My car is more powerful in warm days?

Question

My car is usually more powerful in warm days and sluggish in wintertime. Isn't normal?

I have a 96 Jeep Grand Cherokee

Answer 1

That is not uncommon on older cars for a couple of reasons.

1) As the engine wears the gaps between the moving parts (pistons/rings, valves/heads, etc) grows. In most cases you loose efficiency or power - for example if the pistons are not snugly fitting in the cylinders you will loose compression as the cold air is pushed around them instead of being jammed up into the combustion chamber). As the engine warms the metal expands and that gap will, essentially shrink. Thus you have better compression which means a bit more power.

2) As metal expands in other areas you get other effects. Gears mesh better and, just as with people, old joints begin to work better with use.

3) Lastly the oil and crud inside your engine will actually serve as glue until it warms. Like trying to run thru 3' of water instead of 3' of open field, it will slow down the engine.

4) Conversely cold AIR contains more oxygen then warm air.. so that makes for a less powerful combustion in the engine (which is why race and performance cars have outside ram scoops to force more O2 into the carb.)

All of these contribute or effect power as the engine is warmer (or colder).

does that help a bit???


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Answer 2

I have had many different cars of different makes and there's only one thing that remains consistent: a complete lack of consistency. They're all different.

It could be an illusion because, in warmer weather, your shocks are looser and therefore the back end of your Jeep dips harder when you do accelerate making the the acceleration feel like it's harder and therefore the truck more powerful. I know it sounds strange, but try riding in a car or truck where someone has only changed the front struts/shocks and not the rears. The car feels faster because the back end dips harder which is the main thing your body is recognizing as "fast." A lot of times the older cars (60's-70's) feel so much faster than modern cars because their rear suspension sucked.

Answer 3

normally its the other way around. an engine performs better at cold temperature, because of the cold air. Thats why they install cold air intakes, to deliver cold air in the engine, and yuo get like 5-10 %increase in power.
But in your case, it depends. Do you by chance live a mountain region. Because is you do, the higher the elevation, the slower the engine. ;)

Answer 4

it may be less powerful when you first get in and go in the winter because you havent let your car get up to temperature but generally in the winter you should have a little more power. friction and heat are the two biggest robbers of horse power.

Answer 5

On cold days do you run the defroster? If so, you are also running the A/C compressor which takes a lot of your power away.