Drop in low end performance? - Subaru WRX Forum
 
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#1 Old 07-14-2006, 03:39 PM
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Drop in low end performance?

Installed my Helix UP/DP and Apexi catback, disconnected/reconnected battery and so far have driven a little over 100 miles. I've noticed a drop in low-end performance, although top-end seems far superior to stock. Just wondering if this is normal?
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#2 Old 07-14-2006, 03:53 PM
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no I noticed a gain all through the spectrum. Less back pressure allows the turbo to spool faster and at lower RPMs.

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#3 Old 07-14-2006, 05:28 PM
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Quote:
Less back pressure allows the turbo to spool faster and at lower RPMs.
True, but not always true. Imagine if you had a 4.75" pipe? Talk about no back pressure.

Either way, I think it's just a placebo affect. Unless something is wrong with you car, dyno plots prove that an aftermarket TBE will give you power at both low and high end.

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#4 Old 07-14-2006, 05:36 PM
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Is the UP you used the same inside diamater as the stocker? Because this has been debated, larger up pipes may actually make your car slower due to less velocity, but more volume. I don't know how it actually works out, but it may be true.

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#5 Old 07-14-2006, 05:56 PM
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Quote:
Originally Posted by genkidama20
True, but not always true. Imagine if you had a 4.75" pipe? Talk about no back pressure.
Yes but how many exhausts manufactured for the WRX are that large and secondly the turbo supplies all the back pressure needed.

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#6 Old 07-14-2006, 07:03 PM
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Bigger UP's slow your spool. You're pushing air over an aerodynamic surface (turbine), its all about speed. But the Helix shouldn't hose your low end.

I'm going to say you were expecting more low end gain than you got, and that makes you think you actually lost power.
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#7 Old 07-14-2006, 07:39 PM
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Did you keep your factory turbo shield? If not you may be getting heat soak from the Turbo

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#8 Old 07-14-2006, 08:55 PM
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What was the size of the up pipe that you put on there? A drastic change in size could account for the difference in low end power.

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#9 Old 07-14-2006, 11:29 PM
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he says he installed the Helix UP, I have that installed as well. Unless Helix came out with different sizes.

Quote:
The Helix uppipe features:


-High quality double layered flex section - Reduces torsional vibration on vital exhaust components and turbo, also ensures perfect seal (even with aftermarket headers, downpipes, etc.)
-Thick 1/2" 304 Stainless Steel Flanges - to prevent warping and reduce heat expansion
-304 Stainless Steel Mandrel Bent Piping - Ensures proper flow and durability
-CNC Machined EGT bung - seats EGT properly unlike competitors which will eventually leak. (The EGT is there for a reason!!)
-2.25" piping diameter - optimal for upgraded turbos
-includes OE style gaskets (from same factory as OEM gaskets)

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#10 Old 07-14-2006, 11:43 PM
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Thanks for the feedback. I'll try to answer all the questions at once. The UP looked maybe a hair larger, maybe by a 1/4" or so, or maybe it was just my eyes playin' games b/c I never really thought to measure it. Secondly, no I did not re-install my turbo heatshield, I was going to order an aftermarket like Cobb makes but maybe I'll re-install it tommorow, does anyone know where to find the pics of where to cut it to fit aftermarket DP's? Lastly, tonight I drove out to the car show near me, I now have about 175 miles since the install, I drove it pretty hard tonight and it seems to be coming to life so I'm happy about that. Is that heatshield something you guys would definitely reccommend? Thanks, scooby1220.

P.S. I installed the Kartboy shifter also, worked out nice, very simple install. Doin' the bushings sometime soon.
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#11 Old 07-15-2006, 12:00 AM
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The heat shield i would personally install. That turbo gets real hot and will considerably heat up your intercooler, which means less power.

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#12 Old 07-15-2006, 12:25 AM
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I had to fit the heat shield in place, see where it was touching and cut it out. did that about 3 times and it worked perfectly.

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