Another Exhaust Question.

[robots]

Hey!

I wanted to upgrade my 3inch exhaust a bit. Make it less noisy and give a car more road clearance.

I scrap my exhaust in the basement parkings every time. Awful.

I thought if I split the pipings from the turbo outlet. Make it two 2 or 2.5inch pipes running to the resonator and a twin entry muffler at the back.

Will I have still have the sufficient flow ? Like 3inch exhaust ? I thought 2inchX2=4inch, no? )))

Anyone done something like that ?

Thanks!

Edited May 30, 2008 by robots

[Rolls]

its Pi*r^2 so its not simply double. Twin 2" will flow almost as much as a 3", where as twin 2.25 will flow slightly more, flow goes up exponentially as you increase the radius.

Edited May 30, 2008 by Rolls

[tridentt150v]

In area, what Rolls says is true. Area is larger. However there are other factors such as surface turbulance and drag that take away the advantage. A 3"pipe has less surface area for the gases to pass over than two 2" pipes. The best way to visualise this is to think of the gas as it passes through. The best way to visualise this is to think of the gas as it passes through. At the surface gas velocity is zero, and somewhere in the centre [depending on flow patterns] the flow is at 100% efficiency, in this case 2 may not equal 1. To be definitive about it you'd have to do simulated or real flow comparisons.

But it will help to stop you dragging your exhaust.........lol

[robots]

So say, I run two 2.5inch. I get nice silent power then ))) Under Db limit. No scrapping exhaust. And performance wise comparable to 3inch. Right?

[tridentt150v]

Maybe?? real world === probably

[09ONE_32]

What makes you think that you will get silent power?

I though that noise = low restriction = more flow

[psi]

twin pipes weigh more! 2x cats (but they will be cheap due to small bore), 2x the mufflers/resonators.

they will also loose more heat dure to more surface area, the hotter the gas, the better the flow(kinda like oil, flows better hot).

But problems are just that, so it is do-able.

Twin 2.25" pipes will take up some room, you will have to stagger the cats so you can fit it all in. You will also have to look at some really good flex pipe, or you will suffer cracks.

The 2 pipes should flow more, but i think that will be determined by the quality of the collectors. if you can seperate the gas smoothly and then join it again in the same way, you have a good chance.

my thoughts..

[Rolls]

How low is your car?

[robots]

Its not ubber low. But my cat is scrapping every where. At best, I would like the exhaust to be same level as chassis rails. That way I won't scrub it.

[saliya]

Hey!

I wanted to upgrade my 3inch exhaust a bit. Make it less noisy and give a car more road clearance.

I scrap my exhaust in the basement parkings every time. Awful.

I thought if I split the pipings from the turbo outlet. Make it two 2 or 2.5inch pipes running to the resonator and a twin entry muffler at the back.

Will I have still have the sufficient flow ? Like 3inch exhaust ? I thought 2inchX2=4inch, no? )))

Anyone done something like that ?

Thanks!

Hey,

You might want to visit a competent exhaust shop.

1) Proper muffling on a 3" system will allow you blat around legally; you will lose _some_ flow compared to a 3" straight pipe but the better muffler designs allow more flow for the same noise.

If you need to add/change mufflers from remember that the inlet/outlet of the new muffler(s) does not need to be centred (see (2))

2) If you're trying to stop scraping - first of all, if your car's dumped on its guts you might want to re-evaluate that

Ask the shop how hard it would be to push your current system up as high as it will go without touching/melting things,

and what extra clearance you can get by doing that. You might be able to get that 0.75" by remounting the current system.

If you have to replace mufflers/cat then offset mufflers/cats can allow you to get quite a lot of extra clearance by rotating the body to 'where you want' rather than 'where it is'.

If your rubbers are stretched/broken/wrong type you might get out of it for the cost of a few replacement rubbers and an hour of shop time.

Even if the exhaust mounts need to be cut off/rewelded you're probably only looking at a couple of hundred bucks to fix it if it's possible

(some exhausts just won't sit properly if they're too high).

If the design of the current exhaust is crap (e.g. downpipe off the turbo is too long, causing the entire system to be too low) that

_may_ be able to be corrected with a hacksaw and a welder easily. Cleaning up the inside afterwards, however, will not be so easy.

I have an R32 on the SK Whiteline/Bilstein combo which is a little lower than stock; with a 4" system underneath including a 150mm cat.

More than 100mm clearance everywhere at the recommended ride height. So it can definitely be done in terms of clearance.

If you have other reasons to go dual ('something different', 'bling', 'something-else') or other reasons to go new ('holes in system', 'want new pipes', 'bling', 'something-else') you need to factor those in too.

No point getting work done that is ultimately not going to make you happy

But if it's just noise and scraping I'd go get your existing pipework looked at because repairing/modifying the existing system is likely to be a lot cheaper and easier than fabrication of a new dual system.

Regards,

Saliya

[robots]

thanks for the input, saliya!

[STATUS]

So say, I run two 2.5inch. I get nice silent power then ))) Under Db limit. No scrapping exhaust. And performance wise comparable to 3inch. Right?

We bought in a couple of R33 GTR's years back with crazy twin 2.5" systems on them both done by tommy kaira (spelling) sweet sound and nice clearance (one had full underbody aero panelling)

[psi]

Be very clear of what u are really wanting and wanting to acheive!

A mate of mine has spent BIG $$$$ changing the sound of his car, he is on his 4th set of mufflers and 2nd lot of pipes!

and he is still going on about it..

ask LOTS of questions, check out the shops work before u start the process.

if your only after hight, then do the above stuff, if bling, go for it. But in either case get it DB'ed after its done. If you want to keep it legal, I'm sure the shop is more than willing to help if you tell them BEFORE they start the job. If you dont care what it reads, get it done just for laughs! Most shops dont charge u to test it..

[STATUS]

the best place i have found in aus for exhausts is exhaust technology in SA..... long way to travel but after trying 30 or so after markys work i just feel jaded.

iF YOUR REAL KEEN HE WOULD PROBABLY SOURCE A CAR IN SA AND BUILD IT FOR YOU AND FRIEGHT IT. (stupid caps )

[R31Nismoid]

Unless your over 300rwkw - 3" is perfectly fine