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I've read everything I can find on this, and there are conflicting comments on whether boost tapers off before, or stays up, before the tach hits redline. I know the computer adjusts boost to produce pre-set power levels, adjusting boost for ambient conditions, drive mode settings, base, S, etc. I also read that some 991.2 owners have had boost leaks repaired. Is there a road test that can indicate whether boost is tapering off, or if there is a leak? My car is a '18 C2, MT, w 8500 miles. In 2nd and 3rd gear pulls, at sea level, 65 degrees, I saw the boost gauge reach 10-11 between 6000-6500rpm, then fall off above that.
My C4S does the same. Depending on temp, it goes to 12-15 (maybe 16) PSI then drops off. In the cold temps and early morning or late night its up to 13 PSI then ticks down to 11 near redline, spikes up, and repeats.
Thanks for the feedback, guys. Sounds like my car is OK. Has anyone had a leak? I'm wondering if it's something that can be felt, like an early sign off, or if in our cars it's mostly noticed on the boost gauge.
On my X51 C2S, I see brief blips of17 psi once in a while. Higher boost seems to happen at higher rpms, but not as high in 1st or 2nd. Peak boost seems to increase with each gear from 1st thru 3rd. Could the ECU be holding boost down because of the rear tires squirming for grip?
I haven't launched mine, so can't say what it would do there.
Possible (although I really haven’t felt the car struggling for grip ever in a straight line), don’t really pay too much attention to the boost when I’m WOT. Think I’ve only seen 16, but haven’t redlined in 4th for a long time given we are in full winter here. Lots of 1st and 2nd and I did see 16psi when in 3rd. (Purposely used the sport response button as it’s supposed to give you max boost and have launched many times)
Will have to pay attention when we are back on summers.
03-03-2019, 03:22 PM
991.2 Boost Falling Off Before Redline Normal?
Sounds like my car is OK. Has anyone had a leak? I'm wondering if it's something that can be felt, like an early sign off, or if in our cars it's mostly noticed on the boost gauge.
