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Old 07-23-2009, 01:45 PM   #1
Slug71
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Default Exhaust Upgrade?

So we just recently got a 03 Baja N/A. Im looking to do an exhaust upgrade on it probably in a month or so but want to get my homework started now.

Basically what i would like to achieve is to keep the cruck as quiet as possible at low-mid rpm range but as much power gains possible.

Im thinking of going for 2.25" Header back.

Im undecided on the Headers though. I was initially thinking Borla UEL headers, Stromung high flow cat pipe..?
Does EL/UEL make as much difference on a N/A as on Turbo?
Will EL be quieter than the Borla UEL?

If there really isnt much difference between the two as far as loudness and performance goes then i will probably just go with the Borla for the added 'rumble'.

Also im guessing that regardless of which header i go for and since the rest of the exhaust will be 2.25" with one high flow cat, i will still need to throw a resonator or mid silencer in there to achieve the sound issues?
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Old 07-23-2009, 02:12 PM   #2
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* UEL will make a nicer sound
* EL will add power.
* Either UEL or EL is better than stock
* Both headers will be louder (front engine noise) than stock due to their thin-wall, ticking-prone construction, however they won't change the loudness of the exhaust which depends on whatever comes after the header
* 2.25 sounds reasonable... lot of people put too big of an exhaust
*Cat back/ muffler... search through videos and audios of what people posted. Rs25.com also has a dedicated thread to it
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Old 07-23-2009, 02:57 PM   #3
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A full exhaust and an ECU tune will give you your two biggest gains in power until you feel like tearing apart the engine and doing cams.

Williaty posted a direct comparison of the UEL and EL headers that he ran on his car. He states that the test was baised towards the UEL header too as the engine was running somewhat poor when he had the EL one on, meaning the gains are actually higher then his info suggests.

Header sizing is important for proper engine operation. Header back piping and hardware is much less important. The header does all the tuning work. The rest just get the exhaust to the back of the car. Bigger is actually better when it comes to the rest of the exhaust but can be bad at the header (or intake runners, heads, cams) if the engine isn't built for higher rpm use.

I'll make a note that you can do custom work on the exhaust. You can grab a OBX or Borla header (depending on your goals, sound or power), and buy just a cat, a muffler, and a glasspack/resonator. Then walk down to an exhaust shop and have them fab up everything in between. Example:
OBX header - $300 (Borla replica around $200, burble but less power)
Car Sound 59955 cat - $100 (high flow, compact)
Magnaflow 4"x9" muffler -$70 (needs to be <20" body to fit between the bumper and sway bar, 14" body fits well)
Add $200-$300 tops for exhaust work and hardware, Midas works but you can shop around.

The pricing isn't bad at all.
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Old 07-23-2009, 06:22 PM   #4
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search. there is even a EL/UEL comparison thread with dyno plots and other logged data for an engine very similar to yours.

exhaust in general is the most discussed topic in this forum so there is tons and tons of useful info if you spend some time searching
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Old 07-23-2009, 11:43 PM   #5
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Thanks for all the info so far guys, will do some more searching.

From what i gathered so far though it seems there isnt much of a gain with ELs over UELs.

Now i know they both are louder than stock but is one louder than the other or just a different note?
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Old 07-24-2009, 03:40 AM   #6
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It's just a different note. the uel's give it a more boxer rumble. the el's has a tiny bit of that rumble but with a cat back it'll sound more hondaish. I just purchased the Borla reps off ebay and a 2.25 cat pipe. I personally want that rumble but to each his own. I'll let u know how it works out though.
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Old 07-24-2009, 12:31 PM   #7
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Yeh let me know how it goes. Would like to know if theres a noticeable difference in power over stock.

Now the stock headers don't really provide that 'rumble' so how different is the note between stock and EL?
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Old 07-24-2009, 12:51 PM   #8
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Ok guys don't flame me for this I'm saying that ahead of my question, but what do you think in a Borla header set up I should go with in terms of wanting to FI...do those same 2 1/4 be alright or would a 2.5 be a better set up. EL of course I personally don't think you lose the boxer sound as much as some say but who knows.
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Old 07-24-2009, 12:56 PM   #9
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Quote:
Originally Posted by Back Road Runner View Post
The header does all the tuning work. The rest just get the exhaust to the back of the car. Bigger is actually better when it comes to the rest of the exhaust but can be bad at the header (or intake runners, heads, cams) if the engine isn't built for higher rpm use.
Do you have data to back that up? The info that I've seen is that larger exhausts mess up the scavenging effect.

Haven't touched my exhaust yet and I want to make sure I understand what / if it is worth it to replace things.
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Old 07-24-2009, 02:18 PM   #10
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The scavenging is defined by flow velocity at the combustion chamber. Two parts in the car mainly control the flow velocity, the intake manifold and the exhaust header. They do effectively the same task, just on either end of the process. Head and cams will also play their part. The rest of the piping has less of an effect on this. There can be some influence, but it depends on how the exhaust is designed. Typically a header and what I'll call a "tuned section" is terminated by an inline resonator. It basically ends the majority of the influence of the pressure wave tuning. The intake has the plenum (small for our cars actually) and "torque box" and the stock exhaust runs a resonator, but you could also do the same thing with a large cat, glasspack, resonator, or even muffler. You just need a larger chamber of some sort to work as a low pressure area. After this point, the rest doesn't influence much. The last link below has a good visual of this both without and with an inline resonator. You can see why piping can be influential and how you can effectively terminate the tuned section and simply have the remainder of the piping.

Bunch of links/reading to go through:

Auto Exhaust Science
How Headers Work
HEADERDESIGN.COM - Header Design Concepts
Theory
the one and only exhaust thread here - Team Integra

A good read for the intake side of things:
the one and only intake thread here - Team Integra
Intake Manifold Tech: Runner Size Calculations - Team Integra
FLUID DYNAMIC STUDY OF INTAKE MANIFOLDS OF INTERNAL COMBUSTION ENGINES IN PRESENCE OF ACOUSTIC RESONATORS
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Old 07-24-2009, 04:54 PM   #11
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Haven't read those yet but thanks - I have some weekend reading to do!

I don't care what my exhaust sounds or looks like as long as it performs better than the stocker when I replace it. I generally research the **** out of something before I 'jump' - hell it took me 6 mos to decide on brake pads, SS lines and brake fluid
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Old 07-24-2009, 04:58 PM   #12
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Quote:
Originally Posted by Floyd420 View Post
Haven't read those yet but thanks - I have some weekend reading to do!

I don't care what my exhaust sounds or looks like as long as it performs better than the stocker when I replace it. I generally research the **** out of something before I 'jump' - hell it took me 6 mos to decide on brake pads, SS lines and brake fluid
Even though it's slow, you're doing it the right way! No use buying something and then not liking it.
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Old 07-24-2009, 05:04 PM   #13
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I try to learn from others mistakes
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Old 07-24-2009, 06:14 PM   #14
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Quote:
Originally Posted by Slug71 View Post
Thanks for all the info so far guys, will do some more searching.

From what i gathered so far though it seems there isnt much of a gain with ELs over UELs.

Now i know they both are louder than stock but is one louder than the other or just a different note?
With a search you will discover that the less expensive EL option will yield substantial gains over UEL (test done on 05 RS) the more expensive EL's probably wont yield much more, so it's probably a lot more money for a small gain if you compare the $200 ish EL's to the $900ish EL's. Without a tune, EL/UEL will make almost no difference. A tune is necessary to take advantage of the better design of the parts you install.
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