mishar

That's exactly what I said. When engine and transmission are at same speed torque converter ratio is 1.

s4master1

at that point the torque converter ratio is neutral, is just another heavy piece of metal wedge between the engine and transmission, has no reduction or increase whatsoever.
also at that point the torque of the engine is out of the picture, horsepower takes charge.
another example of mounts is the TT/GOLF/BEETLE the engine hangs from the mounts and moves a lot, that is the reason they also have a pendulum mount to counter the movement created when pulling the car.
nothing to do with torque but the position of the mounts are way higher than the crankshaft, nothing else to it.

mishar

No such thing as neutral ratio. It is 1:1 or just 1.

Torque multiplied with rpm equals power. They are related that way and they are both "in picture" all the times.

Sorry, but I have to ask you, are you sure you know what torque is?

s4master1

Sorry, but I have to ask you, are you sure you know what torque is?[/QUOTE]

easier if you answer me this.
what gets a car moving from a standing still point and what keeps it moving once in motion?
torque in simple terms is the turning force applied on an object.
simple example is torque on the wheel bolts, if you don't hold the wheel with the brakes or the weight of the car and you use a 24 inch long wrench the wheel will spin= no resistance, if you use a 2 inches long wrench it would get "heavier" needing more force/torque applied to it for it to spin.
but back to the original subject, on a 6 liter engine pulling the weight of the A8 the torque is so great that the engine don't move even if you unbolt it.
agree with your point in general but not in this particular car.
look at an 18 wheeler fully loaded, to get it moving even the entire cabin moves as the weight the engine is pulling is so great, you don't see the cabin moving when is in motion already.

mishar

Good, we are almost there. You know what the torque is. Only thing you are refusing is to calculate it. If you take 1 ft long wrench, put it horizontally on some bolt and step on its end with 200 lbs (for example) you will get 200 lbft torque. If the wrench is 3 ft long torque will be 600 lbft. And you are right, you need some counter torque or that bolt will just turn and you can't make any torque.

Same thing is with engine/transaxle block. On Quattro there are three torques coming out from it. One on propeller shaft to the rear differential and two to front wheel drive shafts. They are all countered by engine/transmission supports. But you already know all this. Only thing you refuse to comprehend is a size of those torques, or forces on the supports. Engine is not nearly heavy enough to counter them. Especially those on front wheels as they are ~3 times greater than that on the propeller shaft. Rough calculation from previous posts shows it.

My whole idea with this was to vaguely show complexity of designing cars not to tech anybody, but if there is any interest that is OK too. I am always willing to learn something and I've already learned a number of things from you. Your on hand experience is very valuable. Not so sure about theory, when you get in that field.

Edd W

Have you not missed factoring in the mass of the vehicle into the calc for the maximum force which the mount has to withstand?
I would also add that the 4.2tdi has some 12% more torque available at 1/3 of the engine speed so the calc for that wwould come up with a far higher force I would think - not sure if it has the same mounts though?

Edd W

Yes, but the electrical mount works using the very fluid which has escaped, rendering that effect null!

Edd W

I would suggest your theory is so far from correct that wrong is simply not in the same ball park.

The force to turn exerted upon the engine and transmission assembly is roughly half the resultant torque acheived at the output flange on the rear of the gearbox. The reason it is half is simply because half of the torque is directed to the front wheels which causes a lifting force on the engine as it tries to rotate backwards around the front driveshafts.

This force is pure and simple mechanics, working out what it is as Mishar said, a fairly simple equation, adding up all the forces involved.

Edd W

As it happens the XJ6 & XJ12's had a complex series of rubber and spring mounts - these were designed to counter torque from the propshaft. Even then, the engine moounts were, from what I remember, a V shaped clasp design which failed regularly, as a result of the torque forces exerted upon them. If their only job was to support and isolate the engine, they would never have failed!

Mister Bally

It looks like we have one advanced mechanical engineer, and a technician or two battling it out on who gets to have the last word in.

I've tried to keep out of it but it's getting tough. May I suggest listening to the one with the degree.