Tech:Engine/K Series/Boosted K motors

Due to popular demand I am going to endevour to write up a new section here for boosted K motors.

This is going to be a work in progress and may take me a little while to complete it so please bare with me while I get it done. Once its completed this message will be deleted.

Cheers, Si (Taz_RX)

Firstly, obviously there are two way to build a "Boosted K motor" by using a turbo or a supercharger. For deffinitions or how each work (if you don't know and are intersted) please do a wiki/google search.

Superchargers:

What to use: The most common superchargers used on K motor are Toyota SC12 (4AGZE) and SC14 (1GGZE) units. These are readily available from import motors, wreckers etc and are quite reasonable priced. Others have used other SC's like the AMR300 or AMR500 however both of these units are quite smaller compared to the SC chargers. This isn't to say they won't work though, its just by the time you get up in the revs a bit the small capacity of the charger may restrict top end flow. At the other end of the scale you could use a bigger charger like and Eaton M series (M90 from S pac supercharged commodore for example) which geared correctly could give great top end flow, however some boost lag would be expected in the bottom end of the rev range. Choosing the size of the charger, and the gearing used is just like picking a cam shaft or turbo A/R ratio. It really depends on what you want to use the car for and where you want your power range.

How to mount it: The easiest way to hang a SC off a K motor is to source yourself an air-conditioning bracket off any K motor. With a few minor mods to the bracket and/or the charger itself you can mount the charger in the position normally occupied by the A/C pump. As the mechanical fuel pump attaches to the block inside the A/C bracket, removing the pump and blocking its mounting point with a plate would be required. You should be upgrading your fuel system anyway so this won't be an issue. As the geometry on how the charger is mounted (compared to stock) some custom pipe work to the inlet and outlet would be required to suit your application.

Connecting a belt: K series motors use a "V belt" and most SC's (including Toyota SC12/14) use a "Ribbed belt", obviously this poses an issue of getting drive to the SC. You either need to convert the pulley on the SC to V-belt, or convert the existing K belt arangement to ribbed-belt. Another thing to bare in mind when chossing this setup is the fact that the Toyota SC12/14 have a electronically activated clutch pulley. If you want to retain this clutch (to be able to de-activate the SC) you'll have to get a bit crafty with the belt setup. As my personal experience is with turbos not chargers I'm going to PM some members here and ask how they went about the belt setups. Hopefully I'll have a run down of how to use both V-belts or ribbed-belts once I've heard back from these members.

Gearing the Supercharger: I've copied and pasted to below info from a post by 1JZke55:

When fitting a supercharger, you should match the swept volume of the supercharger to the size of the engine. If the choice is made carefully, problems from overboosting and the required paraphenalia to solve these problems will be minimised. The supercharger will also be kept in its safe operating speed with correct selection.

To choose a setup you need to know :- 1. Engine capacity 2. Maximum engine speed you will be using. 3. Boost level desired

I am setting out the calcs needed for a 1200cc engine in the steps below.

FIRST CALCULATION (Engine Litres/min @ 0 Psi ) Multiply engine capacity (in litres) times maximum engine Rpm. E.g. 1.2 litres x 6000 rpm = 7200 litres/minute. Divide this figure by two as engine only fills every second stroke. (7200/2 = 3600 litres/min. This is the engines air requirements in litres/minute at 0 Psi boost.

SECOND CALCULATION (boost ratio) Add the boost pressure desired (7 Psi) for the engine to 14.7 Psi (atmospheric pressure). (7 psi boost desired +14.7 =21.7 psi) Divide this answer by 14.7 and this gives the boost pressure ratio. (21.7/14.7=1.476) This is the boost pressure ratio above atmospheric pressure.

THIRD CALCULATION (Actual air requirements @ desired boost)

Multiply the boost ratio by the litres/minute obtained for 0 Psi and you get the actual air requirements in Litres/min for the engine at that boost. In our example this is 3600 litres/min X 1.476 = 5313.6 litres/min for 7Psi boost.

To decide on the correct size of supercharger you need to know :- 1. The swept volume per revolution of the supercharger. (Eaton M62 1 litre/rev, SC14 from a 1G-GZE 1.5 litres/rev, SC12- 1.2 L/rev) 2. The maximum continuous safe operating speed for the supercharger. (Eaton M62 14000 rpm continuous, Toyota SC14 12000 rpm??) 3. The maximum pressure that can be safely produced by the supercharger continuously. (Eaton M62 12 psi, SC14 10-12Psi??? teflon on rotors melts??)

CALCULATION (Supercharger rotor speed) Divide the desired air flow (5313.6 L/min) by the swept volume of the supercharger (SC14 from the 1G-GZE is 1.5 litres per revolution). This will tell you the maximum speed the supercharger rotors must be run at to produce the volume required. 5313.6/1.5 litres = 3542.4 rpm for the SC14. 5313.6/1 litre = 5313.6 rpm Eaton M62

CALCULATION (Pulley size ratio) Divide the rotor Rpm by maximum desired engine rpm to get the drive ratio of the pulleys. For an SC14 on a 1200 @ 7psi boost the desired supercharger pulley ratio is 3542.4 /6000 rpm = 0.5904.

EXAMPLE OF CHANGE OF DRIVE RATIO If the 1200 cc engines supercharger pulley ratio is increased to 0.75 using the 1.5 ltr/rev SC14 charger, the volume of air produced when running to 6000 would be 6000 x 0.75 x 1.5 litres =6750 litres/min

Boost produced would be 6750 litres/3600 litres (at 0 boost) =1.875 boost ratio For Psi boost ((1.875 x 14.7) - 14.7)=12.86 Psi.

if you want to get even more technical the sc14 is actually 1.42

As 1JZke55 illuded to above apparently the Toyota SC12 and SC14 have teflon coated rotors and don't like being spun to about 14psi. I'm not sure if this is a shaft speed or general pressure problem but apparently the teflon can chip/flake off the rotors and cause a loss of compression. Hopefully somebody will read this and give us a definative answer!!!??? PM me (Taz_RX) if you do.