LT1 vs LT4 catalytic converter differences?

cjperformance · 06-14-2022, 01:34 PM

Anyone know what the differences are in the catalytic converters for LT1 vs LT4? They are different GM part numbers, but they don't hardly give any data online.

I'm really trying to figure out some legal routes to better exhaust. I don't really want to run long tubes (inspections), and the cat converter restriction is (from what I understand) mainly around necked down connection pipe... not the grid itself. At least not as much... I thought about some GESI converters as they are supposedly legal... maybe???, and guarantee no CEL, but would need to find or fabricate my own connection pipes between them and the stock headers/manifold.

I don't have a ton of data on wither the GESI converters improve anything either.

Kooks Green Cats are supposedly EPA compliant too, but dont guarantee that CEL wont light.

I don't want to disable cat codes either. Looking for 100% legal options.

SJFGTO · 06-14-2022, 05:32 PM

I do not know the difference, if any. However, any gain from switching cats to improve exhaust flow, without LTs, is sure to be negligible and a poor benefit per dollar modification. Eliminating cats typically nets 6-8 HP at most, so switching between cats is not likely to get you even that. Also, today’s cats flow quite well for stock and moderately modded engines. I’d put my hard earned $$$ elsewhere.

6spdhyperblue · 06-14-2022, 06:02 PM

Quote:

Originally Posted by SJFGTO

I do not know the difference, if any. However, any gain from switching cats to improve exhaust flow, without LTs, is sure to be negligible and a poor benefit per dollar modification. Eliminating cats typically nets 6-8 HP at most, so switching between cats is not likely to get you even that. Also, today’s cats flow quite well for stock and moderately modded engines. I’d put my hard earned $$$ elsewhere.

Is that loss for one cat or for both?

SJFGTO · 06-15-2022, 06:07 AM

Both. LOL! I have personally seen at least a half a dozen before and after dyno runs before/after cat removal. Never saw a gain more than 8, saw a couple of 2 or 3 HP gains. Converter switching for exhaust flow or sound on an otherwise stock or mildly modded car is a very poor investment.

6spdhyperblue · 06-15-2022, 07:11 AM

Ok sounds good. For clarity, I meant primary and secondary. Not one bank

LT1ornothing · 06-15-2022, 08:11 AM

Quote:

Originally Posted by SJFGTO

Both. LOL! I have personally seen at least a half a dozen before and after dyno runs before/after cat removal. Never saw a gain more than 8, saw a couple of 2 or 3 HP gains. Converter switching for exhaust flow or sound on an otherwise stock or mildly modded car is a very poor investment.

Were those all naturally aspirated bolt on cars? From my understanding, the power gains on cat removals are much higher than what you indicated in forced induction applications.

cjperformance · 06-15-2022, 10:16 AM

In addition to any possible performance increases, I have been told several times that forced induction will eventually destroy the stock LT1 cats... which is why I was wondering if the LT4 cats are any different... either in flow characteristics, or in construction.

So at some point I'll have to replace them anyway... May as well be prepared with a good replacement strategy.

KingLT1 · 06-15-2022, 11:37 AM

Just get headers and GESI Gen 2 cats. They are handling 1000hp + and not failing.

cjperformance · 06-15-2022, 01:20 PM

Quote:

Originally Posted by KingLT1

Just get headers and GESI Gen 2 cats. They are handling 1000hp + and not failing.

Thank you for the input. This is the route I am leaning towards. I will probably hold out if/until my stock cats get trashed due to cost investment.

Joshinator99 · 06-15-2022, 06:23 PM

Quote:

Originally Posted by cjperformance

I have been told several times that forced induction will eventually destroy the stock LT1 cats...

While this is true, the bigger problem is the restriction they cause will eventually give you soaring cat temps and an inefficient motor as you approach 650-700 WHP. The way the stock LT1 cats neck down where they meet the exhaust manifold is crazy small.

Quote:

Originally Posted by KingLT1

Just get headers and GESI Gen 2 cats. They are handling 1000hp + and not failing.

cjperformance · 06-15-2022, 06:53 PM

Right. Its prob less than 2 inch section... then i went and crammed an o2 sensor in there too.

cmitchell17 · 06-16-2022, 10:24 PM

I can't find anyone selling or in stock with the GESI cats anywhere, I know someone posted a link to a place I think that was selling them a while ago but I can't find it.

I have completely stock exhaust now minus the AFM valve delete (I deleted them in an attempt to stop the rattle and this was before the grind of the ear NPP rattle fix) and I want to put in GESI cats in the primary location and remove the secondary ones. I think the primary do the majority of the unburn hydrocarbon cleanup so they do most for the bad smells and I think the secondaries are more for Nox.

The thing I am trying to figure out is how I want to do it. The secondary cats have an offset input/output, which is going to make it look weird and akward with a relatively tight s bend pipe in their place, I think I might just try to take out most of the section up until the bend.

06-14-2022, 01:34 PM	#1
cjperformance Drives: 2017 Camaro SS 50th Anniversary Join Date: Apr 2021 Location: Missouri Posts: 928	LT1 vs LT4 catalytic converter differences? Anyone know what the differences are in the catalytic converters for LT1 vs LT4? They are different GM part numbers, but they don't hardly give any data online. I'm really trying to figure out some legal routes to better exhaust. I don't really want to run long tubes (inspections), and the cat converter restriction is (from what I understand) mainly around necked down connection pipe... not the grid itself. At least not as much... I thought about some GESI converters as they are supposedly legal... maybe???, and guarantee no CEL, but would need to find or fabricate my own connection pipes between them and the stock headers/manifold. I don't have a ton of data on wither the GESI converters improve anything either. Kooks Green Cats are supposedly EPA compliant too, but dont guarantee that CEL wont light. I don't want to disable cat codes either. Looking for 100% legal options. __________________ 2017 50th Anniversary Edition \| P1X Stage 2 DSX Aux Low Side \| LT4 high side \| Flex Fuel TooHighPsi Port Injection (installed & tuning) CircleD 3K Stall \| QA1 CF Driveshaft Forgestar F14 Drag 17x10 NT555R2 305/45/17 Rear Forgestar F14 18x8 NT555G2 235/50/18 Front 10.84@131 w/4.13" pulley ??.??@??? w/3.7" pulley (installed & tuning)

06-14-2022, 05:32 PM	#2
SJFGTO Oh Oh it's Friday Night! Drives: 2018 ZL1 1LE Nightfall Gray Join Date: Jan 2018 Location: Walton Woods Posts: 1,061	I do not know the difference, if any. However, any gain from switching cats to improve exhaust flow, without LTs, is sure to be negligible and a poor benefit per dollar modification. Eliminating cats typically nets 6-8 HP at most, so switching between cats is not likely to get you even that. Also, today’s cats flow quite well for stock and moderately modded engines. I’d put my hard earned $$$ elsewhere. __________________ 2018 Camaro ZL1 1LE NFG; ARH 2” headers, catless mids, ARH full exhaust, Lingenfelter 18% lower pulley, ATI Harmonic Balancer, Roto-fab CAI, EE-catch can, TM ported TB, NX Lid, BMR strut tower brace. Aeroforce dual pod interceptor gauges. Tuned by Vengeance Racing!!! 644 HP @ 6250 rpm / 689 trq @ 3660 rpm Four that wanna own me Two that wanna stone me One says she's a friend of mine...

06-15-2022, 06:07 AM	#4
SJFGTO Oh Oh it's Friday Night! Drives: 2018 ZL1 1LE Nightfall Gray Join Date: Jan 2018 Location: Walton Woods Posts: 1,061	Both. LOL! I have personally seen at least a half a dozen before and after dyno runs before/after cat removal. Never saw a gain more than 8, saw a couple of 2 or 3 HP gains. Converter switching for exhaust flow or sound on an otherwise stock or mildly modded car is a very poor investment. __________________ 2018 Camaro ZL1 1LE NFG; ARH 2” headers, catless mids, ARH full exhaust, Lingenfelter 18% lower pulley, ATI Harmonic Balancer, Roto-fab CAI, EE-catch can, TM ported TB, NX Lid, BMR strut tower brace. Aeroforce dual pod interceptor gauges. Tuned by Vengeance Racing!!! 644 HP @ 6250 rpm / 689 trq @ 3660 rpm Four that wanna own me Two that wanna stone me One says she's a friend of mine...

06-15-2022, 07:11 AM	#5
6spdhyperblue Drives: 6th gen Join Date: Aug 2013 Location: US Posts: 3,669	Ok sounds good. For clarity, I meant primary and secondary. Not one bank __________________ ‘22 2SS 1LE M6 Summit White - RF, Flexfuel, LT2 intake, 95mm tb, ATI udp, VT ramair, full 28” dragpack - 11.68@122 ‘16 1SS M6 LT2 intake + boltons on DR 11.0@126+ (Sold)

06-15-2022, 10:16 AM	#7
cjperformance Drives: 2017 Camaro SS 50th Anniversary Join Date: Apr 2021 Location: Missouri Posts: 928	In addition to any possible performance increases, I have been told several times that forced induction will eventually destroy the stock LT1 cats... which is why I was wondering if the LT4 cats are any different... either in flow characteristics, or in construction. So at some point I'll have to replace them anyway... May as well be prepared with a good replacement strategy. __________________ 2017 50th Anniversary Edition \| P1X Stage 2 DSX Aux Low Side \| LT4 high side \| Flex Fuel TooHighPsi Port Injection (installed & tuning) CircleD 3K Stall \| QA1 CF Driveshaft Forgestar F14 Drag 17x10 NT555R2 305/45/17 Rear Forgestar F14 18x8 NT555G2 235/50/18 Front 10.84@131 w/4.13" pulley ??.??@??? w/3.7" pulley (installed & tuning)

06-15-2022, 11:37 AM	#8
KingLT1 Drives: 2016 1SS NFG A8 Join Date: Aug 2017 Location: 46804 Posts: 6,787	Just get headers and GESI Gen 2 cats. They are handling 1000hp + and not failing. __________________ 2016 NFG 1SS A8 Options-2SS Leather/NPP Perf. mods-Whipple 2.9/Fuel System/Flex Fuel/103mm TB/Rotofab Big Gulp/Cat Deletes/Corsa NPP Per. times- 10.5 @ 137 w/ 1.8 60ft Full weight on 20's 1200DA

06-15-2022, 06:53 PM	#11
cjperformance Drives: 2017 Camaro SS 50th Anniversary Join Date: Apr 2021 Location: Missouri Posts: 928	Right. Its prob less than 2 inch section... then i went and crammed an o2 sensor in there too. __________________ 2017 50th Anniversary Edition \| P1X Stage 2 DSX Aux Low Side \| LT4 high side \| Flex Fuel TooHighPsi Port Injection (installed & tuning) CircleD 3K Stall \| QA1 CF Driveshaft Forgestar F14 Drag 17x10 NT555R2 305/45/17 Rear Forgestar F14 18x8 NT555G2 235/50/18 Front 10.84@131 w/4.13" pulley ??.??@??? w/3.7" pulley (installed & tuning)

06-16-2022, 10:24 PM	#12
cmitchell17 Drives: 17 2SS, 8L90, Cam, Heads, E85 Join Date: Dec 2016 Location: US Posts: 1,200	I can't find anyone selling or in stock with the GESI cats anywhere, I know someone posted a link to a place I think that was selling them a while ago but I can't find it. I have completely stock exhaust now minus the AFM valve delete (I deleted them in an attempt to stop the rattle and this was before the grind of the ear NPP rattle fix) and I want to put in GESI cats in the primary location and remove the secondary ones. I think the primary do the majority of the unburn hydrocarbon cleanup so they do most for the bad smells and I think the secondaries are more for Nox. The thing I am trying to figure out is how I want to do it. The secondary cats have an offset input/output, which is going to make it look weird and akward with a relatively tight s bend pipe in their place, I think I might just try to take out most of the section up until the bend.

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