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09-19-2020, 10:43 PM | #1 |
Scooby Specialist
Member#: 57064
Join Date: Mar 2004
Vehicle:2008 STi IAG built HTA86 E85 Kel272s Cos IM |
Easy 10% power gain: wastegate as exhaust bypass
Solid lines = hp and tq with cutout Dotted lines = hp and tq before cutout +80whp! XONA Rotor 8269S 0.82 AR @40psi both runs Running IAG Stage 4 extreme with stock crank + IAG stage 5 heads with Kelford 272s I chose the PTE 66mm wastegate over a traditional cutout because it is made of materials that can stand up to exhaust gas heat and offer optimum seal. No failing electric motors or metal valves that don't seal causing exhaust leaks. The wastegate opens at 15psi boost pressure Everyone should definitely do this mod if you want a quiet exhaust without sacrificing power when you get on it
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Last edited by user1029; 09-20-2020 at 01:18 AM. |
09-19-2020, 11:00 PM | #2 |
Scooby Newbie
Member#: 452601
Join Date: Aug 2016
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great results why the difference in spool though
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09-19-2020, 11:34 PM | #3 |
Scooby Specialist
Member#: 57064
Join Date: Mar 2004
Vehicle:2008 STi IAG built HTA86 E85 Kel272s Cos IM |
Less back pressure = quicker spool
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09-20-2020, 12:36 AM | #4 |
Scooby Newbie
Member#: 383291
Join Date: Mar 2014
Chapter/Region:
MWSOC
Location: Great White North
Vehicle:2004 Forester XT Cayenne Red |
No, the graph shows no cutout = faster spool. Therefore more back pressure = quicker spool.
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09-20-2020, 01:00 AM | #5 |
Scooby Specialist
Member#: 57064
Join Date: Mar 2004
Vehicle:2008 STi IAG built HTA86 E85 Kel272s Cos IM |
Oops mislabeled by me
Dotted line is no cutout Solid line is with cutout I'll upload another graph |
09-20-2020, 11:14 AM | #6 |
Scooby Specialist
Member#: 179846
Join Date: May 2008
Chapter/Region:
NWIC
Location: Renton, WA
Vehicle:07 STi Limited EFR 8474 TS EWG |
your turbo and exhaust housing is to small for your power goals
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09-20-2020, 11:30 AM | #7 |
Scooby Specialist
Member#: 57064
Join Date: Mar 2004
Vehicle:2008 STi IAG built HTA86 E85 Kel272s Cos IM |
Honestly my power goal was 700whp and then I said what the hell and added the cutout, here I am at 800whp
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09-20-2020, 02:53 PM | #8 | |
Scooby Newbie
Member#: 495630
Join Date: Dec 2018
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Quote:
??? there is more torque where the graph starts over approx. 800-1000 RPM ramp up from 3000 to 4000 WITH the cutout. Then they merge without the cutout and then with the cut out really takes off. |
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09-20-2020, 02:58 PM | #9 |
Scooby Newbie
Member#: 495630
Join Date: Dec 2018
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09-20-2020, 03:31 PM | #10 |
Scooby Specialist
Member#: 57064
Join Date: Mar 2004
Vehicle:2008 STi IAG built HTA86 E85 Kel272s Cos IM |
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09-20-2020, 03:32 PM | #11 |
Scooby Specialist
Member#: 57064
Join Date: Mar 2004
Vehicle:2008 STi IAG built HTA86 E85 Kel272s Cos IM |
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09-20-2020, 10:22 PM | #12 |
Scooby Specialist
Member#: 57064
Join Date: Mar 2004
Vehicle:2008 STi IAG built HTA86 E85 Kel272s Cos IM |
You can get even earlier spool by running a wastegate spring that opens even earlier I didn't want to terrorize my local school zone just leisurely driving through it
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09-21-2020, 02:42 PM | #13 |
Scooby Newbie
Member#: 495630
Join Date: Dec 2018
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09-21-2020, 03:19 PM | #14 |
Scooby Specialist
Member#: 179846
Join Date: May 2008
Chapter/Region:
NWIC
Location: Renton, WA
Vehicle:07 STi Limited EFR 8474 TS EWG |
Most important thing is pre-turbo back pressure if you doing 40 psi and your back pressure is 60psi then your motor wont be happy camper
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09-21-2020, 03:32 PM | #15 | |
Scooby Specialist
Member#: 239822
Join Date: Mar 2010
Chapter/Region:
South East
Location: America's Penis
Vehicle:2010 WRX pandiculation |
Quote:
Honestly, I'm filing this in the 'great idea, but mad at OP that I didn't think about it myself' folder... |
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09-21-2020, 05:51 PM | #16 |
Scooby Specialist
Member#: 57064
Join Date: Mar 2004
Vehicle:2008 STi IAG built HTA86 E85 Kel272s Cos IM |
Prior to doing this mod, I scoured every google result but nothing tangible. Hopefully I set a precedent with this solid test and hopefully nothing bad happens in the coming months
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09-22-2020, 11:12 PM | #17 |
Scooby Specialist
Member#: 57064
Join Date: Mar 2004
Vehicle:2008 STi IAG built HTA86 E85 Kel272s Cos IM |
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09-23-2020, 02:10 AM | #18 |
Scooby Newbie
Member#: 494541
Join Date: Nov 2018
Location: TX
Vehicle:2009 wxr wrb |
Is a tune required fore this mod?
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09-23-2020, 06:26 AM | #19 |
Scooby Specialist
Member#: 57064
Join Date: Mar 2004
Vehicle:2008 STi IAG built HTA86 E85 Kel272s Cos IM |
Yup definitely, you will instantly run lean otherwise
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09-23-2020, 08:31 AM | #20 |
NASIOC Vendor
Member#: 198281
Join Date: Dec 2008
Chapter/Region:
MAIC
Location: Virginia
Vehicle:2005 WRX/STi WRB of course |
No 2 ways about it, if your exhaust is a bottleneck you either need a cutout or a custom exhaust. This is the far more economical route as getting a larger diameter custom exhaust it big $... and it's still going to sap some power over a cut-out.
On a +700whp setup here's a 3" to 3.5" megaphone at the turbine outlet that transitions to 4" oval under the car, and back to 3.5" round at the muffler. VERY expensive. I don't recall what we lost over the dual side-pipe setup that was just deafening (even with a helmet on), I want to say ~30whp, but the full cat-back would allow you to hear a passenger without having to scream directly into their ear, lol. Last edited by KillerBMotorsport; 09-23-2020 at 09:43 AM. |
09-23-2020, 09:40 PM | #21 |
Scooby Specialist
Member#: 409636
Join Date: Dec 2014
Vehicle:2015 WRX |
I have a cutout like this on my 15 WRX. Been running it for years. It’s boost activated but also on a switch so I can use it when I want to and keep it quit when I need to. It’s mounted as a 3” dump at the end of the y-pipe just before the stock mufflers.
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09-24-2020, 09:47 AM | #22 |
Scooby Specialist
Member#: 25731
Join Date: Oct 2002
Chapter/Region:
MWSOC
Location: Ft Wayne, IN
Vehicle:02 wrx(sold)/2005 Sti/ 93 Leg Wag |
Genius. So no vacuum lines or anything, just opens up on spring pressure? I have an old 38mm Tial I can use. Not as big but even little is better than none I'd imagine.
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09-24-2020, 04:53 PM | #23 |
Scooby Specialist
Member#: 57064
Join Date: Mar 2004
Vehicle:2008 STi IAG built HTA86 E85 Kel272s Cos IM |
Give it 15psi of boost and it'll open or whatever spring you choose. No need for any fancy solenoids
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09-28-2020, 12:58 PM | #24 |
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Member#: 241967
Join Date: Mar 2010
Vehicle:02 wrx |
the spring pressure without any boost hose to the wastegate will keep 15psi pressure in youre exhoust system...
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10-04-2020, 08:49 PM | #25 |
Scooby Newbie
Member#: 519125
Join Date: Oct 2020
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Nice!
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