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I drive a relatively average powered automatic transmission front-wheel drive car; my (naturally aspirated) engine delivers maximum torque at around 5000 RPM. I performed the following test (remaining in first gear) a few times comparing two situations:

  1. I accelerate the car to about 35 mph, which is just above 5000 RPM (max torque point), release the throttle pedal, and then wait for a moment. then (while the engine is at almost exactly) 5000 rpm, I floor the throttle as quickly as possible, resulting in a very feelable jerk and my tires screeching while the front wheels slip momentarily.

  2. I bring my car to around 4000 RPM. Then leaving my foot on the pedal flooring it, accelerating through the 5000 RPM mark; note that when my car is at 5000 RPM, the throttle pedal is fully depressed. Resultantly, the jerk feels significantly less violent, and almost no screeching sound is produced, i.e. the tires are not slipping at all.

My question is then why does the engine seemingly produce more torque when it is suddenly floored at max torque point vs. accelerated through max torque point? At 5000 RPM, with the throttle floored in both cases, and in the same gear, an equal amount of torque should be delivered to the wheels; yet only the wheels only slip in case 1.

Furthermore, since the car is accelerating in case two relative to case one, there should be a load transfer to the rear, causing lower front-wheel traction in case two, and thus higher propensity to slip. Still, the wheels slip solely in case 1, implying an even higher torque difference between the two cases.

I am forced to believe that this is either due to some odd effect in the torque converter, or something like a heat buildup in the engine in case two causing a lower torque to be produced. I am, however, entirely unsure about either of these, and would like to get to the bottom of this occurance.

Thanks in advance!

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  • $\begingroup$ Are you engaging an automatic trans at 5000 RPM ? The trans stall speed is well below 5000 RPM. $\endgroup$ Jul 5, 2022 at 23:11
  • $\begingroup$ My apologies for the lack of clarity, what I meant is that I actually accelerate the vehicle until the engine reaches just above 5000 RPM (which is about 32 mph or so for me), then release the throttle briefly, and then floor it. $\endgroup$
    – naahiv
    Jul 5, 2022 at 23:23

1 Answer 1

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You are upsetting the dynamics of the vehicle, not getting more power.

Releasing the accelerator at 5000 rpm makes the car slow down. Now when you floor it again you are pushing against the car's slower speed. You are unloading the front suspension after you loaded it up by slowing, possibly in a bounce. This results in chirping the wheels. You can't get more power by cycling the accelerator, but you can upset the vehicle.

This does all come under the category of tearing up the car.

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