New user here...proud new owner of a CPO 997S, with EVO intake, EVO headers and AWE exhaust. I'll post photos and description when it stops raining here in NorCal!

Anyway, my question. There is an annoying drone with light throttle between 2 and 3000 rpm. I'm wondering if this is the intake. I have the stock intake, and was considering swapping to see if this cures it. Does anyone have any similar experience?

 

Your resonance problem is probably coming from the exhaust, not the intake.

 

If anything go with the x-51 air box. I noticed less resonance when I did that. The AWE mufflers may be doing a little bit of it. Check to make sure your tips are equal length away from the body too.

FYI - In stages I added the following, RSS Plenum, E-BAY Headers, X-51 exhaust and RSS TB, Complete AWE exhaust, H,C,& M, then an APR ECU upgrade.
An easy experiment try putting the stock mufflers back on and see if that takes it away. I doubt that it will but it is easy to do if you have the stock mufflers.

 

Did you notice much of a change from your APR Chip

 

I went from oem exhaust to AWE Headers, Cats, and mufflers. I didn't touch the intake and if I do, it will be oem X51. No drone before or after REVO software. Easy enough to revert to oem intake - try it and see if that does the trick.

 

YES. I love it. It was the icing on the cake so to speak. It does everything everyone else has talked about when they do a chip.
ie; RonCT.

The best way I can explain the difference with the mods is I would be in situations on 2 lane roads that I used to pass a car on my motorcycle with out much thought. (The ability to get quickly around a car in a fairly short distance) I now have that ability with my 911. The car is noticeably quicker and the power band is very linear where it used to take off between 4-5K it just goes from 2K on up now.

The biggest advantage over other brands IMO is programs can be changed with the cruise control. It also has a security feature that disables the throttle pedal with a 4 digit code.

 

Thanks for the info, I am wanting to do this mod on my car, I have APR on my Allroad (as well as 2 S4's in the past). One thing that I like is the 93 OCT program, I only put 94 Octane in my car. I guess this is a mod that I will be doing soon.

 

I have APR on my Audi A3 too. They are good people I have met them at several Porsche Events and went to their HQ in Auburn for the 911. They will be opening their new facility early next year with their own track.

 

I met Greg Custer at a VW/Audi Event in Seattle a few years ago, I agree with you that they are great people.

 

I dealt with both Greg and Keith.

 

When you removed the OEM air cleaner, you also eliminated a helmholz resonator. (If you look at the rubber duct that went to the throttle body and the air cleaner, you will notice a small duct branching off ot the left. This is connected to the resonator.) These resonators are used to cancel out unwanted noise from the induction system. This is a possible reason for the drone you are now experiencing. It is hard to say exactly what the frequency is without measuring it, but I would guess that you have a 3rd order drone at 2500rpm, from your description. This would be a 375Hz noise. You could cancel this noise by making your own 375Hz quater wave tuner. This would be a tube of 228mm in length with a capped end. (If the frequency is not 375Hz, then of course the length would need to be adjusted.) The tube would be attached to the inlet duct somewhere along its length.
Or, you could live with the drone.
It could be also as RayS suggested, an exhaust issue. Or both.

 

Thanks...this equipment was already on the car when I bought it, but I have all the stock pieces. Based on your other thread on the EVO intake, I will probably switch back to stock, and see how it sounds. I don't expect any perceptible drop in power. I'm an aero engineer by trade, so I'm dubious about the claimed HP gains for the intake and "plenum." The car does sound *awesome* at about 5000 rpm, so hopefully that characteristic stays with the stock intake...

 

I hope so too. When designing vehicle psychoacoustics, we try to take the induction system out of the equation and drive perception with the exhaust note. However, I have to apologize for my calculation of 3rd order noise. (I forgot that I usually leave my brain at the office and ended up throwing an extra "3" into the frequency calculation for no apparent reason.) The 3rd order noise frequency at 2500rpm is, in fact, 125Hz. This would require a 688mm pipe to cancel, which is much less packaging friendly.

 

I've had a EVO intake since they first hit the market. No issues. Also have full AWE system. This could be more exhaust related. JMO.

JohnJ
SATexas/Croatia.

 

Well, I switched over to the stock intake today, which was a very easy job, by the way. I'm pleased with the change in sound. The resonance from 2-3K is still there, but the amplitude, and the range of rpm it occurs over, are both significantly reduced. The only downside is the wail at 5K rpm with WOT is not quite as intense. IMHO, this is a worthwhile trade for daily use. The drone was getting on my nerves when I was caught in traffic. So for now, it's stock for me. I may hold onto the EVOMS unit for track days, as the swap is no more than a 15 minute job. Thanks to all for your input.