Refreshing the rearend. AKG 85A subframe bushings and AKG trailing arm bushings. Also installed stainless brake lines through out the entire car.
Ran AKG 75D 12mm subframe riser bushings for a bit but didn't care for the added NVH and have since went back to the 85A's but flipped to get the subframe 6mm higher.
Next up it was time to replace the tired slow original steering rack. Of course i went with a z3 1.9 for a nice quick ratio.
At the time of install there seemed to be a lot of speculation on whether to put the rack spacers above or below the steering rack. I ended up putting them below and haven't had any noticeable bump steer.
Made a new firewall plate to locate the steering shaft boot down to alleviate grommet riding issues.
Also replaced the rotted steering shaft guibo with this.
For a time i was bit by the autocross bug.
During that time a few things became apparent. Bilstein sports are not up to the task of damping and contact patch is king in autocross.
Revalved ix front inserts and e30 sport rears valved to turner jstock specs. Running 650F/750R spring rates.
Shortened strut housings to accommodate the shorter inserts with m3 style sway bar endlink attach brackets.
Spacer to go underneath the insert to take up the additional room in the housing. Made of ferrous material for easy extraction with a magnet.
Ground control front camber plates and rear shock mounts.
I don't why but i always liked this picture.
It took me a few wheel and tire combo's but eventually i came to the conclusion i wanted to run 17x9's with 245's square, with out hacking fenders. This car was inspiration.
Fitting 17x9 team dynamics pro race 1.2's with 245/40/17's. Tire pictured is a used tire for test fitting purposes. Ended up going with Hankook RS3V2's. With a bit of fender rolling, proper offset (et27 with 12mm spacer up front), and reasonable ride height they fit quite nicely. A bit of trimming to the front fender liners was required.
Time to get rid of the hot air intake i've had since the new engine went in. I was wanting something with a relatively stock look. Ideally i'd have modded the stock air box but there just isn't much room there. Eventually i happened upon an early model with a stamped steel air box. Found out later it's also available in m20 powered e28's. I liked the potential it had and the weldability. While browsing around the yard i found a small bellmouth inside the airbox of a nissan something or other.
Comparison to stock.
Went through a few different ideas and eventually discovered that the expanded end of 3" slip fit exhaust pipe fits snugly inside the airbox upper plenum opening and that the nissan belmouth fits perfectly inside of that. So there it was my rough idea of an intake.
Holes in expanded end to plug weld the bellmouth in place.
Time to open up the airbox inlet to 3".
Found this bellmouth inside the airbox of a 740 iirc for use forward of the engine bay heat shielding.
View from behind the headlight.
Finished product pre paint. Slightly different configuration than above.
Time to head to the dyno to see if it's worth making pretty.
Gained 1 ft/lb peak tq but lost 2 hp peak power.
One thing to note is this wasn't exactly an accurate test. The dyno runs were done with the hood open giving the open intake cooler air than it would normally get should the hood be closed. I say this all works in the favor of the closed airbox though. Even so i'll take the unnoticeable 2 hp hit for better all around drivabilty. No more erratic idle and annoyingly loud induction noise.
Finished Product
Make no mistake, even though it's a closed intake when the car is at a stand still temps will climb regardless. Data logging revealed idling temps will creep up just as they would with the open intake just not quite as fast. Everything in the engine bay wants to become the same temp when it heat soaks. The advantage comes when it's time to take that first big gulp of air. Intake temps come down much faster and stabilize about 10* cooler at cruise than the open intake.
Started to get a bit of inside wheel spin during autocross so it was time for a purpose built LSD. I also planned to replace the diff bearings at the same time. I won't make this a detailed how to as it's been covered pretty well by others but rather a general overview. Here's a couple links to some reference material.
Great small case LSD build by Andrew from IE known as skifree on this forum.
http://www.bmw2002faq.com/_/technica...tial-build-r74
Detailed medium case build on ohiobimmers. Must register to view but it's worth it.
http://www.ohiobimmers.com/forum/showthread.php?t=3624
If you were previously unaware the LSD's that came in our cars were manufactured by ZF. ZF called it the Lok-O-Matic. ZF also provides LSD's to other auto manufacturers, such as porsche, alfa, ford uk, and many others, so there are a lot of resources out there outside of the bmw realm.
ZF overview document on the lok-o-matic
ZF lok-o-matic tech spec document all in german. If anybody has this doc in english please share.
Here's a page out of the above doc but in english that shows how ramp angles and disc configuration effect lock.
Video explaining how clutch/pressure ring type LSD's work
E30's came stock with a 2 friction disk 25% lock LSD's which corresponds with Fig A above. That would be 45* ramps on accel and decel. I decided to build a 4 friction disk unit with 30* ramps on accel and 90* ramps on decel essentially making a 75%/0% LSD. Or, what some might call a 1 way LSD. The 30* ramps are on the accel side to provide additional lock while the 90* ramps on the decel side lower decel lock to act more like an open diff to help with turn in.
Sourced a decent 3.73 LSD core.
LSD unit out...
...and apart.
4 disk stack with 30/90 ramps machined by diffsonline.
In order to add the 2 additional friction discs at approximately 2mm each and 2 additional dog eared plates at approximately 2mm each we need to remove 8mm from the LSD housing. 4mm on each side. This is done by removing a 4mm spacer from the bottom of the LSD housing and also removing 4mm of material from the LSD housing end cap.
4mm spacer removed from the bottom of the LSD unit.
4mm of material removed from the LSD end cap. Not my pic but shows additional material removed.
Here's mine.
I don't have any pics while assembling the LSD but it's pretty straight forward. Take your time and make sure all parts are lubed adequately.
Checking break-away torque. IIRC mine was about 80 ft/lbs. This was with the plates lubed with 75w140NS fluid. Should be about perfect with friction modifiers added.
The rest of the diff rebuild went as expected. I'm not going to cover it just follow the TIS and you can't go wrong. I will mention a few tips i learned though.
Obviously you're going to need some special tooling for this job. I found everything i needed at harbor freight for under $200. This included the 12 ton press, bearing race and seal drivers, and a couple bearing splitters. The rest i made.
Examples of tools for holding the pinion and checking LSD break-away torque but also carrier preload.
Wet sharpie ink works well for checking the contact pattern.
Crush sleeve which allows for precise preload of the pinion bearings. The window from a little too little preload to a little too much is tiny and it's extremely easy to over shoot. Make sure to order extra's.
Pinion nut scribe marks made before disassembly happened to line up after pinion was preloaded so use that as an indicator of nearing the preload range.
For pressing the new bearings in with out damaging them use the old bearings inner collar. To do this cut the cage off the old bearing and open up the ID with a sanding drum until it slides over the applicable shaft. Now you have an adapter perfectly suited for each bearing.
That's that for the diff. Performance is as expected. A nice amount of lock on acceleration and great turn in. Also no more dreaded inside wheel spin.
Well that pretty much brings us up to the current state of the car. I've been enjoying it for now, but we'll see what the future holds ;)
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