991.2 S boost behavior
02-18-2019, 11:13 PM
#16
Pro
used torque app, and check calue against oem gauge first and matched, but oem stops at 19 and torque app shows 20.7psi
02-19-2019, 09:00 AM
#17
we had discussion on this topic a while ago on this forum to death. but i think the gist is that these modern cars are computer controlled to control the boost so that you get the linear feeling of a NA car and maintain the maximum HP your car is designated to have by bleeding the turbo through computer control. if this was an older turbo car, once the turbo hits max boost it should stay there through redline, but not in these 911s. the turbos boost is basically managed by the computer real time. its normal is what i'm trying to say i guess.
try launch control. you'll hit max boost
try launch control. you'll hit max boost
02-25-2019, 10:07 AM
#18
Update:
I notice that boost is higher at 65F temperatures.
~low 30F: Boosting to 12 (with 13 blips)
~40F: Boosting to 13 (with 14 blips)
~65F: Boosting to 14 (with 15 blips)
Early morning and later evening (when I typically drive) its lower peak boost by 1 or 2. Mid day its higher... I actually saw 16 in 1st gear when trying to repro at dealer.
Sport mode, sport plus, sport response etc doesn't do anything with peak boost. I haven't messed around with launch control. Sports plus keeps turbo always spooled 1-2.
I'm leaning toward that the car is tuned to use PSI boost to meet a performance target. This means the engine is LIMITING itself intentionally and things like weight aren't a factor. It goes how fast Porsche codes it to go. I suppose that means there's plenty of headroom for aftermarket hack tune, but I personally don't find myself wanting more power. I just want to know that I don't have something wrong with my car.
I'm still not sure about PSI dropping 1 or 2 1000 RPM before red line though.
I notice that boost is higher at 65F temperatures.
~low 30F: Boosting to 12 (with 13 blips)
~40F: Boosting to 13 (with 14 blips)
~65F: Boosting to 14 (with 15 blips)
Early morning and later evening (when I typically drive) its lower peak boost by 1 or 2. Mid day its higher... I actually saw 16 in 1st gear when trying to repro at dealer.
Sport mode, sport plus, sport response etc doesn't do anything with peak boost. I haven't messed around with launch control. Sports plus keeps turbo always spooled 1-2.
I'm leaning toward that the car is tuned to use PSI boost to meet a performance target. This means the engine is LIMITING itself intentionally and things like weight aren't a factor. It goes how fast Porsche codes it to go. I suppose that means there's plenty of headroom for aftermarket hack tune, but I personally don't find myself wanting more power. I just want to know that I don't have something wrong with my car.
I'm still not sure about PSI dropping 1 or 2 1000 RPM before red line though.
03-16-2019, 09:52 AM
#19
75F and I've seeing 15 PSI a lot and up to 17 sometimes.
I think that my theory is correct. These engines are hard coded to boost less with colder/denser air and boost more when air is less dense to meet performance target. Kind of weird because my NA boxster performed better with denser air...noticeably worse in hot humid (+maybe high altitude). The plus side is everyone is getting consistent performance.
I think that my theory is correct. These engines are hard coded to boost less with colder/denser air and boost more when air is less dense to meet performance target. Kind of weird because my NA boxster performed better with denser air...noticeably worse in hot humid (+maybe high altitude). The plus side is everyone is getting consistent performance.
03-16-2019, 12:52 PM
#20
75F and I've seeing 15 PSI a lot and up to 17 sometimes.
I think that my theory is correct. These engines are hard coded to boost less with colder/denser air and boost more when air is less dense to meet performance target. Kind of weird because my NA boxster performed better with denser air...noticeably worse in hot humid (+maybe high altitude). The plus side is everyone is getting consistent performance.
I think that my theory is correct. These engines are hard coded to boost less with colder/denser air and boost more when air is less dense to meet performance target. Kind of weird because my NA boxster performed better with denser air...noticeably worse in hot humid (+maybe high altitude). The plus side is everyone is getting consistent performance.
03-18-2019, 07:46 PM
#23
Burning Brakes
03-19-2019, 11:57 AM
#26
To anyone concerned about boost leaks and if something is wrong...
The reality is how much your car boosts compared to others is "it depends" on altitude, temperature, and air density. In less than ideal conditions an S model will boost up to 16-17 PSI peak. If conditions are good and it can meet its torque target, it simply won't boost as high.
I don't have GTS, but my understanding is boost is will be similar, however will be earlier and maintain in the RPM range. Assuming conditions call for it, a GTS will get to 16 PSI and stay there and slightly dip near redline, but in same conditions S will peak at 16 past 5k RPMs. A T or base model will be similar to S but 2-4 PSI less. The less boost the engine is doing the more NA it feels like so there are pros and cons for either model...people say GTS noticably feels boosty and the base car is more responsive, while an S without powerkit is somewhere in between (IMO closer to base car).
If you're not flooring it and revving in mid RPMs mostly like me, honestly peak boost isn't relevant since it's mostly less than 10 PSI. I think 50 more torque in S model would be noticable in this range though. I wish these cars had hp and toque gauge...
The reality is how much your car boosts compared to others is "it depends" on altitude, temperature, and air density. In less than ideal conditions an S model will boost up to 16-17 PSI peak. If conditions are good and it can meet its torque target, it simply won't boost as high.
I don't have GTS, but my understanding is boost is will be similar, however will be earlier and maintain in the RPM range. Assuming conditions call for it, a GTS will get to 16 PSI and stay there and slightly dip near redline, but in same conditions S will peak at 16 past 5k RPMs. A T or base model will be similar to S but 2-4 PSI less. The less boost the engine is doing the more NA it feels like so there are pros and cons for either model...people say GTS noticably feels boosty and the base car is more responsive, while an S without powerkit is somewhere in between (IMO closer to base car).
If you're not flooring it and revving in mid RPMs mostly like me, honestly peak boost isn't relevant since it's mostly less than 10 PSI. I think 50 more torque in S model would be noticable in this range though. I wish these cars had hp and toque gauge...
01-09-2020, 08:20 PM
#28
Am I missing something?
01-09-2020, 08:44 PM
#29
Update:
I notice that boost is higher at 65F temperatures.
~low 30F: Boosting to 12 (with 13 blips)
~40F: Boosting to 13 (with 14 blips)
~65F: Boosting to 14 (with 15 blips)
Early morning and later evening (when I typically drive) its lower peak boost by 1 or 2. Mid day its higher... I actually saw 16 in 1st gear when trying to repro at dealer.
Sport mode, sport plus, sport response etc doesn't do anything with peak boost. I haven't messed around with launch control. Sports plus keeps turbo always spooled 1-2.
I'm leaning toward that the car is tuned to use PSI boost to meet a performance target. This means the engine is LIMITING itself intentionally and things like weight aren't a factor. It goes how fast Porsche codes it to go. I suppose that means there's plenty of headroom for aftermarket hack tune, but I personally don't find myself wanting more power. I just want to know that I don't have something wrong with my car.
I'm still not sure about PSI dropping 1 or 2 1000 RPM before red line though.
I notice that boost is higher at 65F temperatures.
~low 30F: Boosting to 12 (with 13 blips)
~40F: Boosting to 13 (with 14 blips)
~65F: Boosting to 14 (with 15 blips)
Early morning and later evening (when I typically drive) its lower peak boost by 1 or 2. Mid day its higher... I actually saw 16 in 1st gear when trying to repro at dealer.
Sport mode, sport plus, sport response etc doesn't do anything with peak boost. I haven't messed around with launch control. Sports plus keeps turbo always spooled 1-2.
I'm leaning toward that the car is tuned to use PSI boost to meet a performance target. This means the engine is LIMITING itself intentionally and things like weight aren't a factor. It goes how fast Porsche codes it to go. I suppose that means there's plenty of headroom for aftermarket hack tune, but I personally don't find myself wanting more power. I just want to know that I don't have something wrong with my car.
I'm still not sure about PSI dropping 1 or 2 1000 RPM before red line though.
2017 4s mt
during the summer months I was pulling the following:
in sport mode - 15-16 psi even hit 17 in a flash
in sports plus 17-18psi easily
these values were achieved due to TWO NEW factory turbos being installed (warrantee work).
more recently now that it is winter the boost has dropped to the following:
sports mode - 13 psi and I can hear the blow off valve really loud (or maybe I am hearing a leak)
sports plus - I am rapidly hitting 17psi then the blow off noises and then bouncing between 13-15 psi
is this normal behaviour given the car is now driving in the winter temps? Or should the boost be constant and independent of outdoor temps?
... is it possible I have a leak?
Rapter is online now Report Post
E
based on your post and a few other it seems your conclusion may be correct. The cold dense air is allowing the cars power/ torque target to be met and therefore less boost is needed.
do I have this right?
01-10-2020, 07:40 PM
#30
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