Gearbox (and engine) mounts

[Kenneth]

Kieran, any update with this?

Tomorrow I will be picking up 450gm of flexane 80 liquid. Might see if I can get the front engine mount sorted before the meet on sunday.

Cost me approx $150 nz (approx £60). be interesting to see how far that will go. if It does more than 1 mount then it is probably worth it.

[KiwiTT]

What symptoms are apparent if your engine mounts are about to go ?

[Kenneth]

What symptoms are apparent if your engine mounts are about to go ?

dont know. my front one is torn. you can see the rubber centre has come away from the outer ring.

Probably the best thing to do is to talk to your mechanic and get him to take a look when you go for your services.

Of course I will report any differences I find, but there is a chance that anything I notice wont be the same as doing your engine mounts if all are intact.

[Kenneth]

Done.

I have successfully created a Urethane front engine mount.

I will post pics when I get them off my phone...

Results? Well, I was in a hurry to get the engine mount in before the Piha run on sunday, so things were a little rushed.

There is deffinatly more vibration in the car from the engine, the vibration is more audiable as as well. This means that I can feel what RPM I am at. On start up it feels a little harsh, but I suspect thats because there is bugger all engine movement. I am still yet to start the engine with the hood up just to see how much/little engine movement there is.

All in all, I prefer the feel of the engine as it is a lot more positive. If comfort and quiet is paramount to you, then this mod is not for you.

Oh, and the Urethane is actually quite expensive, $150. but I do have enough left to do another mount. you will get 2 mounts, possibly 3 out of 450grams

If anyone is wanting to do this, I still have a fair bit left. You will have to take out and strip your stock mount yourself though.

[zentac]

Ive got polyurethene mounts all round (4) in the FTO. They certainly help give better pickup, cant see any other point for them though...

[Kieran]

Ive got polyurethene mounts all round (4) in the FTO. They certainly help give better pickup, cant see any other point for them though...

Where did you get them from? Are they more harsh than standard?

[zentac]

Where did you get them from? Are they more harsh than standard?

alot harsher, the side ones I had custom made, I bought a bar of polly the side ones I got RPW to make up for me.

[Kieran]

To catch up with this one, as it's been some time.... What's a year between friends, eh?!

Okay. 3 engine mounts of the four are now sat with me here.

Unfortunately, I've broken my digicam so I can't post pictures But I should like to give a quick commentary anyway... One of the main reasons being that, it seems that the engine mounts are a little bit of a card tower - That is to say, if one mounting is dead or wearing out, the others have more loading to deal with and this is often at a more severe angle, so they are likely to fail prematurely, even if they're not worn out.

The three mounts I have in front of me are the front and rear mountings (the rear mounting sits next to the rear turbo and was designed by Satanka Evilishi at Mitsubishi, using the trademark Mitsubishi 'Impossi-Bolt' design) and the gearbox mounting (the big one under the airbox).

I think what's happened in my case is that the Transmission mounting failed first, judging by the condition of the bushing - it's much worse than the others. With this mounting, the body is bolted to the gearbox and eyelet (in the middle of the rubber) is anchored to the chassis. Over time it appears that the constant weight of the gearbox has compressed the rubber in the bushing, resulting in the eyelet moving upwards and exacerbating the problem. In fact, the rubber at the top of the mount has been put under so much compression that it has bulged out about 10mm each side above the eyelet and has also torn away from the top of the mounting body. This would account for the low-sitting gearbox

This then placed the front and rear mounts (which are bolted to the body and anchored to the gearbox near the engine at the front and rear) under stress, resulting in the front rubber tearing its bushing and collapsing downwards. The Rear mounting has followed suit, though as it's a beefier mounting, it hasn't completely failed.

I think part of the reason that these mounts have failed so badly is due to a number of things...

Age and Mileage.
'Launching' the car.
The fact that the engine is so torquey anyway.
Compromised design.... Each mount has a rubber bushing, but they're not completely solid. They have large air gaps by design, to allow the mount to move and flex, improving NVH levels in the cabin. The only problem is that this inherently lessens the amount of rubber available to spread any load placed upon the bushing - resulting in the load stress being focused in a few small areas of the mounting, rather than being evenly spread.

So. Tomorrow, starting with the rearmost bushing, I shall be making fresh ones using flexane. I shall follow the instructions here:

http://forums.evolutionm.net/showthread.php?t=166558

[wrdmotorsport]

good info K so soon be with your car then

[Kieran]

Right. Well, today I mostly set fire to to things and weilded a knife in anger!

Unfortunately I have no pictures again, so it's text only.

Anyway - The first mount I tackled was the Transmission one (under the airbox). The design of this mount is interesting in that the area that the bushing sits in is not completely round - as there's a fluid chamber built in that holds what looks a little like LHM fluid. As I was burning and wire brushing out the last of the rubber, this chamber periodically oozed more fluid out. THe reason why i mention this is because it makes the mount difficult to clean up - There's a lot of angles and crevices that you'll need to attack.

I've attached a mock-up diagram of the mount below. It's not at all accurate in terms of scale but it'll give you the idea. The grey areas are where the fluid chamber is. The black thing in the middle is the bushing eyelet. The square on top is part of the design. It looks like a bump-stop to stop total collapse of the mount if the rubber goes (as it had in my case).

The rear roll stopper was MUCH easier to prep - simply because there was no fluid chambers, so once the rubber was out, as wire brush cup on the end of a drill made short work of creating a shiny metal surface.

If you're thinking of doing this yourself, bear in mind it's time consuming and you'll loose use of your car for at least a weekend, taking the flexane curing time into account.

- Be careful of setting fire to the bushes. I did use a blowlamp once I'd cut out all the rubber I could, but you don't want to risk overheating the alloy shell and distorting it. Short, controlled blasts of flame are recommended.

- You can quite easily cut out the middle of the bushing using an old knife (make sure you don't want to use it again though as it gets covered in rubber ooze) ... Simply heat the blade using a blowlamp untill it's almost red hot and it'll plunge through the rubber like it's butter - much cleaner!

- I don't think you need (or indeed should) to chisel out the inner shell of the bushing as the thread I linked to in my last post shows... I found it just as easy to burn/brush clean the inner shell.

- You'll need Flexane FL-10 primer as well as a tin of flexane. This allows the flexane to bond to the metal properly.


Okay - time to go and pour my new mounts then! I shall report back in due course.

[Kieran]

New mounts poured and now curing. Flexane is easy to mix but very messy to work with, and if you've not got a good seal, it will find ways through!

Only slight worry is that the weight of the flexane has dragged the eylet of one of the bushings out of place a tad... It's now protruding slightly more on one side than the other.... I guess it will be 'suck it and see' as to whether this will be a major problem or not.

I think next time I might experiment and cast a completely solid bushing, then drill a pilot hole and press-fit the eyelet in once it's cured, so that I can get it dead on target.... I dunno if this would work or not?

[bernmc]

I suppose you could coat the eyelet with a thin layer of flexane to 'glue' it into the drilled hole...?

Have you gone for the 80?

[Kieran]

No, I went for 60. The General opinion on the word wide wobbly web is that standard mounts are around 45-55 durometer, 'uprated' mounts from the likes of Spoon Sports (a honda tuner) being specified at 70 durometer on some US sites. Now that the mounts have set, I am kinda glad I didn't get the 80 or the 94 - they feel VERY solid indeed!

The acid test will come next weekend when I refit them to the car and see if my fillings loosen when I turn the key!

[psbarham]

well let me know how they go , they only thing stopping my sump dragging on the road is the fine collections of cats eyes under it

[Kieran]

Will do - looking at how rigid they are, I am already saving for the swear tin when I try to line 'em back up again! No lateral play could mean bringing my engine hoist into the fray to get them damn bolts back in again!

Oh, and 1 pot of flexane will do two mounts with a few mils left over - so if you're thinking of using it, you'll need two pots to do all 4 mounts.

[Kenneth]

Will do - looking at how rigid they are, I am already saving for the swear tin when I try to line 'em back up again! No lateral play could mean bringing my engine hoist into the fray to get them damn bolts back in again!

Oh, and 1 pot of flexane will do two mounts with a few mils left over - so if you're thinking of using it, you'll need two pots to do all 4 mounts.

Yeah, they are a bit of a bugger to get lined up if something is slightly out...
I also found that there is probably enough to do 2. you MAY be able to get 3 if you were a bit creative and didn't full them compleatly (I dont think you need to... maybe some voids would soften them somewhat). At 2 mounts per tin of flexane, the economy of making your own mounts is somewhat dubious.

[Kieran]

Not so in the UK.... No aftermarket mounts.... And you've seen the prices for a Mitsubishi set on the first page!

NZ is probably cheaper though.

[stuartturbo]

is the max temp of flex an issue 82degc

[Kieran]

I don't honestly know Stu... I guess we'll find out. THe rear engine mount is about 6 or so inches from the inlet nozzle of the rear turbo, so it's on the cool side I guess, but I might put a heat reflective shield around it now you mention it. I think that's the only one at risk though?

[VR4 MAD]

Will do - looking at how rigid they are, I am already saving for the swear tin when I try to line 'em back up again! No lateral play could mean bringing my engine hoist into the fray to get them damn bolts back in again!

Oh, and 1 pot of flexane will do two mounts with a few mils left over - so if you're thinking of using it, you'll need two pots to do all 4 mounts.

Something from another thread about engine mount rigidity that maybe of interest Kieran...........

I was really surprised just how much movement was present. A friend of mine pointed it out to me and i was really shocked.

When we put the engine it it was a bugger as there was/is NO give in the mounts. Normally the rubber has an abount of give in it and even if the engine isnt perfectly aligned you can get thee bolts through the mounts. On the GTO with the solid poly mounts it took us hours of levering, hoisting and pulling to get it smack on so we could get the bolts in. When the engine was in the bay there was and still is NO movement in it. You need a big lever bar braced off the chassis to get anny discernable movement at all.

On drag launches though, yep the rear of the intake tube smacks the lid off the clutch master cylinder! It will do it every time on a hard launch so i now have to tape the cap on!!

Makes you think, but this movement was from heavy drag type launches though.

Anyway here's thread the quote came from....... http://www.clubvr4.com/forum/showthr...549#post213549

Hope that helps.