3" or 2.5"

just went to the muffler shop in cleveland and they priced me a 2.5" system for $450.
Now reason i'm posting is i would rather not throw a chip into this truck just yet and BPS one of the tuners in my area say that if I go 2.5 i should not have to chip it as it should not lean out.
Also the muffler shop had a 3" system installed on a 2005 str last week and they said that the check engine light was coming on. They say that it was spooling the turbo to fast. So they went a 2.5" dump then 3" from there back.

I want to know all your thoughts and what you guys have done..

thanks joshy

I have a full 3" system, more than happy with it, no warning lights here.
A noticble gain, smoother & turbo spools quicker, chip next.

-JOSH- said:

Also the muffler shop had a 3" system installed on a 2005 str last week and they said that the check engine light was coming on. They say that it was spooling the turbo to fast.

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Crock of crap. Yes these guys can weld (sometimes) but everything else is just pseudoscience.

I went with a Beaudesert 2.75", right in the middle!

Runs a treat.

-JOSH- said:

just went to the muffler shop in cleveland and they priced me a 2.5" system for $450.

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Thats a pretty good price. Just check it includes the dump pipe and a high flow cat.

-JOSH- said:

Now reason i'm posting is i would rather not throw a chip into this truck just yet and BPS one of the tuners in my area say that if I go 2.5 i should not have to chip it as it should not lean out.

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Diesels don't need a specific air/fuel ratio like a petrol. With a 3" exhaust you we be running slightly leaner, but as the navs (zd30 I assume) run a map sensor the computer will slightly adjust the fuel to suit the higher boost pressure.

-JOSH- said:

Also the muffler shop had a 3" system installed on a 2005 str last week and they said that the check engine light was coming on. They say that it was spooling the turbo to fast. So they went a 2.5" dump then 3" from there back.

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Rubbish, The Zd30 has no sensors in the exhaust system, you 'could' run it without an exhaust and the check engine light wouldn't come on. (i only know because I've done it) The light is related to another problem.

So to answer your question, 3" is preferable but 2.5 would be almost as good, but only if its mandrel bent, otherwise forget it.

so u guys with the exahust did it get louder??...not a fan of noise unless it sounds beefy and not a whiper snipper type ;-s but would like to get better airflow..or maybe add some resinators...

nismo4x4 said:

so u guys with the exahust did it get louder??...not a fan of noise unless it sounds beefy and not a whiper snipper type ;-s but would like to get better airflow..or maybe add some resinators...

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Maybe slightly louder, but only with the window down at low speeds. Althought the turbo whistle is much louder

Mine is slightly louder, but not enough for my wife to realise that I had spent money on a new exhaust system........

slightly louder i could handle...turbo whistling is music to my ears ;-)

Jason said:

I went with a Beaudesert 2.75", right in the middle!

Runs a treat.

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Me too, very happy with the end result.

Matt - VNET Pro said:

Mine is slightly louder, but not enough for my wife to realise that I had spent money on a new exhaust system........

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Thats what i thought , but mine noticed the sound. And in the end after a few weeks i admitted it lol

2 3/4'' dump pipe, only cause its easier to get the bolts into and 3'' straight through exhaust no muffler but hi flow cat. Got a have a cat, the fine is not worth 1 kw of extra power !!! Slightly louder but whistles like a boiling kettle !!!

Just done the ring arounds for mine... 3' Exhaust turbo back with stainless 3' hi flow cat... No muffler...

Little bit louder but sounds good, like a beefy 4x4 with turbo whislte very noticable now. Seems to whislte from 1800-2700... after 2700 all ya hear is the snorkel sucking air in and no turbo whistle...

Would recommend 3' exhaust, noticeable power gain, higher speed at lower revs.. can sit on 100 doin 2400..

very happy 3' customer..

I have just built up a replacement pipe for the rear half of mine. I removed everything from the mid pipe (With the small resonator) back and put in a 2.5" pipe through a 6" X 24" round muffler with a small chamber in the middle. I can not pick a performance difference compared to running it with nothing behind the front pipe.

it is a touch louder than I was hoping for, I am holding off on judgement there, the pipe currently ends at the muffler so it may sound a bit different when I make and fit the tailpipe tonight or tomorrow. The outlet is currently blackening the spare tyre (From about 30cm away so no risk of heat damage. There are a number of pipe size transitions in the stock pipework. I cut the flanges off the coupling in front of the old main muffler, one side was large enough to slip just inside a 2.5" pipe and the other side of that join would just slip over the pipe where the front pipe coupled to the middle section (After cutting off the original flange) All in all it means that it has smoothly stepped up from the 2" section to the new 2.5" over a couple of inches of pipe without having to do anything really creative.

On the plus side, if I ever use it as a 4WD, at least the new pipe and muffler is tucked up between the rails instead of having the front of the muffler hanging down like the stock system.

I was originally talked into getting 2.5, the guy who did it convinced me that a 3 would loose to much back preasure ( what a load of crap) the 3" went in today and I could'nt help but let out a little giggle as I drove down the street, the difference is amazing. Dont waste your money on a 2.5" you'll only be wishing you had gotten the 3" later. Oh and to be fair I had the 2.5 madral bent system with the high flow cat in the truck for 2 yrs. So I did have enough time to see how well it worked.

Don't know if anyone is still reading this topic, but how well do they do fuel economy wise with the 2.5" and the 3"?

can anyone post an audio file of a 2.5lt with either a 2 1/2 inch of 3 inch exhaust to have a listen to?

3" all the way
with a nice low pitch nothing like a shopping trolley buzz box

where is a good place to get exhuasts?

i have a 2.5l cr td what sixe would be the best for this size engine and should i do cat back or dump pipe aswell, havent read much for this engine