Exhaust question

[nofx]

I'd like to upgrade the exhaust on my 2012 Nav. I've read all the posts I can find, and dropped in to a few exhaust places which has resulted in some conflicting information and a few questions that I can't answer.

I've read with interest that the Beaudesert 2.75 system has a 2.5 dump pipe and that they have responded to some guys that "the 2.5 dump doesn't affect performance of the 2.75 system". It seems intuitive to me (but am more than willing to be wrong, I am only guessing), that if the 2.5 dump pipe is the narrowest / most restrictive part of the system, then it will govern the flow through the entire system won't it, and you might as well have 2.5 straight through? A bit like the weakest link in the chain or like water flowing through a pipe of two different sizes. Can anyone tell me one way or another if that is correct?

Now my second question. Two different exhaust / performance places have told me that I can go and get a mandrel bent 3" or 2.5" system with 2.5 dump or I could just get the 2.5 dump, a high flow cat and cut the muffler out for way less dollars and pretty much the same performance gains and EGT reductions. They said that the difference between those two options would be measurable on a dyno but would be insignificant enough that a driver wouldn't notice. Has anyone here taken the cheaper option? What was the result? Even better, has anyone here taken the cheaper option then upgraded to a full system later? Did you observe a performance difference when you upgraded?

Long post I know. Sorry. Thanks for your help.

Brett

 

[Nakkers]

Interesting, looking forward to peoples opinions!

 

[04SilverSTR]

IMHO the beaudesert system albeit more expensive is bloody good quality!! and come with everything like shorter studs for the turbo, I really dont think the smaller dump is an issue, 3'' dumps on the 2.5's are very much a squeeze from what i have read and if you have a cat in there to there would be much space! I know rustynav has a beau system so he can elaberate more for the yd25 nav.

my 2c

bryan

 

[DHDamo]

I'd like to upgrade the exhaust on my 2012 Nav. I've read all the posts I can find, and dropped in to a few exhaust places which has resulted in some conflicting information and a few questions that I can't answer.

I've read with interest that the Beaudesert 2.75 system has a 2.5 dump pipe and that they have responded to some guys that "the 2.5 dump doesn't affect performance of the 2.75 system". It seems intuitive to me (but am more than willing to be wrong, I am only guessing), that if the 2.5 dump pipe is the narrowest / most restrictive part of the system, then it will govern the flow through the entire system won't it, and you might as well have 2.5 straight through? A bit like the weakest link in the chain or like water flowing through a pipe of two different sizes. Can anyone tell me one way or another if that is correct?

Now my second question. Two different exhaust / performance places have told me that I can go and get a mandrel bent 3" or 2.5" system with 2.5 dump or I could just get the 2.5 dump, a high flow cat and cut the muffler out for way less dollars and pretty much the same performance gains and EGT reductions. They said that the difference between those two options would be measurable on a dyno but would be insignificant enough that a driver wouldn't notice. Has anyone here taken the cheaper option? What was the result? Even better, has anyone here taken the cheaper option then upgraded to a full system later? Did you observe a performance difference when you upgraded?

Long post I know. Sorry. Thanks for your help. Brett

I'm in the same boat as you nofx - I wanna upgrade exhaust but my brain tells me that a small pipe into a big pipe won't allow it to 'breathe' better as it will be restricted by the 2.5 dump. Have read heaps about it on here - and I'm listening but not fully convinced on the 2.75 or 3 inch system. Like you said, if its 2.5 wide at the dump, won't a 2.5 straight through allow as much flow as any larger pipe?

Happy to hear opinions, see dyno results or whatever to fix my brain tho.

 

[DHDamo]

Oh, and I'm saying the Beaudesert system isn't better quality - i'm more considering the pipe sizing (as I think nofx is).

 

[nofx]

Yeah, you nailed it Damo. I'm certain that any of the after market systems will be an improvement and that some of them are fantastic quality, but my questions relate specifically to pipe size vs restriction and performance benefit of full system vs increasing the dump, replacing the standard cat with a high flow cat and chopping out the muffler in the factory system. The latter option can be done for only a few hundred bucks and if the difference between the two options is only discernible on a dyno, then I know which option I'll take.

 

[DHDamo]

How much is the new cat and remove muffler chop job goin for? Have read around the forum about custom 3 inch systems for 600-700ish which seems cheap - but if they still have a 2.5 dump is there any point (other than bettter quality)?

 

[happy john]

Just go for the beau everything lines up build quality is fantastic those extra mm you want mean nothing sure the price is more but you will be more than happy.

 

[nofx]

How much is the new cat and remove muffler chop job goin for? Have read around the forum about custom 3 inch systems for 600-700ish which seems cheap - but if they still have a 2.5 dump is there any point (other than bettter quality)?

About 500 all up they said. Getting a firm quote on Monday; the supplier of the last place I went to was closed on Friday afternoon so need to wait till Monday. The cheapest quote I have seen was 1200 (installed). I did see one thread for a Sunshine Coast mob, can't remember the name, that I think had them for that price, but if I understood and remember correctly, they had shut down or something?

Just go for the beau everything lines up build quality is fantastic those extra mm you want mean nothing sure the price is more but you will be more than happy.

Yeah happyjohn, that's exactly what I am chasing. You say the extra mm won't make much difference so why would I pay 1500 (I think, from memory) for Beau, when the chop job all lines up as well since its all factory pipe and just adding after market cat and dump? Sure it will probably look ugly, but I'm not trying to win beauty pageants.

 

[rabbit-chop]

get the cheapest mandrel bend straight through system with dump pipe you can find that fits. 2.5", 2.75", or 3" makes no difference except maybe a bit more of a note in the larger diameters if you don't run a muffler. all the back pressure your engine is going to get is going to be in the exhaust mani no matter what you do bar changing turbos, and talk of differences in gas veloctity with the different sizes is farts in a high wind.

my 2c

 

[04SilverSTR]

a free flowing 2.5in dump has got to be better than the cast straw they have there now!!!

 

[bods]

If anyone wants to read it, I did find this which may help choosing sizes http://www.tercelreference.com/tercel_info/turbo_exhaust_theory/turbo_exhaust_theory.html

 

[user 10312]

Good read! Once again proving the exhaust is before the turbo, not after it. Another way to look at it, is everything after the turbo is the dump.

Just a thought, thinking out aloud now but maybe even staggering a couple of 45 deg. bends may be more advantageous over using 90's

 

[bods]

Its definitely possible to do it that way. The other thing is to have long radius bends, although its not always possible to do that... The hardest part in these cars is the front subframe where the front diff sits having to do weird bends through there. Once you get past that it is pretty much a straight run to the rear at least

 

[DHDamo]

a free flowing 2.5in dump has got to be better than the cast straw they have there now!!!

What size dump do they come with standard?

And yeah, that article was good reading.

 

[bods]

What size dump do they come with standard?

And yeah, that article was good reading.

Probably about 2" but its more like a 90deg elbow as opposed to a smooth radius bend like the aftermarket ones are. So instead of the exhaust coming out of the turbine and smacking into a wall then heading down the aftermarket ones help it flow down better...
If that makes sense lol

 

[nofx]

If anyone wants to read it, I did find this which may help choosing sizes http://www.tercelreference.com/tercel_info/turbo_exhaust_theory/turbo_exhaust_theory.html

Thanks for the article, its given me some knowledge to be better able to make a decision, or at least ask better questions of retailers etc..