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DIY Turbo Discussion greddy on a 1.8? homebrew kit?

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Old 02-19-2009, 01:34 AM   #41
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420fwhp/350whp

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Old 02-19-2009, 01:35 AM   #42
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WTF none of my images are working... Can anyone see them? I've posted 4, but I only see 1.
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Old 02-19-2009, 01:38 AM   #43
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When i put in my numbers, It tells me that i'm going to need 63psi to get my power goal. Maybe i'm doing it wrong.

According to garrett's website, here is their calculation.

Where:

MAPreq = Manifold Absolute Pressure (psia) required to meet the horsepower target
Wa = Airflowactual(lb/min)
R = Gas Constant = 639.6
Tm = Intake Manifold Temperature (degrees F)
VE = Volumetric Efficiency
N = Engine speed (RPM)
Vd = engine displacement (Cubic Inches, convert from liters to CI by multiplying by 61.02, ex. 2.0 liters * 61.02 = 122 CI)

If i do the math, that comes out to 48.1 total psi or 33.4 psi of boost. That doesnt seem quite right either. Pretty sure my ****'s going to pop if i try and put 33psi to it with any turbo. Am i missing part of the equation here?
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Old 02-19-2009, 01:38 AM   #44
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No idea, but anyways, at 350whp it's perfect/maxed. Anything more it goes to **** fast.
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Old 02-19-2009, 01:39 AM   #45
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i only see one.
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Old 02-19-2009, 01:42 AM   #46
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Old 02-19-2009, 01:46 AM   #47
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Quote:
Originally Posted by wes65 View Post
When i put in my numbers, It tells me that i'm going to need 63psi to get my power goal. Maybe i'm doing it wrong.

According to garrett's website, here is their calculation.

Where:

MAPreq = Manifold Absolute Pressure (psia) required to meet the horsepower target
Wa = Airflowactual(lb/min)
R = Gas Constant = 639.6
Tm = Intake Manifold Temperature (degrees F)
VE = Volumetric Efficiency
N = Engine speed (RPM)
Vd = engine displacement (Cubic Inches, convert from liters to CI by multiplying by 61.02, ex. 2.0 liters * 61.02 = 122 CI)

If i do the math, that comes out to 48.1 total psi or 33.4 psi of boost. That doesnt seem quite right either. Pretty sure my ****'s going to pop if i try and put 33psi to it with any turbo. Am i missing part of the equation here?

Yeah, some of your numbers were wrong. I copied what I was running, (max power at 7500, full boost 4k, etc) and kept flywheel hp to 430 (357whp) and got this: (24.5 PSI Boost BTW)

Squirrel Performance - Turbo Calculator Version 4

Turbo ain't big enough for 350whp


Same turbo at 380fwhp/315whp
http://www.squirrelpf.com/turbocalc/...&product_id=32

Bout all it's good for.
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Old 02-19-2009, 01:48 AM   #48
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Squirrel Performance - Turbo Calculator Version 4

Looks like 2876 is pretty close to what i need?
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Old 02-19-2009, 01:48 AM   #49
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Quote:
Originally Posted by patsmx5 View Post
Yeah, some of your numbers were wrong. I copied what I was running, (max power at 7500, full boost 4k, etc) and kept flywheel hp to 430 (357whp) and got this: (24.5 PSI Boost BTW)

Squirrel Performance - Turbo Calculator Version 4

Turbo ain't big enough for 350whp
You chose the 2860, i was talking about the 2876
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Old 02-19-2009, 01:54 AM   #50
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You're to the left of the surge line with the 2876. That won't work....You'd be running 28 PSI and surging a lot. And your original link up there had the 2860 selected, that's why I used it.
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Old 02-19-2009, 01:58 AM   #51
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Quote:
Originally Posted by patsmx5 View Post
You're to the left of the surge line with the 2876. That won't work....You'd be running 28 PSI and surging a lot. And your original link up there had the 2860 selected, that's why I used it.
Maybe something an anti-surge housing would fix?
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Old 02-19-2009, 02:04 AM   #52
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At this point, I am at a bit of a loss. I mean, i could always go with a 16g. lol......
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Old 02-19-2009, 02:08 AM   #53
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There'ya go.
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Old 02-19-2009, 02:12 AM   #54
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I would like to go with a turbo that's easy to get ahold of. This is close. I'm still riding that surge line, however.
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Old 02-19-2009, 02:17 AM   #55
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Quote:
Originally Posted by wes65 View Post
I would like to go with a turbo that's easy to get ahold of. This is close. I'm still riding that surge line, however.
lol. Scroll down and select GT3271 with those numbers and have a look. If you could settle for 350whp, the GT3271 ain't bad.

Part of the "problem" is spool. If you build boost at low RPMs, there's low flow, and you surge. You could "fix" this problem with a shitty wastegate and manifold so that you didn't get full boost till say 4500 and say boost onset at 2500 (note they use a linear rise in boost, where in my experience, it's not linear, but exponential).
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Old 02-19-2009, 10:31 AM   #56
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Quote:
Originally Posted by patsmx5 View Post
lol. Scroll down and select GT3271 with those numbers and have a look. If you could settle for 350whp, the GT3271 ain't bad.

Part of the "problem" is spool. If you build boost at low RPMs, there's low flow, and you surge. You could "fix" this problem with a shitty wastegate and manifold so that you didn't get full boost till say 4500 and say boost onset at 2500 (note they use a linear rise in boost, where in my experience, it's not linear, but exponential).
I really dont want to settle. I WILL make 400whp one way or another. Even if i blow this one up, i have another motor sitting in my closet waiting to be built.

Quote:
Originally Posted by JKav View Post
You've never seen a failed thrust bearing?

Race cars that don't use anti-surge valves get their turbos rebuilt every other race. Or so.

ZX, the 2871 sans ported shroud will surge on a 2.0-liter WRX, so I fully expect it to surge on your 1.8.
I'm thinking with a turbo that is slighty off to the left, i can use an anti surge housing.
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Old 02-19-2009, 11:08 AM   #57
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Looks like newbsauce is using this turbo. 4300ish for full spool. Not terrible.
https://www.miataturbo.net/forum/t26984/
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Old 02-19-2009, 11:17 AM   #58
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the 2876 wont spool as early as your simulation suggests unless you're running VVT for high and low end.

Here's roughly how it does on a non vvt optimized setup:


that said, maybe we can swap your 2860 for my 2876 (chra + comp hsg) and play around
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Old 02-19-2009, 11:20 AM   #59
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Quote:
Originally Posted by y8s View Post
the 2876 wont spool as early as your simulation suggests unless you're running VVT for high and low end.

Here's roughly how it does on a non vvt optimized setup:


that said, maybe we can swap your 2860 for my 2876 (chra + comp hsg) and play around
Interesting. Do you have any problems with the turbo surging as you spool?
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Old 02-19-2009, 03:57 PM   #60
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Quote:
Originally Posted by wes65 View Post
Interesting. Do you have any problems with the turbo surging as you spool?
Probably no surge at 7 PSI. But 28....
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