Been reading just about every build thread on here and hoping that around the end of the summer I'll finally be able to finally get started on my own build. While I'll have another vehicle to drive during the build, ultimately this will go back to being my daily driver so I have more modest goals than a lot of the cars here. Mainly looking for 350-400whp on E85 and to keep AC. Just looking for some advice on what parts I'm currently looking at...
120K M50B25 (compression within 5 psi on all cylinders, runs great)
S50 cams
3 inch turbo back
Cut ring gasket
ARP head studs
SPA bottom mount manifold
BW S257SXE
eBay intercooler (probably going to get an overkill intercooler for when I want more power down the road)
RK Tunes or MS PNP
I'm wanting to stay on stock compression to help spool and make torque on the low end. I know for higher boost that basically will require E85, which I have available. However, for roadtrips and daily driving, is stock compression + 91 octane + wastegate pressure (6-8 psi) going to be safe for the engine?
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The issue with your plan is the OEM rods. You need to reduce the low end torque and move the curve to the right so you dont squish them.
The recipe you proposed is usually to increase low end torque and response which will cause problems. See Rajicase's thread.
At the low power goals it might not be a huge issue, but its doubtful he would stay at that level for long
I maxed a s256sx out on my stock s52 rods. It made 465whp/418wtq. As soon as I put the 366sxe in on e85 at 21psi it bent several rods after just a few quick pulls.
I think 6-8lbs on 91 octane is probably about as high as you'd want to go on stock compression.
I would strongly suggest lowering compression if you ever plan on running 91 octane.....
Like I said, really wanting to keep stock compression just for off boost response and to minimize lag. Running on pump would be for DD/roadtrip duty, anything that involves me beating on the car is realistically going to involve E85 and high boost
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You're really going to want to get aftermarket internals if you want to go that route
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So you guys think I'll be better off with copper spacer then?
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Definitely. But consider buying a more responsive turbo even if it costs more. Butters has a customer with a journal bearing 0.63 PT6262 that seems happy, though I have not driven the car. With your 2.5L you will want a responsive turbo and to be able to run higher boost. Spa T3 manifold and maybe PT6262. Maybe an even smaller turbo but not a diesel truck turbo like the BW even if you can get a small back housing for it.
Last edited by pbonsalb; 06-26-2017 at 08:35 AM.
My decision for the BW was actually after riding in a Z3 with a S256 and an M52...I know the extra bit of displacement definitely helps but it made right at 400whp on 93 and spool was great. With the lighter wheels and the fact that it flows more to boot, I think that the S257 is a good option considering it spools damn near like a GT3076R (at least according to Rapidspool's testing) and BW turbos are renowned for being very close to indestructible
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The S256 that raji had was a dog in terms of spool. But he had a massive back housing -- maybe a 1.22?
Yeah he had the biggest back housing they come with because he was worried about choking it up top. When rapidspool tested it back to back on their Evo with a GT3076R it spooled a couple hundred rpm faster and made 40whp more I believe
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Idk why I said rapidspool, meant full race...this was back to back dyno they did with a twinscroll S256 and a GT3076R on an Evo 9 and then an overlay of a GTX3071 on a different car with the same setup. They had a thread about it somewhere on Evo forums but I have no idea how to find it again
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I plan to use the same turbo on my z3 eventually. I'd say just run a 0.90 gasket to drop compression a bit (IIRC that will give you 9.5:1) than run 8-10 psi on 91 and 16-20 on e85. Torque kills rods, but you don't have to worry as much with a smaller displacement m50. Franc proved a stock compression m50 with a cutring and studs can handle 700+whp/500wtq on stock internals on e85 with good tuning. You will max probably out that turbo on e85 before you bend a rod, provided you have good tuning.
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For a 2.5L and 300-400 HP I'd be strongly looking at a 5858 or Garrett version 5857.
Or you can have 2k rpm powerband with the a 62mm+ turbo. That's no fun in my opinion
1996 332IS
Built 3.2
CES/Steed TS Precision 6466, spraying a "$π!℅" load of meth.
Technique Tuning 80# tune.
1/4 mile 10.84 @ 136.72
Your 1 and only stop for all your BMW performance needs
WWW.CESMOTORSPORT.COM
62+mm? I was looking at a 57mm...and I do want to have some headroom on how much I can make down the road. I just want to start with a somewhat reliable and manageable power figure since even 350whp is double what it makes now
I did look at the 5858 but it seems pretty comparable to a S257SXE at a much higher cost, unless I'm missing something
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1996 332IS
Built 3.2
CES/Steed TS Precision 6466, spraying a "$π!℅" load of meth.
Technique Tuning 80# tune.
1/4 mile 10.84 @ 136.72
Your 1 and only stop for all your BMW performance needs
WWW.CESMOTORSPORT.COM
1996 332IS
Built 3.2
CES/Steed TS Precision 6466, spraying a "$π!℅" load of meth.
Technique Tuning 80# tune.
1/4 mile 10.84 @ 136.72
Your 1 and only stop for all your BMW performance needs
WWW.CESMOTORSPORT.COM
Same price for the Garrett GTW 5857 , or the GTW 6262 is a hair more. But too much for a street 2.5L
1996 332IS
Built 3.2
CES/Steed TS Precision 6466, spraying a "$π!℅" load of meth.
Technique Tuning 80# tune.
1/4 mile 10.84 @ 136.72
Your 1 and only stop for all your BMW performance needs
WWW.CESMOTORSPORT.COM
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