Preferred RPM range and turbo lag in base 991.2

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01-29-2019 | 06:02 PM

#16

spdracerut

Three Wheelin'

Joined: Feb 2016

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Headers will measurably improve throttle/boost response:

https://motoiq.com/testing-vektor-pe...911-carrera/9/

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01-29-2019 | 06:04 PM

#17

SeeForce

Racer

Joined: Nov 2014

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My 991.2 C2 would eat my 991 C4S's lunch.

any turbo lag is mitigated by the increase in torque. back up a gear and keep the revs up. mine is a blast to drive... far more friendly on the streets.

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01-29-2019 | 06:33 PM

#18

crossroads

Rennlist Member

Joined: Jun 2006

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Maybe you are used to the NA power delivery. Looking at some hp/torque graphs, the turbo torque peaks at around 5000 rpm and hp peaks at around 6500 rpm whereas the NA hp peaks at a higher rpm(not sure where at what rpm your 996 hp max is).

What I'm saying is that the turbo power drops off at higher rpm's where the NA hp is still increasing. So maybe keeping your rpm's a little lower or being in a higher gear will keep you in the sweet spot longer.

https://rennlist.com/forums/991/9304...confirm-4.html

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01-29-2019 | 06:46 PM

#19

tosha

Thread Starter

Instructor

Joined: Aug 2017

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From: San Francisco

Quote:

Originally Posted by Psorcery

Does it have sport plus AKA Sport Chrono Package? Are you in D or manual mode?

In sport plus, the turbos are primed and pre-spooled 1-2psi. Just sitting there waiting for you to hit the throttle. Instantly delivering max power.

I have a base manual, and don't have sport plus. I just need to keep the RPMs up it looks like, and on the climbs I may learn to expect the lack of power if the turbo is already spooled up and just give more gas... Or try an S in the future.

Quote:

Originally Posted by Psorcery

In my 991.2 GTS, If i'm in Sport+ in prime gear and I mash the throttle there's no lag.. Your head snaps back into the headrests and your tummy will start to tickle... This is the GTS which people say is "laggy-er"

If I'm in D, and normal mode, and auto start/stop is not turned off.. Yeah. The car is not looking for razor sharp throttle response and therefore will lag... I can replicate lag in a 991.1 tuned C4S if I tried.

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01-29-2019 | 06:57 PM

#20

Psorcery

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Quote:

Originally Posted by tosha

Ahh, makes a little more sense now.

I've never driven a manual base with no chrono before.. Closest I've driven is your setup but with PDK which definitely helps mitigate any lag. I'm positive you'd see better results in a PDK car. The base engines do run out of steam when reaching the top of 3rd and beyond (when stock at least). When driving the base, I too would always have it in Sport mode. Sport mode on a NON chrono car makes the same sounds as a chrono car that's in Sport+ mode but you don't get the primed turbos feature unfortunately.

You may want to look into headers to help increase spool.

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01-29-2019 | 07:15 PM

#21

DY369

Instructor

Joined: Oct 2015

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From: San Diego

@Psorcery per your example above "If you floor it in 5th gear at 2K rpm. There will be lag." How many N/A 911's would do well in 5th gear at 2,000 rpm's? Wouldn't most have some sort of hesitation because they are not anywhere near their power band?

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01-29-2019 | 07:56 PM

#22

Psorcery

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Quote:

Originally Posted by DY369

Yes absolutley, that's the point I was making. Any petrol vehicle will have lag in that scenario. Especially turbo applications.

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01-29-2019 | 08:32 PM

#23

JoeyClosets

Track Day

Joined: Apr 2018

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Lag? No Lag....

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01-29-2019 | 09:27 PM

#24

S S

Burning Brakes

Joined: Jul 2015

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From: Liberty Hill, TX

4,000 - 6,500 and Sport + ... It is a beautiful thing. Outside of that, and since we live in a part of the universe where physics applies uniformly and always, there are consequences. You aren't going to change it, just drive it the way Porsche has engineered it to mitigate the downsides. More gas used, more hydrocarbons produced, but what a way to go!

S

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01-29-2019 | 09:29 PM

#25

Wujohn

Rennlist Member

Joined: Aug 2018

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From: San Diego

Quote:

Originally Posted by crossroads

This. I have a base and I find I really lose the oomph and the car seems to choke as the engine revs out whereas at 3-5K RPM it has some good punch to it. I think the base has really usable power on the street but I would not kick an S or GTS out of bed if it were eating crackers and I am entertaining a change. If I get off my butt and change out my cats and headers, maybe I can avoid the upgrade.

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01-29-2019 | 09:44 PM

#26

Bob Z.

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Joined: Jul 2001

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From: Marineland FL

When I think of turbo lag I think of the '87 930 I had in the past...I do not think of turbo lag in my 991.2 GTS, ever.

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01-29-2019 | 10:44 PM

#27

bkrantz

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Joined: Oct 2012

Posts: 6,098

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From: SW Colorado

Quote:

Originally Posted by tosha

I use "turbo lag" to mean the sudden change in rate of acceleration that you feel at most a second after gassing. Are you saying it's not "turbo lag" unless its comes on hard after a few seconds?

I find that on the 991.2, acceleration doesn't increase predictably when I gas hard, unless I do it at around 4K RPM.

Well, there you go.

Like others, I find little perceptible lag. After all, these are still 3.0 liter engines, with mild turbocharging.

When driving for performance, we keep revs up. Above 4000 RPM there is really no lag with the 991.2. And NA engines are up in their power band. Both types offer thrilling performance.

At lower RPM, the mild turbo 991.2 might have just detectable lag. The 991.1 instead offers "lug". I am biased, but I think I know which type will win if we stomp on both in 3rd gear at 1000 RPM.

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01-29-2019 | 10:54 PM

#28

Rennolazine

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Joined: Jan 2018

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From: Chitown, USA

Quote:

Originally Posted by Psorcery

You need to be in sport plus.
You need to be in sport plus.
You need to be in sport plus.
You need to be in sport plus.
You need to be in sport plus.
You need to be in sport plus.
You need to be in sport plus.

You need to turn off Auto Start/Stop.
You need to turn off Auto Start/Stop.
You need to turn off Auto Start/Stop.
You need to turn off Auto Start/Stop.
You need to turn off Auto Start/Stop.
You need to turn off Auto Start/Stop.
You need to turn off Auto Start/Stop.
You need to turn off Auto Start/Stop.
You need to turn off Auto Start/Stop.

Did I mention you need to be in sport plus and while in 'normal' you need to turn off auto start/stop?

If you floor it in 5th gear at 2K rpm. There will be lag..

If you're in prime gear, in the proper setting (SPORT PLUS, or SPORT if you don't have the chrono package) there's virtually no lag.. In racing, there is no lag. Especially in with the base engine/turbos.

This^ Well said
Also manual cuts out some of the perceived lag although you lose almost all boost between shifts (save 1-3 psi). Here the transmission is never asleep, just the driver. You wanna haul ***? Pow, prime gear, what lag?

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01-30-2019 | 01:12 AM

#29

Valvefloat991

Burning Brakes

Joined: Feb 2017

Posts: 1,157

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From: Golden, CO

Quote:

Originally Posted by DY369

No it wouldn’t. At 2000 rpm, a 991.1 would deliver everything it had immediately. In contrast, a 991.2 would need at least a second to reach maximum 2000-rpm torque. But that torque would be much higher than the 991.1’s maximum. Peak torque and turbo lag are independent parameters.