MR2 Super GT Race Series for 2010

[monkeyra]

Brilliant, thanks for the overview. Gives food for thought

[dave5526]

Sounds exciting, if my 2gr conversion is finished in time I'll be entering (cost permitting)

[Rogue]

Sounds exciting, if my 2gr conversion is finished in time I'll be entering (cost permitting)

Excellent - we already have someone planning a 2GR entry. I think they'll be really strong competitiors.

[Neil_turbo]

sounds fantastic

definately something to consider enabling track cars to be taken to the next level!

Will be waiting for the safety regs before commiting to which roll cage now

[Rogue]

That is some impressive car. Not poverty spec exactly.

Yes! Far from poverty spec, but you could realistically achieve the same level of performance for a lot less money. This car is also destined to compete in some endurance races so a lot of attention has been paid to oil control and cooling systems.

Here's me having a go in Simon's car for the first time:

http://www.youtube.com/watch?v=qWBJXEIEsvw

Simon raced his car in an all-comers race last weekend and as expected it was head and shoulders above the normally aspirated MR2s - in the region of 4+ seconds a lap quicker! Simon broke away from the pack with the leading group of five SR & GT cars finishing 9th overall.

[System-G]

It's a shame we didn't make it. Looks very impressive.

[JeffD]

Patrick - what camera setup do you use in those cars? quality of the image is superb - particularly for youtube.

[Rogue]

Patrick - what camera setup do you use in those cars? quality of the image is superb - particularly for youtube.

I'm using a Sanyo Xacti HD800 for the forward facing footage and a HD700 for the rear (they're both essentially the same camera, one has a couple of extra functions). Both record in 720p high definition to an SDHC card.

I've been extremely impressed with these cameras - they're badged as hybrids and take 8mp stills with flash as well. There are two buttons on the back - one to record video, the other for stills. You can pick up the HD700 at the moment for as little as £135!

[JeffD]

Any preference for one or the other (other than price)?

Just had a quick google and the 800 is

Sanyo Xacti HD800 £170

http://www.dslrcamerasarena.com/sanyo-x ... order.html

and the 700 £134

http://www.camerabox.co.uk/product1.asp ... 5QodhBz7Ig

How do you attach them to the car as they seem an odd shape - any chance of some pics/detailos of the setup? Also, whats the max practical recording time for one clip?

[Rogue]

I use a Super Clamp with Stud and Tripod Head from the following page:

http://www.fastfilms.co.uk/fixed-camera-mounts.php

It clamps on to my roll cage, gives me maximum flexibility and is (normally) rock steady! I've just checked one of my videos and 23 minutes of 720p footage used about 1.5GB. I use 8GB cards as they were the best value for money when I bought them but the SDHC standard supports up to 32GB. The mounting point on the bottom of the camera is the normal industry standard for tripods etc.

I've not really put it to the test, but my initial impression is that the HD800 gives better stills than the HD700. In all honesty I only purchased the 800 to top-trump a friend who'd got the 700!

[Quigonjay]

whats the battery life in one of those?
i only get about 3 hours out my pvr

EDIT: says 55 mins recording time on one of those links, surely thats not right?

[bri0905]

Patrick,

How will it work for weights then? Will you have a weigh in before lining up on the grid so you can work out the power to weight? Or will it be worked out after the race?

I'm interested in more info on this please?

Bri

[Rogue]

How will it work for weights then? Will you have a weigh in before lining up on the grid so you can work out the power to weight? Or will it be worked out after the race?

This is where it starts to get a bit clever...

The Race Technology Analysis software is capable of taking the data that we collect using the DL1 Datalogger and - along with some other supplied variables - working out how much power the car used at any given point on the circuit. The other variables are the vehicle's weight, it's co-efficient of drag multiplied by frontal area (CdA) and rolling resistance. Ignore the last two variables for now and just concentrate on the weight. The datalogger provides data about the vehicle's rate of acceleration, which given an accurate vehicle weight can be used to calculate the amount of power was used. Since the regulations work on a power to weight basis (bhp per ton) what we actually want to extract from the data is the amount of power used to accelerate the vehicle if it weighed 1000kgs. We can therefore simply enter a vehicle weight of 1000kgs into the analysis software and if the car has exceeded it's power to weight class then the power figure produced will be too high.

Simples.

[bri0905]

So the driver will supply the weight of the car with him/her on board and fuel and if the data logger does not tally with what's said they'll be checked and penalised accordingly??

[Rogue]

So the driver will supply the weight of the car with him/her on board and fuel and if the data logger does not tally with what's said they'll be checked and penalised accordingly??

No. At the end of a race, data cards will be collected from all cars in Parc Ferme, and then run through the analysis software on a laptop using a default weight of 1000kgs. This will give us the peak power figure for each car if it weighed 1000kgs which is essentially the car's power-to-weight figure. We don't need to know what a car weighs - just what it weighs in relation to how much power it has.

[bri0905]

Sorry, i'm still not following, i thought you'd need to know the weight and power of each car to categorise them?

I'm sure you understand it, maybe i'm just a little slow

[kaiowas]

Sorry, i'm still not following, i thought you'd need to know the weight and power of each car to categorise them?

I'm sure you understand it, maybe i'm just a little slow

If you want to work out the actual power of the car then you need to know it's weight. In this case however we only need to know the power to weight ratio without necessarily needing to know the actual power and weight figures. Power to weight can be derived purely from acceleration data as follows

Here comes the science bit.....

Starting with some basic physics:
force = mass x acceleration (or f=ma)

Plus standard principle of moments:
torque = force x length

Combine the two and you get:
torque = length x mass x acceleration

Applied an accelerating car you're basically saying that Torque at the wheel =Tyre radius x vehicle mass x rate of acceleration

Now looking at the relationship between torque and power:
Power = Torque * rpm * constant

The 'constant' is just a known number which varies depending on your chosen units for power and torque. In the case of a road wheel you can say that:
Vehicle speed = rpm * pi * 2 * Tyre radius

Rearranging gives:

rpm = Speed / (2pi x Radius)

Substituting into the power equation and rearranging:
Power * Radius = (Torque * Speed * constant/2pi)
Torque = (Power * Radius) / (Speed * constant/2pi)

Bringing back the equation from earlier as applied to a road wheel:

Torque at the wheel = Tyre radius * vehicle mass * rate of acceleration

Then:
(Power at wheel * Tyre Radius) / (Vehicle Speed * constant/2pi) = Tyre radius * vehicle mass * rate of acceleration

Tyre radius cancels out:
Power / (Speed * constant/2pi) = vehicle mass * rate of acceleration

Rearranging:

Power / Mass = Acceleration * Speed * constant/2pi

Power/Mass is power to weight ratio so:

Power to weight = Acceleration * Speed * constant/2pi

As the speed of the car at any point can be derived from the accleration data based on a known starting condition (Zero speed on the grid) then theoretically you can calculate a vehicles power to weight ratio based purely on accleration data and known constants. Strictly speaking the race system doesn't *need* CdA and rolling resistance data but I guess it's used to give a 'second opinion' as basing speed purely on the acceleration data will give rise to significant cumulative errors over the course of a longer run.




Might have gone a bit over the top there but the same basic principle is used by those iPhone apps can calculate your Power output based on a 0-60 run and a weight (which you've usually guessed).

/Waits for someone to pick up on some trivial error in that lot somewhere

[Rogue]

I've just skimmed over what you put and without taking the time to check every detail it's clear that we're singing from the same hymn sheet!

CdA is important as a factor though, since it will affect the rate at which a vehicle can accelerate. If you consider that you had two race cars where everything was identical except the body shell and one was shaped like an arrow and the other shaped like a shoe box, the more aerodynamically efficient of the two would accelerate quicker.

Because of this, the arrow shaped car would produce a higher power-to-weight figure, despite both cars producing the same power figure on a dyno. For this reason, the class banding only loosely refers to power-to-weight and is more accurately referred to as a "Performance Index". For each of the three versions of the MR2 we have default figures for the CdA based on standard cars. Theoretically if you make your car more aero efficient than stock then you could have a car with 250bhp that weighed 1000kgs but with a Performance Index of more than 250. With me so far?

Of course, there is a way to take advantage of this system. Imagine that you put a comedy sized rear wing on the back of your car - this would increase the downforce generated but at the same time also increase the drag. More drag means the car is less aero efficient and in turn will come out at a lower Performance Index figure, meaning you could run more power or a lighter weight. This doesn't mean that the system of policing the series is faulty - since I'm being open about this fact, it gives everyone the opportunity to take advantage of it. Result - everyone runs with exciting looking race car rear wings!

The final factor is the rolling resistance of the tyres which is negligible for our purposes since all cars will be using the same tyre compound and similar sizes.

[bri0905]

I'll just have faith that you very clever guys have it all under control. I'm still interested in the possibilty of racing though so please keep us informed!

[Rogue]

I'll just have faith that you very clever guys have it all under control. I'm still interested in the possibilty of racing though so please keep us informed!

Lol! From a competitors point of view, you'll have a little black box that sits in the car with a memory card in it. At the end of a session on track you'll be able to stick the memory card into a laptop and run an analysis program. That will give you a number that represents your car's Performance Index. If it's higher than the class you want to be in (150, 200 or 250) then you need to lower your car's performance - either by adding weight, reducing power or reducing aerodynamic efficiency.

I imagine most people will make changes by either adding or removing weight, or on turbocharged cars by playing with the boost pressure.