Reproducing the Stock 914/6 Engine Mount, and comparison to alternatives Options

[worn]

Cool pics, Luke. Thanks for sharing. (IMG:style_emoticons/default/thumb3d.gif)

911 mounts are spread wide apart because the rear body panel sheet metal was not designed for that kind of weight.

Interesting idea. Makes a lot of sense. The mounts would need to be out to the sides. That cross-member under the 911 engine lid latch isn't strong at all.

I don't think a single 911 mount is sufficient.

I'll have to do some research on this. I'm actually thinking about using a 996 engine mount in my personal car. These are modern fluid filled hydraulic mounts. Probably going to grab one off eBay for trial fitting.
(IMG:http://www.914world.com/bbs2/uploads_offsite/www.sierramadrecollection.com-419-1368123838.1.jpg)

OK maybe you are better at the mental gym than I am, but I have a hard time determining whether a lot of torque actually gets passed to the engine mount. My idea is that the bell housing handles a torque argument between the crank and the diff and the torque ends up mostly squatting the rear and lifting the nose. In real terms are we dealing with more weight or twist? My guess is weight.

[Mark Henry]

You rev a torque monster real fast with a load on it you can bet that engine is trying to twist out of it's mounts. Look at trucks that do tractor pulls, they back up the mount with a hefty chunk of chain just in case.

[McMark]

But Mark, as was mentioned by some else earlier, isn't most of the 'american muscle' chassis twist because of the long driveline and the fact the the source of the torque is so far away from the recipient of the torque? I'm off to YouTube in search of high HP 911 engines revving. We'll see if the motor moves... (IMG:style_emoticons/default/idea.gif)

[McMark]

I think this is a perfect video. Solid/stable camera mount, accelerating under load, and you can't see a bit of engine twist. Even stock 911 mounts have some give. BTW, this is 303hp.


https://www.youtube.com/watch?v=wySSMKNsC6M

[McMark]

This one shows some engine twist, but it's not like those tractor pull trucks you're talking about where the whole chassis twists. And this is a 3.6 Turbo.


https://www.youtube.com/watch?v=cYmlhLjeLOE

[McMark]

Engines that use block mounted transaxles don't have the torque windup that a vehicle would have with a conventional driveshaft. Even ones with torque tubes dont have that much engine lift compared to a good old muscle car. Torque is still present but its transfered differently where huge mounts with large footprints are not required.

I agree with this more and more as I think about it.

[Mike Bellis]

I twisted the chassis of my first 914 V8 drag racing in front of the police station. Front left wheel came off the ground. The engine cradle transferred all the torque into the chassis...

BTW, I won (IMG:style_emoticons/default/biggrin.gif)

[Mark Henry]

I can kind of see where you are going with this (IMG:style_emoticons/default/smile.gif)

The one thing that the mount must do is limit engine movement, mainly for the shifter rod.

I do know from my bug experience that I would try to make the mounts as stiff as possible, without transferring extra noise. In the bugs it's not so much twist, the engine actually tries to hop up and down. In bugs this is a main cause of wheel hop and will literally bend the the frame yoke.
I would make a bar so I had two 914/4 mounts at the front (nose) of the trans, as the stock single mount was not good enough for a HP application. I would keep the rubber (real VW HD) trans mounts at the bellhousing and I would add a crossbar with a pad on the tail of the engine or I would build a kafercup style mount.
My 901 and type 4 in bug set up has a crossbar with 914/4 mounts at the front, stock bug mounts at the bell houseing and I will be fabing a rear bar to use the stock 914/4 mounts.

Might be a month or more but I'm going to be fabing up my own mount soon. I was thinking of fabing an RJ style mount as I have blueprints and parts templates that were given to me. Also was thinking about a Patrick style, but I don't like the fact it has no backup to a (however unlikely) a bolt failure.

Maybe I should dig out that dummy engine and stick it and a tranny in there and start thinking as well. MrHyde is dropping off my DW tank this weekend.... maybe I'll get the itch and stick something in there sooner.

Mark any ideas you may have you would be welcome to bounce them off me, other than making my own mount I have no interest in becoming a mount retailer. (IMG:style_emoticons/default/smile.gif)

[McMark]

I twisted the chassis of my first 914 V8 drag racing in front of the police station. Front left wheel came off the ground. The engine cradle transferred all the torque into the chassis...

BTW, I won (IMG:style_emoticons/default/biggrin.gif)

Wait, was it an open diff in your transmission?

[McMark]

Despite the nay-sayers, I'm moving forward with this project. Finished the drawings for the chassis section and made a template. I tried to fit a stock 996 motor mount and they're just too big. So I'll be making an adapter to utilize a 911 sport mount, which means it could also use a Wevo mount to reduce flex. The pieces will be made from thicker steel than the factory mount to increase rigidity, probably 1/8" plate.

[0396]

Despite the nay-sayers, I'm moving forward with this project. Finished the drawings for the chassis section and made a template. I tried to fit a stock 996 motor mount and they're just too big. So I'll be making an adapter to utilize a 911 sport mount, which means it could also use a Wevo mount to reduce flex. The pieces will be made from thicker steel than the factory mount to increase rigidity, probably 1/8" plate.

Mark,

Looooooks very interesting. When your done, I'm interested in a unit. Pm me when done.

Oh I like add that I have an OEM engine one...,so if you can adapt the one your making to hook up with oem engine mount- the better

Thanks (IMG:style_emoticons/default/piratenanner.gif)

[messix]

in the 914-4 power train mounts you have a 3 point design, the wide spaced points at the tranny and at the front the single mount at the engine bar.

with the 914-6 besides hanging more weight from the front mount the is no difference in the stress on the chassis.

front engine/tranny config with a live axle uses the same 3-point mounting and they do have torsional twisting of the chassis because the drive shaft is transferring torque to a lever [the rear solid axle] that is acting against the ground on one end and the engine/tranny mounts on the other, and this force is causing the chassis to "twist".

the forces that a engine/transaxle transmit to the chassis are a axial rotation [in relation to the transaxle outputs] on the fore/after axis of the chassis [engine will try to lift the chassis at the front of the engine under acceleration and pull it down under braking. because it is now the wheels that are acting against the ground in torsional force.

the key to this is that the engine and transaxle are a solid unit and the side to side torque force is nulled as the torque is transferred to the halfshaft outputs.

[rick 918-S]

I run solid mounts in the Alien. Rubber mounts are designed for family cars and the critics from the magazines that want performance from their Lazyboy Recliner. I have no noticeable engine vibration and when I hit the loud peddle the front of the car lifts. Because of the half shaft arrangement the car stays flat and level during lift off. Twist is not part of the equation or a limited part. And torque is abundant with over 350 hp.

Mark, your mount pattern is very nice. (IMG:style_emoticons/default/welder.gif)

[ConeDodger]

Mark already knows this because we had this conversation 1:1, I had a conversation with Jim Patrick about mounts. He asked what I was using and I told him vaguely, that we were reproducing a beefed up factory six mount. His concern was that because of the geometry of the narrow triangle formed by the front mount and the transaxle mounts, the engine / transaxle unit twists and "can cause shifting problems."

One has to remember that Jim Patrick puts food on the table selling engine mounts. That isn't a criticism. In any research you must identify possible bias.

Best I can tell from what I've read, the mount isn't the area that should be the focus for the solution to the shifting problem. Cable shifter? (IMG:style_emoticons/default/evilgrin.gif)

[SLITS]

One of the 'spurts explain to me that if there is no torsional twist with the 914 set up, why do you hear a thump when you have a broken drivers' side mount on the later cars?

[messix]

The only mount I have seen broke was the little rubber front one from hard launches from a standing start....

[McMark]

Well there's one way to definitively solve this armchair-engineering debate. (IMG:style_emoticons/default/happy11.gif)

As for my addition to the speculation, I figure if the factory race cars (908 engine for example) used a single center mount and if the boxsters use a single center mount, I can't see it being a problem.

[SirAndy]

I figure if the factory race cars (908 engine for example) used a single center mount and if the boxsters use a single center mount, I can't see it being a problem.

Porsche also used a dampener (basically a gas-shock) from the engine to the chassis.
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[McMark]

I figure if the factory race cars (908 engine for example) used a single center mount and if the boxsters use a single center mount, I can't see it being a problem.

Porsche also used a dampener (basically a gas-shock) from the engine to the chassis.
(IMG:style_emoticons/default/shades.gif)

Any idea where this would mount (on the 908)? I looked through a bunch of pictures (including these) and can't see any brace nor any location that would support a torsional brace. (IMG:style_emoticons/default/confused24.gif)

I would love to see how this was done on any of the center mount Porsche race engines.

[Elliot Cannon]

The yellow zonker had a narrow mount and seemed to work OK. Kind of hard to see in this pic.