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Old 03-10-2011, 05:10 AM   #1
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Default I just accidentally ALL OVER MY PANTS from bmw's N55 now must tiny twin scroll

In addition to Valvetronic, Direct Injection, and a map controlled oil pump, BMW's N55 (which im just now reading about) also has this:


My goal is to have 300+whp and the most immediate response possible. Engine's at builder's with 84.5mm Wiseco's, M-tuned rods from 949, and ACL Race bearings, but I'll be using a 3" exhaust, VVT head, +1mm valves (good/bad idea for the street? exhaust only?), and attempting to copy hf-mx5t's dual plenum intake :3

I'm thinking GT2860RS and this ATP twin scroll housing. I'm curious as to how exactly I should go about this though.

Option 1) Cylinders 1&4 are divided to one scroll and 2&3 to the other. *oops, had that mixed up at first...

Option 2) All cylinders feed together undivided into the flange, but there is a "quick spool valve" which blocks one scroll until it needs to open.

Option 1.5+) Design a setup which all goes into one scroll and then divides 1&4 from 2&3 when the 2nd scroll opens.

Option 3) STFU and get a TiAL full v-band housing because that ATP **** is going to break as soon as you take it on the track; your bitchboy turbo will be plenty responsive anyway.

I'm not concerned if the "QSV" will be smooth, because I can always just set up something to open it if needed for track driving etc.

What do you guys think? (i feel like i will see a lot of option 3 "suggestions"...)

BTW, even though the off/on throttle response I'm after can't be shown on a dyno here's a chart from a "62mm billet GT35r(.84 T4 turbine) on stock 7MGTE [3.0L inline 6] with SAFC on stock ECU" w/ a QSV

Last edited by NickC; 03-10-2011 at 03:49 PM.
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Old 03-10-2011, 06:45 AM   #2
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Forget about the QSV. They grenade under track abuse.

300whp and response-minded? You should really press the pause button until a couple of people get EFR6258 setups together.
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Old 03-10-2011, 07:18 AM   #3
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back to life, back to reality
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Old 03-10-2011, 09:21 AM   #4
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I've been thinking about something similar but with a proper 1&4, 2&3 twinscroll manifold (option 4?). I thought about making my own QSV but like Andrew said I'd be weary of it grenading into my turbine. You can ask ATP if they have this turbine in GT28XX for a little less money:
http://www.atpturbo.com/mm5/merchant...egory_Code=GTH

Your 3 options could apply to the BW EFR turbos with their divorced turbine options.
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Old 03-10-2011, 01:27 PM   #5
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What's a QSV?

Why would you want "on/off" throttle response (if I'm understanding you right)

Pairing should be 1&4 and 2&3 as TurboTim implied, not 1&2 and 3&4.


---------------
Now what's the theory why twin-scroll turbines improve spool?
Until what point do the gas paths remain separate?


Response and power - have the VNT and variable vane turbos not moved on yet and become more reliable?
I don't see how BW can improve on wheel aero to challenge VNT/VV in terms of the spool/flow tradeoff.
Why haven't Honeywell released a complete line of VNT and VV turbos to the aftermarket? Maybe if BW are enough of a threat they finally will.
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Old 03-10-2011, 01:32 PM   #6
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Quote:
Originally Posted by JasonC SBB View Post
What's a QSV?
quick spool valve


mostly found on supras with small animal/baby eater turbos.. supposedly helps spool the turbo up faster.. one dyno i saw showed the power came on 700 rpms sooner with it..
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Old 03-10-2011, 01:34 PM   #7
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QSV = Quick Spool Valve - basically a plate with a flapper that you stick between the twinscroll turbo and the single-scroll manifold. When it's closed you get half the A/R you normally would, which means faster spool. Until it just comes apart and ruins the turbo.

Quote:
Originally Posted by JasonC SBB View Post
Now what's the theory why twin-scroll turbines improve spool?
Until what point do the gas paths remain separate?
Exhaust gas pulse separation. They remain separate until they touch the turbine wheel, ideally - a good twinscroll setup uses two external/internal wastegates so the chambers remain totally separate. (Or janky ones like BMW/Mitsubishi use a single internal gate on one half of the twinscroll.)

With single-scroll, you reach a point where the exhaust pulses arrive right on top of each other, and their effect is essentially negated. With twinscroll that point is moved way up in the RPM range since you're only trying to stack two pulses vs. stacking 4.

Once you spin the motor up high enough, the benefit goes away, but the low end benefit is enormous - typically you run a much larger turbine A/R to pick up some flow up top, while still getting good spool via the twinscroll housing. Borg will do a .83 A/R single-scroll turbine or a .92 A/R twin-scroll turbine, and I'd bet money that the .92 TS would spool faster.

Jason, I bet the hurdle for VNT is control. How many of Garrett's customers have an ECU that will control a VNT setup? How many of them are using reflashed Honda/Suby/Mitsu ECUs?

You should read up on the new titanium aluminide exhaust wheels that BW is using - crazy, crazy stuff.
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Old 03-10-2011, 01:34 PM   #8
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double post fail
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Old 03-10-2011, 02:13 PM   #9
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I don't tjink a qsv applies to track use eitehr becuase unless you drive the whole track in 6th gear you will always be above boost threshhold.

My guess is garrett has no afgtermarket VNT because not enuff ppl would buy em becus of complexity.

OP just get a 2871 .63 or a uh .4 T2 3071 and be happy. Actually if 2876 came with a .4 housing and T2 I soulx get that because baby turbines and huge compressors are awesome.
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Old 03-10-2011, 02:58 PM   #10
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Why not just build a good twin scroll mani with 1,3 and 2,4 hooked together with a equalizer pipe to make sure both sides of the mani have even pressure and run your waste-gate off of the equalizer pipe. This will still spool the **** out of a turbo simplify your set up and run with it. If not just run a single scroll mani and deal with it. My experience with a quick spool is one on track cars they blow up two you only need one if you are running some huge huge turbo as in if you have a gt42R with a 1.1 a/r exhaust then yea it would be a good idea for what you want just run with it. SIMPLE is better in all cases.
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Old 03-10-2011, 03:03 PM   #11
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Love this thread. I've been wanting some chatter on these subjects. Also, is the theory behind a QSP similar to an inline twin turbo setup?
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Old 03-10-2011, 03:15 PM   #12
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Yes the QSV is similar to that in a way but not at all in other ways. They hit the market big time on supra's trying to run massive turbos and they work well on street cars but people think hey that guy ran it on his street car for 5 years it will work on my track car. Difference is that the abuse most street cars especially supra's see in a year is equal to what most track cars do in a couple full speed laps. There is a reason you can build a turbo kit for the street for $1000 and get away with it and almost every track car has that in a turbo alone.
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Old 03-10-2011, 03:36 PM   #13
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Quote:
Originally Posted by Savington View Post
Forget about the QSV. They grenade under track abuse.

300whp and response-minded? You should really press the pause button until a couple of people get EFR6258 setups together.
I had a feeling that little piece of stainless would eventually end up in the turbine, maannn... Oh well, the divided setup seems more pr0 anyway.

The EFR6258 looks perfect though! Slightly smaller turbine, slightly larger compressor wheel, and a higher A/R with twin scroll + hybrid ceramic bearings and it appears to just simply be superior in construction too. My only concern is, and this maybe just from reading this forum too much, will I be alright on track without v-bands? I'm assuming BW housing is higher quality and warps less?

Quote:
Originally Posted by JasonC SBB View Post
What's a QSV?

Why would you want "on/off" throttle response (if I'm understanding you right)

Pairing should be 1&4 and 2&3 as TurboTim implied, not 1&2 and 3&4.


---------------
Now what's the theory why twin-scroll turbines improve spool?
Until what point do the gas paths remain separate?


Response and power - have the VNT and variable vane turbos not moved on yet and become more reliable?
I don't see how BW can improve on wheel aero to challenge VNT/VV in terms of the spool/flow tradeoff.
Why haven't Honeywell released a complete line of VNT and VV turbos to the aftermarket? Maybe if BW are enough of a threat they finally will.
Oh right, that makes sense since the firing order is 1-3-4-2 and the point of the twin scroll is to separate interfering exhaust gas pulses. late night assumption, heh...

I said "off/on" (ha, if that makes a difference?) in reference to the "lag" I guess attempting to differentiate between the when (at what rpm) the turbo starts making power under a full throttle condition as opposed to getting on the gas mid-corner. I think I made it more confusing, but the terms kind of blend together sometimes. Essentially, I'm referring to the throttle response that's so good with N/A or supercharged in comparison to the slower response of a turbo setup and trying to minimize that.

I'm interested in VNT/VV, it looks like it's still more of an OEM thing though possibly due to cost of making it a reliable setup and only having enough market by supplying it as an OEM product. Even though there are plenty of people doing aftermarket turbos, I don't think there would be enough demand because they'd be pricey and as Sav was saying, most people wouldn't be able to control them without having a capable standalone or some auxiliary form of control which would make them even more costly.

The "Gamma Titanium Aluminide" wheel of the new EFR series is "over 50% lighter than its inconel counterpart". so awesome.
I think this, coupled with a twin scroll housing, hybrid ceramic bearings, and proper manifold will be very responsive.
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Old 03-10-2011, 05:45 PM   #14
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Quote:
Originally Posted by NickC View Post
The "Gamma Titanium Aluminide" wheel of the new EFR series is "over 50% lighter than its inconel counterpart". so awesome.
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Old 03-10-2011, 06:10 PM   #15
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Sav:

AFAIK VNT control is still pneumatic - IOW they still use the same wastegate actuators our "normal" turbos use.
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Old 03-10-2011, 06:23 PM   #16
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Quote:
Originally Posted by JasonC SBB View Post
Sav:

AFAIK VNT control is still pneumatic - IOW they still use the same wastegate actuators our "normal" turbos use.
The Holset he351VE uses a fairly sophisticated servo based system to control its VNT functionality.

Last edited by Jeff_Ciesielski; 03-10-2011 at 06:23 PM. Reason: Edited to not sound like a dick.
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Old 03-10-2011, 06:37 PM   #17
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Quote:
Originally Posted by Some non-engineer in the marketing department
The "Gamma Titanium Aluminide" wheel of the new EFR series is "over 50% lighter than its inconel counterpart"
lighter relative to what? relative to the moon? relative to the equivalent garret turbine housing?

Had this been "The 'Gamma Titanium Aluminide' wheel of the new EFR series is 'less than 50% of the weight of its inconel counterpart'", then we assume you mean less than 50% of its weight relative to zero, or "less than half"

Hypothetical examples:

a. Turbine wheel = 50 grams
"Over 50% lighter relative to 51 grams" = new wheel < 49.5 grams.
"Over 50% lighter relative to 60 grams" = new wheel < 45 grams.
"Over 50% lighter relative to 100 grams" = new wheel < 25 grams.
"Over 50% lighter" = Mathematically meaningless.
"Over 50% lighter relative to 40 grams" = >55 grams. (WTF!? IT GOT HEAVIER!! the 50g turbine wheel relative to 40 grams is -10g (negative 10) lighter than 40g. If we mulitply the difference by 1.5 (thus increasing the relative "lightness" by 50%) the new difference, relative to 40 grams is "-15g lighter" "OMG!")
"Less than 50% as heavy" = Weighs half as much relative to no weight

I worked in camera sales briefly, and when my co-workers said "the 10x zoom makes things look like they're 10 times closer" I was tempted to strangle them.(because mathematically, this is meaningless, does the object appear 10 times closer relative to the moon, or 10 times closer relative to that car 1 mile away?.....10 times closer relative to something that was between the object and the viewer would actually make it look farther away than it actually is.) To be mathematically correct, a 10x zoom makes things look like they're "1/10th as far away" (because that is relative to the actual distance of the object being viewed)

/off-topic rant

Last edited by fooger03; 03-10-2011 at 06:49 PM.
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Old 03-10-2011, 06:56 PM   #18
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Quote:
Originally Posted by fooger03 View Post
lighter relative to what? relative to the moon? relative to the equivalent garret turbine housing?

Had this been "The 'Gamma Titanium Aluminide' wheel of the new EFR series is 'less than 50% of the weight of its inconel counterpart'", then we assume you mean less than 50% of its weight relative to zero, or "less than half"

Hypothetical examples:

a. Turbine wheel = 50 grams
"Over 50% lighter relative to 51 grams" = new wheel < 49.5 grams.
"Over 50% lighter relative to 60 grams" = new wheel < 45 grams.
"Over 50% lighter relative to 100 grams" = new wheel < 25 grams.
"Over 50% lighter" = Mathematically meaningless.
"Over 50% lighter relative to 40 grams" = >55 grams. (WTF!? IT GOT HEAVIER!! the 50g turbine wheel relative to 40 grams is -10g (negative 10) lighter than 40g. If we mulitply the difference by 1.5 (thus increasing the relative "lightness" by 50%) the new difference, relative to 40 grams is "-15g lighter" "OMG!")
"Less than 50% as heavy" = Weighs half as much relative to no weight

I worked in camera sales briefly, and when my co-workers said "the 10x zoom makes things look like they're 10 times closer" I was tempted to strangle them.(because mathematically, this is meaningless, does the object appear 10 times closer relative to the moon, or 10 times closer relative to that car 1 mile away?.....10 times closer relative to something that was between the object and the viewer would actually make it look farther away than it actually is.) To be mathematically correct, a 10x zoom makes things look like they're "1/10th as far away" (because that is relative to the actual distance of the object being viewed)

/off-topic rant
I'm not sure which one of us is retarded so I've bolded the relevant statement here. If I can read correctly, it is comparing the weight of the advertised wheel to the weight of the inconel version of the exact same wheel.

Have I been huffing too much glue today?
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Old 03-10-2011, 07:08 PM   #19
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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.

Last edited by fooger03; 03-10-2011 at 07:22 PM.
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Old 03-10-2011, 07:09 PM   #20
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Quote:
Originally Posted by fooger03 View Post
lighter relative to what? relative to the moon? relative to the equivalent garret turbine housing?

Had this been "The 'Gamma Titanium Aluminide' wheel of the new EFR series is 'less than 50% of the weight of its inconel counterpart'", then we assume you mean less than 50% of its weight relative to zero, or "less than half"
haha, yeah, I hate lack of actual quantification as opposed to random numbers, which is why I left it in quotes =P however, I checked some numbers like I shold have before and:

Densities:
Gamma TiAl 4.0g/cm³
Inconel 8.14g/cm³


btw, I alt + 0179'd those ^3s instead of copy and paste B) aw yeeeee
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