Proper mechanical diagnosis through troubleshooting

Recently we calibrated a “Blobeye” STi with a smaller turbo and a built motor.  At the time of the tune, we were greatly limited by what we thought was the turbo.  We knew that back pressure was present, in an overwhelming sense.  But without a monitor to quantify the back pressure, we could only see it’s affect on the other system components.  This was manifested as incredibly low output, with what appeared to be low airflow past the MAF sensor.  With changes in every aspect of the tune, we saw no change.  At this point we limited the car, advised the owner and waited to hear back.  The owner decided to upgrade to an STX76XL from his small previous turbocharger.

When they removed the downpipe, they found the catalytic converter had destroyed itself, wedging one part of the honeycomb into another.  This gave us the incredibly high back pressure.  We are always happy to hear, when we limit a vehicle due to unseen mechanical issues, that the owner did find and repair the issue(s).  With the new exhaust and turbo on, we made a:

178 WHP Gain!

over the previous set up.  This was on the same motor, same fuel system and other associated parts.  The only thing that changed was the parts we diagnosed as the restriction.  It is difficult to always get a diagnosis spot on.  But by following the scientific method and not bypassing steps, we can ensure the best possible diagnosis.

On a side note, the STX76 did very well!  It was a very responsive turbo for the car.  For those wanting to tap towards the 500awhp mark, it should do the trick.  It has a bit more lag than the STX71, but a worthwhile amount for the top end the 76 offers.  For quotes on parts and installation to hit your horsepower goals, send us an email or feel free to contact the shop!