When the supercharger is spinning at part throttle, there is an internal vacuum controlled bypass valve that opens allowing the air to recirculate through the supercharger so that it is not compressed.  This reduces frictional losses at part throttle, when the throttle is opened, the manifold vacuum falls and the valve closes allowing the supercharger to build boost.  Some supercharger kits have a blow off valve that does the same thing but we like this clean internal self contained method better.

You can see the Sprintex's screw shaped rotors that diverge at the end of the housing compressing the air internally. This is different from the lobe shaped rotor of a typical roots blower that simply moves the air past the blower allowing it to back up and compress inside the plenum of the intake manifold.  The external compression of the roots blower is far less efficient.  You typically see numbers of about 50% which means more crank power robbed and more heating of the intake charge air, as high as 300 degrees or even more under some conditions!  Compare this to our blower's 70% efficiency.
Here is a cutaway drawing of the actual blower used on the FR-S.  You can see the diverging screws and can visualize how they can provide efficient internal compression versus the lobes of the traditional roots positive displacement blower that simply moves a higher volume of air allowing it to squish in the intake plenum assuming that the blower moves more air volumetrically than the motor.

Here is the compressor map for our Sprintex S5-210 blower.  Note how wide the 70% island is. Our blower will be operating at peak efficiency for most of the engine's operating range!  A centrifugal compressor like that used in some other supercharger kits might reach a higher peak efficiency but it will have a more narrow operating range.  A positive displacement screw blower might have just a few points less peak efficiency but will have a lot of area under the sweet spot curve.

More power means more combustion pressure and more heat.  Since our car is going to be track driven, we have to deal with the heat.  We got a large capacity drop in radiator from Koyo Cooling Systems to help keep things happy.  The Koyo radiator has an all aluminum core with about 40% more capacity and TIG welded aluminum end tanks.

The Koyo is deigned to drop in perfectly with provisions for the factory fans and brackets.  Innovate Motorsports' R&D test mule FR-S has run this radiator in 100 plus degree Arizona heat on the track with water temperatures remaining totally in control.

We found the radiator to live up to its claims of perfect fit and easy drop in installation.
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Monday, September 09, 2013 11:19 PM
It got rid of that big torque drop at 4k rpms too. That's major bonus.
Tuesday, September 10, 2013 4:07 AM
Looks like a good kit? How about water injection instead of an intercooler?

Is the FRS ECU strategy different to Subarus of past? In other Subarus increasing the advance multiplier to 1 wouldn't reduce the ability of the ECU to pull timing. It would just increase the total timing right after an ECU reflash.
Tuesday, September 10, 2013 5:47 AM
what made you guys choose a supercharger over a turbo kit? is response a higher priority than power? not impressed with the price/performance/reliability of current turbo kits?
Tuesday, September 10, 2013 6:08 AM
Geeze, what a pain to tune. Subaru knows that this model is going to be often modified and should have run an ECU that adapts towards standard modifications, not against them.

Also, I think it is fair to call BS on the factory 200 hp number. If FI can't even get the WHP number back to crank hp then something is wrong.
Tuesday, September 10, 2013 7:23 AM
I'm sure many others are having the same tuning issues you are and there must be an ECU in the works rather than just a flash. This is just a small jump in power compared to cars of the past, and I'm wondering what the tuning ceiling will be. Have you guys tried running a tank of "imported" 93 octane or other fuel through the car? CA gas is notoriously bad for tuning. Maybe I'm just always looking for a workaround rather than solving the real problem :/
Tuesday, September 10, 2013 7:34 AM
Maybe Subaru did what they thought was best to protect themselves as far as warranty claims. The BRZ is so popular, every backyard tuner might take a crack at it. This isn't a low strung/low compression motor to start with, so maybe it just doesn't have a lot of latitude for inept tuners messing around.

If i was Subaru, i could see making the factory ecu do conservative correction, while assuming something like KPro will allow people who really want to tune to go to work (assuming something like that can exist for this platform). At least with a KPro mod, Subaru would know if the factory ecu has been altered/tuned. It's inevitable that the BRZ/FRS will gain good ecu tuning tools given their popularity, no?
Tuesday, September 10, 2013 7:45 AM
I think you are right about the warranty issue, I just think that it is silly for the car manufacturer to try to protect the tuner. You modify certain things, it voids the warranty. I never understood why that is such a difficult concept for some tuners.

Also, you are correct that a full stand alone is not installed (yet?) and maybe these guys just need more time to flash certain parts of the ECU to fix the adaptive process.

I thought I remembered a project WRX from SCC where the ECU had actually added hp on the stock vehicle after significant hard driving and they couldn't reproduce the results after resetting the ECU.
Tuesday, September 10, 2013 8:02 AM
I was thinking more like Subaru protecting themselves from the tuner than protecting the tuner. February tunes don't necessarily work in August unless you plan for it. It's pretty easy to imagine a scenario where a tune works in colder weather, but summer heat brings pinging and there are engine problems. The car owner is then able to bring the car in for warranty service. i know this is a potential problem with any car, but i think there is more latitude in most engines. This is an inexpensive car (relatively speaking) with an audience that will want to modify things but without the know-how. When an engine is pushed as this one is from the factory, are there timing changes that have to be made to run I/H/E? I have no idea, but a ton of people probably don't even know to ask that question. When I said backyard tuner, i was using the word tuner in a joking way - i meant someone with the ability to fit a CAI only because someone said it would make the car faster (and with no other understanding or consideration of what else might be involved).

I'm not sure if the S2000 received the same attention as the FRS/BRZ, but it's the only other similar car i can think of that's so highly tuned from the factory. Cars i can think of from my school days in the 1990s like the EG/EK civic, an NA rx7/300zx, a 240sx, sentra se-r, etc., had a relatively mild tune from the factory and it was safe to add I/H/E without much in the way of tuning considerations.
Mike Kojima
Mike Kojimalink
Tuesday, September 10, 2013 8:11 AM
12:1 compression and 91 octane fuel. Direct injection or not the engine isn't happy. You have to tune with our fuel to know just how bad it is. If feels worse than 91 octane. When we went from 92 to 91 it was a huge difference.
Tuesday, September 10, 2013 8:19 AM
If the Ecutek timing and fuel control strategies work well with the supercharged car, wouldn't they be able to be applied to the NA car as well? I know that the Ign. Mul. Constant was changed on the NA car but what else was modified, besides fuel and timing target tables, on the Ecutek flash that got the consistency? If the 91 Cali fuel is that bad I would be worried about long term issues with knock/other issues as fuel quality, and driving conditions vary as the ECU won't be technically as quick at stopping those issues.
Mike Kojima
Mike Kojimalink
Tuesday, September 10, 2013 9:24 AM
The fuel and spark map when NA were left alone. We just changed the intake advance multiplier. Since it is 1 it will not increase the amount of advance, simply reduce how aggressively the ECU can remove timing. It can still remove it though.
Mike Kojima
Mike Kojimalink
Tuesday, September 10, 2013 9:58 AM
Some of the things I plan on trying are a water to air intercooler that Innovate has in the works right now. We will get one of the first production pieces. Modify the intake tube so we can use the less restrictive Greddy airbox and filter. Water injection and a smaller pulley. Custom tuning. Oh yeah an oil cooler because some of the power fade could be oil temp related based on experiences others are having.
Tuesday, September 10, 2013 10:17 AM
Just out of curiosity, what station are you getting your fuel at? I ask because I know Chevron's fuel is higher quality and I was curious to see if you have tried that. Maybe you just need to visit you local Autoslut and get some octane booster to see what kind of results it will pull out, although having to go and buy some every time you fill up doesn't seem like the most "luxurious" idea.
Tuesday, September 10, 2013 10:27 AM
An intercooler and adding straight water injection to combat detonation is what I was thinking as well.
Mike Kojima
Mike Kojimalink
Tuesday, September 10, 2013 10:48 AM
We use only Chevron in MotoIQ's FI project cars.

One thing I hate about octane booster is the weird orange residue they leave over everything. I have always felt that this couldn't be good for the O2 sensors even if it says O2 sensor safe.
Tuesday, September 10, 2013 11:08 AM
This thing is BEGGING to have water/methanol sprayed into the intake. I think the power gains you guys saw are only the tip of the iceberg. That Sprintex 210 blower should be capable of *a lot* more power.
Tuesday, September 10, 2013 11:36 AM
I understand the use of the advance multiplier but was curious if this was modified on the Ecutek map for the supercharger as well as any other constants or factors used by the ecu for timing and fuel correction. If they weren't it would seem you would be having the same problem with the supercharger kit down the road where you would be seeing power lose after some driving time.
Tuesday, September 10, 2013 11:40 AM
@ lastminute, Protodad, etc: the FR-S is so hard to tune compared to other Subaru-powered vehicles because it's not running Subaru engine mangement. If you remember in my glorious FR-S review (http://www.motoiq.com/MagazineArticles/ID/2505/Tested-Scion-FR-S.aspx), the FR-S is running Toyota's D-4S engine management, which is just as recalcitrant to modifications as other Toyota products, probably even more. Anyone who's thrown breathing mods at a newer Toyota without the ominus dominus from a TRD reflash knows this pain.

@ SupraHKS: Even with Chevron and other high quality fuels, it's still high quality shit. The Arizona/California/Nevada "91" (ACN91) octane fuel is so horrible that major tuners release unique maps for it. The formulation itself, mandated by our best buddies at CARB, does something to the fuel that makes it perform worse than it's octane rating suggests.

Also, octane boosters aren't incredibly effective since octane works by averages. So that $8 12oz can of "NOS 100 OCTANE!" against 13 gallons of 91 pisstane results in something like 91.1... :)
Mike Kojima
Mike Kojimalink
Tuesday, September 10, 2013 12:42 PM
We currently have the .7 multiplier with the supercharger. We are probably going to change it to 1.0
Tuesday, September 10, 2013 2:57 PM
ah, that makes sense. malice or ignorance? does toyota purposely make ecus that are difficult to work with, or is it just that they haven't made any efforts to make tuning easier? i guess i haven't read much about this because there hasn't been a toyota i've wanted to own or tune for quite some time.

is there a standalone that keeps street legality (or fakes it) with respect to obdII compatibility? my understanding is that kpro is good for this in the honda world

ps., can't believe i forgot something from that glorous review. guess my mind was so blown, i couldn't retain the details :)
Mike Kojima
Mike Kojimalink
Tuesday, September 10, 2013 5:59 PM
Short answer is no.
Wednesday, September 11, 2013 7:07 AM
Supercharging Subaru engines has gotten a lot more common in the past few years, and I'm glad to see it! It makes my '00 RS/C look like less of a freakshow! :D

Not being well versed on modern ECU emissions and such, are there any piggybacks that could serve to tune the FR-S/BRZ, or would that just be adding problems?
Mike Kojima
Mike Kojimalink
Wednesday, September 11, 2013 8:32 AM
Piggybacks don't really work all that well. They fight the stock ECU.
b drecksage
b drecksagelink
Wednesday, September 11, 2013 8:52 AM
Wow...I was shocked to learn this kit only costs 3700.
Wednesday, September 11, 2013 10:39 PM
Element tuning has a standalone out http://elementtuning.com/store/#!/~/product/category=439245&id=1509847
Thursday, September 12, 2013 10:00 AM
Sigh...This kit gets produced/imported from Sprintex in around a year, and USDM GE8 Fit guys are still waiting on ours 6 years later.

That's what we get for buying into grandma car chassis though.
Thursday, September 12, 2013 10:05 AM
Oh, and definitely keep us posted on the gains this car gets from smaller pulleys!
ekka decker
ekka deckerlink
Thursday, September 12, 2013 10:05 PM
Some Guys in Aus are using a combination of ecutek, haltech ps1000 and a flex fuel sensor to get the required flexabilty on e85 till some one develops a complete stand alone soloutiuon.


Sunday, September 15, 2013 9:23 PM
As someone who works in Toyota, I think I have a theory as to why your having problems with the repeatability of the power. Sadly TMC (Japan) did all the engine cal for the FR-S so I cannot be 100% positive.

So I think it runs the newest version of our (well, Denso's) ECU which has a really complicated knock control system. Basically to sum it up, Toyota takes the stance that the computer should adapt to the engine so that there is always a little bit of knock (a little knock isn't harmful and lets you get a little more power). It is an active system, so it adds timing until it knocks. This is unlike most systems I have seen, they are usually passive (so pull timing when there is knock). Toyota's system then looks at the waveform generated by the knock sensor, the intensity of the knock sensor output (Vmax), and the time gate it happened in crank angles.

This system is also brandy new, before the knock system just looked at the intensity of the sensors output, not waveform matching. It also has tons of variables that need to be calibrated, so that may be a factor too.

So the point is that I think the poor CA gas may be working the knock system a little more than TMC thought it would, so if I was a betting man and you were able to log ign timing during those pulls i bet you would see it vary quite a bit. Furthermore, the system does work over longer terms to learn the engine and knock sensor so that may explain your power drop off over time (or the current tuner software isn't fully overriding the stock system, it is really complicated).

Just an idea!

Monday, September 16, 2013 5:53 PM

Don't worry, the GF will still have plenty of support. Unlike my GC...
Tuesday, September 17, 2013 3:05 PM
@hydrochloric, I think we're talking about different things. I'm referring to the 09+ (GE) Honda Fit, for which Australians have a Sprintex PD SC kit, that doesn't work on USDM Fits.

Some people have been able to get custom turbo setups working, but not without major issues, major expense, or both, so I and others have been waiting on Sprintex to deliver for a while...

Also, I wrote 6 years when I meant 4. Must have been thinking in base 12...
Wednesday, April 09, 2014 5:07 AM
For whatever it's worth, this thing's WHP/L is right in line with more expensive but similar engines (NA, no cam profile switching). Toyobaru should have hooked this up with Toyota's VVL-i system and 500ccs more displacement. A torquey 200whp in a 2800lb body is pretty much perfect and in line p/w wise with "faster" but significantly lardier hardware
Wednesday, April 09, 2014 7:21 AM
IIRC, Toyota was concerned about not getting the revs they wanted (north of 7000rpm) with 2500ccs.
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