
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The GT3 has only one sound "symposer" versus two in the regular 991.2 models, the 2nd being enabled in sport mode. To improve throttle response the turbo engines are also now briefly leaving the throttle open and turning off the injectors when you take your foot off the pedal which contributes to it.
Last edited by JasonAndreas; 07-03-2017 at 06:53 PM.
07-01-2017, 01:02 PM
#33
IMO this was probably a normal thing back in the days of carburetors (the inertia of fuel in motion in the metering system) and perhaps in the days of manifold fuel injection. But these days with computer controlled direct fuel injection it's just not necessary nor the result of normal ECU programming but rather intentional dramatics for the benefit of drivers who like the sounds.
It could be eliminated if manufacturers wanted to. Porsche actually HAS eliminated it in Sport+ mode in the 991.2 series turbo engines (done there for other reasons - ie reduced turbo lag).
07-02-2017, 12:43 AM
#34
RL Community Team
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I never liked the crackle/pops but I discovered an obvious workaround--just turn off PSE. The valves open anyway above 3-4k or whatever it is, and it seems like there's a lot less fake popping going on.
And I might be crazy but it feels to me like at low RPMs the engine is more responsive with the valves closed? With a manual at least, put it in sport or sport plus, press the exhaust button to turn it off (which isn't off, just means keep them closed at lower RPMs), and compare to when it's on. This is also on the .1 GTS, so NA engine, powerkit etc.
And I might be crazy but it feels to me like at low RPMs the engine is more responsive with the valves closed? With a manual at least, put it in sport or sport plus, press the exhaust button to turn it off (which isn't off, just means keep them closed at lower RPMs), and compare to when it's on. This is also on the .1 GTS, so NA engine, powerkit etc.
07-02-2017, 12:48 AM
#35
RL Community Team
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The GT3 has only one sound "symposer" versus two in the regular models, the 2nd being enabled in sport mode. To improve throttle response the turbo engines are also now briefly leaving the throttle open and turning off the injectors when you take your foot off the pedal which contributes to it.
07-02-2017, 12:53 AM
#36
Rennlist Member
07-04-2017, 10:24 PM
#37
Rocky Mountain High
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Rennlist Member
I drove the turbo in "normal" mode for a while today. There were very few pops and crackles in normal driving. However, if I accelerated hard and then abruptly released the throttle, there were several loud pops. It's apparently never completely off.
Happy Independence Day everyone!
Happy Independence Day everyone!
07-04-2017, 11:50 PM
#38
Rennlist Member
Here is an article that explains Jaguar's backfire technology.
"Jaguar engineers achieved this by defying convention. "Usually you’d cut the fuel to the cylinders, when the driver lifts off the accelerator," explained Andrew Lowis, the Gasoline Calibration Manager for the car. "We are delaying the point when we do that and igniting later than we might in normal circumstances. It produces a controlled misfire."
Obviously, the car must still meet emissions regulations despite the intentional introduction of pollutants to the exhaust stream. "It is a challenge, but it is one we can achieve by careful calibration," said Lowis. In fact, Jaguar has more stringent internal emissions limits than the government applies, he said, and the car meets those, too."
"'Theater' is a great word," noted Kevan Richardson, Program Manager for Jaguar sports cars. “We want the car to be entertaining. ... It is all part of the show."
"Jaguar engineers achieved this by defying convention. "Usually you’d cut the fuel to the cylinders, when the driver lifts off the accelerator," explained Andrew Lowis, the Gasoline Calibration Manager for the car. "We are delaying the point when we do that and igniting later than we might in normal circumstances. It produces a controlled misfire."
Obviously, the car must still meet emissions regulations despite the intentional introduction of pollutants to the exhaust stream. "It is a challenge, but it is one we can achieve by careful calibration," said Lowis. In fact, Jaguar has more stringent internal emissions limits than the government applies, he said, and the car meets those, too."
"'Theater' is a great word," noted Kevan Richardson, Program Manager for Jaguar sports cars. “We want the car to be entertaining. ... It is all part of the show."
07-05-2017, 10:33 AM
#39
Three Wheelin'
07-05-2017, 02:54 PM
#40
It's the same way on the .1 as well. The valves open under hard acceleration whether you have PSE turned on or not.
07-05-2017, 02:55 PM
#41
Since my last servicing, the pops and gurgles on decal seem much lower than before. Maybe a software update. I prefer it like that, as I'm not a fan of them when they're so loud they sound overly artificial. Still have a very nice rumble and screams under load, just not as much of the farts and pops on decel.
07-05-2017, 03:05 PM
#42
Rennlist Member
Personally, I agree the GT3 is more muted at lower rpm than my C2 with the AWE bypass on it. There is one element to the acoustics of the GT3 that no exhaust can replace or enhance - the sound between 8-9,000 rpm.