What did you do to your NNBS GMT900 Tahoe/Yukon Today?

[aflumb]

Well I had to take the Tahoe to drop off the family of one of our troops at the airport. On the way home I blew the right front tire. (It was only a matter of time). Took them all off and ordered a new set.

Blown sidewall

Also picked up a nail in the left front also tire was shot

The last two where also cracking


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[Tonyrodz]

Well I had to take the Tahoe to drop off the family of one of our troops at the airport. On the way home I blew the right front tire. (It was only a matter of time). Took them all off and ordered a new set.

Blown sidewall

Also picked up a nail in the left front also tire was shot

The last two where also cracking


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Just crappy tires, or were they just old? Did you hit a pot hole for the sidewall to blow out like that?

 

[07Burb]

Is why I replace my tires well before they're worn out. Do not want a blow out at highway speeds!

 

[aflumb]

Just crappy tires, or were they just old? Did you hit a pot hole for the sidewall to blow out like that?

Both. I knew it was a matter of time. The sidewalks where questionable when I got them (used rims and tires)

Luckily I knew it was going down


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[aflumb]

Is why I replace my tires well before they're worn out. Do not want a blow out at highway speeds!

Yea I would to. But out of all the rims I have installed I have never bought but 2 sets of tires. This will be the third.


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[Tonyrodz]

Yea I would to. But out of all the rims I have installed I have never bought but 2 sets of tires. This will be the third.


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What are they? 22's or bigger? Pics of them?

 

[the_tool_man]

Nah. I've been wanting someone with a droning issue to try fixing it with tuned resonator(s). Basically, you calculate a formula to determine the length of tube(s) needed then weld it/them to your exhaust. You keep your muffler, it's volume, etc. but single out and attack the offending tones. I recently put a 14" muffler on my brother's truck and was actually hoping for drone. So far, he says there is none.

*EDIT*
It's called a Helmholtz chamber and it'd be something like this (internet pics):

It doesn't have to be straight the whole way, just 90° where it meets the main pipe.

Dual chambers (because dual exhaust on Mustang) :

iamdub beat me to it...sort of. The term for what's in that photo is a quarter-wave attenuator, which is a specific type of Helmholtz chamber tuned to damp sound at a specific frequency. You have to know the engine RPM where you want the damping to occur. And you calculate the length of the pipe based on the "time of flight" of a pressure pulse down and back to the mouth of the attenuator. The goal is for a peak to arrive as a valley passes by in the main tube, and vice versa. I installed a set on my Mustang Cobra after I put Flowmasters on, and was getting a pretty severe drone at 2500rpm...right at cruising speed with my 3.73 gears.

They reduced the sound by 4dB, according to the sound meter app on my phone, which is more than half attenuation. They have to be tuned for a single frequency though. If you're getting drone at a wide range, this won't completely resolve the issue. Also, remember that the density of the exhaust gasses varies pretty dramatically with temperature. So you have to guess (or measure) an exhaust gas temperature for best results.

***EDIT*** I mis-remembered it was 4dB not 8 (corrected).

 

[aflumb]

What are they? 22's or bigger? Pics of them?

24’s

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[07Burb]

iamdub beat me to it...sort of. The term for what's in that photo is a quarter-wave attenuator, which is a specific type of Helmholtz chamber tuned to damp sound at a specific frequency. You have to know the engine RPM where you want the damping to occur. And you calculate the length of the pipe based on the "time of flight" of a pressure pulse down and back to the mouth of the attenuator. The goal is for a peak to arrive as a valley passes by in the main tube, and vice versa. I installed a set on my Mustang Cobra after I put Flowmasters on, and was getting a pretty severe drone at 2500rpm...right at cruising speed with my 3.73 gears.

View attachment 230103

They reduced the sound by 8dB, according to the sound meter app on my phone, which is more than two-thirds attenuation. They have to be tuned for a single frequency though. If you're getting drone at a wide range, this won't completely resolve the issue. Also, remember that the density of the exhaust gasses varies pretty dramatically with temperature. So you have to guess (or measure) an exhaust gas temperature for best results.

dang....that's a science lesson right there. I'm not smart enough for such things LOL

 

[the_tool_man]

Here is the original thread on corral.net where I first learned of it. My results are posted on page 6 (same userID):

https://forums.corral.net/forums/general-mustang-tech/496793-exhaust-drone-completely-gone-6.html

Keep in mind, that car was dual exhaust. So the frequency in each pipe is half what it will be for a single exhaust like on our SUVs.

I got some strange looks when I parted that car out and went to sell the h-pipe. No one wanted it, or believed me when I said it worked. The guy I sold it to was a drag racer, who said he was going to cut them off and weld the holes shut. Oh well.

 

[iamdub]

iamdub beat me to it...sort of. The term for what's in that photo is a quarter-wave attenuator, which is a specific type of Helmholtz chamber tuned to damp sound at a specific frequency. You have to know the engine RPM where you want the damping to occur. And you calculate the length of the pipe based on the "time of flight" of a pressure pulse down and back to the mouth of the attenuator. The goal is for a peak to arrive as a valley passes by in the main tube, and vice versa. I installed a set on my Mustang Cobra after I put Flowmasters on, and was getting a pretty severe drone at 2500rpm...right at cruising speed with my 3.73 gears.

View attachment 230103

They reduced the sound by 4dB, according to the sound meter app on my phone, which is more than half attenuation. They have to be tuned for a single frequency though. If you're getting drone at a wide range, this won't completely resolve the issue. Also, remember that the density of the exhaust gasses varies pretty dramatically with temperature. So you have to guess (or measure) an exhaust gas temperature for best results.

***EDIT*** I mis-remembered it was 4dB not 8 (corrected).

Easy now! You don't wanna scare him off with the deep 'n' nerdy stuff right off the bat. You gotta test the waters first. I think @R3cord303 is game, though.

Beautiful pipe work on that 'Stang.

 

[Doubeleive]

Well I don't know what temp cat's are normally or what they should be but the thermometer says anywhere from 300-400 depending on where I pointed it, tech2 says 3way is 775 on each, what about these long term fuel trims?

 

[R3cord303]

Easy now! You don't wanna scare him off with the deep 'n' nerdy stuff right off the bat. You gotta test the waters first. I think @R3cord303 is game, though.

Beautiful pipe work on that 'Stang.

Will add it into the design. At some point i’ll actually do the math and figure out tubing diameter, cfm, what to do for size/length of these chamber doodads

 

[kbuskill]

Will add it into the design. At some point i’ll actually do the math and figure out tubing diameter, cfm, what to do for size/length of these chamber doodads

Here is something to get you started...

Hope it helps.

PS... most people think they need bigger pipe than what is actually necessary.

 

[gooffeyguy]

Well damn, my 600hp mustang only has a 2.5" dual exhaust system.

Maybe I'll get 20 more hp if I up it to 3", 50 more hp if it's painted red

2001 Yukon SLT
2012 Yukon Denali XL
2011 Yukon Denali RIP 5/20/18

 

[07Burb]

Well damn, my 600hp mustang only has a 2.5" dual exhaust system.

Maybe I'll get 20 more hp if I up it to 3", 50 more hp if it's painted red

2001 Yukon SLT
2012 Yukon Denali XL
2011 Yukon Denali RIP 5/20/18

and don't even talk about if you added neon to the underside

 

[mikeyss]

Don't forget, you need this too!

 

[Doubeleive]

well from what I have read the cat temps seem to be pretty normal, on the freeway they ran in the 1500's both of them dead even same temp no matter what it was, fuel trims seem to be normal, all 4 02 sensors seem to be normal also, so i'm stumped.

 

[kbuskill]

well from what I have read the cat temps seem to be pretty normal, on the freeway they ran in the 1500's both of them dead even same temp no matter what it was, fuel trims seem to be normal, all 4 02 sensors seem to be normal also, so i'm stumped.

Perhaps you have gained weight in your right foot.

 

[wjburken]

well from what I have read the cat temps seem to be pretty normal, on the freeway they ran in the 1500's both of them dead even same temp no matter what it was, fuel trims seem to be normal, all 4 02 sensors seem to be normal also, so i'm stumped.

I know it’s a dumb question but have you checked the dashboard estimated mpg with the manual method of fill tank, drive, refill tank and do the math?