Hey everyone. I have a 2020 C63s - and I decided, for some more noise, to get some catted downpipes from Modal.

Wanting to get everyone's thoughts on this. Are there any major drawbacks or risks of getting new downpipes ? Are aftermarket ones at all bad for your car in anyway? I do not know a great deal about them, so trying to learn as much as I can right now.

Thanks!

Here are few that I can think of.
It is quite expensive to properly install aftermarket downpipe because installer has to drop the transmission to get stock downpipe out without cutting.
Installation should be around $1300 but could be more or less depending on the area.
You can install it without dropping transmission by cutting stock downpipe and save about $500 but it will be hard to put stock one back to car.

Most Benz dealers I heard is not friendly with aftermarket downpipe. Your dealer could potentially void your car’s entire powertrain warranty by noting it in their system.
Just expect the worst if something happens to your car.

You will get check engine light with modal downpipe. You will either need to get tune or get some kind of O2 spacer to trick the sensor.

Are downpipes worth it? Thinking of getting the modal 200 cat downpipe system, with spacers to eliminate the CEL. In everyones opinion, is it worth it for the hassle they cause?

As has been advised to me in the past, and based on personal experience with other cars, you should be aware of the following...
- find a dealership friendly to modifications such as you are suggesting. Namely, aftermarket downpipe, different cat, tricking a sensor, and tuning the ECU.
- If you can't find such a dealership, have a friendly shop that is willing to bring your car back to stock for reasonable $$, prior to bringing it into the dealership for anything.
- ANYTIME you modify the ECU, it is recorded. On the off chance that you ever have a serious need for warranty work on the engine, IN ANY WAY, or anything that could conceivably be related to the engine and/or other expensive parts/labor... ECU, sensors, throttle bodies, suspension, turbos, etc, you should assume you may still have ZERO warranty protection and you will be flagged for mods. Vehicle parent companies will look for almost any reason to avoid paying warranty coverage.
- Most reasonable dealerships will overlook minor modifications, IF you're going in for unrelated issues, and IF the issues are of lesser cost. Recommend you to check with service tech/service manager of your preferred dealership prior to making any mods. They may be more understanding if you tell them ahead of time what you plan to do, and if you treat them right.

Also, you can consider getting products from companies that put in writing that they will provide equal to factory warranty coverage for products you get from them, should MB not warranty cover a problem. For example, Dinan (as you may or may not be aware) covers expensive BMW mods (ECU tunes, Stage 1, 2, 3 etc package upgrades, throttle bodies, turbos... whatever) with equal factory warranty coverage when they perform such work on a car.

Whatever you decide, just ask yourself the following question: "is a louder sound, bigger horsepower, a fatter torque curve, a lowered ride, or whatever you want to get out of your car, worth potentially fully voiding the vehicle warranty?"

It's already a powerful, beautiful car with a biturbo V8 engine. It will be expensive when things need to be repaired/replaced. Warranty coverage on an unmodified car is peace of mind.

If you actually purchase the car and plan to keep it long-term, warranty coverage, extended or otherwise, will eventually run out and then you can modify to your heart's content, since you'll be paying out-of-pocket to maintain it anyway, whether it's modified or not.

So IMO, if you plan to change downpipes then just go for it. Aftermarket cats are not legal so if you are going to void the legality just go all the way and get a tune as well. You wont be sorry. With stock mufflers and catless downpipes its not loud but way better than stock - Take that to the bank

Not true (in US).

There are 4 (NY, CO, CA, ME - no surprises) out of 50 states that require aftermarket cats meet CARB certification, but they are still legal. Everywhere else that still only cares you have cats of some kind and can pass emissions.

Paying to play: can't tell you how many thread I've seen here where the OP is ^%$# out of luck due to mods.

He is talking the intent of the law. I am speaking the Letter of the law. So Factually I am correct.. LessisMore - Respectfully its not as easy as just saying as long as a cat is there its legal. - Not True to coin your words. The law actually states the factory must warrant your cats for 10 years or 100,000 miles. What that means is if your car is under 10 years old or under 100k miles, then only the stock cats are legal replacements. All the cats sales people and manufactures in the world can try to tell you you otherwise - its just not fact. If all you care about is passing a sniffer test and not getting pinched - there are a few ways to get around it...like you are eluding to. That does not make it legal. Selling a catted down pipe - that is the subject matter. My vote is still take them out and make the max power. Or run an aftermarket high-flow cat (that really does not flow more than stock) and sleep at night based on your purchase. Its still not legal by the letter of the law

This is flat out wrong, and is the assumption that forms the basis of your misunderstanding.

Its not a fight - Its just the facts Don't shoot the messenger I helped write and form the standards for the EPA and CARB, independent of each other. Again letter of the law vs Intent. The guy just wants to know how we feel about changing parts. So again to answer the question - We took ours off and put straight downpipes using stock mufflers and the stock valves in the exh system. It sounds great.

BTW - I did the same thing to our E63. It seemed louder - still using the stock mufflers

Side note - Everyone may claim to be an expert. I do not claim to be an expert on anything. However...Joe knows EPA and CARB. And I am Joe. I have worked hand in hand with both of them dating back to 1988. I have done EPA and CARB testing for Paxton, Vortech, Diablosport, Comp Cams, Trick Flow, Doug Thorley, Z Industries, Edelbrock, and more.

Joe, I don't know where the idea that this is a fight came from. Still just a discussion and exchange of information to me. I know I can be direct sometimes, but just want to get to the truth here.

I'm not clear on the reason you keep bringing up letter of the law vs intent of the law. Are you saying that the law is written in a way that is not consistent with the intent? Or that the law is commonly implemented in a way that is not consistent with how it is actually written?

​​​​​I do not claim to be an expert on CARB certification, primarily because those overreaching regulations do not apply to me.

Are you also equally familiar with the non-CARB EPA regs that cover the vast majority of state emissions laws in the United States?

Back to CARB: With your familiarity and long experience, can you please point to a link with the specific verbiage in the CARB regulations where it clearly states that if a vehicle is less than 10 years old and has less than a 100K miles, it is illegal to use equivalent aftermarket parts or anything except an OEM manufacturer provided cat, that would refute my statement? I have no problem eating my hat and acknowledging if I am wrong.

Based on your statements, Walker exhaust, one of the largest companies im the game (that you have consulted with) is violating EPA and CARB regs with this page and products they sell?

https://www.walkerexhaust.com/support/tech-tips/state-catalytic-converter-guide.html

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So the letter of the law implies as written and the intent means “one” tried to meet the standard. Like running a hi flow cat. If “one” takes out the stock cat only to install a higher flow version, they are trying to meet the intent although not meeting the “as written standard”.



YES




Nice Video. It does not address the 10 year/100,000 mile reg. Walker does offer “equivalent” replacement parts. AGREED. Equivalent in this case DOES NOT INCLUDE “Hi Flow” or different CELL construction cats.

I will find the verbiage and report back.

My question to you

If the law requires the manufactures to replace your emissions components for 10 years or 100,000 miles, then why would “one” want to pay for that? Its free from the manufacturer. But yes if you have a car with less than 10 years and 100,000 miles and want to buy a Walker cat replacement that does just that, replace with an equivalent part…more power to ya. If you removed said parts and then later decided to sell your car and needed replacement parts AND Walker had part that cost you less…then again I see it and yes it would be legal.

NO SUCH THING AS A LEGAL HIGH FLOW CAT – they meet the Intent but not the letter


And again I have no cats on my E, C or S.

i met a cat once , i think its name was speedbump…

Ah I see - First it was:

Now:

I see what happened and I think we are done.

I appreciate the clarifying response, which i agree is now accurate.