HF cats vs cat eliminators

[1st Gen Forever]

With defective parts, I've had more time to surf the net this weekend vs working on my build and something significant dawned on me. As I've been researching other 700rwhp ZL1 builds, I'm seeing something in common. It seems the most power is being made WITHOUT catalytic converters.

My build will be using Stainless Works high flow cats but now I'm really curious what difference there is in power between HF cats and open pipes with stock exhaust the rest of the way back. Is that how some of the builds are getting the high numbers and into the 9s in the quarter with the ZL1 like the Livernois car?

Anyone know if running without high flow cats on the track is really worth the hassle of removing them from a street car?

[hognutz]

You will get more fuel smell and more exhaust sound. I don't know what cats stainless works uses but I know companies like random technologies make cats that flow really high cfm. Some of the cats flow so much you will get a cel anyway. So they will defiantly flow tons if air but it is another item in the exhaust.

if I was gunning for 9's I would save the $$$ and skip the cats.

[Drew P]

My setup is running gutted stock cats. The exhaust is much louder for sure. On a mild bolt on setup (no head/cam work), picked up about 50 rwhp. Before this, backpressure from cats was causing knocking, and limited tune. Still using stock exhaust manifolds. You will also get a lot of carbon build up on the exhaust tips.

[adamgl]

Originally Posted by Drew P

My setup is running gutted stock cats. The exhaust is much louder for sure. On a mild bolt on setup (no head/cam work), picked up about 50 rwhp. Before this, backpressure from cats was causing knocking, and limited tune. Still using stock exhaust manifolds. You will also get a lot of carbon build up on the exhaust tips.

You mean 5? Or 50 total with the other bolt ons? A cat delete vs. high flows is usually only worth a few HP.

[sykb47l]

Also with increase boost cats start to fail. Clogged cats can lead to engine failure. Most people dont daily drive 9 second cars so not having cats isnt as annoying as it seems.

[1st Gen Forever]

So I'm hearing 2 to 4 HP increase switching from SW high flow cats to cat eliminators. Probably not worth it. And yea, I expect the cats may not live as long as a stock ZL1. Same with my supercharger, spark plugs, valve springs, etc...

All part of the game!

[hognutz]

Originally Posted by 1st Gen Forever

So I'm hearing 2 to 4 HP increase switching from SW high flow cats to cat eliminators. Probably not worth it. And yea, I expect the cats may not live as long as a stock ZL1. Same with my supercharger, spark plugs, valve springs, etc...

All part of the game!

That is consitant to what I have read. the real issue is how long they will last and the cost of replacements. the delete pipes are a one time cost never go bad.

I am wreslting with this same decision. I might go with kooks instead of stainless works but same decision on the cats. I keep going back to the less $$$ part for some reason.

[jimmy5]

I would delete the cats and just be done with it. Like it's said, they dont handle increased boost worth a damn

[RoketRdr]

Originally Posted by 1st Gen Forever

With defective parts, I've had more time to surf the net this weekend vs working on my build and something significant dawned on me. As I've been researching other 700rwhp ZL1 builds, I'm seeing something in common. It seems the most power is being made WITHOUT catalytic converters.

My build will be using Stainless Works high flow cats but now I'm really curious what difference there is in power between HF cats and open pipes with stock exhaust the rest of the way back. Is that how some of the builds are getting the high numbers and into the 9s in the quarter with the ZL1 like the Livernois car?

Anyone know if running without high flow cats on the track is really worth the hassle of removing them from a street car?

Keep in mind that your car won't pass emissions or inspection without cats. Plenty of high horsepower boosted street cars out there running high flow cats with no issues. Like you said there are only a few HP to be had so not worth the trouble of putting cats back on the car just to pass inspection.

[adamgl]

I'd get a full system like American racing headers and X pipe and be done with it. You can get them with high flow cats or no cats for a few hundred $ less.

And you can pass inspection without them, just depends on how good you know the guy doing it, lol.

[Dave Coyle]

I'm running the Kooks 1 7/8 LT Headers with Kooks Hi-flo cats and have had no issues but I am NA and not SC. I do know a couple people that are SC running close to 600 RWHP with the same cats and are having no problems also.