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12-16-2006, 02:57 AM
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Hummer Guru
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Join Date: Oct 2005
Location: Charlotte, NC
Posts: 2,767
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Re: Exhaust?
Is there really a big difference that would justify messin' with the cats? I honestly don't remember ever seeing any performance gains by removing normally operating cats.
Just wondering.... hate to see you spend a bunch of extra money for no benefit.
Mark
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12-16-2006, 03:32 AM
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Hummer Authority
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Join Date: Sep 2005
Location: Texas
Posts: 1,795
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Re: Exhaust?
I think you'd be better off getting custom mapping done on your ECM. If you don't have it already, it's probably running too lean with what you have there.
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12-16-2006, 11:44 AM
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Hummer Professional
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Join Date: Aug 2005
Posts: 258
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Re: Exhaust?
I have modified my cats with sports steel cats.
The difference is very big and the test about exhaust gas is ok for the law.

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12-16-2006, 01:50 PM
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Hummer Professional
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Join Date: Jul 2005
Location: New Jersey
Posts: 255
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Re: Exhaust?
Quote:
Originally Posted by Ernie Italy
I have modified my cats with sports steel cats.
The difference is very big and the test about exhaust gas is ok for the law.

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Ernie, very interested in this Turmax....is it available in th US. All my searches come up in Italian.
Do these effect the sound?
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12-16-2006, 02:32 PM
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Hummer Professional
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Join Date: Aug 2005
Posts: 258
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Re: Exhaust?
Quote:
Originally Posted by HUM GOOD
Ernie, very interested in this Turmax....is it available in th US. All my searches come up in Italian.
Do these effect the sound?
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A little bit...the sound is more breathe and "open". Not loud... I like it
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12-16-2006, 01:54 PM
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Hummer Professional
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Join Date: Jul 2005
Location: New Jersey
Posts: 255
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Re: Exhaust?
Quote:
Originally Posted by tomp
I think you'd be better off getting custom mapping done on your ECM. If you don't have it already, it's probably running too lean with what you have there.
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Custom mapping has been done already......i just feel the motor is taking in LOTS of air and not leaving fast enough.
I am also hoping to richin the sound up a little more. Don't get me wrong...the borla sound awful sweet....maybe one or two octives will satisfy me. ARE WE EVER SATISFIED? DO WE EVER GET ENOUGH?
Prolly not!!!!!!! 
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12-16-2006, 06:00 PM
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Hummer Authority
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Join Date: Sep 2005
Location: Texas
Posts: 1,795
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Re: Exhaust?
Anytime you open up the exhuast flow, you drop back pressure which is going to reduce your low end performance. It's a trade-off
Most exaust companies focus on wide-open performance numbers and not on the low-end. I ended up trashing my first exhaust system to go with one that had better low-end performance.
Also, it may be a good idea to swap out the MAF sensor for one that can meter the air better. The OEM unit can only meter within a certain range of air and you may be outside of that range if you have not changed it out.
If your exhaust is true duals, you may benefit from a cross over tube slightly smaller than the main exhaust pipes. This will give you some low-end back.
Quote:
Originally Posted by HUM GOOD
Custom mapping has been done already......i just feel the motor is taking in LOTS of air and not leaving fast enough.
I am also hoping to richin the sound up a little more. Don't get me wrong...the borla sound awful sweet....maybe one or two octives will satisfy me. ARE WE EVER SATISFIED? DO WE EVER GET ENOUGH?
Prolly not!!!!!!! 
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12-16-2006, 11:31 PM
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Hummer Professional
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Join Date: Jul 2005
Location: New Jersey
Posts: 255
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Re: Exhaust?
Quote:
Originally Posted by tomp
Anytime you open up the exhuast flow, you drop back pressure which is going to reduce your low end performance. It's a trade-off
Most exaust companies focus on wide-open performance numbers and not on the low-end. I ended up trashing my first exhaust system to go with one that had better low-end performance.
Also, it may be a good idea to swap out the MAF sensor for one that can meter the air better. The OEM unit can only meter within a certain range of air and you may be outside of that range if you have not changed it out.
If your exhaust is true duals, you may benefit from a cross over tube slightly smaller than the main exhaust pipes. This will give you some low-end back.
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I dont have true duals, just catback borla. I want to go with the true duals but need to purchase another cat. So that whats leading me to look into my options. When the trues are put on I will also add the "H" pipe in also.
I haven't swapped out the MAF sensor. Who sells it and do you have a part #.
Thanks lots!
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12-19-2006, 11:05 PM
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Hummer Authority
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Join Date: Sep 2005
Location: Texas
Posts: 1,795
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Re: Exhaust?
Which air intake do you have?
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12-21-2006, 02:49 AM
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Hummer Professional
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Join Date: Jul 2005
Location: New Jersey
Posts: 255
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Re: Exhaust?
Quote:
Originally Posted by tomp
Which air intake do you have?
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The K&N
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12-21-2006, 05:48 AM
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Hummer Messiah
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Join Date: Apr 2003
Location: Virginia Beach
Posts: 37,474
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Re: Exhaust?
Quote:
Originally Posted by OrangeCrush
Is there really a big difference that would justify messin' with the cats? I honestly don't remember ever seeing any performance gains by removing normally operating cats.
Just wondering.... hate to see you spend a bunch of extra money for no benefit.
Mark
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I was told point-blank by three shops the "hi-flow" cats were no better than what we have already. I forgot the flow numbers and what the cell configuration is for the hi-perf cats, but it was all the same as our stock cats.
LPE didn't even offer them to us for our last truck with their engine in it.
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