24V AWD Swap Knowledge Base

[The Dark Side of Will]

Hopefully boost by gear will help the durability.

Will you still need it with at least 50% more traction?

[Nisse Järnet]

Will you still need it with at least 50% more traction?

Its mostly to keep the torque to a minimun when in 1st and 2nd gear, less stress on the front end. Buuuuut im sure i will test first and if the parts hold up then turn the boost up :D

[Nisse Järnet]

Allright, the TC is now mounted to the gearbox :) The downside is that you need alot of cutting under the car :P And i still have some more job to do with the firewall...thought i was done with that :(

Well well, im getting there!

[The Dark Side of Will]

Ok so after todays tests with a M50 in there im 99% sure we have to do something with the firewall!
Hopefully removed insulation and brake pipe clips will do it but it might not be enough.

With the engine like 1cm more back the CVs and diff clears everything, its veeeeery close as it is!





Will do more tests tomorrow! (engine is not 100% positioned on the pics)

I just added this to the front page post.
Please confirm that it would not be necessary to modify the firewall IF the engine and transmission were bolted together outside the car, positioned while the suspension crossmember was removed from the car, and then the crossmember bolted back in place.
Does that sound reasonable?

Or will you end up with the wrong driveline angle? (e.g., with the engine in place and firewall not modified, the TC has to be too high in the body to fit)

[Nisse Järnet]

After todays test i think you have to modify the firewall no matter what :S On those pics the engine was to high in the rear (even though it looked right with the sump etc)
But now when i was able to test fit the trans and TC theres now way the engine can sit that high in rear.

Its like you say, the TC and trans would end up too high, so you have to modify the trans tunnel pretty much.

As it sits now the firewall is beat up and a little cut out and the area around the TC is cut out here and there and a little beat up as well :P
And at this position the crank center line (or what to call it) and the TC output flange center is pretty much the same where the M20 was.

If the engine could be mounted more foreward pretty much all of theese problems would go away, but on the other hand you have to make a new custom crossmember/rack etc.


But please dont take all this as 100% true yet as the positioning of the engine and all that isnt completley finished yet. When everything sits bolted down i will know for sure :) Hopefully thats not too far away!

[nando]

Or modify the pan and move it to the same position as the M20. :P

[Nisse Järnet]

Or modify the pan and move it to the same position as the M20. :P

Yeah if i dont get this to fit without more firewall work i might try to move the diff mounting back a little.

Some pics:

[The Dark Side of Will]

After todays test i think you have to modify the firewall no matter what :S

Its like you say, the TC and trans would end up too high, so you have to modify the trans tunnel pretty much.

:-(

If the engine could be mounted more foreward pretty much all of theese problems would go away, but on the other hand you have to make a new custom crossmember/rack etc.

Actually... I've been thinking about this...
It should NOT be very hard to make a new crossmember. I have the fixture about halfway built in my head and I know guys who could build the fixture and subsequent crossmembers quickly and easily.

I'd move the stock rack forward about 1 - 1.5". How far forward does the engine have to move in order to not modify the firewall at all?

Moving the rack FORWARD does NOT affect bumpsteer. It will affect Ackerman angle, but that's a little messed up on the iX already.

I can also include bosses to mount another type of rack (E36 M3, E46 Xi, etc), but I have no idea how the lengths of those racks compare, so I do not know how swapping racks will affect bump steer.

So here's the basic features of what I've been thinking of:

-1/4" steel plates bolt the crossmember to the body
-The "main hoop" is either heavy gauge DOM or square/rectangular tubing.
-The stock rack mounts 1 or 1.5" (2.5-4cm) forward of the stock position
-Additional rack mounts can be provided, as long as they don't interfere with rack mounts already in place. (IOW, I can add as many different rack mounts as people want different racks, as long as they don't overlap.)
-The stock control arm mount locations will be preserved
-It will be possible to RAISE the stock control arm mounts (2"?) in order to preserve roll center and camber gain on a lowered car (This will also require lowering the outer tie rod ends via a bump steer correction stud in order to avoid wicked bump steer)
-It would be most straightforward to duplicate the stock engine mount tower mounting points, BUT it would be a fantastic value add to provide for locating the engine mount points such that common mount arms could be used.

If all of you want to move forward on this, let's figure it out.

Right now we have 4 takers: Me, Nisse, Nando, FlyboyX
Does anyone else want one? I can have a batch of 5 made, and I'll take two as I have a 332iX autotragic build to do.

I'll need mounting center dimensions for each rack we might want to use.

We also need to settle on engine mount arms.

For my swap I need to use E39 V8 arms, but I might be able to use E34 V8 arms (not sure about oil filter and external oil cooler connections). If I use E34 V8 arms, and all you 24V guys agree to use E34 I6 arms, then we can make one style of crossmember that will support both 24V and 32V swaps.

[Nisse Järnet]

Do you have any idea of how long that would take? I might be in for one but im almost there already :)

[nando]

Hmm. Interesting. I'm torn - it goes against my goal of using mostly stock parts, but that's just not going to work somewhere. I will have to modify the pan, build mount arms from scratch, customize the subframe, etc. and it still probably won't be in the "correct" position. I 100% do not want to take a hammer to the fire wall (any more than I did to fit the RD headers, which isn't much).

I think to keep things simple, we should leave things like control arm mount points alone. A lowered ix is more affected by maximum CV shaft angle than the control arms. Being able to fit any other rack would be a huge bonus - I'm thinking forget the E46 xi rack, being able to run any common RWD rack like from an E36 M3 would be even better.

obviously this is just milling around in your head, but here are my thoughts.

the stock subframe is pretty light. going with tube steel will certainly be a lot stronger, but also heavier. I think we'd want to avoid going overkill on strength in the interest of keeping weigh reasonable. luckily steel is much stronger than aluminum as far as strength to weight, and our subframes aren't even billet. they're crummy cast parts.

I agree that settling on one set of mount points makes the most sense. E34 mount arms for both V8 and I6 seem like the best bet. I'd like to be able to use stock mount bushings though - I think a lot of thought went into how the E30 ix mounts are assembled and function.

If the subframe is custom we can keep the rubber bumper thing. Another well thought out idea that keeps the engine out of the radiator and takes some load off the mounts.

Engineering - a lot of guys just grab random steel and weld it all together. most of the time it works fine because steel is a really nice material. But it also means the end product weighs more than it needs to. I might be able to help here - I'm surrounded by steel designers, engineers, detailers, fabricators, etc. I'm looking for a reason to learn FEA too. :)

I'm also close to the engineering department at the local tech school. Maybe a student wants to take on a project?

Costs? I suppose if you have a design ready to build that uses common materials & sizes, and the construction is thought out, it doesn't have to be insanely expensive, but I'm thinking it would probably still be several hundred bucks? I figure I'd probably be looking at $150-200 for custom mount arms, and another $150 to have the oil pan modified, so it could similar or cheaper.. and that doesn't even count what I was thinking for the subframe.

If I don't have to make one-off engine mounts, a one-off modified/hacked up subframe to fit my one-off steering rack, all to clear my one-off customized oil pan, and have something that I can basically bolt in with the bonus of being able to run different racks, that'd be really damn cool. We should keep this conversation going, maybe it's feasible. heck, if it's a 3D model Nisse could have one built in Europe instead of shipped over the Atlantic.

[flyboyx]

well now....this is something i hadn't thought of. i like the idea will. i really don't want to fuck up my fire wall either.(if it can be helped) my swap mantra is generally along the lines of chris's when it comes to using as many stock parts as possible. i think the thought of "fixing" the front crossmember is potentially a better option than re fabbing the pan. that is a complicated sump and it would be really hard to redo it in a way that would make an acceptable part. there are lots of obstacles to re fabbing this pan. warping for one. doing a good enough job to make the sealing edge to the block proper is another. there are lots of curves and complex surfaces to contend with too. also, if something goes wrong in the fabrication process, you have to go all the way to germany to get another one.

i like the idea of using an e36 steering rack (2.7 turns from a z3) but the mounting holes are on the wrong side. i'm sure there must be a way around that.

the rear ears on the ix subframe will be in the way of the axles if the engine is pushed forward that far. something will have to be done to offset this.

the ackerman issue is something to take a close look at. maybe you can run some calculations to see how much effect moving the rack forward an inch would have on handling?

i'm getting ahead of ourselves but for my application, i would like to use the mounting holes on a rwd subframe if possible. i could aways fab that part on my own.

other than these issues, i say sign me up!

[The Dark Side of Will]

Do you have any idea of how long that would take? I might be in for one but im almost there already :)

I think 2 months would be reasonable. I don't work at a welding shop, so I'd be doing this in my spare time... not that I'm not good at it ;) it's just not in my daily life.

I'll need you to take some measurements of your engine and body so I get the crossmember in the right location relative to my mockup engine.

I agree that settling on one set of mount points makes the most sense. E34 mount arms for both V8 and I6 seem like the best bet. I'd like to be able to use stock mount bushings though - I think a lot of thought went into how the E30 ix mounts are assembled and function.

If the subframe is custom we can keep the rubber bumper thing. Another well thought out idea that keeps the engine out of the radiator and takes some load off the mounts.

Engineering - a lot of guys just grab random steel and weld it all together. most of the time it works fine because steel is a really nice material. But it also means the end product weighs more than it needs to. I might be able to help here - I'm surrounded by steel designers, engineers, detailers, fabricators, etc. I'm looking for a reason to learn FEA too. :)

If I don't have to make one-off engine mounts, a one-off modified/hacked up subframe to fit my one-off steering rack, all to clear my one-off customized oil pan, and have something that I can basically bolt in with the bonus of being able to run different racks, that'd be really damn cool. We should keep this conversation going, maybe it's feasible. heck, if it's a 3D model Nisse could have one built in Europe instead of shipped over the Atlantic.

I'm guesstimating $300 per right now
I work in aerospace (starting a new job today!) and have a pretty good eye for structures and SIMPLE designs. I should be able to keep it within a few pounds of the stock crossmember, as well as staying strong.

Do you want to use stock iX mounts? I was expecting to use the mounts that went with the mount arms. Do E34 6 cyl and 8 cyl mounts have different heights, for example? If they do, then using the same mounts with the different arms wouldn't line up with common locations on the crossmember. That's something I'll have to verify.

EDIT: The M50 E34 525i shows 11811133364 for both mounts ($48.62)
The M60 E34 540i shows 11811094149 for left and 11811094150 for right (each $76.68).
Hmmm...
(Of course both use the same crossmember, unlike the E39)

My first step will be having the CMM guy in the QC lab in the machine/welding shop where my dad works whip up a data package on my spare crossmember. That will tell me where all the holes and machined surfaces are.
With that info, I can figure out where the altered rack mount points will need to be.
From there, I'll sketch up a fixture baseplate for them to laser cut from 1/4" or 3/8" plate.

I can bolt that down to a mil table and use the DRO to locate each feature and tack weld some cut-to-length piece of hollow round bar to the baseplate in the correct places to locate the rack mounts.

The locations to bolt down the engine mount towers are a little more finnicky, but should not be too bad. I have my dad's S52 to use for mockup... not sure if we already have E34 mount arms or not.

We can make provision for keeping the bumper, one way or another.

my swap mantra is generally along the lines of chris's when it comes to using as many stock parts as possible.

The custom crossmember allows us to use a LOT MORE stock parts than we would otherwise be able to do ;)

i like the idea of using an e36 steering rack (2.7 turns from a z3) but the mounting holes are on the wrong side. i'm sure there must be a way around that.

Have one you can send me? ;)
I can build the crossmber to take rack mounts on either side, for example... or maybe the E36 rack bolts to the middle and the iX rack bolts to the edge. There are ways.

the rear ears on the ix subframe will be in the way of the axles if the engine is pushed forward that far. something will have to be done to offset this.

I'll look at my car and keep an eye on this. There are ways. The hardest part of the automotive design process is packaging.

the ackerman issue is something to take a close look at. maybe you can run some calculations to see how much effect moving the rack forward an inch would have on handling?

Ackerman only really affects parking lot maneuvering. It has to be REALLY REALLY screwed up before it starts to affect handling.

My assessment from driving my car is that it has some tire scrub when maneuvering at full lock to get into a parking space. Is this what you guys note about your iX's? Is my car screwed up? Is my perception screwed up?

The primary factor affecting ackerman is the angle between the steering arm and tie rod when the car's going straight. The iX steering arms are limited in the angles they can use because of how compactly the knuckle, hub and rotor combo has to package in order to fit inside a 15" wheel of reasonable offset. I'd *GUESS* that this means the rack is already further forward than it needs to be, and moving it even further forward isn't going to help anything. However, like I said, Ackerman has to be incredibly screwed up before it affects handling.

If I'm wrong and the car's ackerman is already good, then it won't be hurt much by moving the rack forward.

i'm getting ahead of ourselves but for my application, i would like to use the mounting holes on a rwd subframe if possible. i could always fab that part on my own.

Why? Doesn't that conflict with the goal of keeping the crossmember out of the way of the axles as the engine is moved forward?

other than these issues, i say sign me up!

Cool!

[flyboyx]

I work in aerospace (starting a new job today!) and have a pretty good eye for structures and SIMPLE designs. I should be able to keep it within a few pounds of the stock crossmember, as well as staying strong.

fuck yeah! congratulations on the new job, man! hope it turns out to be a good one.

Do you want to use stock iX mounts? I was expecting to use the mounts that went with the mount arms. Do E34 6 cyl and 8 cyl mounts have different heights, for example? If they do, then using the same mounts with the different arms wouldn't line up with common locations on the crossmember. That's something I'll have to verify.

I would say the black uuc polyurethane 24v swap mounts would be the best but they are expensive. edit: i just checked their site and i can't find them so maybe they were discontinued. i also like the stock ix mounts. they are low profile and seem like they could be a good choice.

My first step will be having the CMM guy in the QC lab in the machine/welding shop where my dad works whip up a data package on my spare crossmember. That will tell me where all the holes and machined surfaces are.
With that info, I can figure out where the altered rack mount points will need to be.
From there, I'll sketch up a fixture baseplate for them to laser cut from 1/4" or 3/8" plate.

I can bolt that down to a mil table and use the DRO to locate each feature and tack weld some cut-to-length piece of hollow round bar to the baseplate in the correct places to locate the rack mounts.

The locations to bolt down the engine mount towers are a little more finnicky, but should not be too bad. I have my dad's S52 to use for mockup... not sure if we already have E34 mount arms or not.

We can make provision for keeping the bumper, one way or another.

sounds like a solid plan. i guess i have a subframe that is 4 bolts from being off the car. i suppose i could send along one of these too.

Have one you can send me? ;)
I can build the crossmber to take rack mounts on either side, for example... or maybe the E36 rack bolts to the middle and the iX rack bolts to the edge. There are ways.

i have an e30 rwd rack i would be more than happy to send along. the mount points are the same but i think the steering shaft tower might be in a slightly different location.

My assessment from driving my car is that it has some tire scrub when maneuvering at full lock to get into a parking space. Is this what you guys note about your iX's? Is my car screwed up? Is my perception screwed up?

i haven't had this problem with stock wheels and tires. 215/45/17's are another story.

The primary factor affecting ackerman is the angle between the steering arm and tie rod when the car's going straight. The iX steering arms are limited in the angles they can use because of how compactly the knuckle, hub and rotor combo has to package in order to fit inside a 15" wheel of reasonable offset. I'd *GUESS* that this means the rack is already further forward than it needs to be, and moving it even further forward isn't going to help anything. However, like I said, Ackerman has to be incredibly screwed up before it affects handling.


If I'm wrong and the car's ackerman is already good, then it won't be hurt much by moving the rack forward.

assuming this is the case, its all well and good. it goes without saying that no one wants to mess up the car's handling characteristics. i think its safe to say that moving the rack forward would make the car less able to turn the wheels at a sharp angle. i could probably live with that.

Why? Doesn't that conflict with the goal of keeping the crossmember out of the way of the axles as the engine is moved forward?

well, because this:


plus:









plus:



=awd m3 cabrio.

i am going to use the stock frame rails to keep alignment. since they have the ix holes in them anyway, i guess it really isn't a big deal. i will just have to find a way to open them up and install cage nuts to hold the subframe on.

[nando]

if it's $300 count me in. I'm sure I'd spend more than that on what I'd have to do to make it work before.

yeah, I'd like to use the AWD mounts - the RWD mounts aren't designed to take drivetrain forces. well, they don't have the cup/bumper things. I don't care about the mounts specifically but I'd like to use those.

get me some measurements/sketches and I can build you a model. :)

[LJ851]

Ackerman angle is determined by the position of the outer tie rod end in relation to the pivot (kingpin) of the front wheels triangulated back to the centerline of the rear axle, not the steering rack location. A given strut assembly with a steering arm mounted in the same place on the chassis is going to have damn similar ackerman regardless of where the steering rack is.

Location of the steering rack affects bump steer and there generally is not multiple places to locate the rack and keep bumpsteer in check (within reason)

I can assure you that you want to avoid toe out bumpsteer under compression at all costs !

I also agree that ackerman or positive or negative ackerman is not super critical (within reason)

Not trying to call anyone out here, just trying to help you guys succeed.





tl;dr :
Don't worry about affecting ackerman, focus on keeping bumpsteer in check.