it will comfortably run on the electric motor on a flat road at 70 mph
Is that because your Ioniq is a PHEV and not a HYBRID maybe ?.
A hybrid can NOT perform this task.
If your car is a PHEV and you have depleted all of the electric range, then the petrol engine WILL run be required to run constantly, until it has regained enough energy to power the electric motor.
If you read my post again, you will see that after owning a PHEV for over four years, I was totally happy with how it performed, both in pure electric mode and in petrol mode.
So, can you hear / feel the engine kicking in and out at a constant motorway speed as you suggest - No of course not, if in hybrid auto mode ( or something similar ) it will "Sip" on any available electrical power it has available first, then it will feather in the power from the ICE.
The power delivery is seamless at that speed of course it will be.
When the car is cursing on a flat surface, it is in "Coast" mode.
Any small amount of power needed is supplied by the electric motor, that how you make your fuel savings.
Given you have any electrical range left in your HV pack to supply that energy that is.
Any larger demand for power ( overtaking ) will require the help of the ICE to assist.
In traffic / town driving driving with zero electrical range left, you WILL feel the engine kicking in and out, that's a fact I am afraid.
In a HYBRID model and NOT a PHEV ( e.g. Toyota etc ) any speed that exceeds about 25 Mph and the ICE will be triggered, you have NO control of this situation.
I guess you have never driven one of them, brilliant "Self Charging Hybrid" then ?.
Don't worry, you have not missed much mate !.
Just in passing, did you know that the U.K. advertising agencies are the only body that has cleared the usage of the word "Self Charging Hybrid" to be cleared for use here ?.
All other E.U. counties have banned it !.
These are not just my feelings with regards to these cars.
Self Charging Hybrid's and PHEV's are two completely different beasts.
Take a look at the "Real World Figures" for average MPG figures for a S.C.H. - Not brilliant, I wonder why ?.
I was really impressed with the economy figures I received from my PHEV over a standard ICE car over the four years.
My wife's Fiat 500 used more fuel than my PHEV and it had three times the amount of power.
But honestly, my EV beats the PHEV hands down in economy and is silent ALL of the time.
Sorry, but S.C.H. cars are sold purely on hype surrounding it, not on the real facts.
To people who want to do their bit for the planet and are told they don't even have to charge up the battery in the car !.
"The car itself takes care of ALL of that Sir, you don't even need to plug it in either".
Customers who don't fully understand the whole EV thing - it's sad really.
Manufactures trying to hold onto the idea of selling petrol engine's for just a little longer.