heinzboehmer's 2002 Topaz 6MT Coupe

[heinzboehmer]

Wow, can’t believe you even had dust in there!

It got eeeeverywhere, it was crazy.

[Arclitgold]

Wow, can’t believe you even had dust in there!

[heinzboehmer]

Well, had to tackle another unplanned side project today.

Drove the car in the rain for the first time in a while and quickly learned that my windshield wiper stalk was not working correctly. The only setting that worked was the full blast intermittent one. Fortunately, I could flick it up and down quickly to trigger a single wipe, but having to do that for the entire drive got old pretty quick.

I did take the stalk apart to clean the dust out of it from my little track adventure, so must have not put it back together properly.

First, a quick overview of how the stalk works:

There are two perpendicular "tracks" on the circuit board that two separate wipers (think potentiometer wipers, not windshield wipers) "ride" on. One track is for up/down stalk movement and the other for in/out. Depending on the position of the stalk, the wipers connect different traces together, which sends out the appropriate signal to the LSZ (GM5? I forget where the wiper logic lives).

What's really cool is that wiper movement along the tracks is continuous and the mechanical detents for the stalk are completely decoupled from the electronics bits. Guessing this separation is why the action on these things feels so good. Can tune the feel without affecting the electronic characteristics.

A picture should help explain what this all means:



Housing parts:

A - Up/Down wiper riding on its track
B - In/Out wiper riding on its track (you can also see the linkage that transforms in/out stalk movement to left/right wiper movement)
C - Header for dial wheel (and "S" button)
D - Detent plate to discretize stalk movement (basically just a section of a hemisphere with a bunch of divots in it)

Stalk parts

A - Pin that moves Up/Down wiper
B - Lever that moves In/Out wiper (hard to see, but it's L shaped from the side)
C - Connector for dial wheel (and "S" button)
D - "Stylus" that follows detent plate

As you can imagine, this thing is a bit finicky to get back together, since have to make sure that the features that interface with both wipers are in their correct spots. The image above shows how I found the stalk when I took it apart. Close inspection revealed that the Up/Down pin was not sitting correctly in the wiper, which made the stalk work unexpectedly.

Took a couple tries, but managed to get it back together correctly. Probably could have avoided this if I had tested the stalk after I first took it apart, but oh well.

On the upside, I'm getting reeeally good at taking the steering wheel off. Can do it in a couple minutes now

[heinzboehmer]

Quick side project.

I had previously tried to fix the tab that's under the light on one of my C pillar covers by just gluing it back together, but the repair didn't stick:



So I came up with this:




A three piece replacement that mechanically interfaces with the remaining parts of the tab, so that it doesn't have to rely on the adhesive for strength. Chose ABS-GF for this and managed to print with no supports by setting the layer height to 0.08mm. Overhangs came out great.

You can see how the three pieces lock together against the remaining material in this cutaway:



To install, you need to trim the remaining plastic, mark out the location of the notches, then cut those bits away:





A bit more involved than just gluing the piece on, but it results in a super solid mechanical interface.

Here's an impact driver hanging from the replacement tab. Note that there is no adhesive present here:



In hindsight, running the above test was kinda dumb. If it failed, I would have had to source another pillar cover. It survived though, so we're good

For the final install, I did add a bit of epoxy in between the replacement tab and the pillar cover, for max strength. Seems to have worked out great!

[heinzboehmer]

Check your toe

I see road force balancing (RFB) more as a diagnostic tool than something I would routinely do. I used RFB to determine how out of round a wheel was - can't always see it on a dynamic balancer or if the tire was bad (it happens). I never saw a situation where a RFB fixed a vibration issue where a dynamic balance couldn't. In some cases, a RFB made noise and vibration worse. Whoever is mounting a new tire needs to understanding the markings on the side of the tire to orient the high point of the tire with the valve stem which typically optimizes the balance.

IMO, RFB as a routine is the nitrogen of tire balancing - mostly useless, makes the shop more money, and is often "flat rated" by techs. Meaning they say they did it...but didn't do it.

That makes sense.

Due for an alignment soon, we'll see what the front is at. I always go with 0 toe up front, so not the best for tire wear.

[bigjae46]

Fine, guess I'll swap them out for a new set of PS4Ss. Gave the mobile tire guy who's always at the track a call and he swapped tires for me in my driveway. Not having to stuff a bunch of tires into a car and then drive to the tire shop was truly the ultimate luxury, don't think I can go back.

Check your toe

I see road force balancing (RFB) more as a diagnostic tool than something I would routinely do. I used RFB to determine how out of round a wheel was - can't always see it on a dynamic balancer or if the tire was bad (it happens). I never saw a situation where a RFB fixed a vibration issue where a dynamic balance couldn't. In some cases, a RFB made noise and vibration worse. Whoever is mounting a new tire needs to understanding the markings on the side of the tire to orient the high point of the tire with the valve stem which typically optimizes the balance.

IMO, RFB as a routine is the nitrogen of tire balancing - mostly useless, makes the shop more money, and is often "flat rated" by techs. Meaning they say they did it...but didn't do it.

[heinzboehmer]

I've been trying to learn a bit more about air filtration to help interpret my experimental results, but the only thing that has become clear to me is that I have not controlled for nowhere near enough variables to adequately characterize each filter. However, I think we can get an idea of how the system is behaving as a whole.

Let's start with the static pressure data. Experimental setup stayed the same as what I described 30 or so posts back and the data is the average of three measurements. Also worth noting that all filters used in the tests were brand new.

Setup	Differential Pressure (Pa)
Stock Housing + Plug, No Filter	53
Stock Housing + Plug, Stock Filter	80
Modified Housing + Plug, No Filters	73
Modified Housing + Plug, F25 Filters	84

I think we can really only make three observations from this data:

1. Both housings flow worse with filters installed. This is expected and just a sanity check, as any filter will impede flow to an extent.
2. With no filters installed, the modified parts flow worse than the stock parts. This is also expected, as the total opening for the filters in the modified housing is smaller than stock.
3. With filters installed, the modified parts also flow worse than the stock parts, but by a much smaller margin.

The last observation is the interesting one and it's where I think drawing conclusions about the filter properties is not straight forward. Although differential pressure (and thus, flow rate) is very similar between the modified and stock parts, this does not necessarily mean that the filtration efficiency is the same. One possible explanation for the numbers being close is that the filter material in the F25 filters is less dense (driving both differential pressure and filtration efficiency down + flow rate up), but the decrease in area of the housing openings balances this out.

What's tripping me out a bit is that all of the dimensions are different between the stock and F25 filters. F25 filters are significantly taller, so even though their footprint is about 45% that of stock, the total filter surface area is closer. I can probably estimate what the total area is for both filters by counting the pleats and doing a bit of math, but I'm not sure I'm gonna get anywhere with that. I still won't really know how the differential pressure of each filter material compares, since the housing geometry is completely different between the two versions. The only way I can think of accurately measuring this is to cut up both filters, flatten out the material and then run a similar pressure experiment with some bench setup that only flows air through a fixed area. As curious as I am, I don't really think this is a good use of my time/money, as the real world effects are likely gonna be indistinguishable between the two setups.

I think the only thing that (3) tells us is that the power required to move air from outside the car, through the filters and into the cabin, is roughly the same between both setups.

But, actually, I'm okay with that. The system is still operating well within the bounds it was designed for and the only potential downside is that a bit more dust will get into the cabin. Totally happy making that tradeoff considering the massive difference in driving experience that the bracing provides.

[heinzboehmer]

🤣

M3 is shockingly practical. Was my only car the first 10
years I owned it. Got work done!

It really is! Was my only car the first 5 years I owned it. Took me skiing a million times, moved me a couple times (including one cross country move) and served as a daily for a couple years. Good stuff.

[Obioban]

Fine, you guys have convinced me. Next time I'll take the F1 to the tile store.

🤣

M3 is shockingly practical. Was my only car the first 10
years I owned it. Got work done!

[heinzboehmer]

Fine, you guys have convinced me. Next time I'll take the F1 to the tile store.

[Obioban]

^ You couldn't do that in a McF1

McF1 has way more space than you'd expect in those side pods.

[Slideways]

^ You couldn't do that in a McF1

[heinzboehmer]

Man, I love this thing. Just a few weeks ago, it was flying off the racetrack and today it hauled a bunch of tile for a bathroom remodel (with working cabin air filtration!).



Who knew that throwing a couple hundred pounds of tile into the trunk was all you needed to prep the car for instagram fame?



What a good car.

[heinzboehmer]

Wow bracing and cabin air filter housing looks absolutely OEM, truly an amazing job!! I think I know what the next project will be after finishing the engine swap in the E30

Hell yeah! Would be super cool to see these parts on other cars.

[PipeUy]

Wow bracing and cabin air filter housing looks absolutely OEM, truly an amazing job!! I think I know what the next project will be after finishing the engine swap in the E30