Do You Need A Tune Before/When You Get An Exhaust?

[FGXR6T-UTE]

Hey guys I was planning on getting an xforce 4" system when I get my tax back but was reading on another thread that you have to get it tuned before you get an exhaust, why? also I've already got an exhaust its custom not sure if its 3" or 3-1/2" but its a full system dump,cat etc and it hasnt been tuned so just wondering why I would need a tune with the xforce system?

[Wenier]

When you free up that restriction it can allow the turbo to overboost which could cause other issues with running lean. Your current exhaust if its only a 3" I think cant flow anymore than the stock exhaust but the cat and dump would probably be less restrictive so you may have been lucky so far.

Someone else should come on and clear it up. Honestly just get a tune and be safe dont wanna blow it up.

[IH8TOADS]

Not everyone knows what they're talking about!!

The factory tune has closed loop boost control meaning that it can adjust the wastegate duty cycle to keep boost at the "desired" boost level. Depending on your other mods, the factory tune can deal with an upgraded exhaust no problems. If you have intake mods and a big cat convertor it may be too much for the factory tune and set an overboost code. With closed loop it may spike a little on ramp up but the PI system will quickly pull out some duty cycle. If go a 4" with big cat it might be too much, especially if have have a K&N filter.

If you have a custom tune, 99% of the time the tuner will use open loop which has zero scope to bring boost back to a "desired" level. Therefore if you have a custom tune and go make even a slight change to your configuration you need to stay off boost until you go visit your tuner!