Shane's supercharger project

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Price Breakdown

  • $300 - M63 Supercharger
  • $15 - Vacuum Switch
  • $30 - MAP Voltage Clamp
  • $20 - Used SVX FPR
  • $50 - Used Vortech SFMU
  • $70 - New Walbro 255 fuel pump
  • $40 - WRX TMIC & Y-Pipe
  • $45 - Adjustable BOV - is actually a bypass valve.
  • $20 - serp belt
  • $24 - Colder NGK Spark Plugs
  • $40 - pair of idler pulleys
  • $15 - 3" Cone Filter
  • $50 - 3 various 3" silicone couplers and elbows. (averate $20 per item)
    • For about $80 on EBay, a FMIC piping kit comes with both pipe and couplers! Better Deal.
  • $200 - various pipes, and metal plates and hardware
    • $50 for 12"x12"x1/2" Alumimum Plate 6061-T651 [Here]
    • $38 for 12"x12"x3/8" Alumimum Plate 6061-T651 [Here]
    • $18 for 12"x12"x1/4" Plate Steel 1045 [Here]
    • $18 for 12"x12"x1/4" Plate Steel A-36 [Here]
    • $9 for 12" length 3" round tube with 0.065" wall alumimum.
  • $100 - just as a little buffer
  • $1065 TOTAL


Change the SC pulley, and the cost obove will be affected in the following way. Plus, changing the pulley ratio will be MUCH easier.

  • -$15 - Vacuum Switch
  • Save $250 for custom crank pulley (not really shown above)
  • $80 - for 3-3/16" SC pulley

Various Parts Needed

  • Mercedes M63 clutched supercharger ($250-$500 on Ebay)
    • It's actually a M62 with a mercedes clutched pulley.
    • The pulley is 3-5/8" in diameter.
    • A one off 6" crank pulley will cost around $300 to build.
  • MAP Voltage Clamp
  • Vacuum Switch to engage clutch.

Adjustable FPR or RRFPR

  • Awesome Calculation Thread
  • SVX FPR - ($93) from Used, should be around ($20).
  • The XT6 (v6 model ONLY) also works as an alternative to the SVX FPR. Used at JY for $5!!!
  • []should be able to track down a used one for about $35.
  • [Weapon-R Fuel Rail Adapter] ($15)
  • [Megan Racing FPR] ($76)
  • No matter the FPR choose, a manual boost controller can be used to tweak the boosted fuel flow.
  • Most RRPFR require a rebuild after 30-40K miles
  • Vortech 8:1 (Ebay < $60). 4:1 kit extra
  • OBX 8:1 (Ebay $90ish) - not recommended by the nasioc crowd.
  • [Bel FMU] ($260 MSRP)
  • [RS25 Thread claims that at 5psi boost, a 6:1 RRFPR should work fine u to 60psi. 8:1 errors on the side of safe.

Air Filter

  • Sounds like foam is the best substance, followed by gauze then paper.
  • Consider using a replaceable paper cone filter, if it exists.
  • It appears that a 3.5" tube made into an oval will be a perfect size fit for the intake on the M62. This means that we should need an air filter with a 3.5" ID opening.

Fuel Pump

  • Calculation for required flow
    • GPH Flow = HP * BSFC * (1 / fuel weight)
    • 6.216lb/gal for regular unleaded
    • 6.350lb/gal for premium unleaded
    • 300 * 0.55 * 0.157 = 25.9gph * 1.3 (safety margin) = 33.7gph
    • 350 * 0.55 * 0.157 = 30.2gph * 1.3 (safety margin) = 39.2gph
  • Walbro 255lph fuel pump ($120 new, $75 on EBay)
  • [Pump or Kit on nasioc] ($69-$84)
  • Holley Part Number 12-909 lists as TwinTurbo RX-7. But the RX-7 is too short on the pickup side. This Holley one isn't.
  • OEM Pump Capacities
    • 02-05 WRX = 130lph/34gph
    • 06+ WRX = 145lph/38gph
    • 04+ STi = 145lph/38gph
    • 00RS = ??lph



    • Adjustable BypassValve is a BOV with lighter spring.
    • Needed to prevent belt load when quickly shutting the throttle.
    • Adjustable needed? Or at least a pressure release near 8-10 psi.
    • One that fits a WRX TMIC would be best.
    • GFB recirculating BOV can be used, and adjusted.
    • How? The vac-line opens the BOV at idle, and off throttle. The spring can be trimed to lighten the overall pressure on the valve piston. This means it can act as a pressure release valve also. When WOT, boost pressure pushes on BOTH sides of the BOV piston, keeping it closed. Just make sure you don't lighten the spring too much.
    • Tuning the action of the valve so that:
      • It opens on throttle lifts
      • It opens at idle
      • It progressively closes as the throttle is opened
      • It opens a little at peak boost to control the level reached (hardest to achieve)

MAP Clamp


  • AutoMeter Direct has free shipping along with the same prices as Summit
    • Keep an eye on ProSport gauges, the have a line of 52mm/2-1/16 with no extra controller module. Plus, the nasioc crowd seems to like them so far.
    • Boost/Vac 30Hg->15psi
      • Auto Meter Arctic White 1372
      • Auto Meter Designer Black 1472
      • Auto Meter Z-Series, Black face mechanical 30HG-20psi ($50)
      • Stewart Warner Competition Line - 114538 (white face, black bezel -30vac->15psi boost) $50
      • Stewart Warner 114536 (black face 30Hg-15psi) $60
      • Stewart Warner Impact Line 119819 (white face, silver bezel) -30Hg->15Psi) $35
      • ProSport $55
      • GlowShift $35 30psi
      • STRi XLine -30-30 psi, black with dimmer $53
    • Fuel Pressure
      • Stewart Warner
        • 114514 mechanical full sweep $55 - Will need isolator
        • 114220 electric 1/2 sweep $55
      • ProSport $46
      • GlowShift $46
    • EGT
      • Stewart Warner 114402 ($100)
      • Stewart Warner Impact Line 119815 $50? Plus $120 for probe?
      • ProSport $90
      • GlowShift? WTF? $96 full sweep
    • Oil Temperature
      • Stewart Warner
    • Wideband A/F - [LC1] ($200-$400)

Gauge Combos

THE final decision
  • Autometer Z series. Black face & Black Ring.
    • Vac/Boost 2601 $52 @ summit
    • EGT 2653 $105 @ summit
    • A/F 2675 $70 @ summit
    • Selectable Light Color (white, green red)
    • -30 to 20 vac/boost and EGT gauge that should work with my existing probe.
    • Analog/Incandesant light can be hooked to dash light for dimming!!
    • NarrowBand AF gauge for a clean matching look. BUT!! It's an LED style, not sweep!!
  • Glowshift
    • Vac/Boost $36.99
    • A/F $49.99
    • EGT+Probe $99
Possible best match to OE dash
  • Autometer Phantom II
    • They are white by day, and black by night with black trim rings.
Current Fav
  • Stewart Warner EGT uses same thermocoupler
  • Stewart Warner has a 30-15 boost/vac gauge
  • Wait for next month, the impact line will be available. Nicer look.
Single Fuel Pressure Gauge
Auto Meter Phantom

White face 2-1/16 with black bezel and red hand.

Auto Meter Z-Series

Black face with red needle. Actually looks pretty good

Stewart Warner
  • Vac/Boost 30Hg-25psi $27
  • EGT ($99)

Clutch and Pressure Plate

    • Clutchmasters Stage-1 %70 more hold than stock ($450)

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  • The clutched SC will allow for the TB to remain on the intake manifold. The SC can be engaged with a vacuum switch.
  • With the clutched SC, there will be no need for a bypass valve.
  • A Bypass/BOV will be needed if the TB stays where it is. Even with the freewheeling clutch, it'll help reduce belt load.
    • On systems where the supercharger is blowing into the throttle, it’s very important when setting up the action of the bypass valve to measure the idling pressure in the system between the supercharger and the throttle.
  • [Parallel Fuel Rail Mod.] This is an alternative to the major mod version
  • Some sort of Timing Controller to pull timing on boost. eg. Split Second Timing Controller.
  • If the stock AF sensor continues to show correct values in openloop, then we won't need an aftermarket WB gauge.
  • Sounds like a combo of static FPR + FMU is more successfull than an all-in-one unit.
    • Perhaps an SVX FPR?
    • What rate of FMU is going to be ideal? Sounds like 6-7:1 is common in RS-T Setups.
      • The Ludspeed Stage 1 came with a Vortech FMU 8:1
    • If possible, put the T for the pressure gauges right in front of the first FPR. Putting it at the beginning of the system is OK, but it'll measure the pressure before the injectors. This actually shows the pressure drop! Go figure.
  • Somehow, use an idler pulley to route the belt under the rad hose. Might need a pair of idler pulleys. One to feed under the hose, and a 2nd to keep the returning belt away from the first idler. Should be able to mount the pulleys to the SC bracket somewhere.
    • For Reference, fuel pressure should be 33-35psi at idle, and 43-45psi at atmo. (remove vac line to emulate atmo)
  • WRX TMIC requires modifications to the TMIC outlet, and the Intake manifold inlet. They both need to be trimed to fit the TMIC between the TB and firewall. It's been done by many people though.
  • Plate Metal Choices - [SpeedyMetals] for good info and prices
    • Alumimum
      • Must be Heat Treated - eg 6061-T6
      • The strength between different grades is not significant. But, avoid 7000 series alumimum, it's hard to weld.
      • Aluminum should be 1.5 times as thick as a piece of steel to match steels strength. eg 1/4" steel is the same as 3/8" alumimum.
      • For this purpose, alumimum should never be less than 3/8" thick.
      • Grades
        • 2024 - High Strength. Excellent fatigue resistance. Poor choice for welding.
        • 3003 - Moderate Strenght. Good weldability. Better for forming, and sheet metal work.
        • 5052 - Stronger than 1100 or 3000, but not heat-treatable.
        • 6061 - General Purpose alloy. Highest resistance to corrosion. Low Strength. Easy to weld.
        • 7075 - One of the higest strength alloys. Poor weldability.
    • Steel
      • 4130 Chrome moly steel is good stuff, but not any stiffer than mild 1020 steel. Stronger yes, but not stiffer.
      • Grades
        • A-36 - General Purpose. Easy to weld.
        • 1045 - Not readily welded.
        • Grade 50 - The Workhorse. High Strenght, Low Alloy. Provides more strength per unit of weight. Easily welded.
  • Pop-Off valve
    • Need a device that can limit absolute boost in the intake manifold. Commonly called a pop-off valve.
    • Option 1 - Obtain a 5-psi waste gate actuator than can open a wategate style of valve in the intake.
    • Option 2 - External adjustable Turbo Wastegate.
    • Option 3 - Greddy Relief Valve
    • An external WG before the TB can double as a BOV of the vacuum line is referenced also in front of the TB. In other words, this WG can be mounted where the BOV goes.
  • Here is a quote from Redevil regarding low boost on a EJ25 [link]
Well, I simply used a 1-1 rrfpr, which may or may not have done dick.....
But to be safe, I would get a Vortech 4-1 rrfpr and then control the boost the regulator sees with a manual boost
controller. What this does it that the MBC allows you to regulate the boost to the regulator so that if the fuel
pressure goes up too far, you can turn the MBC down so the 4-1 becomes a 3-1, or a variation of there of.....
i.e. controls the fuel pressure....

Eaton M62

  • How to tell the difference between a Gen2 M62 and a Gen3. This is NOT definitive.
    • Gen3 had epoxy or teflon coated rotors.
  • I suspect that the M62 from the C230 is in fact a G3, perhaps a G4.

Power Steering Bits

  • The existing PS hoses and pipes could be relocated to under the intake runners. It'll require a hydrolic shop making a custom hose and fitting.

WRX Intake Manifold & TMIC

  • The BOV of a WRX TMIC on a stock 00 manifold will interfear with the throttle cable.
  • You will have to depressurize the AC and bend an aluminum tube to fit a WRX manifold. Might be able to simply remove the pitch stop, and bend with out depressurize.
  • The coil pack will have to be relocated.


Mounting Bracket

  • find a way to run a virtical triangle pice that runs from the bottom of the head, to the top of the head. Then out toward the side of the car along the bottom of the SC for a perpendicular brace. Holding the downward force of the SC.
  • Use HEAVY gauge steel. Don't risk flex or bending just to save a buck or two. Minimum 5/16". As high as 3/8" or even 1/2" on high stress parts.

The Pulley Dilema

  • M63 Magnetic Clutch Pulley = 3-5/8" diameter.
  • Stock Crank Pulley 5-1/4" diameter.
  • Stock pulley creates a 1.448 pulley ratio.
  • To get 1.65 ratio with M63 pulley, I'll need a 6" crank pulley.
  • 1.448 Ratio @ 6250 RPM = 9050 SC RPM = < 3 psi of boost.
  • 1.65 Ratio @ 6250 RPM = 10312 SC RPM = > 5 psi of boost.
  • I don't want to drop $250 on a pulley that might be wrong
  • Cheapest option is to get a SC that the pulley can be changed.
  • M90 pulleys are pressed on. To replace need a puller. It is also recomended to replace the M8 studs? Where ever these are? [AlpineEcho] stocks a puller and studs.

Stock Crank Pulley

  • To get a 1.65 ratio, the SC pulley would need to be 3-3/16" or 3.1875" diameter.
  • A 3.4" pulley from Summit gives a ratio of 1.54 = SC RPM of 9625
  • A 3.25" pulley from Summit (for Cobalt SS) gives ratio of 1.62 = SC RPM of 10125

Custom Crank Pulley

  • Gonna cost $300ish.

PS Stepup Pulley

  • The stock PS pulley is 4.5" in Diameter.
  • With the 5.25" Crank pulley, this makes a 1.166 pulley ratio
  • 6250 at the crank makes for 7288 at the power steering pulley.
  • To make 10K RPM at the SC with it's OE 3.655" pulley, we'd need about a 6" pulley on the PS pulley.
  • 6 / 5.625 = 1.655 pulley ratio

More info

According to [this RS25 thread], I should be looking at a sub 3" Pulley size?

Idler Pulley

  • A few OEM options exist here. the Mazda MPV for examle uses a decent looking idler pulley.
  • [Dayco] MFG makes alot of aftermarket OEM replacement pulleys.
    • 89003 - Flat face plastic Idler with side ridge (76mm) $13
      • 1991 Corvette
      • 2000 Ford Ranger
    • 89007 - Flat face steel idler pulley (76mm/3") $12
      • Mazda MPV V5
    • 89052 - Flat face steel idler pulley (70mm/2.75") $13
      • 2000 Audi TT
      • 2000 BMW 540
      • 2004 Cadillac CTS
      • 2002 GMC Envoy
  • Pepboys and Autozone should stock a wide array of Aftermarket and OEM pulleys to choose from.
  • ACDELCO Part # T42016 is a small steel idler pulley.

Potential Vendors

South Florida Pulley Ring

  • W-Body DUB Pulley Ring
  • Hub Centric Hole 1.41" diameter
  • 4 mounting holes. Create a 2.19" diameter circle.
    • In other words 2.19" across from one hole, to the opposite hole

Boost Calculations

  • Stock EJ25 flows about 225cfm at 6250 redline
  • My upgraded EJ51 is likely closer to 240cfm
  • To make 5.5psi of boost, 330cfm of air is needed.
  • An M62 spinning at 10000rpm should make 335cfm of flow.
  • Estimated Boost
    • Calc 1
      • 5.25" Crank Pulley
      • 3.625" SC Pulley
      • 1.448 Pulley Ratio
      • 1250cc Absolute intake of 2.5L per rev (2500 / 2)
      • 1000cc Absolute volume per rev of SC
      • 1448cc Absolute volume of SC per engine rev (1000 x 1.448)
      • 15.8% increase (1448cc / 1250cc)
      • 2.3psi Boost (1.158 x 14.7psi - 14.7psi)
      • 1.7psi Actual Boost after 25% loss.
    • Calc 2
      • 5.25" Crank Pulley
      • 3.2" SC Pulley
      • 1.64 Pulley Ratio
      • 1250cc engine intake per rev
      • 1000cc SC intake perrev
      • 1640cc volume of SC per engine rev
      • 31.2% increase
      • 4.57psi Boost
      • 3.4psi Boost after 25% loss.
    • Calc 3
      • 5.25" Crank Pulley
      • 3.0" SC Pulley
      • 1.75 Pulley Ratio
      • 1250cc engine intake per rev
      • 1000cc SC intake perrev
      • 1750cc volume of SC per engine rev
      • 40% increase
      • 5.88psi Boost
      • 4.41psi Boost after 25% loss.

Bypass Valve

Clutch Options

  • Redevil has in his SCd wagon a $97 Kennedy 6 puck unsprung disk. With a stock RS pressure plate and a Forester flywheel. He has done many launches and likes how it drives. [Link]
  • Look into the PDM clutch sleeve (repair kit). Something about saving the trans housing if the throw out bearing goes south.
  • For the modest power increase planned, a stock, or stock-ish disk with a stronger pressure plate should be a good combo. Eg,the ACT Street PP
  • or,the reverse, a stock pressure plate, with an upgraded clutch.
  • [ProstreetOnline] has a Excedy kit for $392. Not a bad price.

Wideband AF Monitoring

  • Innovative product won the shootout competition.
  • Would be nice to find a WB setup that can replace the NB 2nd o2 sensor, and output a 0-1v to the ECU.
  • [Zietronix] wideband can do both 0-5v and 0-1v output. Plus, can set the 0-1 to a specific value to fool the ECU.
    • This stuff might be overkill.
  • [PLX-DM5] $269
    • DM100 $189 (or offer) on EBay??? I think this is the gauge ONLY ($209 MSRP)
    • Does 0-5v out and 0-1v out.
    • Don't know if the 0-1v can be spoofed.
  • [Inovative LC1 Kit] $329
    • 0-5v out?
    • 0-1v out?
  • [Just LC1 Controller] $149
    • Would need a 0-5v gauge.
    • Has 2 programmable analog outputs. More info needed....
    • $200 on EBay for LC-1 and a basic gauge.
    • LC-1 & vr-speed $118
      • $167 with WB sensor
  • Basic LC1 Kit] $229
    • Includes controller, sensor and digital only gauge.
  • Avoid AEM, reports that their 0-5v out are NOT linear!!
  • Prosport Digital 52mm Air/Fuel Ratio & Volt Gauge $50
    • Can read a 0-1v or 0-5v signal!!!


  • LC-1 with o2 sensor $158 at VR-Speed
  • ProSport gauge $50 at VR-Speed
  • $208 plus shipping

EManage Ultimate Notes


Very Nice $45 Catch Can

A check valve might be needed, along with a catch can.

Factory NA PCV routing

  • Both valve covers route to air box. The see only a small amount of vacuum.
  • Crank hose runs to PCV in intake.
  • Subaru PCV closes when it sees boost in the intake manifold. This results in air flowing out the valve covers?
  • Stock PCV might need to be relocated. Boost response from an SC might be too fast for a stock PCV.


  • nasioc claims a subaru dealers mechanic said "all hoses need vacuum"
  • PCV System has clean and dirty sides? They should not be combined.
    • Valve cover lines = clean side
    • Crank line = dirty side

Unconfirmed Combination

  • Option 1
    • Valve Cover hoses to Atmo Catch Can for both fresh air, and vent
    • Crank hose to PCV (same as stock)
  • Option 2
    • Remove PCV, and plug intake hole
    • Run all valve cover and crank hoses to atmo catch can
    • Vent the catch can to the intake through the PCV is optional
  • Option 3
    • Connect all hoses to catch can.
    • Other end of catch can through PCV to intake between filter and SC
  • Option 4
    • Crank hose -> T . One end to factory PCV, the other end joined to Valve Cover hoses via T
    • Valve cover hoses routed to T combined with Crank hose
    • Final end of T through PCV to intake between air filter and SC
  • Option 5 <-- Closes to resembling stock and allows for fresh air in.
    • Valve Cover lines to intake between filter and SC
    • Put catch can between crank line and PCV Valve
  • Option 6 (eliminate PCV)
    • Old school valve cover filter on end of Drivers side valve cover line.
    • Run crank case and passenger side valve cover lines to sealed air separator catch can.
    • Run line from Catch can to intake between filter and SC. Slight vacuum draws fumes out.

Reference Links


The Build

2000 Subaru Impreza 2.5RSC Build Part 1