Where does the level come from?

1250 Views 14 Replies 7 Participants Last post by kmagnuss, Dec 13, 2009

waveydavey

Discussion Starter · Dec 12, 2009

This is just curiosity but:
Our cars have four height sensors that measure the gap between road and body - basically; I know its chassis to axle but it is essentially road to body.

We park on an uneven road and the car self levels - one of the coolest features of the suspension.

What I have never understood is why doesn't it just follow the contour of the road?How does the suspension system know that the road is not level and it needs to compensate? To the best of my knowledge there is no level sensor?

Not a problem or needing help or anything but I would be interested to find out.

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RRToadHall

· #2 · Dec 12, 2009

An uneven road has nothing to do with our system. You can park with one tyre up on a log and it will make no difference. The system works from the frame to suspension gap.

Example: the neighbour keeps you up all night racing his motorbikes around his property. :evil: The next morning you "accidently" run him over as he is getting his paper. After loading his fat beer swilling body into the boot, the back end of the truck drops from his weight. The sensors note that the truck has dropped at the rear decreasing the distance from frame to suspension. The EAS then increases air pressure in the rear bladders to raise the frame/truck returning the distance to normal. Bingo, truck is level again. :thumb: You can load his body on the level road surface, or with the front driver's tyre in the ditch where you came to a stop, the system will react the same. :mrgreen:

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allyv8

· #3 · Dec 12, 2009

Careful what you say,none of my bikes have lights...... (And I am aware I could lose a pound here and there.)

waveydavey

Discussion Starter · #4 · Dec 12, 2009

Carl
I get that and understand it but my question is if you decide to park on top of said motorcyclist; bike under one wheel and rider under the other.

To maintain the frame (Chassis) to suspension gap the car will be lopsided but it isn't it self levels to level so why?

kmagnuss

· #5 · Dec 12, 2009

It doesn't self level. You are mistaken.

RRToadHall

· #6 · Dec 12, 2009

waveydavey said:
To maintain the frame (Chassis) to suspension gap the car will be lopsided but it isn't it self levels to level so why?

:think: It isn't so it doesn't.

rtkraken

· #7 · Dec 12, 2009

It has four sensors that read at four positions, close to each wheel, the distance from the axle to the frame. It compares these readings to set values and adds/bleeds air from each airbag to achieve this set value. How it knows to ignore a rock (or biker) under the tire when at rest is a little beyond my understanding, but don't think of it as leveling, think of it as chasing a set measurement of heights from the axles to the frame. When you change height (ie offroad, standard, highway, embark) you're just selecting a new set of pre-programmed measurements for the sensors to chase. ("chase" being the key word here :roll: )

Scotty

· #8 · Dec 12, 2009

I want to here more about the Biker, what happened to the biker? Did you drop him in a hole or off a boat dock?

Scotty :lol:

kmagnuss

· #9 · Dec 12, 2009

The only way to keep a secret between 3 friends is to kill 2 of them.

Scotty

· #10 · Dec 13, 2009

Here, Here ... 8)

Scotty

shupack

· #11 · Dec 13, 2009

it doesn't find "level", it finds the closest approximation. with the RF wheel up on the biker, the LF wheel will be closer to the body, and the rear axle will be oposite (axle articulation). The ECU takes the average of the 2 readings to approximate where the center of the axle is, and ensure it's far enough away from the frame "on average". If there is more than a certain amount (10%? not sure of the value) it won't adjust, because it would need to re-adjust when it's back on flat ground. The ECU does lots of trigenometry, and can even find a pretty good level with only 3 sensors working.

waveydavey

Discussion Starter · #12 · Dec 13, 2009

Cheers Dennis-that starts to make sense at that. So basically when stopped it adjusts the corners to get the centers to the average of the corners.

For those that didn't follow the question park one wheel on the said biker (a rock or kerb will substitute) put in park (or neutral) apply handbrake and take you feet of the pedals with the engine running and watch what the car does.

RRToadHall

· #13 · Dec 13, 2009

Appky hand brake?

kmagnuss

· #14 · Dec 13, 2009

rrtoadhall said:
Apply hand brake?

Yeah, I was thinking the same thing. I always thought the hand brake inhibited the EAS, just like the regular brakes do.

For an expirement, I'm going to go out and jack up a wheel with the car on and in park to see what happens.

kmagnuss

· #15 · Dec 13, 2009

Okay, I did a small, not very scientific test.

I have a ditch in my front yard, so I drove one wheel up onto the ditch, simulating a run over biker.

With the EAS in normal mode, I drove up on the ditch and put it in park. No adjustments were made by the EAS up or down in any corner.
I raised it to high mode, and it went up the 2 inches or whatever, but it was uniform across all four corners.
Then I lowered it into access mode and it pretty much freaked out. I think it was trying to get down to where it's supposed to be, but it couldn't due to the necessary articulation. It just kept searching for the right height and moving around. I let it do that dance for about 30 seconds and decided I didn't want to take it out of a soft fault today, so I opened the door and let it pump back up.
Then I put it into highway mode. It rose back up and kept basically the same position as the normal mode, but 1" lower.
Last stop, back into normal. It rose up the inch in the same position as I started in. I backed out onto the level road with my foot on the brake the whole time...and when I put it into park and released the brake it didn't make any sort of adjustment.

My conclusion...anything with abnormal articulation will not allow the EAS to adjust the car to "level". We don't have any sort of mercury switches or bubble levels.

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