I was wondering how much power can a s4 t2 rear iron handle before braking my set up at the most will be making 350-370whp I just want to make sure that the iron can hold that without stressing too much.

 

Breaking the rear iron is not a power level issue, it's a detonation issue. Up until 400HP there's no reason to worry.

 

so after 400hp what do you do

 

pay more attention

then the bigger problems become heat management and making the system as a whole work as effciently as possible to minimize stress, but don't take 400whp as an iron clad rule, its just that above that the internal streeses are getting high, but every setup varies.

 

S5 iron, they were strengthened by casting the spot where it breaks thicker. You shouldn't need it if the car is tuned right though.

 

my s4 iron broke around dowel with no detonation or any other issues at about 400 hp.....

 

so an S5 or and S6 iron would be my best bet for over 400hp

 

The RE and REW dowel lands are the largest, the REW has a fewe more advantages overall though as an engine IMO.

 

Look into aux injection along with good tuning.

If you could stand to replace the iron with something stronger, do that as well but meth/alk/water injection lowers egt's and ait's like you wouldn't believe. You can make your own kit for under $300.

 

or buy the aem hd kit for under 500$ and have full tunability with maps for rpm, pressure levels and temps. and it includes the retarded huge 5 gal tank so you dont have to refill it every trip

 

just go with the s5 iron if you are rebuilding. I broke mine at about 320 rwhp

 

Keep in mind that there are 2 different types of S5 rear irons. One has a small reinforcement to the dowel casting, the other has a much larger overall dowel casting, (same size as REW and late RE, 20B blocks)

 

"Pay attention" is the exact answer.

There are some ECUs commonly used that are prone to ignition noise more then others. If you have one of those ECUs, then it's VERY important to insure you are not getting noise on the CAS signal. If you are, it's not huge deal sub-400HP. But at higher levels, you're going to end up firing into the compression stroke of a very volatile mixture and you'll crack an iron easily. Most people who break irons and were smart enough to datalog their runs end up seeing some big RPM spikes right around the time the iron broke. That's noise.

All the AI and tuning in the world won't do a thing if your ECU is trying to fire the engine as if it was running 19,000 RPM when it's just coming up on 6,000 RPM.

 

I think my s4 rear iron was a factory freak. I detonated the **** out of it. Multiple times. I cracked a corner seal from the last mishap, but the rear iron was still holding on strong. that was at 21 psi on a T04S 60-1 . my lower boost dyno was 386rwhp.

 

Just lost mine and I had very little knock. Not even close to pre-ignition. I estimate I am putting out about 370rwhp.

 

this thread gives me worries.. i'm looking at mid 400s with s4 irons, is it really that fragile?

 

I've been mid 400s at the engine with S4 irons for 2.5 years.

Hell, just getting to work this morning I took a turn too tight which caused my fuel pump to suck air at around 10 PSI. Engine pinged, backfired, chugged and then went right back to normal.

Note to self: sump tank.

 

it almost seems like some batches of s4 irons are stronger than others. mine and aaron's have taken detonation fine, and other peoples seem to be glass. I can tell you this though, the s5 and s6 (FD) irons are more consistently durable.

 

S4 irons are pretty hardy, but they will fail structurally at higher HP levels no matter HOW safe you try to make it.

I was running mine at around 427 ish HP when I lost the wastegate line. Boost spike to 30 PSI but NO detonation and that cracked the land. My guess is it was somewhere in the 500 ish range when it puked.

you CAN however, keep that alive at 400 hp. Many of us have done it.