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Discussion Starter #1
On my 1st long trip in my 2019 Santa fe (Ohio to Fla) I had real issues with the cruise control not maintaining the set speed. It worked good in flat country, but when I got into KY and TN it would drop off 3-5 mph every time I went up a hill. I have never had a car that dropped off that much. Has anyone else had this issue? I travel a lot and this will be a game changer for me.
 

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2019 Ultimate 2.0t AWD
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When it would drop off going uphill, do you mean the cruise control would disconnect? Or Does it downshift once it goes below 5mph and catch up to the set speed?
 

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I see the same results. Will run for miles with 3-5 MPG below set speed. That coupled with the speedo off slightly (almost 2mph at 80) I set my cruise for 80 or 81 to run about 75-78 on the interstate. (posted speed is 75) I try to stay close to posted speed but see the same results.
I've checked speed against: Garmin GPS, Dash Cam with GPS, phone with GPS and radar signs along road so the speed is off compared to all of these, and the GPS systems all seem to match so the vehicle seems to the be odd speed. I also find most traffic passes me if I run the speedo at the posted speed, which also indicates I'm going slower than the speedo indicates. I will ask them to check at next service but I'm doubtful anything will change. I suspect I'll have to adjust my driving style.
 

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When it would drop off going uphill, do you mean the cruise control would disconnect? Or Does it downshift once it goes below 5mph and catch up to the set speed?
In my case, no shift of gear and will drive for miles at the slower speed, yet cruise remains engaged and functional....
 

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You need to learn to put your foot into it on hills.
 

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Cruise controls can't overcome vehicle dynamics. If it can't control the set speed on the flat then take it back to the dealer.
 

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Discussion Starter #7
When it would drop off going uphill, do you mean the cruise control would disconnect? Or Does it downshift once it goes below 5mph and catch up to the set speed?
Drops off 3-5 mph before downshifting. Usually starts slowing down as I start going up the hill, then near the top it would downshift and catch up. That's on a long hill, on smaller hills it would just slow down 3-4 mph and then catch up after I got over the hill.
 

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I think this is a design feature in the grade logic. There is a speed range where by it is acceptable within the range, the control system will take action if outside the range. The engineering term for this is hysteresis. This prevents tranny constantly downshift & upshift then repeat again.
 

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Need a more powerful engine. On our old '08 with the 2.4 it was annoying that when on a hill the speed would start slowing then the downshift would come into play to try and catch up.
Any of our other cars will what be termed more powerful, speed stays the same.
See the '19 weighs in at 3600 to 4400 lbs along with HP 185 to 235, so depending on the combo one will be worse than the other.
Our '11 EX-T weighs 3300 lbs with a 274 hp, similar as our Acura with 285 hp with a 3600 curb weight, no problem with maintaining speed. Now our other car with 305hp and a weight of 2800lbs it's barely working when going up a hill/mountain.
 

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What drive mode are you using? Perhaps “Sport” would help as it uses more aggressive shift points.
 

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Discussion Starter #14
Need a more powerful engine. On our old '08 with the 2.4 it was annoying that when on a hill the speed would start slowing then the downshift would come into play to try and catch up.
Any of our other cars will what be termed more powerful, speed stays the same.
See the '19 weighs in at 3600 to 4400 lbs along with HP 185 to 235, so depending on the combo one will be worse than the other.
Our '11 EX-T weighs 3300 lbs with a 274 hp, similar as our Acura with 285 hp with a 3600 curb weight, no problem with maintaining speed. Now our other car with 305hp and a weight of 2800lbs it's barely working when going up a hill/mo
I also have a 15 Outback with less hp and it will downshift at 1-2 mph slowdown. With a 8 speed tranny, you would think the Santa fe it would downshift right away.
 

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Discussion Starter #15
I think this is a design feature in the grade logic. There is a speed range where by it is acceptable within the range, the control system will take action if outside the range. The engineering term for this is hysteresis. This prevents tranny constantly downshift & upshift then repeat again.
That's worth checking, thanks
 

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Need a more powerful engine.........
Rubbish, it's an algorithm. It escapes me at the moment but one auto maker was experimenting with cutting back to a single cylinder at cruising speeds - they decided on two as the single vibrated a bit too much. Newton's 1st law tells us not as much is required to keep it in motion. Unless you're pulling a max load up the "Ike Gauntlet" 185 or 236 is far more than you require up a grade. Hyundai has written the algorithm so that the speed varies slightly - this is to strike a balance between comfort & efficiency (much like your house allows a variance in temp for comfort & function). You really think they can't make it stay at exactly the set speed all the time? That they have the technology that allows the car to drive itself but can't maintain a precise mph? Hardly......they do it because you probably wouldn't like the ride w/ content throttle inputs & brake applications. Think about it - wind gusts, grades, drafts from traffic.........it would not be a fun ride.

Now, I'm not saying Hyundai's allowance for speed variations isn't a bit too lax - just that HP has nothing to do with it.
 

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Rubbish, it's an algorithm. It escapes me at the moment but one auto maker was experimenting with cutting back to a single cylinder at cruising speeds - they decided on two as the single vibrated a bit too much. Newton's 1st law tells us not as much is required to keep it in motion. Unless you're pulling a max load up the "Ike Gauntlet" 185 or 236 is far more than you require up a grade. Hyundai has written the algorithm so that the speed varies slightly - this is to strike a balance between comfort & efficiency (much like your house allows a variance in temp for comfort & function). You really think they can't make it stay at exactly the set speed all the time? That they have the technology that allows the car to drive itself but can't maintain a precise mph? Hardly......they do it because you probably wouldn't like the ride w/ content throttle inputs & brake applications. Think about it - wind gusts, grades, drafts from traffic.........it would not be a fun ride.

Now, nothing to do with Hyundai's allowance for speed variations isn't a bit too lax - just that HP has nothing to do with it.
We're not talking about crusing speed on a level road, we're talking about an incline, and man, you're way off base if you believe HP has nothing to do with the car slowing on hills. With the low powered engines, no, they can't keep the same speed. Experiment with the cruise control off and try to maintain the speed, you can't, as the pedal is depressed down farther, it will be at a point where it must go into a lower gear. The old '08 with the 2.4 and with 4 adults, it would hit a hill, the trans downshifts and with the pedal to the floor it wouldn't maintain the same speed, simply because it couldn't.

Another item to keep in mind is the gear ratios. With the increase in transmission gears to obtain maximum fuel mileage along with the final drive ratio it would be impossible under a high load to maintain the given speed:
2019 Santa Fe 8th gear ratio .64 combined with a 4.08 final drive becomes an overall ratio 2.64 and it just can't stay in 8th and slow.

Taking it to an extreme, how about you find an old VW Super Beetle, no programing to contend with, take it for a ride, go up a steep hill with the 60 HP monster engine and see if you can maintain the same mph if HP has nothing to do with the slowdown.
0-60 on that car 23.7 seconds and I'll guarantee you that it will slow down, and that has a 4 cyl engine.
 

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I've driven a V8 Cadillac up a hill and if the hill is steep and long enough, it will start to slow in momentum, and eventually downshift to catch up to the set cruise control speed. I've also driven a 4 cylinder engine up the same hill. It does struggle more obviously, but if you have enough momentum, i.e. 75+ mph before the base of the hill it should carry the car up a decent length before it downshifts.
 

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There's limits to what the car is capable of. I have a V8 and when towing I get the same full throttle and downshift up a steep hill and the car still drops speed till the cruise control drops out and you then have to do the work. In my situation more power would certainly help.
 

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We're not talking about crusing speed on a level road..........Taking it to an extreme, how about you find an old VW Super Beetle, no programing to contend with, take it for a ride, go up a steep hill with the 60 HP monster engine...........
? Okay, a 60hp VW is close to a 236hp vehicle. It's the algorithm, period, it's quite capable of running a highway grade (6%).

Another item to keep in mind is the gear ratios. With the increase in transmission gears to obtain maximum fuel mileage along with the final drive ratio it would be impossible under a high load to maintain the given speed:
2019 Santa Fe 8th gear ratio .64 combined with a 4.08 final drive becomes an overall ratio 2.64 and it just can't stay in 8th and slow.
Um, ah, so it downshifts to maintain speed......?
 
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