MX5 NA8 Weight Cut

[RileyR]

Hello all,

In this thread I will track the weight cut that I will do on my 1996 NA8 MX5. Maybe others will get something out of it, and maybe people will contribute to the process.

The car was daily dríven, but I now ride a motorbike daily and the MX5 is dríven much less these days. I used to love competing in sprints and time attack style events. It has been over 12 months since the MX5 was last on track, but I intend on getting amongst it again.

Years ago I had a build thread for the car, which can be found here: viewtopic.php?f=57&t=69587&hilit=riley

The 1.8L engine has recently had a full rebuild, top and bottom back to factory standards. No extra HP was chased. I did however add a sump baffle and Nitro dann engine mount. Here is the thread for that: viewtopic.php?f=29&t=77777

I want to do the weight cut in order to get faster times on the track, and have more fun in it in general. Because its not a Daily Driver (DD) some luxuries can be taken out. I want to take out 100kg from the car which might gain me 1 sec or so at Phillip Island. Its the cheapest way to get faster.

So far from research this is the plan:
Spare tyre & jack (12.25kg). possibly replace it with a can of that stuff that fixes small punctures and re-inflates the tyre.
Power Steering (5.44kg). saves weight and gives a better feel while at speed. I have also had issues with the PS fluid spitting out the reservoir.
Baby Teeth (3.62kg). Replace them with lighter weight race tow points.
Soft Top. (16.78kg) . Currently ripped and needs replacing - so it will come out, saving weight and money. I run a hard top 95% of the time anyway.
Aircon. (17.23kg). Hardly ever turned on, doesnt work very well and will save a tonne of weight.
Insulation (5kg?). not needed, save a little weight.
Misc ???
Total: 60kg

I still need to make up 40kg somewhere to reach the 100kg goal. Maybe that 40kg will get more expensive with wheels etc.

[RileyR]

First thing to come out

sound deadening from the boot. It was there to stop rattles from sub woofer, worked well but time to come out. No more super hektic subwoofer bro.
Weighed 1.07kg.
98.93kg to go.

mx5 wc 1.jpg

[StanTheMan]

Carpet
Centre console
Start drilling holes in the chassis aka Slammer
If his thread was still around you’d have a good laugh


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[RileyR]

Does it even need a boot lid? haha

It will stay registered. other wise this could get extreme!

[Magpie]

You will need to buy a trailer

Remember that like the baby teeth something has to go back in. What does it weight now?

Think about

1. Exhaust - do you need to meet noise limits?
2. Carpet - a few kilos
3. Radio
4. Swap OEM for a lithium (BIG weight saving)
5. Passenger seat
6. Lug nuts - you will be surprised how much are in these
7. Rewire - 5-10kg
8. Sun visors
9. HVAC - fit heated windscreen

[Custardtart]

Sell oem hardtop, buy carbon fibre one. Should be cost neutral? Save 15kg?
Wilwood calipers saves 8kg all round?
2 piece rotors saves 6kg all round?
Lighter wheels - save 5kg all round?
R compound tyres - save 10kg all round

[bruce]

Been done many times before with a really old webpage in the States which detailed it to the n-th degree (I don't think the page exists anymore?) I remember way back when Dann was still in diapers he had a silly idea to strip out his car. I think it turned out to be akin to a tin can held together with bailing wire.
I think in the end you may really devalue your car by making it unattractive to any buyers down the track.

[Magpie]

Been done many times before with a really old webpage in the States which detailed it to the n-th degree

https://www.lightweightmiata.com/beast/lightness/

[Magpie]

Start drilling holes in the chassis

I plan to start on my shell VERY soon with these

[StanTheMan]

Yea you’d remember Slammer, he did. All that to Scooter. I think his car is in QLD now.


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[rascal]

R compound tyres - save 10kg all round

I’ve found R specs are usually heavier than normal road tyres, given like for like.

[LiteIsRite]

Spare tyre & jack (12.25kg). possibly replace it with a can of that stuff that fixes small punctures and re-inflates the tyre.

In replacing mine, I went with this... https://www.bikebiz.com.au/cargol-turn-go-road-tyre-repair-kit... possibly slightly heavier than the can of goo but a lot less messy.

[greenMachine]

Don't worry about taking out the spare and jack, they have to come out anyway when the car is tracked. As would the can of goo, if you replaced it with that.
Lightweight seats
Lightweight battery, lightweight alternator. Relocate battery to engine bay (or inside cabin) and shorten that heavy battery cable (this means a VERY lightweight battery!). Only one rad fan.
Gut the inner panelling on the boot (you'd be surprised how much that weighs!), secure with rubber straps a la rally cars. For extreme, take out boot hinges too.
Remove window winders, replace headlight lifts with string (not joking), or similar, or replace with fixed low profile lights, or just fix lights in upright position. Replace side windows and q/lights with Perspex (big savings). Perspex rear window on h/top.
Don't forget to remove radio speakers.
Remove bonnet rod.
Replace front ARB with a hollow Racing Beat one.
If (and only if) you do the cooling reroute, you can remove the heater and fan and all the ducting, replace with an electrically heated windscreen.
Starvation diet for driver.

Offsetting all this will be the half cage you will need ...

If you were serious about this, you would strip the car down, remove every nut and bolt. Cut off every unneeded bracket (marked as you disassembled). Rewire with only absolutely necessary wiring in thin gauge (much $$). Every bolt is shortened to be just long enough to do the job. All brackets drilled for lightness. Windscreen replaced with thinner glass. While the car is stripped, you would get out the hole saw and lighten all non-structural steel. Something to do for the next Christmas holidays ...

[Custardtart]

Don't worry about taking out the spare and jack, they have to come out anyway when the car is tracked. As would the can of goo, if you replaced it with that.
Lightweight seats
Lightweight battery, lightweight alternator. Relocate battery to engine bay (or inside cabin) and shorten that heavy battery cable (this means a VERY lightweight battery!). Only one rad fan.
Gut the inner panelling on the boot (you'd be surprised how much that weighs!), secure with rubber straps a la rally cars. For extreme, take out boot hinges too.
Remove window winders, replace headlight lifts with string (not joking), or similar, or replace with fixed low profile lights, or just fix lights in upright position. Replace side windows and q/lights with Perspex (big savings). Perspex rear window on h/top.
Don't forget to remove radio speakers.
Remove bonnet rod.
Replace front ARB with a hollow Racing Beat one.
If (and only if) you do the cooling reroute, you can remove the heater and fan and all the ducting, replace with an electrically heated windscreen.
Starvation diet for driver.

Offsetting all this will be the half cage you will need ...

If you were serious about this, you would strip the car down, remove every nut and bolt. Cut off every unneeded bracket (marked as you disassembled). Rewire with only absolutely necessary wiring in thin gauge (much $$). Every bolt is shortened to be just long enough to do the job. All brackets drilled for lightness. Windscreen replaced with thinner glass. While the car is stripped, you would get out the hole saw and lighten all non-structural steel. Something to do for the next Christmas holidays ...

Seriously, I'd love a project like this

[RileyR]

haha wow!

I think I need to change the title to "Streetable MX5 NA8 Weight Cut" or "Mild MX5 NA8 Weight Cut"

I appreciate all the input every one!

Magpie: If only I could buy a trailer and a car to tow it! Unfortunately that's not possible. I still want the car to be registered (coming up to H plates soon!) and to be enjoyed on weekends. I just want to make it a bit more track-able, and a bit faster for cheap. and the cheapest way I can think of is to remove all the superfluous stuff (ok maybe not ALL!). A better battery is a great idea! Mine is a bit average and needs a trickle charger these days. I plan on keeping the stereo, but am removing the sub woofer and amp. I tried using an aldi blue tooth speaker and it wasn't loud enough to listen to podcasts. I plan on keeping the carpets, but removing all the insulation underneath them. That link has some great info in it!

Liteisrite: thanks for showing me that product, looks good.

Greenmachine: Now that you have said that I tend to agree that I should leave the spare wheel and jack in the car until track time. It has sparco sprint seats in there now, which would have had to save weight. Your suggestions are awesome, but a bit too much hassle on a car that I still want to take to the shops. I think my title was misleading and got every one more excited than need be haha. Perspex rear window is a good idea, or as Custardtart said, replace with CF one. I'll have to check their weights. It has an mx5mania torsion? roll bar, which was quite heavy haha. All this effort, as you say might just bring it back to factory weight haha

Bruce: I agree that this venture could de-value the car. However, I have no intention of selling it. It's coming up to club reg soon (a year or 2) and will not cost much to register from there. Its just finding the space for it that could possibly become an issue. Its a nice Limited Edition 1.8, but its still not worth a great deal of money. To me, its my forever car, and I want it to be exactly what I want it to be. I don't want to avoid making it what I want in-case I decide to sell it in the future for a few extra thousand dollars. ie sell for 6 instead of 9 or something.


One thing i forgot i wanted to do: Bumper Cut
I think this immediately puts me into a different class here in Vic as its an aero mod. Will have to check that and see if I should or not.