s15 efficiency

[boost_creep]

im lookin for the next step with my sr...it seems like the s15 bb turbo is a good choice from most of the people in here...my question is...what is the s15s efficiency range...(the t25 is maxed at about 15psi)...so what can the s15 produce?...or any other suggestions about going a ifferent route is welcome too.

[SoCalS14]

I have always heard that it maxes out at around 300hp...which is my goal, thats why I have one...hehe. Cn't remeber the psi rating though...I am thinking maybe 16-17??

[SpeedRacer1]

Heavy Throttle always said the S15 T28 would be good for up to 18 psi. The power on all the OEM turbos trails off towards the end of the powerband. Upgraded turbo's usually provide power through the end of the power band.

[chickentendah]

If I may ask, while on topic, does the S15 bbturbo have drastically better turbo lag characteristics compared to t25?

(Everytime I hear a WRX or a EVO drive by, I get jealous because they have virtually NO turbo lag.)

[SpeedRacer1]

Depends on your definition of "drastically." But if you put a T28 BB turbo on your car, chances are you will feel a world of difference. They spool up slightly faster, and push out more air than the T25 so they will sound a lot better.

[Nismo_Freak]

If I may ask, while on topic, does the S15 bbturbo have drastically better turbo lag characteristics compared to t25?

(Everytime I hear a WRX or a EVO drive by, I get jealous because they have virtually NO turbo lag.)

STi's EJ25 has no lag in it's powerband, but the EJ20 is pretty laggy from what I've driven. Then again there are alot of mods to help the EJ's spool, but there is little the EJ can do to make the spool better than the SR"s.

The EVO's may build boost early, but they still don't pick up until about 3500 rpm.

I still want an 05 STi for a daily.

[s13sr20chris]

heavy throttle says the t25 is good to 15psi and they are right. it can run 15psi. the problem is that its WAY unefficient at that point. many shops will tell you that a t25 running 13-15 psi is just a ticking time bomb. at the same time some folks have run 13-15 for a long time with no probs. i would just take all this into consideration if you run a s15 turbo at 18psi. also note that the s15 turbo is not as efficient as the disco potato but the scc car is running 17 or 18 psi(cant remember). that is with the tuning help of mike kojima who actually has the turbine map for the ns111 turbine(super secret stuff i dont fully understand).

bottom line: if i had an s15 turbo i would test the outlet temps before i settled on a boost setting.

edit: i know the turbine has nothing to do with the compressor efficiency but i was just using that as an example