What did you do to your NBS GMT800 Tahoe/Yukon Today?

[Sam Harris]

Getting sick of my drone at 2k. Talked to my exhaust guy and he wanted to take the easy route, and just use a GMT900 resonator...

So we did that.






Just barely fits..

Drove off and knew immediately I didn’t like it. Cuts way too much sound and I’m looking for just limiting the drone at 2k.

Called him back and told him I want a helmholtz resonator as @iamdub has been talking about testing out. So this weekend (hopefully), we’re going to build a 25.2” helmholtz resonator and see how that works... @iamdub, does the 25.2” calculation work on a curved tube? I don’t have a lot of room to the side, so it’s going to be a curve, to a straight chamber, which will sit along side the cat-back portion of the factory exhaust. Not sure if I need to make the chamber 25.2”, or if that includes the curved portion of the resonator.

 

[Ftrsavage]

Quick update, I haven’t been posted since 2017-2018. Went from factory wheels and tires to some 24” replicas today. Installed new headlights and bumper lights. 2 12” subwoofers and a pioneer head unit.

3/5 Lowering kit and exhaust coming soon. Repainting the grille surround today. Waiting on led smoked taillights, led fog lights, nnbs shifter and 0 gauge amp wiring kit in the mail.

UPS and the Mail man need to hurry the hell up.

 

[Doubeleive]

Is this all I need to add the turn signal power fold mirrors or do I need the passenger door switch also?

 

[Tonyrodz]

Is this all I need to add the turn signal power fold mirrors or do I need the passenger door switch also?

View attachment 252661

You don't need the passenger side. Do you have the proper driver side switch? Those the correct DL3 mirrors?

 

[Doubeleive]

You don't need the passenger side. Do you have the proper driver side switch? Those the correct DL3 mirrors?

ya I saved the mirrors off of my 03 and got the switch today out of a 03 tahoe with power fold/turn signal I am going to put them in the 05 should be plug-n-play just wasn't sure on the passenger switch

 

[Tonyrodz]

ya I saved the mirrors off of my 03 and got the switch today out of a 03 tahoe with power fold/turn signal I am going to put them in the 05 should be plug-n-play just wasn't sure on the passenger switch

Let me know if it's truly pnp. I tried to do this in my 03 and couldn't get it to work. @Sam Harris tried helping me too. I did get the turn signals in the mirror to work tho.

 

[Doubeleive]

Let me know if it's truly pnp. I tried to do this in my 03 and couldn't get it to work. @Sam Harris tried helping me too. I did get the turn signals in the mirror to work tho.

did you use the right switch? and were the mirrors power fold? if they were then the only other thing I can think of is maybe a updated bcm calibration would be needed

 

[Tonyrodz]

did you use the right switch? and were the mirrors power fold? if they were then the only other thing I can think of is maybe a updated bcm calibration would be needed

Yes to both.
This is the correct switch that you need.

 

[Doubeleive]

Yes to both. View attachment 252674 View attachment 252675
This is the correct switch that you need.

ya that's the switch I picked up today, the one in my 03 didn't have the light in the middle though

 

[iamdub]

Getting sick of my drone at 2k. Talked to my exhaust guy and he wanted to take the easy route, and just use a GMT900 resonator...

So we did that.

Just barely fits..

Drove off and knew immediately I didn’t like it. Cuts way too much sound and I’m looking for just limiting the drone at 2k.

Called him back and told him I want a helmholtz resonator as @iamdub has been talking about testing out. So this weekend (hopefully), we’re going to build a 25.2” helmholtz resonator and see how that works... @iamdub, does the 25.2” calculation work on a curved tube? I don’t have a lot of room to the side, so it’s going to be a curve, to a straight chamber, which will sit along side the cat-back portion of the factory exhaust. Not sure if I need to make the chamber 25.2”, or if that includes the curved portion of the resonator.

First off, I'm not so sure the placement of that resonator is ideal. A resonator targets and cancels specific frequencies. If your muffler "filters" out certain frequencies and passes others (what you'd hear at the tailpipe), then placing it after the muffler makes more sense, as it is in factory form. Those frequencies may not be present or as present before the muffler, so the resonator may not be operating as designed. Remember, it's just a Helmholtz chamber rolled back along itself. I just don't know how to determine it's target frequency. On the other hand, before or after the muffler may not matter since it could still be working. But, whatever frequencies it doesn't cancel (like all the ones you wanna still hear) are being muffled after the fact and that's why it's now too quiet. Just thinking out loud here.

For the tube, ideally you want it perpendicular to the exhaust pipe. But, if you must, keep the bends to a minimum. One 90° will be just fine and should be all you need at most. On mine, the stock Y-pipe merged together just in front of a cross member. Putting the tube parallel with the crossover pipe coming off the LH bank would be convenient for packaging and it'd connect just after where the two pipes became one. Now that I think of it, I think the Y-pipe of the NBS had two separate pipes further downstream before they merged. So, if there's no convenient place to put it perpendicular, then make it shaped like a "J" with the short leg of the "J" as short as possible (so the tube will be tight to the exhaust pipe). The wave will be slowed slightly by the bend, altering the tuning frequency. I don't think it'll be enough to make much of a difference. I don't know how many dBs per octave it's slope is, but I know it's fairly steep. Be as accurate as you can with your calculations and building it'll be plenty effective.

By the way, have you crunched the numbers to double-check my napkin math? I found this vid that explains the formula:

I forgot what temperature I used in my calcs, but you should measure yours to be accurate, anyway. Temperature plays a major role in the speed of sound and can make this a complete waste if you're off.

Also, for bonus points, download a free dB meter/sound analyzer app to do some before and after measurements so you'll have hard numbers to reference and post rather than just going by ear.