Teachings from the Track

 

Every track day is a learning curve, to an extent. You’re either learning the track better, learning where to shave off a few tenth (or hundredths if you’re that good!), learning more about your chassis or suspension setup or learning how your latest tinkerings have affected the latter.


This outing was no exception. We’d experienced several trackdays with a fully aligned, corner weighted Mk1 MX5 (Schfifty) running Toyo CFsomethings at equal pressures and with average (but even) wear. Schfifty had suffered several setbacks in the braking area due to a number of issues that we’d been fault finding for a few weeks. Excessive heat seemed to build up in the rear left calliper, resulting in a delaminated EBC Yellow and a host of other arduous fiddly jobs, punctuated by what seemed like a million fluid changes.


Above: Schfitfty rocking its new GV style lip spoiler.


Finally a complete bleed with Comma DOT 5.1 and a ‘reconditioned’ used caliper still heralded a bag of problems, illustrated no better than by it smoking after a few opening laps. Something was clearly wrong.


Aside from this, however, Schfifty’s handling was about as good as the chassis, suspension, tyres and weighting would really allow. Even during aggressive cornering she exhibited no sign of understeer and gave a graceful, forgiving and controllable oversteer as you’d expect from a well balanced FR chassis.


‘The Jizza’, my newly dubbed Wu-Tang inspired lowrider certainly wasn’t fazed by some track hustle, and before long Adam was systematically working through the pack of other MX5s who were out that day. His experience both at Blyton and behind the wheel of an Mk1 meant I wasn’t really competing, or at least that was what I was telling myself.


Above: The Jizza, having its wheel put back on.


On Track

Braking


Only nights before she’d been treated to a full bleed with DOT 5.1 and a set of EBC Greenstuffs – the most reliable EBCs we’d found up to now though hardly ideal. The brakes were sharp with the bite point a little higher than it had been making heel/toeing a little more difficult than it had previously been.


Despite this, the brakes still consistently overheated when given more than a little hammer. We both needed to practice ‘brake management’ in order to maintain a safe operating temperature. In some cases this meant not trail braking into a corner and trying to get the braking done as accurately as possible within short, sharp bursts; sometimes it’d mean not braking into a corner at all and using a ‘controlled’ four wheel braking drift method to reduce speed mid corner without using the brakes, though this didn’t do our exit speeds much good. In large however it just meant knowing the braking zones and estimating the extra heat incurred by a second or two of heavy braking.


The window of grace between ‘effectively slowing the vehicle down’ and ‘total loss of braking power’ seemed to be minimal with the Greenstuffs, varying from a quarter second of warning to an almost instantaneous transition into the ‘terrorzone’, desperately clutching at the handbrake and decelerating through the gears to avoid the crash barriers and fields.


Our theories around the braking zones on Blyton came down to:


a) Blyton terrorizes brakes through its lack of truly long straights. We didn’t even hit 5th gear in a car with a notoriously short gearbox. Brakes don’t really have a chance to shed much heat due to the reduced airflow.


b) Blyton isn’t actually that bad on brakes. The lack of long straights and relatively low speeds mean with careful management of the brakes it’s possible to keep brake temperature under control, with only two really major braking zones, especially on the East Circuit.


c) On faster tracks, brake overheating will only be exacerbated.



Conclusion: Bigger/more efficient brakes will be needed if I’m aiming for the stars in terms of power. Which brings us to the next subject:


Power Delivery


Schfifty, by comparison to The Jizza, has a much racier engine with a sweeter, freer flowing decatted exhaust. A rebuilt head, some basic porting and a modest skim makes it significantly revvier and increases mid range torque by a noticeable amount. Round some of the tighter corners, especially in 3rd gear, the Jizza (completely stock) engine seemed to bog down significantly, especially when the revs caught up with the deceleration of the vehicle. This resulted in a much slower exit speed than we knew it was capable of.


Later in the day we incorporated a few swift heel/toe downshifts into second gear to get around especially K7 and even the Ushers-to-Twickers switchback (see map here). In a 13b, especially as the porting gets wilder, the powerband shifts further and further up the rev range. Bigger power often requires a port which creates more overlap between the inlet and exhaust. While creating bigger power and a faster revving engine, this porting approach can starve mid-range torque and requires the engine to be driven hard at the higher end of the rev range in order to get the most out of it. 


Above: Adam putting the hammer down through Bunga Bunga. 


I’m not scared of revving the bo**ocks off an engine, but through some of the tighter sections it would have been nice to leave the car in 3rd and concentrate on the corner. A minor point, but one to think about.


Handling


The Jizza has a power rack which has been de-powered, presumably to free up engine power and increase feel from the front wheels. While the intentions are laudable, in practice I found it a pain in the a*se, with the steering even heavier than a regular non-power rack due to still having to pump fluid around. For the most part this is totally acceptable, and during normal track conditions this gives a positive and visceral feedback, leaving you without question as to what the front wheels are doing.


Above: We'd forgotten that we'd even fitted our recon'd arms on the day. These will be going on sale VERY soon.


Nearer the limit, however, the story is different. Trying to counteract oversteer at 75mph needs some serious work. I’m no weakling, but wrestling an ugly, sideways, overcooked 4-wheel braking drift without the precision and finesse of a power rack is tougher than I personally think it should be.


I learned to drift in an E36 with a modest power rack which wasn’t overbearing, I still knew exactly where the wheels were and I loved the surgical precision it allowed – freeing up space in your mind to concentrate on feathering the throttle and watching out for police cars (JOKE!). 


The jury is out on this one, though I may dabble with reconnecting the power rack.


As far as chassis balance, the Jizza suffered from understeer that Schfifty simply doesn’t. Reasons we deduced include:


a) Lack of proper 4 wheel alignment and balancing. To the eye the rear wheels have a bit more camber than the front. Although this is standard for a race car, back wheels gripping more than the fronts will lead to understeer.


b) Tyre pressure. We both tragically forgot to bring a pump/gauge and couldn’t check if the pressures were even. We tested this by switching over the wheels half way through and it made literally no difference.


Dialling this out is crucial. The 13b weighs a svelte 260lbs (approx), around 20lbs less than a fully dressed 1600 Mk1 engine, and understeer will only become more pronounced.


Finally, our uprated front upper wishbones held out no problem. Combined with a heavy dose of daily fast road usage on Sheffield’s ‘roads’, they should be more than capable of making an ideal replacement for worn OEM ones. We’re already putting some of this footage together into a short ‘advert’ type thing to show some of the highlights.


Now it's time to take the Jizza into the workshop for the winter and start pulling her to bits.


Special thanks to: Mazda On Track for a really well organised and safe day out, and Blyton Park themselves, for letting us razz around their track.



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