Re-engineering the Grand California 680 – from OEM compromise to a coherent, integrated system

[Bizzaru]

Hi everyone,

 

This story started in August 2024, when I bought a VW Grand California 680. During the first months (summer / early autumn) I enjoyed the van exactly as it came from the factory. Pretty quickly, however, the real limitations of the OEM setup became obvious.

Why I decided to take it apart completely

– OEM battery: real off-grid autonomy of 24 hours, after which the fridge went into protection
– weak shower pressure once the battery dropped
– toilet emptying: inconvenient and unpleasant chemical smell
– winter use: significant temperature difference between front and rear
– road noise: furniture and fittings → about 40% of driving fatigue

In short: it worked, but not as a coherent system.

 

Concept & approach

The decision was to rebuild the van as a system, not as a list of accessories.

Advantages:

• own workshop hall
• direct access to CNC machining, 3D printing and custom furniture
• 2–3 professionals involved throughout the project (electrical, mechanical, furniture)

The van was fully stripped: from the toilet area to the rear doors.
On one side, only the kitchen unit remained.

 

Insulation & structure

The OEM insulation was honestly very poor.
There were areas with no insulation at all.

I rebuilt the insulation completely:

• walls
• doors
• cold zones in the rear

The temperature difference between front and rear is now almost gone.

 

Electrical system – EcoFlow Power Kit

 

– EcoFlow Power Kit 5 kVA
– 3 batteries (one optional battery in the former gas compartment)
– battery placement designed to balance vehicle weight relative to the fresh-water tank
– dedicated fresh-air intake for EcoFlow (not recirculated warm air)

Current charging:

OEM alternator: ~1.2–1.6 kW

Planned upgrade:

secondary alternator → 6 kW continuous charging

 

Control & KFG integration

 

I developed a custom communication module for KFG, OEM-fit, which:

• switches interior and exterior lights
• controls the water pump
• controls the awning
• integrates additional functions without errors in the OEM system

For KFG, everything behaves like factory hardware.

 

Water system

 

– upgraded water pump
– grey-water tank:

• insulated
• heating pad
• mechanically protected

– electric drain valve, controlled from the dashboard
– dedicated camera to see exactly where the tank is being emptied

 

Toilet

 

– Clesana C1
– complete elimination of chemicals and smells
– clean integration, no space compromises

 

Heating & air distribution

 

– redesigned hot-air ducting
– proper heat distribution to the rear
– front and rear comfort now match

 

Audio & noise reduction

 

– sound insulation: front doors, sliding door, rear doors
– true 3-way audio system, enclosures calculated to manufacturer specs
– dedicated amplifier + DSP
– subwoofer with independent control
– major improvement in driving comfort

 

Lighting

 

– OEM LED strip replaced with a digital LED strip
– ON/OFF via OEM display
– colors and scenes controlled via my own app

 

Connectivity

 

– 5G modem, easily accessible
– Starlink for areas without mobile coverage
– stable connectivity for remote work

 

Cameras & exterior

 

– 1080p rear camera, OEM-fit for the large display
 

Awning & step

 

– longer awning, extending past the rear window
– electric operation + app control
– new step with a control module that perfectly simulates the OEM step for KFG

 

General principle

 

I avoided drilling the van wherever possible. Where drilling was unavoidable:

• custom ABS parts, OEM-fit
• body protection
• VW-recommended sealant

 

What’s next

1. secondary alternator (6 kW)
2. rear furniture reconfiguration:

• daytime: sofa / lounge area / nighttime: full bed, no compromise on sleep quality (same or better than the current setup)

 

Questions, criticism and ideas are welcome.

 

Because of forum limitations, I can’t include everything in a single post (photos).

I will therefore add separate follow-up posts, each with photos that relate to the topic.

[Bizzaru]

Insulation & structure 

 

OEM insulation: 

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Rebuild insulation: 

All the walls doors and roof top have been reinsulated.

 

[Bizzaru]

Electrical system – EcoFlow Power Kit

 

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[Bizzaru]

Photos & gallery note

Uploading photos directly to the forum is quite slow and limited, so I will create a OneDrive photo gallery where I’ll upload all relevant pictures in full resolution.

[MarioRS]

Servus Bizzaru,

 

very impressive, thank you for sharing!

 

Do you offer such a reconstruction, or partly optimisations, professinally or is this a solely private improvement project?

 

Greetings from Vienna, Mario

[Bizzaru]

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Hi Mario,

thank you very much for the kind words, I really appreciate it.

At the moment this started as a private project, driven mainly by passion and curiosity rather than a predefined commercial offer. That said, I don’t exclude the possibility of offering selected optimizations or reconstruction work in the future.

For now, I’d prefer to first finish documenting the project here. After that, I’d be very interested to hear what you liked most and what kind of changes or optimizations you would personally be interested in. That feedback will help me understand where this could make sense beyond my own van.

Greetings to Brasov,
Bizzaru

[Bizzaru]

Electrical system – EcoFlow Power Kit 

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[Bizzaru]

Electrical system – EcoFlow Power Kit

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[Bizzaru]

Control & KFG integration 

 

This custom control unit is the central interface between the OEM KFG system and the additional functions added to the van.

Through this unit I intercept and manage signals from:

• physical switches
• vehicle ignition / contact
• exterior LED strip
• bathroom light
• exterior lights
• interior digital RGB LED strip

The unit also includes a Bluetooth application, which allows additional control and configuration without relying on the OEM display.

One important feature is that the audio system can be powered on and used without ignition. This makes it possible to use the full Hi-Fi system while camping or parked, without turning the vehicle on.

The goal was seamless integration:

• OEM behavior preserved
• no KFG errors
• no visible “aftermarket logic” from the driver’s perspective

From the outside, everything behaves like factory equipment, while internally the logic is fully customized.

 

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[Bizzaru]

Lighting

For the exterior lighting I wanted a clean installation and correct light direction, not just “mounted lights”.

The body shape was 3D scanned, and based on that I designed and 3D printed custom adapters that match the curvature of the vehicle perfectly.
These adapters create a flat mounting surface, allowing the lights to be installed at the correct angle.

As a result, when the lights are switched on, the beam is directed exactly toward the ground, where it’s actually needed, without glare or wasted light.

This also allowed me to avoid unnecessary drilling and keep the installation visually and technically OEM-like.

 

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[bendicht]

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Hoi @Bizzaru

 

Gratulation, das ist doch mal ein Ansatz. Mit deiner Lösung angepasst an meinen ID,Buzz könnte ich das schreckliche Softwarekonzept von gestern von VW, ein bisschen in die Neuzeit bringen.

Würde gerne mal mit dir zusammentreffen. In welcher Gegend wohnst du?

 

(Ich schreibe bewusst in deutsch. Als Schweizer ist es üblich, dass jeder in seiner Sprache spricht, aber die Andern in ihrer Sprache versteht.)

 

Grüsse Bänz

 

Bearbeitet vor 3 Stunden von bendicht

[MarioRS]

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Dear Bizzaru,

 

thank you very much for your answer!

 

We already have a Perfect-Van composting toilet and a 150AH LiFePo battery and we are fine with it.

 

From my point of view, all the optimizations, that improve the life expectancy, winter proofness and comfort are desirable.

 

My favourites of your optimizations are:

1) Insulation & structure: rebuilt the insulation completely

2) Water system: upgraded water pump, insulated grey-water tank

3) Control & KFG integration: audio system, additional functions

Additionally, for me it would be a great experience and very instructive, to collaborate in the optimization and learn from your experiences. We definitely want to visit Romania soon, it would be great to combine that with an working & learning session on our Grand California.

 

Greetings to Brasov and all the best,

 

Mario

 

[Bizzaru]

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Hi Bänz,

thank you very much for your message and the positive feedback, I really appreciate it.

In principle, we can certainly look into whether and how I could help. The most important first step, however, is to clearly understand the specific problem you want to solve and where the current VW software or user interface causes the most frustration. Only then does it make sense to assess what kind of solution would be realistic.

Once I finish documenting the project here, I’d be happy to talk it through in more detail and go through the points together.

 

Best regards,
Razvan

[Bizzaru]

Lighting, materials & finish

The custom adapters were 3D printed using high-temperature resistant materials, based on ABS reinforced with fiberglass. This was important not only for heat resistance, but also for long-term durability and vibration stability.

After printing, the parts were extensively finished — honestly, probably a bit overdone.
They were sanded, sealed and prepared to a very high standard to achieve a clean, OEM-like appearance and surface quality.

For the final look, I used the original vehicle paint color code. While the result is very close, it’s not a 100% perfect match — something that is barely noticeable in real use, but worth mentioning for transparency.

Overall, the goal was not just function, but a finish that visually blends into the vehicle and doesn’t look like an add-on. The red ones are test.

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[Bizzaru]

Audio / Music system – my favorite part of the build

 

This is without question my favorite part of the entire project. Not because it’s loud, but because it completely changed how the van feels on long drives.

Before installing any audio components, all relevant doors were properly soundproofed (front, sliding and rear). This alone already made a noticeable difference in comfort and fatigue.

System concept

The audio setup is a true Hi-Fi system, not an OEM-style upgrade:

• 3-way system
• rear speaker enclosures designed to the manufacturer’s recommended volume
• speaker membranes made of wool, chosen for their natural, balanced sound

The goal was long-term listening comfort, and maximum volume.

Front & rear integration

A lot of effort went into using space intelligently and keeping everything solid and vibration-free.

Rear section:

• In the back of the van there are several corner furniture elements that are essentially dead space.
• These areas were 3D scanned, and custom enclosures were designed for a full 3-way rear system.
• The parts were 3D printed as single-piece ABS components, with additional rear supports, ensuring high rigidity and zero vibration.

Front section:

• Midrange speakers and tweeters are mounted on the A-pillars. The pillar geometry was 3D scanned, and custom adapters were printed so the speakers integrate cleanly without affecting low frequencies, which remain in the OEM locations.

Mounting & hardware

• Under the driver’s seat, a 3D-printed custom mount holds the amplifier and DSP, keeping cable runs short and protected.
• Under the passenger seat, a rigid stainless-steel bracket secures a 500 W subwoofer, eliminating flex or resonance.

In the center area, a printed support for the subwoofer volume control was added. Since the space was already available, I also integrated 2× USB-C ports (120 W each) for high-power charging.

The system is driven by a dedicated amplifier and DSP, with a separate subwoofer level control for easy adjustment between driving and camping. The head unit is Android-based, avoiding OEM software limitations.

Result

This setup didn’t just improve sound quality, it fundamentally changed the driving experience:

• noticeably less fatigue
• much calmer cabin acoustics
• clean, detailed sound at any volume
• equally enjoyable while driving or parked

It’s one of those upgrades that makes you immediately wonder how the original setup was ever acceptable.

 

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