delay in acceleration

[rh71]

Is there a reason some test drive cars have a slight delay when stepping on the gas pedal? I don't know if I can attribute this to the break-in period where the computer is learning your driving style... is the engine too weak for the car? Is it an engineering problem? Would a twin-turbo engine directly address this problem?

My car is 13 years old now and definitely has less torque/hp compared to cars nowadays but it really goes when you step on the pedal (not even hard). I haven't driven many new cars in the last few years but my dad's newer MPV feels like there's nothing behind it either when you step on it... sort of like a mechanical (direct-it-to-go) vs. electronic (send-over-a-message-to-go) feeling.

I remember feeling this way last year driving an RX400h at the Lexus event and more recently an X5 3.0si. Tell me they're not all like this. One more question - would diesels be worse with this acceleration lag issue? I know they're known for great torque, but will there be a delay?

 

[helpme]

Originally posted by: rh71
sort of like a mechanical (direct-it-to-go) vs. electronic (send-over-a-message-to-go) feeling.

Many new cars are Drive By Wire, which IF tuned to react slowly, can produce this type of feeling. (Gas pedal is connected to the computer, which uses a servo to control the real throttle)

 

[jagec]

Originally posted by: rh71
Would a twin-turbo engine directly address this problem?

Make it worse...turbo lag.

What you describe is probably the electronic throttle, but it could also just be the effect of a smoother, quieter engine in a heavier car that doesn't "jerk" you back in your seat as much, but has the same amount of acceleration.

 

[sniperruff]

that lag was probably caused by the auto box dropping a gear or two before it can rev up.

 

[rh71]

^ it was from a dead stop though.

Also, about turbo lag... the twin turbo is sequential so there's no/little turbo lag (made for that purpose)... but doesn't the smaller turbo kick in after the initial gears only or is it for torque too? Again, this is from a dead stop that it's even noticeable.

 

[spidey07]

It's the electronic throttle.

 

[Fenixgoon]

Originally posted by: spidey07
It's the electronic throttle.

yep, my guess as well.

one of the major reasons i love my 99 passat - cable throttle FTW! :heart:

 

[overst33r]

Originally posted by: Fenixgoon

Originally posted by: spidey07
It's the electronic throttle.

yep, my guess as well.

one of the major reasons i love my 99 passat - cable throttle FTW! :heart:

They're not all like that...

The S2000 I drove had no delay whatsoever, no difference in between the cable and drive by wire throttle...

 

[LordMorpheus]

I think the auto box downshifting is the most likely culprit. An electronic throttle can be fast enough that you wouldn't be able to tell it apart from a cable linkage.

 

[rh71]

Can a "learning computer" during the break-in period fix this in any way?

Will a more powerful version of the same vehicle have the same problem?

 

[spidey07]

Originally posted by: mariok2006

Originally posted by: Fenixgoon

Originally posted by: spidey07
It's the electronic throttle.

yep, my guess as well.

one of the major reasons i love my 99 passat - cable throttle FTW! :heart:

They're not all like that...

The S2000 I drove had no delay whatsoever, no difference in between the cable and drive by wire throttle...

I've got a manual TL and there is no delay. The auto was a different story however.

Plus some traction controls are so sophisticated they won't really let you stomp it when combined with electronic throttle and decent motor. It will absolutely NOT let you break traction.

 

[Arkaign]

I tested a 2006 M5 with the SMG, and it was incredibly responsive with the M mode on.

 

[natto fire]

My guess is 50/50 electronic throttle/placebo.

 

[LTC8K6]

I'm guessing that his car has excessive throttle tip in to make it seem quicker than it is. This was a common trick used by some mfgs. It's hell in snow and ice. Instant loss of traction.

Cars with proper setups would then seem to react slowly to him.

 

[GoatMonkey]

In some new cars this can be fixed with a computer flash. It's a common complaint on 2005+ Mustangs. Getting a performance computer flash will fix it in that car at least.

 

[Demon-Xanth]

Originally posted by: LTC8K6
I'm guessing that his car has excessive throttle tip in to make it seem quicker than it is. This was a common trick used by some mfgs. It's hell in snow and ice. Instant loss of traction.

Cars with proper setups would then seem to react slowly to him.

The supercharged Frontier used an elliptical linkage on the throttle body to make it feel more powerful than it was. 1/2 throttle was really closer to 3/4.

 

[jtvang125]

My car tends to have this problem during cruising speeds. It's like the computer needs to think about what it wants to do and then the transmission has to drop a gear or two before the power kicks in. This seems less apparent if I have the car in Power mode.

From a stop the car does not have this problem though. Instant power although the traction control will not let me break traction.

 

[Aikouka]

My car feels rather normal and it has electronic throttle control. Although at times there's definitely a delay in the torque converter engaging again and it feels almost like I'm letting out the clutch too slow (if my car were a manual). This doesn't happen under slow acceleration though... usually only a little faster than average acceleration.

 

[Zenmervolt]

Originally posted by: rh71
^ it was from a dead stop though.

Also, about turbo lag... the twin turbo is sequential so there's no/little turbo lag (made for that purpose)... but doesn't the smaller turbo kick in after the initial gears only or is it for torque too? Again, this is from a dead stop that it's even noticeable.

There's still lag with a twin-turbo setup. Even a "low RPM" turbo won't really spool until about 2,000 RPM (while larger turbos may wait as long as 3,500-4,000 RPM to fully spool in lower gears when there's less engine load), so you'll still be losing some of the engine's "punch" when trying to get off the line quickly.

Most of the complaints about electronic throttles are that they don't close fast enough between shifts (an emissions thing), this is the first time I've heard a complaint about them not opening fast enough.

ZV

 

[programmer]

I just rented an Impala and it had the same thing. Press the accelerator and nothing for a second or so, then vroom. I know it was a rental, but I was not at all impressed with the Impala. "Basic Transportation"

 

[ayabe]

Originally posted by: Zenmervolt
Most of the complaints about electronic throttles are that they don't close fast enough between shifts (an emissions thing), this is the first time I've heard a complaint about them not opening fast enough.
ZV

Yeah I think all the cars with the electronic throttles have that to some degree.

It took a while to get used to mine, especially because it's setup to give you like 75% throttle when you depress the pedal 40% or something like that, couple that with a turbo and sometimes it can be a bit tricky keeping traction in first gear on a cold morning before the tires are awake.

 

[LS21]

theres lag if theres turbo. theres electronic controlled throttle. theres the sensitivity of the gas pedal. theres gearing and characteristics of the motor. lots of different possible factors