Engine Swap Forum

Kurt,

   Wow!  Those drawings look fantastic, I wish I had some of that software.  I've got a degree in graphic design so I'm pretty proficient with Corel, Illustrator, Photoshop, etc. but I've never tried the 3d modeling software.

  I really like the shear type mount as it would be the best for NVH as you said but I'd only vote for it if we can find a stock OEM lower section from some car that works right out of the box (I have access to tons of those to look at so I'll start looking). Also, like you said, header clearance is a real issue with the the shear mounts, that lower piece may be too big to clear the bottom of the stock Z/G header. If we have to fabricate the lower piece I'd just as soon keep it more simple and go with your last revision of the compression design and use something like the hockey puck (or maybe you've got a better/classier idea for that).

Good work!

Fred

My expectations are that we'll have to do some modifications to the lower section or fabricate one from scratch and use some kind of insert.Most engine mounts with a similar lower section that I've seen have 2 to 4 bolts that mount into the crossmember where my interpretation of the 240sx is that we need 1 bolt hole. (I don't have access to my car so can u clarify that please?). 

I don't think we'll need the NVH characteristics of the shear type (since the hockey puck isn't that bad) but maybe on startup it might prove to be a little more impressive. Another trick we could investigate is to reduce starter voltage on initial turn and bump it up after (x)seconds or 1 or 2 revolutions. Static friction is usually higher than dynamic friction and by using less torque to get the pistons moving, there would be a smaller reaction (engine movement) in overcoming the static friction. Once the pistons start moving (dynamic friction) then bump the voltage back up to get the req'd rpm for cranking.

Back on topic...

Can u check to see what the 350z/ G35 mount inserts are made from? Rubber/ Hydraulic/ Same as maxima (MR fluid?) I was thinking we could use those (and/or the pathfinder's) for the compression type. If somebody found an airbag of some kind that'd fit they could use that as well (I've seen those in use but can't remember where).

I'm about as sold on Comp type - rev2 as I was on the shear type yesterday... Gimme time... I'll prolly think of something that makes the shear type more intriguing.

Kurt

bettonracing:

My expectations are that we'll have to do some modifications to the lower section or fabricate one from scratch and use some kind of insert.Most engine mounts with a similar lower section that I've seen have 2 to 4 bolts that mount into the crossmember where my interpretation of the 240sx is that we need 1 bolt hole. (I don't have access to my car so can u clarify that please?). 

Yes, one bolt through the crossmember.

bettonracing:

Can u check to see what the 350z/ G35 mount inserts are made from? Rubber/ Hydraulic/ Same as maxima (MR fluid?) 

They are the hydraulic type, no electrical connection so I guess not MR fluid type.  I've seen them ripped in two and I seem to remember fluid inside, very common on late model cars I've noticed.

The compression type is most doable I think, all things considered, most simple to design and fabricate it looks like.  I really have no big problems with my mounts except I'd like them made a little beefier and better looking with possibly something other than the puck in there.

Wait, I have an idea if you could draw this out.  Picture in your mind my exact setup but with another puck on top of the bracket.  The bolt would go through the top puck then the bracket then the bottom puck then the crossmember.  I think that would be a compression mount but with some rebound dampening too.  You'd need a large washer or plate on top of the top puck to prevent the bolt from just ripping right down through the top puck.  Thoughts?

Fred

Here's my interpretation of what u're recommending.

Those inserts might be a little on the large side but I think it shows your idea. The only adjustment I'd make is to use a smaller (cheaper? easier to find?) insert on the top (rebound insert) since the jounce insert on the opposite side somewhat already absorbs some of the same motion (i.e. theoretically rotation about the crank axis). I'm thinking to use a fluid insert for jounce and a rubber insert for rebound. That being said, the symmetric look (as in the picture) does look kinda nice...

Does the 350z insert allow for a straight thru bolt as is required in our application? If not, any ideas on how to use the 350z insert? Or can u check your 'stash' to see if there're any OEM applications that accomodate that straight thru bolt, please.

Here's a shot of a stock Z mount with it's bracket:

Seems pretty tall given the height of the stock 240sx crossmember, I looked into using it originally but opted out probably because of it's height.

Most RWD mounts use the single bolt design from what I've seen.

Fred

A taller 'insert' will help reduce the size of the mount we're designing. More specifically shorter legs. Unfortunately, it might also interefere with the exhaust manifold...

Another possible problem I noted w/ the 350z insert is that it seems to sit more upright (i.e. vertical) in the 350z than it would in the 240sx (the result of different crossmember designs). If this is so, it might put a shearing force on the insert whereas it was designed to be loaded in pure compression (especially considering it is a fluid mount...).

Could u take a height measurement of the insert itself and see where that height falls in with your engine's current location?

If most rwd setups u know of are single bolt (I'm assuming u're referring to the through bolt setup like what we're using), we should be able to find a fluid filled insert that'll work. If u come across any, grab some quick dimensions and we'll start compiling a small list to use when we start throwing (accurate) dimensions into the design.  (This is assuming that u're in a agreement to using a fluid insert for the jounce side).

I'm still open for ideas on the shear type if u're still interested. Otherwise I'm focusing my efforts on the compression type rev 2b (2b = the rebound insert added).

I think you're right, the angle of the 240sx crossmember will put that Z mount at a bad angle, also it's height puts it really too close to the block to make a bracket feasible.  I don't think it's the best option for us.

I think most RWD mounts are like the Z's, they have a stud on top and one on bottom instead of an actual removable through bolt.

I like the compression design best, I vote for that over the shear design.

By "jounce" do you mean when the engine lifts up?  I have no prob with fluid filled for that.

Fred

Ok. So I guess we'll focus on the compression type mount.

My reference to jounce refers to the mount insert below the bracket (in the location your hockey puck is currently). (note: jounce/ rebound are opposing terms used in suspension circles to describe wheel motion over bumps and in dips. Rebound actually refers to the downward motion when a wheel goes into a hole. Jounce is the upward motion resulting from driving over a bump).

Since u called the upper insert 'rebound' I kinda just took that and ran w/ it. I'll call them upper and lower inserts from now on.

For clarity, I'd like to use a hydraulic lower insert and a rubber/polymer upper insert. The hydraulic lower insert on the opposite side will help absorb the motion the upper insert is intended to absorb.

Once we find our hydraulic inserts, we'll be ready to start putting in [accurate] dimensions and run some FEA tests. I'm gonna need some rough engine dimensions so expect some pm's. I'll put sketches (including the dimensions discussed in pm's) with the FEA files.

Kurt

Kurt,

  Sounds good, I think we're heading in the right direction.  I wonder how hard it will be to find hydraulic inserts with provisions for a through bolt?  I don't even know where to start looking for that kind of thing. 

  Also, I wonder out loud, is the upper insert really necessary?  It was an idea but not necessarily a good one.  I wonder if the compression of the RH mount when the motor rocks to the RH negates the need for the upper insert on the LH and vice versa?  I'd think the more vibration dampning the better but it may not make a noticable difference really, especially if we come up with a suitable hydraulic lower insert, that alone is gonna absorb a ton of vibration over my already "not too bad" solid pucks.  I think a hydraulic lower insert will be sufficient.

Fred

I don't expect the hydraulic mount to have a through bolt, I'd expect it to have two concentric studs (one attached to the top of the insert, the other attached to the bottom w/ the fluid inbetween) which simulates a thru bolt setup. If u come up with any, note the angle of its mounting surface. I'll keep my eyes open too. (check some german cars if u have any).

If we find a hydraulic lower insert that does not have a thru bolt but the concentric studs setup, we won't need the upper insert. If it does infact have a thru bolt, then I think the upper insert however small) might help with absorb the initial motion (like on startup/ bumps/ etc). It doesn't have to be anything fancy but even a [thick] washer-shaped rubber insert would help. I'll go bug some parts store ppl this weekend and see what I can come up with. The upper insert can be optional.

Kurt

It's funny how I keep ending up back at this guys site: http://e30m3performance.com/installs/installs-2/motor_mounts/mounts1.htm

Note: reference to the s14 engine on that site refers to the 2.2L & 2.5L bmw 4 cylinder engine from the E30 M3 (first gen M3 w/ the buff fenders).

Based on that article, it seems we have a couple options from the bmw group. The E30 M3 and the 740iL (the E28 is not fluid filled). My first preference would be the 740iL ('93 & '94) since they're the shorter of the 2 (more header clearance). Quick online price checks = ~ $50. I'll keep checking around...

I started to get a little worried about the mounting angle that the subframe subjects us to but after looking at your pictures:

 and

I don't think the angularity will be as much of a problem as I'm making it to be. Can u get a rough estimate of the subframe mounting surface angle (from vertical)?

Kurt

Kurt,

   The crossmember mounting pads are around a 45 degree angle, but not exactly.  I measured them w/ an angle guage but I've forgotten the exact measurement.  I had the mount brackets bent to 45 degrees and it worked out okay but not exactly ideal.

   Those 740 mounts look pretty good but maybe still too tall, not sure.

Fred

Here's another option from an 02 Corvette that looks promising.

I believe it's fluid filled.  The measurements don't include the length of the studs as that shouldn't be a real issue.

Fred

Those corvette mounts seem to be right up our alley. I'm still hoping (looking) that we can find one even shorter but seriously doubt it'll be drastically shorter. Keep looking to see what u can find (as will I).

Since I don't expect to find any mounts much shorter, I think we should start putting in some dimensions (using the corvette mounts). If (in our never ending search for better equipment) we find a shorter mount (which won't be much shorter), it won't require drastic changes to the mounts to get them to work. I'd expect a shorter mount to require shims of  some kind to work. If needs be, we could redesign some new 'legs'.

Start thinking of any cosmetic changes u would want to add.

Fred, this'll be your area of expertise. I'm gonna do some sketches and ask for some dimensions (including bacis engine dimenions for FEA) within the next few days (time is a precious and rare commodity right now).

Kurt

P.S. Goodbye Schumi. Hello Kimi!

Sounds good Kurt, not sure what these mounts cost yet, I'll try to get that tomorrow if I have time at work. 

Let me know what dims you need and I'll do my best.

Fred