Torque dip sound: rattling / vibrating - Toyota GR86, 86, FR-S and Subaru BRZ Forum & Owners Community

mike_ekim1024 · 11-06-2013, 04:19 AM

With certain tunes / mods I hear a difference in the torque dip area.. like a rattling / vibrating sound, and then it smoothes out again. I've heard that resonance and air dynamics play a large role in torque. Am I hearing the loss?

I heard it more prominently when I got an intake, then it went away when I installed my cat back exhaust. With it I felt the dip go away. Could you say it's 1:1 or it's just mildly related?

endrswrd · 11-06-2013, 10:28 AM

The sound your hearing is coming from large overlap made possible by the AVCS system. When trying to maximize power on these cars you run alot of overlap before and drop it off then ramp back up through the TQ dip to minimize the valley itself. I have only been tinkering with it for a few hours since I just got ECUflash beta last week.

But dropping the overall overlap and smoothing out the ramping up and down makes this go away almost completely without effecting the reduction in the tq dip.

jeebus · 11-06-2013, 11:14 AM

I like the sound personally.

mike_ekim1024 · 11-06-2013, 12:41 PM

Quote:

Originally Posted by jeebus

I like the sound personally.

But it's when I hear this that I loose power.. so it's negative reinforcement. Are you gaining power?

mike_ekim1024 · 11-06-2013, 12:59 PM

Quote:

Originally Posted by endrswrd

The sound your hearing is coming from large overlap made possible by the AVCS system. When trying to maximize power on these cars you run alot of overlap before and drop it off then ramp back up through the TQ dip to minimize the valley itself. I have only been tinkering with it for a few hours since I just got ECUflash beta last week.

But dropping the overall overlap and smoothing out the ramping up and down makes this go away almost completely without effecting the reduction in the tq dip.

Aha.. I knew a little about AVCS but you've got me researching now. This sums it up pretty good if anyone else is interested: http://drive2.subaru.com/Win05_WhatsInside.htm

Thanks!

jeebus · 11-06-2013, 01:01 PM

Quote:

Originally Posted by mike_ekim1024

But it's when I hear this that I loose power.. so it's negative reinforcement. Are you gaining power?

oh...ya it's when my power goes weeeeeeeeeeeee right at 4k (thanks to my tune)

Zach3794 · 11-06-2013, 03:17 PM

First day I drove home with my (at the time) new tune and noticed the sound, I was a bit nervous. Now I think it's awesome! I confirmed with my tuner, it is indeed from messing with the timing. All I know is, I've got a lot more power in the dip than I did before...

11-06-2013, 11:14 AM	#3
jeebus Senior Member Join Date: Jul 2012 Drives: 2015 Mustang GT (on order) Location: San Diego Posts: 904 Thanks: 114 Thanked 471 Times in 208 Posts Mentioned: 9 Post(s) Tagged: 0 Thread(s)	I like the sound personally. __________________

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11-06-2013, 10:28 AM	#2
endrswrd Member Join Date: Jul 2013 Drives: 2013 LTD BRZ Location: Dayton Ohio Posts: 49 Thanks: 0 Thanked 16 Times in 12 Posts Mentioned: 1 Post(s) Tagged: 0 Thread(s)	The sound your hearing is coming from large overlap made possible by the AVCS system. When trying to maximize power on these cars you run alot of overlap before and drop it off then ramp back up through the TQ dip to minimize the valley itself. I have only been tinkering with it for a few hours since I just got ECUflash beta last week. But dropping the overall overlap and smoothing out the ramping up and down makes this go away almost completely without effecting the reduction in the tq dip.

11-06-2013, 03:17 PM	#7
Zach3794 Senior Member Join Date: Mar 2013 Drives: 2013 Scion FR-S, Raven, Manual Location: Vista, CA Posts: 396 Thanks: 81 Thanked 143 Times in 101 Posts Mentioned: 8 Post(s) Tagged: 0 Thread(s)	First day I drove home with my (at the time) new tune and noticed the sound, I was a bit nervous. Now I think it's awesome! I confirmed with my tuner, it is indeed from messing with the timing. All I know is, I've got a lot more power in the dip than I did before...

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