Twin-Scroll GT28's?

[KA240SX808]

I don't know if anyone seen this (http://www.atpturbo.com/mm5/merchant.mvc?Screen=PROD&Store_Code=tp&Product_Code=ATP-HSG-102&Category_Code=GTH) but Garrett has come out with a T3 Twin-Scroll Turbine Housing for the GT2860RS, GT2871R, and the GT2876R. Was wondering if any one had thought's on how it would spool compared to the normal T2 housing it comes with.

[Epstein]

This is just the same T3 flange .82ar (divided) housing that they've had for years, except that it's built to suit the smaller 53.85mm turbine instead of the 307x's 60mm or the 3582's 68mm turbine.

I had a 3071 with the .78ar divided housing, previously. This turbo has a 60mm turbine. A 2871 with a .82ar divided housing would have a smaller (53.8mm) turbine in a larger housing. Ignoring trims and blade geometry, this is the recipe for spooling slower. I think the 2860 would be neat. You can't get the 60mm compressor on a T3 flange with a decent housing, that I know of. On a KA that is setup for only 350whp, this would be a neat turbo. The problem is, I don't think "twinscroll, GT turbo, KA-T, $$$" intersects with "planned 350whp max".

[turtl631]

It could for an autocross setup where spool trumps max power to some extent.

[SM240]

Seems a bit redundant to me. The whole idea is to help spool time.....how much more spool is needed in a t2 based turbo? I mean really sounds like theres a minimal difference. Maybe on a larger housing I can expect some gains, but seems to me like Id spend the money to have a turbo thatll spool fast and have excellent top end power like a 3071-76.02

[Geno]

Agreed. I think money would be better spend just doing an extrude hone on the manifold and t2 housing than getting a top mount setup. Especially since the extrude hone would cost less than the pair of external wastegates you'd need.

[PoorMans180SX]

Digging this thread back up.

I am not concerned with the top-end power, I am looking for the quickest spool possible from a T28-sized turbo.

I know a .78 twin-scroll 3071 will spool up faster than a .63 2871r, but this seems like an odd combination. Will this give faster spool, or just equal spool with more top-end flow on a 2860rs? Either way it could fit into my plans pretty well, but I was just looking for some more information.

and why at the bottom does it say it was designed for a 56.5mm wheel?

[Def]

I don't think the small spool difference is enough to justify the cost for 99% of the builds I've seen.

Honestly, I don't think going to a T3 manifold makes sense on an SR unless you want over 400 rwhp, which pretty much means GT3076R IMO.

[PoorMans180SX]

Well you see, I would be pairing this with a 3076r, or maybe something a little bigger even. :D

V-band outlet is much better for this as well.

So it would be a small spool gain as well as increased flow?

I just PM'd 240sxTTC.

[CodyAce]

I don't think the small spool difference is enough to justify the cost for 99% of the builds I've seen.

Honestly, I don't think going to a T3 manifold makes sense on an SR unless you want over 400 rwhp, which pretty much means GT3076R IMO.


Let it be known that a 400 whp T2 2871r s14, is also quicker than a 435 whp 3071r car. 'just saying'

If you really want to make big power, you gotta go with something that makes 450 whp or more with a 30r based setup...anything less will not out run a T2 car at 400.

[PoorMans180SX]

Well since I plan on making over 450whp with quicker spool than a 2871r...

I don't think it's going to be a problem.

[Def]

On a big turbo build I think the .7x a/r twin scroll housing starts making sense. A bit more power than a .63 housing, and probably equal spool if not a hair better. The extra cost isn't a huge deal then.

I guess my other post was centering on the fact that I don't understand the appeal of a 3071r twin scroll setup when you can get 90-95% the results with a bolt on 2871r.

[Equinox]

Has anyone seen these? They'd probably be a good cost-effective upgrade for an SR20

http://bit.ly/daka5G

They're an internal gate, bolt-on GT3071R or 76R, twin-scroll low mount for the Evo X and are available off the shelf from Garrett. Ignore the price in the link; I'm sure that has your typical Aussie supplier's 70% markup on it. Probably a lot cheaper from Garrett.

[PoorMans180SX]

Might as well get an external gate if you're going with a custom manifold.

[Def]

Has anyone seen these? They'd probably be a good cost-effective upgrade for an SR20

http://bit.ly/daka5G

They're an internal gate, bolt-on GT3071R or 76R, twin-scroll low mount for the Evo X and are available off the shelf from Garrett. Ignore the price in the link; I'm sure that has your typical Aussie supplier's 70% markup on it. Probably a lot cheaper from Garrett.

ATPturbo.com has those in the T2 flanged turbos. Some people like 'em, some don't.

[KA240SX808]

I read alot about boost creep from those with the T2 Side. Even when the port the WG port it still creeps.

[juggernaut]

For comparison purposes this was one of my dyno runs with my .78 twin scroll 3076 (52 trim) showing boost. Ended up making peak 388rwhp and 240rwhp by 4000rpm - refer to intro/build section for final hp and torque.

Not sure whether you could get a 2871R spooling much better than this on normal pump fuel?

Points of interest:

boost graph in KPa!!!
starts making positive boost at approx 2300rpm
approx 21.6 psi by 3750
still runs VCT on intake cam
exhaust cam was deliberately retarded to bring low/mid rang torque on earlier.

http://i241.photobucket.com/albums/ff132/juggernaut000/Boost307652trim.jpg

[PoorMans180SX]

Yeah, I was mainly concerned with super quick spool. I'm not worried about top-end power. That will be taken care of other ways :D.

I've talked with 240sxTTC a little via PM, and he said that the twin-scroll t28 housing will most likely flow more, but probably have the same spool characteristics.

I'm probably just going to rock the GT2560. It should perform it's role admirably :).

[tonto]

nobodies curiosity has been piqued by a twin scroll 2871? i was thinking that might be an interesting new variable to play with. i even have a megan manifold i'd be willing to cut up to run a test. dunt have a housing tho....

maybe all of the things which make the 2871 work just get better with the ts housing?

[Rustspecs13]

Andy- Are you seriously thinking of the SR still? best bet is to get a extra s13 swapping it in and selling it. ;)

VQ30+ HE351 (aka holset hx40 with variable exhaust housing) = simpler more reliable setup. Stronger trans and not JDM too.

Keep in mind if you run much more then 25-30psi, you might need to o ring the head or something pretty crazy with an engine build.

I really think the fastest spooling stock SR turbo thats been rebuilt, or something thats stock ish size and maybe spools faster would work good. I do know my RB20 stock turbo out spooled my friends stock SR20, but thats because its a BB and ceramic exhaust wheel.

That and some piping and two waste gates would be fun till your aluminum block takes a vacation. :D

~Alex

[hai1206vn]

I do know my RB20 stock turbo out spooled my friends stock SR20, but thats because its a BB and ceramic exhaust wheel.
2 extra cylinders make a bit more exhaust to drive the turbo.

[PoorMans180SX]

Andy- Are you seriously thinking of the SR still? best bet is to get a extra s13 swapping it in and selling it. ;)

VQ30+ HE351 (aka holset hx40 with variable exhaust housing) = simpler more reliable setup. Stronger trans and not JDM too.

Haha, you always make me doubt my decisions!

Problem is, I need a track car, and a daily, and definitely can't have 3 cars right now. I don't have the space or time to be constantly fitting and tinkering with parts, and having the car down for any lengthy period of time; both of which I know I would have to do with the VQ. Someday.

Everything about the SR is basically drop in and go, and I can easily build an SR on the side to handle anything I'll be throwing at it. The VE head makes the rocker question mark go away. And there are simple solutions for stronger transmissions as well. Buy a kit, bolt on a VG trans, done.

So although it's not quite as cool, the SR will do for now. And I can gradually upgrade. GT2560 (S15 turbo) will be an easy step in the right direction.

[Def]

If you're buying new, get a .64 GT2871R. If used, a GT2560r is fine and pretty cheap.

I'd take an SR S13 over a FI VQ30 S13 any day of the week. Much more factory, more robust, lighter, and it'll make enough power to run with modded Vettes. Can't really ask for much more with a cheap import engine from the 90s. For track usage the stock trans seems strong enough.

[PoorMans180SX]

I would probably go with the 2871, except for the fact that this turbo will eventually be paired with something bigger in a compound setup, and it's primary purpose is spooling fast so as to get the other turbo online faster. Just a decent upgrade until then (which is far from now, haha). And yeah, I'll probably buy used.

[Equinox]

ATPturbo.com has those in the T2 flanged turbos. Some people like 'em, some don't.

You mean the ones with the chopped down 56.5mm HKS specification turbine stuffed into a T2 exhaust housing?

This one appears to be a full sized (60mm) GT3071R in a proper twin scroll exhaust housing.

Or is there another setup you're talking about that I'm missing? :P

[CodyAce]

Well since I plan on making over 450whp with quicker spool than a 2871r...

I don't think it's going to be a problem.


Faster, yet supportive? Only thing I an think of involves 8 cylinders and pushrods ;) Honestly though.




I'd take an SR S13 over a FI VQ30 S13 any day of the week. Much more factory, more robust, lighter, and it'll make enough power to run with modded Vettes. Can't really ask for much more with a cheap import engine from the 90s. For track usage the stock trans seems strong enough.

I wouldn't bother with all of the trouble of a forced induction vq30. If he's gonna swap that in, may as well put a GM LSx in there, and make real power, and be reliable.

[PoorMans180SX]

I will never, ever, have a LSx in my engine bay.

The car will get a built compound turbo SRVE, a legit Y33 VQ30DET build, or a VQ35 build.

Screw V8's and pushrods, I like my car without 490lbs of 1960's technology under the hood.

[e1_griego]

:popcorn:

[Def]

I would probably go with the 2871, except for the fact that this turbo will eventually be paired with something bigger in a compound setup, and it's primary purpose is spooling fast so as to get the other turbo online faster. Just a decent upgrade until then (which is far from now, haha). And yeah, I'll probably buy used.

A parallel or a serial setup? You could always sell the GT2871R if you want to run twin GT2560R's, but that's A LOT of turbo for our cars, and it'll be laggy for days upon days. A serial setup is retardedly hard to do, and you'd probably want something like a GT3076R on the "big" side.

[Def]

Faster, yet supportive? Only thing I an think of involves 8 cylinders and pushrods ;) Honestly though.






Meh, 450+ rwhp LS1s are supposedly just a few bolt-ons away, but they always seem to be very hard to find without someone that's spent about $6-8k on the motor. At least at the track where you have to work a bit harder to keep a motor making that much power happy.

The C5 Z06/C6 guys I talk to at the track are usually in the 390-440 rwhp range, but on the upper end of that they usually have everything but heads, and that's NOT cheap. $2500 long tube headers, $1k cam, intake mani, blah blah - it all adds up, and it's not cheap. Plus the lower end powerband starts sucking for as big a V8 as it is.

[Rustspecs13]

Def- no we are talking about a true Compound turbo setup.

http://i68.photobucket.com/albums/i17/paulvolk/DSCF0359.jpg

Thats a 2G dsm with a 16G and a t4 flanged 60-1. It puts down about 630whp- to almost 700whp, and makes 33psi at 3K.

The smaller turbo gets exhaust gas first, then feeds it into the larger second turbo, while fresh air goes into the larger turbo first then feeds BOOST into the SMALLER turbo (thats for other people, im sure they will skim and ask Q's any way) and then the smaller turbo feeds into the FMIC/engine.

That way the compressor flow is such that the smaller turbo runs its normal "PSI" aka pressure ratio range, and its happy and not being actually pushed that hard. The larger turbo runs completely normal.

On the exhaust side the smaller turbine isn't a restriction because its waste gate diverts any extra flow and keeps the turbo shaft speed and pressure in check like normal. That waste gate feeds back into the mid pipe that feeds the larger turbo exhaust side. Then it has its own turbo as well to control its boost just like normal.

http://www.youtube.com/watch?v=y-Me6yWApzY explains it pretty well except neither turbo is ever by passed, both work 100% of the time.

I plan on doing a compound setup on something, the rb20 I have, or get a CA18 or build a KA. Something.

But first I'm doing a VQ3X setup, na at first likely.

+1 on the "easy and cheap" 400-500-600whp LS1's I've always heard about. The way I figure it (and my bosses- I work at a rotary shop) it pretty much takes the same amount of money or work for any given HP level. Its just different depending on the engine. And I've seen and heard of real stories of plenty of LS1's blowing up under high G cornering due to oil issues. 6 of one half dozen another really.

Andy- I told you I'll have a VQ30 kit made to use the maxima ecu some time soon. Mounts, wiring, radiator piping, all that figured out. But I know its still not a normal swap. But cheaper motors for when you blow one, better sounding, no hassle USDM parts, etc etc etc.

~Alex

[PoorMans180SX]

Yeah, and I'm pretty sure the setup could be a bit more elegant than that in our cars.

I'm a pretty flexible guy, but I'm all about effeciency and good design. If I can't do it without cobbling it all together, I won't, but it seems plausible to me. So in other words, there will be a LOT of other things going on my car before I tackle a project like that.

Alex, let me know when you have that kit together, I'll probably have changed my mind 20 times by then anyway, hahaha.

[CodyAce]

Meh, 450+ rwhp LS1s are supposedly just a few bolt-ons away, but they always seem to be very hard to find without someone that's spent about $6-8k on the motor. At least at the track where you have to work a bit harder to keep a motor making that much power happy.

The C5 Z06/C6 guys I talk to at the track are usually in the 390-440 rwhp range, but on the upper end of that they usually have everything but heads, and that's NOT cheap. $2500 long tube headers, $1k cam, intake mani, blah blah - it all adds up, and it's not cheap. Plus the lower end powerband starts sucking for as big a V8 as it is.


There is no debate in the cost of doing an LSx based setup to 450 whp...but at the same time, whats it cost a VQ swap to that power level (reliably)...or a SR?? With that in mind, the cost ends up being the same.


450 whp is achievable with junkyard parts and a good valvetrain anymore (and rod bolts, don't forget) Hell a 6.0/l92 setup gets ya there with the right cam/valvetrain.

Low end powerband starts to suck? Still make more power than 450 whp 2.0 or 3.5, that's for darn sure...sure more cubes will help that, but if you're keeping 5.3/5.7/6.0 based than it's a weekend adventure to make 450 whp...we've done it, have friends that have them, and all hav eno issues (well aside the Forced induction LS team in our area...they all have bad luck aside from the procharger drag guys)


In the end of the day, it takes MUCH less worry and stress to 'campaign' a 450 whp LSx than it doesd a 450 whp 2.0 or 3.0 or any combination....especially when playing with a N/A vs F/I car...Sure my car sees 4-5 track days a year, not many...but not at 20 psi that's for damn sure. Now if it had a 450 whp 6.0/6.2 top end, it would have that power reliably all the time.


I don't get to tooo caught up with the brand stuff, juts what works and what is easy to work on...as this is what we all play with daily. Ultimately I'd rather swap a 5.3/6.2 setup into an E36, but that's just me ;)


PS: SloppyMechanics.com check out our 4.8 truck turbo ;) Bull**** turbo stuff under 2000 dollar build, 450 whp through a TH400 at no boost...god I love v8!

[CodyAce]

+1 on the "easy and cheap" 400-500-600whp LS1's I've always heard about. The way I figure it (and my bosses- I work at a rotary shop) it pretty much takes the same amount of money or work for any given HP level. Its just different depending on the engine. And I've seen and heard of real stories of plenty of LS1's blowing up under high G cornering due to oil issues. 6 of one half dozen another really.

I'll never doubt the HP per dollar aspect of all builds. I look at the 'whats it cost to maintain/rebuild/fix' aspect of things more than any of it. Call me a pesimist, or call be jaded, but I don't have the time to dream up wacky setups or attempt to reinvent the wheel, or get to caught up in 'what is cutting edge or high tech' with these setups. I'm a simple minded guy, who likes easily fixed/replaced setups, that make good reliable power. There's a reason peopl ehave been swapping v8's into everything, and not compound turbo 2.0's....think about it.

[PoorMans180SX]

I can list several reasons:

1. People don't know how to build engines.
2. People don't know how to design things.
3. People are afraid to do something custom, because they perceive custom as unreliable, when this does not have to be true.
4. They don't want to put forth the effort, and a swap is easy/bolt in.
5. Dudes get a boner over the sound of a OHV V8

None of these really apply to me.

[jspaeth]

^^ That compound turbo setup up there completely confused the **** out of me.


I don't understand how the big turbo can feed the small turbo.....I understand pressure ratio and how you can use one turbo to feed another, but ultimately, it also comes down to the mass flow rate of air.


Where, anywhere, on that smaller turbo's compressor map (at whatever pressure ratio) can it possibly support 600-700 hp worth of mass air flow?

I am lost.

[PoorMans180SX]

The exhaust gasses are bypassing the small turbo by a large amount using the wastegate from the manifold to the midpipe.

Remember that compressor speed is determined by the exhaust powering the turbine.

The big turbo's compressor is basically just pushing boost through the small turbo's compressor, the small turbo is just spinning.

[josh18_2k]

1. People don't know how to build engines.
2. People don't know how to design things.
3. People are afraid to do something custom, because they perceive custom as unreliable, when this does not have to be true.
4. They don't want to put forth the effort, and a swap is easy/bolt in.
5. Dudes get a boner over the sound of a OHV V8

you just listed every reason TO go ls1 lol. Do a ton of work, spend a ton of money (for anything not "bolt in"), and have it blow up because one little thing wasnt done quite right... or just put in something that works and enjoy driving.

its the same list i've seen on rx7club for years

lsx does need oiling mods, but its all the same stuff that should be on any abused engine. baffled pan, accusump, and oil cooler.

[PoorMans180SX]

Yeah except I know how to do it right so none of that happens. (That was the point)

I'm an old school import enthusiast at heart.

Not to mention my SR build will cost the same as an LSX swap. 1/2 dozen of one, six of the other.

[Def]

Def- no we are talking about a true Compound turbo setup.

http://i68.photobucket.com/albums/i17/paulvolk/DSCF0359.jpg

Thats a 2G dsm with a 16G and a t4 flanged 60-1. It puts down about 630whp- to almost 700whp, and makes 33psi at 3K.

The smaller turbo gets exhaust gas first, then feeds it into the larger second turbo, while fresh air goes into the larger turbo first then feeds BOOST into the SMALLER turbo (thats for other people, im sure they will skim and ask Q's any way) and then the smaller turbo feeds into the FMIC/engine.

That way the compressor flow is such that the smaller turbo runs its normal "PSI" aka pressure ratio range, and its happy and not being actually pushed that hard. The larger turbo runs completely normal.

On the exhaust side the smaller turbine isn't a restriction because its waste gate diverts any extra flow and keeps the turbo shaft speed and pressure in check like normal. That waste gate feeds back into the mid pipe that feeds the larger turbo exhaust side. Then it has its own turbo as well to control its boost just like normal.

http://www.youtube.com/watch?v=y-Me6yWApzY explains it pretty well except neither turbo is ever by passed, both work 100% of the time.

I plan on doing a compound setup on something, the rb20 I have, or get a CA18 or build a KA. Something.

But first I'm doing a VQ3X setup, na at first likely.

+1 on the "easy and cheap" 400-500-600whp LS1's I've always heard about. The way I figure it (and my bosses- I work at a rotary shop) it pretty much takes the same amount of money or work for any given HP level. Its just different depending on the engine. And I've seen and heard of real stories of plenty of LS1's blowing up under high G cornering due to oil issues. 6 of one half dozen another really.

Andy- I told you I'll have a VQ30 kit made to use the maxima ecu some time soon. Mounts, wiring, radiator piping, all that figured out. But I know its still not a normal swap. But cheaper motors for when you blow one, better sounding, no hassle USDM parts, etc etc etc.

~Alex

"Compound" is not the correct terminology for that setup. It's a serial twin turbo setup(turbos inline with each other, not in parallel).

I have my doubts as to how "happy" the small turbo is when flowing ~70 PPM of air, even if its pressure ratio is low. It might do it, but I imagine it's asking for turbo failure, and your shaft speeds are far higher than you're guessing.

[CodyAce]

I can list several reasons:

1. People don't know how to build engines.
2. People don't know how to design things.
3. People are afraid to do something custom, because they perceive custom as unreliable, when this does not have to be true.
4. They don't want to put forth the effort, and a swap is easy/bolt in.
5. Dudes get a boner over the sound of a OHV V8

None of these really apply to me.

Writing people off as 'incapable' because they don't go the hard way is a poor attitude towards things performance... to me, you like the alternative options as they are different...that's fine, but as above, don't assume people can not do something, just because they have not done something.

But as I said before, why are guys swapping these motors into every chassis out there....figure if they can go through the trouble, they'd go with the easy setup. I'm just a simple guy...to me, all of that crazy compound and turbo this/that is cool/impressive...and certainly it works....but at the end of the day, I'll take what's easy, whats easily fixed, and what is proven to work with the least amount of effort.

Look at successful (attainable costing) Forced INduction track cars....they are money pits, either from maintenance or to make them reliable will cost a bunch. (Trust me, I own a reliable turbo car...it wasn't cheap).

Now look at reliable 400-500 whp N/A cars....check oil, maybe change the pan for starvation issues (which you will do on VQ or SR anyway), 'bolt on' parts, or OEM parts...and you've got a snarly v8 with power everywhere. Cost? Will look at what it takes to make a 400 whp sr20? Yea...it adds up.


Cliffs: Don't assume people are lacking skill because they don't go the hard way...there is a reason why you see countless Vettes or v8 swap cars at track days, and maybe one compound setup a year, or in a lifetime. Again, different <> better.

[Def]

you just listed every reason TO go ls1 lol. Do a ton of work, spend a ton of money (for anything not "bolt in"), and have it blow up because one little thing wasnt done quite right... or just put in something that works and enjoy driving.

its the same list i've seen on rx7club for years

lsx does need oiling mods, but its all the same stuff that should be on any abused engine. baffled pan, accusump, and oil cooler.

Only on import forums are LSx engines ultra reliable when modded to crap and back. Just because a motor is NA doesn't mean it's reliable when you put aftermarket heads, big cam, higher pressure valve springs etc. I'm not saying they're a ticking timebomb, but they do not have anywhere near factory reliability when used on track from my experience. Just like any highly modified engine, you can improve some factory deficiencies(oiling etc), but start putting a ton of aftermarket parts on it, making more power etc. and you're typically going to start getting decreasing reliability.


All too often with a new solution or aftermarket parts, you're doing the development/proving work, especially when using the stuff on track. So failures with aftermarket parts is just a given across any industry(import, domestic, Porsche etc)

[e1_griego]

Josh's LS1 seems to be pretty bulletproof from all the abuse I've seen over the last 2-3 years driving with him. It's stock though, no big cam or anything.

[jspaeth]

The exhaust gasses are bypassing the small turbo by a large amount using the wastegate from the manifold to the midpipe.

Remember that compressor speed is determined by the exhaust powering the turbine.

The big turbo's compressor is basically just pushing boost through the small turbo's compressor, the small turbo is just spinning.

"Compound" is not the correct terminology for that setup. It's a serial twin turbo setup(turbos inline with each other, not in parallel).

I have my doubts as to how "happy" the small turbo is when flowing ~70 PPM of air, even if its pressure ratio is low. It might do it, but I imagine it's asking for turbo failure, and your shaft speeds are far higher than you're guessing.


What Def said is what I was talking about....look at a small turbo (like a GT2871R or smaller) compressor map.

EVEN at low pressure ratio, or ANY pressure ratio, you CANNOT safely run the turbo at 60-70 lbs/minute....it's so far right of the choke line, and the shaft speed must be ridiculously unsafe.


I am curious how long that turbo would last.....

[Def]

Josh's LS1 seems to be pretty bulletproof from all the abuse I've seen over the last 2-3 years driving with him. It's stock though, no big cam or anything.

That's the key. I've seen quite a few LSx failures over the years at the track, and all but two had some aftermarket valvetrain stuff on it. I think the stock ones died from a combination of retarded high oil temps(320+ deg F continuous on track, C5 Vette) and a little oil starvation.


LSx are the most common street car engine failures I've seen. I'd say the most common overall is all the Cobra Replicas at Road Atlanta blowing up their really modded powerplants.

[PoorMans180SX]

What Def said is what I was talking about....look at a small turbo (like a GT2871R or smaller) compressor map.

EVEN at low pressure ratio, or ANY pressure ratio, you CANNOT safely run the turbo at 60-70 lbs/minute....it's so far right of the choke line, and the shaft speed must be ridiculously unsafe.


I am curious how long that turbo would last.....

And my point is that you should be using a very large wastegate to run most of the exhaust gas around the smaller turbo, lowering the shaft speed, and basically leaving the big turbo pushing air through the small turbo's compressor, which shouldn't speed up the small turbo.

I don't know, but that sounds like it should work to me. I've considered other options, like a "quick spool valve" and the holset vgt turbo, but nothing seems as effective as this. Seems like ball bearing turbos should be able to handle the thrust loads and shaft speeds associated with such a setup.

Boost Logic makes a serial setup for the 2JZ, and Marc is running it in his "street fighter" Z31. The power curve (310ft-lbs at 3000rpm and 510ft-lbs at 4000rpm) and pull are insane. There are multiple videos on youtube.

[jspaeth]

And my point is that you should be using a very large wastegate to run most of the exhaust gas around the smaller turbo, lowering the shaft speed, and basically leaving the big turbo pushing air through the small turbo's compressor, which shouldn't speed up the small turbo.

I don't know, but that sounds like it should work to me. I've considered other options, like a "quick spool valve" and the holset vgt turbo, but nothing seems as effective as this. Seems like ball bearing turbos should be able to handle the thrust loads and shaft speeds associated with such a setup.

Boost Logic makes a serial setup for the 2JZ, and Marc is running it in his "street fighter" Z31. The power curve (310ft-lbs at 3000rpm and 510ft-lbs at 4000rpm) and pull are insane. There are multiple videos on youtube.



I understand your point.....I just don't see how if the smaller turbo comes SECOND, that you can fully utilize the first, BIGGER turbo's fully capacity.....ultimately all the air that flows out of the big turbo MUST pass through the second turbo...

And if the second turbo is small enough to spool quickly, then presumably, the shaft speed required to support 60-70 lbs/min of air would be dangerously high.


You can't push that much air through the small turbo WITHOUT having the unsafe, enormous shaft speed.....how can you?

...not trying to fight, just trying to make things clearer to myself as well

[PoorMans180SX]

Big turbo comes second on the exhaust side, which is what determines shaft speed.

Remember it's just pushing through the smaller turbo's compressor, not "powering" it. The smaller turbo shouldn't really speed up at all from this. So really the big turbo is pushing all the air (at high rpm/big boost), it just happens to go through the little turbo's compressor on the way to the intake.

So the whole process goes like this:

Engine starts getting to where the first turbine starts spooling. First (small) turbo starts making boost. Once it reaches the wastegate pressure (at this point the big turbo is starting to spool) the wastegate opens and diverts the exhaust energy around the smaller turbo, fully spooling the big turbo. Total boost pressure reaches a set level, and the second wastegate opens up.

[240sxTTC]

For a 600hp application with a series (compound) setup the low pressure turbo (bigger turbo) must be able to support 60lbs/min. The high pressure turbo (smaller turbo) is utilized mostly for low rpm operation. The compressor outlet of the LP turbo feeds into the inlet of the HP turbo and during higher rpm operation the inlet pressure of the HP turbo increases. The pressure ratio dictates the shaft speed and since the inlet pressure of the HP turbo is high the the pressure ratio stay relatively low and therefore so does the shaft speed. There are a few ways to configure series setups and the valving to make it work properly gets difficult. I done some crazy series and series sequential matches. The problem usually comes done to packaging constraints.

[Def]

For a 600hp application with a series (compound) setup the low pressure turbo (bigger turbo) must be able to support 60lbs/min. The high pressure turbo (smaller turbo) is utilized mostly for low rpm operation. The compressor outlet of the LP turbo feeds into the inlet of the HP turbo and during higher rpm operation the inlet pressure of the HP turbo increases. The pressure ratio dictates the shaft speed and since the inlet pressure of the HP turbo is high the the pressure ratio stay relatively low and therefore so does the shaft speed. There are a few ways to configure series setups and the valving to make it work properly gets difficult. I done some crazy series and series sequential matches. The problem usually comes done to packaging constraints.

I understand the density of the air in the smaller turbo will be much greater when the larger turbo is spooled, but it still seems like it'd be spinning it's ass off for probably flowing well over its corrected massflow at a "low" pressure ratio.

Maybe it's not that bad with high enough pressures, but I can't imagine flowing something like 70 PPM through a tiny ass compressor inlet/outlet without some truly massive pressure drop.

[jspaeth]

I understand the density of the air in the smaller turbo will be much greater when the larger turbo is spooled, but it still seems like it'd be spinning it's ass off for probably flowing well over its corrected massflow at a "low" pressure ratio.

Maybe it's not that bad with high enough pressures, but I can't imagine flowing something like 70 PPM through a tiny ass compressor inlet/outlet without some truly massive pressure drop.


I still don't get it. I understand what they are both saying, that if the pressure doesn't change, the shaft speed would be low, but even if you look at a GT2871R compressor map (not THAT tiny of a turbo)....WHERE on the compressor map would you be operating.


ANY pressure ratio at 60-70 ppm still puts you so far right of the choke line:
http://www.turbobygarrett.com/turbobygarrett/images/catalog/Turbochargers/gt28_images/743347-1comp_e.jpg


Literally you would be ridiculously off the map, even at a pressure ratio of 1.


If many people are doing this, and it DOES work, and their turbos ARE still okay, then there must be something that this simple "compressor map approach" is missing.

[Def]

The X axis is corrected airflow. So you can use the ratio of total pressures to get a round about correction. At 30 PSI of boost you can flow 3 times as much air as at atmospheric pressure at the same volumetric flow rate.

The only reason it probably works is that there is a HUGE pressure drop across the inlet of the tiny turbo, and since you have a higher "driving force" there, you don't really have to worry about choking as much as sucking in atmospheric pressure. Think of the choke line as reaching the maximum amount of flow you can get with atmospheric pressure "driving" the flow. If you put another turbo upstream of your small POS, then you can just raise the pressure on that turbo to get higher density and more "driving force."

So it might all work out fine due to the density change, but I'd be really curious to see what the compressor speed of the smaller turbo ends up doing.


I think doing a valved twin setup like a Supra/FD3S would probably work a bit better. Just have to find a high temperature valve and then program it up with some sort of ECU switch.

[jspaeth]

Thanks for the good explanation Def....that made more sense.

[Rustspecs13]

Like Marc says in his video- the turbos operate like 2 independant systems, as far as the stress and shaft speed are concerned. Each turbo will spin as fast as the waste gate lets it. He gets it wrong when he says the one wastegate bypasses the primary turbo, it only bypasses what it needs to maintain boost for the smaller turbo like normal.

The smaller turbo's waste gate gets its "atmosphere" signal from the output of the larger turbos compressor since the smaller turbo's inlet pressure is the output of the larger turbo.

The shaft speeds will be exactly the same as in a normal setup, unless you want to over boost them just like a normal setup.

The ONLY down side I see is hot air getting fed into the smaller turbo. That's the only factor I can see wearing down on either turbo in this setup.

Diesel trucks run turbos like these, and they are called compound turbos. So that's what I call them. Some of them don't even run wastegates, but looks like lately more are putting WG's on the primary/smaller turbo.

jspaeth- think of a turbo in a normal setup. At sea level, pressure pre compressor is say 14.7psi of atmosphere. 10K feet above sea level its say 5 psi. You will notice a performance difference because the turbo is not efficient or makes the same boost really. The Bigger turbo changes the atmosphere pressure the turbo sees. Its efficient at compressing air at a certain rate, and the higher pressure means that it can flow more over all.

~Alex