BW S257SX-E turbo

boosted79 · 05-15-2016, 03:13 PM

I'm looking at turbos for my engine. 3.3L, SC cams, headers, IC, CIS. This one looks promising.

comp. 57 x 76 mm
turbine 70 x 61 mm

T3 twin scroll, 0.83, 1.0, 1.15 or 1.22 A/R

The circles I put on the map are 2,3,4,5,6,7 krpms.

Same compressor size as a GT3076 but with a turbine size of a 3582. GT3076 has a 60x55 turbine. 3582 has a 68x62 turbine.

This would look better at 1 bar, I think I need a new spring.

Tippy · 05-15-2016, 06:00 PM

That IMO is a perfect turbo for the stock headed and intake 930 crowd.

I'd run the 0.83 or 1.00 AR housing.

GJF · 05-15-2016, 06:37 PM

It actually maps 1 point higher on the PR side. A pair of these map out well for 800+ and still have good low end manners without over boosting.

kenikh · 05-15-2016, 07:19 PM

S362 also comes in a T3 .83 twin scroll for those with a ports, exhaust and want more power with minimal lag. BW makes some great turbos.

JakobM · 05-16-2016, 03:03 AM

5761
BW makes great and innovative turbos, but the wheel configuration are in general too much "diesel" for me. Specially for a 930 non-twin scroll header 61mm is too much turbine wheel size on a small 57mm inducer compressor wheel for my taste, that is regardsles area of housing put on afterwards.

Compr. inducer vs. turbine exducer
BW keep its roots more solid grounded in diesel configurations and you will general find larger turbine wheels parret with compressor on the BW programme compared to other manufactures like garrett precision etc. The single most important factor to spool-up is wheel configuration, most gasoline racing turbos tend to be more egual on the comp inducer vs. the turbinde exducer. A 5761 turbo will spool-up slower than a 5858 or a 5959 and all still procuce solid 500-600hp. That is everything equal and regardless bling bling ball bearings.

Compressor map
Dont forget the turbo shaft rpm. The smaller you go on the compressor inducer the more shaft rpm the turbo has to make to build the same boost. If you compare that on a compressor map, you will see that a turbo with larger compressor on same size turbine wheel, will actually move same amount of air with much less turbo rpm hence build boost quicker. The minor added weight from going larger on the billet alu wheel is non-issue in the comparison. The compressor map from BW in this tread do not show the turbo rpm lines (sadly), look at other compressor maps with these shaft rpm printed and it gets interesting, you will find e.g. 10-20.000 shaft rpm in difference between two different optioned sized compressor wheels reach the same boost level - now think which of these two wheel sizes you want attached in the other end of a e.g. 61mm turbine wheel to either go 100.000 or 85.000 rpm to build one bar of boost. Same turbo, same turbine, different compressor wheel. (example figures). Smaller compressor wheels do not build boost quicker (area does) - what a smaller compressor wheel will do, is increase the backpressure from the added turbo shaft rpm that on the other end of the shaft block up the turbine sooner before reaching the desired boost level in the compressor. So a 5761 turbo will need more turbo shaft rpm (and hence larger turbine to keep backpressure under control) compared to a e.g. hybrid 6559 turbo which is oppersite configured.

Example hybrid configured turbo
A low pressure racing turbo (i.e. <= 1.5 bar ) with 6559 configuration, i.e. 65mm forged billed compressor inducer with 59mm inconel exducer, can be used for solid 350-650 hp with very quick spool-up. Turbo shaft rpm are very low, 59mm turbine exducer put on twin scroll setup and large area/A/R, no issues on surge (antisurge compr.), backpressure reduces as shaft rpm recudes, large diameter wg(s) take care of the venting when boost is reached. Just a comparison in the other direction. Wheel size first, then area/A/R (low on wheel and size up on area), always twin scroll. Used heavily in drifting when among others quick boost and low temperatures are needed.

Twin scroll
If buying a twin scroll turbo make sure the WG piping is correct for twin scroll, either correct split with one wg (yes, you can build correct TS with one WG), or simply two wg's. Some get the twin scroll psysics wrong as most of the 930 header suppliers have it wrong. A split plenum T3 or T4 header build with open"single- or Y-shaped WG piping and branded as "true split plenum with both banks isolated" is not a split plenum header and will never be a split plenum header. They always need new tig welding or always other options to discard the incorrect WG setup for a true split bank setup. Many 930 owners are runing such mis-match setup together with a twin scroll turbo beleiving thay have a split plenum header/system. A split plenum header with incorrect open single- or a Y-type WG piping will loose 800rpm of boost on a 3.0L.

I choose wheel size first depended on the desired boost pressure in play- not afraid of the surge (off map) in the low rpms as the compressor housing has antisurge, choose twin/single scroll Next (always TS when possible), then choose Area/A/R based on the two other parameters. In generel more equal on comp.ind. vs. turbine exd. or larger compr. ind. depending on special application.

boosted79 · 05-16-2016, 04:55 AM

GJF -"It actually maps 1 point higher on the PR side." - not following you here? (1+.8)/1 = 1.8 PR for .8 bar boost.

JakobM - I am digesting.

Tippy · 05-16-2016, 08:28 AM

Jakob, I thought the same, but I'll tell you, BW is legit!

Mine has a 73mm exducer on the turbine with a 66mm inducer on compressor (S366). That's a big spread, and I had doubts.

But if you watch my videos posted, I can EASILY hit 1.4 in 1st gear with a G50.

Not to mention, boost recovery is insane with mine.

I've had 3 turbos on my car, and this one is king.

JakobM · 05-16-2016, 10:15 AM

Yes, a 6673 is a great turbo and works well on a high output 930, just saying a 6768 or a 7668 on T4 twin scroll is a different animal... personally I like the latter best :-)

What engine specs and output are you running? - do you have a link, would like to see your car in action

Rich76_911s · Rich76_911s's Garage

Quote:

Originally Posted by kenikh

S362 also comes in a T3 .83 twin scroll for those with a ports, exhaust and want more power with minimal lag. BW makes some great turbos.

Kenikh,

Where have you been able to find the 362 in T3 .83 twin scroll? I've found them in T4 but haven't found T3.

Thanks
Rich

kenikh · 10:57 AM

I can't find a 5959 anywhere. Where do you source one? Seems like a twin scroll T4 with .83 AR and 5959 wheels would be the ultimate 500HP fast spool Turbo.

Btw, where do you get the compressor map app in the screenshot?

kenikh · 05-16-2016, 10:57 AM

Quote:

Originally Posted by Rich76_911s

Kenikh,

Where have you been able to find the 362 in T3 .83 twin scroll? I've found them in T4 but haven't found T3.

Thanks
Rich

I believe I misremembered. Can't find one.

Tippy · 05-16-2016, 11:09 AM

Quote:

Originally Posted by JakobM

Yes, a 6673 is a great turbo and works well on a high output 930, just saying a 6768 or a 7668 on T4 twin scroll is a different animal... personally I like the latter best :-)

What engine specs and output are you running? - do you have a link, would like to see your car in action

7668? That's well over 1000hp. Assume you're using on something other than a 930?

I posted videos under my thread with S366 in the title. That was shot with old IC, without IC, I'm not able to control boost any longer, and hitting over 1.4 bar in 1st occurs. Will put on twin WG's soon.

Rich76_911s · Rich76_911s's Garage

Quote:

Originally Posted by kenikh

I believe I misremembered. Can't find one.

Damn I was hoping I was misgoogling

I did find this that is a .80 a/r t3 divided housing that would work on the s362, but I'm not sure how the HX40 outlet would/wouldn't work on our cars. Not exactly cheap either!

http://www.agpturbo.com/t3-divided-inlet-hx40-outlet-14cm-for-s300/