hi guys i was chatting to chris about this and he suggested to make a new thread for everyones benefit. i was just wondering why you would fit one of these front mounts over a poly front mount? from what ive read, it seems theres less nvh but thats about it. thanks.
In addition to my replies in the now GB thread: The standard & poly `cup` mount allows an engine to move significantly - I do not want this movement because it affects other components.
Have you NOT read the links I sent you??? http://www.clubgti.com/forum/showthread.php?t=187861 http://www.clubgti.com/forum/showpost.php?p=2028290&postcount=132&highlight=utimately disintegrates That carries an implied insult Please ask specific questions, based on the information you already have been given
sorry chris i did read them but thats all i could pick out. oh and also a poly front will cause stress fracture on the body, and it has a better location (in what way?). james then goes on to say the standard and poly allow the engine to move about significantly. from reading what others have said i thought the poly totally eliminated movement? ive read so much im getting confused. i just want it made clear how this mount is better than a poly and why. im considering participating in the group buy as it sounds like it is the best mount but i want to know the theory behind it before i commit to anything. sorry if i sound a bit dense but im not an engineer, i just love to drive and want to make the most of my car thank you.
The standard design mount with a rubber `nose` and the same with a poly `nose` allow the engine to move as the nose locates into a socket. The GB world cup type bush has no socket, it is a direct connection to the front panel through a rubber bush ... this provides a more fixed location. You also need to consider how the other (4) engine / gearbox mounts are provided as the engine will vibrate and this will need to be accounted for somewhere. That is why I have used the world cup type bush mount for the rear gearbox mount and left the other mounts standard. If you have a standard car then just keep the standard items albeit in good condition. Hope this helps ...
There are several other aspects to the engine mount issue which are relevant here. 1) Setting off traction Uprated front and rear mounts improve tracton immensely. Why? No engine bobbing backwards and forwards under load, causing erratic transmission of power to the road. This then gives increased and more predictable throttle response, eg if traction is broken, lift to regain and press more gently, all done straight away, because the engine is static: it doesn't need to come to rest. I used to use Bugpack rear mounts and ignore the rear mount NVH issue (which is significant) simply to gain this benefit, on a road car. The front mount alone will help (and have less NVH), but the rear mount is needed to optimise 2) In-use traction Again, as above, noticeable mid corner, when gaining traction to exit. As nice to use on the roads and the track alike. 3) Exhaust life Front and rear mounts improve downpipe life immeasurably 4) NVH of rear mount Solid block of poly, or rubber bobbin mounts in a high shore rubber? Both will increase NVH. The advantage of a less crude bobbin (or other mount )design should be evident, but clearly a block of poly is cheaper. 5) Life of poly rear mounts These are great to start with, barring NVH, but they in time soften, possibly from heat, but obviously articulation. They will ultimately rip out of the centre bolt, and do it when you've just launched the car, ie at the least helpful moment. The exhaust will have suffered on the way to fatigue and continued use will fatigue it some more, and if you're unlucky, snap it. This is where the rubber bobbin mount has a clear advantage. Hope that gives a far greater depth of understanding of what otherwise seems a more solid way of bolting an engine in for ? query what purpose. In a nutshell, traction, NVH trade off and you ultimately get what you pay for Side mounts are a potential next topic, but this covers phase 1 of any mount upgrade on a Mk1.
On my Jetta, i fitted a big red poly rear block and a poly front 'doughnut', and kept the standard side mounts. This helped a lot with some of the movement as i was having problems with the exhaust moving and constantly leaking, but i found over time that there was still movement in the front mount, mainly front to back rather than side to side or up and down. The side mounts were also past their best. My plan is to fit one of these uprated front mounts, stick with the rear poly block, and i've got a couple of NOS diesel side bushes to fit which are of a more solid construction to the standard items. I'm also fitting a cable change box, and also have one of the extra gearbox mounts from a MK4-chassis car, and will look at ways of also incorporating that if possible. The car's main use was on track and also the quarter mile, but it was fine on the road and covered thousands of miles including a trip to MIVW and it was by no means horrendous - removing sound deadening etc caused more issues than changing mounts in respect of loss of refinement and increase in noise and vibration.
