nitrodann

The A/R is kind of like how you hold your lips when you blow onto a pinwheel.

If you purse your lips tightly together you can get the fan moving without having to move a lot of air, but ultimately you will be restricted in the rate at which you can exhale by your pursed lips. If you blow through a couple of McDonalds straws then you will have to try harder to get the pinwheel spinning due to the lower gas velocity but you wont be limited as much in terms of how fast you can exhale if you exhale really hard.

A bigger A/R makes the entire engine system (air filter to exhaust tip) less restrictive, at the expensive of high velocity low rpm exhaust gases making the turbo spool up slower.

Dann

Savington

iTrader: (31)

There were cars 10+ years ago doing 575whp through the stock head casting.

Based on the few high-boost 6258 setups out there, I'm speculating that ~415whp is about the limit of the 6258 compressor wheel. Emilio did ~405whp through a fully built head with +1/+2 valves. I did 415whp with a stock head at the same boost level through the same turbine housing, but with a 6758. That says something about the efficiency of the 6258 at the right edge of the compressor map.

At some point the 0.64 housing is going to be a restriction. That point is not 400whp.

OP, as I said on the phone, the TS setup is just going to bring you headaches.

matrussell122

iTrader: (1)

Kinda my thought. There is one other guy that has a 6758 an Matt at Hellafab is building our manifolds side by side. Worked out nice because the other guy shipped his turbo there for mock up.

The phone call we had was very informative, pretty much drown me in info which was great. My only issue is I have already paid for the custom twin scroll manifold and now possibly having second thoughts and wanted to see what the community would like to see if I fell into a testing hole.


Everyone else thanks for the reply's. This is the kind of tech based discussion I wanted to stir up instead of the do this or do this. As I said above there is one other 6758 TS in the works right now that would give an possible A/B comparison but im pretty sure that they arnt on the forum so it might not be a good data point.

As another question what do you all thing the mode of failure would be on either TS tubular manifold or SS TSE manifold (If I back out of the TS ill just order the proven TSE kit)

18psi

iTrader: (76)

Based on track records over the years, the cast will always outlast the tubular by a big margin.

matrussell122

iTrader: (1)

Just due to cracking? Im guessing right next to a weld near the head due to the cantilever action on the manifold?

18psi

iTrader: (76)

I've seen a high quality ARtech crack at the collector (99nb's car, tracked really hard), and I've seen an ABSURDflow crack somewhere in the middle iirc (savingtons or hustlers car, I forget). Both are really high quality builders using high quality materials, and in the end both admit that a tubular will in fact at some point crack, no matter how much you reinforce it.

There have been a couple log failures too, but like a handful out of hundreds/thousands tracked over the years.

It's really not a big deal unless you plan to track your car regularly.

matrussell122

iTrader: (1)

As of now the car is dual duty but probably wont see a track until life slows down a bit. How often do they crack under regular track use and proper bracing. Is it a crack a weekend or once a season? Welding cracks for me isnt a big deal since I have the equipment on hand but the time of taking it all off and back on all the time isnt my idea of fun.

Arca_ex

iTrader: (2)

Didn't that take like 4 years of consistent track events to happen though?

18psi

iTrader: (76)

Something like that. Definitely not a frequent occurrence, because both those guys make top tier stuff.
The tse unit is still relatively fresh, so time will tell, but so far I don't know of a single unit that broke.

shlammed

iTrader: (8)

just found this thread.

go 6758 for your goals. 7163 would be cool to see.
the 6x58 and 7163 regardless of the turbine housing are all b1 frame turbos with alternate turbine housing. b2 frame is a 7064 and 7670 +.

tubular manifolds get out-performed by cast? depends what your idea of performance is I guess. they are indeed more stout and will last for 10, 15 20 years... oems use it for durability and cost. There are no reasons that a cast manifold will outperform a tubular manifold for power, and in this case the twin scroll will add performance.

FWIW, I am working on sourcing a new project Miata and will be using the same turbo placement as you MatRussell, in twin scroll with 7163 spec but it probably wont happen for another 6-7 months when I have finished my new shop and other manifold projects on the go.

psyber_0ptix

iTrader: (4)

Interested in being one of the other manifold projects

matrussell122

iTrader: (1)

What are you cooking up? Are you going to do the built head and twin scroll?

psyber_0ptix

iTrader: (4)

At this point it's all coming out anyway for a rebuild. May as well up the ante with each iteration.
​​​​
I will stick with the 6758 because it's already a reckless mess and would keep cost down for me if all I have to get is a twin scroll housing.

matrussell122

iTrader: (1)

So then why a new manifold if not a twin scroll? Not that i dont condone a new manifold,schlammed does great work. A 6758 TS could be a very wild track car. lets doooo eeeeettttt

psyber_0ptix

iTrader: (4)

Oh I meant twin scroll but 6258 Turbo, until I see a completed 7163 on the dyno and it's response time I'm not convinced yet it's worth the upcharge

matrussell122

iTrader: (1)

going from your 6758 SS to a 6258 TS Wont you lose a bit of top end power since you are running #allofit right now?

18psi

iTrader: (76)

I'm sure it's a type-o. but I also think he's gonna lose top end even with the 6758 because TS

psyber_0ptix

iTrader: (4)

is this a case of a larger turbine would be more beneficial because moment arm thing (all TS a/r being equal)?

I thought that despite the higher A/R on the T4, the efficiency gain from the twin scroll would counter act the loss in spool.

Here's a snipet of a response I got in PM when considering adapting the 3sgte full-race twin scroll manifold to Miata flange. (This was a WHILE ago). Shlammed talked me out of it.

shlammed

iTrader: (8)

im going to say probably not... because t2 flange and now t4. t2 is pretty tiny at his power levels.
t4 open vs t4 twin scroll you would loose power in a drag application, yeah. but a t4 TS footprint is 1.8x the area of the t2 footprint for exhaust gasses to flow.

for those reading that thinking it will hurt spool, the A/R for the wheel is still the same, so there is more reduction of x-sectional area inside the turbine housing instead of inside the manifold. I have my theories about this, but generally it will help the manifold last longer because the heat isn't in the collector, and I expect it will bump efficiency of the turbo itself because the heat is being put as energy into the wheel instead of being wasted.

I fully expect the TS version to spool the same as the t2 based turbo, but expect the power to remain more linear with the free flowing housing as well as some other little things. Will set psyber up with a manifold once I get rolling on making more than one of them at a time... which will be in time for next season.

18psi

iTrader: (76)