STG

Yea, very happy. Around 5hrs labor hours just for IPD. While they were at it, had plugs and BMC filters done too.

mdftx1

I also had the IPD installed along with BMC filters and a Cobb Tune....amazing difference in responsiveness and interestingly a nice increase in MPG at cruising speeds...average 31 mpg on a 200 miles highway trip

Bacura

Amazing difference? Really? I can't tell the difference between regular C2S and X-51. You have a sensitive butt-o-meter.

HoustonATX

Has anyone tried ordering a GTS plenum and installing on their 991S? Should be pretty much plug and play right?

dkmesa

STG did your car have the infamous "stumble" low in the RPM band prior to the IPD install? Wondering if the IPD would smooth that out.

J3C

Ordered my IPD Plenum. Will report back once installed and I have time to provide a fair assessment. I am just after the increased intake sounds, any performance gains are just a bonus. I'll also be doing a dyno and tune later this summer. Shame cobb removed their stage 2 map. Open to tuner recommendations in the NJ/NY metro.

MrSharps

J3C - keep us posted. I’m looking into a combination of iPad plenum + bmc filter + x-pipe (center muffler delete) + Cobb tune on my 3.4L. I’ve got a shop that can do a dyno, but I’d love to hear your results before taking the plunge.

STG - thanks for all of your feedback on this thread. I’m glad that you love the new sound. But how was it different? And was it louder at all RPMs or just at higher levels?

Thanks!

garfunkle

FVD has a tune for it.

I did mine with a tune from FVD. The dip ~4K RMP when the car comes on cam is gone and the car pulls harder lower in the range. There is more induction sound; subtle but noticeable. I also did BMC filters but really don't think they mattered.

with the 3.4 - I think you can get the larger TB which will also make a good bit of difference.

koven

anyone ever dyno before and after IPD for a .2 ?

George from MD

No dyno. Lots of placebo. I think Barnum was right.

MrSharps

Thanks for the feedback Garfunkel. I think the 3.4L comes stock with a 82mm TB.

To George from MD’s point - the 991 has been out for 7 years. It is surprising (disappointing?) that it is this hard to find numbers and the supporting data for plenums. You’d think there’d be readily available dyno sheets or someone with a YouTube video showing a before and after. Especially for the base and 3.8L as they are the least expensive in the range, most common, and presumably most likely for owners to seek power gains.

PTS-BRG

BGB Motorsports did a dyno before and after the IPD Plenum and posted the chart on this forum. Everyone who saw the chart seemed to have a different interpretation.
My interpretation was that the plenum actually DECREASED HP and Torque across the whole power band. Others saw it differently and others said it required a tune to show the real gains.

I have more than most by way of performance goodies and I did not opt for the Plenum. Thats my opinion of course..