performance advantage to going catless at section 1 (full supersprint setup)?

[gixxer]

Hello,

Currently the car has 63.5mm (2.5 inch) full Supersprint setup with catless header, catted section 1, twin-pipe (non-resonated) and race exhaust.

Thinking of going catless in section 1.

The car is supercharged with AA setup.

I hear lot of talk from Turbo folks with downpipe where catless makes sense if can bare the smell (and sound).

But for NA and supercharged cars, does going catless in section 1 add any anything to the performance?

Or, just waste of money for the smell?


Thanks.

[usdmej]

Hello,

Currently the car has 63.5mm (2.5 inch) full Supersprint setup with catless header, catted section 1, twin-pipe (non-resonated) and race exhaust.

Thinking of going catless in section 1.

The car is supercharged with AA setup.

I hear lot of talk from Turbo folks with downpipe where catless makes sense if can bare the smell (and sound).

But for NA and supercharged cars, does going catless in section 1 add any anything to the performance?

Or, just waste of money for the smell?


Thanks.

at best, single digit hp gains compared to a quality catalytic converter (like you'd get on a SS setup)


smell is pretty awful, and then there's the environmental impact too

[Cronenberged]

The SS chatted sec 1 isn't that restrictive. The hjs fill is a gold standard for performance cats AFAIK.

[Icecream]

You'll probably beat most lambos tbh, or it will be totally like closer without cats.

[Tbonem3]

I always feel a difference going between catted and catless, but when I got the HJS catted sect 1 to replace the 2.5" v1 stepped decat pipes (in order to pass CA smog) I felt no change! The only change I noticed was a little less drone and rasp overall. Not even that much quieter. The HJS are the real deal.

[Epoustouflant]

I always feel a difference going between catted and catless, but when I got the HJS catted sect 1 to replace the 2.5" v1 stepped decat pipes (in order to pass CA smog) I felt no change! The only change I noticed was a little less drone and rasp overall. Not even that much quieter. The HJS are the real deal.

Very true. Supersprint bench tested HJS v catless and there's nothing in it (outside of smelly NOx and CO2 emissions). Price is a factor, can't deny it.

[ridebikes]

Another vote for HJS. I went with Fabspeed's setup and it's awesome so far.

I also think the smell would just ruin every drive. I never want to have to explain why something is weird on my car to a passenger.

[gixxer]

Thanks all.

My Supersprint 63.5mm setup is from 2007 (not a typo, it's that old). Current mileage is at around 24,000 miles.

I imagine my stepped header is V1, whatever that means.

Maybe HJS race cats have improved since 2007 (???), but from what i hear, i would be better off just sticking with the race cats in section 1.

[Tbonem3]

You're good to go man.

[usdmej]

I never want to have to explain why something is weird on my car to a passenger.

the best litmus test frankly. if you sound like a fool justifying a mod to an automotive layman, that part probably doesn't belong on a street car

[jet_dogg]

I also think the smell would just ruin every drive. I never want to have to explain why something is weird on my car to a passenger.

The best part about having a modded car.

[stash1]

Ya, as everyone has mentioned, a high quality HFC will flow nearly as well as non-catted pipes. It's hard to believe that all that 'crap' in the pipe doesn't cause much of a restriction, but w/our relatively (by comparison) low HP engines, they just don't present much of a restriction. I've done back-to-back testing and the difference is usually less than 7 HP. Maybe some of the lower quality/high cell count CAT's may be more of an issue, or if we were dealing w/500+ HP engines...the outcome might be different.

[gixxer]

Ya, as everyone has mentioned, a high quality HFC will flow nearly as well as non-catted pipes. It's hard to believe that all that 'crap' in the pipe doesn't cause much of a restriction, but w/our relatively (by comparison) low HP engines, they just don't present much of a restriction. I've done back-to-back testing and the difference is usually less than 7 HP. Maybe some of the lower quality/high cell count CAT's may be more of an issue, or if we were dealing w/500+ HP engines...the outcome might be different.

Okay, 500+ HP, not in that plus territory...

[bmw m3 s50]

I feel that catalytic converters have come a long way since the e46 m3 was released. I remember when the e46 m3 came out that most cats would rob a ton of power from the car, so it was a no brainer to go catless. Now there are companies like HJS, GESI, even certain OEM cats that are high quality catalytic converters that can handle high HP and better engine tuning. These high quality catalytic converters only rob single digit whp which has been proven through dynos results (research online, many articles on this). Also I would not deal with exhaust smells, it sucks getting out of the car and your clothes smell from the fumes.

The problem will not be power loss but longevity. The higher quality catalytic converters tend to hold up longer and handle more abuse. Your problem will be that you are supercharged and running a catalytic converter designed for an NA m3 with different exhaust flow and temperatures. Will it hold up, I can not answer that. As an example, when running my AA supercharged m3, I did not run cats. I did run a resonated section 1 and that eventually did not hold up over time. I can not image that a catted section 1 would have held up better. If you have made it 24,000 miles then that is a good sign.

Additionally, RMS makes an exhaust header designed for supercharged e46 M3's which makes the exhaust flow even better than the Supersprint stepped headers. There are no dynos to show the difference but the tubing and primaries on the RMS headers are the largest of any e46 m3 header which would help with the much greater increase of exhaust flow that the supercharger produces. These are all options for you.

[gixxer]

Recently i got "owned" by G82 M4 (i think was non-Comp variant) on the Mexico highway doing pulls. Toward the end i was catching up with the HP and i think may have even gone out in front, but man took a while...

Damn my linear curve with the supercharger for HP and dinky little torque

Just looking at places i can squeeze bit more performance without gong engine rebuild and turbo.

Local shop has e46 turbo setup with catless. Going to check that out, just how bad the smell is.

I know with my current setup with the Supersprint race cats, pull in to the garage and close the garage door, and smell is there.

Get out of the car outside though, can't really notice in outdoor.

Additionally, RMS makes an exhaust header designed for supercharged e46 M3's which makes the exhaust flow even better than the Supersprint stepped headers. There are no dynos to show the difference but the tubing and primaries on the RMS headers are the largest of any e46 m3 header which would help with the much greater increase of exhaust flow that the supercharger produces. These are all options for you.

Darn, 63.5mm of Supersprint versus 75mm ?

I would still be limited at my 64mm piping with Supersprint. though in section 1 and 2, through the Race Muffler.