ALFAGTV6.COM

[Mats]

My point was that if you align everything perfectly in the garage it will move itself out of alignment once you add torque. The shaft needs to be straight when diving, that's the whole problem.

Poly is useless in situations like this, hysteresis and natural damping is bad and it can't take the same beating as natural rubber. Will wear out very quickly.

[Zamani]

Mats, when torque is applied won't the engine twist on the same axis the shaft is turning?

[ar4me]

My point was that if you align everything perfectly in the garage it will move itself out of alignment once you add torque. The shaft needs to be straight when diving, that's the whole problem.

I understand that. I'm trying to do as much as possible given practical constraints. I was not sure if your mentioning of solid mounts was hypothetical (to make a point) or a suggestion for practice. I suppose it was the former.
Jes

[kevin]

MD, I agree with you that the best prop solution would be with only one rubber coupling(BMW) and that would be at the front so handle the offset alignment on the GTV 6 and mainly to absorb that shock. Some chaps here use nearly solid mounts and engine stays on the 2.0l as they can feel the engine move in the twisty sections which upsets the balance of the car. I dont think you can put an engine stay on the V6 as this will defeat the object of offset engine mounts.
I got some pics of the prop complete in Rouse car. Im sure they are up somewhere.
Im hoping mats will redesign the whole prop, front and rear mounts with a lightweight solution and say 'i told you so', however this will probably only apply to the 2.0l's.
jes, I made one(front alu coupling) similiar to that but got no need for it yet with coupling cage been succesful.

[MD]

Kevin/Jes,

Here's my modified front engine mounts. Both left and right are the same.The rubber bush is of a much higher density than the original Alfa compound. It is actually a Range Rover suspension component.

The point is this. The set up restricts engine rotation and does not require an engine restraining bar.This of course minimises changes in angularity under torque. Coupled with a similar modification to solid rubber mount for the rear engine mount, the net movement of the engine in either fore and aft mode or rotational mode is minimised.

This is in the race car application.

Strangely enough, the amount of harshness is a lot less than you would expect and it is really quite acceptable.

So getting to Mats point, when I set up the prop shaft for straight operation in the static mode, it will approximate the situation under operational mode and when coupled with any gyroscopic effects
when rotating, it does maintain correct angularity I believe.

[kevin]

MD, remember your car starts in a straight position unlike the gtv6 so you cant do it in the 6. If I recut my engine mounts and aligned straight then it would work.

[MD]

Kevin,

I didn't know that there was any specific inlcine in the V6 engine not that it matters as these are hand made mounts and you should be able to fabricate any angle you need.

Just had another simple realiasation.Whenever I have had a prop shaft that was balanced with the car stationary but revving the engine through the range, it never produced a vibration. Nor did it produce a vibration under load when the car was in motion. I am assuming zero anlge changes as engine revs change due to almost no load when it is stationary.

Conversely, a car with an out of balance prop shaft at staionary position only got worse under load and seriuosly whacked around 3400 rpm.

That suggest to me that the misalignment thing under torque is possibly not as relevant as first it appears and lining the prop shaft up in the straight position should be ok in the absence of evidence to the contrary.

Of course this is just an explanation about a balancing issue as in those cases, i never checked the angularities so I cannot say for certain..

[Zamani]

When the engine is revved does the engine go into misalignment i.e. left to right OR does it tilt in the direction of the crank's rotation (on the same axis)?

One Alfa tuner told me, for all practical purposes just align it under static conditions. Aligning it in under load is sort of an academic discussion for most of us. For me at least, I agree as I know for sure I'll never be able to do it.

Anyway MD, did you just align it using the spacer method or did you also try mounting a laser pointer on a used cut up yoke?

Allen Mitchel also had to realign his engine and gearbox when he converted to the CF setup. I think it cost him US$1.5K, which is not too bad.

[MD]

When the engine is revved does the engine go into misalignment i.e. left to right OR does it tilt in the direction of the crank's rotation (on the same axis)?

Mr. Zee. The engine rotates in the opposite direction to crankshaft rotation and is called a torque reaction.

No laser used. I did however have to cut the outer corners off the tranny rubber mounts so I could get the transaxle high enough without the mounts fouling the tunnel !!

[Mats]

There is also a straightening force produced in the Hardy/Guibo as well, not a small one either.

It's important to note in this discussion that we are talking about very small angular changes in most driving conditions, nowhere near a pendulum suspended transverse engine for example so to do it up straight statically will be a lot better then to just drop the engine in and hope for the best.

I'm however convinced that unless there is something seriously out of alignment you will only affect the durability of the hardys, the vibrations are from propshaft imbalance and that is something completely different.

[Zamani]

Hey MD,

You are right about the direction. On the V6, I think it is slightly off left to right, kind of like how Maurizio drew it earlier. Not sure about the Nord. Am I right on this?

And I think it's worst if you have the older type propshaft wihtout the sliding splined front section (flywheel side). Because you can't quite adjust the length. I have that type of propshaft.

[ar4me]

Zamani,
It is probably a straight switch to use the spline-based driveshaft - you may need the entire driveshaft. Call APE - they probably have a used one. I was looking into that type of driveshaft due to the beefier center coupling but was told it only fits with shafts that do not have splines - needless to say I threw out that idea quickly.
Jes

[MD]

Zamani,

I am confused by you response which makes me think we are not in the same swimming pool.
Referring to Maurizio's illustration in the context of what I said would confirm this. When I am talking about torque reaction, I am saying this:-

Alfa engines rotate clockwise.When you engage first gear and crank up the herbs to 5g's, drop the clutch and see some smoke on the rear rubbers, the torque reaction will be counterclockwise and the engine will want to rip the lhs engine mount into two. Does that make more sense to you?

What I beleive YOU are talking about is a fore and aft motion under accelaration and deceleration which would loosely be represented by Maurizio's drawing. The two motions are at 90* to each other and definitely not the same. I hope that helps mate.

BTW. Totally agreee with Mats last and very relevant comment.

[Mats]

There is also some sideways motion, that's because the engine mounts are sitting on a lower plane then the crankso the torque around the crank turns into a force which moves the engine sideways. The main moints move more sideways then the rear and that means you need to put the engine in crooked to get it straight during hard acceleration.
V6 more so then the Nord because of the higher torque in the V6.

[Zamani]

Hi MD,

I was talking about the way the engine sits at rest. It seems to not be perfectly aligned. I'm not sure about the amount of misalignment during motion. Probably not a big issue for me, but I agree with Mats that you need to align it when the system is at rest.

I just checked Maurizio's sketch, I thought it was showing misalignment from left to right.