Julian Edgar, 50, has been writing about car modification and automotive technology for nearly 25 years. He has owned cars with two, three, four, five, six and eight cylinders; single turbo, twin turbo, supercharged, diesel and hybrid electric drivelines. He lists his transport interests as turbocharging, aerodynamics, suspension design and human-powered vehicles.
The weight changes caused by turbocharging and supercharging
Many performance mods add weight to a car, so reducing their real world effectiveness by at least a little. A big exhaust, a supercharger or turbo – all make the car heavier than it was standard. (Of course there are a couple of mods that make the car a tiny bit lighter – eg porting a cylinder head or lightening a flywheel – and there are other modifications that make no difference at all to car weight – eg increasing turbo boost.) But in general, even changes like bigger wheels add mass.
Recently I had the opportunity of comparing the weight gains made to a naturally aspirated car that was firstly supercharged, and then the supercharger removed and the engine instead turbocharged. How much weight was gained by each approach? The car was my first series Toyota Prius.
The blower installation involved the fitment of:
A supercharger support bracket, which in this case also replaced the function of the original cast iron engine mount…
…the supercharger – an ex-Subaru Vivio AMR300…
…a small air/air intercooler from a diesel turbo Pajero…
…and a GFB blow-off valve (used as a recirculation valve).
The turbo installation involved:
A fabricated thick-wall exhaust manifold…
…an IHI RHF4 turbo…
…the same blow-off valve…
… the same air/air intercooler and
…a new exhaust…
and much longer intake and intercooler plumbing.
The measured weights were rounded to the nearest kilogram. However – and it’s an important point – it’s no good just measuring the weight of the bits and adding them up. That’s because many of these components replace factory parts – and the factory parts may be heavier or lighter than the parts being used in their place.
So let’s look at it in the context of also subtracting the weight of the bits removed.
Supercharged:
| Modified Part (added) | Standard Part (removed) | Mass Change |
| Fabricated blower bracket: 3kg | Cast engine mount: 1kg | +2kg |
| Blower: 6kg | – | +6kg |
| Intercooler, Recirc Valve: 2kg | – | +2kg |
| Total Addition: | 10kg |
Turbocharged:
| Modified Part (added) | Standard Part (removed) | Mass Change |
| Fabricated exhaust manifold: 3kg | Factory cast iron exhaust manifold: 5kg | -2kg |
| Turbo: 5kg | – | +5kg |
| Intercooler, BOV: 2kg | – | +2kg |
| Exhaust: 15kg | Exhaust: 11kg | +4kg |
| Longer intake and intercooler pipes: 1kg | – | +1kg |
| Total Addition: | 10kg |
As can be seen, the total weight gain was the same, whether a turbo or blower was fitted. (Note that if a new exhaust hadn’t been installed at the same time as the turbo, the turbo conversion would have worked out lighter.)
But more important is that the overall weight gain in each case is completely trivial. The kerb weight of the car is listed at 1240kg, so the addition of 10kg represents lest than a 1 per cent increase in mass…
