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Diesel Rear Motor Mount

10K views 55 replies 28 participants last post by  DrewP 
#1 ·
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#2 ·
very interesting.

Probably doesn't compare, but in the mk1 vw world, the diesel mounts are a lot more heavy duty than the gas engine mounts. The ones in my vw rabbit diesel were original and failed at 220k miles (turned soft and started to tear). I even re-used one, because it was still stiffer than the brand new gas engine mount I bought.
 
#3 ·
I just ordered it from GS on Wednesday. They said it is currently out of stock but should be in within a few days.

From those that have all three I have heard that tons more vibrations are transferred into the car... I don't foresee it bothering me that much...

According to the web page it is a direct bolt on. I'd imagine the only difference is maybe a thicker rubber and a heavier hydraulic oil.
 
#5 ·
I have a friend that put all three GS mounts in his 900s. I asked him about the diesel mount as i was wondering about it too. He said it was notably stiffer and worth the money for the upgrade. Just be aware that there is definently more cabin vibration. I got to drive it with the new mounts and it feels so crisp and fresh but it also makes it vibrate like a race car, which I personally like as your more in touch with the car, but many Saab owners probably won't like it.

Put simply, its without a doubt one of the next things im getting for my car.
 
#8 ·
Well I was eating rear mounts like tires at the drag strip.. The diesel rear mount has held up nicely.

My container from Sweden (Realcar, BSR and Sp for the bigger ones) will be here Monday.

Also in other news we won't be dealing with the SE company that held up this shipment for over a month ever again ;)
 
#13 ·
I have the two other mounts and the vibration is not to bad, to me at least.

I am wondering, how much EXTRA this last mount will add. My guess is, if I am fine with the two that I have now, this 3rd one will not be much worse.

I am probably going to add it to my parts list for the 2nd round of shopping for my trans rebuild this month.
 
#14 ·
I will make some sketches of how the side torque mount like the 9000s does not help the problem. it does a little but it makes other loads worse. Think about the reaction torque from the axles and how the stock 3 mounts are symmetrical. Then you throw one up putting lateral loads on the front mounts and causing the power-train to twist in the hole.
 
#15 ·
Hey Nick, I know this is one area we disagree on and I know what you are saying and on paper I am sure this looks less than the ideal place to put a third motor mount, but in real life there is no question it makes a huge difference in reward engine movement and the tranny and drive-train actually seem to stay much more in line and much more power is transfered to the ground.

I had mine checked on the dyno and it did not move more than 1" backward under full load with 500bhp. I also noticed when my clutch was slipping before with the old used one that when I put the top motor mount back in place, lo and behold, the clutch started slipping again, one more example of how more power is transfered to the wheels and the ground with the top mount.

Its not absolutely necessary, but there is some wasted energy there for sure and its very easy to test;)

John
 
#16 ·
I see what Nick is saying too. However unlike the 9k setup, there is a mount dead center in the ng900/og9-3 setup where as in the 9k it was two on the bottom front and rear of the motor on the subframe, the dogbone up top, and then the lone trans mount on the driver side subframe. That I'm sure deffinitely causes an unwanted twisting motion.

However in the ng900/og9-3 setup I'm sure that twisting motion is nowhere near as bad since its a triangulated setup. What if instead of mounting the dogbone/brace in the normal spot going from right behind cylinder 4 dead center back to the strut mount brace? That would keep it triangulated in 2 areas perfectly aligned.
 
#18 ·
That, could require some tough fabircation.

I agree that from all the car I've driven, seen, and watched run on the dyno the engine is noticeable more stable with the top mount from a 9k. I'd be interested to see what more information is out there to prove or deny this.
 
#20 ·
I will keep this short, little busy..

Every top mount I have seen was pointed down in the front. This will only add more load down on the rear mount and force forward on the front mounts. It needs to point up(on the engine side) to vector the force off of the rear mount. John, this is most likely why you were breaking the rear mounts.

I learned early on developing these mounts that it was important to keep the mounts symmetrical to eliminate torque pulling most noticeable on the highway.
Stock engine mounts only allow maybe 1degree rotational freedom of the powertrain. You are not loosing any energy. Otherwise if you were loosing power into the mounts then the mounts would be getting very hot. ;) Thats basic physics.
 
#21 ·
I guess we will have to agree to disagree on this one;)

No question more power is put to the ground with the top mount on the car and I actually broke rear mounts trying to run without it as you suggested and once I went back to it, clutch started slipping again, immediately, and I still have movement of a weak used rear motor mount, but have not broken one again.

I think if you tested with and without one, you would see and feel everything I am talking about. Even with both poly mounts up front and no top mount, my motor goes way back on full load and there definetely seems to be some wasted energy. Not that it matters much in our case of big power, but its still there none the less....

You could always make a strut bar mount like Kyankton did to put the load more in the middle of the engine.

John
 
#22 ·
Ok It is not opinion.. but physics.. :D

The clutch slips because of the shock load. You need a certain amount of "give" in the mounts to keep the shock load down on the gearbox and associated parts. This is a compromise with trying to prevent windup or "Wheel hop" This is not as simple as it sounds since everything from rear sprig rate to bushing harness to upright stiffness and tire side-walls have a influence on this frequency.

If we talk about wasted energy rotating the powertain on the "softer mounts".. Say the engine is accelerating at a measly 250rpm/s (Quite slow actually) And the engine is allowed to rotate maybe 5deg (that is an exageration bear with me) There are 2 axis of rotation depending on load. One is the crankshaft the other is the driveshafts.

250rpm/s = 90,000 degrees/second So those 5 degrees take a whopping .00005 seconds! That is at 4 seconds per 1000 rpm acceleration rate..
 
#23 ·
Hey, now you have said somthing that makes sense to me:cool:

Shock load would make a lot of sense and instead of rotating or twisting backward, the energy is immediately put to the wheels and this causes more tire spin and of course with a marginal clutch, clutch slippage.

I did notice I would spin the tires much easier with top mount and the shock factor would make some sense.

That would equate to more power to the ground and even though its a small amount, its there. I did stop breaking the passenger side stock motor mount when I went to the top mount and it does seem to keep the drive train in line better, but hey it does not mean my car is any faster for it being there.

I have found many times in life, what works on paper is not always what works in real life and urge you again to test with and without a top mount and then report on you're findings.

We don't have to agree on everything and that is what makes modding fun in my opinion, not everyone has to do everything exactly the same.

You like not running one and feel it puts an uneven load on the other mounts, I feel its a great mod to keep the motor from twisting backward so much and it does seem to get more power to the ground.

I like w/m injection and have been able to run very aggressive timing with it and keep my car a little safer from knock. You don't think its worth doing, its no big deal, we all have our own ideas on what works well and not so well and that is what makes a free country great! :cool:

I just had an idea, we can line up and drag race at the track and if I win, I will say its probably because of my top mount and w/m injection and if I loose you can say its probably because of that top mount and w/m injection:p

John
 
#29 ·
I made my torque damper sit level with the top of the engine. Makes for very crisp shifts, and since I'm running stock boost, I have very little fear of overloading the mounts. I would love to try uprated mounts with and with the damper to see ho wit works.



I hand lathed the damper body, installed an 80D poly cylinder in it, anchored a rod w/heim joint in the poly, and then bolted a heim joint to the outer body. The block bracket and firewall bracket with spreader and backing plate are all hand milled by me on a Bridgeport.
 
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