your take on BOV's and WG's

Forced Induction Mopar

  1. CUDAGUY

    CUDAGUY aka Prince Valiant

    Messages:
    613
    Likes Received:
    4
    Joined:
    Apr 30, 2009
    Location:
    Portland,OR
    Local Time:
    6:10 PM
    I have access to a 6.7L cummins turbo (HX40 ???) that Im thinking would be fun to throw in the 273 in my wagon. What should I use to control it? Im familiar with small engines and turbos (neon and SRT-4) but controling something this big is rather intimidating. Im only shooting for 12-14 pound of boost due to the stock internals.

    any info helps!
     
  2. 1970Duster

    1970Duster Well-Known Member

    Messages:
    6,660
    Likes Received:
    92
    Joined:
    May 30, 2010
    Local Time:
    6:10 PM
    If you have stock internals the most your looking at is 6 to 8 pounds of boost, and I'd still use a WG or Blow off valve though.
     
  3. CUDAGUY

    CUDAGUY aka Prince Valiant

    Messages:
    613
    Likes Received:
    4
    Joined:
    Apr 30, 2009
    Location:
    Portland,OR
    Local Time:
    6:10 PM
    they are forged internals with the exception of BEEFY cast pistons, lotsa neon guys running stock puny cast pistons with 10-12 pounds....not to concerned about the 273.
     
  4. 1970Duster

    1970Duster Well-Known Member

    Messages:
    6,660
    Likes Received:
    92
    Joined:
    May 30, 2010
    Local Time:
    6:10 PM
    If you just bolt the system on without addressing the piston rings and run the boost your talking you'll mess you stuff up quick. The boost you want need the piston rings to be addressed for a different setup and if your at that point I'd also put in forged pistons (I'm using Ross Racing pistons, the are a 1/16, 1/16, 3/16 ring setup and the pistons are designed to handle a lot more boost then what your after, I reccomend them).
     
  5. TT'74

    TT'74 Well-Known Member

    Messages:
    136
    Likes Received:
    3
    Joined:
    Feb 17, 2009
    Location:
    Orlando, Fl
    Local Time:
    9:10 PM
    What are you suggesting he address with the piston rings? The only concern I would have with the rings would be insuring that they have an adequate spacing below the top of the piston so that if a slight bit of detonation happens during tuning the pistons won't chunk. If the rings aren't mounted too high I don't see a problem with 10-14 PSI on stock stuff.
    In my experience stock internals will hold up to a lot more than the aftermarket will lead you to believe.
     
  6. dgc333

    dgc333 Well-Known Member

    Messages:
    4,124
    Likes Received:
    27
    Joined:
    Jan 12, 2005
    Location:
    Pembroke, MA
    Local Time:
    9:10 PM
    You need a waste gate to control the level of boost from a turbo period. If the turbo only produced the desired boost at max rpm it would produce little or no boost below max rpm. You size the turbo to produce the desired boost low in the rpm range then use the waste gate to prevent over boost higher in the rpm range.

    A Blow Off Valve is used when you have the throttle in between the output of the turbo compressor and the engine. When you close the throttle of a blow through system it creates a pressure spike that travels back into the turbo compressor and stops the compressor from spinning and rattles the bearings. The BOV releaves this pressure spike which allows the turbo to keep spinning and protects the bearings from Damage. The reason you want the turbo to keep spinning is it reduces turbo lag when you open the throttle again.

    I don't know anything about the Cummins turbo but for all around driveability and perfromance it is important to size the turbo correctly. One from a 3.8L (231 cid) Buick V6 would likely be a better match to your 273 than the Cummins turbo.
     
  7. CUDAGUY

    CUDAGUY aka Prince Valiant

    Messages:
    613
    Likes Received:
    4
    Joined:
    Apr 30, 2009
    Location:
    Portland,OR
    Local Time:
    6:10 PM
    Im familiar what they are and what they do as well as the fact that Im gonna need both, Im just not sure if the sizes should be any different, or if I should be running a wastegate on each bank or one just before the turbo.

    The intention is to stay nearly completely out of boost untill atleast 3500 while under cruise/light throttle.....no more than a pound or two, simply to keep the cars current street manners.
     
  8. Bill Dedman

    Bill Dedman bill dedman Legendary Member

    Messages:
    3,997
    Likes Received:
    63
    Joined:
    Oct 16, 2007
    Location:
    Conway, Arkansas
    Local Time:
    7:10 PM
    Turbocharged engines often produce more heat.... heat that expands the top two piston rings to a greater degree than a normally-aspirated engine would.

    To acommodate this increased heat, the ring end gap will likely need to be increased to an amount larger than the same engine without forced induction would require. If insufficient end-gap is present, under lots of heat, the gap totally closes and the ring tries to continue growing, and can seize in the bore, possibly damaging the bore, and sometimes literally pulling the top off the piston at the ring-land.

    Additionally, pistons that are designed for forced-induction applications, have the top ring positioned lower, with more room between the top of the piston and the top ring land. I don't know for certain, but I think its a strength issue.

    I have successfully used a set of OEM Magnum pistons in my 360 Magnum, probably because I only run 10 pounds of boost, and because when I built this junk, I didn't know any better.:angry7:

    Build a 30-psi /6 turbo motor, and you'll find out how much you DON'T know, fast... That's what Freddie and I are TRYING to do...

    I'm still learning and I have a L-O-N-G way to go.... obviously!
     
  9. CUDAGUY

    CUDAGUY aka Prince Valiant

    Messages:
    613
    Likes Received:
    4
    Joined:
    Apr 30, 2009
    Location:
    Portland,OR
    Local Time:
    6:10 PM
    I plan on freshining the engine and if the first rings on a 2-barrel piston are as far down as a 4-barrel piston as well as as beefy around the top of the piston, it should be fine. And I do realize that 2-barrel pistons are cast and 4-barrel ones are forged.
     
  10. TT'74

    TT'74 Well-Known Member

    Messages:
    136
    Likes Received:
    3
    Joined:
    Feb 17, 2009
    Location:
    Orlando, Fl
    Local Time:
    9:10 PM
    The cummins turbo should work pretty well for you with atleast a 38mm WG. However i think it will build boost under hard throttle alot faster than you're expecting it too. Mustang SVO and turbo coupes (2.3l engines) that are modified often run a single HX35. For street use it may be alright as long as you aren't running too high of RPMs. While cruising and regular driving you won't see boost at all, but if you get on it I would expect boost to come in in the lower 2000rpm mark.
     
  11. Bill Dedman

    Bill Dedman bill dedman Legendary Member

    Messages:
    3,997
    Likes Received:
    63
    Joined:
    Oct 16, 2007
    Location:
    Conway, Arkansas
    Local Time:
    7:10 PM
    I read, :read2: somewhere, in a textbook-type book (maybe Corky Bell's highly-regarded book, ("MAXIMUM BOOST") that as regards turbocharger sizing, a properly sized turbo that is sized for maximum horsepower output, won't be capable of making ANY BOOST AT ALL below halfway up the rpm scale for that engine.

    That should work for you, wouldn't it?
     
  12. Prine

    Prine A-Body Fanatic

    Messages:
    1,753
    Likes Received:
    72
    Joined:
    Feb 15, 2008
    Location:
    Oregon
    Local Time:
    8:10 PM
    I think what we are going to find out here....and I know because I used to work for Cummins....is that a HX35/40 for a 5.9L or 6.7L Diesel MAY have a T4 exhaust flange, but the A/R of the housing is AS IMPORTANT as the exhaust EXDUCER size.

    The reason is:

    A OEM Diesel has a RPM range of 900-4000 rpm.
    Bore x Stroke = 5.9L 358ci or whatever.
    And the calculations for the Amount of Air for Diesel Application.
    Yada yada.

    When you take into account 2 extra cylinders, and another 2500-3000 of desired rpm....you will see that THAT particular turbo Exhaust Housing is drastically undersized.....and will be going positive on a V8 application at or around 1800-2000 rpm, and running out of turbine flow around 4500 rpm.

    Good luck though...prove me wrong.
     
  13. Prine

    Prine A-Body Fanatic

    Messages:
    1,753
    Likes Received:
    72
    Joined:
    Feb 15, 2008
    Location:
    Oregon
    Local Time:
    8:10 PM
    I would guess that that HX40 has a 13cm or 15cm housing on it......Ideally the HX40 you would be looking for would have a 17cm twin scroll.

    Or even a HX55 with a 19cm.

    I dislike Holset Turbochargers overall because of the lack of "aftermarket support" for them....you have to dig through tons of Cummins Literature to source all the v-bands and such.

    I prefer http://www.precisionturbo.net/

    I have custom spec'd a couple from them and their support has been Top Notch.

    For a Single Turbo 273ci SBM with a target power range of 400-500rwhp on pump gas and under 14 psi with no aftercooling, I would recommend a 67mm compressor inducer, S-cover compressor housing, T4 Exhaust Flange, 70mm exhaust exducer, .96 A/R exhaust housing.

    I would use (1) 50mm chinese wastegate on the collector Preturbo.
    one with a 7psi spring in it...and get a Manual Boost Controller and a 30 psi gauge to tie it all together and monitor it.

    150gph electric fuel pump.
    Return style Bypass regulated 1/2 feed/return.
    Set at 7psi idling...rising rate 1:1 Bypass Regulator
    Holley 750 4150, Blow Through
    50mm BOV pre-Carb

    Single 3.5" Exhaust post turbo

    Wide Band tuned of course

    (I would throw in Meth Injection and crank the boost....but thats JMO)

    would be a fun ride with a 742 SG and some 2.94's or 3.23's :burnout:
     
  14. Prine

    Prine A-Body Fanatic

    Messages:
    1,753
    Likes Received:
    72
    Joined:
    Feb 15, 2008
    Location:
    Oregon
    Local Time:
    8:10 PM
    I looked up the turbo on their website that I recommended for your app.

    It has a Max Power of 750hp

    Its called a PT6776RE.
     
  15. Prine

    Prine A-Body Fanatic

    Messages:
    1,753
    Likes Received:
    72
    Joined:
    Feb 15, 2008
    Location:
    Oregon
    Local Time:
    8:10 PM
    My take on wastegates and blow-off valves are minimal.
    Size Accordingly so they arent restrictions.

    Slant 6 dual 38's or (1) 44mm
    Single Turbo SB V8.....would require Dual 38's or (1) 50mm.
    Single Turbo BB V8 Dual 44s....or Single 70mm

    Blow Off valve....needs to be 1/3 the diameter of the charge piping...3" charge piping could get away with a 30mm BOV....but 4" pipe would NEED a 50mm.

    WG and BOV are only a small part of a SYSTEM.
     
  1. This site uses cookies to help personalize content, tailor your experience and to keep you logged in if you register.
    By continuing to use this site, you are consenting to our use of cookies.