My wife has a supercharged V6 Buick engine and her air conditioner didn't work well at all. I bought the deal at the auto parts store where you can top off your own compressor. Thing went from blowing 65 degree to 45 degree air with about 10 minutes of effort.

I have driven through Florida and Nevada in the summer in four cylinder cars and was fine.

The larger, more powerful engine can run a larger AC system without affecting acceleration/cruising. So it would work better.

But if the volume being cooled was much larger - say a minivan vs a compact sedan - Then the increase in cooling power may not make up for the larger volume of hot air to be cooled.

The issue is really the power needed to run the AC compressor. The larger the compressor, the more power required.

Generally, 4-cylinder engines make less power than 6-cylinder ones. So, auto makers install smaller AC compressors in those cars, to prevent robbing horsepower needed to move the car. Smaller means less cooling power.

In smaller cars, that's probably not much of a problem. In larger cars, though, the difference could lead to the result you're experiencing. If you add very hot weather, as you seem to have, the difference would seem greater to the driver.

It's a pretty big vehicle and it goes 80 mph up a mountain in 4th gear (out of 5). No heating and cooling issues either. Toyota created that in-line 4 in the early 60s and it remains one of the best performing engines in the world.

But there are a lot of variables. I have the same issues with hot-natured and hot climate.

I think it depends on how much power the four cylinder dedicates to cooling power. You can get it cool enough if you don't mind a zero-to-sixty time measured in minutes.

I also think the relative size of the car matters a lot. A four cylinder is more able to handle the small interior of an economy car but will not cool a large sedan or mid-SUV

I try to get hybrids so the electric motors can compensate for the underpowered 4-cyl.

I once had a Honda Pilot that was a 6-cyl but would shut off 3 cylinders at cruising speed. I thought that was pretty slick and you could not even tell it was happening. Before anyone environment shames me, I am in the contruction industry so I need a little bit of capacity and off road ability. I currently have a Hybrid RAV4 and love it.

I've told people that the 4 cylinder engine on my Chrysler convertible will go zero to 60 in under 3 seconds. Provided i drop it out of a plane.

The compressor is roughly the same size and only draws a few horsepower. The bigger factor is coolant charge, type, and evaporator size.

i live north as you might have figured but i open a window to let the solar oven that a car is spill out so the ac does not have to work quite at hard to make you cool.
obviously i close the window when the ac starts to work

And our 8 cylinder Tundra.

And I live in Florida.

I just think modern compressors are not the energy hogs they used to be. I remember in my 70’s vehicles I would feel a real loss of power when the compressor kicked in that I do not feel now.

But I am a plant science guy so what do I know?

We never have a problem with air conditioning. With my Prius, I still get over 50mpg on highway driving with the air conditioner on.

Cooling is about the same, or I just never noticed. Warming is a different story up here in the snow belt of Michigan. 3 miles and I have some warm air coming out with the 4. More like 6 or 7 miles for the 8 to warm up.

If you have no idea how things work under the hood, it's probably a good idea to ask someone who really knows.

However, I would like to point out your sister's glaring logical fallacy. Your sister's car's AC may very well work better than yours does and her old one did, but that doesn't mean it works better because the new car has six cylinders.

2L Ecoboost 4cl engine and a 2006 Toyota Tacoma with a 4L V6. Both ac work good. Maybe I am wrong but I tbink the old R12 coolant worked better.

The compressor runs on a belt connected to the engine that spins it. Just like the alternator.

It is possible they use different compressors but I would be surprised if they do.

It also sets outside in the sun all day and most of my commute is at 30 mph or less.

It eventually cools down, but much quicker at highway speeds.

I echo the advice above about having your coolant and compressor checked.

The AC does sap more performance power from the 4 then it does from my other vehicles.

Subaru WRX STI is about the same.

Both come with air conditioning.

Check your AC.
They will fix you right up.
Sounds like a simple fix.

I have a 4-cyl Caravan (would never do that again!), but in the summer (and it gets pretty hot here), the AC works fine. Now, when I have to climb a hill, 4 cyl suck! Never buy a van with 4 cyl!