So I am going to have a exhaust built soon and was curious should I run a 3.5" or a 4" exhaust?
I currently have a 3.5" DP and a 6765dbb TS 1.15 Turbo PW66mm WG ..
I was looking into a 4" vibrant resonator with a vibrant 1155 muffler
http://www.ebay.com/itm/Vibrant-1155...59e0f4&vxp=mtr
has anyone ran one of these?
I ran the 3" version of the resonator and muffler on my old NA e36 m3 and loved it.
2002 911 Turbo k16 billet, JIC Coilovers, GT3BBK, Cobb Mafless, Oz Ultra
I have a 4" straight pipe on my 2.8
[ame]http://www.youtube.com/watch?v=PZnDWSk4XGo[/ame]
Ground clearance sucks. I scrape the V-bands all the time.
-Mike
IG: @mikevanshellenbeck
I run 4 inch exaust with two borla racing mufflers here is a vid:
[ame]http://youtu.be/xB83loAfsaU[/ame]
1991 bmw 325I <e30>
First 8 second full body BMW with BMW independent rear suspension in the USA
8.69 @160mph in a 1/4mile on slicks.
drag radial tires record holder9.53@148. Also a world record holder for bmw overall 60-130mph 4.2 seconds.
Bistein sport susp,turner sway bars,3:25lsd,m52 AEM INFINITY stand alone. MORAN 2500cc injectors E85 ,front mount 33x12x4 intercooler, 5lug conversion M3 front,Mcoupe rear Dss axles/driveshaft ATI Proglide.
2003 Ford Expedition
1998 M3
1986 Mercedes Cosworth 190e 2.3 16v 5speed (sold)
In the process of building a complete 4 inch oval exhaust now. Hope to be done by 1/1/13.
The e30 had a 4" exhaust.
http://www.e30tech.com/forum/showthread.php?t=55729
Last edited by BenFenner; 12-03-2012 at 09:55 AM.
One of my bigger mods planned for the new year is I want a 3.5-4" exhaust....worried if I can keep the sounds down with 4" but I foresee big gains over my current 3"..decisions!
I'm sure there is power to be had but... I made over 630 with a 3" down pipe, 3" exhaust, magnaflow resonator and dynomax vt muffler. My exhaust is far from perfect. it looks like a shitty muffler shop welded it up. It's not pretty or ideal and it supports decent whp.
OLD
E30
636whp
1/4 mile: 10.91@144.38
http://www.youtube.com/watch?v=L_f7fUVqblI
NEW BUILD
335d
520whp
635wtq
120.51mph trap speed
I know why someone with an 8 second 1/4 mile car has a 4" but it doesn't make a lot of sense for the rest of us.
97 BMW M3 (s52b32) - VF-Supercharger kit ( Vortech V2-SQ supercharger, 32 pound injectors, VF tuning ), VDO/LeatherZ Gauge Kit (Oil Temp, Oil Pressure, and Boost), UUC Motorwerks RSC36 Exhaust, Stainless Steel 6-2 Exhaust Headers, Bilstein Sports, Rear Adjustable Camber bushings, Wheel Spacers 10mm in front 25mm in back, Uprated Clutch, UUC Shift Knob, Short Shifter and Clutch Stop, Cross Brace, Mason Engineering front strut bar, Contour Wheels, Euro Ellipsoid (Angel Eyes) HID Headlights, braided steel brake lines, aluminum thermostat housing, mishimoto aluminum radiator and silicone hoses and a partridge in a pear tree
Hey boris, why are you running mufflers at all? Your car seems pretty much drag only, wouldnt the mufflers detract from the awesome noise and add a little (if insignificant) amount of weight?
Believe me, I want it too. Just not sure if the minimal difference in spool and slight HP gain is worth fitting a huge exhaust under the car. Especially if it's louder and scrapes on every bump.
I think there have been significant gains made in the Supra world although I remain skeptical... I don't think I'd see a 50-100whp gain (suggested on the supra forums) if I went to a 3.5-4" exhaust. Maybe though...
OLD
E30
636whp
1/4 mile: 10.91@144.38
http://www.youtube.com/watch?v=L_f7fUVqblI
NEW BUILD
335d
520whp
635wtq
120.51mph trap speed
A little math for fun...
Area of a circle: pi × r2 with pi = 3.141593
Area of an oval: pi x L x W
4" circular exhaust diameter =12.566 in2
4" oval exhaust (~2.75" tall and 4.375 wide) =9.449 in2
Circle = ~33% bigger
(12.566 - 9.449 = 3.117 / 9.449 = answer, if I understand correctly. )
3.5" circle = 9.621 in2
3.5" oval (~2.5"L and 4"W) = 7.854 in2
So, circle = ~22.5% bigger
Continued:
4" oval is ~1.82% smaller than 3.5" circle.
4" oval is ~33.67% bigger than 3" circle
For reference, a 3" circle is 7.069 in2.
More fun - 4" circle is ~77.76% bigger than a 3" circle.
All things to keep in mind when making a decision on exhaust size.
So, if I were to build and exhaust, then I would definitely go for a 4" exhaust if possible. Also, I definitely would not go from a 3" circular exhaust to a 3.5" oval exhaust because it is only ~11.1% bigger.
This is my signature....
I'm getting my stuff from Spintech (mufflers and tubing) I'm planning on doing a thread on it as soon as I get a little farther along with the fabbing.
I assume it may not flow AS good as round, but better than my 3 inch is good enough for me.
Thanks for the math. Great information there !!!!
My initial intent for going oval was due to clearance issues with my 3 inch. My V-band clamp took one helluva beating due to my car being low. And since my goal was ground clearance, 4 inch oval seemed to be the only sensible choice. So.... with that being said, I will be gaining a 33.67% bigger exhaust AND gaining ground clearance.
Several months ago, I found a couple good articles (Supra stuff IIRC) talking about considerable whp/wtq increases when increasing exhaust size. IE from 3 inch to 3.5. As with anything, there are multiple variables. I should have some results pretty soon. My last dyno was 598/516 and I am changing ONLY the exhaust, so the comparison will be apples to (bigger) apples .
Holy math dump...... thanks for the info brother!
Actually. I tend to agree with you. I was looking at some oval tubing online, and it looked very rectangular.
Hence. I used the best numbers for oval pipe I found. I'd really be interested in seeing some actual numbers.
My numbers were more so for fun. Either way, the circular measurements should apply though.
Sent from my iPhone 5 using BF.com
This is my signature....
I has a sewer pipe.
This space for rent.
I have 5" down and 4" under and back whit 1 large muffer on my E34 turbo.
Nice sound and 89db whit DB testing on track
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