2015 mustang gt feels hesitant - Mustang Evolution

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Old 03-24-2015, 10:52 PM   #1
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2015 mustang gt feels hesitant

New to forum, I have a new 2015 mustang gt and have notice when I first take off in it, before the engine warms up, if I get into the throttle slightly, around 3000 rpms it feels jumpy or hesitant. Once I get about a mile down the road or so it runs fine. Just wondering if this is normal or something I should get checked out. Thanks
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Old 03-25-2015, 05:16 AM   #2
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Mine does the same. Seems to be in the tuning. Not sure yet if it's cam timing related or the CMCP's in the intake. But yes, there is a noticeable power change around 2800 RPM's.
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Old 03-25-2015, 07:10 AM   #3
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I'm gonna put the car back on the dyno today. I'll start the sweeps down at 2000 RPM's instead of 3000 where I was doing them before and see if I can catch the change in the data logs. It might not be as noticeable with the car warmed up but I'll see if it shows up.

This was something I addressed when I sent in the questionaire for the tune but it's still there, so we'll see.
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Old 03-25-2015, 07:15 AM   #4
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I noticed the same thing with mine.


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Old 03-25-2015, 07:35 AM   #5
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I know my little 2.0 '14 Focus did the exact same thing. 2800 RPM's there was a noticeable power change.
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Old 03-25-2015, 10:35 AM   #6
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I'm gonna put the car back on the dyno today. I'll start the sweeps down at 2000 RPM's instead of 3000 where I was doing them before and see if I can catch the change in the data logs. It might not be as noticeable with the car warmed up but I'll see if it shows up.

This was something I addressed when I sent in the questionaire for the tune but it's still there, so we'll see.
Ok sounds like it may just be how it is. Mine is fine once it warms up just does it when I first get in the car. As long as I shift at 2500 or below I never feel anything. Just when I let it get to like 2800 I can definitely feel something. Then about a mile or 2 down the road I don't feel anything
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Old 03-25-2015, 10:56 AM   #7
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Originally Posted by silverstangg View Post
New to forum, I have a new 2015 mustang gt and have notice when I first take off in it, before the engine warms up, if I get into the throttle slightly, around 3000 rpms it feels jumpy or hesitant. Once I get about a mile down the road or so it runs fine. Just wondering if this is normal or something I should get checked out. Thanks
hey Silver - Welcome. That's a good question and I swear this isn't only on the Mustang but across the board on their cars. Just like silverS550 had said below this is something that he saw his focus and considering I just purchased a 2014 EcoBoost F150 that was a leftover it does the exact same thing! Just my .02 but I think it's just coming in and out of cycle and once it's up to temperature it typically subsides. Have you experienced this anywhere else or just on cold start?

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Old 03-25-2015, 11:01 AM   #8
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hey Silver - Welcome. That's a good question and I swear this isn't only on the Mustang but across the board on their cars. Just like silverS550 had said below this is something that he saw his focus and considering I just purchased a 2014 EcoBoost F150 that was a leftover it does the exact same thing! Just my .02 but I think it's just coming in and out of cycle and once it's up to temperature it typically subsides. Have you experienced this anywhere else or just on cold start?

Alex
No its only when I first start down the road. It runs great after that. I thought it was probably just how it was but I was wanting to see if anyone else was having the same issue.
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Old 03-25-2015, 11:57 AM   #9
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i experience the exact same thing on my car. started letting it warm up a bit before driving out of precaution, although I'm not sure if necessary...
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Old 03-25-2015, 12:06 PM   #10
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i experience the exact same thing on my car. started letting it warm up a bit before driving out of precaution, although I'm not sure if necessary...
Yea I've been doing the same thing. It's just a little frustrating having to let my brand new car warm up so it will perform like it should
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Old 03-25-2015, 12:28 PM   #11
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I will chime in also, I have notice the same issues when it is cold, guess it is just its way of saying I need to warm up a bit more!
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Old 03-26-2015, 06:08 AM   #12
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No its only when I first start down the road. It runs great after that. I thought it was probably just how it was but I was wanting to see if anyone else was having the same issue.
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Old 03-26-2015, 06:49 AM   #13
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One thing to remember is there are a TON of modifiers and limiters in the factory tuning. You have limiters based on coolant temp, trans temp, barometric pressure, torque limiters based on throttle position, limiters based on gear seleted, etc....there are as many limiters as there are tuning parameters.


If you've never ACTUALLY tuned a motor before, here is an example of what you're looking at. This is just the AFR table (in lambda) for the '88 based on RPM. If you look over to the left of the picture, you see a bunch of the tables / parameters / limiters (they go down out of frame) that you have to mess with to make it do what you want. If you miss a SINGLE limiter, you can be chasing your tail trying to figure out why it's not doing what you're telling it.....but this is where data logging comes in. Data logging and knowing HOW to read the data logs is where the real money is made. You can build what you think is the most whoop a$$ tune on the planet, but until you log it and see it's actually doing what you're telling it to do, you're just hoping that it is. This is why I don't go by "seat of the pants" testing. The seat lies when the wallet gets light....the dyno, track and data logs don't have those feelings attached.


If you don't know what lambda is, it's simply your AFR's represented on a scale of 1.0 vs 14.7 : 1. Example....an AFR of 14.7:1 would be 1.0, an AFR of 12.5 would be .85. In the picture below you can see I'm shooting for a target AFR of 11.6 while the car is on boost. This is for 93 octane pump gas, on race gas I'll go leaner up toward 12 - 12.5. If the car was running lean, let's say 17:1, you see something like 1.16.


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Old 03-26-2015, 07:39 AM   #14
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This is what you're actually looking at when you're trying to see what's going on with the car. These are data logs from yesterday on the dyno. This first one is dead stock.



This one is "tuned"....



That's what you're interpreting when you're trying to make the car do what you want.


One way to really see the TRUE impact of a tune on the cars REAL performance is to look at the data log and dyno graph in time vs RPM or speed. You'll know it's picked up USABLE power and torque throughout the curve when you see the total run time DECREASE (i.e. from the time from RPM A to RPM B). If you go from a 10 second sweep to a 9 second sweep, what that really means is the car now goes through the RPM range 1 second faster (i.e. made more power and is turning the roller quicker).

Peak power is great, but what's really important to drivability is power UNDER peak, especially the torque.
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