W12 motor mount heads up/inspection experience
01-25-2012, 09:42 AM
#11
AudiWorld Super User
Thread Starter
You are apparently mostly right..."Torque Support Bracket"
I've checked your pictures and my ETKA and I think you are looking at third engine support, one that doesn't carry engine weight and has not oil in it. Main engine mounts are further back. This one is there to counter torques from front wheel drive and drive shaft. It is not that expensive.
I did find a discussion in Bentley, in a subsection describing removing the "torque support bracket." Hmmm, sounds like an apt name if it broke supporting W12 torque... From the illustrations (though none with a great "big picture" orientation of the side motor area), it looks like the part in question. Repair procedure involves pulling the bumper cover to get access (ouch), plus the air box and right headlight, and then some Dremel/Helix drill work to punch a 24mm (a full inch!) hole into something (apparently for tool (socket?) access?). Sounds like a bit of a design goof where someone spec'ing the part forgot about later maintenance as positioned in the car. Reminds me a bit of Mister Bally's demo saw reference for a rear W12 sensor.
The description and illustration does show an electrical connector right at this part, and it's clear to me something brown in color pissed all over the alternator case right below it, so it adds up to me that it is in fact another fluid filled part that is also electrically controlled. If I follow the illustration (you can find it in Bentley in the W12/BSB Engine Mechanical section under the Torque Support Bracket subheading), it does look like it mounts to the car body/frame elements from above, so it would presumably be resisting torsional force in general from the drivetrain, rather than carrying dead weight to a large degree.
Heads up about an observed broken part that is an expensive/difficult fix in the W12 motor support components still applies, and the top level post has the pictures to show actual location. I will edit the first post to note the actual part.
Last edited by MP4.2+6.0; 01-25-2012 at 10:07 AM.
01-25-2012, 12:18 PM
#12
AudiWorld Super User
you choose the worst example of physics.
the engine is so big and powerful compared to the weight of the car that it barely moves before the car starts moving.
many times I/we had replaced completely broken mounts and the only complaint is vibration at idle, you can unbolt both engine mounts and the engine won't be jumping around in this car.
let me put it this way since you want to get too technical on a simple isolator.
if you install a 500-1000cc engine like a motorcycle or small car engine, it will need to be "tie down" all the way around not just at the bottom,
in the case of a small engine on a heavy car like this, the engine is trying to spin around before the car starts moving, simple power to weight ratio difference.
designing a mount based on all the factors you stated is important but not critical for the simple fact that the car can be sold in a very hot climate or a very cold one, you have to consider both scenarios and go somewhere in the middle.
but on a 6 liter engine you can just wedge the soles of your old shoes between the engine and subframe and be fine driving it.
the engine is so big and powerful compared to the weight of the car that it barely moves before the car starts moving.
many times I/we had replaced completely broken mounts and the only complaint is vibration at idle, you can unbolt both engine mounts and the engine won't be jumping around in this car.
let me put it this way since you want to get too technical on a simple isolator.
if you install a 500-1000cc engine like a motorcycle or small car engine, it will need to be "tie down" all the way around not just at the bottom,
in the case of a small engine on a heavy car like this, the engine is trying to spin around before the car starts moving, simple power to weight ratio difference.
designing a mount based on all the factors you stated is important but not critical for the simple fact that the car can be sold in a very hot climate or a very cold one, you have to consider both scenarios and go somewhere in the middle.
but on a 6 liter engine you can just wedge the soles of your old shoes between the engine and subframe and be fine driving it.
Now you add rear wheel drive shaft torque: 428 x 4.171 / 2 = 892 lbft divided by 1.5 ft distance from left to right support = 595 lbs lifting left and pressing right support. Once more enough to lift engine from left support.
There is not best or worst physics.
01-25-2012, 12:33 PM
#13
AudiWorld Super User
Thread Starter
Found the right parts diagram
Stumbled on this just now (looking for oil drain seal rings). Part #6 apparently. Good clear diagram. List $275. http://audiusaparts.com/parts/2007/A...iagram=1361208
Mishar as an FYI since we both use this. I mentioned to Loree that at least for W12's, the 2006 engine parts diagrams for the motors currently go to 4.2 listings. I found meanwhile the 2007 ones seem to work right; I also noticed you went to 2005, which might also work (didn't check). Also finding on my older 4.2, the 2000 4.2 listings are sketchy, but the 2001 ones are more complete. Thus big picture, as long as I'm comfortable w/ inter year parts interchange, I'm finding jumping around in the years can turn up what I want. They are putting together good stuff here in general.
Mishar as an FYI since we both use this. I mentioned to Loree that at least for W12's, the 2006 engine parts diagrams for the motors currently go to 4.2 listings. I found meanwhile the 2007 ones seem to work right; I also noticed you went to 2005, which might also work (didn't check). Also finding on my older 4.2, the 2000 4.2 listings are sketchy, but the 2001 ones are more complete. Thus big picture, as long as I'm comfortable w/ inter year parts interchange, I'm finding jumping around in the years can turn up what I want. They are putting together good stuff here in general.
Last edited by MP4.2+6.0; 01-25-2012 at 12:36 PM.
01-25-2012, 12:34 PM
#14
insulators
you want to make a scientific equation on something so simple as pushing a car.
look at old jaguars with the 12 cylinder engine, the mounts were merely a piece of rubber attached to metal brackets, even when worn out the engines did not move at acceleration.
now look at the Benz 300se with the 126 chassis, the engine been a 3 liter was too small to pull the weight of that car.
on that particular car the mounts needed replacement every 35k miles.
on an A8 6 liter all that torque does not matter for the weight of the car, as I said before unless you step on the brakes and push the throttle you won't see the engine move.
bumps on the road hardly have any effect on the engine/transmission as the suspension dampens those forces before they get to the chassis.
look at old jaguars with the 12 cylinder engine, the mounts were merely a piece of rubber attached to metal brackets, even when worn out the engines did not move at acceleration.
now look at the Benz 300se with the 126 chassis, the engine been a 3 liter was too small to pull the weight of that car.
on that particular car the mounts needed replacement every 35k miles.
on an A8 6 liter all that torque does not matter for the weight of the car, as I said before unless you step on the brakes and push the throttle you won't see the engine move.
bumps on the road hardly have any effect on the engine/transmission as the suspension dampens those forces before they get to the chassis.
01-25-2012, 12:49 PM
#15
AudiWorld Super User
No. I am just trying to explain you how it works. Unfortunately it seems that physics is not your language. Only other way to see that you are wrong is to unbolt left engine mount put in in gear and step on it (no brake needed).
01-25-2012, 05:31 PM
#16
unbolt
no need to unbolt anything, I/WE see many cars with mounts broken in 2 pieces with no complaints other than vibration at idle.
on your equation you forgot about the torque converter.
on a stick shift car if you let go the clutch pedal too fast the weight of the car will react on the engine moving but not on a large ratio lower gears auto.
one big factor missing here is the height of the engine, on Cayennes the engine is very tall thus needing a reaction mount on the passenger side.
on the Q7 no need for this as the engine is shorter, even more there's no torque mount in the front like the A8.
on your equation you forgot about the torque converter.
on a stick shift car if you let go the clutch pedal too fast the weight of the car will react on the engine moving but not on a large ratio lower gears auto.
one big factor missing here is the height of the engine, on Cayennes the engine is very tall thus needing a reaction mount on the passenger side.
on the Q7 no need for this as the engine is shorter, even more there's no torque mount in the front like the A8.
01-25-2012, 06:36 PM
#17
AudiWorld Super User
I didn't forget torque converter. As a matter of fact just regular torque converter would make things even worst multiplying torque on wheels with its ratio. A8's torque converter has a lock that kicks in before engine reaches the highest torque.
Unbolting experiment necessary.
Unbolting experiment necessary.
01-25-2012, 07:18 PM
#18
converter
I didn't forget torque converter. As a matter of fact just regular torque converter would make things even worst multiplying torque on wheels with its ratio. A8's torque converter has a lock that kicks in before engine reaches the highest torque.
Unbolting experiment necessary.
Unbolting experiment necessary.
01-25-2012, 08:10 PM
#19
AudiWorld Super User
Sure. It locks up when ratio comes close to 1. Not sure about particular torque converter but it is somewhere around 1.1 and I think it happens before max engine torque. If I am wrong and it is not locked yet when engine reaches max torque it makes things even worst because torque converter would just increase torque to the wheels and reaction on supports with it.
01-25-2012, 08:34 PM
#20
lock
Sure. It locks up when ratio comes close to 1. Not sure about particular torque converter but it is somewhere around 1.1 and I think it happens before max engine torque. If I am wrong and it is not locked yet when engine reaches max torque it makes things even worst because torque converter would just increase torque to the wheels and reaction on supports with it.
at that point torque has almost no effect on it.