Turbo exhaust advice!

1172 Views 14 Replies 7 Participants Last post by  nderwater
Hi peeps!

I have been running a custom 2.5" downpipe from my greddy turbo back for a short while now.

its making boosy quicker and is a little louder than before:

Now when i was N/A i had a custom dual exit de-cat back system made made by a custom muffler shop. It was very loud...but I liked it like that!:bigtu:

It is 2.1/4 inch back.

It looks pretty with its twin chrome / carbon tail pipes and single muffler.

Now the question is would i benefit allot from 2.5" haust all the way back? its only a 1/4 of an smaller at the moment.

if so what benefit would it make over the 2.5" d/p I already have?

I have been offered a custom exhaust to be made by a very reputable haust place in the UK and was thinking of have another dual tip exhaust but without a muffler or a CAT!

Is anyone running this set-up?

would this be unbearbaly loud with my greddy turbo and make spool even quicker or am I asking for trouble?
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We can't run without a cat here in Australia, there's a huge fine if you get caught.

Corky says 2 1/2 inch is big enough for any turbo MX-5 setup.

JDM says 3" makes more power.

2 1/4" might be limiting your power but the budget GReddy kits aren't designed to make lots of power.
Ok, I just checked your website, last time I was distracted by the girls and didn't look at the car enough :lol:

I'd spend the cash on an intercooler first :D
I have a saab 900 intercooler already and a new front month IC set-up going on shortly! :wink:
Well as to the amount of improvement in flow: Flow increases exponentialy with tubing diameter.

As to the loudness: Yep, no cat no muffler would be loud. There's some muffling from the turbo but it'll still be very loud.
would the turbo not quiten it down with no muffler!

I noticed a big diference in the exhaust note when the turbo went on! It was allot quiete and allot more induction noise.

It was also decat then but with the restrictive original greddy downpipe!

Running with no CAT is no problem in the Uk for pre - 03 cars and some of the Honda's VTEC NO TORQUE have stupidly loud buddy club hausts!
Run a 3" pipe going from the end of the downpipe to the back of your car if you want to notice anything. With a turbo it wont be loud.
someone told me with no rear muffler there will be no back pressure and a turbo needs back pressure.

If there is no back pressure I willeventually do my turbo seals supposodly?

Any truth in this?
False. Turbos hate backpressure. the less there is the better with a turbo setup.
Corky argues that if the exhaust is TOO big, then it will create turbulence inside and that extra turbulence adds back pressure.
3 inch will work fine, it will most definitely free up some ponies and the turbo will spool up a bit quicker. Turbos hate backpressure, the freeer they flow the better performance you will get. If you were naturally aspirated then you need some backpressure. Also if you're gonna get the exhaust custom made, try to have them make it as straight as possible. Turbo cars are usually pretty quite since the turbines chop up the exhaust note. Hope this helps.
the exhaust on my turbo nb is cracked and i was thinking of replacing it with a hi-flow cat and 3" stright pipe, but am afriad of how loud it will be. the crack in my current sys is right after the downpipe and the result is too loud inside the car. will throwing the unrestricted air out the back instead make that much of a sound difference inside the car?
:shock: More chicks with miatas :shock:
the crack in my flex pipe spread all the way around the flexor, dropping my exhaust onto the highway when it gave way. turbo + no exhaust after the down tube is hella, hella, hella LOUD. that is all.
I wimped out and nixed the idea of a straight 3". After my exhaust fell off I did some asking around and found that Enthuza is local to me, so I took my car to Jason for a custom 2.5" stainless system. It's a great looking piece of work, but it's quieter than I expected (although it sounds really good under full boost). i'd gotten used to a loud, raspy note but i guess that something a little more stealthy is a better match for a stock-looking daily driver. I'll post pix the next time the car is up in the air.

- Ian
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