arentz07

I wouldn't recommend going into neutral as that would cause more wear on the transmission components when going from neutral back into drive, especially if you're in motion. If you just want to rev the engine while sitting still, park does that just fine. In drive (D), if you want to hold the brake and rev the engine while sitting still, it's also possible, but I would not do this often if at all due to the stress it puts on your car.

LaZeR

Hi, if you guys review the initial opening post at the very top, do you know HOW exactly they designed & engineered such a drastic change when you manually downshift. I'll paste the snippet below...

"... when you manually downshift Lexus really let's ya "feel" it eh Wondering how they designed & engineered the latter... some kinda choke, less gas, etc?".

THANKS!!

Olasek

And what exactly is this drastic change??? What is 'drastic' and what is 'change'.
Please explain better what you mean.

LaZeR

OK - maybe I'm not explaining it right. What I mean is this:

• when you're in manual shifting but start to slow down for a red light or stop sign the car automatically downshfits for you and it's nice and smooth, as you can see on the gauge, as well as read in the owner's manual, so you don't really have to bother with downshifting ~ it's not necessary.
• BUT, if you're in manual shifting, and start to slow down for a red light or stop sign, but manually downshift instead ~ i.e. don't let the car control this ~ from say 6 to 5, or 5 to 4, or even 3 to 2, what I mean is there's a drastic slowing down of the car, it almost JUMPS slower, like the brake is being applied even when it's not, and it's NOT nice and smooth, almost feels like you're doing something wrong. I'm just wondering about the technical details that controls this.

arentz07

I'd say it's time to get back on topic.

To seriously answer your question, the jerk or jump that you feel is from the engine speed not quite matching what it should be for the gear the car is in. Rev matching solves this issue. If you are in M (manual mode) and downshift, the car should do this for you, or if you are in D and in Sport mode and driving it kinda hard.

FWIW, Lexus didn't engineer it in; it's a fact of how engine and transmission interact.

des2k3ised

Moving around town at low speeds, manual mode is pretty jerky

Olasek

Because humans generally can't shift as smoothly as computer.

nathantse

True, shifting from 2nd to 1st jerks the car. Feels like when you're hard braking.

Not sure if I'm shifting right lol. Other than that, freeway shifting is pretty smooth.

Mrg02d

I paddle shift and engine brake most of the time that I drive. I can downshift better than the car can because the car can't read my mind. When I see a potential need to NOT be in dang 8thgear, I'll downshift and then hit it.

I usually use M mode for times of high intensity driving, so I don't have to constantly watch the gear that I'm in.

arentz07

I've always wondered why, when driving the car hard, the shifts are quick and smoother (though not seamless), but are jerky at low speeds. It's possible that it shifts more slowly due to compensating for the torque-converter lockup? Random guess.

Yes, I agree, it's much easier to control your speed (i.e., not accidentally go too fast) if I'm the one shifting. In addition, the AI-SHIFT thing, as you mentioned, is a bit slower than a human at downshifting into a corner. I am actually impressed that it works as well as it does.

Solara350

2morrow start your car warm it up, put in manual shifter, acel the gas gently and shift 2nd at 1.200RPM see if the car jerks, 3rd gear at 3.000RPM , if you smooth on the gas shift gear like Computer the car will be no jerk.

arentz07

I think he was talking about shifting from 2nd into 1st, not the other way around, which it sounds like you are saying based on the fact you mention using the gas. TBH, you really shouldn't shift into 1st unless you're coming to a stop, or in an emergency (when you probably wouldn't be in manual shifting mode).

dizlex

The computer is still doing the shifting, in manual mode. The reason it's jerky is that manual mode in the 8-speed is with a locked torque converter, by design. More "sporty" but less smooth. It's a reasonable design, but, let's face it, the 8-speed is a bit dated in design, and not the greatest tranny around.

dizlex

Same here. The paddles are also useful just to get the revs out of the cellar (or out of the annoying torque dip 2000-3000 RPM) for "crisp" but smooth acceleration. Simply pressing the accelerator often results in two changes down, and excessive revs and neck-snapping.