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Thread: Understanding the 2015 GT engine from the 11-14 V8 Mustang engines.

  1. #1
    Advanced Tuner
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    May 2015
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    Understanding the 2015 GT engine from the 11-14 V8 Mustang engines.

    Hey Guys,

    I am creating this thread to discuss the 11-14 GT engine configuration and tuning, vs the 12-13 Boss engine configuration and tuning, vs the Cobra Jet engine configuration and tuning, vs the 2015 GT engine configuration and tuning.

    I will start this out by saying that they all share the same block. It appears that they all share the same compression, bore and stroke as well, maybe a little different pistons and rods. Head flow varies between vehicles as well. I would assume the valvetrain setup and operation is similar as well. Mainly what I am getting down to is these engines are pretty identical except for different strength components in the bottom end, valve springs and retainers, and cam specifications.

    Now, from what I have seen, the 11-14 GT, 12-13 Boss, and Cobra Jet engines all LOVE valve overlap, except for the 2015 GT engine. Below I have a list of valve train components from engine to engine.

    11-14 GT
    Intake Cam Lift- 12mm, 260* duration.
    Exhaust Cam Lift- 11mm, 263* duration.

    12-13 Boss
    Intake Cam Lift- 12mm, 260* duration.
    Exhaust Cam Lift- 13mm, 263* duration.

    Cobra Jet
    Intake Cam Lift- 13mm, 263* duration.
    Exhaust Cam Lift- 13mm, 290* duration.

    2015 GT
    Intake Cam Lift- 13mm, 263* duration.
    Exhaust Cam Lift- 13mm, 263*duration.

    Now, with these specs in mind, you can really see a comparison here of what they did on the new 2015 GT, taking bits and pieces from each motor to make the new engine. Also, the 2015 comes with .3mm larger intake and .8mm exhaust valves over the standard 11-14 GT and Boss engine. The Boss engine and the CJ engine both come with ported heads from the factory, now the 2015 heads are ported larger than the 11-14 but just not sure by how much. The biggest thing that sets the 2015 GT engine from the Boss engine is the Boss intake manifold and the 2015 GT has 1mm more lift on the intake cam.

    Now with all of that said, I can't think of anything different that would make the 2015 engine that much different from the previous. I know a new ECM was implemented and added 14 more mapped points to the configuration, however, that does not change the tuning and operation of the ECM and engine.

    I feel really strongly that the reason the 2015 GT does not like valve overlap and that it prefers to have the intake valve open ATDC is behind flow restrictions due to the stock components that the vehicle comes with. I feel with the increase in flow mods, we will really start to see this engine behave like the engines it was designed after.

    Does anyone have any other information they could contribute to my list and the dilemma at hand?

    Thank you,

    Kris
    Last edited by kris5597; 09-30-2015 at 07:34 AM.

  2. #2
    Tuner in Training
    Join Date
    Aug 2014
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    A lot of things to change above.

    There are multiple different blocks with incompatibilities such as head bolt diameter and length.
    CJs are not the same compression.
    Multiple different rods.
    Multiple different pistons.
    NA CJs are a larger bore.
    11-14 GT are the same 12mm intake cam as the Boss.
    11-14 GT has an 11MM exhaust cam.
    Only Boss had CNC chambers/ports, 15 does not.
    Boss intake valve is same diameter as 11-14 GT.
    15 GT and Boss exhaust valve is only 0.8MM larger than 11-14 GT.
    15 GT intake valve is only 0.3MM larger than 11-14 GT and Boss.
    Last edited by kdanner; 09-29-2015 at 09:51 PM.

  3. #3
    Advanced Tuner
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    May 2015
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    Quote Originally Posted by kdanner View Post
    A lot of things to change above.

    There are multiple different blocks with incompatibilities such as head bolt diameter and length.
    CJs are not the same compression.
    Multiple different rods.
    Multiple different pistons.
    NA CJs are a larger bore.
    11-14 GT are the same 12mm intake cam as the Boss.
    11-14 GT has an 11MM exhaust cam.
    Only Boss had CNC chambers/ports, 15 does not.
    Boss intake valve is same diameter as 11-14 GT.
    15 GT and Boss exhaust valve is only 0.8MM larger than 11-14 GT.
    15 GT intake valve is only 0.3MM larger than 11-14 GT and Boss.
    The wrong information I had has been corrected, you are right on a few things. The multiple rods and pistons is irrelevant if bore, stroke, and compression are the same on an n/a engine. I understand the CJ motor is on another level with compression and bore size. Just throwing in comparisons. The 2015 does have larger intake and exhaust ports. From what I have read, instead of them being CNC ported like the Boss, the same port sizes where introduced into the casting.

    However, this still doesn't answer my question of why the 2015 engine doesn't like valve overlap.