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M2 redux


Ian

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It's been awhile since I had time to post, but I've been working away on the car as time permits.  I wanted to get the rear of the car squared away, so I worked on diff mounts for the Alpina diff cover.  The Alpina cover was actually made for the e21, and bushings were surprisingly hard to find, but I eventually found some nice urethane bushings from Eurometric.  They installed easily, and I was able to hang the diff. However,  the passenger-side mount was offset about an inch from where the 2002 mount would be.

Diff_Cover_Installed.jpg

Hanger1.jpg

I was also less than thrilled with the sheet metal that mounted the diff.

Diff_Cross Beam.jpg

So I decided to cut out the rusty 19 ga sheet metal, and welded in a piece of 14 ga square tube, to which I would tie-in the cage on top, and the diff on the bottom. Here you can see the first cut to open up the area, and then the square tube tacked in place, and then welded in.

Diff_Mounts.jpg

IMG_0720.jpg

I then made some brackets to mount the diff from some 12 ga steel I had leftover from making the cage base reinforcements.  I braced them to the rear trunk floor with some scrap .065 DOM tube. With hindsight this was probably overkill, but rather than cutting it out and remaking, I'll see how this works and then make it a bit lighter at a later date.

IMG_0724.jpg

2019-02-06 20.17.07.jpg

These rear mounts were not removable, and to ease installation I made a second set for the other side of the bushings that were removable, and bolted to the underside of the trunk floor.  I thought I should reinforce the top, but the stock floor in this place has lots of undulations, which would make fabricating a bracket difficult.  So I cut out the area and replaced it with some flat steel.  However, I didn't need all the area to bolt up the brackets, so I got excessive  with the dimple die and "added lightness" to the panel before welding it in place.  

DIff_mount - 1 (2).jpg

Then I made an X-brace for the rear cage connecting to the square tube that supported the new diff mounts.  You can just see the bolts for the removable diff brackets ahead of the X-brace, which is just tacked in place for now.

Cage_Tie-in.jpg

That's all for the rear for now.  I need to get the exhaust sorted before I weld up the rear firewall or finish the rear of the cage.  So now to the front of the car.

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Ian
'76 M2

'02 325iT

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15 minutes ago, Ian said:

It's been awhile since I had time to post,

only a year and a half!

 

good call on the modified diff mount Ian!  classic scope creep!

 

i can't give you too much of a hard time about M2 work...i have not done much recently at all.

2xM3

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3 minutes ago, M2M3 said:

LOL...mine too...

Y'all just don't know when to leave well-enough alone!

 

??

Ray

Stop reading this! Don't you have anything better to do?? :P
Two running things. Two broken things.

 

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5 minutes ago, Ian said:

 

Now what fun would that be?

True, true.

 

And I know -- I just don't drive my car properly enough to break things...

 

... recently!

 

?

Ray

Stop reading this! Don't you have anything better to do?? :P
Two running things. Two broken things.

 

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Moving to the front of the car, I have to deal with the radiator.  I picked up a beautiful Ron Davis double-pass Chevy radiator a long time ago, and Marshall has continued to give me grief because he thinks it's too large for this car.  And I have to finally admit he's right.  I thought I could do some creative cutting to make room for the large radiator, but I could not find the room.  I decided to go instead with a Mishimotor aluminum radiator made for the e30 M3.  It's significantly thinner than the Ron Davis, and fits much better. Here are the two radiators next two each other,

0.5-Radiator-front_Subframe - 1.jpg

The Mishmoto actually stacks up pretty well against the usual competition:

 

320i radiator: 268 cu in core volume, 17 lb total weight (radiator + water)

Mishimoto: 483 cu in core volume, 13 lb total weight

Ron Davis: 697 cu in core volume, 19 lb total weight

 

So the Ron Davis radiator only weighed 2 lbs more than the usual 320i radiator, but couldn't fit.  The Mishimoto is almost 2x larger in capacity, and actually weighs less than the brass 320i radiator.  So I think I'll run an M3-style cooling system, but move the header tank to the front of the engine bay since I don't have room at the rear where the M3 has the tank.

 

All this radiator discussion reminded me of how far forward the S14 always seemed to me in the 2002.  And mine always seemed high, rubbing on the underhood insulation.  I wondered what the engine would look like down 1", and back about 3".  The only problem is that the VAC oilpan would hit the subframe.  So just for giggles I removed the subframe and positioned the engine with my engine hoist, and made some temporary engine mounts out of 2x4s.

1-engine-Front_Subframe - 1 (4).jpg

I really like this!  The engine fits the engine bay much better.  The IE drop sway bar needed to be spaced down 1/2", but it fits nicely and acts as a nerf bar to protect the oilpan.  An added benefit to moving the engine back is that the header now clears the pitman arm.  If you look at the yellow arrow in the pic below, it shows the part of the S14 header that has to be "massaged" with a BFH to get clearance.  Now the header is far enough to the rear that even with a lowered engine there is plenty of clearance.  Win!

2-Header-Front_Subframe - 1 (3).jpg

Edited by Ian

Ian
'76 M2

'02 325iT

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Okay, the engine looks cool and fits better moved to the rear.  What's stopping me from doing this?  Well, the subframe for one.  The 2002 subframe is made from stamped steel, and is folded for structural rigidity.  As a result it projects about 6" forward from the mounting point for the control arms.  I wondered if I could replace some of this stamped steel with some 1.5" DOM tube I had left from the roll cage build?  After debating this step for about a week, I broke out the cut-off wheel and removed a bunch of structure from the subframe.  And it fits! 

3-Cut subframe F.jpg

Now I had to restore the structural integrity with some DOM tube. My thought was to have a horizontal tube that I could weld to the original cross section, thereby leaving the mounting points for the control arms intact, and maintaining the suspension geometry.  Here is a test fit.

4-guides-Front_Subframe - 1 (2).jpg

I drilled holes through the tube, and fitted the guide tubes from the stock subframe though.  The idea is to maintain the stock bolts, and trim the guide tubes to fit the 1.5" tube. The plan went through several iterations, and I eventually made the cross tube with bends at each end to reach down to tubes running along the old (flimsy) mounting surfaces of the subframe.  To prevent distorting during welding, I found some scrap 1/4" wall square tube, and made heavy jig that I drilled and tapped so I could bolt the DOM structure down.5-welding-Front_Subframe - 1 (1).jpg

I also needed to make some cross tubes to go into the base for the bolts, to prevent the bolts from compressing the tubing. It was actually diffictult to find thick-wall DOM tube that would accommodate the M10 bolts that are used to attach the subframe to the chassis.  Most thick-wall tube of this size had too small an ID to accommodate the M10 bolts.6-legs-Front_Subframe - 1.jpg

The answer was to find some thick-wall tube and drill it out on my drill press.  I would have loved to use a lathe or a mill, but lacking those tools I used the tightest undersized drill bit I could use to center the tube in a vise that I clamped to my drill press table. After everything was centered I changed bits to a larger bit and drilled out the tube to fit the M10 bolts.

7-drilling-Front_Subframe - 2.jpg

I capped the tubes by cutting out some 1.5" holes from 14 ga steel with a hole saw, and welding them in to each end of the tube.

 

Edited by Ian

Ian
'76 M2

'02 325iT

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Stay tuned for Ian's car terrorizing a track near you -- in 2025!

 

:D

 

I believe JimK runs a Mishimoto also. I may be interested in doing that as I get heat soak in stop and go. I have read that others solved that with an electric water pump, and specific kits are available.

 

Cheers,

Ray

Stop reading this! Don't you have anything better to do?? :P
Two running things. Two broken things.

 

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And the moment of truth: it fits!  Here is a picture of the DOM C-shaped brace that has been fully welded and then tacked in place to the subframe.  I cut out the structure of the subframe side rails, and am largely using them as mounting points for proper alignment with the chassis.

8-Oilpan_01.jpg

The forward edge of the masking tape shows how far forward the stock subframe overlapped with the oil pan with the engine this far back.  I also gusseted the corners of the C-brace before attaching the new structure to the subframe.  After bolting the DOM tubing to the subframe and chassis, I tack welded the assembly and then removed it for welding.  To prevent warping, I bolted the subframe assembly back down to my welding jig, and then fully welded the C-shaped DOM brackets to the minimized subframe.  

9-welding-ubframe_Welding_Jig.jpg

Here is a comparison of stock vs narrowed subframe. The modified subframe has considerably more room for the oilpan, particularly in the corners.  Overall, I'm quite pleased with how this came out.  It gives me more room, is probably stronger, and is about 5 lbs lighter than stock, so even if I box in some sections its likely to not be heavier than stock.10-subframe_Comparison02.jpg

Of course, there is one drawback to moving the engine back this far.  It does interfere with the firewall and transmisson tunnel.  I had to make some cuts to open up and make a bit more room for this test fit.

11-Firewall-Front_Subframe - 1 (1).jpg

Modifying the firewall and tranny tunnel are the next step in this project.  However, first I need to make some motor mounts to get the engine position fixed, and then I can send my driveshaft off to get it shortened.

Ian
'76 M2

'02 325iT

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  • 3 weeks later...

I was setting ride height and measuring compression and droop when I notice the control arm was hitting my modified subframe, and had bent the flange of the arm around one of the bolt heads that mounted the subframe to the chassisBolt_Interference_01.jpg

This was a setback.  But I figured if I cut out that corner and lowered the bolt head, I might get the clearance I need.  And it worked!

Bolt_Interference_02.jpg

The arm clears the bolt head, and I can plate this up later.  For the moment I'm going to throw this back on the car and make sure everything clears, and then go back to setting up the suspension.

Ian
'76 M2

'02 325iT

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