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Location:
Melbourne
Registered:
August 2002
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 Re: 1GGZE Crank pulley Diameter???
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Thu, 15 August 2002 09:03
 
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length width height weight displacement
SC14 85-89+ 1G-GZE 311mm 148mm 254mm 11.9kg 1420cc
SC12 86-89+ 4A-GZE ~249 148mm 254mm 10.8kg 1200
Both of these superchargers are roots-type positive displacement superchargers. The rotors are fluorine resin coated. The units have their own lubricating oil, 130cc. Stock boost is regulated to about 0.7 bar, and the units are normally driven at 1.25 times crank speed (4A-GZE has a 7500rpm redline). Oversize pulleys are available. The stock crank pulley on 4A-GZE is 145mm in diameter, the HKS pulley 157mm.
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
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