Time Attack Project

[brysport]

Hi guys,

I have been designing parts using solid works for the last few years, including an open top bike engined sports car (still not finished) but have started on a new project for a Time Attack car. I haven't been surface modelling for long so still very much an amateur, but I'm looking to do some CFD runs but I don't have the knowledge or software to be able to do this, so looking for some advice. I'd love to finalise the standard shape and then be able to run comparisons. I want to be able to try lots of different things, so any help would be greatly appreciated.

The reason I'm taking on this project is that I think there is a loophole in the rules (here in Australia) whereby I can run a super light car on the same size tyre as the heaviest car. So my design for a Suzuki Cappuccino that can weigh 588kg can run on the same 295 width tyre as the last winner, the 1000kg+ Mitsubishi Lancer EVO.

With the right aero and much less power, it should be possible to beat these cars, or at least give them a scare!

[andylaurence]

What engine are you fitting to drag that aero pack around? The standard engine wouldn't get that to 100mph!

[kosioBG]

if you have designed it with solidworks, it's best to use their built-in flow simulation, it also offers bulk simulations, where you can test different designs and compare the results. pretty cpu intensive though.

[brysport]

What engine are you fitting to drag that aero pack around? The standard engine wouldn't get that to 100mph!

At this stage it looks like the G13B from the Suzuki Swift GTi. These engines only weigh 54kg dry and with some forced induction and a stroker kit should be able to increase capacity to 1.5 (these engines don't take too kindly to boring, hence stroking) and should be able to push 300 - 350hp relatively easily.

The main thing is to keep the weight down.

I really need to look at the objectives of the project (i.e - power/weight, drag, downforce and work out the lap time I want to aim for and work back from there). I just get excited creating in Solidworks... I know it's not a good way to be!

[MadMatt]

You would need to double that power in order to go fast enough to need that downforce, as andylaurence said.

[andylaurence]

I wouldn't say you need double the power at all. It all depends on the track. For me, drag is entirely unimportant at Crystal Palace and the only important thing is getting downforce. That car would be fine with the standard engine! At Castle Combe, I back the wing right off as there's a half mile straight and I can lose seconds from too much drag. You can do some simulation to see what sort of drag/downforce is optimal for the tracks you visit. Work back from your objectives to design the car, rather than designing the car and hoping it meets your objectives.

[TurboLag]

This is Eastern Creek Raceway, and 350 hp would leave you eating ALOT of dust.. I do agree you should be able to keep up with a few of them in the low speed corners, but you should not underestimate the cars with aero by Andrew Brilliant. Under Suzuki/Scorch Racing and Tilton Interiors are beasts! Even though TI is not by Andrew Brilliant.. 350 hp would leave you trailing..

[AnthonyG]

Can't fit a rotary engine from an Rx7 and tune that up? (i think thay can be tuned to +500bhp with ease)
On the other hand, I feel you might be shooting yourself in the footstarting with a cappuccino...

[MadMatt]

Once you have fixed your engine power, you need to workout your aero needs, that's the way to do. Not the other way around. You can use OptimumLap to help you a bit in this task if you have a rough idea of your aero values and engine needs.

[TurboLag]

I don't mean to sink your idea for a lightweight time attack car, I've got a project of my own. 1994 Miata, SR20VET, big aero made in a wind tunnel by an aero engineering student. It won't be the fastest thing in the world, but you got to have enough power to drag a big frontal area through the air. Mine gets in the 800-900 whp range to do this..

[brysport]

I don't mean to sink your idea for a lightweight time attack car, I've got a project of my own. 1994 Miata, SR20VET, big aero made in a wind tunnel by an aero engineering student. It won't be the fastest thing in the world, but you got to have enough power to drag a big frontal area through the air. Mine gets in the 800-900 whp range to do this..

Well it looks like I have a lot to work out! Realistically I need to work out the details before I progress any further. Great to be getting this feedback.

[dandfx]

I'd speak with the time attack organisers first, sure it would be great to exploit a loophole but building it all up then failing the scrutineers check would make it all a waste.

Maybe give 101 Motorsport a call, they are achieving awesome times with low power in their CRX on the approach you plan, they are competitive in their class but not really giving the big guys a scare like you plan.

I can see your motivation and theory but Eastern Creek is a power track, aero and weight are big factors but getting down the front straight quickly is also very important. Here in Brisbane (lakeside) a local Silvia driver can match corner speeds with $50k+ evos but has a 20km/hr lower top speed on the straight which makes a pretty large difference in lap times.

Also, wider tyres isn't always better. Nitto tyres USA was testing product with the Toyota 86 (stock standard) and they had better times running 235 all round over a 235/255 combo.

[matt21]

Could you share the rules with us?
MAybe we can help in interpreting this loophole.

[NoDivergence]

I'd speak with the time attack organisers first, sure it would be great to exploit a loophole but building it all up then failing the scrutineers check would make it all a waste.

Maybe give 101 Motorsport a call, they are achieving awesome times with low power in their CRX on the approach you plan, they are competitive in their class but not really giving the big guys a scare like you plan.

I can see your motivation and theory but Eastern Creek is a power track, aero and weight are big factors but getting down the front straight quickly is also very important. Here in Brisbane (lakeside) a local Silvia driver can match corner speeds with $50k+ evos but has a 20km/hr lower top speed on the straight which makes a pretty large difference in lap times.

Also, wider tyres isn't always better. Nitto tyres USA was testing product with the Toyota 86 (stock standard) and they had better times running 235 all round over a 235/255 combo.

I don't know if you followed 101 last year, but they had a lot of troubles that if resolved, would have them to the front of their class easily. As far as I know, they were the only ones flat through turn 1

[wesley123]

Could you share the rules with us?
MAybe we can help in interpreting this loophole.

I assume the TS was talking about the WTAC

http://www.worldtimeattack.com/rulebook ... _Rules.pdf

The rule regarding the weight is

Minimum weight for Pro Class will be determined by the manufacturer's original specifications for the lightest version of that particular model of vehicle, minus 20%. Eg. Mitsubishi Lancer Evo 9 not merely Mitsubishi Lancer. Vehicles with original weight exceeding 1500kg will not apply the 20% rule but will have a minimum allowed competition weight of 1200kg.

This does not generally define a minimum weight limit, only a 20% under the base model's weight with all the required liquids + 5 litres of fuel.