Catted vs Catless Headers Power Gains differences

[Summerwolf]

Originally Posted by Jyn

You are right that it's "not the same," however, it meets the DOT's specifications.

There's multiple ways to solve a mathematical equation, but so long as the combination of variables gives the correct solution, is that not what matters? Same principle with the HIDs.

As for the HFC, totally agree that only having 1 HFC in front pipe < 2 HFC < 2 OEM cat. converters. It just becomes someone's preference in where they draw the line with respect to their own personal preference. I'm simply stating a case for my position, but I don't mean to say mine is the end-all-be-all.

Wrong. Otherwise the manufacturers would use the same projector between halogen and HID versions of the same headlight.


Also, wrong on the math front. Just look at common core tests.


I think you're still missing the point.....

[Jyn]

You're right. I'm wrong. Sorry for being the stupid.

[bfrank1972]

Just adding my 2 cents, I actually run an aftermarket long tube catted EL header:

1) Quite a noticeable gain over stock, so for those who are estimating just a few HP over a stock catted header because "both headers have cats", you're quite incorrect.

2) Why are we always quoting +15 hp, or +25 hp etc. The point of headers on our cars is primarily to improve bottom end and get rid of the disgusting torque dip that our cars have with the stock headers. Additional top end +15 hp is nice, and you'll feel it a bit, but in everyday driving you'll *really* notice the extra +35 ft/lbs at 4000 rpm over the stock header.

I have a P&L catted EL header, 4-1 long tube, the cat sits in the 2nd section of the 'long tube' fairly close to the overpipe. I think discussions here are generalizing header design too much (as most every header discussion does). Dyno charts for the P&L EL header on here show a really nice torque curve for both the catted and uncatted version - with a very minor (maybe 4-5 whp, can't recall exactly) differency with the catted version.

Just FYI, now back to the regularly scheduled program, already in progress.

[steve99]

Originally Posted by nikitopo

Where did you find that the second has larger capacity? I think that the first one in header has 500 cells and aftermarket catted headers have usually 200 or 100 cells (?)

The stock secondary cat is something like 400 cells, aftermarket high flow cats are usually 100-200 cells hence flow better but less effective at converting gasses. From looking at the stock vs aftermarket cats im not 100% on exact specs

Looking ar secondary cat it looks to be similar construction to header cat but is larger,. Hence more surface area so in theroy should be more efficient when up to temperature at converting gasses

Aftermarket high flow cat



Stock cats below

[gtengr]

Originally Posted by bfrank1972

Just adding my 2 cents, I actually run an aftermarket long tube catted EL header:

1) Quite a noticeable gain over stock, so for those who are estimating just a few HP over a stock catted header because "both headers have cats", you're quite incorrect.

I don't think anyone would have disagreed if this conversation was started around the P&L headers. That sort of design and your results also proves the point that the stock front cat location is restrictive.

[bfrank1972]

Originally Posted by gtengr

I don't think anyone would have disagreed if this conversation was started around the P&L headers. That sort of design and your results also proves the point that the stock front cat location is restrictive.

I guess I didn't read the thread well enough - that was the point I was trying to make vs the stock header, sorry about that

[re-animator]

just thinking about hypotheticals here, can someone with more knowledge/experience weigh in?

- What is the power difference hypothetically on the stock header with a gutted cat vs stock header with stock cat? I presume a lot of the gains in an aftermarket cat are just coming from flow restriction being removed with either a high flow or catless design. It makes me suspect at the cost of $1200 headers when you are basically paying for a very similar performance gain to cat delete which costs next to nothing for a track car.

- What is the sound/smell difference would you be looking at with a gutted cat or catless header assuming the stock front pipe is still in place? Sounds like there would be some power there, but the cat in the FP is still doing the heavy lifting with respect to emissions and sound. Does it move the car into "loud" territory and have a catless kind of smell even with the stock FP?

[Razgriz]

Not going to look for it but when I was researching all this. I found somebody here did cut off their cat and there was a very noticeable gain on it. I don't remember the exact numbers but it wasn't what I was looking to do so I didn't care too much.

[gtengr]

Originally Posted by steve99

Aftermarket high flow cat

Here is an HJS cat next to a generic aftermarket. The HJS uses a twisted substrate for greater strength and durability.

[steve99]

Originally Posted by re-animator

just thinking about hypotheticals here, can someone with more knowledge/experience weigh in?

- What is the power difference hypothetically on the stock header with a gutted cat vs stock header with stock cat? I presume a lot of the gains in an aftermarket cat are just coming from flow restriction being removed with either a high flow or catless design. It makes me suspect at the cost of $1200 headers when you are basically paying for a very similar performance gain to cat delete which costs next to nothing for a track car.

- What is the sound/smell difference would you be looking at with a gutted cat or catless header assuming the stock front pipe is still in place? Sounds like there would be some power there, but the cat in the FP is still doing the heavy lifting with respect to emissions and sound. Does it move the car into "loud" territory and have a catless kind of smell even with the stock FP?

If you just knock the insides out of a stock header cat, it will likely perform slightly better than stock.

You wpuld likely get a better result if you cut cat out completly and welded in a pipe see below

Stock header



Stock header with modded cat





Even if you did nod s above it wont be as vood as a good aftermsrket header as the aftermarket catless header will also have changes to the primary tube diameters and lengths and a better collector to move and increase the engine efficiency assuming you get a tune as well

[steve99]

Originally Posted by gtengr

Here is an HJS cat next to a generic aftermarket. The HJS uses a twisted substrate for greater strength and durability.

Most aftermarket cats will be metalisied substrate instead of the stock ceramic material. So they usually cope with vibration and heat better, but are usually less efficient at converting gasses.

[Somerandom18]

Get a used 2017 header for dirt and cut the cat out?

Sent from my Pixel XL using Tapatalk

[vagthomas]

Originally Posted by churchx

gyubo: you forgot also bit, that cats can be replaced only with stock cats if one fails. That strikes out legality-wise aftermarket catted exhaust bits too, even if they still have cats in somewhat old place.
------------
vagthomas:
3) there would be gains. But less then from catless header, as primary cat in header is in "worst" place, hurting flow most and dictating worse/less efficient header design.
Main pro of catless front pipe is ability to run with stock ecu tune without throwing CELs, as sensors are upstream prior it.
But then again imho it makes little sense to pay a lot in aftermarket exhaust bolt-on parts and NOT to get tune, getting just part of possible gains from upgrades, so that "gain" is of less importance.

From catless frontpipes these seemed interesting to me:
Fujitsubo one with dual resonators. LOL, it even makes impression like having cat, has extra port for sensors, and resonators may help with enhancing sound/dealing with drone.
Or Nameless one with integrated overpipe.
But if i'd be willing to do anything to any of stock cats, my primary choice would be catless header + stock frontpipe.

From headers i'd consider these:
Ace Type A/350 (CS400 if RHD country/car) with DT tune for supposedly best gains
OFT+OFH for nice package
Groupe-S for budget catless header
JDL or Tomei for a bit more expensive ones
For track-only car Ace anaconda or /150/250 or PTuning

Catted header, JDL or FT86SF

What do you think about the HKS Catted header? Have you heard anything on this brand? any performance data?

[guybo]

As for gutting the cats- don't listen to the guessers on this forum. A lot of people don't like gutting because it's cheaper than their expensive header and is just as good. Read this:

http://www.circuitmotorsports-blog.c...-fr-s-86s.html

These are professionals who don't guess and have dyno results. they aren't trying to sell anything either. Just save yourself a lot of money and gut and tune.

An aftermarket header does look better, true. when you pop the hood it looks pretty down there. But the gutted stock header with the heat shields still in place is better for the engine and reduces heat soak.

If you are going to leave the cats, do yourself a favor and stay stock, it's not worth it. I had my cats and a OFT stage 1 tune for a while and the difference was not worth the money spent. The good thing about OFT is that it cost me nothing extra when I went stage 2. Yeah some of the torque dip with stage 1 was better but eh not much. Once I gutted and went stage 2 OFT the difference was night and day.

The stock tri-Y header is an excellent design and the empty chamber left behind in the collector by the cat being gutted doesn't affect the tune at all.

....and cue the butt dyno claims.....