[michaelalex17]

Originally Posted by Mflowt5

Yes, don't do it. I was pulled over by cops because they thought it was too loud. Luckily they didn't look under the car but it draws unnecessary attention to yourself. In addition, it doesn't sound very clean, rather mangly and throaty, which I don't prefer. Also, mufflers are decently important as you want some back pressure in the system. You will loose HP from a muffler delete (not much). It is smarter to delete your cats and have high flow mufflers so some back pressure is sustained and you won't draw a lot of attention (unless you have eisenmann race). Just my opinion and do what you want with it. Good luck.

u said cops will pull u over for it. its illegal? i know for state inspections they just plug the computer into the OBII or whatever its called.

[turb0mik3]

Originally Posted by gbreeE90

lol wrong. You dont need back pressure.

Yes you actually do. A turbo works by restricting the exhaust (backpressure) so that the exhaust gasses turn the turbine and exit the turbo. Without backpressure you would have no boost. Furthermore, think of it in terms of a guard at a gate. The Exhaust wants to get past the guard but only after the exhaust pushes breifly on each of the turbine blades. Once the exhaust pushes on the blades it's free to exit via the tail pipe. So in essence you want as free flowing an exhaust as possible, but going with straight pipes or a muffler delete is not helping. There is a dyno around here that shows HP loss with a muffler delete.

Originally Posted by michaelalex17

u said cops will pull u over for it. its illegal? i know for state inspections they just plug the computer into the OBII or whatever its called.

It is illegal in CA to have no mufflers. I am sure it is elsewhere too. State inspection will check to see if you have a muffler because it will be extremely loud. It is the easiest way to check: just look under the rear end. I had a muffler delete for a while and it was alright. Just sounded unprecise and too muffled. Just my opinion but I would just save money and get an axle back exhaust and worry about midpipes later.

[michaelalex17]

im pretty sure a lambo would be louder then my 335i with no muffler so i dont get that logic.

[Forcefed3]

Originally Posted by Mflowt5

Yes you actually do. A turbo works by restricting the exhaust (backpressure) so that the exhaust gasses turn the turbine and exit the turbo. Without backpressure you would have no boost. Furthermore, think of it in terms of a guard at a gate. The Exhaust wants to get past the guard but only after the exhaust pushes breifly on each of the turbine blades. Once the exhaust pushes on the blades it's free to exit via the tail pipe. So in essence you want as free flowing an exhaust as possible, but going with straight pipes or a muffler delete is not helping. There is a dyno around here that shows HP loss with a muffler delete.

You are very confused. A turbo does not need back pressure at all. A turbo works by using the exhaust gasses to spin the turbine wheel which is connected to and turns the compressor wheel which forces the incoming charge into the cylinders. Exhaust gasses are going to exit the cylinders no matter what so as long as the wastegates are closed the turbine wheel is going to spin, creating boost. What the car needs is exhaust VELOCITY. Many people are very confused about this, including yourself. The car didnt loose power because of lack of back pressure, it lost power because of less exhaust velocity. The perfect exhaust would be one that is small enough to have a high exhaust velocity but no mufflers, cats, etc. You should read this, it will help you out.

http://www.hondacivicforum.com/forum...ts-wrong-3064/

[michaelalex17]

thanks guys, i am not confused about the backpressure i know the less backpressure on a turbo car the better. i just didnt know if i should do the muff delete or not. i want a loud start up and loud idle and loud when giving it gas but then not as loud when cruising on the highway. i dont think deleting the 2nd cats or whatever is loud enough in terms of startup and idle for me based on youtube videos. so i just dont know how bad the muffler delete will be on the highway. if u have music on can u hear the drone over it or no?

[ProbyOne]

Originally Posted by Mflowt5

Yes you actually do. A turbo works by restricting the exhaust (backpressure) so that the exhaust gasses turn the turbine and exit the turbo. Without backpressure you would have no boost. Furthermore, think of it in terms of a guard at a gate. The Exhaust wants to get past the guard but only after the exhaust pushes breifly on each of the turbine blades. Once the exhaust pushes on the blades it's free to exit via the tail pipe. So in essence you want as free flowing an exhaust as possible, but going with straight pipes or a muffler delete is not helping. There is a dyno around here that shows HP loss with a muffler delete.

Sure you could consider the dP from the turbine wheel "backpressure" but everyone here is talking about "backpressure" after leaving the turbos.

Backpressure is never good. Exhaust momentum is good (see above post on velocity).

ETA: I think that you are confusing the topics of 1) recovering energy from exhaust gasses with 2)friction losses in the exhaust system

[ProbyOne]

Originally Posted by ttbmer

Really I didn't know that turbo engine need back pressure I thought that was only for NA cars

And so everyone is clear, friction losses due to the exhaust system is NEVER a good thing, regardless of application (NA vs. FI).

[turb0mik3]

Hm, fair enough. I always thought a little was needed but thank you for the clarification. I do have one of the most free flowing exhaust systems out there so I never doubted a less restrictive was the best. Thanks for the knowledge.

[Forcefed3]

Originally Posted by Mflowt5

Hm, fair enough. I always thought a little was needed but thank you for the clarification. I do have one of the most free flowing exhaust systems out there so I never doubted a less restrictive was the best. Thanks for the knowledge.

Yep, as long as you dont have huge exhaust pipes you're good.

[Never-Enough]

Originally Posted by Mflowt5

Yes you actually do. A turbo works by restricting the exhaust (backpressure) so that the exhaust gasses turn the turbine and exit the turbo. Without backpressure you would have no boost. Furthermore, think of it in terms of a guard at a gate. The Exhaust wants to get past the guard but only after the exhaust pushes breifly on each of the turbine blades. Once the exhaust pushes on the blades it's free to exit via the tail pipe. So in essence you want as free flowing an exhaust as possible, but going with straight pipes or a muffler delete is not helping. There is a dyno around here that shows HP loss with a muffler delete.




It is illegal in CA to have no mufflers. I am sure it is elsewhere too. State inspection will check to see if you have a muffler because it will be extremely loud. It is the easiest way to check: just look under the rear end. I had a muffler delete for a while and it was alright. Just sounded unprecise and too muffled. Just my opinion but I would just save money and get an axle back exhaust and worry about midpipes later.

Must be 335 specific then b/c I had 3" DP back exhaust w/no muffs & deleted cat on my old MAZDASPEED6 & that really woke the car up....

Turbo cars love free flowing exhaust.

[michaelalex17]

i have a question then, so the 335i is quite on startup and idle and then when u remove the muffler is becomes loud, but u get a drone at highway speed. but what about a car like a Lamborghini or something that i believe has a muffler but is very loud on startup and idle? do they have the drone also?

[ttbmer]

Originally Posted by ProbyOne

And so everyone is clear, friction losses due to the exhaust system is NEVER a good thing, regardless of application (NA vs. FI).

Cool' good to know!! Learn sone new everyday!
Thank you

[michaelalex17]

i have a question then, so the 335i is quite on startup and idle and then when u remove the muffler is becomes loud, but u get a drone at highway speed. but what about a car like a Lamborghini or something that i believe has a muffler but is very loud on startup and idle? do they have the drone also?

[GAINZ]

I did my muffler delete back in January.

It sounds really good a lot of the time, but the drone can get annoying when you have passengers in the car. I don't mind it when I'm driving by myself, but sometimes after a while the drone will get on your nerves after long driving.

I love it because it loud when you want it to be loud. The start-up and cold-starts sound really good, also idle is pretty loud and you can hear it from a descent distance away. It sounds really good under heavy throttle and when you're in tunnels, near walls, and next to cars. I love it, but sometimes it annoys me.

I'm doing catless downpipes soon so after I install them I might have to put them back on depending on how loud the car is with muffler delete + catless downpipes.

Let me know if you have any other questions.

[ProbyOne]

Originally Posted by michaelalex17

i have a question then, so the 335i is quite on startup and idle and then when u remove the muffler is becomes loud, but u get a drone at highway speed. but what about a car like a Lamborghini or something that i believe has a muffler but is very loud on startup and idle? do they have the drone also?

Don't forget that the stock exhaust has a flap that opens and closes based off of RPM, so removing the stock exhaust also removes the exhaust flap (changing exhaust note/loudness).

Ferrari also does something similar to this.

[michaelalex17]

i have the golf tee mod so that doesnt really apply to me, and i dont think that really answered my q but thanks for the info

[michaelalex17]

anyone?

[Forcefed3]

Originally Posted by michaelalex17

i have the golf tee mod so that doesnt really apply to me, and i dont think that really answered my q but thanks for the info

No, that was an answer to your question. The flap is closed in those exotic cars you speak of while cruising so it reduces drone.

[michaelalex17]

ohhhhh ok i get what he meant now thanks. i thought he was saying that if i remove the muffler it removes the flap so i should be aware of that also. i didnt understand what he meant. so all exotic cars that are loud have those types of flaps? like a lambo? or a Dodge Viper or one of those types of cars that are meant to get everyones attention.

[Forcefed3]

Originally Posted by michaelalex17

ohhhhh ok i get what he meant now thanks. i thought he was saying that if i remove the muffler it removes the flap so i should be aware of that also. i didnt understand what he meant. so all exotic cars that are loud have those types of flaps? like a lambo? or a Dodge Viper or one of those types of cars that are meant to get everyones attention.

Not every single one of them. But the ones that are well engineered will. The flap actually can help with power in some cars, it increases exhaust velocity.

[STONEY_M5]

i would like to hear cl dp and secondary cats deleted with muffler delete on an e90

[Cozmos]

Regarding your question about what manual or auto has to do with a muffler delete. If your auto, your always going to be at very low RPM resulting in a drastically different sound while city driving ( in a verrry bad way) and also massive freeway drone. It will probably sound terrible with auto.

And a lot of people with exotic cars (Ferrari's etc) do a similar golf tee mod as most of the members on here to keep from buying ungodly costing exhaust systems, and some even straight pipes, but exotic v8 and v10 drone sounds a lot different than turbo I6 drone and they generally don't have to deal with these cars on a daily basis.