Trouble driving in low speeds.

[Pakman]

Do any of you have trouble driving the car in parking lots/ low speeds. I'm talking about sub 10mph. This is my first time driving a manual supercharged car, and at low speeds at gear 1/2 it's kind of jerky. Does anyone else experience this with their stock cars or FI cars?

[Somerandom18]

My car stock does this. Just have to modulate the clutch like crazy.

NE Ohio represent.

[Ultramaroon]

Originally Posted by Somerandom18

My car stock does this. Just have to modulate the clutch like crazy.

NE Ohio represent.

+1

[daiheadjai]

I usually try to shift to second ASAP to avoid this... It has enough torque, and doesn't seem as jerky as first gear.

Sent from my SM-G930W8 using Tapatalk

[carsebuco]

That's why I take off in 3rd gear

[Pakman]

Thanks for the response folks. Glad it's not just me. I thought I was the only one experiencing this issue. I have to navigate my parking lot which has a lot of speed bumbs and it's always so jerky

[extrashaky]

There's a trick to it.

There is a phenomenon usually experienced in aircraft called "pilot induced oscillation." It happens most often in situations where very small inputs to the controls cause large changes in the state of the aircraft. What happens is that there is a very small lag in the pilot's reaction to the plane, and that lag is in phase with the aircraft's response so that it actually exaggerates the movement of the plane rather than diminishing it.

For example, suppose I'm flying an airplane and push the nose up a little, but it goes up more than I wanted it to. The plane will want to level out on its own, but I push the nose down. So now it goes down further than I wanted it do, so I pull up again. Soon I'm porpoising up and down and bucking all over the sky.

I say, "This damned plane! It's hard to control!" But it's really me causing the problem because my inputs are exactly in phase with the plane's response. Most pilots who crash planes due to PIO don't even realize they were doing it. It just seems like the plane went crazy. High performance aircraft, like fighter jets, actually have dampening in the control systems to make them less responsive, to "tune out" the danger spot for PIO.

Similarly, because of the excellent throttle response of our cars, driver induced oscillation happens with the throttle at low speeds. When the car slows down, the slightest input to the accelerator makes it buck up. The natural reaction is to let your foot off the pedal, but that makes the car jerk back down. Most people are not even aware that they're doing it and just think the car is jerky at low speeds. It doesn't happen at high speed because a small change in pedal at higher speeds makes a relatively smaller change in response. A tap that would jerk the car violently at 6 MPH could have almost no effect at 60 MPH.

The way to avoid driver induced oscillation is to change your thinking so that you anticipate what the car is going to do. You do that by driving through the bucking. Instead of trying to get the bucking under control, concentrate instead on keeping a steady foot that drives right through the oscillation and comes out smooth on the other side. The car will smooth out.

Try this:

Find a parking lot with little traffic. Practice maintaining 15 MPH in first gear. Then drop it down to 13. Then 10. Keep going until you start bucking, then try to drive through the bucking at that speed. At first it takes some concentration and a very light foot. But later it becomes second nature.

I can smoothly creep this car in traffic in first gear at 1000 RPM without bucking or lugging the engine. That's about 6-7 MPH. But I couldn't do it when I first got the car. It took some time to get to know the car's reactions while keeping in mind the tendency to fall into an induced oscillation.

[extrashaky]

Here's a video of a crash caused by pilot induced oscillation. You're essentially doing the same thing with your accelerator foot, hopefully without the crash.

[ame="https://www.youtube.com/watch?v=wxX4QvLylLY"]Saab Gripen Pilot Induced Oscillation during Flight Test - Landing Crash - YouTube[/ame]

And here's video of a pilot learning to "fly through" an oscillation. This company intentionally sets up the aircraft to make it prone to oscillation in flight so that the student can learn to recover.

[ame="https://www.youtube.com/watch?v=fiJeRHQ-q7w"]Calspan's In-Flight Pilot Induced Oscillation (PIO) Training - YouTube[/ame]

[Pakman]

This is quite informative. Thank you. What if you were approaching a speed bumb, how would handle that situation? Since we cant just drive through the oscillation since the car has to slow down for the bumps.

[JD001]

Clutch control in first gear, keep a steady gas pedal and modulate the clutch until you've over the stall state, then take your foot off the clutch pedal as you don't want to ride the clutch.


http://www.driving-test-success.com/...h_control.html

[extrashaky]

Originally Posted by Pakman

What if you were approaching a speed bumb, how would handle that situation? Since we cant just drive through the oscillation since the car has to slow down for the bumps.

Just as JD001 said above, it's clutch control and throttle control as you ease over the bump. Go as slow as you need to over the bump. But if it bucks when you give it a little gas and let out the clutch on the other side of the speed bump, don't get hung up on that. That's where the oscillation trap is. Instead, think about driving through the bucking to get to the smooth part on the other side. Do this enough, and you'll skip the bucking altogether and get right to the smooth part.

By the way, induced oscillation happens in steering as well. Ever seen an accident where someone fishtails all over the place and loses control of the car? Ever been in that situation yourself? That fishtailing is driver induced oscillation. You avoid fishtailing by driving through it to recover control of the car, just like you do with the throttle at low speed.

[humfrz]

Originally Posted by Pakman

Do any of you have trouble driving the car in parking lots/ low speeds. I'm talking about sub 10mph. This is my first time driving a manual supercharged car, and at low speeds at gear 1/2 it's kind of jerky. Does anyone else experience this with their stock cars or FI cars?

With practice, you will get the hang of it.

I suggest you try just using the clutch and brake and leaving the gas alone, to smooth things out at low speeds.


humfrz

[Ultramaroon]

Originally Posted by extrashaky

There's a trick to it.

Well put. OP, shaky's discussed this in the past but IMHO, he really put it together for you this time.

The secret to speed bumps is to anticipate the effect and compensate for it in your approach.

If you get it wrong, be ready to get out of the lurch by disengaging your clutch.

If you get stuck on the near side of the speed bump, I suggest taking a poke at the throttle and using the inertial energy of the flywheel to get you over it. That way on the other side, the engine's already slowing down and you can immediately disengage the clutch to prevent the whiplash.

That's my idea of feathering the clutch.

[Pakman]

Thanks for all the advice. Really appreciate it for a newbie like me. Will practice what's mentioned here and hopefully see improvement!