Need help with turbo A/R

[dirtdiggler]

Just finished up my car and have been enjoying it but there is one thing I don't really like. The turbo I used is a BW s257 sx-e but it won't really come on tell about 4k. I ended up going with a .96 A/R open figuring the turbo is small and would help with flow. Another question can the psi change when it comes on at all? I am only on a 7 psi wg spring right now.

With this setup I will never go over 14-16 psi so what would be the best housing for me?

only other options are .68 and .81

[someguy2800]

Since your not pushing it that hard I would not be afraid to use a .68

[someguy2800]

Also you might want to check that your wastegate is sealing and that your vanos is working. I would expect that turbo to start signing at just over 3000. An s366 comes on around 4000.

[Mklock]

4k is when M5x/S5xs come on anyways. I was at 15psi with my S257sxe well before 4000 rpms. Probably 3300...now the car naturally pulls extremely good at 4k to rev limit. 7psi with the S257sxe was literally at any throttle input. If I started at 2k rpm and floord it, I'd see 7psi by 2800Rpms. Try to see what your gage is reading and not when you feel the most pull. The S200 frame size is quite small anywho, If you're single scroll .9 would be the biggest you can put on it. I ran a 1.10 but it was twinscroll. My S300 a/r housing is a 1.10 as well. Still turns on pretty quick.

[dirtdiggler]

Ok I am going to check for any leaks to hopefully rule that out when I have time. I just went for a quick drive and I was a little wrong, I saw 1-2 lbs at about 3200-3300 and about 5 lbs at 3500 and 7lbs at 4000. My psi gauge is kinda far from the tach so its kinda hard to see at the same time.

Would there be a big difference from the .96 and the .68 if so how many rpm sooner "guessing" would it start to spool?

[someguy2800]

That is a pretty big change. I would expect it to make 200 or 300 hundred rpm difference. A electronic boost controller will also help since you have such a light spring in it.

[Mklock]

Someguy is spot on, if youre just running of wastegate, 7psi will crack open earlier than the *spring rating* resulting in it coming on later. .96 to.68 would help it come on faster, you'll have more boost earlier but probably still won't feel like much till 3700-4k I say try it and report back! Data is good.

[pbonsalb]

Try raising the boost to 14. That might improve the response. Like others have written, your WG is opening early in order to not exceed 7 psi. If you run 14, it will stay closed longer. Right now, it’s venting before it’s really woken up. After that I would try a smaller turbine housing and/or an electronic WG controller.

[dirtdiggler]

I was thinking the same thing that the wastegate was doing its job a little too well and I'm sure that a good thing in a way. I took a little video with my phone and sometimes it would look like it only got to 6.5 psi. So I was also wondering if the spring is way to soft and the turbo was moving a lot of air that the wg was bleeding off air very early?

should I put a 10 or 11 spring then control with boost controller? I just don't want 14 as a base.

Not sure if it matters but its a turbosmart 45 mil

[pbonsalb]

TS 45 is not a great WG but is probably fine at your flow levels. A 14 lb spring is supposed to give you around 14 psi. It opens earlier than 14 psi. Systems can vary so it might give a little less or a little more. With an EBC or an MBC, you are essentially lying to the WG. You can get more out of the spring rating. EBC tend to give the best response by cycling the WG so it is open as little as possible.

[dirtdiggler]

Why is a TS not a good WG?

But if I use 14 psi spring and a boost controller won't 14 psi be the lowest I can go?

Also any good recommended boost controllers?

[pbonsalb]

Yes the WG spring is the floor. The TS 45 has limited piston travel and does not flow well, at least compared to a Tial 44. I wish I had not bought one. But I have an internal and an external and seem to be doing ok with the two of them.