DJ23

I was trying to find in the manual the max PSI you can obtain with the TTS in either Sport or Sport Plus Mode when in Overboost. I can't seem to find it. If someone knows what or where it is
in the manual let me know.

Also if I'm reading this correctly, when looking at the Power (HP), Torque, versus RPM graph, it appears that in overboost from 2250 to 4000 rpm the car will reach close to 600 HP for the time you are in
that part of the curve when in Overboost. For those of you have had a lot more seat time than I have how do you utilize this information when you are driving with the "Perfomance" screen on the Multifunction Display?

Thanks for your time.

Jay

Tfk

M3S3R

Thank you for posting very informative.

Kevin

You can see the effect of the overboost/curve from the attached

Randyc151

I'm still trying to figure out if the overboost is automatically on when in Sport+, or does pressing the button still add boost when I'm coming out of a corner onto a long straight. I don't see much difference when I do that at VIR in Oak tree.

sctanton52

DJ23

Thanks to everyone for clarifying this. I have a better understanding of where I will be when our weather improves and I get a chance to drive consistently.

Tfk, thanks for posting that press release. I am just amazed sometimes at the information some of you guys have. This helped a lot.

Jay

worf928

I recall, from reading Porsche's materials, that over-boost is available in Sport (only with SC) as well as Sport+ and that, in either mode, it's 'on' all the time. It's essentially just a software 'switch' that changes the maximum permissible boost before the waste gates start bypassing.

Edit: Oh! Wait. That was true for 991.1. No idea about .2s. Oops.

FastLaneTurbo

In the S model, turbo boost is increased to 1.2 bar (17.4 psi) and maximum engine speed has risen 200 rpm to 7,200 rpm, creating a more flexible engine with greater torque during maximum acce- leration and following gear changes.

Overboost: power is boosted at the press of a button

With the Sport Chrono package, standard on the 911 Turbo S and optional on the 911 Turbo, maximum acceleration is aided by an overboost function that increases maximum turbo boost pressure by approximately 0.15 bar (2.2 psi) for up to 20 seconds in the engine’s midrange, increasing max torque to 750 Nm (553 lb.-ft.).

I read that as 1.2 Bar being the standard 991.1 Turbo Boost and overboost increasing 0.15 to 1.35 Bar.


Re 991 Turbo Torque Values, Interestingly:
The Maximum Torque Spec of 553 Lb. is exactly the same on all 991S Turbos: 560, 580, 607 and 700 HP.
Only the RPM Range changes slightly as follows.

The Maximum Torque of the TTS-1 (560 HP @ 6,500 RPM) is 553 Lb.Ft @ 2,200 - 4,000 RPM
The Maximum Torque of the TTS-2 (580 HP @ 6,750 RPM) is 553 Lb.Ft @ 2,250 - 4,000 RPM
The Maximum Torque of the TTS-E (607 HP @ 6,750 RPM) is 553 Lb.Ft @ 2,250 - 4,000 RPM (TTS Exclusive Model)
The Maximum Torque of the GT2RS (700 HP @ 7,000 RPM) is 553 Lb.Ft @ 2,500 - 4,500 RPM

Jean

Thats a great observation, torque is directly correlated to boost level at a certain RPM in engines with similar BMEP, all these cars will have the exact same boost level at a certain RPM to achieve same torque.

Torque on the factory cars is kept under control for several reasons among others:

1- Drivability, aggressive torque is fun but dangerous if you don't have grip
2- Longevity of engine and clutches, factory warranty
3- Consistent performance- keeping temps under control

When you drive a 997GT2 and 997 GT2RS back to back you cannot tell which is which, same kick in the pants, exact same performance feel, yet a GT2RS has 90HP more at higher revs.

Penn4S

edkwon

I just picked up a 2015 Turbo and have been googling for an answer on how to 'activate' overboost function on a car with SC.

Reading thru this my understanding is: when you're in either Sport or Sport+ mode, overboost will automatically kick in when the gas pedal is at WOT in the right RPM range, for a limited time period, and it is not something you can manually control.

Randyc151

It's manually adjustible. Sport or Sport+, then manually adjust with your right foot.

Deezflip

Don't mean to bring this back, but what happens after 20sec? Do you have the press that button again? Or in some Porsches, have to press the Sport+ again?

catpat8000

Let's clarify one more time then A few points:

1, When the car (991.1 or 991.2) is in Sport or Sport+ mode, over-boost is always available. You get it by depressing the accelerator, nothing more is needed.

2, Pressing the button on the steering wheel does NOT produce more power and it does NOT provide more boost. What it does do it put the DCT into the best gear for acceleration at that speed, it opens the throttles slightly but without fuel to enable building some small amount of pre-boost, the better to reduce turbo lag when you do nail it. At the end of 20 seconds, if you want your engine to keep revving at a very high rpm, press the button again

3, Overboost does not increase the max horsepower of the engine because it is not available at higher rpm, where max hp occurs (recall hp is torque times rpm).

4, All the modern TT/TTS/GTRS2 engines make a maximum of 553 lb-ft of torque. The reason they have varying hp levels is because they are able to make enough boost to keep the torque output up at higher and higher RPM, using different turbos, sw, etc.

This is easy to see by back-calculating the torque at the RPM where max HP is made.

TTS-1 (560 HP @ 6,500 RPM) is making 450 lb-ft @ 6500 RPM
TTS-2 (580 HP @ 6,750 RPM) is making 450 lb-ft @ 6750 RPM
TTS-E (607 HP @ 6,750 RPM) is making 470 lb-ft @ 6750 RPM (TTS Exclusive Model)
GT2RS (700 HP @ 7,000 RPM) is making 525 lb-ft @ 7000 RPM

Making the extra torque at higher RPM in the GT2RS (more HP) allows using gearing to deliver more torque to the wheels. The GT2RS has the same transmission ratios as the Turbo S but has a 15% shorter (numerically higher) final drive ratio (3.96 in the GT2 vs 3.44 in the Turbo S). When combined with larger wheels and tires, the result is the GT2 gearing is about 8% shorter than the TTS.