By Corky Bell 2.25" is enough for 250whp, 2.5" is enough for 400whp.

I'd go with motoria exhaust, it's cheap and good quality.

PS:
Tim has no cats like me, bash on him too!!!

Deniss, reply on my x3 thread when you get a chance.

 

But dude, Tims testing the limits of our motors, he IS going for the most HP possible. Its not that hes lazy or doesnt have the money, he has a good reason for runnig no cat. I understand your situation with money and all, trust me, but if your gonna dish out some cash no matter what, why not spend it right?

But I agree with you that the 2.25 should be ok for low boost, and I think most will agree.

 

Its not Tim's daily driver, which is the point. Either way, Corky is on crack with his little exhaust chart. One of the only parts of his book that I found wrong. Its more of a guide to where you should be (i.e you should be at least 2.25, but 2.5 would be better)

 

Does the car have to be street legal, or can race setups be used?

 

shame on you Tim. Seriously though, I will put up with Tim only because I would have wonder how many cats he would have melted by now.

 

No no...fluid mechanics (dynamics refers to the forces don't originate within the system...such as aerodynamics...dynamics is the branch from mechanics.) tells you that flow in is equal to flow out. Since I took this class last term...I'll bestow upon you dudes my knowledge...for those who care. For those who don't, eat my arse. eyeroll.gif

I'm going to go a little off-topic, which has everything to do with the topic. Since we're dealing with a closed system...(exhaust pipe...even your headers would work the same)...fluids in motion often fulfill the Qin = Qout [flow in = flow out]. However, just saying "flow" is a bit of faux pas...because "flow" consists of both area and velocity [in physics, it's basically the simple equation of Q = AV...if you don't know what A or V stands for, please shoot yourself].

Now, in the most simplistic case, that means Vin x Ain = Vout x Aout. You can change the area on one end, but depending on area or velocity on the output, you need to fulfill a balanced flow. Now...that's in a frictionless system. Of course, in reality, you get friction in the pipes...and the way the pipes are shaped. But it's not a total significant loss...but that again depends on multiple variables (expansion of the metal, smoothness of the inner wall...etc). So, the crushed bends impedes flow velocity. Overall flow out of the system is somewhat reduced as well, due to the friction caused by the inner walls of the pipes...creating turbulence.

The only reason I bring this up is so that when you guys do talk to someone who has a significant wealth of information on the subject, you don't sound dumb. Crush kinks would only impede on the velocity...so the flow inside the pipe isn't laminar, and becomes turbulent. Like aerodynamics, you want laminar flow rather than turbulent flow to maximize efficiency. I would personally shell out the big bucks for mandrel bent pipes than crush bent.

Don't think short term, think long term.

What if you decide to boost beyond 9psi? Sure, maybe for the temporary application, you'll want a 3" crush bent pipe, but if you reach your goal of 9psi, and you want more...you'll want to get a 3" mandrel pipe...which means you just wasted some money on getting the 3" crush bent pipe. Sure...might not be a huge difference, but that's money you could be saving up for a boost controller...manual or electronic. 3" mandrel may be a little too much for you now...but the temporary HP loss you get from that, is justified when you're boosting past your goal.

 

I looked in the Apexi site and couldn't find our exhaust (and many others).

For the 3" manderal I defintally need to wait until I get the turbo because of the backpressure issues. It would be extramly slugish until then.

Thanks

 

eek.gif

I had 2.25" Mandrel in mild steel installed for $96.75. I just took my car in and handed him the new muffler.

However, that $96.75 was wasted (along with the price of my header, muffler, and CAI) because I will be going back to the same shop this spring for 3" mandrel bends with a new muffler. This is prolly going to kill my power right now, but it will all be worth it once I start my 'special project' smile.gif

 

thanks for the more detailed analysis Arctic, what was what I was going for.. the reduction in flow due to turbulance.