Turbocharger vs. Supercharger - what’s the difference?
I got asked this the other day, and after fumbling through my answer, I thought I’d better do some research. Having completed said research, I am ready to impart my new-found wisdom to the masses…
Basically, both turbochargers and superchargers do the same job - delivering compressed air to the engine. Why? Because if the air is compressed, you can get more in, and if you get more in, the fuel burns better, and if the fuel burns better, the engine goes faster. Make sense? Good. Here’s the key difference then:
A turbocharger has a turbine that is fed by the exhaust gases of the engine. These gases cause the turbine to spin, which powers the compressor.
A supercharger is belt driven by the engine.
Because of these differences, a turbocharger becomes more effective as the engine load increases. This is why you get a sudden burst of acceleration in turbocharged cars at about 3,000 RPM. This also has the added benefit of being more fuel efficient. The downside is the turbo lag issue.
Looking at my car as an example, which is a Fiat Coupe 20V Turbo, it generates 220BHP. The normally aspirated (or none turbo charged) version generates 154BHP. That’s some difference that the turbo makes! If you are driving at low RPMs and the turbo isn’t fully effective, then you can see that the performance gap is pretty huge. Simple solution: if you want to drive fast, keep the revs up.
The supercharger is connected to engine speed not engine load. The faster your engine is running, the faster your supercharger will run. The benefit is that you don’t have to build up exhaust gas pressure to get the supercharger going - it’s always on. So the upside is no turbo lag. The downside is the increased fuel bills, but then if you can afford the average modern car fitted with a supercharger then fuel bills probably aren’t much of a concern.
The two chargers sound different too. A turbo whistles as the engine revs pick up, whereas a supercharger makes a distinctive whine that is ever present.
I’m no mechanic, so if I have anything wrong, please submit your corrections below.
Hi David
Most of what your saying here is correct!! Engine efficence is controlled by a factor called “swept volume” this is the ability for the cylinders to fill with air and fuel at the correct ratio “Please note this ratio has to remain correct at all times failing to do so will result in melted engine components” The “swept volume” of an engine decreases as the rev’s increase due to the fact the valves are opening and closing more quickly but the air still takes the same time to move from a stand still and fill the cylinder. This is where the forced induction unit’s help greatly be it turbo or supercharger by creating a positive pressure in the inlet system the engine becomes much more efficent at filling the cylinders with the correct ratio of fuel and air and therefore deliver’s much more power. I have both Turbo “Lancia Integrale” and supercharged “Lancia Beta Volumex” the supercharged car will deliver enough power to force you into the seat in any gear at any RPM “Third gear from around 1200rpm being my personal fav” The turbocharged car on the other hand requires much more attention and makes alot more heat under the bonnet..
Hope this help
Craig
P.s Incase you hadn’t guessed I am a mechanic
Thanks Craig. Nice bit of extra info there.
can you fit a super charger on the non turbo version of the fiat coupe 20v 2Ltr?
cheers
mario
Yikes, that would be fun!
I can’t see why not, although space under the bonnet will probably be the limiting factor. You might need to upgrade the cooling system, and depending on the power output, you might need a heavy duty clutch and up-rated brakes.
Good luck!
if i was running a twinturbo with two wastegates would this be better than a supercharger
Hi Stephen,
You don`t specify petrol or diesel eng.Turbo`s generate much more heat than superchargers,and require intercoolers,dump valves etc.They are, though very suitable for diesel engines as they have a much narrower operating rev. range and thus heat is not such an issue.
Superchargers are used where more power is required and fitting a larger engine is not feasable,small car/big engine makes for unbalanced car! If it will fit,it will leave less room underbonnet for heat dissipation.
You have to decide what you require; 1/2 decent fuel economy & a burst of power higher up the rev. range. or Torque that will catapault you out of corners like no turbo could ever do!
Supercharged engines have excellent fuel efficiency on cruise as the supercharger requires little effort to keep it spinning at constant speed, heavy accelleration however and they drink fuel like a stag night go through booze. Lag is often quoted on turbos and is often as a result of poor design or bad bolt-ons (e.g. poor popping wastegates etc), proper design of the exhaust feed to the turbo and intake feed from the turbo greatly reduces lag, other addiitons such as water injection can almost fully remove it for little financial outlay.
As for the Fiat, better to fit the supercharger to the turbo car (not the standard non-turbo - boom!) and do away with the turbo, more torque throughout the rev range and generally a supercharged engine you don’t need the red-line so much as peak efficiency is wider and much lower, variations on the pulley size and therefore drive speed of the boower can also be used to up the power to be slightly higher than the stock compression (synth oil would be a good idea though!). Also the motor is already built for the extra compression and all the blow-off valves can be re-used in the new manifolds as well as the ECU won’t care and can handle the change well (mine did and it’s niiiiiiice).
Stay well
Steve
Thanks Steve, that’s great info. Supercharged Coupe - why didn’t I think of that? Alas my Coupe has now been sold so I will have to stick to my bikes for insane acceleration thrills.
supercharging my 20v fiat coupe na . . . this is something im seriously interested in doing. any advise? where would i start? what supercharger would i use? are there “bolt on kits” available.
sorry to sound a bit ignorant to this.
cheers!
mario