The carbon fibre time attack/superlap MX5 NB twins blog

[rascal]

But now we are going to do forged bottom ends.

Me thinking the $15K budget is looking shaky....

Looking forward to seeing them finished though. Any idea of when you think they'll be on track...

[lightyear]

But now we are going to do forged bottom ends.

Me thinking the $15K budget is looking shaky....

Looking forward to seeing them finished though. Any idea of when you think they'll be on track...

Yer, $15k was with stock running gear, and able to track it. The plan was to get them together with all the lightweight mods done, and develop them over time. Not much point in doing everything and taking forever as you save the money to buy things. We are hoping to have them done in about 6 months. The body work will take a while. And i am looking forward to doing it.

Just picked up the new 15x9's with 225's of james at mx5centre, they fill the guards out perfectly, after lowering the car they would tuck under nicely due to camber. Would be an ideal fitment for a road car.





Just finished rubbing back the NB ready for paint, and thought i would throw them on to see the fitment.

[Okibi]

Looks good, loving your updates.

[16bit]

if you want to lose weight in the prop shaft area you are better off getting an alloy one. the cr prop shaft i have looked at in the past was heavier than the stock item but much stonger.

this build is going to be awesome.

being as you are modifying the body work i would consider putting in the some flat flooring and venturi tunnels to try and keen some of the mechanical grip that you will be losing by reducing the weight.

if you are also getting rid of the boot flooring then why not use some shrouded thermo fans and run active aero like the old brabham f1 cars to add some downforce.

[lightyear]

if you want to lose weight in the prop shaft area you are better off getting an alloy one. the cr prop shaft i have looked at in the past was heavier than the stock item but much stonger.

**I will look into it later, i have a lot of other things to do first.

this build is going to be awesome.

**Yes, it will be.

being as you are modifying the body work i would consider putting in the some flat flooring and venturi tunnels to try and keen some of the mechanical grip that you will be losing by reducing the weight.

**We are doing the flat floor with diffusers

if you are also getting rid of the boot flooring then why not use some shrouded thermo fans and run active aero like the old brabham f1 cars to add some downforce.

**Don't think thermo fans would generate enough downforce, and i would have to run a skirt around the car to seal the air, so don't think we will go that way.

[little decks]

if you are also getting rid of the boot flooring then why not use some shrouded thermo fans and run active aero like the old brabham f1 cars to add some downforce.

Jim Hall originally did this with his chapparal 2J in the Can-Am series back in the late 60s or early 70s. The size of the fans and the power required to run them meant using a separate engine (out of a snow mobile) to run them, and that was with the plastic side seals aroun the bottom of the car. It is also pointless to have this with a rear diffuser and undertray as you will just be creating low pressure between the car and undertray.

I think for the speeds you will be doing you don't need to get too carried away with aero. A good front splitter, rear diffuser and rear wing would be enough. With anything under 200 rwkw you would want too much rear wing either.

[lightyear]

You seem to know a bit about aero, but i will be doing much more than you suggest. As i think there is more to it than just a wing and splitter going by the info i have read. The rear diffuser won't work unless you have a flat floor to give un-turbulant air to it.

[little decks]

You seem to know a bit about aero, but i will be doing much more than you suggest. As i think there is more to it than just a wing and splitter going by the info i have read. The rear diffuser won't work unless you have a flat floor to give un-turbulant air to it.

Thanks...i am interested in all things racecar, and F1 is my religion, so it comes with the turf. I consider the diffuser to really imply the floor being present for this reason.
I think with what sort of power you will be starting with you want as little drag as possible. Your principle of making the car light and the extent of measures you are going to is admirable and in my opinion the best way to make any car go. With a time attack car you will probably find alot more time in a sequential gearbox and a good engine package rather than going all out on the aero... but i guess i cant say that for certain, any ideas on what other aero work you are looking at doing?

[lightyear]

I would love a sequential gearbox, but i would never be able to afford one. Unless i use a hayabusa motor with a turbo.
Basically the aero will be used to control air flow. I will be taking measures to stop air entering under the sides of the car, rather use the areo to pull air out from under the car, cannards, new guards to pull air out from the wheel arches. Just clean straight lines, with definiton. There will be scoops, scollops, fins. I have the ideas in my head, and will start on doing all the aero when the cars get back from meridian with the new cages.

They will look something like this

[little decks]

sounds good

interested to see how it turns out

[16bit]

if you are also getting rid of the boot flooring then why not use some shrouded thermo fans and run active aero like the old brabham f1 cars to add some downforce.

Jim Hall originally did this with his chapparal 2J in the Can-Am series back in the late 60s or early 70s. The size of the fans and the power required to run them meant using a separate engine (out of a snow mobile) to run them, and that was with the plastic side seals aroun the bottom of the car. It is also pointless to have this with a rear diffuser and undertray as you will just be creating low pressure between the car and undertray.

I think for the speeds you will be doing you don't need to get too carried away with aero. A good front splitter, rear diffuser and rear wing would be enough. With anything under 200 rwkw you would want too much rear wing either.

you would obviously have the fans sucking air between the floor and the road. if ferrari are doing it on the 599xx with no side skirts i would dare say it is effective.

i think you would want as much aero as possible as with the lower hp as you need every advantage you can get. not to mention that only running 225 section tyres on 15inch wheels and running up against cars with 265 section tyres and much larger wheels which have not only much wider but longer contact patches that have much more grip available.

also with such a massive reduction in weight there is going to be effectivley less mechincal griip available so it will be important to make it up aero grip. a similar principle to why the nissan gtr is so heavy - there is a good video on youtube from pistonheads.co.uk who interviewed the head engineer on why the car was so heavy.

i can't wait for this thing to be done. gonna be awesome!

are you going to do a fastback?

[bruce]

Top Gear magazine did a little write up on the Chapparal on their backpage a while ago. A truly ugly but effective machine.

[little decks]

if you are also getting rid of the boot flooring then why not use some shrouded thermo fans and run active aero like the old brabham f1 cars to add some downforce.

Jim Hall originally did this with his chapparal 2J in the Can-Am series back in the late 60s or early 70s. The size of the fans and the power required to run them meant using a separate engine (out of a snow mobile) to run them, and that was with the plastic side seals aroun the bottom of the car. It is also pointless to have this with a rear diffuser and undertray as you will just be creating low pressure between the car and undertray.

I think for the speeds you will be doing you don't need to get too carried away with aero. A good front splitter, rear diffuser and rear wing would be enough. With anything under 200 rwkw you would want too much rear wing either.

you would obviously have the fans sucking air between the floor and the road. if ferrari are doing it on the 599xx with no side skirts i would dare say it is effective.

i think you would want as much aero as possible as with the lower hp as you need every advantage you can get. not to mention that only running 225 section tyres on 15inch wheels and running up against cars with 265 section tyres and much larger wheels which have not only much wider but longer contact patches that have much more grip available.

also with such a massive reduction in weight there is going to be effectivley less mechincal griip available so it will be important to make it up aero grip. a similar principle to why the nissan gtr is so heavy - there is a good video on youtube from pistonheads.co.uk who interviewed the head engineer on why the car was so heavy.

i can't wait for this thing to be done. gonna be awesome!

are you going to do a fastback?

I agree you have less mechanical grip. But you don't require as much grip to accelerate a smaller mass.... F=ma

Once again, even if you are sucking in the right spots (which you wont be of the fans are mounted where you suggested) retro-fitted radiator fans would be as about effective as using a go-kart to tow a car trailer.

I think your mate over at Nissan is trying to make excuses for an overweight car. Lets face it... the best way to go fast is with as little weight as possible. The GTR is heavy because of its drivetrain, its not like they have made the floor out of lead to achieve higher mechanical grip. I think you are forgetting that more weight means slower accleration... once again F=ma... you would think Nissan would still want their car to move off the line, and i would imagine they invisaged the car being able to stop at a decent rate. But most importantly... why would a car company in this day and age, with all the hype about reducing emissions and whatnot, intentionally make a car that is heavier than it needs to be and hence substantially more inefficient.... not to mention the fact that the extra weight puts more load on componentry, the GTR has a notoriously fragile gearbox no doubt partly contributed to by the weight of the car ( I will concede it also has to do with them going for a cheap option on their complex gearbox and associated systems).

I think that lightyear is looking at the best sort of aero package for his car because it won't have alot of straightline speed when it is immediately built, hence you add bits that move the air efficiently around the car, stop it from going where you dont want it and creating some downforce but with minimal drag. If you go all out on trying to create as much downforce as humanly attainable without having access to expensive resources like a wind tunnel or CFD programs you are likely to upset the balance of the car by shifitng the grip too far to the front and creatng oversteer or the opposite effect.

Your point about the tyres is slightly misguided. The only dimension substantially relevant to contact patch is width. Tyres are afterall circular in shape, so the contact patch is where the road (tangent) meets the edge of the tyre (circle) in theoretical mathematics the diameter of the circle wont give the tangent contact over a longer distance, it only ever touches at one value. Granted that this is theoretical, and the tyre is not a fixed circle, so it has some sag in it, however tyre pressures and alignment settings (camber) have a greater bearing over contact patch than diameter.
The width is a slight disadvantage, however the extra weight the cars with more witdth may carry is often the greater disadvantage.
There is quite a large advantage you get from the smaller diameter wheel though. Due to the car being at a power disadvantage as well as weaker componentry in the driveline the 15"s reduce the load, as they give the driveline a better mechanical advantage, which also incidently gives the car better acceleration. I know from when i was with Dad at Phillip Island, when he was driving in the 1 hour with David from Mania... the black turbo car broke 2 axles across the weekend probably due to the combination of around 220rwkw at that meeting with 17" wheels with 245 Michelin slicks on the rear.

Sorry for the novel of a post, I just enjoy discussing this kind of stuff

[lightyear]

Great post, someone who sees it from my perspective. Wider tyres add weight and friction. Larger diameter wheels are not only heavier, but the majority of the weight is in the hoop not the spokes so the weight has been extended further from the axle making it harder to spin up and slow down. If you keep going bigger in your width, there will be a point that your laptimes will start to slow. Unless you keep adding more power. A lighter car can change direction easier, takes less fuel, there is less tyre and brake wear, etc.
The aero is obviously something that will have to be worked on once the cars get on the track to get the balance right. So we will start with splitter, flat floor diffuser, decent rear wing, skirts, etc.

[lightyear]

Cage is in, looks good. The guys at meridian did a great job.