2.5 RS Max boost PSI

Discussion in 'General Subaru Discussion' started by Bielke55, Oct 27, 2005.

  1. Bielke55
    Offline

    Bielke55 Well-Known Member

    Likes Received:
    66
    Trophy Points:
    283
    Does Anyone Know what the max PSI a 2.5 RS Motor can with stand before things get messy? i have a boosted 2.5RS, that i want to increase boost to 7 or 8 but im unsure of its limits. If anyone knows please let me know. Thanks

    -B
     
  2. hercules
    Offline

    hercules New Member

    Likes Received:
    1
    Trophy Points:
    0
    im like boosting 15 in my 2.0 RS...but im sure zola or Russ should know the answer to that....btw what kind of FMIC is that???
     
  3. WRX1
    Offline

    WRX1 _ Staff Member

    Likes Received:
    722
    Trophy Points:
    348
    What kind/ how big is your ic? Do you have a ic? What kinda of engine management do you have? Do you have a way to increase your fuel flow and decrease your timing?

    Russ
     
  4. AWDimprezaL
    Offline

    AWDimprezaL has more posts than you

    Likes Received:
    1,818
    Trophy Points:
    573
    ive heard 8-10 is pushing it, kelly has a boosted RS, phatsuby has a boosted 2.5 in his lgt.
     
  5. esperunit
    Offline

    esperunit Well-Known Member

    Likes Received:
    11
    Trophy Points:
    223
    8-10 is pushing it.

    That's not really the engine setup to have if you are the kind of person who wnats to tuen up the boost one day. Running 8+ psi will cause that engine to blow sooner or later. Some people swear they run 8 all the time, but nobody swears they run 10.
     
  6. Zola
    Offline

    Zola Well-Known Member

    Likes Received:
    0
    Trophy Points:
    121
    Totally depends on which turbo you have on there and your state of tune, there is no magic maximum boost pressure number.
     
  7. RallyNavvie
    Offline

    RallyNavvie Well-Known Member

    Likes Received:
    12
    Trophy Points:
    223
    Where the hell do all these RS turbos come from these days? Like they grow on trees, I swear...

    Anyway your "safe" number for stock internals AND decent engine management is 5psi. I guess I never understood why people would want to take the chance of blowing up their engine by going beyond that without putting more work into the engine when 5psi makes the high-CR n/a plant pretty damn quick. At least it felt a lot quicker than my GT does.

    You can push to 8-10psi on stock internals ONLY if you're running proper engine management. I had a Haltech E6K in mine, or there's the TEC-II or 3 (which I don't recommend because I don't think either had air temp correction maps), or the Link. Look under the engine management sticky thread at NASIOC, it has a comparison of several geared more toward aftermarket turbos.

    Once you start changing out internals you may as well just get an STi 2.5 block and build on that. You'll get far better reliability from it and be able to do greater things with it and you'll end up spending only slightly more for the new block. If you can sell your old one so much the better.

    We'll finally get to see dyno results on my old car in the near future. The new owner was already down at RS to tune but their laptop couldn't read from the E6K properly so he had to come back later. I'm kinda curious just to see what my numbers were from the rough tune Todd and I did for it.
     
  8. readymix
    Offline

    readymix ...Lest ye be trod upon... Staff Member

    Likes Received:
    2,890
    Trophy Points:
    473
    Hey, when you blow your motor, can you sell me your crankshaft?
     
  9. Yang
    Offline

    Yang Well-Known Member

    Likes Received:
    3
    Trophy Points:
    223
    I may have one soon :lol:
     
  10. readymix
    Offline

    readymix ...Lest ye be trod upon... Staff Member

    Likes Received:
    2,890
    Trophy Points:
    473
    2.5L Phase 1 Crankshaft?
     
  11. Dynapar
    Offline

    Dynapar Well-Known Member

    Likes Received:
    30
    Trophy Points:
    358
    it sounds like 6 is what works the best. however with proper tuning / hardware you can do 10. although from what i have heard 8 works the best as far as $$$/Power goes. since you can caress the extra 2 psi fairly easily, and without major issue (so i hear).
     
  12. WRX1
    Offline

    WRX1 _ Staff Member

    Likes Received:
    722
    Trophy Points:
    348
    Ok, there is alot of mis-information going around. You can run 20psi, but you need to have PROPER EM. You need full control of your of your fueling AND timing. Remeber, the more boost you run the less timing you can run. So yes, you can run 20psi, but you timing is going to be VERY low. There is a happy place in the middle, and that will depend on all your supporting mods and em. Most rs's run 5-8 with fair em. Rallynavvie could have ran more boost with his haltec, but his ic was kinda holding him back. What ic are you running? What em are you running (or plan on running)??

    Russ
     
  13. snbrd4evr
    Offline

    snbrd4evr Well-Known Member

    Likes Received:
    3
    Trophy Points:
    123
    I can't tell if you're serious or just joking. I'm sure the motor could run 20 psi... for 10 seconds :lol:

    I have hit 9 psi in my car for a few full runs and it was ready to explode. I could feel the heat through the vents. Right now I'm running around 5-6 on wastegate and between 7-8 when the solenoid is turned on. Right now I have a hydra for engine management (it's a full standalone that's plug and play). I ran 4-5 psi for a long period of time just to get used to how tuning works and how the car will react to different changes.

    Before we can give you any good recommendations, you need to tell us what turbo you're running, what engine management, what intercooler, and what phase motor you have.
     
  14. FuJi K
    Offline

    FuJi K Well-Known Member

    Likes Received:
    121
    Trophy Points:
    248
    20psi with race gas is do-able with good engine management. It's just the rods and pictons will go boom just because they're not strong enough.

    You can go 16psi just fine with like said, godo tuning. There's been a few in the past that put 12psi and run 12's in the 1320.

    Get the fuel their and you'll be safe. It's just that when you're having that much pressure in the cylinders, the rod and pistons may not hold, even though you have good tuning....you might just throw a rod bearing.
     
  15. Bielke55
    Offline

    Bielke55 Well-Known Member

    Likes Received:
    66
    Trophy Points:
    283
    Wow thanks everyone for the help!! Im running a garrett T28BB. with custom everything basically. The Kit was not bolt-on like it said. For EM im using Hydra Nemesis and Ronnie as my dyno and tuner. im running at 4PSI right now. I ordered larger Fuel injectors because my stock ones are maxed out. Im having some boost leak problems though, cause at 1,200RPMs the boost is 6. But then at 5,500 it drops to 4. Its been one thing after another. Im looking for more parts if anyone is selling please let me know
     
  16. BlackDubRX
    Offline

    BlackDubRX New Member

    Likes Received:
    0
    Trophy Points:
    0
    I've run 35 psi on stock head studs/no EM but fuel. :lol:
    And yes, he is serious. There is no magical number that your car will explode at. Only if certain conditions are met, and lean is certainly one of them. It all really comes down to your setup.
     
  17. RallyNavvie
    Offline

    RallyNavvie Well-Known Member

    Likes Received:
    12
    Trophy Points:
    223
    You boost shouldn't even be coming on at 1200rpm. That's, like, 200rpm more than what my idle was set at.

    Also your stock RS injectors are NOT maxed out running less than 6psi. It was generally accepted that after 5psi you look to larger injectors, and even then you don't need to go crazy on massive ones. If you're keeping it to around 10psi then perhaps 350cc injectors should work. Best thing you can do is have an engine computer that supports staged injectors ;)

    And as for running 20lbs on the stock 10.5:1 RS plant I'm pretty sure no amount of tuning, unless it's firing when the exhaust valves are open, would allow that motor to survive. I mean there is a limit to what the engine internals can take. I think I recall seeing someone run 12psi on stock internals with a Link ECU but even that one went after a few months. As I said, I would steer clear of anything more than 8-10psi on stock internals and only then with proper engine management (i.e. no piggybacks).
     
  18. snbrd4evr
    Offline

    snbrd4evr Well-Known Member

    Likes Received:
    3
    Trophy Points:
    123
    You've run 35 psi on a stock 2.5RS block and it didn't explode? From what I've always read, if you want to drive your car daily you should run at most 6psi if you have a rrfpr and a voltage clamp, or run 8-10 psi if you're running a standalone. Even 8-10 is pushing it, the block isn't strong at all and is known to warp the cylinder walls under high boost and blow the rings out.

    You have good engine mangement and a good turbo, I'd suggest running 6-7 for a while and have it tuned. What injectors are you planning on running? I'm running RC550's and they're doing well even for brief moments around 8 psi. Good luck with everything and I hope we all helped helped you.
     
  19. AWDimprezaL
    Offline

    AWDimprezaL has more posts than you

    Likes Received:
    1,818
    Trophy Points:
    573
    kelly your car is wicked, the backfires rule pretty well too
     
  20. WRX1
    Offline

    WRX1 _ Staff Member

    Likes Received:
    722
    Trophy Points:
    348
    you need to remember that turbo diesel's are around 20-25:1 compressions and are running 35-80psi of boost. I also never said at 20psi you would be able to run 20 degrees of advance. Like I said, there is a happy medium between boost and timing that needs to be found. If you read up on some of the tunning posts you will see that some people run alot of boost and a little timing and other are the complete opposite.

    Russ
     
  21. snbrd4evr
    Offline

    snbrd4evr Well-Known Member

    Likes Received:
    3
    Trophy Points:
    123
    Very true, but this block isn't strong enough to handle 20 psi even if the timing is retarded down to 8 or something. It's a matter of the internals holding the pressure. I could see 20 psi in one short burst. But with these blocks, it's just smarter to run 6-8 psi and retard the timing a little bit if you're going to be using it as a daily driver. If you don't believe me, you should check out some of the threads over on rs25.com, anything over 10 psi lasted less than half a year and that was with crazy tuning. I'm not saying you're completely wrong, just that it's not very smart to try to run a stock 2.5RS block at 20 psi daily.

    Thanks :D
     
  22. Bielke55
    Offline

    Bielke55 Well-Known Member

    Likes Received:
    66
    Trophy Points:
    283
    So in case anyone is curious ever... 10 PSI on a N/A 251 Block is PUSHING the limits of the block...
     
  23. AWDimprezaL
    Offline

    AWDimprezaL has more posts than you

    Likes Received:
    1,818
    Trophy Points:
    573
    Ahahahahahaa
     
  24. snbrd4evr
    Offline

    snbrd4evr Well-Known Member

    Likes Received:
    3
    Trophy Points:
    123
    I was right!!! :laugh:
     
  25. Shibbs
    Offline

    Shibbs The Daywalker

    Likes Received:
    74
    Trophy Points:
    283
    lol 3+ year bump.
     
  26. qstarin
    Offline

    qstarin Well-Known Member

    Likes Received:
    17
    Trophy Points:
    123
    def nice bump!
     
  27. RallyNavvie
    Offline

    RallyNavvie Well-Known Member

    Likes Received:
    12
    Trophy Points:
    223
    And yet I don't miss that turbo RS of mine at all, every day wondering if this was the day I was going to shred the transmission. Oh wait I do miss it :)
     
  28. RichWRX
    Offline

    RichWRX Well-Known Member

    Likes Received:
    53
    Trophy Points:
    233
    30lbs :)
     
  29. ShortytheFirefighter
    Offline

    ShortytheFirefighter Pokemans. I has none. Staff Member

    Likes Received:
    1,571
    Trophy Points:
    398
    DING!

    Fries are done!

    So, catastropic failure or what?
     
  30. AWDimprezaL
    Offline

    AWDimprezaL has more posts than you

    Likes Received:
    1,818
    Trophy Points:
    573
    It still ran, with part of a piston. Furthermore that piston was completely washed? cracked head perhaps?
     
  31. Bielke55
    Offline

    Bielke55 Well-Known Member

    Likes Received:
    66
    Trophy Points:
    283
    [​IMG]
     
  32. RallyNavvie
    Offline

    RallyNavvie Well-Known Member

    Likes Received:
    12
    Trophy Points:
    223
    Epic.
     
  33. ShortytheFirefighter
    Offline

    ShortytheFirefighter Pokemans. I has none. Staff Member

    Likes Received:
    1,571
    Trophy Points:
    398
    (whistle)

    Ouchie. How bad is the head on that side?
     
  34. Bielke55
    Offline

    Bielke55 Well-Known Member

    Likes Received:
    66
    Trophy Points:
    283
    Head and valves were just fine. It was weird there was nothing to be found...
     
  35. blackozone
    Offline

    blackozone Well-Known Member

    Likes Received:
    1,010
    Trophy Points:
    348
    LOL! Piston bits, NOM NOM NOM!!!
     
  36. ShortytheFirefighter
    Offline

    ShortytheFirefighter Pokemans. I has none. Staff Member

    Likes Received:
    1,571
    Trophy Points:
    398
    Wow. That's insane.

    I have to wonder where that chunk went.
     
  37. Bielke55
    Offline

    Bielke55 Well-Known Member

    Likes Received:
    66
    Trophy Points:
    283
    My guess is that it exploded into small enough pieces and passed through the valves and through an opened wastegate
     
  38. Snowbum
    Offline

    Snowbum Well-Known Member

    Likes Received:
    0
    Trophy Points:
    101
    I wonder what noises you'd hear if the wastegate was closed :)

    LOL Nice bump doood!!
     
  39. wrexinator03
    Offline

    wrexinator03 Banana Cream

    Likes Received:
    8
    Trophy Points:
    223
    BOOMmm