E30 M3 S62 Build - Loads of queries about 4x4 drivtrains

[The Dark Side of Will]

as u see it in the pic its just resting, but quite comfortably id say. It would be a case of welding a couple of bosses and the drilling and tapping them.

What would be the effects if I was to slide the rack across and inch or so to allow for the diff etc? I imagine id need to shorten one push rod and extend the other?

Been going over this with the guys on E30 tech for MONTHS.

If you move the inner tie rod ends from their stock locations, you *WILL* create bump steer.

[nando]

yes, I understand that. the question is, how much and will it matter?

but if an E30/E36 rack is the same width, it might make more sense to use that if you could make mounts.

[Turk]

would a bump steer correction kit not solve this? How many degrees will an inch of movement really effect the angle and parallelness between the drive shaft and tie rod? very little based on triangulation maths.
2-3mm increase one side, and 2-3 mm drop the other id imagine.

Also bear in mind the engine and subframe may (probably in fact) have to be lowered too. Just like the 300mm.de 20mm spacer kit does. So either way I think it will need a correction kit

[The Dark Side of Will]

<sigh> here we go again...

As BMW built the car, it has a certain bump steer curve. The position of the rack is chosen so that bump steer is minimized at stock ride height. Lowering the car puts the suspension into a range of its travel where bump steer is greater than it was stock. Bump steer correction kits just space the steering arms back down to essentially stock ride height.

RWD bump steer correction spacers don't work on the AWD knuckles.

Moving the rack pivots relative to the inner ball joints for the control arms will change the *shape* of the bump steer curve. *UNLESS* you know the shape of the stock curve, you won't be able to predict how moving any given pivot will change the shape of the curve.

Yes, 2-3mm matters.

Spend a few minutes on Google looking up how to measure bump steer. It's a pain in the ass, but absolutely necessary in situations of altered front suspension geometry in order to end up with a car that will actually perform.

[Turk]

ok, I appreciate what you are saying. But there is always a solution. Im sure something specific can be made up. or as said before move the rack in front and extend the steer arms. I wouldn't want to extend more the 5cm tbh but id definitely give it a go. maybe make something that bolts on so if it doesn't work just whip it off.

Lets talk more about steering boxes. Un assisted, quite basic and fairly compact. any know about these?

[The Dark Side of Will]

Yes, there always is, but every change involves more design, fabrication and testing... Eventually you get to a point at which you should have just built a clean sheet design from scratch.

[Turk]

Will,
Neither of us embarked upon these projects with the hope they'd just bolt together mate.
Of course theres a shedload of fabricating and testing. But essentially we are building very expensive toys. I don't know about the US, but over here a bare metal resprayed and immaculate e30 m3 with S62 will push the £40000 mark. So who knows about AWD!!! So obviously a lot of thought, money and testing will need to go into it.

While I feel I and a few others are brainstorming solutions to these issues, it seems you are just knocking them back. Although I find the negatives you have discovered extremely useful, It would be great if you could throw in the solutions you think *may* work too.

Im sorry if I sound negative, but sometimes a positive step forward with an alternative suggestion may be better for us. U never know what other ideas your suggestion's might trigger in others.

Again, I'm not being negative, and I think there are some great ideas floating about, you obviously have a huge amount of knowledge and you are being very helpful. It would just be great if you were more constructive ;)


Going back to the steering; My concern is more to do with the sump to rack to subframe spacing. Without changes to the one of the aforementioned i don't think it will fit.

Have you actually had your engine in the bay yet to measure your clearances?

I was over a friends house today, he is building a standard s62 and managed to snap this picture. He has gone a little further regarding the bulkhead to enable him to remove the gearbox without the need to remove the engine.

However, this gives us a very good view of where drivelines etc will need to be, and what will need to be modified (floor pan). The blue thing you can see is in his footwell inside the car.

What are your thoughts?

[The Dark Side of Will]

Going back to the steering; My concern is more to do with the sump to rack to subframe spacing. Without changes to the one of the aforementioned i don't think it will fit.

Have you actually had your engine in the bay yet to measure your clearances?

However, this gives us a very good view of where drivelines etc will need to be, and what will need to be modified (floor pan). The blue thing you can see is in his footwell inside the car.

What are your thoughts?

http://i776.photobucket.com/albums/y...n/1281d666.jpg

I don't have a body yet, so I haven't checked the trans tunnel clearance. That is one thing that I haven't been able to look at... Whether the engine is low enough in the bay when the transmission is as low in the tunnel as it needs to be. I don't think that the RWD trans tunnel clearance is necessarily applicable to the AWD tunnel. The AWD trans tunnel has extra space on the left side to accommodate the T-case drop and the driveshaft. Also, the crossmember clearance is obviously nothing alike relative to the RWD chassis.

I need to hound the guy who's providing my (*FREE*) FTP services to get my site back up and running so I can reference my mock-up pictures...

I had guessed that if the RWD pan will fit the RWD crossmember and allow the engine to sit low enough to clear, then the relationship of the AWD components would be the same. Of course there's zero basis for this assumption...

I'm not being negative, I'm being realistic :p
It's a big complex project, but it will be more complex than it has to be if you charge headlong into modifying thing without understanding the impacts.

For example, in excessively lowered cars, the bump steer is equal but opposite from one side to the other. On a pure two-wheel bump, there's no net effect because one wheel steers one direction and the other steers the other direction. The only result is a change in toe. The car only becomes unsettled when the suspension moves differently from side to side.
If the rack were offset to one side, then the bump steer would be equal and *ADDITIVE* between the sides... that is both wheels would steer the same direction. Thus a two wheel bump would always steer the car one way AND individual one-wheel bumps would steer the car also. Note that this is worse than the usual bump steer of a lowered car.

[Turk]

Ok, I take your points.

Re the rack; what solution are you thinking of to reduce/eliminate bump steer?

which racks have you tried and how far off have they been?

[The Dark Side of Will]

The only rack other than the stock E30 iX rack I've looked at is the E46 Xi rack. There were too many little fit problems with the E46 rack for me to want to mess with it.

The E30 iX rack *should* work fine if the left mount ear on the end fitting is modified to enable rotating the spool valve closer to vertical. It needs to have about half its stock angle off vertical in order to work around the E53 diff, the engine mount bracket and the mount tower on the crossmember.

The primary complaint about the iX rack is that it's slow compared to an M3 rack. This can possibly be fixed with a steering quickener, if a multi-u-joint steering shaft can move said quickener far enough to vehicle left (LHD car) to clear the left bank exhaust.

E30 iX's weren't imported to the UK, were they? Having a RHD car would make the steering and diff *MUCH* easier to work together as they'd be on opposite sides of the engine! :)

Checked your pics... your M3 at least is LHD. :(

Do your measurements indicate that the transmission will be too high in the tunnel when the oil pan is as low as it can be over the crossmember?

[Turk]

There are rhd ix's floating about. But both of my cars are lhd :)

I have a feeling the m3 rack will do the job. From what I remember of your Ix rack pix there was quite a lot of bulk to it. The m3 is much neater and skinnier than the e36/z3 rack that came off my car at least.

But going back to your question I think the only thing I might have a slight issue with is the auto v8 bell housing. The rest of it looks like it will bolt up fairly well. Since the getrag I'm using is a box designed to fit the e30 I'm hoping to using the original mountings as a guide for the drive line. Allbeit there may be some lowering involvolved engine side to clear the bonnet/hood.

Transmission wise I think it will be near perfect. I can see the tcase needing to be cut into the floor pan just in front of the drivers seat runner. I doubt this will effect driver as the tcase is angled down quite sharply.

My main concern now is diff/sump/rack clearances.

[The Dark Side of Will]

The only way in which the clearance to the sump and rack should be a problem is if the engine is as low as it can be over the rack and the bellhousing is still too high. I'm pretty confident in all the other clearances in terms of engine size and position.

If you get the engine as low as it can be over the rack, then the lower oil pan WILL hang below the crossmember.

The interference between The spool valve on the stock iX rack and the E53 diff is the only thing that's keeping me from having a fully assembled mockup right now.
As I said, I have a strong idea about how to fix that.

The E46 rack pushed the spool valve too far to the left. It would still interfere with the diff unless rotated forward, would interfere with the mount tower if rotated forward, required a chunk to be cut out of the crossmember immediately below the spool valve and required a mount adapter that would have raised the rack and affected bump steer.

Gordon Murray said that the automotive problem is fundamentally one of packaging. BMW's products are highly engineered and very specific considerations have been paid to getting everything to work right within the packaging constraints of the design. This not only applies when reworking the iX design, but when adapting other production components to the iX system.

For example, because of the way the crossmember is designed, in order to move the rack forward, it would have to move forward 3 to 4 inches in order for the tie rods to pass the crossmember. Lengthening the steering arms at the hubs this much would slow the steering down dramatically, as well as perhaps not fitting inside 17" wheels. Moving the rack without lengthening them will change the ackerman angle of the suspension significantly... not a huge deal, but definitely a nuisance.

Fundamentally, if I am dissatisfied with the iX steering rack, I will commission an aftermarket company to produce a replacement identical in fit but with a faster ratio and different weighting.
For example:

http://www.mavalgear.com/unisteer.html

http://www.woodwardsteering.com/

http://www.titan.uk.net/steering.php

http://www.flamingriver.com/index.php/products/c0014/s0005

There might even be something workable in the Quaife catalog, although I seriously doubt they'd be willing to build just one...

[The Dark Side of Will]

This won't affect my build, but might be useful to you if you're using the E34 T-case.

I just had a *duh* moment regarding my proposed "Fixed yoke conversion" for the front output of the E30 and E34 T-cases.

I had been thinking that the yoke itself would have to be made from scratch, which would be an effort that is not inconsequential.

However, I realized that the yoke could be made using only the front end of the ruined driveshaft. Since the driveshaft would be scrap anyway and is probably already in the car, it's available essentially for free.

The fitting would be made by parting off the shaft 4-5 inches (whatever depth is required to bottom out the yoke in the front output sprocket) from the front differential flange. The 4-5 inch section would be splined to take advantage of the full length of spline engagement in the front output sprocket, drilled axially and tapped.

The T-case would be disassembled and a hole drilled in the back of the front output sprocket, along with a corresponding hole in the rear case half. The T-case would be reassembled. The yoke would be installed and secured into the sprocket with a bolt that would be installed through the hole in the rear case half.

I haven't figured out *exactly* how the hole in the case half could be sealed yet, but there are enough, bungs, fittings, plugs and caps on the market that something relatively simple could be bought and installed. It would probably be necessary to weld the bung to the rear case half, but that's not a big deal.

[Turk]

Those custom racks look interesting indeed :D Though I was having another play today and am beginning to think that the m3 rack may be a fit.

Could you do me a favour and measure from the centre of the rack 'body' to the upright of the knuckle/upright housing? Don't know if I've quite explained that properly but my brain has turned to mush and I can't remember the proper word :p

Part of me still thinks a manual rack might be the way to go. No banjos and a much skinnier set up. maybe something off of a 316 or such?

Are you going to create a 'centre bearing' for the front shaft? Maybe mount it to the sump, then a long spline to give some movement coupled through the bearing maybe?

Have you drawn up any diagrams of your fixed yoke theory? though i think I know what youre saying I'm struggling to picture it.

[The Dark Side of Will]

I made the mistake of planting the idea in my Dad's mind of building my mom's car into the "first of kind" automatic S52B32 powered E30 iX, so I may yet build the fixed yoke myself, in which case I will thoroughly document it.

I can sketch a couple things up too.

I really don't think you want a manual rack in a V8 AWD E30... Not fun even with the M20 from what I hear.

Unless there ends up being serious interference with the driver's footwell, I'm expecting to use a one piece driveshaft with u-joints at both ends... although I'll have to build some plunge into it somehow. I may either use a CV at one end or find a plunging fitting to incorporate in the middle.

There "shouldn't" be any movement between the T-case and the diff, *BUT* the engine and transmission case are made of aluminum and climb by about 150 degrees F from cold start to operating temp... Being bolted to a rigid steel driveshaft that doesn't change temp as much and doesn't grow as much with the temp it does change will be a recipe for some eventual problems.