2016 cammed C7Z down on power/boost

[doc350]

I have a 2016 C7Z A8 on the dyno that has a BTR Stg II cam, 10% OD crank pulley, 2.3 upper, Cordes CAI, flex and meth.

Im having an issue where boost gets pretty wavy about 5000rpm, and because of that, its not making the power it should.

Right now I'm just running in on straight 91oct, and its only making 600whp. However, torque is up at 700ft/lbs which seems reasonable. Boost starts at around 12.5psi when I get on throttle and drops to abour 10psi by 6500rpm. You can really see in the log how bad the boost curve gets.

I have put the shortest belt possible on it. In fact I even modified the tensioner in order to get the shortest belt possible on it.

I've messed around with SOI and virtual torque and nothing made much of a difference.

Attached are the current tune and log.

c7z_btrII_91oct.hpt

c7z_boostissue.hpl

[GHuggins]

If you still have variable cam timing, take a look in that department. These cams don't like to be 0ed out from everything I've personally seen with them.

[doc350]

I was told the cam is locked out. I was wondering if that is making it unhappy. However, I talked with BTR and they dont think thats the issue.

[TriPinTaZ]

Sorta looks like belt slip

[doc350]

That was my first thought too. I have the shortest belt I could get on it. The pulley combo isn't super aggressive on the car. Does anything jump out in the tune to anyone? I've stared at it so much I might be missing something.

[GHuggins]

That cam does exactly the same thing with the map reading in NA setups. Haven't run one boosted to know if it would perform the same in that setup or not. Also haven't gone through the tune, but my direct experiences with that cam is it looses about 10kpa during a wot run 0ed out. I also assume at this point you've checked inlet restrictions, bypass opening and closing?

[Alvin]

Its honestly loosing a pretty significant amount of boost.

Nothing else you can do with the belt?

Have you tried logging the SCIAP? Although I think the scanner isn't logging that correctly. But try to see if it has a intake restriction. Seems to penalize PD type blowers 2X as much as NA cars.

[doc350]

Its honestly loosing a pretty significant amount of boost.

Nothing else you can do with the belt?

Have you tried logging the SCIAP? Although I think the scanner isn't logging that correctly. But try to see if it has a intake restriction. Seems to penalize PD type blowers 2X as much as NA cars.

I'm gonna mess around with the belt some more, but I'm not sure if there is much else I can do. Same with the bypass, I have played around with the preload on it and it never really made a difference. I beginning to wonder if there is a leak where the snout bolts to the blower from when the pulley was installed.

I'll log the inlet pressure sensor too, but I dont think its an inlet restriction. The car has a 5" intake on it. It does still have the stock throttle body, but I don't think thats an issue at the boost/power levels we're hoping for.