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Open Wastegate vs Recirculated Into Downpipe (Video)

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Open Wastegate vs Recirculated Into Downpipe (Video)

Old 09-13-15, 01:11 PM
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Thumbs up Open Wastegate vs Recirculated Into Downpipe (Video)

I've been tired of waking the dead with my open wastegate and I thought I'd share the results of a few different fixes I tried.

Here's a quick rundown of my setup:
Stockport S5 13BT, 9.7:1 rotors, Atkins seals
AEM V1 Water meth w/ 550cc nozzle
GT4088R, eBay FD manifold, Precision 46mm WG
3" DP, 3" Vibrant Ultra-Quiet Resonator, 3"ID/7"OD Magnflow XL Muffler, Very quiet setup by rotary standards.


Setup #1: 4" of 1.75" tubing staight off the wastegate.

LOUD. Like my ears would ring after a 1-3rd gear pull. It also put a lot of gas fumes into the cabin.
Even with the Precision 46mm WG, I was having boost creep issues.
With a 9psi spring and open dump, it would creep to approx 15 psi by redline.

Setup #2: 1.75" glass pack muffler and 2.25" tip.

This was an effort to reduce volume, not necessarily impact boost creep.
It did make the exhaust a BIT quieter, but not much.
It mostly knocked out some of the high frequency rasp, but didn't impact volume enough to keep around.
With this setup and 9psi spring, it would creep to 17psi by redline.

Setup #3: 1.75" tubing rerouted back into downpipe.

Because I do not have a TIG welder and I can barely MIG weld (see photos for proof lol), I chose not to merge the recirc at a shallow angle like it should. I ended up using a 90* bend that was cut to merge at approx 70-80*. Not ideal.
The difference in noise was HUGE.
I thought something was wrong at first like the turbo wasn't making boost because it was so quiet.
An added bonus was the reduction in boost creep.
With the same 9psi spring, I can now hold 13psi to redline.
I would say that 90% of my boost creep issues stem from the shitty wastegate placement of my ebay manifold, but 13psi is livable with 9.7:1 rotors and 93 octane.
That would be my base pressure without water methanol.

It's pretty hard to say if I lost any power with the recirc'd WG.
It now hits less peak boost on just spring, so that in itself is worth some power. Nothing the boost controller can't fix.
Being able to drive the car without feeling like a felon is worth a few hp, so I am happy.

Here is a video of Setup #1 vs Setup #3.
I never recorded Setup #2 because I wasn't really happy with the results and removed it after only a couple days.
It also had ground clearance issues that made leaving/returning my house a pain.


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Old 09-15-15, 07:53 AM
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hurting your ears every time you drive gets old. Here's my external WG routing on an FC:

Attached Thumbnails Open Wastegate vs Recirculated Into Downpipe (Video)-wastegate_recirc.jpg  
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Old 09-15-15, 01:01 PM
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That's definitely more elegant than my setup, but unfortunately my wastegate is very close to the downpipe. I may end up redoing my recirc because the ground clearance isn't great. My driveway is very steep and I've scraped it more than a couple times this week. May be easier just to raise the car lol.
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Old 09-15-15, 07:08 PM
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External wastegates need to be plumbed back into the exhaust to be road legal down here.

Here's my setup on FD with twin gates plumbed back IMO its a bit of a work of art. FD is RHD also..so also have the steering column to contend with.
Before it was welded up;




perfect fit, and check out them welds

Last edited by 96fd3s; 09-15-15 at 07:10 PM.
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Old 09-20-15, 12:43 PM
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I'm running a Full Race Manifold with dual 44mm MVR's dumping to the atmosphere. The sound is ORGASMIC.

I may go the recirculated route one of these days when I turn into an old man.
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Old 09-20-15, 01:03 PM
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Originally Posted by TheAsset View Post
I'm running a Full Race Manifold with dual 44mm MVR's dumping to the atmosphere. The sound is ORGASMIC.

I may go the recirculated route one of these days when I turn into an old man.

Try going up a 8% grade next to a mountain where everything is echoing off each other while you are on the boost for a couple of minutes.......I don't mind the open dump for the here and there full throttle. if you go ***** out on a canyon road it gets damn annoying.
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Old 09-21-15, 12:21 PM
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Originally Posted by lOOkatme View Post
Try going up a 8% grade next to a mountain where everything is echoing off each other while you are on the boost for a couple of minutes.......I don't mind the open dump for the here and there full throttle. if you go ***** out on a canyon road it gets damn annoying.
I live 100' from a large river. I have to climb a few hundred feet of elevation to get our of the valley to go pretty much anywhere. I would have to baby it to keep from opening the WG at all in 5th gear. Also, at 70mph on the interatestate, my cruise control will open the gates trying to go up these hills. It is funny seeing the look of confusion on the 65yo in the Mercedes passing you when you car suddenly gets 3x louder and you're notaccelerating lol.

Last edited by Shainiac; 09-21-15 at 12:58 PM.
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Old 09-21-15, 04:39 PM
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I'm no clear about how recirculating could have solved your boost creep? Normally it should be the other way around.
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Old 09-21-15, 04:56 PM
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Originally Posted by Narfle View Post
I'm no clear about how recirculating could have solved your boost creep? Normally it should be the other way around.
I think the idea is that all the additional gasses from the wastegate are flowing through the same 3" pipe as the turbo, turbine speeds are reduced. I honestly fought with the idea of it actually helping, but it did. I can hold 12psi +/- .5 past redline. Way better than with the open gate.
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Old 09-21-15, 05:02 PM
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Proof is in the pudding, right? Interesting that adding back pressure in the overall exhaust system trumped adding more back pressure at the gates.
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