In a low powered econobox like the Mazda2 having a little more power is always useful but obtaining it can be exceedingly expensive. So how can power be gained for free?
Well by changing how we look at power. Instead of taking a peak power figure as the goal and increasing from the original stock figure, work from power per ton. Because I'm writing this from home in England I'm going to be using BHP per ton as my standard unit. Should you need a conversion chart to help there's one right here.
1 BHP metric = 1.174HP American
= 0.75 Kw Australian
So what's the difference between peak BHP figures and BHP/Ton? Simple, the power figure of a BHP/Ton calculation can be influenced by the reduction of weight.
Weight is the enemy of everything automotive. It simple adds inertia which requires greater forces to influence change in its state. A heavy car with a traditional internal combustion engine will ordinarily accelerate slower then a lighter car of the same power. Electric motors do overcome this through witch craft, magic pixie dust and instant maximum torque. Since I don't own or race an EV I'm going to ignore them.
Weight doesn't just affect acceleration. it has an impact on stopping distances, turning, fuel economy, tyre wear, brake wear, cabin noise, comfort. The list goes on.
I believe it was Colin Chapman who famously said "simplify and add lightness". If that's good enough for Lotus its good enough for me.
For example. Stopping the car. By reducing the overall mass of the car the brakes don't have to work so hard meaning, when simplified, you have effectively scaled up the stopping power of your standard brakes.
Coming to my 1.5 Mazda2 sport built at the factory back in 2010. It's currently running stock power so should be 102bhp at the flywheel. Having been driven over 120k miles with "ify" service history prior to my ownership and then being flogged around a circuit without ever having had an engine rebuild the exact figure could be as low as 88bhp at the flywheel. Because I like to keep things simple and to acknowledge some wear will have taken place I'm going to specify that my race car currently produces 96BHP. I will put it on a dyno for accurate figures at some point.
From the factory the 2010 Mazda2 in sport trim weighted in at 960kg. The mathematicians will see what I've done here.
BHP / weight is 96bhp / 960kg = 100bhp per tone.
The perfect starting point for this article.
At the point of writing this I have removed the minimum required to go racing. Figures rounded up to the nearest kg.
Front seats 38kg,
rear seats 14kg,
Carpets with underlay 9kg,
roof lining 5kg,
Redundant wiring 3kg,
Excess dash material 4kg,
All seat belts 11kg
All plastic panels 6kg
The standard battery 12kg
The 16inch wheels with tyres 65kg
AC pipe work 1kg
Radio, speakers and associated wiring 3kg
All air bags and wiring 5kg,
The stability controls yaw sensor 1kg
OEM steering wheel 2kg
Spare wheel 8kg
Jack and tool kit 4kg
Total weight saving = 191kg
If the car could be driven like this we would have a new bhp per ton figure of
96bhp / 769kg = 125bhp per ton which would make a huge difference on the race track.
Hopefully you'll note that this works out at a 1bhp gain per 10kg loss.
Sadly however the car cant be driven in this form so added back into the car is the following
Race battery 6kg
Fire extinguisher with brackets and pipe work 15kg
Steering wheel 1kg
15inch wheels and tyres 48kg
Electrical cut off switch 1kg
Race seat 6kg
Planted seat base 6kg
Seat rails 2kg
Side mounts 2kg
Race harness 2kg
Roll cage 50kg
Total weight going back into the car = 137kg
The new driving bhp per ton is thus 96BHP / 906kg = 105BHP per ton as we have saved just over 50kg Not a huge power increase but its an increase none the less.
If we were to add a driver to this equation the figure will change again. I'm going to use Joe who's returning to the team for the next round at Silverstone this weekend 21st May 2022. Joe is our Lando Noris, he's fit, healthy and sub 1.7m tall. When fully prepped for a race weekend he's weighing in at 60kg. So what I'm going to claim here is, by stripping all the weight out of the car we have saved the new mathematical measurement of one Joe.
Including Joe back into the equation we have a total BHP per ton figure which we use for class selection of 96bhp / 966 kg = 100bhp per ton. Right back where we started.
So what's the plan for the next race.
Apart from putting three of the teams drivers on a diet or at least banning the ice creams. What can be done to help reduce the weight of the car further.
The limit for our class with in the BRSCC Clubsport trophy is 135BHP per ton. As such we have scope to both increase power and reduce weight further if we want to. However, if we were to go down the more extreme route of tuning the engine and reducing the cars weight further we would be detracting from the ease building a competitive Mazda2 race car. With the aim being to host a complete grid of 40 mazda2s in the near future we must keep the cars simple to build.
With the future in mind by Silverstone I hope to have reduced the cars weight through removal of the following.
All sound proof matting 3kg,
Isofix mounting points 1kg,
Rear wiper and motor 2kg,
trimming down the internal door cards 2kg
Washer bottle system 2kg when empty,
hand brake cable cover 1kg,
That's 11kg so another horse power gained.
If we were to run the cars for all our performance the following options would be viable for removal.
Electric window mechanisms 2kg
AC compressor 7kg
Horn and wires 1kg
Door cards 3kg
Central locking 4kg
Door mirror motors 2kg
Headlight internals / blanks 6kg
Heat shields 2kg
heater matrix 5kg,
Entire dash 5kg
wheel arch liners 1kg
drill or honey comb all the interior metals 4kg
Following the above list and without spending money on lightweight replacements the maximum power you can hope to gain from a Mazda2, through weight loss alone is ...
96bhp / 857kg = 112bhp per ton
Should you wish to throw money at the car with the use of exotic light weight materials such as carbon fibre and Titanium you may be able to remove another 60kg bringing the BHP per ton to 118bhp achieved through weight loss alone.
Sticking with the 857kg weight in theory we could hit 135bhp per ton (our class limit remember) with an achievable increase of peak power form 96 up to 115. I say its achievable it would require an engine rebuild, a streamlined cold air intake, an exhaust system and a custom remap which is potentially £1000 worth of work. While this would be great for our class competitiveness its again not sticking with our cheap fun easy to access race series mentality.
So can power be gained for free? Yes if you look at the power gain in the right way. would you want to go down the weight loss route for your road car? yes, to some degree. Removing even the smaller items from the car and keeping clutter to a minimum will aid performance and fuel economy. On track its definitely worth it. Every small gain when added to a longer list of small gains adds up to significant changes over a lap and those are multiplied further when accumulated over the course of a full race distance.
For anyone interested in coming racing please do email me at email@example.com
Should you want to hire a race spec Mazda2 for a track day email me as above.
If you own a mazda2 and are thinking about trying your car on track there is a great opportunity at the Big Mazda2 meet at Blyton park 17th July with MOT track days. Lots of Mazda2 in attendance including the full 2Racing team. Go to our Facebook event for full details.
Race Team Manager