Preferred RPM range and turbo lag in base 991.2
02-02-2019, 04:26 PM
#61
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Did someone say turbos?
02-03-2019, 04:53 AM
#62
Instructor
Thread Starter
Does this mean that non-Sport mode is designed to feel like NA, as long as the driver is gentle on the throttle in the first half-second of acceleration? Sport feels like a different car, and fun in its own way. I'd rather take a little longer getting to 85mph and experience predictable, increasing rate of acceleration. If you can get past the slower initial response, non-Sport creates an illusion that the car is much faster all through the acceleration.
Last edited by tosha; 02-03-2019 at 01:30 PM.
02-03-2019, 12:40 PM
#63
Burning Brakes
It's actually just marketing simplification, putting a value that's easily understood by the average person. As you've found out, it's about impossible to hit the peak torque number at that engine speed in the car. Sure, it can be done on the engine dyno. The GTS is rated for peak torque at 2150rpm. So just comparing the base C to the GTS, you can easily see the GTS has more lag.
If one were to get into a more technical discussion of lag, it would end up something like this. In the C, in 2nd gear, at 1500rpm, the time to torque is 5 seconds. At 2000rpm, the TTT is 2 seconds. At 3000rpm, the TTT is 0.5 seconds. In 3rd gear at 1500rpm, it's 5.5 seconds. etc. In the GTS in 2nd gear at 1500rpm, it's 6 seconds. At 2000rpm, it's 2.5 seconds. And.... you've lost the average person a long time ago.
If any of you remember driving a 2002 Subaru WRX, it's rated for peak torque at 4000rpm! It didn't even really start building boost until 3k rpms. So your average person can look at peak torque at 1700rpm vs. peak torque at 4000rpm and instantly see the difference in the turbo lag they will feel. In reading how the 488 Pista engine drives compared to the McLaren 720S, the general comments is the 488 drives like a big NA engine where the 720S feels a bit more old-school turbo being a bit laggy with a big hit. 488 is rated peak torque ta 3000rpm and the 720s at 5500rpm. Golf GTI, peak rated@1500rpm. Golf R@1800rpm, the R will feel laggier.
If one were to get into a more technical discussion of lag, it would end up something like this. In the C, in 2nd gear, at 1500rpm, the time to torque is 5 seconds. At 2000rpm, the TTT is 2 seconds. At 3000rpm, the TTT is 0.5 seconds. In 3rd gear at 1500rpm, it's 5.5 seconds. etc. In the GTS in 2nd gear at 1500rpm, it's 6 seconds. At 2000rpm, it's 2.5 seconds. And.... you've lost the average person a long time ago.
If any of you remember driving a 2002 Subaru WRX, it's rated for peak torque at 4000rpm! It didn't even really start building boost until 3k rpms. So your average person can look at peak torque at 1700rpm vs. peak torque at 4000rpm and instantly see the difference in the turbo lag they will feel. In reading how the 488 Pista engine drives compared to the McLaren 720S, the general comments is the 488 drives like a big NA engine where the 720S feels a bit more old-school turbo being a bit laggy with a big hit. 488 is rated peak torque ta 3000rpm and the 720s at 5500rpm. Golf GTI, peak rated@1500rpm. Golf R@1800rpm, the R will feel laggier.
In any case, I think we all believe that Porsche engineers are reasonably competent. I would submit, therefore, that they would not release an engine that is capable of developing a level of torque at an rpm point that would damage the engine. And they certainly wouldn't advertise this capability and encourage their customers to do so.
But it seems that we all agree that the 991.2 has turbo lag, which, of course, it must. We also agree that one can choose a driving style that limits low rpm and minimizes the lag. And most of us seem to believe that the turbo engine's additional low and mid-range torque is more than adequate compensation for the lag. I think the OP's questions have been answered.
02-03-2019, 01:33 PM
#64
The 991.2 makes maximum power all the way to redline. At least the GTS does. Theres no power drop at the higher RPM. This is a fact.
It builds HP all the way to the top. Not torque which is at the bottom . Once you reach 5k the torque hands the baton over to the HP to do the rest of the work.
Lots of wrong information in here. The 9A1 is inferior to the 9A2. Numbers dont lie.
It builds HP all the way to the top. Not torque which is at the bottom . Once you reach 5k the torque hands the baton over to the HP to do the rest of the work.
Lots of wrong information in here. The 9A1 is inferior to the 9A2. Numbers dont lie.
02-03-2019, 02:12 PM
#65
The 991.2 makes maximum power all the way to redline. At least the GTS does. Theres no power drop at the higher RPM. This is a fact.
It builds HP all the way to the top. Not torque which is at the bottom . Once you reach 5k the torque hands the baton over to the HP to do the rest of the work.
Lots of wrong information in here. The 9A1 is inferior to the 9A2. Numbers dont lie.
It builds HP all the way to the top. Not torque which is at the bottom . Once you reach 5k the torque hands the baton over to the HP to do the rest of the work.
Lots of wrong information in here. The 9A1 is inferior to the 9A2. Numbers dont lie.
I agree......just have to realize it’s human nature to support what an individual may have with facts not always being a requirement!
02-03-2019, 02:19 PM
#66
Instructor
Thread Starter
As someone who works in consumer products, I have to disagree. Facts about products don't describe the experience of a product (there's a reason we stopped hearing about megahertz in computers). There are several things wrong with the above, but most importantly, HP or torque at a rev count doesn't describe off-on throttle response at that RPM, nor does it account for a change in rate of acceleration that is easily perceivable.
02-03-2019, 03:55 PM
#67
Rennlist Member
Obviously, but the point of those top-gear acceleration tests is to quantify powertrain flexibility.In musclescars of the Sixties, with giant engines, 3.73 or 4.11 differentials, and transmissions with no overdrive, acceleration in top gear was quite strong. In toady's cars with downsized turbos and much taller gearing, top-gear acceleration is much. But how much less, because all cars are not equal. These tests simply quantify the differences between cars.
If you don't care, so be it. But they are useful in discussions of turbo lag, which the 991.2 assuredly has.
If you don't care, so be it. But they are useful in discussions of turbo lag, which the 991.2 assuredly has.
02-03-2019, 04:07 PM
#68
That's pretty much the summary of it, and it applies to any engine. NA, forced induction, whatever. My CBR600RR doesn't get moving until 10k rpms. Cruising around town at 4k in 6th gear and the bike isn't going to accelerate quickly anywhere. It needs to be downshifted all the way to 2nd to get serious acceleration. Drive any 1990's/2000's Honda, the torqueless wonders below VTEC. Even the 997 Carrera is kinda gutless below 6k rpms when the variable intake resonance flap thing actuated; Porsche equivalent VTEC feel.
02-03-2019, 06:52 PM
#69
[QUOTE=PJ Cayenne;15613095]Yet amazingly, as we both know with base, MT 991.2s, in 7th gear on the highway, it takes only a small increase in pressure on the throttle to summon as much acceleration as needed get around slower traffic. Shift down to 4th or 5th, and your just gone. My thoughts are, if I feel any lag, I'm just in the wrong gear.[/QUOTE
^^^
Mine does the above, exactly, it's a MT C4S; at highway pace, 7th will clear traffic and get you to 100 effortlessly, any lower gear selected is really overkill in most traffic situations.
You really have to pay attention to your speed.
^^^
Mine does the above, exactly, it's a MT C4S; at highway pace, 7th will clear traffic and get you to 100 effortlessly, any lower gear selected is really overkill in most traffic situations.
You really have to pay attention to your speed.
02-03-2019, 10:07 PM
#70
This thread made my eyes bleed
(1). All turbocharged cars have turbo lag
(2). All NA cars have cam lag
In both instances Porsche have developed engineering solutions to compensate for the various idiosyncrasies common to each form of induction.
In a nutshell, for both forms of Porsche engine you switch to sport plus - in the case of the 9A2 the revs immediately go to ~ 3500RPM and you have ~4000RPM of lag free driving with near instantaneous throttle response.
In in the case of the 9A1 you drive above about 4500RPM (post cam) and have about 3300RPM of "cam" free driving with near instantaneous throttle response.
In a comparitive sense the difference in throttle response to full delivery is about 0.2s - effectively nothing and it can't be felt at all.
Below 3500RPM with the turbos and below 4500RPM in Porsche NA it's a case of pick your poison. A bit of lag with the 9A2 or absence of torque and power with the 9A1.
The real world reality is, as most 991.2 owners know, is the very small amount of discernible lag is made up for the gains in low to mid range torque and exemplary power delivery - and the only NA Porsche sports cars to square that circle (lack of torque and consequently HP at low to mid revs) are the 991 I and II GT3 and GT3 RS courtesy of shorter gearing ("torque multiplier")
(1). All turbocharged cars have turbo lag
(2). All NA cars have cam lag
In both instances Porsche have developed engineering solutions to compensate for the various idiosyncrasies common to each form of induction.
In a nutshell, for both forms of Porsche engine you switch to sport plus - in the case of the 9A2 the revs immediately go to ~ 3500RPM and you have ~4000RPM of lag free driving with near instantaneous throttle response.
In in the case of the 9A1 you drive above about 4500RPM (post cam) and have about 3300RPM of "cam" free driving with near instantaneous throttle response.
In a comparitive sense the difference in throttle response to full delivery is about 0.2s - effectively nothing and it can't be felt at all.
Below 3500RPM with the turbos and below 4500RPM in Porsche NA it's a case of pick your poison. A bit of lag with the 9A2 or absence of torque and power with the 9A1.
The real world reality is, as most 991.2 owners know, is the very small amount of discernible lag is made up for the gains in low to mid range torque and exemplary power delivery - and the only NA Porsche sports cars to square that circle (lack of torque and consequently HP at low to mid revs) are the 991 I and II GT3 and GT3 RS courtesy of shorter gearing ("torque multiplier")
Last edited by groundhog; 02-05-2019 at 01:59 AM.
02-04-2019, 01:38 PM
#71
Instructor
Thread Starter
This thread made my eyes bleed
(1). All turbocharged cars have turbo lag
(2). All NA cars have cam lag
In both instances Porsche have developed engineering solutions to compensate for the various idiosyncrasies common to each form of induction.
In a nutshell, for both forms of Porsche engine you switch to sport plus
(1). All turbocharged cars have turbo lag
(2). All NA cars have cam lag
In both instances Porsche have developed engineering solutions to compensate for the various idiosyncrasies common to each form of induction.
In a nutshell, for both forms of Porsche engine you switch to sport plus
Are there any contrary beliefs here to the Sport+ mantra? I think it’s worth it for you to try non-sport mode with an MT while driving it like a “turbo.” I was missing out by living only in Sport.
Last edited by tosha; 02-04-2019 at 03:07 PM.
02-04-2019, 04:32 PM
#72
Three Wheelin'
Yet amazingly, as we both know with base, MT 991.2s, in 7th gear on the highway, it takes only a small increase in pressure on the throttle to summon as much acceleration as needed get around slower traffic. Shift down to 4th or 5th, and your just gone. My thoughts are, if I feel any lag, I'm just in the wrong gear.
02-05-2019, 01:55 AM
#74
I have a base MT Carerra without the sport package, so no Sport+ for me. But I also am in disbelief at how fun and more satisfying the car is with Sport turned off. It gives the illusion that the car can keep increasing the rate of acceleration, and acceleration feels more predictable and controlled, which is one of my favorite aspects of driving a 911.
Are there any contrary beliefs here to the Sport+ mantra? I think it’s worth it for you to try non-sport mode with an MT while driving it like a “turbo.” I was missing out by living only in Sport.
or in PDK car flick to manual and use the paddles to keep you above 3500rpm The difference between sport and normal are quite minor with manual e.g. if you go to sport you get slightly sharper throttle mapping, changed rev limiter and rev matching on the down shift (plus cosmetic stuff like backfires and more sound in the cabin).
A lot more happens with the SC PDK equipped cars with sport+ e.g. performance throttle mapping, launch control, race like PDK gear mapping, engine mounts lock down, PTV plus, PDCC and RAS are dialled up. (PTV plus and PDCC are not available on the C). From the POV of lag the SC automatically ensures the revs don't drop below 3500rpm when you're on the ham.
02-05-2019, 04:15 AM
#75
I think this comment cuts through a lot of this. On the 996 4S, I got in the habit of gassing hard and enjoying the immediate response and a predictable buildup of torque that lasted all through the acceleration. When I drive the 991.2 like an NA, I need Sport mode for quick initial response, but I dislike the Sport mode’s jolt of torque that tapers and I’m at my desired speed almost immediately without the exciting buildup (I have a base Carrera). When I drive it “like a turbo” with more patience for initial response, but with Sport mode *off*, the boost increases more gradually, lasts throughout the acceleration (doesn’t level off noticeably like in Sport) and feels more predictable and much more fun. I did a spirited 3-hour drive north of SF on wet roads today in non-Sport mode (Mt Tam East Peak to Bolinas-Fairfax and Stinson), and it was some of the most fun I’ve had with this car, and I completely forgot about “turbo lag.”
Does this mean that non-Sport mode is designed to feel like NA, as long as the driver is gentle on the throttle in the first half-second of acceleration? Sport feels like a different car, and fun in its own way. I'd rather take a little longer getting to 85mph and experience predictable, increasing rate of acceleration. If you can get past the slower initial response, non-Sport creates an illusion that the car is much faster all through the acceleration.
BTW, it has been raining pretty hard in Bay Area. Nice you were able to get out for a drive.