Exhaust...

97SierraStepSde · 07-31-2007, 08:48 PM

ok need some more input. 2000 Silverado 4.8L. Guys from Summit told me theres really no gain from taking my cat out.. possibility that he was just saying that so I wouldnt make my truck illegal! haha so here it is:

Opinions & Facts please:

Cats out - check engine light? better sound? more power?
Cats in - keep it legal and miss out?

scottie · 08-01-2007, 11:11 AM

the honeycomb cats are not a restriction, those huge carbon ones are, though

scottie · 08-01-2007, 11:14 AM

removing your cats will not give you anything besides a check engine light. your 02 sensors will go crazy and your truck will run like dump, especially on a newer truck like that. go for headers and muffler if thats what you looking for, leave the cat there......... my 2 cents

75K30 · 08-01-2007, 04:28 PM

Here is the skinny on cat removal. The small displacement einging will not see much of a benefit from cat removal. Given the compression and cam size, it is only capable of displacing so much air. Taking the cats off won't make the engine move more air. An engine is really a very good air pump. If you increased the size of the pistons, and increased the size of the intake / exhaust ports and the valves, and the throttle body, making the exhaust bigger will not do a whole bunch on an engine of that displacement.
Let me give you an example: Take a Briggs 5 hp engine, and put a big old car muffler on it, and see how much more horsepower it makes. Gonna make 5 Hp. See the larger exhaust will not help the little motor. If that were the case, all we would have to do would be to use a little engne with a monster exhaust, and we know that does not work.
Now take a 1000 Hp BBC and install the same muffler, and it might loose a ton of HP, but install a bigger muffler and it will not make more than the compression and displacement will allow.
The little engine you have is a decent little engine, but is too small to be affected by butchering the exhaust. I doubt you will se any sugnificant increase in power.
I agree with the guys at Summit.

97SierraStepSde · 08-02-2007, 01:36 AM

ok so if I do anything with my cats just get a new "hi flow" or Magnaflow or any replacement honeycomb style cat?

and thank u all 4 ur input it was much appreciated and in about a month or so Ill let u know my decision and how it runs :-D

07-31-2007, 08:48 PM	#1
97SierraStepSde Senior Member Join Date: Nov 2006 Posts: 106	Exhaust... ok need some more input. 2000 Silverado 4.8L. Guys from Summit told me theres really no gain from taking my cat out.. possibility that he was just saying that so I wouldnt make my truck illegal! haha so here it is: Opinions & Facts please: Cats out - check engine light? better sound? more power? Cats in - keep it legal and miss out? __________________ Ride Til I Die

08-01-2007, 11:11 AM	#2
scottie Senior Member Join Date: Jan 2006 Location: South Florida (Palm Beach), originally from south of BOSTON Posts: 644	the honeycomb cats are not a restriction, those huge carbon ones are, though __________________ im a straight shooter with upper management written all over me

08-01-2007, 11:14 AM	#3
scottie Senior Member Join Date: Jan 2006 Location: South Florida (Palm Beach), originally from south of BOSTON Posts: 644	removing your cats will not give you anything besides a check engine light. your 02 sensors will go crazy and your truck will run like dump, especially on a newer truck like that. go for headers and muffler if thats what you looking for, leave the cat there......... my 2 cents __________________ im a straight shooter with upper management written all over me

08-02-2007, 01:36 AM	#5
97SierraStepSde Senior Member Join Date: Nov 2006 Posts: 106	ok so if I do anything with my cats just get a new "hi flow" or Magnaflow or any replacement honeycomb style cat? and thank u all 4 ur input it was much appreciated and in about a month or so Ill let u know my decision and how it runs :-D __________________ Ride Til I Die

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08-01-2007, 04:28 PM	#4
75K30 Senior Member Join Date: Jul 2006 Posts: 2,992	Here is the skinny on cat removal. The small displacement einging will not see much of a benefit from cat removal. Given the compression and cam size, it is only capable of displacing so much air. Taking the cats off won't make the engine move more air. An engine is really a very good air pump. If you increased the size of the pistons, and increased the size of the intake / exhaust ports and the valves, and the throttle body, making the exhaust bigger will not do a whole bunch on an engine of that displacement. Let me give you an example: Take a Briggs 5 hp engine, and put a big old car muffler on it, and see how much more horsepower it makes. Gonna make 5 Hp. See the larger exhaust will not help the little motor. If that were the case, all we would have to do would be to use a little engne with a monster exhaust, and we know that does not work. Now take a 1000 Hp BBC and install the same muffler, and it might loose a ton of HP, but install a bigger muffler and it will not make more than the compression and displacement will allow. The little engine you have is a decent little engine, but is too small to be affected by butchering the exhaust. I doubt you will se any sugnificant increase in power. I agree with the guys at Summit.

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