Right now I'm running the stage 2 cobb map on my 04 wrx. So I already have a catless TBE and uppipe. I'm planning on going with an 18g setup in the near future. Do I need to upgrade the internals or can it be safely tuned on the stock bottom end? The setup I want to go with is: deadbolt 18g PE 650cc Walbro 255 Spearco TMIC/ or a FMIC (haven't decided yet) I already have the Accessport so I'm also planning to get a protune done. A guy at work has recommended Topspeed, he got his Legacy tuned there. I've heard good things about them.
I'm not sure if those injectors will be big enough for an 18G. As far as internals, you should be alright for a little while. Running a lot of boost and holding it to redline is bad on the piston rings. I'd worry more about the transmission with all of that power. Topspeed is a great shop and a site sponsor, they come highly recommended by almost everybody on the site.
Your tranny should be fine as long as you dont beat on it. I've been doing alot of reading on the 2002-2003 tranny problems and almost all of them stem from speed shifting between 1-2, 2-3, and high power launches. As long as you dont do that, there is a guyon clubwrx making over 320 to the wheels with a 20g on the stock tranny, and he has been on that setup for over 20K miles. I'm sure a few launches are ok, as long as you aren't revving it to 5K+ then dropping the clutch.
longevity of the engine will depend on how aggressive the tune is... im also wondering whether those injectors will be adequate
I think the injectors will be able to hold, considering I believe the 800-900 CC injectors run at 68% duty generally on an 18G. They'll be at the very end though, so I would advise going with larger ones. Which IC do you really want? FMIC or TMIC ?
I'm more concerned with the piston rings and the pistons. How reliable can the stockers be with an 18g on it. It's a daily driver and I don't want to be repairing the engine anytime soon. And TMIC vs FMIC, I can't decide. I drive from a little south of Atlanta to Ashford Dunwoody every morning. There's a lot of road junk that beats the hell out of your car. I got my windshield cracked within 3 months of owning of the car. I don't want to pay >1k for a nice piece of equipment to get beat up by dump truck rocks. So I may just sacrifice some power for longetivity and get a nice TMIC.
I bet a decent bar & plate core front mount wouldn't get beat up too badly. Hell, you can put some heavy gauge mesh in front of it (it could look good) to protect it.
A larger TMIC would be fine for an 18g. However, I would recommend on getting the FMIC so that you have more options on future upgrades. The 650's will be more than enough for the 18g and would be at the limit of a 20g. With alcohol injection they would probably be enough for an sz49 or FPGreen. If you need more room you can always bump the fuel pressure some. Be nice to your transmission and it will be fine. I am running 356whp/387tq on a stock 02 tranny and have no issues.