I suspect my answers will be similar to kiwigenes, but let's do them anyway
Old_Gregg_ wrote:Got a few questions that ill ask here rather than in PM for the benefit of others. Got an Auto btw.
A lot of people in the thread have mentioned getting a dump pipe before their tune, cant seem to find why I can only assume its the easiest way to get more power out of a tune, can anyone elaborate?
The stock dump pipe is a significant restriction on your engine's ability to put out power. To start with, when you take if off, the section that sits over the wastegate is actually blocked off. Replacing it with a better (after market) dump frees up the exhaust side of the turbo, helping the turbo to spool up faster and to run harder at the top end. There's some additional noise as well, which if you're into performance tuning, probably won't come as a disappointment.
Is there any risk of damage due to the retune, Someone mentioned earlier in the thread about running on S# any not wanting to risk damage, wasnt sure if they were joking. Im assuming the oil temp light still works and is still applicable.
There's always a risk - but the stock tune is safe to the point of stupidity (literally - Subaru have to tune for stupid people to drive their cars, as does every manufacturer). Good tuners (like Matt) can get good power gains out of a car (particularly the turbos) relatively safely. But be aware that pushing more power DOES put more stress on the engine and drivetrain, and if any of it wasn't in good condition to start with, you may start to see the issues more obviously. That's one reason why good tuners insist that you fix any known issues with the car before they start making changes (Matt as an example runs a scan over the ECU, or gets you to if you have the right gear, and gets you to fix anything that he feels needs addressing). Some tuners advise replacing stock components such as the fuel pump with a higher-flow device (dw65c for example, that fits into the stock fuel filter basket) to give additional headroom.
The comment about not running S# may have been when a change is made to the running gear (dump pipe, exhaust, intake, turbo, intercooler, etc) that wasn't present when the tune was done, as these can change important parameters on which the engine tune depends. Running in only S or I mode runs lower boost levels, which are safer, and less likely to cause a significant issue.
For an auto, after a tune how does the engine react if you just flat foot it?
Is there any improvement in the manual use of an auto? More immediate changes?
To start with, your in-gear acceleration should be better after a tune than it was before. Matt's tunes help the gearbox to work better too, by feeding the TCU (transmission control unit, effectively the computer that controls your transmission) good data for it to make decisions based on.
Manually selected changes do seem faster than before, yes.
What is the expected power increase from a tune?
How long is a piece of string? It depends on many factors, most of which are relatively unique to your particular car. Stock, the GT Spec.B is rated at 180kW at the flywheel, or about 135kW at the wheels. Without hardware changes (ie just a tune), you'd expect 150kW at the wheels. Minor changes (intake and exhaust) would take you to ~165kW at the wheels (all things being well). My car has:
- VF52 turbo
- Kobe motorsport intake hoses (from stock airbox to turbo)
- Process West TMIC
- Pierburg 3-port boost controller
- dw65c fuel pump
- Invidia 3" dump pipe with high-flo catalytic converter
- TCP 3" center/Y-pipe
- STI mufflers
- (There's other stuff, but it's not going to impact my killerwasps)
And I'm apparently (according to airflow readings) getting roughly 200kW at the wheels running 18psi boost (to be confirmed on a dyno).
Back again in a few weeks 
