heinzboehmer's 2002 Topaz 6MT Coupe

[D-O]

Very well done sir.

[heinzboehmer]

Thanks! I'm pretty happy with how the project came out

[YoitsTmac]

Looks great! Whose intake snorkel is that? I'm looking for a plastic OEM-style one

[heinzboehmer]

Looks great! Whose intake snorkel is that? I'm looking for a plastic OEM-style one

Karbonius snorkel that I had cerakoted. I think Haimus makes one that fits and is plastic?

[heinzboehmer]

Also, some (long) thoughts and a photo dump at the end:

It's been interesting driving the car with the braces and snorkel back on. It's both more and less refined.

The thing that I kept being drawn to this time around is the H in NVH. The car isn't harsher as a whole, but the qualities of the harshness for sure change.

If you imagine plotting the impacts that the driver feels inside the car, the amplitudes would stay the same, regardless of bracing, BUT the shape of the waveform would be very different. Unbraced would be sinusoidal, while braced would be much more triangle-like. In other words, the unbraced chassis extends the duration of the harshness, but softens the transitions, while the braced chassis both absorbs and gets the harshness out of the way much quicker. In qualitative terms, the bracing makes the car feel more "sporty" and less "relaxed". Think this is similar to what Bryson was talking about when comparing it to a spring rate change.

The one exception to this is the steering wheel. The feedback you get through there is for sure harsher, period. Makes sense since, for a given impact: less strut tower deflection -> less energy absorbed by flexing the strut towers -> more energy going into the steering rack -> harsher "jolts" of the wheel in your hands. This is not at all an unwelcome change, though! Makes the front end feel way more precise and again, "sporty".

On throttle, mid corner behavior is still the best part of this mod for me. You give it steering input and the front keeps turning at the same radius, regardless of the amount of throttle applied. It's very fun.

Counterpoint to that is that the front end is significantly less forgiving of imprecise inputs. I didn't even realize I had learned this behavior, but turns out I was using the unbraced, throttle induced understeer to aid in small direction changes. Simplest example that comes to mind is giving it only a little bit of steering angle on the highway to change lanes, then giving it throttle to speed up and letting the understeering front end carry you over to the other lane. If I go to do that with the braced chassis, the car just keeps pointing where I told it to point with my hands. Again, not something I mind because of the more sporty nature of the car, but still something worth pointing out.

The braced chassis demands more attention from the driver in most situations, and especially if you want to be smooth. As mentioned above, it's less forgiving to imprecision.


Onto the snorkel:

This change was immediately obvious: less snorkel, more rowdiness. It's not louder, but the overtones in the noise are slightly higher pitched, which makes it feel louder.

And this isn't just subjective! I have data to prove it.

First, a comparison of the waveforms of a pull from 3k to 8k rpm (same on ramp, similar weather, mic in the same spot, both WOT). Note that the amplitude is basically the same between both.

No snorkel:



Snorkel:



And here's a spectrogram comparison of the same clips.

No snorkel:



Snorkel:



The difference is very obvious in the spectrograms. Notice how much more higher the frequencies are pushed without the snorkel. With the snorkel, they're all bunched up in the low end.

Cool to see, but I think I'll be keeping the snorkel for the sake of those IATs

(also worth noting that this is with the cerakoted snorkel. I'm not sure how much the coating affects the sound, but it sounds pretty similar to what I remember the uncoated snorkel sounding like. I wish I had captured audio of that combo as well, just to know for sure)



Anyway, too much talking. Ending this one with some much better engine bay pictures, in a couple different lighting scenarios.:

[Slideways]

Both brace and snorkel turned out amazing with the cerakote!

The snorkel might need a sticker delete

[heinzboehmer]

Both brace and snorkel turned out amazing with the cerakote!

The snorkel might need a sticker delete

Yeah, sticker is pretty unsightly. I asked for it to get masked cause it has manufacturing info on it, buut all of that came off when unmasking.

Which means that if I do remove it, I have to figure out how to blend the overspray with the raw carbon under the sticker. Soooo I've just been ignoring it.

[George Hill]

My Z4 braces just showed up

And the brace looks sooo good, but that snorkel being cerakoted vs CF is the chefs kiss IMO.

[heinzboehmer]

Unfortunately, when parking back in said garage, I noticed a faint oil smell. Popped the hood and immediately saw this:


...

Timing chain tensioner is drenched:



The boss on the head that it threads into is drenched as well though, so it seems like the oil is coming from higher up.

Coming back to this.

Have been driving the car around and keeping an eye on this leak. I've yet to see it leak any more and have not smelled any oil since I first noticed it.

I only noticed the smell after a track day, so I'm starting to suspect that the second half of the last sentence in the quote above is incorrect.

I'm guessing that what actually happened was that the tensioner had a small leak and the oil got flung around due to the g forces on track. Some made it onto (or close) to the exhaust manifolds (hence smell), some made it onto the tensioner boss on the head and some made it all the way to the water pump pulley (hence the oil trail near the belts).

So, plan is to replace the tensioner crush washer with an annealed one (thanks maupineda for the suggestion!) and go from there. Maybe this will end up being an easy fix?

[D-O]

Coming back to this.

Have been driving the car around and keeping an eye on this leak. I've yet to see it leak any more and have not smelled any oil since I first noticed it.

I only noticed the smell after a track day, so I'm starting to suspect that the second half of the last sentence in the quote above is incorrect.

I'm guessing that what actually happened was that the tensioner had a small leak and the oil got flung around due to the g forces on track. Some made it onto (or close) to the exhaust manifolds (hence smell), some made it onto the tensioner boss on the head and some made it all the way to the water pump pulley (hence the oil trail near the belts).

So, plan is to replace the tensioner crush washer with an annealed one (thanks maupineda for the suggestion!) and go from there. Maybe this will end up being an easy fix?

Hopefully you will be luckier than I was. Wet in the same spots, but my leak turned out to be the VANOS gasket.

[heinzboehmer]

Hopefully you will be luckier than I was. Wet in the same spots, but my leak turned out to be the VANOS gasket.

I hope so too!

I've swapped that gasket out too many times now chasing leaks. Think what finally solved it for me was a timesert on the upper right corner of the head. Guessing the original threads were slowly failing and causing the bolt to lose clamping force.

I just poked around there with a mirror and it looks dry. Seems like that gasket isn't the cause of the leak, but it's fairly hard to tell without removing more stuff.

[heinzboehmer]

Swapped out the crush washer for an annealed one and did a bit of science while I was at it. I had 15+ of these things in the stash, so more than enough to mess around with.

First, let's document the annealing process.

I hung the crush washer from a bent paper clip and used a propane torch to heat it up (was afraid MAPP would pretty much immediately melt it), then quickly quenched it in some room temp water.

My first attempt involved trying to judge temperature by eye and resulted in this:



So, for my next attempt, I scribbled with a sharpie on one side of the part (as can be seen above) and hit it with the torch from the non-sharpied side. Once all the sharpie disappeared (i.e. part had heated all the way through), I quenched it in the water.

Supposedly, sharpie ink disappears right around the annealing temp for aluminum, which is why it can be used as a temp indicator. Can't remember where I learned this trick, but thank you brain for stashing that bit of info away.

This method worked significantly more reliably.

Subjectively, a stock crush washer felt harder than the annealed one when scratched with a metal pick. The annealed one also felt way more "clay-like" when torquing the tensioner, almost as if it was "smearing" more. The difference was subtle and it's hard to draw any real conclusions from a subjective account, so, I decided to collect some data.

Here's an overview of the experiment:

1. Measure thickness of crush washer pre-torquing.
2. Torque tensioner along with above crush washer on spare engine to factory spec. Spare engine is used here so that torque wrench is on straight and the procedure is repeatable.
3. Measure thickness of crush washer post-torquing.

I also found a crush washer stuck on the head of the spare engine, so I measured that one + the leaky one that came off the car for some extra data.

Some givens/assumptions before diving into the data:

• I assessed four different "versions" of the same part:
  • A new stock crush washer (1)
  • A new crush washer that I annealed (2)
  • The crush washer that came off the car (3)
  • The crush washer that I found on the spare engine (4)
• (1), (2) and (3) were all purchased at the same time. I placed an order for ~20 a couple years back, so it's highly likely that they were all produced at the same time, in the same factory, from the same material, etc.
• (4) has a completely unknown history. It's highly unlikely that it's from the same batch as the others.
• (3) was torqued by me following the BMW spec.
• (4) was torqued by someone else to some unknown value.
• Pre-torque thickness of both (3) and (4) are unknown. Since (3) is likely from the same batch as (1) and (2), we can assume that its pre-torque thickness was similar to that of those.
• For max scienceness, I prepared three samples of (1) and three samples of (2), then ran the experiment on all of them.

Data:




From this, we learn the following:

• (1) crushes by a small, but very consistent amount.
• (2) crushes by a larger, less consistent amount. I suspect the lack of consistency comes from the annealing process. Doing so with a torch is not super repeatable, which likely leaves the hardness all over the place. Nonetheless, they still crush more than (1), implying they're softer.
• The post-torque thickness of both (3) and (4) are closer to (2) than to (1), even though they were not annealed prior to torquing.

The first two observations confirm that the annealing works, but I think that the last observation is by far the most interesting one.

The fact that the used crush washers are closer to the annealed ones makes me wonder if this part is gradually annealing from engine heat cycles, causing the joint to lose clamping force over time. This is a bit of a logical leap, since we don't have the pre-torque data, but this could explain why this part seems to develop a leak over time, rather than leaking immediately. I'm for sure gonna be checking the torque on the tensioner after some time.

Here's a post-torque comparison of an annealed (left) vs stock (right) crush washer, as well. It's subtle, but you can tell that the annealed part crushed more:



Super long post for a super simple job, but I thought this was pretty interesting!

[Ramage]

Great write-up!!

The hours I have spent fighting with this stupid leak... I do think you might be on to something about the engine's heat gradually "annealing" the washer. It might be worth adding a step to bring the car fully up to temp (maybe and few times) and then retorquing it to spec after it cool, just to see if it settled. Edited.

Another thing your post made me think of, does the Exhaust Manifold Heat Shield (11627831352) make enough of a difference on cars that still have it installed and do not have this leak? I know for myself I only started having issues with the timing chain tensioner after I installed catless headers and did not reinstall the heat shield. Likely this is just a coincidence, but figured I would add another point of data.

[heinzboehmer]

It might be worth adding a step to bring the car fully up to temp and then retorquing it to spec while warm, just to see if it settled. Only issue with this is that area is around the temperature of the 9th level of hell after the car is at temp.

I'm not sure I would torque when warm. Wouldn't want to risk overtorquing and pulling out the soft aluminum threads in the head when everything cools back down. Retorque after a full hot-cool cycle (or multiple) seems reasonable though.

Another thing your post made me think of, does the Exhaust Manifold Heat Shield (11627831352) make enough of a difference on cars that still have it installed and do not have this leak? I know for myself I only started having issues with the timing chain tensioner after I installed catless headers and did not reinstall the heat shield. Likely this is just a coincidence, but figured I would add another point of data.

I've always kept the heat shields installed on my car, but I bet that taking them off doesn't help with this issue.

[Ramage]

I'm not sure I would torque when warm. Wouldn't want to risk overtorquing and pulling out the soft aluminum threads in the head when everything cools back down. Retorque after a full hot-cool cycle (or multiple) seems reasonable though.

Good call, the thread engagement depth of the tensioner is somewhere between 14mm and 17mm making it already a risk of stripping. Edited my comment.

I've always kept the heat shields installed on my car, but I bet that taking them off doesn't help with this issue.

Adding to this theory is that the last time you smelled oil and saw seepage was after a track day which even with the heat shield in place would bring the temps around the tensioner up to extreme levels.