N54 - Custom single exhaust

[totti84]

Hi guys

I have searched and not had any luck

Has anyone successfully attempted in getting a custom single 3.5inch exhaust made? Joined just after the downpipes, running a single highflow cat and piping all the way?

Is there any clearance issues? Performance benefits or downfalls?

Do any companies offer this off the shelf?

I thought this would offer some decent weight saving over twin 2.5inch pipes all the way

Thanks for any input
Steve

[jwongie]

http://www.1addicts.com/forums/showthread.php?t=519018

No high flow cat though, also not sure if it is still in production.

[totti84]

jwongie - that's exactly what i'm after (I'm happy to add my own high flow cat) but I'm pretty sure its no longer available

[katsooba]

Hi,
i have 3.25" exhaust turbo back with two custom made mufflers.
its more quiet but burlier down low
never measured flow,
im with Variant 3 30 mm lowered coilovers, never had a scrape, just from my garage exit, which is mega-steep.

[jwongie]

Originally Posted by totti84

jwongie - that's exactly what i'm after (I'm happy to add my own high flow cat) but I'm pretty sure its no longer available

Could just have some one fab one up? Wouldn't be too complicated. . . just gotta space out the brace far enough . . .

[totti84]

What brace are we talking about? Is there any details/photos showing the issue with clearances?

[rac]

i just had twin 2.5" mid pipes swapped out for 3" single.

i haven't spaced out my tunnel brace all the way yet but will do when i get a chance, it will be possible. look under your car near the stock resonator to find the brace we are talking about. my ground clearance is ok. i think 3.5" will be more difficult from a tunnel brace and ground clearance perspective (depending on suspension set up).

are you sure you need / want 3.5"?

[totti84]

Rac - how low is your car?

When you say space out the brace, do you plan on simply inserting a couple of washers to give the bracing more clearance?

I'm not positive if 3.5inch is needed, I just assumed it was the logical upgrade from twin 2.5's

[rac]

Originally Posted by totti84

Rac - how low is your car?

When you say space out the brace, do you plan on simply inserting a couple of washers to give the bracing more clearance?

I'm not positive if 3.5inch is needed, I just assumed it was the logical upgrade from twin 2.5's

I'll check, I think its around ~90-100mm at its lowest point, I was 106mm before. If you want to be safe, assume that you cannot reduce the clearance between tunnel and top of pipe, then just take the difference b/w want you want in there and what is in there, and that should roughly be what ground clearance is reduced by. From memory the stock midpipes are 2.25"? So if you put 3.5" in there you might lose 3.5-2.25" = 1.25" of ground clearance, or, 0.75" for 3".

In reality the fabricator might be able to do better than that.

Washers - yes. But it will be a few more than a couple. Single piece spacers would be neater.

i see your logic in that the x-sectional area of a 3" single is less than 2x 2.5" mids. However I calculated the gas flow pressure drop through a single 3" pipe to be less than 2x 2.5" (although its very close). This is a function of better flow area to surface area ratio. Not only that, I had really poor off-boost throttle response around town with the 2x 2.5" pipes compared to a 1x 3". imo you will lose clearance going to 3.5" pipe with little benefit.

[Nugget]

Originally Posted by rac

I'll check, I think its around ~90-100mm at its lowest point, I was 106mm before. If you want to be safe, assume that you cannot reduce the clearance between tunnel and top of pipe, then just take the difference b/w want you want in there and what is in there, and that should roughly be what ground clearance is reduced by. From memory the stock midpipes are 2.25"? So if you put 3.5" in there you might lose 3.5-2.25" = 1.25" of ground clearance, or, 0.75" for 3".

In reality the fabricator might be able to do better than that.

Washers - yes. But it will be a few more than a couple. Single piece spacers would be neater.

i see your logic in that the x-sectional area of a 3" single is less than 2x 2.5" mids. However I calculated the gas flow pressure drop through a single 3" pipe to be less than 2x 2.5" (although its very close). This is a function of better flow area to surface area ratio. Not only that, I had really poor off-boost throttle response around town with the 2x 2.5" pipes compared to a 1x 3". imo you will lose clearance going to 3.5" pipe with little benefit.

Who made it for you?

[totti84]

I wonder if a 3.25inch single is an option?

[questionable]

Is it really going to make that much of a difference from a 3inch ?

[totti84]

The way I look at it, if I'm going to spend $2000-2500AU for a catback and axle back system off the shelf which will be a 2x 2.5inch system, I may as well get a custom setup which:
- will save weight for having a single midpipe/cat/resonator
- save me having to buy two cats instead of one
- get a quad muffler setup
- all of the above for less than $1500AU

I have an awesome exhaust fabricator which is capable of building anything, I just need to find out what size is best for the n54 and he will make it!
I should probably see what he recommends, but thought I would check with the experts of here first

[Nugget]

You could always get an exhaust like this made
http://www.n54tech.com/forums/showpo...&postcount=125
Light weight and seems to flow well enough for a big single turbo.

[rac]

Originally Posted by Nugget

Who made it for you?

genie exhaust. i was there on the dyno and he offered use of a laser to get me back and forward to work while they did work on the car. otherwise i would have gone to Ramp, but Malaga is a PITA for me to get to during work hours.

~$600 to cut out the mids and weld in the single.

[rac]

confirmed 90mm ground clearance at lowest point, so i lost 16mm ground clearance from the stock midpipes.

[totti84]

That ground clearance is fine with me, my last car had a ground clearance of 60mm!

Rac - Do you have any photos of your setup on a hoist or prior to installation?

Would you recommend the 3inch or should I gamble with a 3.25 or 3.5inch?

[rac]

Originally Posted by totti84

That ground clearance is fine with me, my last car had a ground clearance of 60mm!

Rac - Do you have any photos of your setup on a hoist or prior to installation?

Would you recommend the 3inch or should I gamble with a 3.25 or 3.5inch?

no photos on a hoist. you should be able to find stock photos on hoist somewhere on a forum.

my Y piece is immediately after the DP's, from there it goes through to an after-market resonator that sits just behind where the stock resonator would sit, and then to a straight through single inlet double outlet high flow muffler.

not sure that i need the resonator to be honest.

the real reason i went to a single is so that i had 6 pulses going down that length of unrestricted pipe (i am catless) rather than 3. and that doubled the frequency at cruising speeds from ~100Hz to ~200Hz, which solved my low cabin drone resonance issue i was having. it was either that or put cats back in.

regarding pressure loss, the cat you plan on installing will cause a pressure drop probably an order of magnitude bigger than dropping 3.5 to 3". if you believe corky bell's rule of thumb chart (page 133 of maximum boost), 3" single will support ~700bhp. perhaps modern opinion has changed, or maybe just modern marketing.


r.

[miggs]

3.5 exhaust set up is loud. I have the HPF exhaust on my 135 which is a 3.5 the car is stock height if I'm not careful enough the exhaust will scrape on dips on the road and of course going into drives

[totti84]

miggs - do you have any video's or photo's of your setup?

[miggs]

Originally Posted by totti84

miggs - do you have any video's or photo's of your setup?

sorry for the late response i just saw this. i have one video of when i first installed it and turned it on during cold start. i also have a few videos of me racing other cars i can share. as for pictures i only have the tips from a rear shot i took of the car.

[totti84]

Please share if you don't mind