heinzboehmer's 2002 Topaz 6MT Coupe

[ethan]

So when are we making that custom rear subframe?

Could this be as "simple" as cutting off the old RCA pickups on the stock subframe and welding on new ones but lower? I suppose you could then use two pairs of ARCAs with coilover rear suspension. I might be able to do some scanning with the Einstar and experimenting on my track car over the winter.

[heinzboehmer]

It probably does! Rear suspension looks jacked up because of that damn high rear roll center, and the camber changes *significantly* with ride height because that instant center is basically in the diff, related to the stupid high roll center.

So when are we making that custom rear subframe?

[bigjae46]

I took the rear bumper off to do the muffler swap and noticed that the adhesive on some of the crash bar tabs had failed, so fixed that. Cleaned the area and reattached the tabs with JB plastic bonder. I also decided to add a couple rivets to each tab (including the ones that still hadn't fallen off) for some extra security. Don't think these are coming off anytime soon.

No adhesive seemed to work for me...rivets seem to be the only way to go.

[Bry5on]

Think this pic illustrates the motivation behind the camber arms quite well:

Rear right wheel looks almost like it's got positive camber!]

It probably does! Rear suspension looks jacked up because of that damn high rear roll center, and the camber changes *significantly* with ride height because that instant center is basically in the diff, related to the stupid high roll center.

Apologies for the thread hijack.

[mention]Bry5on[/mention] are you okay with me adding this to the CAD files master list sticky for everyone's future reference? https://r.tapatalk.com/shareLink/topic?share_fid=2212386&share_tid=271707&url=https %3A%2F%2Fnam3forum%2Ecom%2Fforums%2Fmobiquo%2Fredi rect%2Ephp%3Ftid%3D271707&share_type=t&link_source =app

Yep, no problem

[karter16]

Thanks ethan for hosting! Files can be downloaded here: http://bry5on-nam3forum.sfo2.digital...step_files.zip

Apologies for the thread hijack.

[mention]Bry5on [/mention] are you okay with me adding this to the CAD files master list sticky for everyone's future reference? https://r.tapatalk.com/shareLink/top...ink_source=app


Sent from my iPhone using Tapatalk

[heinzboehmer]

Think this pic illustrates the motivation behind the camber arms quite well:



Rear right wheel looks almost like it's got positive camber!

Also, cool pic with friends:

[Bry5on]

Happy to host them on S3. PM me if that would be helpful.

Thanks ethan for hosting! Files can be downloaded here: http://bry5on-nam3forum.sfo2.digital...step_files.zip

[heinzboehmer]

Also I believe heinzboehmer redesigned the upper duct to better match the dust shield if memory serves. Heinz, shoot me that file if you want.

Sorta. I redesigned the upper duct to match my modified brake shields. I had previously cut them to install circular flanges for traditional brake duct hoses.




Happy to share the files, but they're matched to the cut shields on my car, so not sure they'll be useful to anyone else.

[ethan]

Follow instructions here for flap trimming: https://nam3forum.com/forums/forum/m...963#post253963

Trying to upload step files but they’re too big for the forum. Will have to find a spot to host them. Also I believe heinzboehmer redesigned the upper duct to better match the dust shield if memory serves. Heinz, shoot me that file if you want.

Happy to host them on S3. PM me if that would be helpful.

[Bry5on]

That's a pretty great result.

Want to share the scoop files?

Follow instructions here for flap trimming: https://nam3forum.com/forums/forum/m...963#post253963

Trying to upload step files but they’re too big for the forum. Will have to find a spot to host them. Also I believe heinzboehmer redesigned the upper duct to better match the dust shield if memory serves. Heinz, shoot me that file if you want.

[Obioban]

Alright, time for a bit of science. Did some testing to qualify whether the brake scoops help the dust boot problem at the latest track day.

This whole experiment is based on the assumption that my driving is consistent enough to draw somewhat reliable conclusions from. Thunderhill 3mi is definitely the track that I know the best, so I don't see much of an issue with consistency. Also, the two track days I'm comparing did happen at different times of the year, but the day with scoops was MUCH hotter, so the scoops needed to be extra efficient to make a difference. Here's a quick overview of the experiment design:

No scoops track day:
- Mar 2024
- Thunderhill 3mi bypass configuration
- 3.5 hrs of track time
- Ambient temp: ~15 C
- Cloudy skies
- ~2:05 min/lap
- More pad life

Scoops track day:
- Sep 2024
- Thunderhill 3mi bypass configuration
- 3.5 hrs of track time
- Ambient temp: ~35 C
- Sunny skies
- ~2:05 min/lap
- Less pad life

Car setup (same both days):
- ~3200 lbs
- ~315 whp
- MK60
- RBF600 (purposefully did not flush fluid so that the only potential difference would be worse thermal capacity on the scoops day)
- Bridgestone Potenza RE-71RS
- Cerakoted 996 calipers (finish supposedly helps dissipate heat)
- Girodisc titanium pad shims
- Brand new girodisc dust boots installed before each day
- Same PFC08 pads front + rear (as in the same exact parts, not just the same compound)

The experimental results are meant to be qualitative and not quantitative. Basically just trying to see if having the scoops makes the dust boots survive.

I found one cooked dust boot on each side of the car after the no scoops track day. Scoops track day involved thinner pads and higher ambient temps, so zero cooked boots would point to working scoops and not increased thermal capacity in the system (in reality thermal capacity decreased).

Aaand the results:






Success! Dust boots seem totally fine We'll have to see how many more track days they last.

Also, a few entertaining things I found when dressing the car back up for street duty.

These used to be rotated 90 deg:



These pins and screws used to be centered on the rotor holes:



And these tires used to work:



Man, this last track day really made me remember how hard this sort of driving can be on the hardware. Tons of fun, but it really does age parts very fast.

(and yes I'm aware I need more camber, more on that soon)

That's a pretty great result.

Want to share the scoop files?

[heinzboehmer]

Also patched the latest BlueBus source with my memory mirror feature and updated my unit. Realized I never uploaded the feature anywhere, so put it on GitHub

Posting link here for posterity: https://github.com/heinzboehmer/BlueBusMirrorMemory

Not exactly the prettiest code, but this will likely never make it into the BlueBus source, so I'm keeping the hacky aesthetic

[heinzboehmer]

Got a few things done this past week.

First, wrote some super quick and dirty validation FW to make sure the V5 Gauge.S board could talk to the car. Did this to rule out the issue being a hardware one. Here's the validation code if anyone is interested: https://github.com/heinzboehmer/Gaug...54HP-Validator

Here's the test setup. From left to right, OBD II Gauge.S connecter with D bus tap, V5 Gauge.S board, ESP32 programmer, logic analyzer:



It works!



After some conversations with sorek, we found that the FW for the new board was initializing serial comms with the TJA1021 with two stop bits, instead of the one stop bit called for in the ISO 9141-2 spec. Sorek built a beta FW for me with just one stop bit and it works great! It's nice to have the new HW working correctly now. No pics of the new board in the car cause it looks exactly the same as before.

Then moved on to addressing the camber thing. I had been running about -1 deg camber in the rear and -2 in the front because I was limited by the stock rear camber arms. I had a set of aluminum Eibach camber arms sitting on the workbench, but had been putting off the install since I knew it was going to be a pain. However, the last track day really made it clear that I desperately need more camber, so I finally got around to it.

Pic of the amazing design that makes this a ~5 hr job, instead of a 30 min one:



I managed to cheat and get the bolts out by undoing the three diff bolts and just moving it around (leaving driveshaft and axles attached), but man, it was crazy tight. Couple mm longer bolts and I don't think this technique would have worked.

I marked the location of the eccentric bolt on the old arms and then matched the length of the new arms to that. Kinda hard to see the silver mark, but it's there on the right side of the bolt head:




Also, this is what the stock eccentric bolts looked like. These parts were replaced when I installed the VinceBar, so only about four years old:



I blame this on the track. Don't think those small tabs were designed with the lateral forces that modern 200tw tires can generate in mind

Forgot to take a picture, but since these arms have rubber bushings on the subframe side, they need to be torqued at ride height. As luck would have it, a good friend who lives a few blocks away just got a four post lift in his garage, so I went over there and torqued them to spec on it. Always a pleasure to work on the car with a lift. If only my garage had taller ceilings...

Here's the new alignment specs:



Wanted to get closer to -3.3 deg front and -2.3 deg rear camber, but the new limiting factor in the rear is toe. Tech wasn't able to get any less than 3/32" toe in at -2 deg camber, so we decided to leave it there. Guess I'd need to lower the car further to be able to get more camber without crazy toe in. Honestly very annoying, as I was hoping to go back to stock ride height after doing the camber arms, but I guess I'm staying at this height for the time being. Always fun playing the compromise game.

Since I had the exhaust out, I replaced the section 3 that was on the car with another stock one. Old one has started to rattle on cold starts and it was driving me crazy:

Kinda crazy to see how much more abuse the old (bottom) muffler had taken. Especially considering the new (top) one came off a ~200k mi car:



Old one looked very similar to the new one (and didn't rattle!) when I installed it a few years ago. Blaming this on the track as well.

I took the rear bumper off to do the muffler swap and noticed that the adhesive on some of the crash bar tabs had failed, so fixed that. Cleaned the area and reattached the tabs with JB plastic bonder. I also decided to add a couple rivets to each tab (including the ones that still hadn't fallen off) for some extra security. Don't think these are coming off anytime soon.




Ended up doing a ton more work than expected for a pair of components that are held in with four bolts, but glad to be done with this now.

Next up, radiator! Car was having a lot of trouble with coolant temps on track, so I think it's finally time to replace the original, 141k mi old radiator. I've replaced everything else in the cooling system, but never did the radiator as the cooling efficiency was completely acceptable. Was seeing ~30 C temp drops across the rad at speed and ~16 C ambient temps. Closer to ~10 C drop at ~30 C ambient. Guess it was fine for the street, but not for a hot track day. Also definitely rolling the dice with those old plastic end tanks, but no failures so far

New radiator is sitting in a box in the garage. Just waiting for the motivation to cover my garage floor in coolant.

[heinzboehmer]

You had blanked the bumper brake duct holes for this one right? Ie: only clean air coming from under the car, not through the factory ducts, same as my testing?

Yep! The outlets I added to the stock ducts for brake cooling hose were taped off and the openings in the fender liners were covered with the stock clip in covers (used two of the solid ones, not the one with the holes). Also trimmed the pork chops. Basically just replicated the setup on your car cause that's what you tested with.

How can we get some of those scoops?!?!

Gonna need to talk to Bryson for that

[davidinnyc]

How can we get some of those scoops?!?!

Cash. Lots of cash.