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      08-29-2017, 02:20 AM   #1
mattfwalters
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Exclamation Watch me ruin a Z4M Coupe: build thread

I've owned a 2006 Z4MC in Sepang Bronze Metallic over Sepang brown extended leather interior for a little over 4 years now. I bought the car in Vancouver, BC with around 50k km on the odo - today it has a little over 82k km (51,000 mi) and is in many more pieces than most people would consider "normal" or "healthy". Apologies for starting this thread mid-build; I've been documenting it elsewhere, but on a private forum, since initially this was going to be a pretty mild build. Now that this has turned into something of a monster, I figured it was time to make a thread in a public forum so that I can take advantage of more peoples' knowledge of the cars, and get more input on the build, process, thinking, time, sweat, blood, and tears that are going into my coupe.

Here's how it looked before any of the modification began:
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After my first track session with the car, it became immediately clear to me that it was a fantastic chassis, but that there was lots of room for improvement. I loved (and still love!) the S54's power delivery, but found the car to understeer badly when pushed, to be fairly poor at managing weight transfer despite the obviously high stock spring rates and meaty sway bars, and to have brakes that just weren't up to track duty in opposition to the wonderful insanity of the S54. These judgements are relative, of course - the Z4MC is so damn good on the track, but it tells you the whole time how it can be better. "I just need a little more rubber, and a little more suspension, and a little more power, and a little more brake, and I'll be perfect for you" is what it whispered in my ear the whole time.

The first round of modifications were: Ground Control coilovers with 550lb front and 700lb rear springs, GC front camber plates, rear sway delete (well, disconnect), stud conversion, 18x9.5" ET35 Apex EC-7s on all four corners (12mm spacers in the rear) with some 200AA A Kumhos, ECS floating front rotors and fresh BMW rotors in the rear, and Hawk HP+ pads. Back at the track, the results were... somewhat positive (fast lap starts around 4 minutes ):



That 2:02 lap was around 12 seconds faster than my previous best at the Ridge. As you may be able to tell from the video, I was pretty happy with it.

And then I put my foot on the slippery slope and started ordering more stuff. The parts shelves when I started the "mild" build contained:
  • AP Racing CF front splitter / rear wing
  • Evolve CF CSL-style airbox / Alpha-N tune
  • Schrick 288/280 degree cams and DLC cam followers
  • Brembo 4-pot calipers from Porsche 996 turbo (also newer Boxter / Cayman S) front / rear with RallyRoad adapters, RallyRoad lines, and Hawk HP-10 pads
  • eBay exhaust headers
  • Beisan VANOS seals, rattle fix, and oil pump

So, naturally, the first thing I did was to install the rear wing, because... reasons. It's sexy as hell, ok? See:
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A wise fellow on the other forum said "This build is bonkers. I see it as 'put on a ridiculous wing and build the car to, by God, live up to that ridiculous wing.'", which basically says it all.

So then I did the brakes:
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And holy hell, this is how these cars should have come from the factory. Solid pedal, assertive brake action, I simply couldn't make them fade no matter how hard I tried. So naturally I ordered some Castrol SRF to flush them when it's actually track time.

So, come end of May, I booked a couple of days off of work so I'd have a five-day window to get all of the bits installed, install the Evolve Alpha-N base map, and get the car to a nearby dyno and baseline it.

Late in the game, I decided to order the Bimmerworld rod bearing / ARP bolt kit, just to be safe. So you can imagine how this went.

I made a list:
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Set up the engine support:
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Target of opportunity: pulled the exhaust headers while I was mulling over how to deal with the subframe and balljoints. Getting at a few of the bottom nuts on these is bloody awful and made me want to throw a wrench across the room more than once.
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Finally just said "hell with it" and pulled the subframe with the control arms and steering rack attached. It's not as heavy as I feared, but was heavier than I'd hoped. Unfortunately I screwed up a couple of the balljoint boots trying to separate the control arms and tierods, and was pretty pissed about it. Ordered some generic silicone boots to replace them, still haven't done it.
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Finally the oilpan is exposed!
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Looked up at the guts. The oil pump needs to come out before the rods are accessible.
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Set up for bearing / bolt replacement:
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Art shot of one of the conrods, highlighting the split-cap construction (for the unaware: they're forged as single units, and then split with liquid Nitrogen to create the cap / rod separation. It means that each rod is unique, caps aren't interchangeable, and are also directional). The colour of the crank doesn't come through in this photo, it's a really lovely deep blue.
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Finally, the bearing shells that came out. Lots of copper showing there, I was very glad I decided to do the rod bearings. Spoiler alert: this was about 1/2 of what caused the build to go from mild to "I hate my wallet".
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Next day, I got serious about the top end, and things went sideways early on. I'd done the shims twice before, so wasn't surprised by most of the prep. But then I added a new entry on my "stuff to not forget" list:
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Of course, the nut being in the sump was literally the best-case scenario. It could have been anywhere along the cam chain channel, in the main timing gears... ugh.

Then, of course, I realized that the rocker shafts simply cannot come out of the head while (1) the head is in the car, or (2) the rad support is installed. I decided to pull the head, because I didn't want to pull the engine. Spoiler alert: that's the second half of the build derail. I used the DIY "back off each cam bearing cap nut 1/4 turn, in series, at a time" method for cam removal, and it went smoothly. Being way behind schedule, I totally bailed on building my own exhaust system behind the headers and ordered SuperSprint catless section 1, non-resonated X-pipe, and race cans.

Happy fun top end time:
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Pulling all of the VANOS bits:
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A small pile of take-offs, including a bag of 27 cam journal cap nuts
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Mostly-stripped head:


Stuff that came off:


The note I left myself at the end of the day:



So then I carried on to pulling the head off. It was pretty straightforward at that point.



The 28th nut:


This is where things got fun. Since the head was off, it didn't make any sense to me to put it back on without a refresh. A bit of research later, I ordered SuperTech valves / springs / retainers, and Achilles guides / seals, from the fine folks at Achilles. When I dropped them off at the machine shop (which, I found out, builds a tonne of Spec E46 and race S54 engines), they asked me about the rod bearings. I cheerfully explained that I'd done the Bimmerworld treated bearings and ARP rod bolts, so all was well. They responded by asking me a bunch of questions about things like roundness, clearances, bolt stretch, rod length, piston height... and I realized that I'd made a huge mistake.

Welp.

Since the block was coming out for a torque-plated 0.5mm overbore / rotating assembly balance / etc., I ordered Molnar rods, ARP main studs, VAC main bearings, JE +0.5mm pistons, VAC coated rod bearings, Clutch Masters aluminum flywheel, Clutch Masters FX300 clutch kit and mentally set the new engine's redline to 9,000RPM.

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The next time I think to myself "self, this would be easier if you just pulled the bloody engine out of this thing", I'm going to listen. Pulling the engine is honestly cleaner than dropping the front subframe to get at the bottom end, and it isn't that bad of a job with the Z4M's huge engine bay - even leaving the transmission in place.

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Next time I think the engine is going out the bottom, since I had to drop the front subframe to get it out without smashing the hell out of the oilpan (sigh).

At this point, things came fully unhinged. I ordered a Radium fuel rail (note! Despite claiming E85/E86 compatibility for their S54 kit, modification to either the kit or the Z4M's fuel system is required to use it), CSF aluminum radiator, Achilles power steering cooler, Setrab 650 (double stack 50-row) oil cooler, a bunch of -10AN fittings and hose, Earl's oil thermostat, Technica internal oil thermostat defeat, AEM X-Series oil / fuel pressure + oil / water temp + wideband AFR gauges, Moroso 1.5qt accumulator, EGR / heater core block-offs, and probably a bunch of other stuff I'm not thinking of right now. Sent the injectors off to RC to be cleaned and balanced. Only god and Visa know what else I spent on stuff for the car during that period of time.

Prepped the shortblock to go to the machine shop:
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There was coolant everywhere in the bottom end. Next time I pull it, it's coming out in one piece so I can be sure the water's out before cracking the head and dumping it into the oil passages / sump. Ugh.

Off to the shop:
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Some snaps of the shelves / floor around the shop at that time:
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Pulled the rest of the front end apart to make life easier for myself:
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Found more damage under the car than I'd expected / hoped:
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At this point, I learned that removing the engine and most of the nose of the car makes the distribution... not 50/50. I can lift the front of the car off of the front lift arms with one finger. Not great. Pretty spooky.

So then I got a shortblock and a ported / deshrouded head back from the machine shop:

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Assembled head:
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SuperTech springs / retainers / valves:
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Combustion chambers:
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New intake ports (phwoooooaaaaarrrrrr):
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Ported exhaust:
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Cleaning up parts to re-install:
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Re-installed the oil pump, pickup tubes, chain, and tensioner (yes, 25N-m and Loctite red):
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Did the VANOS re-seal / rattle repair:


..and this is nearly up to date. Next post: getting the Schrick cams installed on the bench to set the 0.25mm clearance specified by Schrick (spoiler alert: this is harder with stiffer valves and higher-duration cams), and to make sure that all of the shims are taller than the tops of the spring caps...
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      08-29-2017, 03:39 AM   #2
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That's one hell of a lot of work! Respect.

Are you glad you found out about the bearing particulars before you tried running the motor in? Annoying, but probably for the best.
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      08-29-2017, 04:21 AM   #3
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Wow, keep the posts coming brother!!!
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      08-29-2017, 06:03 AM   #4
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Damn. Putting it back together with shiny new parts will be fun though. At least I hope so. Interesting that you give the parts that piss you off the finger, I've done that a few times in my life too.....
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      08-29-2017, 07:35 AM   #5
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Wow!! Subscribed for the end result! Keep up the good work and you deserve tons of credit for doing this all yourself in your garage.
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      08-29-2017, 08:25 AM   #6
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      08-29-2017, 08:35 AM   #7
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Anti climax... there's no ruining going on here. You're taking better care of it compared to 99% of us.
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      08-29-2017, 09:47 AM   #8
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very very cool!!
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      08-29-2017, 10:00 AM   #9
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Quote:
Originally Posted by Finnegan View Post
That's one hell of a lot of work! Respect.

Are you glad you found out about the bearing particulars before you tried running the motor in? Annoying, but probably for the best.
Thanks! Yeah, I am incredibly glad. I actually asked the shop to measure how badly I'd gotten it by DIYing (and, to be clear, I did everything as close to correctly as possible per the FSM and ARP's instructions). The interesting thing to me is that according to the shop I used, anybody who has DIYed the rod bearings and doesn't own a bolt stretch gauge, didn't measure roundness of the rod big end with the new bearings / bolts, didn't appropriately clearance it, etc. is either really lucky or rapidly chewing through a set of rod bearings. The split-cap rods are apparently very strong, but virtually impossible to repeatably re-assemble perfectly due to the uneven rod-cap mating surfaces. I'd love to learn how to do all of the internals properly - but frankly, with the amount of money I have into this build, the labour to have it done by pro racing engine builders was rounding error, and then of course it led to... because racecar.
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      08-29-2017, 10:01 AM   #10
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Quote:
Originally Posted by pcube View Post
Anti climax... there's no ruining going on here. You're taking better care of it compared to 99% of us.
Heh. I meant "ruining" in the sense of "it will no longer be a pleasant thing to drive". I have a looooooooong and proud history of tuning cars and motorcycles to the point where they're absolutely fantastic at one thing, and completely miserable for literally everything else.

Pretty sure this is going to be one of them.

Pretty sure I'm alright with that.
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      08-29-2017, 10:08 AM   #11
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Quote:
Originally Posted by Z4M_GT3 View Post
Wow, keep the posts coming brother!!!
Quote:
Originally Posted by RABAUKE View Post
Damn. Putting it back together with shiny new parts will be fun though. At least I hope so. Interesting that you give the parts that piss you off the finger, I've done that a few times in my life too.....
Quote:
Originally Posted by Azeka1 View Post
Wow!! Subscribed for the end result! Keep up the good work and you deserve tons of credit for doing this all yourself in your garage.
Quote:
Originally Posted by deemo319 View Post
Quote:
Originally Posted by Beedub View Post
very very cool!!
Thanks, all. This isn't going to be done for awhile, but it should be a fun ride for everyone. Looking forward to fabricating a new rad support that can be removed with the bumper on the car, for example. And also fabbing all of the front-end aero to make the big coolers effective, while still getting cool air to the airbox, and also keeping enough closed vertical area to make the splitter effective...

Oh yeah. That reminds me: I ordered a set of the Trackspec Z4M hood louvers the other day. I wasn't sure how I was going to deal with underhood pressure, and then all of the sudden another Z4MC owner comments on one of my Instagram photos, and his car has this amazing hood that looks like exactly what I need! Of course I figured it was going to be some kind of $3,500 unobtanium piece - but nope, Trackspec, and they're ridiculously affordable for what appears to be very high-quality pieces. Win.
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      08-29-2017, 01:32 PM   #12
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Looking good mate, love the parts list, and love where this build is headed.

Subbed for more awesomeness..
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      08-29-2017, 04:42 PM   #13
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Fantastic build, but serious question(s)

What will the car be used for

And why did you make the decision that you did for some of the parts?
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      08-29-2017, 06:22 PM   #14
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Quote:
Originally Posted by TheAxiom View Post
Fantastic build, but serious question(s)

What will the car be used for

And why did you make the decision that you did for some of the parts?
The car has predominantly been track use for the past year and a half, but I've been driving it to and from events. This is basically cementing "off road" as the only thing it will be used for, and getting there / back on a trailer. If this had started as a full track build, I'd have prioritized some other things first - interior / safety / etc. - since it has become a full track build because of the "while I'm in there" engine stuff, I'll be dealing with cage / interior / seats / harnesses / etc. next.

Which parts are you curious about? Happy to share my thinking about specifics (or groups of things), but it would be a lot of work to go through and explain every item
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      08-30-2017, 01:27 PM   #15
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This indeed sounds very expensive, and I recommend you start a plan right away to recoup some of the costs by selling me your entire Sepang interior with all the extended leather bits. I just want to help you. ;-)
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      08-30-2017, 03:29 PM   #16
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Quote:
Originally Posted by DanFromTucson View Post
This indeed sounds very expensive, and I recommend you start a plan right away to recoup some of the costs by selling me your entire Sepang interior with all the extended leather bits. I just want to help you. ;-)
Your advice seems sound. Make me an offer I can't refuse.
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      08-30-2017, 05:02 PM   #17
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No! Sell it to me!
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      08-30-2017, 09:43 PM   #18
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Damn - great work! My 2JZ swap was surely a breeze compared to what you're going through. Much respect.

I like the build comments and photos, reminds me of my build thread in many respects. If you run into odd ball issues or want to bounce some ideas, PM me!

Also, why that Setrab cooler? I went with a CSF long bottom mount unit on mine, which gets you the advantage of frontal airflow for cooling right beneath the radiator, not blocking anything else. Better than trying to place a cooler now in front of your radiator, or worse, to the side. Then again, you don't have a huge front mount like I do, with an AC condenser sandwhiched between lol.

I also looked at hood louvers, but my car sees road duty often, and rain/washing my car would just sour my day.

Interested to see what power you make when all is said and done!
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      08-31-2017, 02:43 AM   #19
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Quote:
Originally Posted by wdb View Post
No! Sell it to me!
Something, something, offer I can't refuse? Seriously, if somebody wants the interior out of this car, make me an offer. It's coming out at some point anyway, and if it'll help pay for the cage, harnesses, seats, etc. I might as well do it now.

Quote:
Originally Posted by dre99gsx View Post
Damn - great work! My 2JZ swap was surely a breeze compared to what you're going through. Much respect.

I like the build comments and photos, reminds me of my build thread in many respects. If you run into odd ball issues or want to bounce some ideas, PM me!

Also, why that Setrab cooler? I went with a CSF long bottom mount unit on mine, which gets you the advantage of frontal airflow for cooling right beneath the radiator, not blocking anything else. Better than trying to place a cooler now in front of your radiator, or worse, to the side. Then again, you don't have a huge front mount like I do, with an AC condenser sandwhiched between lol.

I also looked at hood louvers, but my car sees road duty often, and rain/washing my car would just sour my day.

Interested to see what power you make when all is said and done!
Thanks man! I sincerely doubt that this is anywhere near 2JZ swap territory as far as weirdness or complexity is concerned, but I also appreciate the props. I will definitely PM you with any questions - sure does look like you went down a similar road so far as taking the whole damn car apart is concerned.

I picked the Setrab 650 because it has the lowest (or second-lowest, can't remember) pressure drop of their 6-series line, and has enough surface area that I should never need to worry about oil temp. The huge cooler is the reason for the Earl's oil cooler thermostat - I don't want to over-cool it. I honestly don't know if this is stupidly oversized or not, but over-engineering the oil system on a race engine never hurt (see also: the Moroso oil accumulator). I didn't want the E46 / E86 style cooler because they have pretty significant pressure drop - like 6-11 PSI if memory serves (fake edit: ECS says that the CSF E46 M3 oil cooler has a 10 PSI pressure drop) - versus the 1.8 PSI drop Setrab claims for the 650. Since I have to redo all of the airflow management in the nose of the car anyway - and I'm deleting the A/C, because I hate myself - I figure I can sort out the water and oil radiators in a way that will be reasonable. And yeah, no intercooler either. Just oil and water.

Since I'm doing airflow management on the front end, I should be able to manufacture some air pressure over the splitter, which will pressurize the underhood area pretty badly if I don't let it out somewhere. I don't want it under the car (lift BAD, downforce GOOD) so louvres it is. Plus I think they look awesome.

I am hoping to be in the 370-400WHP range when all is said and done. We shall see. Similar builds are in this territory, but of course a lot of it comes down to the porting and tuning. Since I'm running the stock ECM and have their airbox, I'm working with Evolve in the UK - they're pretty bullish about how their tune is going to work with this setup. Should be some interesting dyno sessions!
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      09-01-2017, 08:47 AM   #20
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Quote:
Originally Posted by mattfwalters View Post
The car has predominantly been track use for the past year and a half, but I've been driving it to and from events. This is basically cementing "off road" as the only thing it will be used for, and getting there / back on a trailer. If this had started as a full track build, I'd have prioritized some other things first - interior / safety / etc. - since it has become a full track build because of the "while I'm in there" engine stuff, I'll be dealing with cage / interior / seats / harnesses / etc. next.

Which parts are you curious about? Happy to share my thinking about specifics (or groups of things), but it would be a lot of work to go through and explain every item
Cams, head work, Headers?
Like why you went 288* vs 272*?

Suspension?

I'm just curious (seriously) on what made you pursue those options?
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      09-01-2017, 11:20 PM   #21
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Quote:
Originally Posted by TheAxiom View Post
Cams, head work, Headers?
Like why you went 288* vs 272*?

Suspension?

I'm just curious (seriously) on what made you pursue those options?
Headers: I've had the headers for awhile (like 3 years) - bought them because cheap power - and had been planning to install them with the rest of the bits since they were around and I had to tune the ECU anyway with the Evolve airbox install (a good time to code out the front O2 sensors). Bought the Evolve because 20+ horsepower and oh my god that noise

Suspension: I wanted to fit the the widest front tires I could under the fenders and have a fat square wheel setup (because being able to rotate front-to-back and keep only one width of spare wheel around seemed very convenient, and I really wanted to dial out the understeer as much as possible), and built a very nerdy spreadsheet to calculate what combination of offset, wheel / tire width, spacers, and camber would be required to make it happen. Ended up with the APEX setup (EC-7 18x9.5" ET35 w/12mm spacers in the rear; stud conversion). Converted to studs because changing wheels trackside without studs sucks. Math said I needed around -2.5 degrees of camber to tuck the fronts under the fenders, so I knew I needed camber plates. Didn't want to just put camber plates on the stock suspension, knew I wanted coilovers to properly corner-balance the car and set ride height, found the Ground Control setup, researched it, found a bunch of folks tracking cars with them and very happy, called GC and talked about my goals for the car and they recommended the 550 / 700 setup with rear sway delete to keep the car neutral while cornering but to provide more rear grip coming out of corners. We talked for awhile, it's clear they know their BMWs, I bought them for half the price of the KW v3s, and they've been amazing for the car on the track. At this time, bear in mind, the car was intended to be dual-use and also a mild / relatively inexpensive build. I've been ridiculously happy with the GC suspension.

Cams: picked the 280s because they're the most aggressive N/A cams recommended for street use, and the combination of the CSL-style airbox and big duration cams (1) sounds f___ing amazing, and (2) makes very good power over a broader range, with a good mid-range torque bump. Still meant to be a relatively mild street / track day car at this time.

Headwork: talked about this a bit in the first post, but generally, once I had to take the head off, it didn't make sense to re-install it with 81k km on it. I almost always follow the "upgrade rather than replace" policy - especially with this car, where hop-up parts are way cheaper than OEM, so I looked into what would be necessary to bump the redline a bit, and what were generally the best-regarded top-end internals by endurance racing folks. I ended up on the phone with the folks at Achilles for awhile, chatting about options (including considering +1mm valves / VANOS delete - Minos' suggestion was "keep VANOS. Delete it when you really hate your wallet"), and settling on the SuperTech setup with steel retainers, since Ti retainers crack much more easily. He, again, clearly knew his stuff, and shared a lot of learnings from racing / customers who race without even a hint of hesitation. So I looked around for a machine shop / engine builder nearby, found the shop that builds Spec E46 and race S54 engines, and brought everything in to them. They recommended the headwork based on significant experience building motors for racing BMWs, I checked with Achilles and they agreed with the recommendations, so that's what I did. This is when the conversation about rod bearing clearance / rod big end roundness / etc. happened and I decided to have experts deal with the bottom end. Molnar rods were recommended by several endurance racing folks as excellent for RPM and durability (I'm staying N/A so don't need turbo internals), and if I'm replacing the rods, doesn't make any sense to leave the pistons. And this is pretty much where the wheels came off and it turned into a "damn the torpedoes" track build.
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      09-02-2017, 11:15 AM   #22
yousefnjr
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Well that ramped up fast lol. Looks like a lot of fun, great thread. Looking forward to your thoughts on the cams when all is done, and videos of this 9k rpm banshee
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