Upgrade bolt on BB 50 trim to a t3 hotside

[henrysan]

I currently have a garret BB 50 trim on a mitsu style bolt-on turbine housing. I am thinking about upgrading to a .63 a/r t3 4 bolt outlet turbine housing using a t3/dsm adapter to keep my tubular exhaust manifold, and also adding the matching 4 bolt t3 o2 housing. Would the gains be worth it, or should I just save this money toward a larger turbo setup in the future? I have seen up to 49-50lbs hr flow in dsmlink at 27psi with current setup.

 

[JusMX141]

If you're already seeing 50 lb/min, you're not going to see much improvement going with a larger turbine housing unless you plan on cranking the boost a bit higher. The car may be a little easier to tune on pump gas, but that's about it.

I'd save your money for a bigger turbo in the future.

 

[henrysan]

Alright thanks for the info. After adding gsc s2 cams, I notice the car really wants to rev, and was worried about back pressure at high rpms with the bolt on mitsu hotside.

 

[Black95TSIawd]

Less back pressure is a big plus all around. You might incur some more lag, but pick up quite a bit of power up top even at the current boost levels.

 

[Kevin Jewer]

If the airflow doesn't go up, the only gains will come from reduced pumping losses, and that may not add up to much at that power level. You'd have to know what back pressure is now to make a good decision. My gut feeling is that even if it picks up a little, it will not be worth the effort, and you'll wish you put that cash toward the next turbo as you already suspect.

In cases where airflow can go up, VE gains from reduced back pressure go a long way. Dropping 30+ psi back pressure on my car recently was a real eye opener. It took a significant increase on the turbine side (and a slight increase on the compressor side) to achieve that though. Just changing housings on the same wheel will make a much smaller difference.

 

[bastarddsm]

Not to step on kevin or Justins toes, but from a different perspective. The compressor takes power to run, that power is something like (mass flow* Pressure change^1.4)/(comp efficiency) The turbine power is similar (massflow*pressure drop^1.4)*(turbine efficiency)

It's really more complicated as there's temperature and entropy and enthalpy and such... but the above is simple and gives you the idea.

Anyway you can see that the pressure change has a much larger effect on the pressure requirement than the mass flow. So basically you'd have to have a massive gain in mass flow across the turbine to get much of a drop in drive pressure. As kevin says, that's a big change in wheel and housing.

Final note, the temp part I left out has almost as much of an effect as the pressure. So the thing to take away is that you'll probably get more gains from making sure the air getting into the turbo is as cold and as high pressure as possible, than from a bigger housing.

 

[henrysan]

Awesome info everyone thanks. I have my plans set toward a s256 borg warner and more fuel to feed it, but I am also at the point that I need to look at forged internals..so my next step in power would be a huge hit on my wallet.

 

[bastarddsm]

The 256 isn't a a huge step up from your 50 trim. I'd maybe looking at a S259.

 

[henrysan]

The 256 isn't a a huge step up from your 50 trim. I'd maybe looking at a S259.

I was a little worried about slow spool on the s259. If the s259 in a .63 or .70 a/r t3 housing can spool around 4.5k I would consider it. Thanks agian.

 

[Steve93Talon]

An S256 or 259 will work fine with stock internals. I've run both on stock bottom ends, the 256 in a bolt-on housing and the 259 in the .70 T3. I made more power on pump with the T3 setup (119 vs 123 mph traps, straight 93, 30psi, FP2s, stock 1G head/intake/bottom end), but it was about 1k rpms laggier (30psi at 3700 vs 4800). If I had it to do over again with the S200 stuff, I'd do the 259 in the .85 divided T3 housing. It would spool very close to the bolt-on and fully support the compressor flow. Then again, both are fairly old tech these days compared to the billet BB stuff so I'd have a hard time justifying spending the money for a proper manifold/gate/o2 combo and then short changing on the turbo. For example, the EFR7163 will flow about the same as the 259 and see full boost in the mid 3k range.