Tried searching the archives and did not find the results helpful.

An Internet search returns results of automotive journalism saying the Carrera S peaks at 16 PSI of boost, but I don’t want to simply trust that.

What peak PSI number is readily observed for a stock 991.2 Carrera S? Owners: please chime in.

Here’s my problem.

My 2017 Carrera S (7spd manual) seems more than a little sluggish after a 4-year major service yesterday with spark plugs and engine air filter change at dealer. I am seeing no more than 10 PSI at any point in the rev range in any gear; I could swear this thing went into the teens but I honestly do not recall for sure.

I drove the car extensively on the highway at high speed today and something seems off especially at the top end of the RPM range.

First gear seems like it takes a longer time to reach redline- I recall it being much snappier.

Wondering if a real issue is happening (possibly connected with the service) or if I’m imagining things because I haven’t driven the Carrera S in a while.

 

Unless you're driving really aggressively, you're not going to see much above that. Try putting it into 2nd gear while puttering along, and then floor it and hold it floored as long as you can. Or do the same from a standstill in 1st gear. My recollection before tuning my car is that it took some aggressive driving to achieve a max boost number, and it was very rare to see anything above 10psi. Tuned, and with GTS turbos, it hits 17psi easily, but I think that's also the max of the dashboard display. From what I've seen, the dashboard display is particularly unreliable, and you really need to access the MAP values directly via OBD-II or an access port.

 

I had exact same symptoms on my 2017 C2 last year. Turns out the hose/vacuum line from the COV to the intake manifold had been severed. I cannot think of the actual name of the connector, but once I replaced the hose portion using the existing connectors, I was back in business with full boost.

It has to be disconnected to change the air filter, so I’d check to see if the connection has come loose or if it was severed by the serpentine belt if it was reconnected incorrectly under the Y pipe (ask me how I know). Old picture may help some ... red arrow depicts the path of the connection. If this is the case, it’s an easy fix (once you remove the bumper, of course) as these particular components are easy to see and get to.

I hope it’s that simple and good luck!!!

 

Thanks so much!

And what is your typical peak boost value on your display?

 

I have a C2 base, so supposedly it goes up to 13. I can see 11 or 12 just punching it in 3rd gear without much effort.

But when I say I had exact same symptoms....I mean exact same! Wouldn’t go past 10 psi to save its life, almost lethargic acceleration. No warning lights on dash, but my ODB2 scanner showed a “low boost pressure” code.

You sound like me when sensing even the slightest deviation in acceleration/throttle response. I hope it gets sorted quickly...keep us in the loop please!

 

Good point - I'd forgotten about that. One thing to note - my vacuum line had *also* been cut by the serpentine bolt; it occurred at about the same time as the GTS turbos were installed - after the installation they were test driving it and it produced no boost pressure at all. Turns out that the serpentine bolt had cut it. If you really don't see anything beyond 2-3psi even under hard acceleration, you've probably got a boost leak somewhere, but getting beyond 10psi for me was hard. It's possible, I guess, that I had a boost pressure leak in the vacuum tube for a while and that the installation made it catastrophic, so it's possible you're seeing the same thing post maintenance.

 

IMO that’s not normal. Lots of things come out for the air filter change-my guess is a vacuum line was missed or a connection is loose or damaged. As a comparison my base car was easily over 10psi in stock form.

 

Thanks everyone for all contributions.

I would really appreciate it if some 991.2 S/4S owners could verify that they see 15psi all day long and maybe 16-17 (for the sake of apples to apples). Pictures would be great too.

I will need to return to the dealer (possibly today) and therefore I would like to assemble as much finite and concrete information as possible- not conjecture- so I can have the best information and the best case against the assumption that either I’m crazy or the Internet guys are just a bunch of crazy Internet guys

 

.2 4S owner here, bone stock car.

Dash-indicated 16-17psi all day long if I wind it out beyond 4500rpm, otherwise I usually see 8-12psi in normal(ish) driving.

 

Thanks!

 

Back in business!

Dealer confirmed and fixed vacuum leak. (No apology or compensation of course for the inconvenience of schlepping 100 minutes each way for three total trips instead of one.)

Repair complete and now I see 14psi all day long with an occasional 15 and an elusive (but observed) 16psi.

Thanks everyone for chiming in!

 

Excellent!

 

Great to hear-did they say where the culprit was?

 

“On the one side, like you said.”

They didn’t want to go into details about their screwup

 

Thank you all for this post, and the responses. I recently purchased a 2019 991.2 CS2 MT and the boost reads Zero (0) psi. I am hoping that it is related to the gauge connection as it seems to perform just fine. I will take it to the Porsche dealer this Spring and let you all know the result.