Stock Exhaust Manifold vs Shorty Headers +++ WHICH TUNER?

Discussion in 'Mustang Chit Chat' started by Jhol, May 28, 2020.

  1. Jhol

    Jhol Junior Member

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    I wonder what the difference in gains are on the 2018 intake compared to the 2012 intake manifold. I see the intakes aren't horribly expensive. I wonder if the 2012 CAI and throttle body would bolt up okay?

    Also, how expensive do you all think it would be to have the mid pipes cut and retrofitted to long tube headers? Sounds like a serious headache.
     
  2. Juice

    Juice forum member

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    The first cork in the flow of the 11-14 cars is the gt intake at high rpms. The gain from the 18 intake is about an additional 500 rpms of usable power. From what I read, its practically a direct bolt on.
    As for the headers, the long tubes scavenge better. But my past experience with aftermarket headers have been less than desirable. Fittment/clearance issues, blown gaskets due to bolts backing out, difficulty of tightening said bolts due to the tubes in the way, etc. I finally put lockwashers on the header bolts and solved the issue of them backing out. Sorry, Im too cheap to buy those special fasteners sold to solve that issue.
    I have a welder, I can pretty much make my own exhaust. My dilemma is, my car works just fine as-is.
     
  3. teeje

    teeje Member

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    IMO if you are going to go through the hassle of changing headers go with longtubes and get the mid pipe to go with it. Pointless to go to shorties unless you are going to go with a turbo I suppose.


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    Anti and 06 T-RED S/C GT like this.
  4. Dino Dino Bambino

    Dino Dino Bambino I have a red car

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    Not marketing hype. It's been verified by an independent dyno test. The gains are small but real nevertheless.

    https://www.andersonfordmotorsport.com/content/exhshoot3.htm
     
  5. 06 T-RED S/C GT

    06 T-RED S/C GT forum member

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    According to AFM dyno results: JBA shorty headers came in at 325.3 ft lbs Max TQ and 303.8 Max HP. Avg TQ was 303.1 ft lbs. Avg HP was 247.3 Stock manifolds were 323.7 ft lbs max TQ and 298.9 max HP. Avg TQ was 299.3 ft lbs and Avg HP was 244.3

    HP comparison, JBA's gained a maximum 4.9 hp over the stock manifolds and also gained an average of 3 hp. Torque comparison, JBA's gained a max 1.6 ft lbs over the stock manifolds and also gained an average of 3.8 ft lbs.

    At any rate, the independent test results have also verified just how efficient the stock exhaust manifolds truly are. Despite the verified gains of the JBA's over the stock manifolds, the gains are nevertheless so marginal that it's not even worth going thru the hassle of making the switch, let alone justify the cost for just a small 5HP maximum gain along with an average 3.8 lb ft TQ gain/max 1.6 lb ft TQ gain. Just as previously mentioned, there's nothing worthwhile to be gained by upgrading to shorty headers from the stock 3v exhaust manifolds. That being said, if I'm going to go thru the hassle of upgrading from the stock 3v headers? I'll go with longtubes over shorties any day, hands down lol.
     
    Last edited: May 31, 2020
  6. Midlife Crises

    Midlife Crises Member

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    I thought the decision to use mid length or long tubes was supposed to be based on valve timing. Tube diameter is determined by cubic inches of engine. Shorties have nothing to offer. I have seen formulas for calculating tube length that makes use of first or second exhaust pulse to get best scavaging.
     
  7. Dino Dino Bambino

    Dino Dino Bambino I have a red car

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    The header tube diameter is one factor that determines the rpm where the engine will develop peak torque, along with the cam and intake manifold design.
    The header tube length determines whether reflective wave scavenging takes place. The tube length of shorty and mid-length headers is too short to provide any wave scavenging, and any performance gain comes from improved flow alone. Long tube headers provide reflective wave scavenging as well as improved flow, which is why you see significant increases in mid-range torque as well as higher rpm power. The longer the header tubes, the further down the rpm range you'll see torque gains. Unfortunately the header tube length is limited in most vehicles by the lack of available space so a compromise has to be made. Another reason for compromise is the need to place the cats as close to the engine as possible for emissions purposes.
     
  8. Flusher

    Flusher Member

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    My apologies to any party affected by the perception of this being a thread jack.

    Has anyone considered ported and/or Extrude Hone of the factory manifolds? I understand that the modern factory manifolds are lightyears better than the old smog-dog manifolds described in the video below, but would it be a worthwhile alternative to shorty headers? I know, no comparison to legit long-tube headers. Just asking.





    Thanks
     
  9. Midlife Crises

    Midlife Crises Member

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    I am sorry Dino but your information is not accurate. The tube length does not determine whether or not the reversion wave takes place. It determines when it takes place. The tube diameter is selected to keep the exhaust pulse moving at the right speed with as little back pressure as possible. Shorter tubed headers using the first wave can offer extreme scavenging and cylinder fill over a very narrow RPM range. The longer tubed headers are using the second wave for scavenging. This wave is not as strong as the first, it is cooler and is useful over a broader rpm range.
     
  10. Dino Dino Bambino

    Dino Dino Bambino I have a red car

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    Thanks for correcting me on that detail. :)
     
  11. Midlife Crises

    Midlife Crises Member

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    You and I are probably not going to build headers for our car anyway but having an idea of what primary tube length will best match the rpm range intended would help decide between different brands based on their tube length. Throw in the fact that tuned scavenging only takes place over about a 2000 rpm span at best and that set of headers that provide max torque @ 3500 rpm and max HP @ 7000 rpm are mythical. There has to be a compromise on one end or the other.:cheers:
     
  12. Juice

    Juice forum member

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    I have actually read somewhere that the actual length of primary tubes needed just cannot be done in a car. Basically, even long tubes are not long enough for best perfarmance.
     
  13. Dino Dino Bambino

    Dino Dino Bambino I have a red car

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    That's true. You need a primary tubes of ~35"-45" to get the length required for best performance in most street engines, and there just isn't enough space in most production vehicles to accommodate them.
     
  14. Midlife Crises

    Midlife Crises Member

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    There is the compromise. In a street vehicle there is not enough performance gain for manufactures to bother with 35” primaries. They want an engine to perform over a 4 or 5000 rpm range and they still have to make the CATs work. That’s a big contrast from a Drag engine with 28” tubes that only operates from torque peak to HP peak.
     
  15. GlassTop09

    GlassTop09 Member

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    This would interest me as well...…. Would be good info to know if ported 4.6L OEM exhaust manifolds using this process did provide any feasible performance gains...….....
     
  16. Midlife Crises

    Midlife Crises Member

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    Didn’t pumping abrasive material through intake and exhaust manifolds get debunked back in the 1950s. Polishes OK but cuts the wrong areas.
     
  17. Dino Dino Bambino

    Dino Dino Bambino I have a red car

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    I'd say any performance gain from extrude honing the stock cast iron exhaust manifolds would be minimal at best. Even the JBA, which is the best of the shorties, could only muster a 5hp peak gain but it did produce a decent 5-7lbft gain from 2700-3500rpm.
     
  18. tjm73

    tjm73 of Omicron Persei 8 S197 Team Member

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    Sorry to tell you that on the basis of pure law that technically anything other than factory manifolds is illegal, even in Florida. Exhaust manifolds are directly related to the the emissions control function of the engine and it's a violation of Federal law to remove/modify them. Same goes for the mid-pipe. Once you are past the catalytic convertor, things get more free to being changed.

    That fact said, many people change them and nobody is the wiser as the Federal government has no enforcement capabilities and each State may or may not check them at their discretion. Many States say don't change them, but also don't check them. NY, for example, says don't change that stuff, but once a car is 25 years old all they inspect or is safety. They no longer check for emissions compliance.But for those first 25 years, if it isn't there and functioning you fail the inspection and can't drive till it's corrected.

    I'd bet Florida says don't change it, but they don't inspect (last I knew) and have no method of checking nor desire to check at this point.

    Not too long ago the Feds cracked down HARD on a bunch of companies and "off-road" mid pipes are drying up quickly.Not sure why this didn't get more press. Maybe COVID-19 bumped it off everyone radar.

    https://www.hemmings.com/stories/2020/01/14/epa-launches-crackdown-on-emissions-defeat-device-makers

    The long term ramifications are still to be seen, but expect non-compliant stuff to start drying up. The EPA has decided to hold the manufacturers responsible for supplying product that end users put on their cars to defeat the emissions control functions.

    From the article....

    "EPA will vigorously pursue and prosecute companies who attempt to circumvent emission controls that are required to reduce air pollution," Susan Bodine, the EPA's assistant administrator for enforcement and compliance assurance, said in a statement. "This case illustrates why stopping the manufacture, sale, and installation of aftermarket defeat devices is an EPA National Compliance Initiative."

    and

    "According to the EPA, its National Compliance Initiative, which "will focus on stopping the manufacture, sale, and installation of defeat devices on vehicles and engines used on public roads as well as on nonroad vehicles and engines," is slated to run from 2020 through 2023, though the August and September enforcement actions listed above were considered part of the initiative."

    It's clear that the during the next phases the EPA will almost certainly go after the sellers and installers of these products. After that, they will be down to the owners. Us. Enforcement and change are coming. And it started before I was born.

    https://www.epa.gov/transportation-...line-major-accomplishments-transportation-air
     
    Last edited: Jun 2, 2020
  19. Juice

    Juice forum member

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    The short answer is, no computer modification, no check engine light. So shorties are overlooked by inspection.

    Once they start checking for tunes installed, we are screwed. Funny thing is, it is actually legal to make some modification to the tune under some circumstance. SCT is the only company right now that is emission legal, as long as the end user keeps the OBD/emission stuff unaltered.
     
  20. tjm73

    tjm73 of Omicron Persei 8 S197 Team Member

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    The day of cheap and easy "dirty" increases of power is winding down. The sun is setting on that. While not as cheap, the good news is we can make bucket loads of power and still be clean these days.
     
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