Toyota SC-14 Supercharger

Toyota SC-14 Supercharger

Description and Operation

Both of these superchargers are roots-type positive displacement= superchargers.

The rotors are fluorine resin coated. The units have their own lubricati= ng oil, =20 130cc. Stock boost is regulated to about 0.7 bar, and the units are normall= y=20 driven at 1.25 times crank speed (4A-GZE has a 7500rpm redline). Oversize= pulleys are available.

The Toyota 4-AGZE motor was used in the 86-89 MR2 Supercharged edition M= R2s. The motor is a modified 4-AGE unit coupled to an electronically engage= d roots type supercharger manufacturer currently unverified) and a Nippon D= enso air-to-air intercooler. Static compression ratio of the motor was drop= ped from 9.4:1 to 8.0:1. The camshafts are identical to a normally aspirate= d car, although their timing may be different. The motor is fitted with a d= ifferent type of injector with a higher flow capacity. Boost level is set a= t 8 PSI and achieved at 4000 RPM and higher, however the supercharger creat= es usable boost from idle through redline.

The supercharger is driven by a serpentine belt off of the crankshaft an= d shares=20 its drive belt with the water pump.

The supercharger adds heat to the intake charge both by conduction of ho= using heat since the supercharger is bolted onto the engine and also by pre= ssurizing the intake charge. With the bypass valve open and the supercharge= r disengaged the intake system raises the intake charge temperature by abou= t 30 degrees F once everything is up to operating temperature. Running unde= r full boost with an outside air temperature of 50 degrees F the air temper= ature of the SC outlet can get as high as 270 degrees.

Vent holes are placed at three points in the housing. One in the rear ge= ar housing and one to each of the shaft ends of the vanes on the front of t= he supercharger. The vents are all connected together via external metal tu= bes and hosing. An air valve is connected to all the vents, which can purge= them to the intake system after the airflow meter but before the throttle = body.

Supercharger Clutch

The supercharger clutch works in the same way as an air conditio= ning compressor clutch. The pulley itself spins freely on the supercharger-= input shaft. A coil=20 of wire sits behind the pulley and a metal disc sits in front. The front di= sc is connected to the actual input shaft of the supercharger. When the coi= l is energized, the disc is drawn against the rotating pulley and they then= rotate together as a unit until the coil is de-energized.

The manufacturer intended this clutch to be operated based on intake man= ifold vacuum.=20 If vacuum drops below 8"Hg the supercharger clutch is engaged. The clutch s= hould stay on=20 until the intake manifold vacuum has risen to over 10"Hg for a period of 5 = seconds. This time delay is required to avoid cycling of the clutch during = shifts and momentary throttle transitions. A delay circuit is required to r= eplicate this behaviour when fitting these units to other vehicles

The manifold vacuum during highway driving will be low enough that the S= C clutch will stay engaged all the time with an appropriate controller circ= uit of this type

Physical and Functional Data

Type Year Model Length Width Height Weight = Displacement

SC14 85-89+ 1G-GZE 311mm 148mm 254mm 11.9kg = 1420cc

SC12 86-89+ 4A-GZE ~249 148 254mm 10.8kg = 1200cc

Maintenance Data

Supercharger bearings

For the small bearing (shorter shaft, sealed only one side)

Koyo part number: 03NU0514-7

Inner diam: 0.668"

Outer diam: 1,772"

Thickness: 0.548"

For the thicker one, sealed both sides

Number unreadable, but seal number 03NU0518-2 (the "8" is a guess)

Same inner and outer diameter,

Thickness: 0.705"

10,000rpm +

Lubricant

The gears are run in Toyota supercharger oil, Toyota part number= 08885-80108. Total gear housing capacity is 130ml. Other types of lubrican= ts may work satisfactorily. It is not unreasonable to expect a decent hypoi= d gear oil to work. A 90-weight synthetic gear oil appears to be the closes= t commonly available equivalent.

Disassembly

Two special tools are required for disassembly of the supercharg= er; SST 09504-00011 for keeping the pulley from rotating while you undo the= nut that holds the clutch hub to the supercharger. If you have an impact w= rench you might be able to get by without this for removal. However you wil= l still need something to hold the pulley when you tighten the nut down upo= n re-assembly. SST 09814-22010 for removing the ring nut that holds the clu= tch pulley on. You can't get by without this short of having a set of ring = nut sockets or custom building the equivalent tool.

Calculating Blower Characteristics

Assuming the same blower:crank RPM ratio, and assuming the same = inlet/outlet

temps,

Pbig =3D Psmall * (Dbig / Dsmall)

Psmall =3D boost pressure with small blower in *absolute* units

Dsmall =3D displacement of small blower, any units

Dbig =3D displacement of big blower, same units as above

Pbig =3D boost pressure, in absolute units, with big blower

If you had 10 psi with the SC12. That's 24.7 psia at sea level.

With an SC14. (1.42L vs. 1.2L )

24.7 * (1.42 / 1.20) =3D 29.2 psia, or 14.5 psi boost at sea level.

This is only a basic calculation and doesn=92t take into account tempera= ture and altitude

www.thermactor.com/?f

The supercharger oil is around $35.00 (US) per kit
Kit comes with 2oz can of oil and a filler pump.

There is no substitute for the s/c oil… You must get the toyota oil!

I don't know what is in it, but is good stuff

The service intervals for the s/c oil is 60,000 miles. But it is a good idea to check the level of oil at every engine oil change to make sure you are not low.