Lots of Questions

[utlize]

I have an AEM intake with an air bypass valve.(It rains a lot here) I want to put a high performance muffler on I have read a few postings on the flow master muffler. I called Midas for and estimate on it, with 3 inch pipe and a flow master 50 series for about $350 out the door. What do you think? I need a header haven’t found one yet should I get a header first? What suggestion do you have on headers at a good price? Finally yet importantly, fuel pumps and pressure regulators. What is available and were can I get them?

[VIO]

i4 or v6?

[HeadAche]

First and foremost 3in pipping for your exhaust is way to big unless your on the bottle or boostin.. Headers on our applications have found to have no real horsepower changes besides the 1 or 2 whp gains. A FRP you can get from RPW or RRE, and the fuel pump you can get from Walbro..

[utlize]

It is an inline 4. I will be boosting in the future. So would a 3 in be ok or should I go smaller? Will a header help or not?

[Xavier22]

shane just said a header only gains bout 1-2 hp, maybe a lil' lil' more - and its been proven on a dyno sheet - basically, dont waste your $$!!!

[VIO]

if he goes to forced induction the headers will be a good thing. by themselves they add next to nothing for our cars but when you start quickly pushing massive amounts of air and fuel into your engine you need to be able to get the exhaust out just as quickly. as for 3" piping i think that's a bit much on the i4. i would say 2.5" to 2.75" would do just fine especially if it mandral bent. if you went with headers and 2.75" piping you'll probably lose a bit of power until you get forced induction. in a larger diameter pipe the exhaust cools much quicker making it dense and heavy. i'm thinking headache would be a better person to answer your piping questions in regards to our cars though. personally i would go with headers from ripp. from what i've heard they are a nice bit of kit for sure but you'll certainly pay for it as they are about $650 i think but according to them the are about as perfect a design as you can get for the i4. now whether this is true or not i cannot say as i have not seen a dyno sheet on them. as for a fuel pump, walbro 255, it's the champ. i don't think many people will disagree on that one. i'm assuming that you'll also be upgrading your injectors are well yes?

[Fishboy55]

<div class='quotetop'>QUOTE(VIO)</div><div class='quotemain'>if he goes to forced induction the headers will be a good thing. Â*by themselves they add next to nothing for our cars but when you start quickly pushing massive amounts of air and fuel into your engine you need to be able to get the exhaust out just as quickly. Â*as for 3" piping i think that's a bit much on the i4. Â*i would say 2.5" to 2.75" would do just fine especially if it mandral bent. Â*if you went with headers and 2.75" piping you'll probably lose a bit of power until you get forced induction. Â*in a larger diameter pipe the exhaust cools much quicker making it dense and heavy. Â*i'm thinking headache would be a better person to answer your piping questions in regards to our cars though. Â*personally i would go with headers from ripp. Â*from what i've heard they are a nice bit of kit for sure but you'll certainly pay for it as they are about $650 i think but according to them the are about as perfect a design as you can get for the i4. Â*now whether this is true or not i cannot say as i have not seen a dyno sheet on them. Â*as for a fuel pump, walbro 255, it's the champ. Â*i don't think many people will disagree on that one. Â*i'm assuming that you'll also be upgrading your injectors are well yes?</div>
Just to qualify that, if he goes FI with the blower he can get gains with the header. If he decides to go FI with a turbo, the headers will have to go. That's my dilemna right now.
Didn't mean to crap on your post Vio or increase my post count by repeating what you said, just want to make sure all the options are clear.

[utlize]

Do you all think the flowmaster would be a good choice?
Fuel pressure regulator and pump what volume pump should I get and what should I keep it regulated at? How is this going to effect my PCM. If it affects my PCM what can I do to counter it.
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[Auto-9]

<div class='quotetop'>QUOTE(utlize)</div><div class='quotemain'>Do you all think the flowmaster would be a good choice?</div>

For me, no. They are not a straight through design. But, some people swear by them. About the mandrel bending thingy...I was told by a pro racer that for forced induction, mandrel bent tubes are not recommended, but I forgot all the physics talk he used to explain it to me. For naturally aspirated cars, they need all the assistance they can get breathing.

[Stewi]

Im running 2.25" cat back with an Apexi N1 muffler, sounds really throaty, 2.25 or 2.50 are good, but I wouldn't recommend using 3" til you go turbo, im going turbo soon and im just gonna get rid of the 2.25" and go for 3". I got the piping installed and welded to the muffler for $150.

[VIO]

<div class='quotetop'>QUOTE(Fishboy55)</div><div class='quotemain'>
Just to qualify that, if he goes FI with the blower he can get gains with the header. If he decides to go FI with a turbo, the headers will have to go. That's my dilemna right now. Â*
Didn't mean to crap on your post Vio or increase my post count by repeating what you said, just want to make sure all the options are clear.</div>

oh well yeah! i forgot to mention that you'd have to use a turbo manifold if you went turbo! :oops: of course you wouldn't be able to use headers with a turbo. i guess i just assumed that since he was speaking of headers and forced induction he meant supercharged as opposed to turbo. thanks for catching that though as that is an important bit of information! 8)

now, as for rallifan's post about naturally aspirated engines needing all the flow they can get i don't agree. the most important aspect of an exhaust system for an n/a engine is the rate of flow of the exhaust as opposed to the diameter of the piping. it does make sense that the larger the pipe the more exhaust you can flow. to a point this is correct, however you must take into consideration that hot gases flow much easier and faster the cooler gases. when you move to 3" piping it allows the exhaust gases to cool too quickly as the 2.4 doesn't push out a really large amount of exhaust in it's naturally aspirated form. it just doesn't have the displacement and flow rate to keep the exhaust hot. the exhaust cools by the time it gets past a few bends and then gets heavy thus making it harder to push out. now i do agree that a straight through design is better simply because it's less restrictive. yes a large pipe is also less restrictive but it's a different type of restriction. bends are restrictive because a) if they are not mandrel bent then the bends are "pinched" causing the piping to have a reduced diameter in the bend and the exhaust is forced to change directions and a bit of turbulence is created as the exhaust hit's the side of the pipe. thus the greater the angle of the bend the greater the turbulence. a large size pipe is less restrictive because there's more space. but it's a different type of restiction. now back to the velocity of the exhaust. the exhaust gases are moving at a fairly high rate when they exit the engine and the valve closes. now during the time that the valve closes and before it opens again a vacuum is created, the higher the velocity of the exhaust gases the greater the strength of the vacuum. the greater the strength of the vacuum the quicker the exhaust is pulled/pushed through the pipe. in order to keep the velocity at a maximum you need to find the best balance when it comes to piping. i.e. not too big so the gases cool too quickly and not too small as to be restrictive to the flow rate due to piping size. this is why when you move to a large pipe you can lose low end power. there's not a lot of exhaust being pushed out at low rpm's and it get's cooler more quickly then when you're at wot. and of course when forced induction comes into play you're pushing a lot more air in and hence a lot more exhaust out. remember though, you can't push out more exhaust out of the engine then the amount of air you're taking into the engine. now when it comes to pairing mandrel bent piping and forced induction i'm not experienced so i can't comment on whether or not it's good or bad but i'd like to hear more about why it could be bad as i cannot see the downside to it. that of course does not mean there isn't a downside just that i can't figure out what it is.

[utlize]

So should I go with a 2.25 or an 2.50? I found a cat back system with the mandrel bending for 325.00. good price?

[VIO]

if you are for sure going to put your car on the bottle or forced induction then i would go with at least 2.5. if you're going to just put the standard bolt on and not much else then i myself would stick with 2.25 if it's mandrel bent. a mandrel bent exhaust will breath much better as the bends aren't piched. 2.5 you'll most likely lose some low end hp if you stay with stock displacement (i.e. you aren't going to bore out the cylinders) but you might gain it back in the upper rpm band when you're at wot. if you have a cali spec you could look at replacing the cats, if you have a fed spec like i have you should be good to go. fed spec breath a bit better then the cali's.

[Mante]

Im going to shed alittle light since everyone is giving opinions on fpr's, ask yourselves this..."does my fpr come with a gauge to measure the fuel?" chances are the answer is NOPE. There are makers that pulled there thumbs out there ass's and included the guage...OBX at the moment currently does. B&M does not, RPW does not anymore.