Sauce

Hey guys, im plannin on getting a 3 inch piping exhaust. How much power is really "lost" compared to getting a 2.5 inch piping. The reason im planning on getting a 3 inch is because I dont wanna have to redo my whole exhaust system after boost comes into play. Thanks guys

Irish_tc_518

Its funny you posted this today, I just started designing a custom intake, which I found out that the parasitic losses @5000RPM are 5x as much on a 2.25" as they are in 3" pipes (according to Bernoulli's equation). Thats why injen intakes are the best, they use 3" pipes in their CAI. But it applies to exhaust since flow in= flow out. If you went for like 4" custom pipes you would start to lose tho cause of the pressure losses and turbulence. I think our engines would max out usefullness at about 3.5" with a turbo.

Edit: you may lose some power in the low end of the TQ curve. But gain at the top. The exhaust is a strange beast. There can be back pressure effects if the pipes are too large for the amount of flow you have. In short, there is a perfect pipe size for a specific RPM.

GetIt

Like nike says "just do it"

Sauce

Hehe i like that!

&& Irish I didnt know that AEM made em 3" for thier intakes. Im only rockin a WR short ram which i doubt is made to 3"

Irish_tc_518

No no injen makes the 3" one, I think AEM's is 2.5 But honestly dude the secret weapon is the worst intake of all. Dont get me wrong, im not bashing weapon-R cause I love their headers! But from a fluid mechanics standpoint its a terrible design. One pipe inside another doesnt vortex anything, it just makes more turbulence and pipe friction. They would have made a better product if they just left out that inner pipe. Plus people like to call it a "hot air intake" lol since its sucking in the hot engine bay air.

Sauce

yeah Injen is what I ment. Idk i personally think I paid too much for mine when I bought it (200 shipped)

Irish_tc_518

edited original reply

3min3m2

Honestly a 3inch is not necessary. I'm turbo with 2.5, and it is definitely sufficient.

Here's a trick to save some cash, but gain a good bit of flow and keep low end torque:
Get 2.5" mandrel bent piping the whole way, and then get a convertor up to 3in, with a 3in muffler. The smaller piping gives you that snap torque when its on the bottom end, and enough flow for the top, since its the muffler that causes most restriction.


Have fun either way.

xdejablu3x

i plan on getting 2.25" all around and tsudo 4-2-1 header. would it be better for 2.5" though since thats the size of the tsudo/weapon-r?

draxcaliber

it really makes no difference what so ever.

supercharged tC, 7 psi, weapon-r header, s-pipe and trd exhaust: 209 whp.
supercharged tC, 7 psi, weapon-r header, s-pipe and full 3 inch exhaust: 212 whp, and a loss of less than 1 lb-ft of torque.

oh, and BTW, you're exhaust volume will be over 140 decibels at WOT, and that is with a muffler, resonator and high flow cat on it.

if you need proof, listen to the videos below, compare the noise of my exhaust with the noise of the other cars running. also notice the gentleman at the starting gate cover his ears as i take off. yeah, it is really friggan loud.

http://www.youtube.com/watch?v=m7RFaiKu-LA

http://www.youtube.com/watch?v=FsVbnOC-Y-c

3min3m2

If your going turbo it will quiet exhaust down, FYI.

rangerryda

iTrader: (1)

Most definitely! I run a Turbonetics setup with 2.5" all the way back. I have NO RESONATORS, NO CATS, just one Magnaflow muffler and it's as quiet as OEM with a little gurgle at just the right tone I love it! Soooo many people ask how my exhaust is so quiet. I can only chalk it up to Magnaflow and the turbo aspect.

ScionFred

iTrader: (1)

I just installed a 3" exhaust and regret it. I wish I had gone with a custom 2.5" exhaust instead. I thought I could add a bigger resonator to quiet it down but even a 7" x 18" made little difference above 2000rpm. The only thing that makes my exhaust tolerable is the baffle/silencer in the tip. I'm starting to think that the only way to keep a large tube exhaust quiet is with a baffled muffler like Rangerryda has.

2.5" also fits much better than overkill 3". OTOH if your plans are for 400+ whp, go with 3".

rangerryda

iTrader: (1)

Yeah, 400 whp and up, who cares what it sounds like lol. Wear earplugs, they're cheap!

jwallace045

@ drax, damn bro that sh*t is loud!!

Irish_tc_518

Thats a really good point! When I posted that original reply I wasnt even thinking about noise level. Definitely a big consideration if you wanna keep it streetable.

draxcaliber

yeah, i actually drove with the car like that for over a year. i even drove cross country 1000 miles straight with my exhaust like that. it was epically loud as i refered to it.

now it is much better, still loud, but quieter and mellower.

http://www.youtube.com/watch?v=RyEIdyPpouA

ScionFred

iTrader: (1)

The answer lies in the oem exhaust design. Scion tapered the exhaust size for a good reason, to keep exhaust gas velocity high. I'm not sure about the TC but the XB2 starts out at 2.25" and then tapers to 2", then 1.8". IMO you should stick to 2.25" ID. 2.5" would be too big for a NA 2AZ.

rangerryda

iTrader: (1)

Ours is scrunched up to about 1.5 inch inside the stock spipe at the very beginning, then goes to 2 1/4 I think, then through another car and resonator, and just before the resonator, it shrinks a little again, then the axle back which resembles a septic tank or possibly a charcoal grill with a cool looking exhaust tip! lolz. In other words, suck!

jwallace045

I like it! nice bro and <3 the boost