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Engine power is always extremely variable, in theory a new engine should perform to spec but if the exhaust or air intake vary from the original test set up and it has not been mapped accordingly then the figures will be way out.
If it managed 132 bhp new then at 200,000 it is probably a little less.
A decent 1.8 MX5 engine produces 175 BHP with ease once it's been treated to a properly mapped ECU and a set of throttle bodies.
Remember the huge difference between flywheel BHP and WHP (wheel horsepower), some say a 10% loss through the trans is average, some say more. One thing is for sure it won't be on peak if it is not fine tuned for your particular set up.
To work out your BHP per ton, call it 1000 kg, divide by the car weight, say 650 kg = 1.538. Times your BHP by 1.538 and you have the power to weight ratio. But then remember it is not all about horses, we have light cars, they slow down easier and go round corners with less forces acting against them than a top heavy tin top.
Torque is less important with light cars. An easy way to look at the torque v bhp is to consider torque as the pulling power and horsepower as the speed at which it can pull it.
Don't expect adding carbon fibre to make any difference, GRP is light too and we don't have a huge amount of bodywork!
If you want to go faster then try to avoid pulling in when you see a big yellow M sign for a few months and drive with your tank half empty, oh and empty yourself if you are keen on knocking a tenth off a quarter mile! I am much slower after Christmas than B4, no idea why ~_~