Cats. & removal ?

[Captain Greg]

Guys my car is out of warranty I had an H pipe with standard rear boxes, the drone inside at normal speeds was too much…removed the H pipe, then I added aftermarket rear boxes car sounds nice not to loud definitely masculine …I’m considering removing the cats, will it be very noisy will it have more power ? Are there any advantages to this ?

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[Cobra Jet]

On a modern day performance car that is not used in any track or time trial events and the engine is not sustained at long (or very short/quick) intervals at very high speed/rpm - there is absolutely NO benefit to removing the catalytic converters.

Modern day catalytic converters (last 10 years) are very high flow and are not as restrictive as older systems of the past. Think about the performance cars out on the market now pushing 400-500-600HP right out of the box that were designed and built with catalytic converters in place.

You also cannot just remove the cats on an S550. Well... let's rephrase that - anyone can physically remove their cats...but error codes will surface AND even if bypassing the errors via known tricks, the car won't be running efficiently as designed (fact).

Operationally, you may need an aftermarket tune or a way to bypass the O2's, otherwise the engine will not perform at its optimum as designed and again multiple error codes may pop up.

---

Removing cats and or the resonator will greatly increase the sound (loudness) of the vehicle. Essentially you're removing inline "baffles" which are keeping the exhaust tone down. Once those baffles are removed, the car exhaust note will get much louder and you may notice increased drone as well at certain RPM ranges.

---

Does removing the cats improve exhaust flow? Yes BUT only to a degree as noted above regarding track use vs. daily driving. Adding LTH's and removing cats on a street driven vehicle where vehicle speed and RPM is not maintained, is erratic or sporadic stop/go intervals due to traffic, signal signs, signal lights, and lower speed limits in populated areas - it has NO benefit at all - other than the "loud factor".

If the car is to be used 90% or more for track use (drag racing, road racing or auto-X) and where rpm/speed is maintained higher than "normal" (ie: grocery getting), then deletion of cats and running LTH's can be beneficial where performance gains are not only recorded BUT also recognized in data.

In any instance a tune would also usually accompany such changes for track cars
where every bit of HP and closing time gaps is a need for gains.

If the car is aftermarket forced induction via turbos or supercharger, a tune is mandatory and again, removal of cats will only be beneficial to how the car is being used. If it's just putzing around town @45 mph for a run to a store and back, there's just no benefit.

If you're in a State or region that requires emissions inspections - removal of cats is not only going to be a PIA come inspection time - but if caught running without, that can be a pricey monetary fine.

Removal of cats will in some instances also increase exhaust smell (raw fuel smell) and the excessive loudness can bring attention to you.

No one can tell you what to do - it's your vehicle. Just take note of the above, especially if you're in a region where annual emissions inspections are a requirement.

 

[Captain Greg]

On a modern day performance car that is not used in any track or time trial events and the engine is not sustained at long (or very short/quick) intervals at very high speed/rpm - there is absolutely NO benefit to removing the catalytic converters.

Modern day catalytic converters (last 10 years) are very high flow and are not as restrictive as older systems of the past. Think about the performance cars out on the market now pushing 400-500-600HP right out of the box that were designed and built with catalytic converters in place.

You also cannot just remove the cats on an S550. Well... let's rephrase that - anyone can physically remove their cats...but error codes will surface AND even if bypassing the errors via known tricks, the car won't be running efficiently as designed (fact).

Operationally, you may need an aftermarket tune or a way to bypass the O2's, otherwise the engine will not perform at its optimum as designed and again multiple error codes may pop up.

---

Removing cats and or the resonator will greatly increase the sound (loudness) of the vehicle. Essentially you're removing inline "baffles" which are keeping the exhaust tone down. Once those baffles are removed, the car exhaust note will get much louder and you may notice increased drone as well at certain RPM ranges.

---

Does removing the cats improve exhaust flow? Yes BUT only to a degree as noted above regarding track use vs. daily driving. Adding LTH's and removing cats on a street driven vehicle where vehicle speed and RPM is not maintained, is erratic or sporadic stop/go intervals due to traffic, signal signs, signal lights, and lower speed limits in populated areas - it has NO benefit at all - other than the "loud factor".

If the car is to be used 90% or more for track use (drag racing, road racing or auto-X) and where rpm/speed is maintained higher than "normal" (ie: grocery getting), then deletion of cats and running LTH's can be beneficial where performance gains are not only recorded BUT also recognized in data.

In any instance a tune would also usually accompany such changes for track cars
where every bit of HP and closing time gaps is a need for gains.

If the car is aftermarket forced induction via turbos or supercharger, a tune is mandatory and again, removal of cats will only be beneficial to how the car is being used. If it's just putzing around town @45 mph for a run to a store and back, there's just no benefit.

If you're in a State or region that requires emissions inspections - removal of cats is not only going to be a PIA come inspection time - but if caught running without, that can be a pricey monetary fine.

Removal of cats will in some instances also increase exhaust smell (raw fuel smell) and the excessive loudness can bring attention to you.

No one can tell you what to do - it's your vehicle. Just take note of the above, especially if you're in a region where annual emissions inspections are a requirement.

Thank you for a most comprehensive response and in depth information, based on this my cats can say as they are I’m not using the car for anything more than the odd little run to the store
I was told by some ( pub talk) removing cats will magically increase my RWHp …and I just thought for that small cost to get my car 435hp (claimed by Ford) to say the newer 460 Hp for little cost/ effort I would do it
Thank you for your in depth advice

Greg

 

[Orange5Fitty]

I have 2M cat deletes on my 2015 and it made it exponentially louder and the power difference was night and day with proper tune. Anyone that says removing them doesn't add power has absolutely no idea what they're talking about. My Hemi Ram is also FBO catless with tune and it does make a huge difference.

 

[Orange5Fitty]

I did swap my x pipe out to a Magnaflow 11386 X Muffler and it's amazing now.

 

[Captain Greg]

I have 2M cat deletes on my 2015 and it made it exponentially louder and the power difference was night and day with proper tune. Anyone that says removing them doesn't add power has absolutely no idea what they're talking about. My Hemi Ram is also FBO catless with tune and it does make a huge difference.

Thanks for this …do you have Dyno numbers to support it? I’m a big fan of super bikes and I use a corrected Dyno when we tune …I have found sometimes guys get confused with more aggressive sound than actual HP ….louder cars encourage one to drive more enthusiastically and this can fool one into thinking more power ?
Im not a great believer of just a tune …IMO & exp and engine is an air pump and one needs to get more air in and then get it out faster in order to gain power? normally doing this comes at a huge expense? there is no magic cheap bullet that just give one HP ? Or am I wrong ( I hope so cos the 550 out the box is by n means a beast)

 

[Orange5Fitty]

Thanks for this …do you have Dyno numbers to support it? I’m a big fan of super bikes and I use a corrected Dyno when we tune …I have found sometimes guys get confused with more aggressive sound than actual HP ….louder cars encourage one to drive more enthusiastically and this can fool one into thinking more power ?
Im not a great believer of just a tune …IMO & exp and engine is an air pump and one needs to get more air in and then get it out faster in order to gain power? normally doing this comes at a huge expense? there is no magic cheap bullet that just give one HP ? Or am I wrong ( I hope so cos the 550 out the box is by n means a beast)

It's just a canned custom tune for now, at some point I hope to get a custom dyno tune.

 

[engineermike]

Not exactly the same thing but I dynod my car, same dyno-same day, with and without cats. This was gt500 [2.75”] cats vs 3” straight pipes on a 730 rwhp pump gas combo. The car made 10-15 more hp with cats than without. There were some things going on in the calibration that caused an extra degree of timing with cats, but at the end of the day the least we can say is that they weren’t hurting it much.

 

[TexasMetallic5.0]

Mine will be going away before long. Nothing I’ve ever owned has kept them for any amount of time. I just need to decide on which mufflers I want, leaning towards AWE touring or LTH Scorpion.

 

[K4fxd]

If it's a gen 2 removing them should help as the gen 2 is 2 1/4 from the cat to the factory hookup.

 

[AZlb5.0]

removal of cats isn’t a wow factor. 10-15 hp that you really can’t feel to be honest. You might see it on your time slip again it’s a small gain. What you will notice is the noice. That to me is the biggest deferent now that I’ve gotten older and wiser. So it depends on the op and what he wants and can deal with.

 

[WildHorse]

there is absolutely NO benefit to removing the catalytic converters.

more mpg, 20 more hp, less weight, sounds great.

 

[Grimreaper]

Boosted is pretty noticeable SOTP. Running full 3 inch to gt500 mufflers. With cats its Camry quiet down low. Without, 4x as loud but all the right v8 noises. Much quieter than the mbrp race +cats previously. Muffler choice can make or break cat deletes tolerability.

 

[PC_GUARD]

Boosted is pretty noticeable SOTP. Running full 3 inch to gt500 mufflers. With cats its Camry quiet down low. Without, 4x as loud but all the right v8 noises. Much quieter than the mbrp race +cats previously. Muffler choice can make or break cat deletes tolerability.

Are you running a resonator or just straight through x/H?

 

[Grimreaper]

Are you running a resonator or just straight through x/H?

There's a pair of 16 or 18 inch 3 inch resonators in the h pipe that I had installed to try and tame the mbrp race few years back. Suspect they help with mid range rasp at most.

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