I'm not saying that a forged crankshaft isn't better. It might even free up a few ponies if they reduced the weight enough because of the increased strength. And I'm sure it's more reliable than the cast nodular iron piece. But when a dozen guys are making over 500 HP on the stock crank, and at least 2 now over 600 HP on the stock crank, then you have to wonder if it's really worth the cost...

 

my awnser to your question would be 6psi is safe on stock internals because most cars come factory boosted with 6psi.and if you plan on making crazy power just go all out with over sized pistons stronger rods ect in the bottem end and a head rebuild for larger valves made out of better meterials while the head is off you might want to have it ported and polished and get a valve job if done at a shop with a flow bench cams and a port and polish job with a full exhaust and a higher flow intake you could make some serious hp a good head job cost less than a turbo setup and will put down some where from 50-70hp to the wheels. you have to make sure the engine breathes before you force air into it.

 

6 psi???What car are we talking about that is turbocharged that is only set @ 6 psi??? Most factory boosted cars stay at atmospheric bar for 14.6 psi so closer to 12-14 than 6...now supercharged cars can see 6-12 on average from the factory and some a lot higher. the engine will breathe well enough to run about 6-8 psi on stock motor depending on the turbo so breathing isnt an issue....its the stock components RODS AND PISTONS that suffer the most from the torque generated by boosting b/c CR should be at around 8: s rather then 10:s or 11:s b/c the compressed air raises the power significantly to generate a lot of problems for the stock internals....

 

the stock turbo on the SRT-4 runs from 11 to 14 psi, you should be safe in that zone. Anything above 200 HP and I'd start replacing some of the stock internals. For the best results, I'd buy everything as a kit, if you can afford it.

 

What the...? The SRT-4 is also a 2.4L with forged pistons and rods stock. You might as well compare the Evolution or a 911...

Both Hahn and CF come with Mitsubishi S16G or S20g turbos. Most other DIY setups use comparable turbos like a T3/T4 hybrid. With those on the stock engine and stock PCM, I wouldn't go above 6 psi untuned. Once you get it on a dyno, you could probably run closer to 8 psi, but you'll only know for sure when you get it done. Adding a timing retard unit, more appropriate camshaft, and more tuning time would get you more in the 10+ psi range. But the cast pistons and rods are still the breaking point 90% of the time. 200 HP at the crank shouldn't be a problem. In fact, it's not the HP that bends rods and breaks pistons, it's torque. And the magic number seems to fall in the 225-235 ft-lb range.