czachari

Noticed it before, but today I decided to try and narrow it down. In 6th gear at 2000 rpm going slightly uphill so the car does not just roll, press the gas to WOT. There's major ruckus coming from the engine like vibration/flutter. It lasts until the engine gets closer to 3000 rpm.

This does NOT happen in any other gear while going to WOT at ANY RPM, not even 1000 RPM.

This is the 1.8L Engine. Needless to say, I am concerned. The car has NO engine mods, it's completely stock.


Thanks

CZ

adamrs80

I could be wrong but it sounds like your just bogging your engine down. If you're going uphill in sixth and flooring the car then I would think that would cause the major vibration you're talking of. Auto's would downshift and it wouldn't be a problem. This might be totally wrong but from what you described it sounds like you're just in the wrong gear...I know thats a really simple explanation and might not be what you're talking about but if it does the same thing if you put the car in 4th going 5mph or something along those lines that I wouldn't worry about it just shift more.

Lynn

adamrs80 is correct. You are on the wrong side of the torque curve, and are lugging the engine. This is very bad for the engine. It is asking you to shift to fifth gear. On the 1.8, you should try to keep it revving over 3000 when accelerating.

czachari

When going to WOT at 1000 RPM, it bogs down in ANY gear. This is different. The engine actually vibrates and produces a droning flutter sound which is different than a bog down where basically the timing is retarded to avoid pinging and you lose power.

In the case I'm describing, I can hear the S/C going full bore trying to produce power, the timing is not really retarded but something in the engine compartment must be vibrating violently.

ONLY happens in 6th gear from 2-2.5K at WOT, it dows not happen at any other other RPM range in any gear.


CZ

Lynn

In that case, I have no idea.

Outland

You BOG at wideopen throttle at low RPM's for several reasons, timing isn't one of them. There's no pinging involved.

Quote:

In the case I'm describing, I can hear the S/C going full bore trying to produce power, the timing is not really retarded but something in the engine compartment must be vibrating violently.

It it jerks heavily, and drones, that's LUGGING. Youre trying get the engine to pull when it doesn't have the power.

mctwin2kman

WOT at 2000 RPM in 6th gear is the problem. The tourque curve on the 1.8 does not start until 3000 RPM. Once the engine is above 3000RPM are you ok? Personally if I am on the highway and want to pass someone and floor it and am under 3000 RPM I downshift to 5th. The vehicle travels well in 6th until you get under 60MPH or so. I never get a vibration though just a little slower on the get go. If I really want to buzz by someone I drop to 4th, and the car just flies up to 90-100.....

Lynn

For some reason, I didn't pick up on this yesterday. It is impossible for the supercharger to be going full bore when the engine is at low rpms. The supercharger is mechanically connected to the crank. If the engine is turning slowly, so is the supercharger.

czachari

First, let's say that I know what bog down is since I've been driving small displacement 4 bangers for more than 12 years. Next, yes, the 1.8L does bog down at WOT below 3000 RPM. The reason I posted the first message is that what I am experiencing is not bog down. It's bog down squared. I can hear the S/C sucking wind, I experience the typical bog down lack of power but at the same time I feel/hear severe vibration ( like when a 4-cylinder engine is twisting on its axis during acceleration ) but the vibration seems to resonate so that it's on/off, on/off, on/off in that pattern. The visual image that enters my mind when it happens is that something is twisting back and forth in the engine compartment.

The main question is if it is bog down, why is it so different in this gear and RPM range? Why is bog down different at ALL other RPM ranges and gears.

To make the question more obvious I have to mention that going WOT at 1000RPM in 6th gear does not produce the droning. Once the RPM hits 2000 then the resonance starts.

Thanks for your help so far. Can we get some more people with 1.8L 6 speed to try this?


CZ

dmatre

As you car is still under warranty, and the problem is easily reproducible (every time at 2k-2.5k rpm), I would take it to the dealer for diagnosis.

Continuing to drive with this problem could lead to undue stress on the engine/mounts/transmission. This stress may not cause failure now, but may reduce the component life - leading to failure when the car is out of warranty.

My suggestion: Let the dealer figure it out and fix it, before any further damage is done.

Kar don

is this your first 6 spd? WOT at 2k rpm is def ur engine bogging down, read the owners manual. It prob vibrates worse cuz it is a supercharged engine.

mctwin2kman

It will vibrate the most at the resonance frequency of the moving components. Since that is the lowest gear ratio and the tranny internals are spinning almost as fast as they can, this will cause a resonance. Thus causing a vibration throughout the driveline. It is most likely normal for that RPM range in that gear. Normally you should not be at that low an RPM in 6th gear, and that is why the rest of us do not notice it. Downshifting is your friend. And that is the reason there are 6 forward gears. Also the reason that at cruising speed the RPM's are above 2500 RPM, at least in mine it is.

czachari

When cruising I like to be in 6th @ 2K RPM to conserve gas. When I am driving for fun I always keep it above 2.5K RPMS. It's just that this vibration is VERY uncivilized for a Benz. I'd like to see if any of you can duplicate it. If yes then I will leave this subject alone.


Thanks


CZ


p.s. This is my first 6 speed. All my other cars have been 5 speeds. I've only owned one automatic in my life.

mctwin2kman

I will test mine at lunch. You are saying between 2000 and 2500 RPM in 6th gear? See I am in 6th when I am above 60-65 MPH, other than that I do not use it. Plus you are not saving gas if you need to five it a ton more to accelerate past the bog down point since you are giving it WOT, you are actually using more gas.