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Discussion Starter #1
Has anyone maxed their car out yet? I went for it on a runway, hit 145, and ran out of runway. I think this car has 155-160 in it. I did my run with no wind, premium gas; air temp was 60 F, elevation 4200 ft. At sea level I’m sure this car would be faster.

Thoughts?
 

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there's no way it goes 145 without a tune because of the speed limiter. What kind of tune do you have? and as Don asked what kind of tires? Because I know that you wouldn't go 1 45 with under rated tires, right?
 

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Discussion Starter #5
They are v rated tires, came with the car. Again, it is a 2014, they do not have a speed limiter that I am aware of. And I can assure you it went 145, my speedo, and a friend's radar gun verified. A little more info, I had traction control off, and was shifting manually (stupid little rocker switch) at that speed I was at 5400 rpm in 5th.
 

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It was pretty stable for such a big car, brake performance was better than expected, although the nose really dove down which would suggest the front diffuser was allowing too much air under the car, causing it to lift. I wouldn't be comfortable going much faster. I found this instrumented test that says it is drag limited at 149.

2014 Chevrolet Impala 3.6L V-6 Instrumented Test – Reviews – Car and Driver
 

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I find it really hard to believe that 145mph occurs when you claim. 5400rpm, 1.0:1 gear ratio, 2.77 final drive and 27.7" diameter tires equates to 160mph....so unless there was MASSIVE slip in the torque converter (which would've set a DTC) I just don't see 5400 being 145. Or realistically 145mph at 4200ft.

I also not sure what you expected the brakes to be like but I already know from my romps to the ton that there's no way I'd attempt 145 in a stock Impala. Nor would I consider the brakes good past that mark. They are far too soft and don't communicate well enough in my opinion.they do stop well from any thing under 75mph though.
The brake dive is most likely due to the softly sprung nature of the car and not its "front diffuser allowing too much air under the car".... First and foremost because if we are calling the undercar trim panels a " diffuser" then the fact that they let "too much" air under the car would actually reduce lift.
 

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Discussion Starter #9
Going to answer each point here:

I find it really hard to believe that 145mph occurs when you claim. 5400rpm, 1.0:1 gear ratio, 2.77 final drive and 27.7" diameter tires equates to 160mph....so unless there was MASSIVE slip in the torque converter (which would've set a DTC) I just don't see 5400 being 145.

(Yeah, I might have been off about that, your math is good, my memory must be slipping!)

Or realistically 145mph at 4200ft.

(Believe what you want, I have a character witness to verify, I can provide sources to this claim, but you will have to PM me. I have no reason to lie.)

I also not sure what you expected the brakes to be like but I already know from my romps to the ton that there's no way I'd attempt 145 in a stock Impala.

(I wasn't expecting a whole lot, someone asked how it handled, I was giving them my opinion!)

Nor would I consider the brakes good past that mark. They are far too soft and don't communicate well enough in my opinion.they do stop well from any thing under 75mph though.

(I agree they are soft and not very communicative, but are adequate for a large sedan.)

The brake dive is most likely due to the softly sprung nature of the car and not its "front diffuser allowing too much air under the car".... First and foremost because if we are calling the undercar trim panels a " diffuser" then the fact that they let "too much" air under the car would actually reduce lift.

(You might have a point here about the softness of the suspension, although the bottom of the bumper, you will notice a protruding edge, this is to increase the air velocity. Again, I was trying to avoid a long discussion about Bernoulli's Principle, and a lecture in physics, and probably used some out of place terminology, I was attempting to make my reply more readable, and allow those without a Degree in Mechanical Engineering to comprehend what I have written, my bad. More air in a confined space would equal a higher velocity, which would create low pressure area underneath.)

In summation, thanks everyone for the warm welcome, my question still stands, and if you want additional info on a subject, I will be happy to use the proper terminology to avoid confusion in the future! :eek:k3:
 

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i can verifiy 115 is not a limit. i have a pic of about 126. regrettably i do not have a pic on a trip in when i was over 130. sigh. but my gf would probably verifiy :devil:
 

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Going to answer each point here:


(Yeah, I might have been off about that, your math is good, my memory must be slipping!

Or realistically 145mph at 4200ft.

(Believe what you want, I have a character witness to verify, I can provide sources to this claim, but you will have to PM me. I have no reason to lie.)
Im not suggesting your lying,nor do I need character witnesess, just pointing out that your numbers dont make sense to me, even with a 1% error for the radar gun, and a 2 or 3% deviation on tire size, display on the tachoemter, etc...its still off. Id expect to see rpm right at 5,000rpm for a true 145mph. Even working back from Goodyears specs of 755rev/mile comes out to ~5050rpm @ 145mph. Could I be wrong in some of my calcualtions? Sure, you admit (sarcastically?) that your memory may be off, but Id just like to try for the benefit of all to figure out the numbers involved.


(You might have a point here about the softness of the suspension, although the bottom of the bumper, you will notice a protruding edge, this is to increase the air velocity. Again, I was trying to avoid a long discussion about Bernoulli's Principle, and a lecture in physics, and probably used some out of place terminology, I was attempting to make my reply more readable, and allow those without a Degree in Mechanical Engineering to comprehend what I have written, my bad. More air in a confined space would equal a higher velocity, which would create low pressure area underneath.)
I wasnt correcting your choice of words on vehicle parts...I dont care if you call the edge of the bumper and undercar trim a diffuser, or if you call airdams a spoiler, or if you call spoilers wings....What I was pointing out is that you are incorrectly implementing the function of the different air velocities over and under the car. If the air moving under the car is going faster than the air over the car you will indeed have a low pressure area under the car....this will allow the higher pressure above the car to push the car down, reducing lift and lowering the car. This is the function of diffusers and most spoilers.

The Impala likely DOESNT have a larger quantity of air flowing underneath it than it does over it. It may be turbulent and slower underneath than compared to over top, and this would create lift.

Lastly, and I guess this sentence was excised from my response from my phone previously through some mistake of mine, but I would imagine that 145mph is probably max velocity for the impala @ 4200ft. While the reduced air density at your altitude is conducive to going fast on the ground(see Bonneville, also at 4200ft) this same reduction in drag also corresponds to as much as 15% decrease in horsepower as compared to sea level. Id say 145mph is a record :)



In summation, thanks everyone for the warm welcome, my question still stands, and if you want additional info on a subject, I will be happy to use the proper terminology to avoid confusion in the future! :eek:k3:
Sorry I wasnt part of the warm and fuzzy welcome commitee, its just not who I am.:lol:
Welcome to the Impala forum :eek:k3:
 

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IIRC, the 2012/2013 got pretty far up there as well. I think it has to do with the LFX more than anything else. What tires are on it? Brand/model that is.
 

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Yeah that Car and Driver indicates 149 drag limited, you are right. Thanks for the follow up.
 

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Discussion Starter #15
I'm going to try again, this time at +- 3000 ft, downhill, with a cameraman. I think i will stick with my V rated tires, as I will only be momentarily at or above 149. Should have some evidence in the next couple of weeks.
 

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Going downhill doesn't tell us much!! If you try again, would be interesting to see it on a flat road again.

Just make sure you don't kill yourself (or someone else) just to see how fast you can get it to go!

Sent from AutoGuide.com Free App
 

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I will also go on record at 126 mph. Still had pedal. Followed a left laner doing 5 under the limit for over 10 miles backing up traffic on I-70. When I got a hole I went around him with the pedal to the floor. Had to let off due to upcoming traffic. Was very impressed. Can't get over how quiet the cabin is. I think it's quieter than my previous Cadillac DTS but will admit the ride is a bit stiffer.
OP, I really dig your blacked out grill. Please share how you did it if you don't mind.
 

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Can't get over how quiet the cabin is. I think it's quieter than my previous Cadillac DTS but will admit the ride is a bit stiffer.
Triple sealed doors. :eek:k3:

Although, I suspect areas with more salt and crap, might have more door rust outs in the future.
 

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