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DIY Turbo Discussion greddy on a 1.8? homebrew kit?

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Old 02-19-2012, 10:58 AM   #101
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SP exhaust valve works very well and honestly they have put in on everything from 1200whp supras to 800whp supras with stock exhaust systems. Car is quiet until you get on it. Spool might be effected slightly but nothing a quick spool valve can't fix. Those are amazing.

Loud exhausts are annoying espc. on none "race car" or any car you drive alot.

SP is currently building a 7sec "street supra" With both of these items. Thats should prove they work and work well.
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Old 02-20-2012, 01:54 PM   #102
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I'm sure someone has done it, but I wonder whether a 3" downpipe and a 2.5" catback would be an acceptable loss in power for the noise reduction? Vlad, you're from the Suby world originally, so you should know what I'm talking about.
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Old 02-20-2012, 02:38 PM   #103
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Yeah, many do it, the power difference is all up top past 5k and the spool is off by about 200rpm. I have dyno plots of my own forester going from stock 2.5" exhaust with 3" dp to 3" full turboback I'll post up when I get home.

I have a feeling I'll probably end up going full 3" exactly like the one I had before though. Watched the clips of my white one last night and OMG does it sound good lol.

I plan to test all 3 versions though, just for giggles:
3"dp w/ stock exhaust.
3" dp w/ stock exhaust + boost cutout
3" dp w/ 3" exhaust

If I like option2 I wont even switch to option3. If I don't, well you know the rest.
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Old 02-20-2012, 02:50 PM   #104
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Another idea I had is: What about using an EWG?
You can get a 60mil off egay for like 70 bux. That's like 2.25 inches or something like that.
They even have ones that open at 4psi.
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Old 02-20-2012, 02:58 PM   #105
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Quote:
Originally Posted by 18psi View Post
Another idea I had is: What about using an EWG?
You can get a 60mil off egay for like 70 bux. That's like 2.25 inches or something like that.
They even have ones that open at 4psi.
That's creative. Go for it. You could always mount up several on your downpipe. If you had different sized wastegates, it would sound interesting.
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Old 02-20-2012, 03:36 PM   #106
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Quote:
Originally Posted by Savington View Post
I'm sure someone has done it, but I wonder whether a 3" downpipe and a 2.5" catback would be an acceptable loss in power for the noise reduction?
Full 2.5" exhaust at close to 300 whp will show ~10 psi of backpressure. My 3" full exhaust with spring loaded flapper shows 5 psi. At this power level it would be silly to use a 3" downpipe and a 2.5" exhaust. Far better off to go with a full 3" system with a spring loaded flapper.
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Old 02-20-2012, 04:04 PM   #107
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is this internally gated or externally?
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Old 02-20-2012, 05:07 PM   #108
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2560 teacup turbo only comes intenal gate nuka
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Old 02-22-2012, 01:03 AM   #109
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Here goes:

red- 3" downpipe into 2.5" stock exhaust....tuned
blue- 3" downpipe into 3" free flowing exhaust.....untuned (or more specifically using the previous "red line" tune)


Pretty hefty difference
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100% of the power. 0% of the sound. Winning-vladforesterdownpipevsfullexhaust.jpg  
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Old 02-22-2012, 10:09 AM   #110
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Here's my personal car:



Same boost, same setup. The only difference was replacing my MAX5 cat and 2.25" borla dual with a 2.75" -> 3" test pipe and 3" enthuza exhaust and mild DIY head porting.

Tune was obviously different, but the spark timing was the same IIRC.


Here's a small SR20 T25 1.6L setup with the same borla duals:




Now look at a very simlar 1.8L setup running only 10psi with the same sr20 t25 but a 3" enthuza exhaust [red]:



Notice the spool/tq difference?
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100% of the power. 0% of the sound. Winning-scott_beforeafter.jpg   100% of the power. 0% of the sound. Winning-samnavy_197.jpg  
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Old 02-22-2012, 12:22 PM   #111
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Man, I need to put on my 3" downpipe and tune my FXT...
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Old 02-22-2012, 12:43 PM   #112
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Mine's a 2.25 to 2.75" DP IIRC I forget. I believe the SR20 T25 setups are the same; all BEGi parts.

But I gained roughly 1000rpm in spool removing the awful 2.25" catback. The muffler was single 2.25" in and dual 2.0" out...not sure what effect that had on it.

So if anything I'd want a cutout, that opened fully at the first notion of getting into boost. Which for my setup could mean 5% throttle on the highway. I can boost out of my driveway for god's sake. This all defeats the purpose of trying to keep exhaust noise to a minimum.
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Old 02-22-2012, 12:46 PM   #113
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Quote:
Originally Posted by Braineack View Post
Here's my personal car:

...

Notice the spool/tq difference?
The difference is significant.
But this begs the question: when did each of these setups reach, say, 5psi when the cutout would open? I'm pretty sure its well before peak toruqe, but maybe I'm wrong.

Also on that last one, are you comparing a 2871(blue) to 2560(red) or is it the same turbo both times?
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Old 02-22-2012, 12:48 PM   #114
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The last chart, in red, is a sr20 t25 on a begi manifold/dp running 10psi with a 3" exhaust. You should compare that to the 1.6L motor above running that same 2.25" catback I was. Look how long it took to reach 14psi.

I guess if you had some sort of 3-5psi dump it would help, but it will still suffer and torque would then raise exponetially once open--along with dBs.
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Old 02-22-2012, 01:23 PM   #115
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Yeah pretty much. It would stretch that vacuum-to-4psi transition from say 200rpm to like 300 or 400 possibly. Then open up and shoot back up to whatever it would have been with 3"
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Old 02-22-2012, 02:37 PM   #116
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Actual spoolup difference, with my flapper valve wired open vs. normal.
https://www.miataturbo.net/showpost....&postcount=44:



3rd gear on a 6 speed. Blue is wired open. Difference is <100 ms. And I opted for the stiffer option for the spring (opens later)
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Old 02-22-2012, 02:55 PM   #117
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So you're basically arguing the exact opposite of Sav and Brainy: the 0-4psi transition is not long at all

I'll have to dig up my old 3076r MLV boost plot when I was 3" dp+stock exhaust. I believe full boost was achieved by 4500 or something like that. Now I'm wondering how long it took for it to go from vacuum to 4psi.
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Old 02-22-2012, 04:20 PM   #118
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Quote:
Originally Posted by 18psi View Post
So you're basically arguing the exact opposite of Sav and Brainy: the 0-4psi transition is not long at all

I'll have to dig up my old 3076r MLV boost plot when I was 3" dp+stock exhaust. I believe full boost was achieved by 4500 or something like that. Now I'm wondering how long it took for it to go from vacuum to 4psi.
If you do a cutout or bigass wastegate (better idea IMO) you should have a full length 2" exhaust

and

Bigass shortie "dump tube" as close to turbine exit as possible. That way you have minimum backpressure and max spoolage.

Also email me your map anyways! I want to take a look.
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Old 02-22-2012, 04:22 PM   #119
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BTW:

Why not just use tiny exhaust and compensate by:

running VVT head ($250 in classifieds)
upgrade oil pump $300
valve springs $300
intake of some decent sort $300

And then rev to 8000RPM. So what if boost onset is greater, you will have the same width powerband and will hold power to redline.
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Old 02-22-2012, 04:31 PM   #120
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Quote:
Originally Posted by JasonC SBB View Post
Actual spoolup difference, with my flapper valve wired open vs. normal.
https://www.miataturbo.net/showpost....&postcount=44:

do the same with say a 2" restrictor plate on the tailpipe.
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