I just accidentally ALL OVER MY PANTS from bmw's N55 now must tiny twin scroll
03-10-2011, 06:22 PM
#21
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Completely defeats the purpose of twin-scroll. You end up with cross-contamination from the pulses and you lose the divided effect. There's a good reason that real twinscroll manifolds (i.e. Full-Race) have two EWG hookups.
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03-10-2011, 06:26 PM
#22
You have read correctly. You bolded my version of the quote, which is what "should have been" written. In both scenarios, we're comparing the GTA wheel with the inconel wheel, the only difference is, the original quote gives no baseline for comparison.
Now, that being said, we understand what "the new part is over 50% lighter than the old part" means; but it's mathematically incorrect - try solving for the weight of the new wheel mathematically using only the information provided in this statement, understand that you must multiply the difference between two quantities (some unknown quantity - the weight of the old wheel) by 1.5 in order to solve it.
I know I'm only confusing the matter more by editing with following information, but:
q = some unknown quantity
o = weight of old wheel
n = weight of new wheel
q-n = (q-o)1.5
assume o = 100
q-n = (q-100)1.5
assume Q = 110
110 - n = (110 -100)1.5
110 - n = 15
-n = 15-110
n = 110-15
n=95
New wheel = 95g, 50% lighter than old wheel relative to 110
Assume Q = 200
200 - n = (200 -100)1.5
200 - n = 150
50 = n
new wheel is 50g, 50% lighter than 100g relative to 200g
Assume Q = 50
50 - n = (50 - 100) 1.5
50 - n = -75
125 = n
new wheel is 125g, 50% lighter than 100g relative to 50g
The problem is: "Q" is a mathematically undefined variable in the original quote.
Now, that being said, we understand what "the new part is over 50% lighter than the old part" means; but it's mathematically incorrect - try solving for the weight of the new wheel mathematically using only the information provided in this statement, understand that you must multiply the difference between two quantities (some unknown quantity - the weight of the old wheel) by 1.5 in order to solve it.
I know I'm only confusing the matter more by editing with following information, but:
q = some unknown quantity
o = weight of old wheel
n = weight of new wheel
q-n = (q-o)1.5
assume o = 100
q-n = (q-100)1.5
assume Q = 110
110 - n = (110 -100)1.5
110 - n = 15
-n = 15-110
n = 110-15
n=95
New wheel = 95g, 50% lighter than old wheel relative to 110
Assume Q = 200
200 - n = (200 -100)1.5
200 - n = 150
50 = n
new wheel is 50g, 50% lighter than 100g relative to 200g
Assume Q = 50
50 - n = (50 - 100) 1.5
50 - n = -75
125 = n
new wheel is 125g, 50% lighter than 100g relative to 50g
The problem is: "Q" is a mathematically undefined variable in the original quote.
TL;DR: over 50% ligher than != less than 50% of the weight of.
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03-10-2011, 06:29 PM
#23
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The 997TT is all electronic - it uses the vanes for response and overall boost control. You could do pneumatic control pretty easily, though. I wonder if EGT/abuse is still a concern for high performance aftermarket use?
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03-10-2011, 06:33 PM
#24
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Come on, guys. It's implied that they are referring to the Garrett Inco wheel when they say "50% lighter". Kind of like how your stock portfolio goes up 10% a year - it's not 10% relative to the GDP of China, it's relative to your portfolio.
It's not hard to figure out what they meant, especially when you look up the mass of GammaTi vs. Inconel.
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03-10-2011, 11:21 PM
#27
Sav's on point here re: twin scroll and VNT. One correction, the BMW and Mitsu internal wg draws from both scrolls, not just one. They're done right.
EFR looks really nice. Hope they hit the ground soon. Turbine housings look nice. Ti-Al wheel is its single biggest perf benefit. Curious about the wheels' heat tolerance though.
Porsche's is the only VNT capable of handling gasoline EGTs. That, and the Garrett motorsports VNT on the Audi R15 LeMans car, but that's pretty much unobtanium. Borg sells the Porsche VNT in the aftermarket though...
Many/most VNTs use a rotary electric actuator for vane position control.
EFR looks really nice. Hope they hit the ground soon. Turbine housings look nice. Ti-Al wheel is its single biggest perf benefit. Curious about the wheels' heat tolerance though.
Porsche's is the only VNT capable of handling gasoline EGTs. That, and the Garrett motorsports VNT on the Audi R15 LeMans car, but that's pretty much unobtanium. Borg sells the Porsche VNT in the aftermarket though...
Many/most VNTs use a rotary electric actuator for vane position control.
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03-10-2011, 11:58 PM
#30
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Is the benefit of dual-scroll from the scavenging or from effectively a more efficient turbine?
If the former, I don't get it, don't you get the same benefit from longer manifold runners? IOW, the gas pulses mix in the turbine blades, so the pulses are kept separate only for the additional length of time it takes to go through the turbine:
If the former, I don't get it, don't you get the same benefit from longer manifold runners? IOW, the gas pulses mix in the turbine blades, so the pulses are kept separate only for the additional length of time it takes to go through the turbine:
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03-11-2011, 01:21 AM
#31
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Is the benefit of dual-scroll from the scavenging or from effectively a more efficient turbine?
If the former, I don't get it, don't you get the same benefit from longer manifold runners? IOW, the gas pulses mix in the turbine blades, so the pulses are kept separate only for the additional length of time it takes to go through the turbine:
If the former, I don't get it, don't you get the same benefit from longer manifold runners? IOW, the gas pulses mix in the turbine blades, so the pulses are kept separate only for the additional length of time it takes to go through the turbine:
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03-11-2011, 01:50 AM
#33
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edit- It's really a more efficient turbine housing and manifold design that gets the pressure to the turbine better instead of allowing it to restrict flow in the manifold.
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03-11-2011, 02:31 AM
#34
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but you can get away with using a more common alloy as a wall that's just clearanced far enough from the valve? Realistically, even though I realize your post was just saying it can be done, it seems safer and more effective in terms of both cost and performance to just run two wastegates.
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03-11-2011, 11:01 AM
#35
http://forum.diyefi.org/viewtopic.ph...&t=199&start=0
I shouldn't have said 'sophisticated' as its just a servo, however it seems that there are a lot of variables that go into controlling it. i.e. it isn't just boost pressure. EGT/AFR/Throttle position/etc are all accounted for in the factory system from what I've gathered.
I'm really thinking about running one of these on my 320i as I have access to one locally for pennies (if I can fit the bastard between my frame and block
). My thoughts were to remove the stock control system and replace it with a standard internal gate actuator ala aerocharger. I was thinking that if it were supplemented with an external WG and plumbed both of them together behind a boost control solenoid controlled by the MS2, the results could be rather nice.
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03-11-2011, 11:56 AM
#36
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http://www.superturbodiesel.com/std/...tronic-control
http://forum.diyefi.org/viewtopic.ph...&t=199&start=0
I shouldn't have said 'sophisticated' as its just a servo, however it seems that there are a lot of variables that go into controlling it. i.e. it isn't just boost pressure. EGT/AFR/Throttle position/etc are all accounted for in the factory system from what I've gathered.
http://forum.diyefi.org/viewtopic.ph...&t=199&start=0
I shouldn't have said 'sophisticated' as its just a servo, however it seems that there are a lot of variables that go into controlling it. i.e. it isn't just boost pressure. EGT/AFR/Throttle position/etc are all accounted for in the factory system from what I've gathered.
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