Honestly, I see all this "May affect torque crap" all the time...
Scientifically and logically, when you look at it, the engine is only going to do what it can do. Think of lightened parts as the equivalent as putting a ball bearing turbo on a car, it's going to boost earlier because of the extra weight spinning and aiding the car. In an N/A car though, a lightened part is going to get up the revs easier and you're going to get in to your power band faster, there are no other variables. How in gods name does a lightened part REDUCE torque? It may reduce torque when you come off the throttle and back on as the weighted part is going to want to spin for longer, but how in gods name will that increase your torque either?
What you're trading off as torque for engine free speed you are NOT going to notice a power difference. You won't go faster, but you'll certainly get there faster. Besides, if you're going to lighten a component, the loss in torque, if I'm incorrect (because I know nothing) will not matter, because you'll need less torque in the first place because the car weighs less overall.
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R27SG Very rarely you are going to be doing 130MPH on a track mate, to be honest.
If I've totally missed the point, can someone more mechanically minded explain. Logically, I just can't see how it would make a difference. What's traded off, will be picked up elsewhere.
Although lightening any component is a MUST. Remove your back seats from your Clio and the ISOFIX bar which will come in around 22-30kg weight loss and you'll actually notice a difference.