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Have decided to build the shell in the shed to CAMS 2B and WTAC Clubsprint and get it to 804kg with all my running gear fitted.

The aero in 2B and clubsprint are different, however not a big issue to have 2 splitters.

Should have the weight of the shell on the weekend and this will be the starting point!

Planned jobs

1. find seat and have it fitted
2. fit CAMS cage

Awesome news. Excited to see the development

Go Magpie!

So now Blue shell will now be Jay's car? Great to hear you're moving forwards, bring on P804!

Great news! I'm sure this means you'll be entering the mx5/86 challange this year to get a taste for racing

Exciting news mate.

Just wondering, I happened to be flicking through the 2018 WTAC regs, and it looks as though they have the NA MX5 listed at a minimum weight of 893kgs for the Clubsprint Class. This is without driver and a maximum of 5L of fuel.

Am I reading it wrong?

893 as it says in the rules, probably doable.

804,I'm assuming that this is applying the extra 10% for an Naturally Aspirated car on the listed MX5 NA weight, but they aren't turbo from factory, so one would think that the weight listed is the weight, meh rules are for interpretation and I would interpret it as 804 also.

But honestly within those club sprint rules, I don't think it is actually possible. Please I would like to be proved wrong, and I don't like being a negative nelly.

From what I can see:

Bonnet - CF - not a big saving
Boot CF - massive saving
Front bar CF - not a big saving - and super expensive
Rear bar - most of it is gone anyway so doesn't count
All glass lexan - ok saving
Custom tiny fuel tank - not sure but saving
Battery - Lithium - big saving
Cage - + more weight
Exhaust free - titanium headers to tip - big saving - super dooper expensive
Custom wiring - decent saving
Remove all first gear related internals - not sure if its possible, but is a saving
BBK - small saving

Even with most of that, you are still coming in at about 850 or more.

Surely it's also about what can be completely removed or gutted, not just replaced - ie door skins only with reinforcements removed (cage is for safety anyway) etc

Tim_cyc03 wrote:804,I'm assuming that this is applying the extra 10% for an Naturally Aspirated car on the listed MX5 NA weight...

I don't think it is actually possible. Please I would like to be proved wrong, and I don't like being a negative nelly.

I think it will be a BIG struggle to get to 804kg...

Lexan windscreen - not allowed in clubsprint.
Heated windscreen - allowed and the fan/HVAC/heater can be removed as to all the dash venting.
Lexan windows - if full cage then running a net so the window would only be required for transport etc.
Fuel tank - Just weighted the OEM tank and it is 12kg. However its mass is rather high and lowering this would also help.
Cage - but what can be removed to fit the cage. For example door intrusion bars no longer required, parcel shelf, if fuel cell installed all the sheet metal around the fuel tank can be removed. Dash, does not need massive bar anymore, cage can be used to mount steering. The OEM dash is required however it can be just a shell.
Wiring - the OEM loom with no brackets is 12kg, however this did not include the steering wheel 'stuff'.
Radiator - as small as possible. Yet to weigh my current setup but I think there is a decent saving here as well.
Oil Cooler - again as small as possible

Will start to weight all the other parts over the weekend to make a list up.

Racing and time attack have completely different cooling requirments, so don't go to crazy on cutting cooling system to save weight.

This is the same with fuel tank capacity. Given the other e85 mx5s have to add another fuel tank to do a 1hr race, you might not want to fit a super small fuel tank.

There are more areas that you probably want to look at in detail before deciding which path to go down. A purpose built time attack car focusing on minimum weight isn't going to make a very reliable race car (or even one that will finish a race). At the cost of some extra weight you could have a reliable race car, but it isn't the lightest possible time attack car.

You could get a full tubular subframe and arms if that's allowed in the rules, will save weight, but won't be cheap.

Mega costly to lose weight.

Can you go billet block in club sprint?

If you're going billet block, may as well go dry sump... and have the block based off a k24... with a honda head...

Maybe it might be cheaper to buy an ginetta?

plohl wrote:Can you go billet block in club sprint?

Yes - not in the budget

plohl wrote:and have the block based off a k24... with a honda head...

Clubsprint engine has to be from the same manufactrer and have the same number of pistons. In the MX5 I can use any 4 cylinder mazda motor. The Mazda 26B four rotor is considered a production engine by the promoter.

plohl wrote:Maybe it might be cheaper to buy an ginetta?

Ginetta is NOT listed, would have to ask...

I would expect that maybe by Aug 2019 I would have the car ready for testing so until that time the blue/silver MX5 is my 'ride'.

If I think strategically then I could make provisions to swap in another fuel cell as what it would be to change cooling systems.

Magpie wrote:Clubsprint engine has to be from the same manufactrer and have the same number of pistons. In the MX5 I can use any 4 cylinder mazda motor. The Mazda 26B four rotor is considered a production engine by the promoter.

So does it just need to be a factory block?
and apart from that, it's open slather?


Obvious choice for power/weight would be a rotary.

But if you wanted to stay piston, you could look into an FE block. a bit heavier than a B6/BP, but can cope with a lot more boost etc.
FE-DOHC (or FE3 colloquially) would be the pick, mainly for the twin cam head.


Otherwise, I have heard that one of the later Mazda 3 blocks was heavily B6 based, AND aluminium.
No idea on strength, but could certainly be a weight saver with the alloy block.


edit:
ZM-DE looks like the later one that was super close to a B6.
Cant find definitive info if it's allow lime other Z blocks, or Iron like a B6/BP

hks_kansei wrote:So does it just need to be a factory block? and apart from that, it's open slather?

That is correct from the same maker and same number of cylinders. I could ask about is a 4 rotor engine the same as a 4 piston... they both have the number 4 in them...

I could look at the MZR engine, however engine swap is not on the cards at the moment.