Pulsing when Accelerating

[jvincent]

I think you might be experiencing the car equivalent of PIO (pilot induced oscillation).

What that means is that your throttle/clutch timing is off and you are making the car jerk. To your original point, you may still be bad at driving a manual.

WTH do you need to be on the gas that hard pulling away from a stop sign anyway? If you were racing it would be WOT, but if you are just on the street, apply the gas smoothly and you should be fine.

[Jesse36m3]

Originally Posted by jvincent

What that means is that your throttle/clutch timing is off and you are making the car jerk. To your original point, you may still be bad at driving a manual.

This, plus the fact this motor is torqueless.

[carma143]

Originally Posted by jvincent

I think you might be experiencing the car equivalent of PIO (pilot induced oscillation).

What that means is that your throttle/clutch timing is off and you are making the car jerk. To your original point, you may still be bad at driving a manual.

WTH do you need to be on the gas that hard pulling away from a stop sign anyway? If you were racing it would be WOT, but if you are just on the street, apply the gas smoothly and you should be fine.

So even if I am not pressing on the clutch, the car should still be violently rocking, even if my foot is barely pressing on the throttle? (have to take foot competely off throttle to stop rocking)

Regardless of where I'm going 3/4 of WOT, if this does not happen in other BRZs or FRSs then this might be an indication of an underlying issue.

I don't mean to be rash, but maybe you haven't read my posts in this discussion?

Thanks for your insight. Any further input is greatly appreciated.

[jvincent]

PIO happens when you get on/off the throttle in response to the acceleration of the car, but the on/off is timing wrong so you cause the jerky behaviour.

So yes, even if you are off the clutch and manipulating just the throttle it can happen.

You say the car is rocking, but I assume you mean it is moving forward, just very jerkily.

[Tenament05]

Originally Posted by carma143

Regardless of where I'm going 3/4 of WOT, if this does not happen in other BRZs or FRSs then this might be an indication of an underlying issue.

This isn't indicative of anything until you have an experienced manual car driver get in your vehicle with you and try to replicate the problem.

The 'pulsing' you describe sounds much more like driver induced oscillation than anything else. The car is moving back and forth as the soft OEM bushings and drivetrain are deflecting and trying to deal with the sudden forces. I know what you mean, and I used to get that back in the day when I drove my old beater subaru, which was my first manual.

Bushings help tremendously, especially the famous "botox bolts" for GD/GG Imprezas. Similar products to ours that help against these oscillations are harder subframe/diff/outrigger/transmission/motor mounts/bushings.

[Estey]

Originally Posted by carma143

So even if I am not pressing on the clutch, the car should still be violently rocking, even if my foot is barely pressing on the throttle? (have to take foot competely off throttle to stop rocking)

Regardless of where I'm going 3/4 of WOT, if this does not happen in other BRZs or FRSs then this might be an indication of an underlying issue.

I don't mean to be rash, but maybe you haven't read my posts in this discussion?

Thanks for your insight. Any further input is greatly appreciated.

There is no underlying issue. You just need to practice and pay more attention to your timing with the clutch and gas. Eventually it will become second nature and you wont ever have this problem.
Anyone in their right mind would read your posts and come to this conclusion.

[tahdizzle]

so the consensus is: L2ManualTransmission

[STV3]

Originally Posted by jvincent

I think you might be experiencing the car equivalent of PIO (pilot induced oscillation).

What that means is that your throttle/clutch timing is off and you are making the car jerk. To your original point, you may still be bad at driving a manual.

WTH do you need to be on the gas that hard pulling away from a stop sign anyway? If you were racing it would be WOT, but if you are just on the street, apply the gas smoothly and you should be fine.

Ha, never knew there was technical term for that.

Happened to me once when I was a teenager and my friend had asked me to pick up his Fox body Mustang for him from the shop and bring it to where we worked at the time. It was only about a mile from where we worked and I did know how to drive stick, but I was bucking that thing all the way from the shop to our job. I don't think I ever got out of first gear lmao. I had a 1990 Celica GT at the time, so I wasn't used to the very stiff clutch pedal of the Mustang.

Oh and the car was smoking by the time I parked it

[carma143]

Originally Posted by jvincent

PIO happens when you get on/off the throttle in response to the acceleration of the car, but the on/off is timing wrong so you cause the jerky behaviour.

So yes, even if you are off the clutch and manipulating just the throttle it can happen.

You say the car is rocking, but I assume you mean it is moving forward, just very jerkily.

Yes, rocking = jerkily moving forward, in my previous reply.

From what I understand PIO occurs (at least in a manual car) when the driver is applying less/more throttle to the car because of the constant acceleration/deceleration that occurs, which is pushing the human foot forwards and back.

But I have tested this both with my foot firmly at WOT (pedal pushed as far as it will go) and at maybe 2% (barely even feeling the pedal). I still plan to take a video of this today with a GoPro showing the rpms, etc in different situations.

Sometimes I drive up a steep hill with a stop sign on the steep hill. I feather the throttle up and down slightly to start moving, which always works fine.

P.S.: My car failed to start today, after about 4 seconds of pressing the start button. The next time I tried, it worked fine. I don't know much, but could this be related to a bad spark plug, which was the cause to a similar problem found online.


Edit: I realize Yahoo Answers isn't the MOST reliable website, but I found this:

https://answers.yahoo.com/question/i...2015451AAg6AnP, specifically this:

"- Sudden Surges: Sometimes, you might experience a sudden surge in power without a discernible cause. This could also happen when your car engine problems show up by not accelerating properly, or responding to continuous pressure on the gas pedal in fits and starts. This kind of inconsistent engine performance is an indication of bad spark plugs. "

[D_Thissen]

Are you sure you are in first and not third?? Take your car to the dealership. Have them try it out.

[Tenament05]

Seriously bro just accept the fact that you aren't special and need more seat time.

Take your car to the dealership and have a COMPETENT mechanic drive it with you in the car.

[Bergen23]

It's nothing to be embarrassed about. When I first started driving stick, it'd happen every now and then to me. My dad would get in the drivers seat and he would drive it no problem. Then as more practice and conscious thought went into it, it happened less and less.

Plus, with a modern manual transmission, it's preeeeeeeeeetty damn hard for this rocking to happen

[carma143]

Originally Posted by Bergen23

It's nothing to be embarrassed about. When I first started driving stick, it'd happen every now and then to me. My dad would get in the drivers seat and he would drive it no problem. Then as more practice and conscious thought went into it, it happened less and less.

Plus, with a modern manual transmission, it's preeeeeeeeeetty damn hard for this rocking to happen

I don't typically go WOT when I don't want to. Only going up a steep hill have I sometimes pressed the throttle too quickly, resulting in this issue occurring. In a previous thread (when I thought it was the fault of the 87 octane gas) I commented how I almost crashed twice trying to cross a street at ~4 mph. It took ~6 seconds to cross the lane completely. Luckily I realized taking my foot off the throttle and back on allowed me to then exit at a quicker pace.

I have 1 friend who drives manual cars and motorcycles. He's a freshman at University of Colorado: Boulder. I asked him to drive my car and the first try he put on too much throttle, panicked and stalled. The next 4 tries he created the violent pulsing I've been talking about, followed by stalling. He quit after that, mutually agreeing so he wouldn't cause damage to my BRZ.

For any one else interested, I am planning to have the Subaru dealer test out the car to absolutely make sure this is normal, because it's preeeeeeeeeetty damn easy for this rocking to happen.

[D_Thissen]

Maybe make a video so we can see what's going on.