Guys out there who has replaced your stock 2.5" exhaust with the bigger 3" one, does your turbo spool up sooner(lower rpm) or later(higher rpm) compared to stock exhaust?

 

the only way it will is if you replace the DP section... other than that, a catback isn't really going to have an effect on the turbo spooling...

 

Ok....if the downpipe and everything else after it is 3", does your turbo spool up sooner(lower rpm) or later(higher rpm) compared to stock exhaust?

 

Well in theory anything after the turbo, bigger is better. Less backpressure quicker spool-up and of course a less restrictive exhaust is going to flow more at higher rpms. Of course this is all in theory.

 

People have been saying that 3" turbo backs give u a better high end power, and a lil less torque on the low end. Just do a search, there have been countless postes on this subject.

 

well i will tell you this....i put my UR 3" TB on last night and OMG.....there is ALOT more power. It is like the car woke up. Turbo spools much faster and the dead leg from 5 to redline isnt as obvious. But I only drove it for about 10 minutes this morning so I will have a better understanding after today.

 

You want no exhaust, that is the best exaust. The less restriction, the more air that can be flowed throught the exhasut, = more efficient air to be pumped into you engine.

NO Doubt a 3.0 exhaust will ad some lag, and the turbo will just snap to life, so floor it at 3000, like 3500 THWACK 20PSI instantly and it will hold there, make the most power, and just keep on accelerating.

If you get a smaller exhaust, faster more contolled spoolup but with boost fall off and lack of highend flow.

get a 3.0, it is a Def.

 

My Evo snaps to 20psi and stays there and pulls hard to redline with just a Pruven axle back, mbc, and grounding kit.
I will say that a 3" is best if things such as bigger turbo are in your Evos future. With the stock turbo a 3" will also make more topend power closer to redline but will lose lowend/midrange torque..
A good 2.5" turbo back will give great power increases.

 

First of all, "pulls hard" isn't exactly quantitative.
I will append a blurb from the technical portion of my site.

Downpipes; What size? - Many individuals that are modifying a turbo car for the first time are concerned about what size to select for one of the first good modifications to most turbo cars; the downpipe. There are several theories floating around. Many tuners that are not familiar with turbo cars will think the sizing should be similar to normally aspirated techniques. In NA cars, increasing the size slightly can aid midrange and top end power while yielding minimal loss in the bottom end. If the size is increased significantly, however, the scavenging effects will be shifted to very high rpms and result in loss of power except at very high rpm where it is not useful. In turbo car theory, the larger the piping, the better. Bigger pipes mean less backpressure which works great for the turbo and power almost everywhere. Turbos work off of pressure differentials, among other things.

The most important thing to remember when selecting a downpipe is that both are actually true to some extent. When the car is off boost and at low rpms, the turbo can actually be of little resistance in the exhaust stream. At this point, the car will behave somewhat like an NA car in terms of downpipes. This usually happens on cars that either come with a relatively large turbo from the manufacturer or have been upgraded significantly. The Mitsubishi EVO8 is a car with low/midrange that will suffer from a downpipe without more extensive modifcations. The particular type of motor and the rest of the airflow setup (heads, manifolds, etc.) will also determine if this loss is felt or not. If the motor is built for midrange and topend, you won't notice much of a loss on the bottom end. The Toyota Supra TT is an example of this type of car. Once the exhaust flow is high enough for the turbo to start to cause a restriction, then it is necessary for it to do it's own part to improve the power output. From that point on, the downpipe requirements will raise quickly and settle into a "bigger is always better" situation.

Keep in mind that the EVO has an O2 housing which for all intents a purposes should be considered part of the downpipe.

Mark
www.Quantum-Racing.com

 

The turbo seems to spool up quicker and pulls harder then stock.