Liam's Z4C race car project

[Anonymous]

This is a great thread. Really enjoy it. You have some nice lines through there.
One question though, have you got a 6 point harness fitted?

 

[JamieZ4C]

Loving this thread! PM'd you about the seats

 

[Sidewaze Samm]

The interior strip starts this weekend. Shout if you want anything... piano black trim and oyster leather sports memory seats (non-heated).

I'd be interested in the black trim

 

[Liam22]

Thank you all for the kind words. I have learnt a lot from the forum archives, so I'm pleased to give some content back

The strip is well underway. Boot trim alone weighs 11kg.



20kg main cabin trim
56kg seats and belts
13kg carpet and rooflining
2.8kg centre console
2.2kg speakers
5kg door cards
1.4kg side airbags
0.8kg bolts/screws

Today's total, 112.2kg



Ran out of enthusiasm to get the dashboard out today, but its empty enough for my local roll cage guy to take a look at it. He'll be happy that the roof skin is removable. I quite fancy replacing it with a carbon fibre panel.

Pleased not to have stick-on soundproofing anywhere.

Looks like I'll be taking a reciprocating saw to the big lump of metal behind the seats. It's not doing anything but adding weight.

 

[Liam22]

One question though, have you got a 6 point harness fitted?

Not yet. Harnesses will go in with the race seat, and after I have fitted eye bolts into the floor pan.

 

[Thrustyjust]

Love this thread and enjoy the work you have put in . Quick question on the flywheel. Is there any noticeable vibrations from being a non - dmf and also does the engine respond any better for the weight reduction ?

 

[exdos]

Looks like I'll be taking a reciprocating saw to the big lump of metal behind the seats. It's not doing anything but adding weight.

Is that not part of the coupe's structure and totally removing it might compromise the stiffness? Or, are you relying upon the roll cage to supplement that?

 

[Liam22]

Re flywheel, can't speak to vibration because I have solid engine mounts so the vibrations are terrible! The flywheel itself is great though, the revs fall very fast.

I don't think the central structure adds a lot of stiffness, its single skin where it meets the side of the car. Looks most like its vertically strong to protect in a convertible rollover situation. Also, a decent chunk of it will need removing anyway, to pass roll cage tubes through to the rear suspension towers.

If you look at photos of Z4C race cars they do not have that part at all. A diagonal from roof to floor, combined with harness bar across the middle will be much stronger.

 

[Liam22]

How do you feel about the Strongflex bushes? At some point I'd like to get PU bushes, would you recommend them for a street car? I have also fitted the ones for the shifting linkage, was a real PITA since I did it without removing the driveshaft but now shifting feels a lot better!

So far so good. They have all fitted perfectly with the exception of the elliptical shift arm carrier bushes. I replaced all of the shifter parts apart from the lever itself.

Feels great, especially when warmed up. Rifle bolt all the way. Combined with stiffer gearbox mounts and engine mounts there is absolutely no movement of the shifter unless I'm moving it

 

[JDavis21]

20kg main cabin trim
56kg seats and belts
13kg carpet and rooflining
2.8kg centre console
2.2kg speakers
5kg door cards
1.4kg side airbags
0.8kg bolts/screws

Today's total, 112.2kg

Looks like I'll be taking a reciprocating saw to the big lump of metal behind the seats. It's not doing anything but adding weight.

That's some good weight saving! Surprises me that there's no stick on sound deadening anywhere, but also makes life easy for you.

From what I've read that lump of metal is around 16-18kg to cut out, and definitely not required structurally, hence the BMW built GT cars not having it there.

Did you get a weight of the car before you started?

 

[Liam22]

Did you get a weight of the car before you started?

1362kg (full tank of fuel) on the Snetterton weighbridge.

Brings my current empty weight down to 1210kg.

Lots of weight loss to happen yet:

- That central metal thing
- Carbon roof panel
- HVAC system incl aircon compressor and rad
- Engine bay soundproofing
- Exhaust system
- Lithium battery and shorter cable runs
- Dash lightening, incl airbags, steering wheel
- Headlamp washers, smaller washer bottle
- One wiper arm
- Redundant wiring

All offset by adding roll cage, seat, belts, fire extinguisher.

Target weight is 1200kg in qualifying trim. That would be the equivalent of 300bhp at my current weight.

 

[AlpinaZ4]

Spent most of the morning trying to get a decent ABS/DSC combo working. Even with the DSC turned off (long press on DTC button) it's still actually on. It'll let you have a small slide but still intervenes, and makes the steering feel terrible. So I went through the process of individually removing every single fuse related to ABS, DSC, and DTC. My goal was to retain the ABS while completely disabling DSC. No luck. So I ended up keeping fuse 43 removed which disabled ABS and DSC as this also had the best steering feel.

That's odd. I have a Quaife diff on my 3.0Si Coupe and DSC can be turned off with 1 long press.
Recently completed several full day sessions on skidpads with no DSC intervention.

 

[JDavis21]

Did you get a weight of the car before you started?

1362kg (full tank of fuel) on the Snetterton weighbridge.

Brings my current empty weight down to 1210kg.

Target weight is 1200kg in qualifying trim. That would be the equivalent of 300bhp at my current weight.

It'll be mega at 1200kg.

Are you looking at fitting lighter non-OEM wheels? Or I guess that's restricted with budget?

 

[AlpinaZ4]

- Carbon roof panel

Possibly useful:
http://www.carbon-factory.de/en/automotive/bmw/bmw-zseries/e85-e86/103/bmwvz4-roof?c=162&number=SW10005

According to realoem the roof panel is 7,9kg so not much weight saving.

In your case I'd probably go for a Lexan rear window (original rear window 7,5kg) for similar weight saving that's much easier to achieve.

 

[adam1985]

Not sure if you have seen these threads but thought they might be of use;
https://z4-forum.com/forum/viewtopic.php?f=9&t=111079
https://z4-forum.com/forum/viewtopic.php?f=2&t=100911&p=1476196&hilit=carbon+roof#p1476196
https://z4-forum.com/forum/viewtopic.php?f=9&t=101634&hilit=roof

 

[Liam22]

A bit more weight reduction this weekend:

- 4.0kg Passenger airbag
- 1.6kg head unit and cables
- 1.0kg main dash insert

Most significant was the the OEM battery and clamps at 19.5kg. The 1.0kg lithium battery that previously failed to start the car now works fine with a direct connection on the main terminals, and with a lighter flywheel to turn.



Ultimately I plan to relocate the battery to the passenger compartment and significantly shorten the 12V supply cable runs. I need to understand the cable routing options better before attempting that.

 

[Kev]

Interesting read
Just starting to try and lighten my roadster for track days after doing just one! Seats are mega heavy currently trying to change them but also couldn’t believe size of the rear speakers by the seats! Appears to be a lot of junk in these cars

 

[Liam22]

I noticed that only the offside rear fog lamp was working despite having a good bulb in the nearside lamp. Did some searching to find this is normal!

MSA rules require either a central rain light or a symmetrical pair. So I found the offside wire and bridged the two lamp connectors to prove that the nearside will light up. It's the yellow wire with black stripe.



Cut both wires of the same colour and used the nearside one as live for both sides. This worked but triggered the bulb warning light on the dash as I had cut the unused feed for the nearside lamp!

My slightly dodgy solution was to splice all 4 ends together. So the lamp check works, but I also have both fog lamps working. Used a heat shrink solder tube for the splicing.

 

[Liam22]

A bit more weight loss in preparation for roll cage fitting.

The big one was the heater at 8kg just for blower and matrix unit behind the dash. Utter pig to remove though, ended up having to disconnect the steering column from the dash bar (8 bolts!) and pull the whole thing forward to provide enough clearance.

Aircon compressor and pipework not yet removed, so not sure of the grand total weight of the HVAC system.

The heater hoses both lead back to the expansion tank which is convenient as they can now be looped with very a very short hose run.

I removed the airbox and intake trunking to give more clearance and decided to delete the sound generator. Ideally I would find a suitable length of silicon hose for this, but for now I just blanked off the sound generator pipe with a rubber bung I just happened to have left over from my last race car build. Never throw things away!

A little Gorilla Glue will prevent it from being sucked into the throttle.

 

[Liam22]

Removing the heater now leaves 5 holes in the bulkhead:

- Aircon condensate drain (above gearbox)
- Fresh air intake (letterbox)
- Sound generator (behind glove box)
- Heater inlet/outlet (diagonal hole)
- Aircon inlet/outlet (next to heater)

I made some simple aluminium panels to seal it up. In this photo the drain hole is done and I'm lining up the sound generator panel.



I realised that the sound generator hole would be perfect for passing through a battery cable to the starter motor for when I relocate the battery. So I fitted a post to the panel so that a cable can be attached from both sides without fear of rubbing.



You can see how brilliantly close it is to where the cable that runs under the car meets with the starter cable

The heater/aircon holes were a bit more fiddly, especially as I want to use the rubber grommet to pass fire extinguisher pipe. Made a template with cardboard and a Stanley knife which worked first time.



It's not pretty, but will be painted with the rest of the interior after the roll cage goes in.

The fresh air letterbox will be used as a cold air feed for driver ventilation. Planning that at the moment. A windscreen demist solution will also be fitted, probably picking up the existing dash vents.