[Eric91Z]

Ok, will try to be clear on this so you all know where I am coming from. Got a few questions around tunes, tuning, drivability related items and looking for input/feedback from those that have tunes, have done some tuning, etc.

Anyway, background on the car: 2014 Impala LTZ Limited. I purchased it with about 8900 miles on it and now have right about 30,000 miles on it. Can has no engine/performance work other than the current tune. Here are the items I am looking for input on:

1. First gas mileage: prior to installing the tune, my DIC gas mileage was pretty close to gas mileage figured by hand at fill up. Usually within 1 mpg or so. Ever since installing the tune, the DIC is consistently showing about 3 mpg better gas mileage than figuring by hand at fill up. The hand figured number is almost identical to what it was prior to tune (on DIC and by hand). Just the DIC now is showing about 3 mpg higher. Tuner has no clue as to why and notes they don't mess with those conversions in the ECM. Thoughts?

2. Tranny/engine response: since the tune (and I have cleared TCM and done full load of tune), but at times when driving around town, like coming to a stop light or corner, where you slow down, almost stop, don't stop all the way, and then go to accelerate again, the car has noticeable delay/lag. Up to a second or so at times which can be a little disconcerting if traffic is coming! Used to have a Ford 500 that was like that and was resolved with an ECM update from Ford back them. When I clear the TCM and do the full reload of tune, it seems better again, but then comes back.

3. Tranny engagement: this has only happened once and was today, but was not what I want the car doing. Was accelerating, light throttle, up to highway speed. Got up to about 55 mph and backed off to maintain speed. Was kind of waiting for the feel to go in to 6th gear, but never felt it, and car started slowing down a bit. So, give it a loot gas and revs up, but doesn't speed up then tranny kind of slams in gear and goes. Kind of like it was slipping or in neutral then in gear all the sudden. Had never done that before and didn't again afterwards.

Car has not been beat on, never any transmission related type things prior to tune, and has always run well. Not trying to slam on this tune by any means, but I don't want to have to clear TCM and reload tune every time it acts up or something new comes along.

So, go. What do you guys think? Need any additional information from me to help clarify or discuss? Let me know what you think.

On a side note, going to drive a '15 Chevy SS tomorrow. In a dream world, the above issues would be no big deal as the SS would come home with me! Actually, I would probably build the '16 SS I want if I got rid of the Impala!

 

[jtrosky]

What tune do you have? Trifecta, Overkill or some other tune? Obviously, it sounds like a tuning issue since you didn't have those issues before the tune...

Also - any mods to the powertrain?

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[Eric91Z]

Trifecta tune. No other power train mods except K&N filter (yes, I know...). MAF was cleaned couple hundred miles after installing K&N just to be safe (same process I have used to clean MAF in this car before and plenty of others).

Other than that, drivetrain is bone stock.

 

[ImpalaLFX13]

Eric91Z,

I have my Trifecta tune data-logged earlier this summer, and it did help on your #3 issue, but, once in a while, when I give a quick snap on the throttle, then back off and back on, the rpm will raise without engaging in the proper gear. As for the #1, I've been compiling all my fuel in fuelly.com, and I've notice an slight improvement. #2, also better than factory.

You may what to drain your transmission and add a fresh 5 liters of Dextron VI and a bottle of Lucas transmission conditioner, it will help a bit (look under transmission treads for more info)

good luck

 

[Eric91Z]

I have been kicking around a transmission drain and fill with 30,000 on it...


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[evil ken]

I have One issue where when i go full throttle to about 80 mph. Then i lightly brake, when the speed goes down to about 55 or 60. The car bogs down for a sec. Like its a semi rough down shift. IT doesnt do it when i let off the accelerator pedal and let the speed decrease on its on, without me braking. This with a trifecta tune.

 

[jtrosky]

These types of issues are why I eventually decided that I would only truly be 100% happy if I had the ability to tweak the tune myself... I didn't like the fact that I couldn't see or change anything with the Trifecta tune at all... At least with the Overkill tune, you can tweak it (if you have an HPTuner device) - not so with the Trifecta tune - it's 100% locked down....

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[ImpalaLFX13]

evil ken,

that's weird, I had those issues (rarely) on the stock tune, but not anymore, once in a while, the transmission acts strange only when I do a quick pump-and-dump on the gas pedal and slightly press on the gas pedal again.

No issues with the Trifecta in normal driving, light or moderate throttle position. etc.

Just a quick question, do you still have the factory size tires? I'm just wondering if someone installed a smaller size tire to get a more aggressive FD? ex: 225-55-17 to 225-50-17 (on LT models)

 

[Eric91Z]

I have kind of wondered if any of the issues are from going to "Sport On" to "Sport Off". My driving is very mixed. All in town driving is done with Sport On (Cruise turned off). But I do commute daily, every other week, where I am on the highway. During that time Cruise is on, so Sport Off. And that includes driving in that mode through some small towns, stop and go. Then get off highway and back to Sport On (Cruise power button off).

Just wonder if the ECM "learn" features get confused from the switching back and forth...


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[ImpalaLFX13]

I don't think the tune gets confused, I think it's more than a tranny algorithms?

Just so you know, even when you have the tune CC off, the tune is always there. It's just in fuel sipping mode, until about 4K. If you are in a WOT with the CC on, the tune will be full-on power starting around 4K to red line (minus the 9C!/C3 shift points).

But, with the CC off, you do get about +50whp and 65wtq around 2,500rpm.

tried that on the dyno, and you clearly see the power dip from 2,500 and gradually joining the CC off power curve at 4K

 

[Eric91Z]

Doesn't the Trifecta go in to ECO mode in both Sport and non-Sport modes? They said ECO is based on certain throttle, speed, etc parameters in either mode. And yes, I know tune is always on no matter cruise setting, but cruise on is closer to stock than Sport mode (lazy TCM settings, less responsive throttle like stock, etc)


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[jtrosky]

What I've learned dealing with tunes is that a "one size fits all" tune (aka mailorder tune) cannot possibly compare to a tune that you can customize to your specific car and your specific driving style. It's just not possible - there is no way that a "generic" tune can compare to a tune that you customize based on hours and hours and hours of actually driving in *your* car, with *your* driving style. A re-tune after datalogging may help a little, but it's mainly for extracting the most power - not for the best drivability.

Really, the vast majority of folks don't care about extracting the most power from the car at all costs - they are more concerned with "drivability" - most people use these cars as daily drivers and never once race them or take them to the track, so a little added power at high RPMs really isn't even beneficial to them most of the time.

For my needs, for example, I go for drivability, comfort and reduced risk above all else. I'd rather lose a little fuel efficiency and gain better drivability. I'd rather have smooth, un-noticable shifting versus "firm", "jerky" or fast shifting. I'd rather keep timing mostly-stock versus pushing the timing to gain a little more power - in my case, I actually *reduce* timing slightly in certain areas compared to stock to address some common KR areas that I noticed with the stock timing.

Everyone is different and has different goals and different driving styles, which is why, in my opinion, a mailoder tune is never really an optimal solution - it's full or compromises that you can't correct (at least with Trifecta). Overkill, on the other-hand is a great tune to start with - and customize from there for your particular needs. The price of the Overkill tune file is worth it just to learn from, in my opinion (by comparing it to a stock tune to help learn what changes have what effects).

Just some food for thought and another perspective.

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[ImpalaLFX13]

Not sure about "always on", but with the massive wtq gains down bottom, les throttle needs to be applied to have the 3,800+ pounds moving.

But, I strongly recommend you to, when you're done (or almost done) with the bolt-on mods, to have you Trifecta tune data-logged.

I'm not sure if you need to report the headquarters in Texas, or have a local license technician, but try to have it done, it improves the overall drivability.

I'm planning to do it again when I'm done playing with JacFab intake spacers/ Overkill 80mm throttle and the 3.5" intake retrofit kit and after cats down pipes.

Hope to have all it done by June 2016?

 

[Eric91Z]

Yeah, I am done with engine bolt ons as far as I can see. Want more suspension stuff and tune was more for better drivability and little more power.

Not planning on going crazy as this car will most likely end up going to my daughter in a couple years when she starts driving (if I don't trade in on something else before that!).


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[ImpalaLFX13]

EricZ,

same here, planning to keep my current Imp for another 3 year, then I want to move up in a more luxurious car (always a 4 door saloon). I could really see myself in a 2017-18 Lincoln Continental with a 3.0L V6 twin-turbo, pillow seats, plush interior and ride, etc. Even my 16 year old rater me to give here my 2009 Hyundai Accent winter beater hatch than my 2013 Chevy Impala when she gets her license next year. She thinks it for old people! Kids.

But until then, I will test and race parts, JacFab is almost done, next it will be Overkill parts, then I will see what will be available. I'm still thinking power can be achieve by playing with the Thermosat (stock is 180), but maybe Phastek/ Overkill will have a high flow version of it, also, maybe an electric water pump conversion? If a vendor out there and want me to test it, just contact me.

CTS is also in my choice, the 3.6 TT would also look very nice in my garage, but, I will be looking for the best interior, ride and the smoothness of the drive.

 

[Eric91Z]

Well, I just got my winter wheel/tire set from Tire Rack for Impala. So it is set for a while. And pass that on to my daughter. She actually runs the Torque Pro for me when we do impromptu 0-60 runs out of the highway when I am taking her to school...

I am not sure what will be next. Kind of want a truck again. If so will be 1/2 ton Silverado Z71 with 6.2L. Also test driving a SS today. And maybe Charger and Challenger RT. Next car will be 4WD, AWD., or RWD. No more FWD!


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