STR Z4 Coupe "build"

[John V]

What Jay said. You don't need a new crush sleeve. Mark the nut and reinstall where it was. If you understand the function of the crush sleeve you'll understand that this will maintain the exact pinion preload you have now.

Yes, you'll need new seals. That's a small price to pay compared to destroying a diff.

I'm not sure what you mean by "tolerance." I have four E46 diffs disassembled here. The difference between the thickest and thinnest pairs of shims installed in them is more than 2.5mm. That should tell you something.

[illinipo]

I still can't believe the deal we got on these.



wassup61 should be here in about 3 hours so get your modems ready for a huge pic bomb all weekend

Fri 7:50p: gahhhhhhh can NOT remove the shift coupler pin to change out the sponge. Rusted in there. And there is just not enough room to hammer it up or down. So, we are going to leave it for now and take care of it when the trans comes down for the clutch eventually...

Fri 9:42p:

Heeeerre weeee go



Filled the rear shifter bushing with that Loctite PL roofing urethane at the bottom of the table which cures to about 27A hardness.

Never got around to the exhaust stud. Will get it tonight.



Shifter parts.



Sat 2:20a:

Just this part alone made a HUGE difference in shifter play.



Getting ready for bushings. (SVT Focus head with bent valves in background, if you were wondering)



Fortunately they were a good fit so no need for the press tool. Some careful and convincing blows did the trick.



Cleaning the mating surface on the diff.



Always be sure to wear gloves when filling your differential with antifreeze.





Time for some goo



Torquing it up



More goo



Prepping the subframe. Making sure to set the bushing preload close to zero in the middle, little bit low on the travel.





And done.



We started on the CSB but wassup61 got tired so we stopped.

[illinipo]

Sat. 6:22p

[BTM]

Thanks for having me pete, glad you were able to make some good progress despite me getting in the way all weekend

[illinipo]

Nonsense, you were a huge help for like 90% of the time lol

Plus I'm glad you got going on the shock adjuster extenders. I wouldn't have got around to it myself.

Two more pics, and the weekend is done.

Gotta lube the shaft.



Found: Bottom half of wassup61. In search of top half. Please contact by PM if located.

[Dubbedown]

This is now on my favorites link! To think there's actually a purpose built e86 n52 in-progress. Up to now, I thought my 3.0si with off-the-shelf mods was the most "modded"... really appreciate all the info you poured in here! Too bad there's no track halfway between us where we could do a DE together =)

[illinipo]

Planning on hitting the Toledo ProSolo if you really want to see how you stack up

[illinipo]

Subframe and suspension are installed. Less springs and shocks... 3-4 more weeks for 4150's.

Tomorrow it's giubo, CSB, diff connection. Bolt up exhaust (may need to finesse the stud hole) and heat shielding. Then the car will hit the ground for the first time in almost 4 months...

May or may not get started on the BW mounts. The bolts that hold the front chassis bracing need to be replaced and are supposedly on national backorder... We can't really start that job without the new bolts on hand.

Saturday 1519

Driveshaft is in, e-brake adjusted, heat shield is in. Time to lift the exhaust into place.

Almost there!

Sat 2231

She put up a fight... but the exhaust is in. Questionable whether it will leak or not. The rust is so bad, I did not want to use a ratchet to get the nuts on because it would have broke another stud for sure. So, I had to use an impact to get the nuts on... And I didn't want to overdo it and strip the threads off the studs. I think it is tight but it was still spinning pretty freely. So we'll see.

Because of a few things that went wrong, we decided to get the car up on all 4 jack points instead of dropping it for the BW mount install. So that is done, car will not hit the ground for at least another month and we are ready to go on that.



Does anyone know what is STR legal in terms of trans mounts?

[murph1379]

The current rule on the trans mount is that it can't contain any more metal than stock. The proposed new rule is that it can't be any lighter than stock.

[illinipo]

so... time for solid mounts?

What I meant was, which brands are legal?

We are looking at UUC gen2 reds.

[John V]

Very little reason to use anything other than the stock transmission mounts. They're plenty stiff.

[Prodigal_M]

Very little reason to use anything other than the stock transmission mounts. They're plenty stiff.

Yes, compared to spaghetti they are quite stiff on the Z4

[BTM]

Very little reason to use anything other than the stock transmission mounts. They're plenty stiff.

Beg to differ...upgrading trans mounts made a huge different on my car. The Z4 transmission is notoriously notchy, esp 1-2 upshift under a lateral load. Upgrading mounts makes it a big improvement. It's much more pronounced on the M (due to the engine/trans mismatch) but I've driven this car and I think harder mounts are a good idea

[wassup61]

I would have to agree with john v. He's done 4 e46 mounts and found stock is best. Listen to the expert bro.

[John V]

I have stiffer mounts in my DSP car but I really don't think they do much when you already have solid motor mounts.

Are the Z4 mounts softer than regular E46 mounts?

[illinipo]

Special thanks to Jason (modernbeat) and AJ (sn unknown?) at Vorshlag for showing me around yesterday. I could tell you guys were really short handed but still took the time to give the tour Thanks!

Got decent news about the shocks that I'm not sure if I can divulge... But let's just say it is frustrating that us 'Mericuns love our muscle cars so much that the Mustang and Camaro shocks go into production first

Front brace should be coming out this weekend in preparation for motor mounts. Depending on the ease of install after the brace is down, I might just do the mounts and get it over with...

After that all that's left are trans mounts and AST's. I also still need to plot the camber curves and fix my one broken scale pad, which will be done tomorrow in preparation for BTM's BSP ///////M coupe.

[illinipo]

Modded my garage tonight. because racegaragewhiteboard



Got the trans mounts in. The N52 exhaust makes this job 10 times harder than it needs to be.



And here are the endlinks that came on the 21.5mm front bar I got from JBracer. After some disassembly by wassup61 of course.



And finally, more broken parts to replace. My records show these were bought in early July last year. That means these Powerflex FCAB lasted a whopping 5,000 miles and about 60 autocross runs.





Pretty sure we are going AKG this time.

[BTM]

Modded my garage tonight. because racegaragewhiteboard

OMG...no way. I don't believe my eyes

[illinipo]

No kidding lol. Now I just need a reason to use it.

I finally got around to measuring the weight reduction by going with stiff spring / small bar setup. It is not insignificant.

25mm front bar with bushings 12.4lb
21.5mm front bar with bushings 9.8lb
19mm rear bar with bushings, mounts, and brackets 7.4lb

Total weight savings, about 10lbs.


Still kicking myself that I forgot to weigh the open diff and wavetrac without the ring gear...

[BTM]

we could use it for camber plate comparisons...u get the scale fixed?

[illinipo]

Well, there is a temporary solution installed but I would like to take a bit more time/money/parts to improve it.

729p...
Bimmerworld engine mounts installed... was almost too easy.

New remaining work list:

Mount new rubbers
Buy and install AKG FCAB
Oil change
Install rear chassis brace
Install front chassis brace and undertrays
Remove front suspension
Take delivery of the suspension that was paid for 4 months ago but still hasn't been built by AST
Install said suspension
Build and install shock adjuster extenders
Determine desired ride height from camber curves and consider bump steer
Corner balance on my epic deal race scales
Do alignment
Study shock dynos to determine desired knob adjustment settings for various springs
Bleed brakes
Button up interior trim
Hooning/operations check

[illinipo]

Had a long day at work including a major F up. So I needed to cool off in the shop.




Those PVC bushings and adapters have been priceless throughout this build. Best $5 I ever spent on a tool, seriously.

Anyway, the lollipops are empty and the AKG 75D bushings will be here momentarily.


I also measured the swaybars and used the Puhn method of estimating effective spring rate. He uses the torsional stiffness of the middle part and bending stiffness of the ends, and doubles the end deflection in the analysis like Matt Murphy did. Using the 0.554 rear and 0.861 front motion ratios I determined for the bars, I end up with the following effective wheel rates:

19mm rear bar 436 lb/in
21.5mm front bar 1212 lb/in
25mm front bar 2261 lb/in


Now, I'm not yet sure I fully buy into this effective spring rate stuff. That is a big number and I have read threads where guys will go from 650 springs with 19mm rear bar to 750 or 800 and no bar, and have no net change in handling. That means they supposedly dropped 436 lb/in of bar wheel rate and picked up about 75-100 lb/in of spring wheel rate. A 350 lb/in change in wheel rate with no effect on handling? It's not looking good for this type of analysis of swaybars.

I would prefer to measure the overall torsional stiffness about the roll axis (in lb*in/degree) and use that in Milliken's method (http://www.optimumg.com/docs/Springs...Tech_Tip_2.pdf). That way I can directly put the number in my roll gradient model without these silly "effective wheel rate" assumptions and calculations. Might get crafty this summer and build a rig with my scales. In the meantime, I'm gonna do some geometry and other maths to develop my own equation for lb*in/deg for the bars I have. Stay tuned for that I guess. It's late, I'm tired, and I have to fix what I broke at work tomorrow.


In any case. I'm in the market for 60mm springs, if anyone has a pile they want to get rid of.

[murph1379]

Yeah I hear ya on being a little skeptical of the numbers the calculators put out on the bars, which is why I was attempting the measurement project. Still have some thoughts on working on that with another guy locally, but also getting rather busy with autocross season here. Did you remember to square the motion ratio to use as the wheel rate multiplier?

The article you posted is interesting, but he seems to calculate MR opposite of how I've seen it done in other places. (he asks how much the wheel moves for each inch of spring or bar movement, others ask how much spring or bar movement for each inch of wheel movement) He also explains the equations of how to calculate things, but not a very good idea of what a desirable end result should look like.

Looking forward to hearing more about your work in calculating the lb*in/deg info.

[illinipo]

Here is my quick spreadsheet for the Puhn calculations. Remove the second dot because bfc doesnt allow tinyurl links i guess.

http://tinyurl..com/7bnyrlx

The article you posted is interesting, but he seems to calculate MR opposite of how I've seen it done in other places. (he asks how much the wheel moves for each inch of spring or bar movement, others ask how much spring or bar movement for each inch of wheel movement) He also explains the equations of how to calculate things, but not a very good idea of what a desirable end result should look like.

Looking forward to hearing more about your work in calculating the lb*in/deg info.

He does do MR backwards, but this is taken care of later on when he says wheel rate is spring rate / MR^2. Even the first equation has it as Ks/MR^2.

Does not provide an end result because the Optimum G program is designed for helping out a student competition (FSAE) so the numbers may be all over the place and he doesn't want to give it away. Especially when you compare an FSAE car to, say, Vorshlag's beast of an STX car (now ESP), the numbers will be way different.

If you want to try some things out, shoot for a ride frequency around 2-2.5 and a roll gradient of about 1.5-2 for street tires on a passenger sedan. There is more about this on the internet.

[murph1379]

If you want to try some things out, shoot for a ride frequency around 2-2.5 and a roll gradient of about 1.5-2 for street tires on a passenger sedan. There is more about this on the internet.

Great info, thanks! I'm at about 2.5 NF on both ends, and have been sorta estimating something like roll gradient based on the amount of travel I'd get if all 1400ish lbs of my front sprung mass were transferred to the outside wheel. That doesn't necessarily tell me how much the car will roll, but I've found that to be difficult to determine, because I can't really find the roll center.