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Supercharger vs Turbocharger


The debate about what is best for adding power - a supercharger or  turbo has been going on for an age but really there is no single answer, it depends on what fits your situation and intended application.


Turbo info from Garrett
Eaton Supercharger FAQ

Click on the images to be taken to Garrett and Eaton for more specific  information about Turbos and Superchargers

Back to basics

A naturally aspirated engine (or NA as it's commonly known) can only suck in a certain amount of air and this is dependent on it's capacity or size. We need fuel, air and a spark for the combustion process to drive down the piston and turn the crank so if we want to get more power out of the engine we either need to burn the fuel more efficiently or burn more fuel with the right proportion of more air.

Sure we can throw more fuel in quite easily with simple modifications but this won't neccessarily make more power, in fact it may make less as the mixture will be too rich unless it was extremely lean in the first place. We need to get more air into the mix.


To get more air in we could increase the capacity of the engine and stay in this NA configuration, or we could add more oxygen to the air with a nitrous oxide setup which can add reasonable gains on even a modest setup but this has it's own drawbacks.

Or we can go forced induction - force the air in under a compressed state, a Turbo or Supercharger are our choice of devices to do this, they compress the air increasing it's pressure like a big air pump so that we get more oxygen molecules into the same capacity engine cylinder. This compressing of the air will also increase it's temperature so we need to be very careful of this and take steps to cool it down and manage it.




Turbos are powered by the exhaust gases which turn a turbine, this spins a shaft that draws in air from the intake side and compresses it as it's spinning very fast.






A supercharger isn't connected to the exhaust, it has a pulley which is driven by one of the engine belts so is usually installed where the pulley can be aligned with the other belts - this alignment is critical.  Other setups that have been used are to have a shaft with a pulley on each end or coupling to the supercharger so that it doesn't have to be on the same side as the pulleys/belts.

In either case it's the fans or lobes inside the supercharger which compress the air so that it delivers air at a higher rate than atmospheric pressure.

So they are both like bit air pumps right just a different way of powering them?

Sort of but there definately are differences in their characteristics, how they perform and installation considerations in

general and on the Mitsubishi FTO.




Drive method - Turbo is more efficient

As a Supercharger is driven off the engine it takes a certain amount of power to drive it, this is lost efficiency but you do get power back when boosting. To take the load off the system a bypass valve is used for off-boost cruising which makes the system more efficient.

In comparison a Turbocharger isn't driven directly it's powered by waste exhaust gases so pound for pound (or psi for psi) a Turbocharger should in theory result in slightly more power than a Supercharger. The Turbo system isn't without it's inefficiencies though, there are interrupted exhaust gas flow, loss of back pressure and the extra heat that a Turbo puts into the engine bay.


Durability - Supercharger

The Supercharger is generally regarded on top here, expected times between overhauls are around 100,000 miles. The Eaton M45 has it's own enclosed lubrication system but even with these high service intervals I would recommend replacing the supercharger oil more frequently in an FTO Supercharger setup due to over-running the supercharger (running it past it's normal recommended operating RPM).


Lag - or lack of with a roots type Supercharger like the Eaton units

Boost is available almost immediately on the FTO Supercharger setup, as soon as the throttle is opened and the bypass valve closes in fact.

In a turbo setup you have to wait for the turbos to spool or use small turbo's that spool quickly to get boost low down and this can then see a trade off in top end power.


Installation - it used to be close but it's now even easier to fit a Supercharger

Space is very tight in the engine bay as you're probably well aware so fitting a turbo or supercharger presents problems.

When fitting a turbo the power steering pipes and brake lines generally have to be moved, custom turbo manifolds have to be fabricated along with up and down pipes to the exhaust and with this being a V6 it's not all that straight forward. Heat wrap needs to be used in lots of places for shielding and plumbing of oil feed and return pipes for the turbo for lubrication also need to be done.  That said there have now been quite a few turbo conversions particularly in Australia and there is quite a lot of information on the fto australia forum.

Fitting a supercharger in the FTO engine bay does at first glance look to be a tall order due to lack of space but it has been achieved previously by a handful of dedicated enthusiasts but with long project build times.  
The good news however is that with one of our FTO Supercharger installation kits it's much easier as we've taken care of the research, development and fabrication of bespoke parts making it a job that can be completed in as little as a weekend with no fabrication skills required.


Overall power - Turbo

If you are chasing big power then a turbo or engine swap is the way to go. All of the big power FTO's to date have used turbos and forged internal engine components or engine transplants.  To get the same amount of power as a large turbo can deliver with a supercharger setup you would need a larger Supercharger than the M45, maybe an M62 Supercharger and the downside is that they take more power from the engine to run them and they are therefore more suited to larger displacement engines.  Forged internals would also be required to handle the increased stress on the engine (the same goes for Turbos chasing big power).

Our FTO Supercharger kits can still deliver between 6 and 9 psi of boost depending on pulley sizing and charge cooling setups and I would estimate that this should see somewhere between 240 and 270 horsepower given previous results.

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