custom exhaust need help(opinions) LONG!!

[A_325i]

ok well im new to these boards i just found them tonight and figured i'd ask you guys your opinions..Alright then here goes

It all started when my exhaust started falling apart i decided to look for a catback system and found only really expensive ones or really cheap crappy ones so i went to some exhaust shops to get some estimates for a custom exhaust one place quoted me 800$ for dual 2" piping from the x(h?) pipe to a dual 2" in/out cat then dual 2" piping all the way to a dual 2"in 3"out magnaflow muffler...800????!!!! and that was if i provided everything? including muffler cat and all pipeing? i thought ok this is rediculous..so i shopped around some more and have come to the conclusiong that getting a custom dual exhaust setup is jsut far to expensive for me to afford...so i got a quote for a single exhaust system and im pretty sure ive decided on one but i would love some opinions....i got quoted $300 flat i provide muffler cat and pipes (its pretty much all labor i guess) and heres what i have decided to get

first the shop will cut the dual exhuast pipe right after the x(h??)pipe right before the stock cat then they will weld this cat in place

(unfortunatly i can not find a cat that is dual 2"in single 2.25" out so i have to compromise and get 2.5" out hopefully the shop can make a tapered pipe to go from 2.5 to 2.25)

then they will cut bend and weld this piping 2.25"


and that will go all the way to this magnaflow single 2.25" in dual 3"out muffler



now my only concern is this 2.25 will add too much back pressure there for decreasing performance? im sure it will be better then what i have now but i also dont want to lose any power and the guy at the shop said if i go any higher with the piping i would have clearance issues? ok i guess my questions are.....is 2.25" piping ideal for the stock m20 2.5l engine or will it add too much backpressure? or would in increase performance?...if its not big enough then what is the largest diameter you guys suggest without going too large (i dont want 3" thats just too big and i know ill have clearance issues)....btw would this entire setup sound good? or am i getting a rice exhaust? opinions please...i have been researching extensively about this exhaust thing and there are just so many options yet i have so little knowledge of this stuff i dont know what is ideal for this car and what will sound perfect....thanks in advance for your replies and im sorry for writing so much and not using any puncuation tehehehe :twisted:

[EverWiser]

If you're worried about backpressure stay 2.5" between the cat and muff. That'll be more than enough flow for a relatively stock M20 and still give you room to "grow" and hopefully won't result in any clearance issues.

[MR 325]

Maybe I am udnerstanding your post wrong but don't bother with dual exhaust, single will be just fine. As said above, go with 2.5 though, you'll be happy you did later on.

Good luck

[JRKOUPE]

I have also been thinking about same upgrade but would like to hear from some1 who has DONE it...




on a single pipe system I have heard from many that 2.25 is fine for stock m 20. I dont know specifically how 2.25 will be diff than 2.5. Our stock duals are 45 mm I believe.



I am curious how the car will run and how it will sound. Its a bit of a gamble to not know.


if your cat is ok , then you can consider 2 " duals out from stock cat into dual in/single out magnaflow. I am leaning this way.......

[A_325i]

well yea i dont want dual pipes now because its way to expensive...but anyways they told me at the shop 2.25" is pushing it for clearance and that 2.25" is perfect for my car but i was just wondering what you guys had to say about back pressure and blah blah because i know these cars need back pressure to run correctly so you say 2.5"? how will this sound with the stuff i buy? i hope it doesnt sound too ricey and i dont want it to sound raspy either my buddy got a custom single 2.5" pipe into a $5 ebay muffler with DTm tips and it sounds good but way to raspy and i dont want that

[MR 325]

Well if you go with single 2.5 it will be just a tiny bit bigger than what the stock dual system flows, it's the perfect upgrade and I can assure you of this. If you go 2.25 it will be too small. I had a full custom system on my car, headers 2.5 piping, and one of those dual tip ebay mufflers, Magnaflow copy. Oh and I ran nbo cats, just a glasspack in the center section. I fucking LOVED the sound it made, it was awesome. My exhaust lives on on I3uller's car, lol

More or less, go with 2.5, trust me

[A_325i]

alright i placed the order for the same stuff only all 2.5" and the magnaflow muffler 2.5" in and dual 3" out cat is dual 2"in single 2.5"out and i bought 12 feet of 2.5" pipeing now since i spent all my money on this stuff lol i gotta wait to save up anbother 300 so i can get everything installed :-P oh man i cant wait :twisted:

[JRKOUPE]

alright i placed the order for the same stuff only all 2.5" and the magnaflow muffler 2.5" in and dual 3" out cat is dual 2"in single 2.5"out and i bought 12 feet of 2.5" pipeing now since i spent all my money on this stuff lol i gotta wait to save up anbother 300 so i can get everything installed :-P oh man i cant wait :twisted:

...so your cat will be acting like a y pipe( 2 into 1 )...got it.


Im pumped for ya......get those bucks together!


please show pics and or sound clip.....good luck..........!

[JRKOUPE]

..meant to ask..what brand cat and part no?.......


are you running stock oe pipes into your new cat?

[MR 325]

alright i placed the order for the same stuff only all 2.5" and the magnaflow muffler 2.5" in and dual 3" out cat is dual 2"in single 2.5"out and i bought 12 feet of 2.5" pipeing now since i spent all my money on this stuff lol i gotta wait to save up anbother 300 so i can get everything installed :-P oh man i cant wait :twisted:

Nice, let us know when you get it all setup

Glad you went with the 2.5

[A_325i]

yea beleive me im much happier going 2.5 i was worried baout clearance but i was even more worried about too much backpressure with the 2.25

yes i am running stock headers and downpipe into my 2 in 1 out cat which will be acting as a y pipe...they said they would have to custom make a y pipe so i decided why not make it easier on them and just get a 2 in 1 out cat..

and the cat is a magnaflow high flow converter which im getting from performance peddler(cheapest place i could find) if anyone knows where i can get one any cheaper then please let me know the part number is Product ID: MAG94007 its the 94000 series

i am so anxious to get this installed and get rid of the marbles knocking around in my cat and the hissing sound coming from the leak and i cant wait to get rid of the nasty rusted rotting muffler hmmm oh and did i mention its going to be nice to get rid of the 800 lbs that the stock exhaust system weighs lol

i would love to record the thing once its done but how would i go about doing that? i can get pics but i just dont know how to get a recording




oh yea one last thing..i read in some other threads that you guys were talking about glasspack mufflers....so i splurged a little and bought a 2.5" in/out thrush magnum glass pack which now my exhaust will be set up exactly like this


stock(ugly)headers- stock pipes with o2 sensor - 2"dual in 2.5"single out cat- 2.5"pipe- 2.5"in/out glasspack- 2.5"pipes- 2.5"single in 3" dual out muffler


i can not wait to hear what this sounds like ive never heard a setup like this ...have any of you? what do you think it will sound like? i hope its not raspy and i honestly dont mind a slight drone but i want it to be loud to kind of drown out the ticking sound of the m20 engine

[MR 325]

That glasspack may quiet it down a little too much, the cat should do enough. I only added the glasspack because i was catless

[EverWiser]

If the stock "i" exhaust pipes are 45mm each, that is a cross sectional area of 3181 square millimeters. A single 2.5" pipe has a cross sectional area of 3167 square millimeters so you'll still be just a grunt smaller. To be honest, however, the stock 45mm pipes are probably a little more restrictive due to twice the pipe surface internally (circumferencially). The two 45mm pipes have a total circumference of 565mm and a single 2.5" pipe has one of 399mm so if you equate that to the internal surface area of the pipe, the exhaust gases will "drag" across more pipe surface on its way through the stock "i" pipes. This would produce more backpressure than a single pipe with less surface area to drap upon. "Ain't math fun!".... :D

[A_325i]

hmm i hope the glasspack doesnt quiet it down too much.....maybe i should call and cancle the order for it?...

[Kristuphir]

I doubt it....I have a magnaflow, with an aftermarket cat, and it is LOUD at low rpm's...so loud I took it back to the shop and had them put an e46 resonator on it, which made more or less no difference. Sweetens right up after 2500rpm though...drives me nuts. :)