str8line

I noticed a few people mentioned this in another thread.

My wife told me she got pretty scared the other day when she went to accelerate out of our neighborhood and onto a busy street and there was a lengthy delay in her GL320's response to her flooring it.

I've noticed it too: You press on the accelerator and after what seems like a 1+ second delay the vehicle jumps like a bat out of hell. Impossible to modulate, impossible to get rid of the delay. You either have to drive like a grandma or get shot like a bullet.

Who else has noticed this and has anyone tried to fix it?

StevethePilot

That's a serious lack of creativity on your part!

What some of us have come up with is, half throttle at the start as opposed to mashing down on the pedal actually gives some better off-the-light because instead of waiting for the torque converter to engage and the turbo to spool up, it allows the engine itself to give something to the equation. Once things start rolling, swiftly but smoothly add lead to the foot and you should get a smoother start followed by rapid acceleration. (Rarely do I have to put in any more accelerator once the maneuver's started as the torque converter and turbo come on line and add the boost I need. Now, as for cowbell, I do need more of THAT ...)

Your next option is the two-footer option, which is where you spool the RPMs up to the 1700-2100 range with the right toes, while holding the honey back with the left ones. This should produce that neck-snapping start we're all used to from normally aspirated engines.

Yacht Master

The easy fix, is to wait for a reasonable space in traffic, and not have to enter like an ******* at full throttle.

BTW GL320 is my Grandma's whip too.

str8line

My neighborhood can be a b#$%^ to get out of. But thanks for your ingenious advice.

str8line

Half throttle at the start yields anemic acceleration, and I can't see my wife brake-torqueing.

The fact that she would even need to consider either of those options for some off-the-line pep is a joke.

I've been driving diesels in Europe for over 10 years and my truck is a diesel, never had a vehicle do this.

Danno4x4

My wife really likes the diesel GL... She got used to the acceleration characteristics in no time and actually enjoys the two pedal technique. But, perhaps the GL 320 is simply not the right vehicle for your wife... I suggest you take it for yourself and buy her something with normal non-turbo acceleration characteristics...

str8line

I guess you guys are ok with it, that's cool. I'm not. But don't blame it on the diesel or turbo lag and act like all diesels do it, that's NOT the problem.

StevethePilot

Welcome to the US. I don't suggest leaving it half throttle (well, maybe slightly more) but if that doesn't work then see above advice from Yacht Master.

StevethePilot

We don't really have a plethora of diesels to test it against. US built diesels don't even have common-rail injection until next year. BMW may or may not be bringing something in. VW's diesels (other than the ultra-rare V10 Touareg) are generally in low-weight cars anyway. So what is it, what would cause this off-the-line pause, if not the torque converter or the turbo-lag or whatever?

jpeardm

Most single TD's with auto trans will inherently experience this hesitation unless the boost threshold is reduced to near idle rpm. There are designs to provide for this including electric supplemental turbo units that keep the boost up at less than exhaust threshold. There have been Euro vehicles including the Volvo XC 90 that also had severe hesitation problems from a standing start. Some of this can be reduced through software changes or outright tuning. I'll wager that MB is or will be working on this soon. It definately can be improved upon and should be.

StevethePilot

I've specifically asked while they're trying to determine the cause of my shimmy, why there's such a huge delay when I mash my foot down? Before I pick it up I'll get an answer. See the "shimmy" thread for more info on that.

carpersn

I don't think i've noticed anything quite as bad as you are describing...one suggestion though...your wife may have "taught" the adaptive transmission bad habits. Try resetting the adaptive transmission. THere is a procedure outlined on the forums here for doing it that involves holding the accelerator down while shifting the key into the accessory position...short of that, ask the dealer for any software updates for the transmission and get them to reset to factory defaults. I was just thinking to myself the other day how much i like the transmission/off the line oomph. 6500 miles and counting...

AsianML

Turn key to position 2,
depress accelerator all the way for about 10-15 seconds
release pedal and turn key to position 0,
leave the key in for a minute to two or three minutes

str8line

Thanks AsianML, and thanks Carpersn.

I'll try that, but I wonder if that affects the shifting only and not the response from a standstill. I'm waiting to hear from the dealer to see if they have a remedy.

StevethePilot

After mentioning the delay in acceleration to my SR, he said they'd downloaded some software updates that address "hesitation." Once I get the beast back, I'll let you guys know what difference it's made.

STP

str8line

Cool!

StevethePilot

After the software update, there is still a delay. However, it's about 2/3 of what it used to be, and with my confidence in Phoenix Motor Company's service department to actually address any issues beyond Service A and Service B (can you imagine?), I'm making an appointment with Schumacher on Monday to see what they think of the two problems.

Again, I'll keep you guys updated.

Can Drive 55

Shouldn't he turn off the key before releasing the pedal? Here is the step in question the way I copied it a while back.

Turn the key to the "off" position (don't remove the key), then release the gas pedal.

Note: I have never noticed anything from doing the re-set procedure in my car. If it has ever done anything, it was subtle at best. Maybe mine is just always ready, like a cocked weapon.

AsianML

You already have a fast car. I have the slowest car in the world. Anything I can do will help.

I've always done it by releasing the pedal then turning the key. I'll try it the other way and see if I get the same results.

BETO

Dangerous? please, you need to learn how to drive this type of vehicles. It's not a powerful 400hp V8 pulling a heavy car, nor a powerful 6 (in-line or v) pulling a light car. I guess your wife never drove a four cylinder car with auto tranny. Wanna try my Prius or my old Sentra? Heck, even my V8 Land Rover is sluggish off the line, not to mention climbing up-hill on the freeway, going up El Cajon pass is a PITA, specially if I'm loaded, not to mention when I pull my race car.

jhcicco

Found this on the Benzworld.org site (Thanks to Newbie_2_MB - Jen) on the oil dip stick thread.

From the service bulletin: Recommends not using the two pedal technique.

Aug 21, 2007 S-B-27.00/101 MY All Models All With Transmissions 722.4/5/6/9 Do Not Operate the Accelerator Pedal and Brake Pedal Simultaneously. Heats up transmission, may damage torque converter/transmission, reduce service life

scottybdiving

QUOTE=str8line;2345283]Half throttle at the start yields anemic acceleration, and I can't see my wife brake-torqueing.

The fact that she would even need to consider either of those options for some off-the-line pep is a joke.

I've been driving diesels in Europe for over 10 years and my truck is a diesel, never had a vehicle do this.[/QUOTE]

I too have been driving diesels for a while (25 years over 800,000 miles) going back to the pre-turbocharged days. All of them were American made, in large pickups except for the 1981 Toyota pickup, when I was in college (had to turn off the AC when pulling a hill). All of them had the notoriety of turbo lag, especially if you floored it. This includes my 4 month old 2007/2008 Duramax that has common rail injection and a variable geometry "smart" turbocharger with computer controlled turbine vanes. This is supposed to reduce the lag time but it is still there. Once it spools up, it takes off like a sports car and is scary fast.

Ford's new 6.4 Twin Turbo has a smaller 2nd turbo that is designed to spool up at low RPM's and eliminate the lag and it does seem to work well. This is a common age old problem for turbo-diesels, and they are all trying to reduce or eliminate it through technology. Kind of like shutter lag on digital cameras.

When I test drove the GL 320 and ML 320, it wasn't noticeably worse or better than what I am used to driving. Since my wife has been driving a diesel for 10 years, I don't think she will have a problem with it either. I think it is something you have to be aware of and comfortable with. It is a compromise for having a 3.0L engine that can make this much power and yield this kind of economy.