What happens inside an engine during downshifting?

Answer 1

Well, your pistons and valve train are moving so that your car can stay running.
Oh! and there's probably some type of fuel running through to the cylinders and exploding upon spark.

Answer 2

Basically the motor is at idle when you are braking or down-shifting.

When you engage the transmission with a clutch or crank down the automatic from Drive to L3 or L2 or L1 you are forcing the motor to run at a higher RPM than idle and in doing so you are using the internal motor parts, pistons, connecting rods, crank shaft, to slow down the car via the transmission and to the drive shaft(s).

The car does not burn more gas as if accelerating, but the stress on the motor and transmission and drive shaft(s) is immense. Very much the reverse of drag racing and the stresses put on a motor and drivetrain during a 1/4 mile run. The only difference is that the reverse surfaces of the transmission gears and driveshaft bearings and differential gears and axle bearings are taking the wear and tear.

Brakes are much cheaper than motors and transmissions and other drivetrain parts.

I noticed that when driving my 1976 Suburban and later my 1985 Chevy truck with the same souped up 454 motor, the rear axle bearings had to be replaced when the axle seals started leaking into the brake drums. No other reason except I drove them hard and would use the tranny to slow the vehicle down if I was horsing around at high speeds.

There's always a price for high performance and the harder you push that envelope the more prone you are to unscheduled repairs and break downs.

I've seen transmissions catch fire from being pushed so hard the internal fluid burst into flames. And I've seen transmisson pans come flying off followed by a handful of gears.

Good Luck!

Answer 3

The engine spins at a higher RPM = revolution per minute, The same thing when you accelerate before you up shift. Your compression does not change at all. If your engine is 10 to 1 compression it is 10 to 1 at and idle, 10 to 1 @ 1,000 RPMs, 10 to 1 @ 6,000 RPMs. If down shifting hurt or prematurely wore out parts them why do all truckers do it?

Answer 4

when your on a gear like 1 or 2 the engines crankshaft moves alot more then the cars wheels, so when u go to a higher gear like 4 the crankshaft is coming as fast as the wheels. so gears like 1 and 2 have alot more torque, but spin less fast, while gears like 3 and 4 means the engine is almost spinning as fast as its wheels


edit: but that didnt really explain much, so when u down shift, the engine wants to keep spinning the wheels as fast as they were going before, so now it must work even harder to keep them spinning that fast, so in turn, that means the engine must try harder seeing as how its not spinning the wheels in a 1 to 1 ratio, more like a 3 to 1. so its trying harder as opposed to 4th gear where 1 turn of the crankshaft if 1 turn of the wheels. 1st gear would be 3 turns of the crankshaft for 1 turn of the wheel

Answer 5

the hamsters go really fast. jk. u get high compression, the rpms go up. thats about it. its been debated whether to use the engine to slow down or the brakes. car talk says brakes as they are alot cheaper to replace than engine.

Answer 6

inside the engine? well, rpms jump up because of gearing, but nothign really changes in the engine.

Answer 7

more fuel mix gets pumped into the engine to match the sudden jump in rev. (RPM)