Sprinting a Mygale M12 Ecoboost

[RicME85]

What's the reason for selling? Got another car lined up?

[andylaurence]

I only own half of it and the other half is for sale, so I'm out by default.

[Pierce89]

I only own half of it and the other half is for sale, so I'm out by default.

Man, that sucks. If the guy can't afford it, he should forfeit to you rather than forcing you to sell. Is buying the other half yourself out of the question?

[andylaurence]

Car shares always end with one person wanting out. I knew this when we bought it, so no problem. It's not possible to run the car alone; strapping myself in for starters...

[andylaurence]

The EgoBoost is for sale and that means the challenge of a new car, but which car? I'm heading for the roadgoing classes and top of my list is a Mazda MX5/Miata. The big question is whether it can be competitive. The class I'm aiming for is the 1800-2600cc roadgoing class and that's dominated by a Mini Cooper S that's reported to have 354bhp. So what do I need to do to beat that car?

I fired up OptimumLap, because it's a quick and easy laptime simulator that's free to use and ideal for wet finger comparisons. I looked up the specs of the Mini and ran a lap of Castle Combe Circuit. I know the car managed an 80.46 lap earlier this year. I could only find a dyno plot of a 275bhp Cooper S, so I ran a test lap with a friction co-efficient of 0.9, which yielded an 82.95. Upping the power to the suggested ~350bhp, the lap time came down to 82.36, but it was clearly having more wheelspin than the car really has.



I ran a sweep of longitudinal and lateral friction from 0.9 to 1.0. The time fell between 0.94 and 0.95, so I plumbed 0.95 in on the assumption that the driver's not perfect! Had we had any data from the car, this might have been a little less finger in the air. So what does the MX5 need? I plumbed in the figures, including a dyno chart from a 200bhp supercharged engine. The baseline time for the car came out at 82.05 in this spec.



Knowing the standard engine is limited to around 250bhp before needing forged internals, I ran a sweep of times from 200-250bhp and the 250bhp engine came in at 80.87. Half a second to find! So let's have a look at aerodynamics and see what time we can find. Drag appears to be worth less than two tenths from 0.34 to 0.40. Sweeping downforce from 0.1Cl (lift) to -0.5Cl (downforce) found 0.65 seconds, so clearly downforce is a worthwhile investment. 80.30 seconds was achieved with 0.38Cd and 0.38Cl, which seems achievable as a lift to drag ratio of -1. A look at a Mk1 in CFD yielded a reduction in drag and downforce of -0.49Cl.



Plumbing in 0.38Cd and -0.38Cl, let's have a look at the effect of weight on lap time. Sweeping weight from the standard 1130kg to 1000kg (with driver) brought lap time down from 80.3 to 79.8, a further half a second per lap saved. A more realistic weight saving of 55kg brought lap times down by 0.2 seconds. On that basis, it seems like the MX5 has the capability to beat the Mini, assuming the 350bhp is true. Let's go build a supercharged MX5!

[FoxHound]

Depending on budget, an S2000 or an Integra with a supercharger kit can be had for less than £10k.

Both with more potential the MX5, and both with easy bolt on performance parts.
There's a stoker kit for the S2000 that allied to a supercharger, will give you over 350bhp. The car itself can also lose about 100kg's of mass pretty easily, with a further 100kgs if you fully strip it out and add a carbon bonnet(12kgs saving there alone).

If you look at the suspension, there is a bevy of options, all in the MX5 ballpark too. A good set of coil overs can be had for about £900, and I'd recommend it, as well as brakes which will set you back £950 quid for discs pads and calipers(optional).
Standard, those brakes are fine and pretty much fade free for a 20 minute track session(mallory park).
But horses for courses, and with 350bhp, you'll want to stop predictably.

You'll likely need 17 inch offset wheels, Rota(fighter)do a range that are cheap and lighter than the standard 16inch wheels(marginally).
Your problem will come when it rains, as it will be tail happy. But an MX5 with 250bhp will suffer the same issue.

With this in mind, as well as the rules....could you run a 2.5 litre 400bhp Skyline for 8k?
http://www.ebay.co.uk/itm/1995-Nissan-s ... Sw9IpXxDn4

[bhall II]

Depending on budget, an S2000...

Quietly one of the best cars of the last 25 years. I think a late-model CR edition (factory stiffened, lightened, no AC, etc.) would be a great place to start.

[Pierce89]

Depending on budget, an S2000...

Quietly one of the best cars of the last 25 years. I think a late-model CR edition (factory stiffened, lightened, no AC, etc.) would be a great place to start.

Quietly? --- every racer i know loves those little revvers.

[andylaurence]

The S2000 would fit into the class above if supercharged, as would a Skyline. Class leaders there are going much quicker in 600bhp 911 turbos, Mitsubishi Lancer Evolutions and Subaru Imprezas. I don't want FWD so an Integra is out and I can't see it being much different to a 350bhp Cooper S but with more money to get there no doubt.

I'm reasonably confident in the MX5 and if it doesn't work out, then I'll switch cars next season.

[FoxHound]

Depending on budget, an S2000...

Quietly one of the best cars of the last 25 years. I think a late-model CR edition (factory stiffened, lightened, no AC, etc.) would be a great place to start.

We didnt get the CR or the F22C 2.2 (lower revs more torque) motor here in the UK.

Will probably be the best car I've ever owned (and still do)

The S2000 would fit into the class above if supercharged, as would a Skyline. Class leaders there are going much quicker in 600bhp 911 turbos, Mitsubishi Lancer Evolutions and Subaru Imprezas. I don't want FWD so an Integra is out and I can't see it being much different to a 350bhp Cooper S but with more money to get there no doubt.

I'm reasonably confident in the MX5 and if it doesn't work out, then I'll switch cars next season.

What are the criteria for the class?
The S2000 fits engine criteria as well as rear drive front/mid mounted engine.
The stoker kit will push you up to 2.4 litres but bag you an extra 30bhp and 50/70nm torque.

[andylaurence]

1800-2600cc. Supercharging is a 1.4x multiplier, so equivalent to 2800cc on a 2000cc car.

[bhall II]

Quietly? --- every racer i know loves those little revvers.

Nearly every S2000 on the road in NJ is either riced out or is clearly the centerpiece of a mid-life crisis starter kit. Consequently, they're not particularly beloved outside those demographics.

The quintessential driver's car, I think they should be the subject of poetry.

[FoxHound]

The quintessential driver's car, I think they should be the subject of poetry.

Not quite poetry, but....

Our s2k, who art in Suzuka
Hallowed be thy exhaust music
Thy modifications come
Thy will be done, in JDM spirit as it is Japan
Give us this day, our daily 93-octane
And forgive us our speeding tickets, as we forgive those who rev against us
And lead us not into street racing
But deliver us from snap oversteer.
For thine is the vtec , the unicorn power and rpm glory
for ever and ever

Amen

1800-2600cc. Supercharging is a 1.4x multiplier, so equivalent to 2800cc on a 2000cc car.

I assume you are looking to run a 1.8 MX5. How are you going to attain the power gains, Supercharging?

[andylaurence]

Yes, I've bought a supercharged MX5.

[FoxHound]

Yes, I've bought a supercharged MX5.

Nice,

If I may....What model year have you bought? And has the cars suspension been uprated?
Seen a few of these cars at track days, and they're spirited.

But if you are gunning for a 340bhp Cooper S, you gonna need some dynamite. How are you going to achieve this type of gain?