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Old 02-16-2011, 04:00 PM   #20
Scooby Guru
Member#: 261612
Join Date: Oct 2010
Location: Minneapolis, MN
2002 WRX - 750WHP
9.5s @ 150mph


Originally Posted by mapleleaf View Post
It's making the same power as your tune only car with a DP, what is amazing about that?
Originally Posted by Boosted WRX STi View Post
I didn't see the difference at first until I looked at the overlays. Its not only about peak numbers, its the area under the curve. Look at the difference in midrange power and torque compared to KWIL's stock downpipe. Pretty impressive for one mod.
Originally Posted by mapleleaf View Post
Impressive if it was a mod other than a DP. Maybe the stock IC is why they are holding it back as there is a lot more available on the table with a DP than what is reflected in that graph.
I answered this above. Here is my post:

Originally Posted by xluben View Post
I believe COBB has made it standard practice to limit boost on the high end with the stock TMIC. That is why Stage 2 setups don't really make much more peak power, but the torque curve is much better, even at lower boost.

Stage 2 was a big jump to my butt dyno. Definitely worth it.
I actually went and looked up both plots, and added the boost line to the plot. It makes it clear that my guess from above is what actually happened. The downpipe allows COBB to make the same peak power with considerably less boost pressure.

You can see that the peak boost is a hair higher, and has the expected response. Then in the higher RPM's the tune reduces boost to approx. 1.5psi less than the Stage 1 tune, and it is still putting out just as much power. I posted about this a while ago and COBB did confirm that heatsoak issues are what limits the Stage 2 power. If you look on their site, they do have Stage 2 runs with the boost pushed higher, and they do make quite a lot more peak power, but it probably won't be reliable without a new TMIC.

So with a downpipe you get your choice of:

-the same power, more torque, and presumably greater reliability (due to less boost)
-significantly more power, way more torque, and push everything else to the max

If you choose the second one your TMIC and BPV will be at the verge of blowing apart, the injectors will be maxed out, and the car could knock if heatsoak kills the IC efficiency enough. Generally it would be better to go with a safe Stage 2 and enjoy the extra torque, and lower stress on the turbo. If and when you upgrade the TMIC, BPV, and injectors, you will be ready for plenty more power. If you go this route you'd still need the downpipe anyways, so you might as well get rid of the biggest restriction right off the bat.
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