Crossover vs. stock vs. 4-1 exhaust

Discussion in 'Pitts' started by tscottmiller, Mar 7, 2017.

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  1. Mar 7, 2017 #1

    tscottmiller

    tscottmiller

    tscottmiller

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    Gang,

    We are running stock S1S with AEIO-360-B4A with stock exhaust and bungee suspension system. Is there tangible performance results moving to crossover exhaust system?? Pros & Cons.....

    Any thoughts on 4-1 performance and maintaining bungees??

    Thank you,

    Scott
     
  2. Mar 7, 2017 #2

    akt227

    akt227

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    There is a CAFE report about that. It's why I bought a 4-1 system.
     
  3. Mar 8, 2017 #3

    PittsDriver68

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    The short answer is Yes to all of the above. I have a factory crossover exhaust on my S-2A and I believe the estimates of increased horsepower over the stock system that the airplane came with. We have not heard of any unhappy 4-into-1 owners other than issues with moving oil coolers and modifying cowlings.

    Best of luck,

    Wes
     
  4. Mar 8, 2017 #4

    tl_z_bub

    tl_z_bub

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    Hi Scott. I removed my "plans" exhaust and fitted a Sky Dynamics crossover (My S1 was the same spec / engine as yours). This made a noticeable improvement, particularly in the mid range torque when climbing / accelerating. I posted some numbers on here at the time, but imagine flying with 5 gallons less fuel as a rough equivalent.

    I never tried a 4 into 1 on my aeroplane, but for what it's worth my thoughts are that 4 : 1's work best with C/S props - making more power at max RPM but less effective than the crossover in mid range.
     
  5. Mar 10, 2017 #5

    tscottmiller

    tscottmiller

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    Makes perfect sense! Did the crossover pipe create a cowl clearance or oil cooler placement issue?

    Much appreciated!

    Scott
     
  6. Mar 10, 2017 #6

    PittsDriver68

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    The crossover system is OK with the oil cooler but another bump in the cowl might be needed. I had to add a cowl bump on my S-2A, a surprise since the system was a factory option.

    Best of luck,

    Wes
     
  7. Mar 10, 2017 #7

    garyg

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    My understanding is that because the 4 cylinders fire from one side (both in sequence) and then from the other side in sequence), the exhaust cycles are too close together for the same plumbing. The crossover basically installs a gap in the firings, which is where the gains come in. 4 into 1 does the same thing by use of the collector. I would guess the difference between 4 into 1 and crossover is not significant. But stock into either is huge. This made sense to me when it was explained anyway.

    I was looking into 3 into 1 or 6 into 1 for a 540 and I am told that since they fire alternate banks, they do not get the significant gains that the 4 cylinders achieve.
     
  8. Mar 10, 2017 #8

    akt227

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  9. Mar 10, 2017 #9

    EAABipe40FF

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  10. Mar 10, 2017 #10

    cwilliamrose

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  11. Mar 10, 2017 #11

    akt227

    akt227

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    I was able to access that link with Chrome, was blocked on Tor
     
  12. Mar 15, 2017 #12

    tl_z_bub

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    Hi Scott

    My S1-S is "Plans" other than having S1-T style cowl doors. The SD crossover went straight on (Vertical sump) but it was very close to the side rails of the lower cowl where the cam lock fasteners are. Still, "very close" is not the same as "would not fit" so no mods needed (other than to make a wire form to support the exhaust stacks at the very bottom in front of the gear bungee box.)

    Regards,

    Richard
     
  13. Mar 15, 2017 #13

    Skippy

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    Build a custom one to your aircraft and engine and you can design around any clearance issues.
     
  14. Mar 16, 2017 #14

    tscottmiller

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    Hey gang!

    I called Custom Aircraft, California and they quoted a tailored to fit crossover for our Pitts. I believe the only issues I see is applying high temp hose sleeve over two oil cooler lines, shortening the starter cable and a sleeve over the pan line.

    We have been discussing a future change to Wolf gear and headers but we just changed bungees so we might go ahead with the crossover exhaust.

    I appreciate the information!!!!

    Scott
     
  15. Mar 16, 2017 #15

    G-KEST

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    When I ordered my cross-over exhaust from Sky Dynamics for my Pitts S-1S project, they very kindly altered their jig to move the down-pipes inwards away from the bottom cowl 'sill' and there are no clearance problems with the stock cowling at all.

    All the best
     
  16. Mar 16, 2017 #16

    Skippy

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    Scott
    I recently build a 4 into 1 using a company in Fort Lauderdale, did the whole pvc mockup and shipped to them. Pretty easy process and I was able to custom design to my plane and how I wanted it to look. Brett wrote a good article about it that I'm sure he'll share with you.
     
  17. Mar 17, 2017 #17

    tscottmiller

    tscottmiller

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    Skippy..... I think I read an article or post about a mocked up system being used for a final custom exhaust. Great idea! From what I have researched the crossover is best for 2700 rpm's or less. The 4-1 is supposed to gain HP over the
    2700 mark.....

    I would like the 4-1 but the bungees will need consideration thou....
    However, your insight is much appreciated.

    Scott
     
  18. Mar 17, 2017 #18

    jrs14855

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    On my 0 360 S1 when I installed the crossover I was able to go from a 56 pitch Sensenich metal to a 58 pitch. This maintained the same lower speed performance as before but substantially increased the cruise and high speed performance. Very easy to get and maintain 190 plus across the box. The full throttle high speed r/m dropped substantially. My final prop was a Anderson modified Sensenich metal with 60 pitch. This was better still. Easily obtained 200 ias and maintained this across the box.
    The crossovers I used came from a guy named Cochran in the Denver area. Way before Vetterman and others. Bolt in installation with no clearance issues. Ball joint tailpipes did require supports.
     
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  19. Apr 16, 2018 #19

    tscottmiller

    tscottmiller

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    Hey folks,

    I know it’s been awhile since any post but I wanted to report back. We installed the cross over exhaust with insulated silicone hose for the oil cooler lines, oil lines near exhaust, metal heat shields near intake and rubber isolated exhaust hangers. Installing the exhaust didn’t take any time but the OCD anal stuff took some time thou.....The crossover was custome bent and fit the cowl like a glove with no bumps needed. We had one clearance issue and the supplier made a new pipe which worked great!

    Their are two differences we noticed immediately:

    1.) The plane accelerated during takeoff and climbed at 200-220 rpms higher than stock exhaust. The rpm maintained during climb to high akro alt. The engine is more responsive in mid-range and power balance seems better.

    2.) The plane sounds much more “throaty” in the air. I would compare the sound more to big block vs. small block. The sound quality is significantly better from an old gear head prospective. The 4-1 should be slightly better with a tuned collector.

    In short, the cross over is worth the money and installation. I would bet the 4-1 is equally beneficial, if not more.....

    Scott
     
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