Stock Exhaust What part is the most restrictive?
02-21-2006, 10:40 AM
#1
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Stock Exhaust What part is the most restrictive? Just wondering are the stock cats really restrictive?
Does anyone have any hp/ET number gains from deleting cats?
Z is a 2001
Does anyone have any hp/ET number gains from deleting cats?
Z is a 2001
02-21-2006, 10:43 AM
#2
The entire exhaust is basically restrictive. The stock manifolds are shorty's and are restrictive and the muffler as well as smaller diameter piping are restrictive. You can buy high flow cats that will flow better than stock cats but I don't imagine much of a gain from them. I've heard like a 5-10hp gain from deleting cats which is like not even really noticible. You could get Long Tube Headers, an Off-Road or Catted Y-Pipe, a nice Catback such as GMMG, Borla, Magnaflow etc. and pick up some real horsepower! You could also convert to True Duals and pick up even more power yet.
Last edited by StealthFormula; 02-21-2006 at 10:52 AM.
02-21-2006, 10:51 AM
#3
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Originally Posted by ilirw325
Just wondering are the stock cats really restrictive?
Does anyone have any hp/ET number gains from deleting cats?
Z is a 2001
Does anyone have any hp/ET number gains from deleting cats?
Z is a 2001
The stock muffler IS restrictive and a replacement catback will see maybe 5-10rwhp. It will also improve throttle response.
The stock cats however are also a restriction as is the 2.5" mid pipe (but to a lesser extent on an otherwise stock car). You may see anohter 5rwhp or so by replacing the cats with hi-flow ones. The biggest gains however are in the manifolds, long tube headers will flow better than stock, but more importantly allow scavenging.
A full LT, catted 3" Y and catback should be good for anywhere from 20-30rwhp.
But to see the gain you need to address all area's. Think of it as a river with a series of dam's. By removing one you will increase the flow locally to it, but over all there will still be obsticles.
IMO, get a nice cat back 1st. Then look at some LT's with a good catted Y or ORY if you don't want to do the whole thing at once.
02-21-2006, 11:22 AM
#5
I've heard numbers closer to 1-3hp for deleting cats. Nowadays they just aren't the restriction they used to be. All things considered, the stock Y-pipe is probably the most restrictive, followed by the muffler and manifolds. Replacing just one though doesn't do much without the rest of the system flowing as well (which is why an SLP y-pipe is pretty much a waste)
02-21-2006, 11:27 AM
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I would have to say the y pipe since it gets smased down almost flat at one point. If your not worried about having cats i would get lts and y pipe if your short on cash just dump it with an exaust cut out. If you dont have a big money restriction get lts with true dules.
02-21-2006, 11:55 AM
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I've heard that you don't get much by replacing the stock Y by itself. Although GM squished it for clearance, the flow by going to a round pipe is barely better. It's one part that GM actually engineered to not cost power, even though it may not look like it.
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02-21-2006, 03:57 PM
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Originally Posted by Aegnor
I've heard that you don't get much by replacing the stock Y by itself. Although GM squished it for clearance, the flow by going to a round pipe is barely better. It's one part that GM actually engineered to not cost power, even though it may not look like it.
Exactly...It all depends on your plans for the car. If you plan on sticking with the stock exhaust manifolds, then the stock 2.5" pancake y-pipe has been proven to NOT be a restriction. A good catback should add over 10 rwhp, and high flow cats or an o/r pipe will add a few more, with stock manifolds. If you go with longtubes, which are probable the best hp gain, you will have to replace the y-pipe anyways. As far as the biggest restriction, on a stock car it would be pretty close between the exhaust manifolds and catback. The y-pipe ISN'T a restriction on a stock car, and isn't even in the equation.
Last edited by Redneck Z; 02-21-2006 at 04:03 PM.
02-21-2006, 05:43 PM
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Ive seen the dyno sheets that have shown 10rwhp and 10tq by just hollowing out the stock cats. This was on a car w/ a lid and an SLP loudmouth. Same dyno. Given that the same car will dyno different on different days Id say the gutted cats were worth th least 7hp to the wheels.
03-06-2006, 04:04 PM
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Originally Posted by 300bhp/ton
Well you need to look at the whole thing as a setup. Essentially the catback is one item and often the first to be replaced.
The stock muffler IS restrictive and a replacement catback will see maybe 5-10rwhp. It will also improve throttle response.
The stock cats however are also a restriction as is the 2.5" mid pipe (but to a lesser extent on an otherwise stock car). You may see anohter 5rwhp or so by replacing the cats with hi-flow ones. The biggest gains however are in the manifolds, long tube headers will flow better than stock, but more importantly allow scavenging.
A full LT, catted 3" Y and catback should be good for anywhere from 20-30rwhp.
But to see the gain you need to address all area's. Think of it as a river with a series of dam's. By removing one you will increase the flow locally to it, but over all there will still be obsticles.
IMO, get a nice cat back 1st. Then look at some LT's with a good catted Y or ORY if you don't want to do the whole thing at once.
The stock muffler IS restrictive and a replacement catback will see maybe 5-10rwhp. It will also improve throttle response.
The stock cats however are also a restriction as is the 2.5" mid pipe (but to a lesser extent on an otherwise stock car). You may see anohter 5rwhp or so by replacing the cats with hi-flow ones. The biggest gains however are in the manifolds, long tube headers will flow better than stock, but more importantly allow scavenging.
A full LT, catted 3" Y and catback should be good for anywhere from 20-30rwhp.
But to see the gain you need to address all area's. Think of it as a river with a series of dam's. By removing one you will increase the flow locally to it, but over all there will still be obsticles.
IMO, get a nice cat back 1st. Then look at some LT's with a good catted Y or ORY if you don't want to do the whole thing at once.
03-06-2006, 04:06 PM
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Originally Posted by 300bhp/ton
Well you need to look at the whole thing as a setup. Essentially the catback is one item and often the first to be replaced.
The stock muffler IS restrictive and a replacement catback will see maybe 5-10rwhp. It will also improve throttle response.
The stock cats however are also a restriction as is the 2.5" mid pipe (but to a lesser extent on an otherwise stock car). You may see anohter 5rwhp or so by replacing the cats with hi-flow ones. The biggest gains however are in the manifolds, long tube headers will flow better than stock, but more importantly allow scavenging.
A full LT, catted 3" Y and catback should be good for anywhere from 20-30rwhp.
But to see the gain you need to address all area's. Think of it as a river with a series of dam's. By removing one you will increase the flow locally to it, but over all there will still be obsticles.
IMO, get a nice cat back 1st. Then look at some LT's with a good catted Y or ORY if you don't want to do the whole thing at once.
The stock muffler IS restrictive and a replacement catback will see maybe 5-10rwhp. It will also improve throttle response.
The stock cats however are also a restriction as is the 2.5" mid pipe (but to a lesser extent on an otherwise stock car). You may see anohter 5rwhp or so by replacing the cats with hi-flow ones. The biggest gains however are in the manifolds, long tube headers will flow better than stock, but more importantly allow scavenging.
A full LT, catted 3" Y and catback should be good for anywhere from 20-30rwhp.
But to see the gain you need to address all area's. Think of it as a river with a series of dam's. By removing one you will increase the flow locally to it, but over all there will still be obsticles.
IMO, get a nice cat back 1st. Then look at some LT's with a good catted Y or ORY if you don't want to do the whole thing at once.
