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BMW 3-Series (E90 E92) Forum > E90 / E92 / E93 3-series Powertrain and Drivetrain Discussions > N55 Turbo Engine Tuning and Exhaust Modifications - 335i Tuning > Is it worth it? best bang for buck? exhaust idea



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      11-20-2010, 07:08 PM   #45
Bakeme521
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When did I say something contradictory? When I agreed to what he said about drag cars? B/c what he said was a true statement. Stock cars need a bit of backpressure to run correctly, b/c that is how they are designed. I'm pretty sure we are on agreeing terms I just do not agree with how you went about saying it with no facts to prove what you are saying. We do not need comments like that and I am tired of seeing people bash others about a topic, its stupid and immature.
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      11-20-2010, 07:09 PM   #46
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Techno- whatever you say dude
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      11-21-2010, 09:42 AM   #47
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Quote:
Originally Posted by Bakeme521 View Post
When did I say something contradictory? When I agreed to what he said about drag cars? B/c what he said was a true statement. Stock cars need a bit of backpressure to run correctly, b/c that is how they are designed. I'm pretty sure we are on agreeing terms I just do not agree with how you went about saying it with no facts to prove what you are saying. We do not need comments like that and I am tired of seeing people bash others about a topic, its stupid and immature.
That was meant for BrainMN, but I was taking care of both responses in the one response I made, didn't come across that way.
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      11-21-2010, 09:45 AM   #48
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Originally Posted by gbreeE90 View Post
You do need a little bit of back pressure. But the main thing is, his exhaust sounds awesome, and its fully reversible


Ok, now we have you jumping in this discussion.

So then, explain the physics theory and how back pressure is needed and what the purpose it serves related to exhaust design?

My last post before this explains more, but I'm not doing physics research for you guys anymore. I posted enough of basic pressure theory and the well documented fact of 1HG of back pressure will reduce HP by 1HP.
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      11-21-2010, 09:56 AM   #49
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Techno- whatever you say dude
Haha...you just don't understand physics. You don't even know what a wastegate does.

Don't want to hijack the thread, but let's go over some basic 4-cycle engine theory.

At the point after air/fuel mixture is burnt, the piston then comes back up while the exhaust valve is open...known as the exhaust cycle.

So as the piston is rising, and it is now pushing air out the open exhaust valve.....here's the question...explain exactly how in terms of physics we want back pressure to push/work against the piston as this happens and why it is necessary?!?!?!

Of course we don't want any "back pressure" going against the piston and air as it is moving upward. That takes away power.

I just gave you the formula that 1HG of pressure is equal to 1HP.

So if you increase pressure by 1HG, you will lose 1HP...that is physics...nothing you can do or say about it as much as you want to come ans say I have no proof. That is your proof...

Why don't we have a 6" pipe for exhaust? Why stop there?? Because, as air expands, it slows!! Here again...physics. You need to test and design the optimum size of the exhaust to: 1) Reduce backpressurer; and 2) Increase velocity. Accomplishing this across the entire RPM range is the challenge due to those changing as engine RPM increased.

I'm not doing your physics research for you...I know the facts on pressure, exhaust design and velocity.

Just keep responding with "whatever you say" and continue on in your world.
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      11-21-2010, 09:58 AM   #50
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Ok, everyone stop posting. Techlogik is the smartest man alive.
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      11-21-2010, 10:56 AM   #51
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Techlogik- read my post last page. Typical non-performance and non-sophisticated engines need backpressure to run PROPERLY - the reason is NOT for more power or torque. Why do they new backpressure to run Properly? Because they are TUNED to run with the specific exhaust system and the specific backpressure. Our BMWs are smart enough to adapt a/f to changes in backpressure. Many cars (even nowadays) cannot adapt themselves well enough to compensate. Go back to carbureted engines- if you wanted to run with no headers, that would require significant tuning to run properly again. So how Does It run poorly if not tuned differently? Lean. What happens when you run too lean? Burnt exhaust valves. Case and point: high school, Hyundai Elantra GT loaner car, a buddy thought it would be funny to take the header completely off. Although it was so obnoxious it was funny, it not run properly at all. Further, upon return my friend was charged $2400 to replace the head due to burnt exhaust valves.
So, you are right in the sense backpressure is not good for performance, but if it is tuned to be there, it, needs to be there.

Bottom Line- eliminating all backpressure is not beneficial for all engines unless you tune it to accommodate.

Last edited by BrianMN; 11-21-2010 at 11:54 AM.
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      12-07-2010, 07:46 PM   #52
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just did the muffler delete today. one word amazing! will have a video up probably tomorrow
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      12-07-2010, 08:13 PM   #53
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just did the muffler delete today. one word amazing! will have a video up probably tomorrow
At least you have res on the pipes, mine doesn't.
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      12-07-2010, 08:40 PM   #54
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just did the muffler delete today. one word amazing! will have a video up probably tomorrow
Sweet I can't wait to hear it.
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      12-07-2010, 09:16 PM   #55
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i just did my exhaust as well to match the quad diffusor. first muffler delete, realized it was way too loud and drony (sp?) and then ultimately just had magnaflows put on. i have no desire to pay the BMW tax for a mod that isnt going to help as im more interested in looks anyways. that, and i think it sounds wonderful the way it is now
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      12-08-2010, 01:47 AM   #56
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muffler delete easy to do and reversible
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      12-08-2010, 02:06 AM   #57
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lol
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      01-09-2011, 09:21 AM   #58
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only one way in my book and on my car, dimisa tips

www.dimisatips.com and they have the straight angle ones back!!!
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