Project SEMA Scion Tuner Challenge FR-S: Getting More Power with an HKS Supercharger and More Cooling with a CSF Radiator 

by Mike Kojima

Our SEMA Scion Tuner Challenge car's progress is coming along nicely.  With all of our other mods coming together we now will focus on getting serious power out of our FA20 engine with an HKS supercharger.  With power comes heat and we will be relying on a CSF racing radiator to take care of our cooling needs. 

We chose the HKS supercharger because it is diametrically the opposite in operating function of the roots type Innovate Motorsports supercharger on our own Project FR-S and we wanted to test it out.  HKS is know to make high quality parts with an OEM level of fit and finish and like all of our project, we wanted something that would not only make power but be reliable day in and day out without affecting the normal function of any of the cars operating systems.  

Of course more power means more heat so we were not going to let the stock radiator handle all of the additional thermal load, especially when anticipating potential track use so we chose the same CSF radiator that just won our FR-S radiator shootout. 

Read all about about Project Scion Tuner Challange here!

The HKS supercharger is a centrifugal supercharger which is very different from the positive displacement roots type supercharger found on our own Project FR-S.  A centrifugal supercharger is like a crank driven turbocharger.that uses a snail like housing and an impeller wheel to compress the intake charge.  Centrifugal superchargers have internal compression and hence a naturally high adiabatic efficiency.   What this means is less parasitic crank power loss and a cooler charger air temp.
A disadvantage of centrifugal superchargers is that they make little boost at low rpm and thus have a sort of lag much like a turbocharger.  To make up for this, HKS has incorporated a traction drive transmission into their supercharger.  The traction drive uses steel rollers instead of gears, bathed in a special "traction oil".  This allows the supercharger compressor to spin up quickly.  When the compressor is at max output, the traction oil allows for some slip so the compressor won't overspeed into surge.  This is kinda like a torque converter in an automatic transmission and allows for an aggressive step up in gear ratio so the supercharger comes into boost sooner.  Another advantage of the traction drive is that it is very quiet compared to gears like what some other centrifugal supercharges use.  The traction drive can create a lot of internal heat so an external oil cooler must be used.
The HKS supercharger kit comes with an efficient and generously sized tube and fin intercooler.  Tube and fin heat exchangers are lightweight and work well when there is good airflow through them although they don't have as much heat sink affect like the common bar and plate heat exchanger.
The HKS supercharger kit is very complete and comes with every single part, nut bolt line and clamp for an easy installation.  The HKS kit is very high quality with an OEM level of brackety and high quality cast charge tubes. 
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Tuesday, January 27, 2015 1:10 AM
I like where this car is headed now :D
Tuesday, January 27, 2015 11:32 AM
Does anyone know what the difference is between the HKS units and Rotrex units? I know they require different traction fluids, and work slightly differently, but I don't know to what extent, or whether one unit works more efficiently, or produces better power, than the other.
Mike Kojima
Mike Kojimalink
Tuesday, January 27, 2015 1:57 PM
They are very similar.
Dusty Duster
Dusty Dusterlink
Thursday, January 29, 2015 8:25 AM
Is that traction fluid a type of oil? Is it similar to motor or differential oil?
Saturday, January 31, 2015 7:23 AM
It's closer to the fluid used in viscous couplings, and differentials.
Here are two links if you feel like reading up on lubricants and traction fluids.
You can basically read the whole book on line. But you can always find a few hard copies on say, amazon or ebay.


Wednesday, February 04, 2015 7:43 PM
Does the traction fluid ever need to be changed?
Is the traction fluid cooler sized for fit or cooling capacity? In the SoCal heat will the car lose power during track days?
Does it work on the serpentine belt, or a separate one? What are the chances of belt slippage?
Mike Kojima
Mike Kojimalink
Wednesday, February 04, 2015 7:54 PM
It should be changed periodically but not too much like the engine oil. The belt doesn't seem to slip.
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