Jonas Olhssons BMW 1602
- BMW M10
- 4 cyl, OHC, 2 valves/cyl
- 90.5 mm Mahle flat-top forged pistons
- 2.0 litre crank (with over-bore 2.05 litres)
- Stock rods
- No squish area left, bad for fuel economy, good for boost
- 7.5 : 1 compression ratio
- Schrick cam shaft (328/316 intake/exhaust degrees duration)
- Individual Throttle Bodies (50 mm)
- Ford Motorsport 1600 cc/min fuel injectors, 5 Ohm impedance
- Run in saturated mode
- No power resistors
- 30 V TS diode on the flyback wire
- This is proven method for these injectors (Emil has done many)
- Stock distributor with heavy duty coil and MSD 6A CDI box
- Custom aluminum trigger wheel on the crank, two metal points for simple trigger using Honeywell GT1 Hall-sensor
- Long tubular turbo exhaust manifold
- Holset HX50 turbo, 63 in/72 out with 22 cm² exhaust housing.
- Large front mount intercooler
- Two piston controlled wastegates (will be replaced with diaphragm based single wastegate for better control)
Intake Design Issue
The Large throttles and the placement of the fuel injectors results in very hard to handle low load.
- No good load metering for Alpha-N nor Speed-Density
- Uphill and downhill driving share the same load site
- Fuel injection is done right before each throttle, at the floor of the runner. Fuel will puddle on the intake runner wall, before the throttle.
Better design would be:
- Fuel injectors placed at the head
- Single throttle blade
Better construction would be to use two injectors per runner.
- small one, near cylinder head and large (for the better fuel atomization) in the end of the runner at the upper plenum chamber
- plenum design plays an important role, evenly balanced air distribution wise.
Good design; Throttle body mounted to 'lower plenum', connected via narrow air flow channel which has same length as the both plenums to the 'upper plenum' where the runners end cone and large injectors are located.
Compromise for the time being:
- Tune for WOT (main purpose of the car)
- Let lambda/EGO correction fix some of the low load problems