Knowledge Boost:</br> Selecting A Supercharger
Centrifugal Versus Positive Displacement

Traditionally, when the term ‘supercharger’ is mentioned it evokes images of muscle cars with bulging Roots-style blowers climbing out of an engine bay and saying ‘mine’s bigger than yours’. Technology has evolved a long way over the years and this applies to the current crop of superchargers too.

For those not familiar with the inner workings, I’ll give a quick recap of the principle behind supercharging.

All things being equal, the power we can achieve from an engine is defined by the volume of air it can consume, and in a naturally aspirated engine this is limited by atmospheric pressure. It’s the difference between the pressure in the intake manifold and the low pressure created in the cylinder by the piston descending during the intake stroke that makes the air flow past the valves and fill the cylinder.

super-charger-high-performance-academy 4

A supercharger artificially increases the pressure in the intake manifold and this creates a larger pressure differential between the intake manifold and the cylinder which has the effect of forcing more air into the engine. Within reason, the more boost pressure the supercharger produces, the more air that can be forced into the engine and the more power we can potentially make.

When it comes to superchargers, our choice comes down to two options – centrifugal, or positive displacement – and in this story we’ll examine the pros and cons of each.


A positive displacement supercharger is probably what most people think of when they hear the term supercharger, as this is the type we normally see hanging out the bonnet on those muscle cars I mentioned. This type of supercharger displaces a fixed volume of air for each revolution of the supercharger, and if it’s moving a larger volume of air than the engine can consume, the result is positive pressure in the intake manifold.

Positive displacement superchargers can be further broken up into Roots-style and twin-screw. A Roots blower is the oldest form of supercharger and is still hugely popular in muscle car and drag racing (think of Dominic Toretto’s Dodge Charger). This type of blower, which is best thought of as an air pump, takes air in through the top and a pair of closely-meshing lobes pump the air through the supercharger body and out the bottom.

super-charger-high-performance-academy 6

A more modern take on the positive displacement supercharger is the twin-screw style which has a pair of intricately meshing lobes that look similar to screws. These superchargers take air in through the rear and compress the air as it travels through chambers that decrease in volume as they reach the outlet.


Centrifugal superchargers on the other hand are basically a belt-driven turbocharger. They use a compressor section that is essentially identical to that of a turbocharger but are driven via a belt instead of by exhaust gasses.

This type of supercharger relies on centrifugal force from the compressor wheel to accelerate and force the air into the engine. This requires the compressor to spin at very high speeds (30,000 to 60,000rpm), and to achieve this these superchargers include a gearbox to step up the rotation speed above what we can expect from the crankshaft.


So which is best? Why choose one over the other? Well, the ‘best’ option is going to depend what you want from your engine. Both have pros and cons and understanding these will help make your choice easier.

Let’s start with efficiency. When we compress air its temperature will naturally increase, however the amount of heat placed into the intake air will also depend on the efficiency of the supercharger. Heat is the enemy of power so the less we have, the better. Here a centrifugal supercharger is the winner, operating with superior efficiency over a positive displacement supercharger – particularly at higher boost levels. This means that for the same boost pressure the intake air will be cooler with a centrifugal supercharger and we can expect more power.


I will point out though, that the twin-screw style of positive displacement superchargers do offer vastly improved efficiency when compared to the older Roots-style, but they still typically fall short of a properly selected centrifugal supercharger.


Since I’ve mentioned intake temperature, let’s talk about intercoolers. An intercooler is included in the intake after the supercharger to remove heat from the compressed intake air. Intercooling a centrifugal supercharger is not much different to a turbocharged engine and a front-mounted air-to-air intercooler can normally be included without too much trouble.


A positive displacement supercharger installation can be a little trickier though, as often the supercharger is installed directly onto the intake manifold, or even as a part of the intake manifold. This is common with a ‘v’ configuration engine. This makes an air-to-air installation difficult, so a more common solution is to incorporate a water-to-air intercooler under the supercharger. These have the disadvantage of being less efficient than air-to-air and often the intercooler size needs to be compromised to allow them to fit.

Strike two for the positive displacement supercharger? In this case yes, but it’s not all bad so read on.

More Things To Consider
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One of the key differences between the two superchargers is the way they produce their boost, and this will in turn effect the torque delivery of the engine. A centrifugal supercharger requires a high compressor speed to produce useable boost, but since the supercharger is driven by the engine, the compressor speed is directly related to engine RPM. This means that we won’t see much boost at low RPM and the boost curve will increase in a linear fashion with engine RPM.

A positive displacement supercharger on the other hand is always moving more air than the engine can consume and this means it can achieve good boost pressure all the way from idle, and the boost pressure will be reasonably constant with RPM. The picture above gives a good comparison of the difference in boost curves you could expect to see. The flatter red line is from a twin-screw blower, while the green line is from a centrifugal supercharger.


So what does that mean to your right foot? A centrifugal supercharger will do a great job of producing power at high RPM while a positive displacement supercharger will produce good low-RPM power. Due to their relative efficiencies, if both types of supercharger were producing the same boost, the engine equipped with the centrifugal supercharger will make more power.

Since a positive displacement supercharger gives a reasonably flat boost curve, the effect is to multiply the normal torque curve of the naturally aspirated engine. What I mean by that is, the shape of the torque curve will be very similar but you’ll have more torque everywhere. It’s almost like fitting a larger engine.

Due to the way a centrifugal supercharger creates more boost as RPM increases, this type of supercharger tends to magnify the torque curve more as RPM increases. The result is that the engine feels like it just wants to keep pulling all the way to the rev limiter.

Basically you need to choose what you want from your engine: a low-RPM torque monster capable of frying the tyres at a touch of the throttle, or an engine with more linear response that just keeps pulling harder the further you rev it.


A last consideration is fitment in the engine bay. Modern engine bays are getting more cramped for room and finding enough space for any form of supercharger can be a challenge. A positive displacement supercharger can have some benefits here – particularly in a V6 or V8 installation where the supercharger is often a good fit in the valley.

A centrifugal supercharger can be tricky to fit, but on the plus side they can be remotely mounted away from the intake manifold giving a little more flexibility to their location.


So there’s a summary of the choices you face if you’re looking at supercharging your engine. There are no easy choices when it comes to modifying cars and choosing the right supercharger for you is no different.

At least now you should have a solid understanding of the options and how they will effect the results you’re likely to see. If you have any further questions about the finer details of blowers, your setup, or your future boosting plans, I’ll be happy to answer them in the comments section below.

Andre Simon
Instagram: hpa101




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amazing write-up!


This is great. I am just about to supercharge my NA miata, and this write-up is such an awesome help.
Cheers mate!


that was a short but clear explanation on the supercharger differences, as well as when to use them.  thanks!


Thanks for the article Andre, cleared up a few misunderstandings I had!


So for FRS/BRZ, Cosworth is a positive displacement supercharger and Wortech is a centrifugal supercharge.


@FunkyChild What are you going for?


MOU89 yup, you got it! Vortech and HKS offer centrifugal options and Cosworth, Sprintex/Bullet and Cosworth offer positive displacement. In the current market you're pretty unlikely to find a roots-style blower as the twin screw offer much better efficiency.


@FunkyChild I'm glad you found it useful. Good luck with with your project and I hope this article helped make your decision easier.


matthewyaa happy to help. The options are pretty easy to understand but I still find a lot of confusion exists over the different choices. Hopefully this resource can be useful to others.


Is a centrifugal supercharger similar to a turbo charger? If so what is the pros and cons of each?


Reveley_97 They use the same principle, but the spin of the turbine in the supercharger is caused by a pulley which is connected to a belt, and in the turbo the spin of the turbine is caused by the exhaust system's pressure.


Reveley_97 exactly! A centrifugal supercharger uses a compressor section that is essentially identical to a turbocharger but it's driven by the crankshaft instead of exhaust flow.

The centrifugal supercharger is usually simpler, cheaper and easier to fit with the potential for better reliability, however the boost curve is always dependent on engine rpm (see the dyno graph in the article). This means that they work best at high rpm. On the plus side their torque delivery is very smooth and consistent which can improve traction and driveability.

A turbo on the other hand can provide much more flexibility in the amount of boost being delivered and it's easier to control from the cabin. Installation of a turbo system is more complex and expensive and there will always be some amount of lag when you first go to full throttle (although with a well matched modern turbo this is now much less significant).


Ahh thanks for the info!


Andre Simon Very nice write-up! If you're ever in SoCal, come on over to Vortech Superchargers. I work in their Engineering Department & would be more than happy to give you, or any SpeedHunter, a tour of our facility!



Great article bro, thanks!


I'm considering twin-charging, and my priority is compact packaging but loads of pow on all revs. Will centrifugal do?


Great article  Andre... waiting on individual throttle bodies vs intake plenums or both together ...... Speedhunters???  tech article from Andre to clear up misunderstanding to us the reader and enthusiast , i thank you guys for sharing the knowledge and it makes it interesting to go do the courses ...... Keep up the good work Andre n thank you again thanks speedhunters!!!!


Is it possible to have a supercharger and a turbo in the same set up? There is a Starlet GT in my locale which is hella fast and rumour has it it runs on both.


Is it posible to run a center fugal with a NOS set up or would it mess with the smooth power band because of the rpm rising faster than usual? Wondering about putting NOS in the challenger would be really help full!


Rick Rosales thanks for your comments! I'm probably going to end up in SoCal again later this year so I'd love to take you up on a tour. Flick me an email to with some contact details. Thanks!


UWerqxTeam_MJ twincharging isn't overly common due to the complexity of the system. The potential for results is there however you would be better to consider using a positive displacement blower. 

The advantage of twincharging is combining the instant boost and good low end performance of a positive displacement blower with the efficiency of a turbo. The centrifugal supercharger isn't going to help you in the bottom end so you would miss the true value of the system.


zemanski thanks for your comment! An article on itb's is actually a great idea. Thanks for bringing it up.


zollz yes it's possible - It's usually referred to as 'twincharging'. It's a complex system to get working perfectly but it does have the potential to basically give you the best of both worlds - Great low rpm performance coupled with the efficiency of a turbo at high rpm.


jacobherman14 there's no reason you couldn't use NOS with a centrifugal supercharger. With a turbocharger NOS will dramatically improve the spool time of the turbo but obviously with a centrifugal supercharger the boost is still tied to the engine rpm so NOS won't effect the boost. It's going to give you a similar boost in power to what you would see on a naturally aspirated engine.

One aspect to be aware of though is that both supercharging and NOS will create more cylinder pressure - This is after all why we see more power from them. If you're putting both power adders on a stock naturally aspirated engine, you may risk exceeding the mechanical strength of the engine internals. You will also need a way of retarding the timing to suit the supercharger and then even further when the NOS is active. Reliability will require precise tuning.


Please write more of these! The more info the better!


You're partially right... NOS is normally used on N/A engine to give it more air at higher rpm (usually). Along with the procharger (centrifugal supercharger) it provides exponentially higher boost figures as the rpm climbs. Now since it has a lack of low-end boost, what you might see happen is tuning the engine to have the NOS engage at lower rpms


Is it possible to run a twin centri setup? If so, what will the differences be from a twin turbo?


From what I've read the twin screws are superior in most ways to centrifugal superchargers. Even in the graph you show, the centrifugal only makes more boost for about 250 rpm. The twin screw is superior in the entire rev range. On tracks I would take a twin screw over a centrifugal any day.


@Chris as per the article it really depends on what you're definition of superior is. Judging two superchargers purely on the boost they're able to produce isn't going to tell you very much about the power and torque they will deliver on the engine, or the shape of the power curve.

You need to consider boost pressure along with the efficiency of the supercharger at that particular pressure ratio as well as the ability to intercool the heated air efficiently. In both these cases the centrifugal will be superior. On this basis if you were choosing a supercharger purely for the track where you are almost always in the mid to high rpm range, the centrifugal is actually likely to be your better choice.

I'm not knocking the twin screw and a centrifugal SC will never be able to match the low rpm torque of a positive displacement. There is a lot more to a supercharger's performance than just boost pressure though.


raidensnakeezio it would be possible but not really beneficial. 

Twin turbos are common as using two smaller turbochargers will result in lower inertia in the turbo assembly and the ability to spool up faster compared to a single larger turbo. Boost response with a centrifugal supercharger is defined by engine rpm so lag isn't really a consideration.


mlc5309 glad you are enjoying the articles! I look forward to bringing more to the Speedhunters community :)


TimAukamp I'm not sure if I've understood your comment correctly so I'll apologise if I've got the wrong angle. Nitrous won't effect the boost level you'll see with a centrifugal supercharger. The only thing the supercharger cares about is how fast it's rotating and the volumetric efficiency of the engine. If you're not altering one of these two aspects then the boost won't be effected by injecting nitrous.

As you mention, you could utilise nitrous to pump up the low rpm torque of the engine where the supercharger makes little boost. I haven't used nitrous like this with a centrifugal supercharger but my guess is that it would be hard not to introduce a hole in torque at the point where you switched the nitrous back off. That may still be a worthwhile tradeoff for the increase in low rpm torque though. Of course how pronounced the hole is would also be dependent on how much nitrous you're spraying too.


Andre Simon Thanks. One more thing to clear up. Does doubling a forced induction device of the same size to a throttle body/ies also double boost?
If x=amount of turbos(same size)
y=amount of boost
then 2x=2y, no?


raidensnakeezio If you double the airflow then within the realms of efficiencies I would expect you may end up with approximately double the boost pressure and I think this is what you are getting at with the twin centrifugal supercharger idea. That being said you would be much better off to simply fit a single larger supercharger capable of supplying the airflow you're looking for.


Andre Simon TimAukamp  Yes, you're correct and I thank you for catching my mistake. True, nitrous doesn't effect boost however it does effect rpm and gives the engine more air. Nitrous oxide, in the scientific sense, is two parts nitrogen, one part oxygen. This being how nitrous works, it provides 66.6% of nitrogen and 33.3% oxygen. The reason this works is because normal air will consist up to 90% nitrogen and around 5-6% oxygen. So theoretically Nitrous is better for your car then normal air. Also it is one of three commonly used gasses that are colder when pressurized, other two are propane and CO2. Try putting those into an engine(I know they already make propane engines).

I was caught up in my wording. Thank you for bringing this to my attention. Good job on the article by the way!

side note: check at this video you might find it interesting...


Andre Simon Oh for sure. Well said. The cam profile also matters. I come from a canyon background so a twin screw would be far superior to a centrifugal, but on the track I think you would be right. Personally I would rather turbo charge for that particular application with an anti lag system (one can dream). 

Boost is a complex issue that requires the tuner to account for a lot of variables. Even driver skill comes into play. Nice write up and good pictures! 

For the most part turbos tend to dominate time attack cars from what I've seen. Haven't seen a top level unlimited class car run a supercharger that I can recall.


Andre Simon : Dont know whatyou where thinking: Water To Air is way more efficient for cooling. Otherwise we would all have aircooled engines. It should be the other way around. Installation is more difficult though as of the extra plumbing....


Andre Simon raidensnakeezio : Dont forget that if boost is slightly off you cant make the system parallel because of boost from one charger is hindering the other one. You can make a system work in series though, although since it is belt driven a bigger supercharger would be cheaper and about as much as efficient....


Kevski Style unfortunately it's not quite that simple. The specific heat value of water is much higher than air meaning that water can remove heat from the charge air very efficiently however there is a little more to consider.

While water can absorb heat from the intake charge efficiently, the water still needs to transfer this heat back to ambient air which then relies on air as the cooling medium - Basically it's easier for the water to absorb heat than to dissipate it so over prolonged hard use it's usual to see the water heat soak and the IAT rise. This situation is amplified when smaller than ideal heat exchangers are required to fit a tight installation.

Water-to-air isn't without its benefits though. In mid-engine applications or very tight engine bays it can be easier to fit a water-to-air system. They also really come into their own for a drag application where you can run an ice water slurry - I ran this system in my drag car using a PWR barrel cooler and could easily achieve IAT lower than ambient at the start of a run and temps in the low 30's at the end, even with 50 + psi boost.

For prolonged hard use though it's difficult for a water-to-air system to match the IAT attainable with a decent air-to-air core. This is why you seldom see water-to-air intercoolers in professional motorsport.


Andre Simon : Water can dissipate heat way better then air can. Its all a matter of designing the system correctly for the application. You just need to have more water and an effective radiator to cool everything back down again. A couple of hours drive shouldn't be to bad. Weight can be an issue though. Its way heavier then an air to air cooler and its more complicated. On top of that most regulations tend to ban water to air intercoolers and you have the real reason that they arent used much in motorsports. The adiabatic effects are way better then air can obtain. One thing shouldnt be overlooked though: There is always a fresh air supply around allthough you cant expect to have the same temp all the time....


TimAukamp Andre Simon Don't know what planet you are on dude, but on Earth it's about 21% O2 and 78% N2.  I think you should probably leave the technical stuff to Andre!


Andre Simon zemanski Please do this. Would be excellent


Kevski Style it's not the ability of the water to dissipate heat that I was referencing - Once the water transfers the heat to the heat exchanger you're back to relying on airflow for your cooling. You're also now transferring the heat twice (air to water and then water to air) which effects efficiency.

Adding more water won't fix anything. It'll just prolong how long it takes for the entire system to heat soak. A bigger heat exchanger would help however water-to-air is almost exclusively used when room is lacking and hence the radiator and exchanger size are typically compromised.

I wasn't talking about theoretical ideals here - I'm talking about the real world installations that are actually in existence. In my own experience on both the dyno and the race track they simply don't match a quality air-to-air. 

I'm interested to know which regulations ban water-to-air? I'm struggling to find a justification for banning them? On this side of the world there are no such rules yet they are still uncommon.


Andre Simon true on the airflow part, but bare this in mind: When you have a normal car without a turbo, it cools better with water then without it,right? Thats because water absorbs heat better then air does. The water gets cooled by air via the radiator. Only in marine applications that wouldnt be the case. When temps get high water cools better. But water (and everything else for that matter) cools by way of exchanging energy and therefore heat. The bigger the temp difference the better it cools. So higher intake temps result in a bigger temp drop with the same temp of cooling aid (water or air). But it will also heat up the cooling aid more. So you are correct that it doesnt help efficiency by using air and water to cool, but it still more efficient by using them both. The only real concern is heat soak, but a properly designed system wont have those issues. And by that I dont mean of the shelf designed, but hand fabricated for the application. Doing it correctly it can be driven hard for a couple of hours and during traffic.

That being said: Why would you do it if space isn't an issue? WRC uses it because of space and reliability. Apart from drag racing it isnt used anywhere. I believe its banned in WTCC, le mans and F1,although i dont know that for sure. It's been years since I was involved in F1, so current regulations arent up to spec....


Kevski Style Andre Simon water to air is superior. I worked for a guy who built twin turbo V8s that broke records (one street car did 270mph on the salt flats) and he exclusively used water to air intercoolers on every single build he did. These were 5 to 10 liter street driven engines that were pushing 1500-2500hp.


Wow Andre Simon you need no introduction my friend DOCILE was a filthy weapon if ever I have seen one I used the parts list from zoom magazine (before tube frame) like I recipe lol worked well I might ad I intended to take it to speed tech for tuning but was too far to travel ended with 337kw atw... you're work is extremely impressive you open doors many suggested couldn't be opened.. I'm off topic there
I now have a BA xr8 with CAPA vortech kit makes 330kw atw sounds great but they FG f6 I had would fucking kill it as the power curve climbs all way to rev limit and then drops of so badly changing gears it's likely only 220kw at 4000rpm
I'm a little unsure of why this is but I'm assuming it only achieves 8psi right at end of rpm as without a waste gate(boost limiting) like a turbo all that limits boost is gearing?? Having said that the engine swallows more air as revs increase so maybe this assumption is wrong.... What are my options to actually make this thing fast? Cos now it really isn't its piss week bar the almighty surge just before the limiter. I'm thinking air to air intercooler to avoid detonation with a couple of extra pounds... But can boost be increased and blead of when it tries to get too much or should I look at gearing supercharger differently and lowering rev limit.. I have always been a fan of the idea of water injection although I have never used it to date. Really the only things I know I can apply to it are only going to fend of detonation opening a door to increase power in this high rpm range not really fixing the problem I'm talking about.... I'm a bit disappointed with the ozzy 5.4 to be honest. My back up plan is rebuilding the engine with the right bits and pieces and a large single turbo set up.. Love to hear you're thoughts...


With a twin screw how to shift a mamuel to get top speed. Im new at this. I have a 2015. Mustang gt ford racing sc 670hp. Do I drive 6th od top speed than drop to 5th gear to build top boost and back to 6th. When Im out cruising. Or do I create top boost and car speed from start.Thanks!


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You're slightly misinformed about superchargers. Centrifugal superchargers don't compress air in the same manner as twin-screw types. The air is more or less "compressed" because it is forced at a high rate of speed into the intake manifold, where as a twin-screw actually compresses the air between the screw lobes; this is why centrifugal chargers run cooler. Also, water dissipates heat much better than air, contrary to your statements, hence the reason nearly all engines produced are liquid cooled. Please do proper research before posting false info.


It's called a radiator, fool. Water MORE efficiently cools the charged air, then moves through a radiator to cool the water.

Graham Phillips

So what must be done to, let's say a smaller v8 (4.1L) to make power, upwards of 800whp with a PD blower? Ported heads? Larger valves? What design of cam would benefit most? The engine in question has a pentroof style combustion chamber, 10.2:1 compression and has a factory redline of 7100rpm or 9000rpm with rod bolts.

Graham Phillips

Also the fueling would be both pump 93 as well as tunes for e85 and 112+ octane race fuels