BREAKING NEWS! Complete Exhaust Stack Re-Design

Discussion in 'Chevy' started by TXFlyGuy, Nov 27, 2019.

Help Support HomeBuiltAirplanes Forum by donating:

  1. Nov 27, 2019 #1

    TXFlyGuy

    TXFlyGuy

    TXFlyGuy

    Well-Known Member

    Joined:
    Apr 26, 2012
    Messages:
    1,543
    Likes Received:
    451
    Location:
    Republic of Texas
    Here is what we have learned...

    There is a major loss of power, both torque, and horsepower, using the Titan short stack exhaust. This starts to occur at 3000 rpm and above. Hutter Performance was really scratching their heads on this one, and it is purely due to the design. Titan purposely blocked off part of the exhaust port in order to reduce the power output from the LS3.

    After a long conversation with Trevor (Hutter Performance), and Ron Dalin, we have decided to fabricate an all new exhaust, with the correct port sizing to match the exhaust manifold. In addition, Trevor wants to increase the diameter of the pipes, and add just a little extension from the current length.

    As the Titan exhaust is actually a but undersized, we feel the new design will actually improve the looks from a cosmetic standpoint.

    And Trevor is certain that we can regain a good amount of the lost power from the LS3. Hutter will be making an all new stainless steel exhaust. And keeping it true to appearance for a P-51 look.

    The increase in power will allow us to cruise at altitude at a reduced rpm setting, while still getting the power we desire. This will result in added engine longevity, quieter cockpit, and reduced fuel burn. If you want to go all out, and race your Mustang, having the high performance exhaust is what you will want. If you want to fly at slower rpm settings, and still have good power, the high performance exhaust is what you want.

    Anyone currently flying a T-51 Mustang with an LS3 might want to look into this.
     
    Last edited: Nov 27, 2019
    ScaleBirdsScott likes this.
  2. Jan 8, 2020 #2

    TXFlyGuy

    TXFlyGuy

    TXFlyGuy

    Well-Known Member

    Joined:
    Apr 26, 2012
    Messages:
    1,543
    Likes Received:
    451
    Location:
    Republic of Texas
    Here ya go, the latest photo updates from Hutter Performance. These pipes are 1.75" diameter. The Titan pipes are 1.25". A P-51 exhaust tube is 2.0" diameter.
    Yes, the two "dummy" pipes will go forward of the live pipes.
    1AACF686-73FA-468C-A24C-5ED895684E31.jpg
    7DCDBAEC-5D85-456B-A2E3-FC003956D977.jpg

    50817CE5-0C6F-42F5-95B3-3538AF91BEF4.jpg
     
    raymondbird, fly2kads and cluttonfred like this.
  3. Jan 8, 2020 #3

    BJC

    BJC

    BJC

    Well-Known Member HBA Supporter

    Joined:
    Oct 7, 2013
    Messages:
    10,010
    Likes Received:
    6,759
    Location:
    97FL, Florida, USA
    Darn, Tex, I read the first part of the thread title, and thought, “Tex flew the T-51.”


    BJC
     
  4. Jan 8, 2020 #4

    TXFlyGuy

    TXFlyGuy

    TXFlyGuy

    Well-Known Member

    Joined:
    Apr 26, 2012
    Messages:
    1,543
    Likes Received:
    451
    Location:
    Republic of Texas
    Right now, we appear to be on track for test flights early April (2020).
     
    BJC likes this.
  5. Jan 9, 2020 #5

    Voidhawk9

    Voidhawk9

    Voidhawk9

    Well-Known Member HBA Supporter

    Joined:
    Mar 26, 2012
    Messages:
    265
    Likes Received:
    151
    Location:
    Timaru, NZ
    He doesn't want to fly it, he just likes spending money on it!
    j/k, looking great!
     
    bmcj likes this.
  6. Jan 9, 2020 #6

    bmcj

    bmcj

    bmcj

    Well-Known Member HBA Supporter

    Joined:
    Apr 10, 2007
    Messages:
    13,075
    Likes Received:
    5,005
    Location:
    Fresno, California
    So why would they constrict the flow rather than optimize power output?
     
  7. Jan 9, 2020 #7

    TXFlyGuy

    TXFlyGuy

    TXFlyGuy

    Well-Known Member

    Joined:
    Apr 26, 2012
    Messages:
    1,543
    Likes Received:
    451
    Location:
    Republic of Texas
    This header will flow much better, with larger diameter pipes, and with zero exhaust port blockage. The Titan header blocks off the ports.
    We will know next week after they do another dyno run with this new exhaust.

    It would appear that the original design was not properly engineered, according to Hutter Performance. Titan was under the impression that by blocking off the exhaust ports at the head, and restricting the pipe size, you could get more torque at low rpm. Hutter does not agree. And Dale Earnhardt won back-to-back championships running engines built by Hutter.
     
  8. Jan 9, 2020 #8

    BJC

    BJC

    BJC

    Well-Known Member HBA Supporter

    Joined:
    Oct 7, 2013
    Messages:
    10,010
    Likes Received:
    6,759
    Location:
    97FL, Florida, USA
  9. Jan 11, 2020 at 1:30 PM #9

    TXFlyGuy

    TXFlyGuy

    TXFlyGuy

    Well-Known Member

    Joined:
    Apr 26, 2012
    Messages:
    1,543
    Likes Received:
    451
    Location:
    Republic of Texas
    Found this...some good reading on exhaust design, and header pipe diameter:

    Exhaust Design Comments:
    The concept that maximum power is obtained by zero pressure in the exhaust is only partially true. There should be absolutely
    no back-pressure from the collector rearward, but the diameter of the system beginning with the exhaust valve is a compromise. The highest efficiency for the system requires a minimum speed for good exhaust gas velocity to insure that
    gas does not "back up" into the chamber during overlap at low engine speeds, and that the "suction" (negative pressure pulse) effect of a resonant (tuned length) and/or collector (overlapping exhaust pulses) system is optimized.

    To predict what primary size will be best for a specific motor, you must know where you want the engine to develop peak torque. If the existing torque peak is at bit lower RPM than you prefer (typical in under-cammed or stock motors), it can be "bumped" a bit by increasing the primary diameter. If the torque peak is too high (motor is "peaky", with no range and poor recovery from
    gear changes), the peak can be adjusted down by using a smaller pipe. A change of 1/8" in the primary diameter will raise or lower the peak torque RPM by 500 or so.

    This factor slightly overlaps the effect of primary pipe length, but the pipe length generally will not change the peak torque or the RPM at which it occurs. A length change has the effect of improving the torque on only 1 side of the peak by "borrowing" it from the other side. A shorter pipe improves the torque after the peak (reduces it at lower RPM), preventing the curve from
    flattening out so quickly as speed increases.

    A longer pipe extends the torque curve backwards to improve the engine's flexibility, at the expense of after-peak torque. Less stall speed is required, and the motor will pull taller gears; this re-tunes a 4-speed motor for better operation with Torqueflite, etc.
    For best effect, the gas speed in the primary tube at the peak torque RPM should be about 240 feet per second. The formula to calculate pipe size is:
    Area of Primary Pipe = RPM ? Cylinder Size ? 88,200

    This determines the pipe's cross-sectional area, from which we can calculate the ID. Typical exhaust pipes are 18ga. (wall thickness of .049"), so the OD will be .098" larger. From this we can construct a formula for an 8 cylinder motor, and factor in the 18ga. wall thickness:

    Area of Primary Pipe = RPM ? Motor Size ? 705,600
    Pipe ID2 = RPM ? Motor Size ? 705,600 ? .7854
    Pipe ID2 = RPM ? Motor Size ? 554,177
    ID = (RPM ? Motor Size ? 554,177).5
    OD = (RPM ? Motor Size ? 554,177).5 + .098"

    Remember that your peak torque RPM will always be lower than your peak HP
    RPM. The separation between peak torque and peak power is roughly
    proportionate to your range of useable power (wider is better). Be realistic in your
    estimates and plans - peak torque @ 7000 RPM sounds good, but is almost certainly
    beyond the breathing ability of even a professionally-built race motor, and if
    true will make the car impossible to launch. Note that 1-1/2" pipe is large
    enough for a 273" motor with max torque @ 4000 RPM. A 360" only needs 1-3/4"
    for 4200 RPM. A 440" is fine @ 4500 RPM with 2" primaries.

    If choosing pipes for a 4WD, van, towing, etc. keep the size small to
    improve torque where you need it most - the lower RPM ranges, typically 2500-3500.
    One exception where use of a larger pipe (than indicated by the above
    formula) will help power is, of course, motors using nitrous oxide, supercharger
    or turbocharger. In these cases, size the pipe for the expected peak torque,
    not the motor size.

    Another instance where a slightly larger pipe may help is where the
    departure angle of the pipe from the flange is very sharp (typically downward). The
    added cross-sectional area immediately after the flange apparently helps
    reduce the restrictive effect of a small radius after the port. This partially
    explains why some header models or brands work better than others with similar
    dimensions.

    As far as ability of an exhaust system to flow enough air for a given amount of horsepower without causing significant back pressure, this is from one of David Vizard's books:

    1. For avoiding significant restriction from back pressure, the pipe should flow at least 2.2CFM per horsepower produced.

    2. A straight pipe will flow ~115CFM per square inch of area (using inside diameter of the pipe)

    Recommended Header Primary Tube Diameter:

    Horsepower / Primary Tube Diameter
    200-325 hp. - 1 1/2 in.
    275-425 hp. - 1 5/8 in.
    400-500 hp. - 1 3/4 in. or 1 7/8 in.
    500-Plus hp. - 2.0 in. or larger

    It would appear that Hutter Performance is right on the money with the choice of a 1.75" diameter header pipe.
     
    Last edited: Jan 11, 2020 at 4:27 PM
    raymondbird likes this.
  10. Jan 13, 2020 at 11:32 PM #10

    TXFlyGuy

    TXFlyGuy

    TXFlyGuy

    Well-Known Member

    Joined:
    Apr 26, 2012
    Messages:
    1,543
    Likes Received:
    451
    Location:
    Republic of Texas
    Just got this update from Hutter Performance...and she is a thing to behold!
    Just feast your eyes on this beauty!
    4E92A19D-BE2B-4E24-8E02-B9FC92292A97.jpg
     
    raymondbird, delta and mcrae0104 like this.
  11. Jan 15, 2020 at 2:42 AM #11

    GeorgeG

    GeorgeG

    GeorgeG

    Member

    Joined:
    Jan 8, 2019
    Messages:
    16
    Likes Received:
    0
    Location:
    Tracy, CA, USA
    That's almost as pretty as the El Camino!
     
  12. Jan 15, 2020 at 1:07 PM #12

    TXFlyGuy

    TXFlyGuy

    TXFlyGuy

    Well-Known Member

    Joined:
    Apr 26, 2012
    Messages:
    1,543
    Likes Received:
    451
    Location:
    Republic of Texas
    Hutter Performance has no shortage of exotic autos that come through their shop.
     
  13. Jan 15, 2020 at 9:36 PM #13

    Lendo

    Lendo

    Lendo

    Well-Known Member

    Joined:
    Feb 7, 2013
    Messages:
    375
    Likes Received:
    67
    Location:
    Brisbane
    Love it!
    George
     
  14. Jan 16, 2020 at 12:31 PM #14

    TXFlyGuy

    TXFlyGuy

    TXFlyGuy

    Well-Known Member

    Joined:
    Apr 26, 2012
    Messages:
    1,543
    Likes Received:
    451
    Location:
    Republic of Texas
    El Caminar - Spanish translation = The Road.

    Dyno testing to resume today or tomorrow. Hoping for some very good numbers.
     

Share This Page



arrow_white