Hello Gruntguru
You write:
“Two points.
With four times overcharging the pressure in the exhaust port will be at least 4 bar absolute so the differential pressure acting on the exhaust valve will be 11 bar not 15.
Assuming you start with a 2 litre NA engine capable of 200 bhp (reasonable assumption with unlimited valve timing) the MAP required to produce 600 bhp will be less than 3 bar ie less than 30 psi boost.”
Quote from https://www.koenigse...specifications/
INTERNAL COMBUSTION ENGINE (ICE)
• Koenigsegg Tiny Friendly Giant Twin Turbo Freevalve 3-cylinder Internal Combustion Engine (ICE) with dry sump lubrication
• Compression: 9.5:1 - Bore: 95 mm - stroke: 93.5 mm
• Closed-loop combustion control with in-cylinder pressure sensing
• 440 kW (600 bhp) at 7500 rpm, red line at 8500 rpm
• Torque: 600 Nm from 2000 rpm to 7000 rpm
• ICE is mounted midship and powers the front axle together with one E-motor through a propshaft
• Engine weight: 70 kg
E-MOTORS
• Three Electric Motors: One for each rear wheel with 500 bhp and 1000 Nm each and one E-motor on the crankshaft 400 bhp and 500 Nm to power the front wheels (together with the ICE)
DIMENSIONS
• Total length: 4975 mm
• Total width: 1988 mm (without outer rear-view cameras)
• Total height: 1295 mm
• Wheelbase: 3000 mm
• Fuel capacity: 75 L
• HV Battery: 800 V 16.6 kWh, liquid-cooled
• Dry weight: 1715 kg
• Curb weight: 1850 kg
• Ride Height: 117 mm front, 117 mm rear
• Front lifting system activated: +35 mm
• Total trunk volume (rear and front): 200 L
• Optional roof box
End of Quote
In the following slide (from the above video):
they are shown restoring valve springs (big ones).
At the opening of the exhaust valve, the pneumatic system has to take the force from the pressure inside the cylinder (minus the instant pressure in the exhaust port, which is not, at all conditions of operation, high), it has also to take the inertia of the valve (rev limit 8,500rpm), it has also to take the force of the restoring valve spring.
I.e. the pneumatic system has to operate at high pressure.
From the following plot:
it seems that the extreme power (600PS) of the ICE (Internal Combustion Engine) engine of Gemera is not really significant for its performance (acceleration, final speed).
At peak power, only the 1/3, or so, of the power comes from the ICE, the rest is from the battery.
If instead of 440kW, the engine provides only 90kW peak power, the performance would drop only slightly (760+90 = 850kW instead of 800+400 = 1200kW).
Actually the sum of the peak powers of the three electric motors is not 760kW but ~1000kW, with the one electric motor being on the crankshaft.
What dominates in Koenigsegg’s Gemera is its electric system, not its internal combustion engine; the internal combustion engine is there to charge the battery.
Despite its lightweight engine (only 70Kg), Gemera’s dry weight is 1715 kg.
With 70Kgf weight the Gemera engine makes 440kW (600bhp), which means a specific power of 8.5bhp/Kg (6.3kW/Kg, 3.9bhp/lb).
And this engine is green and fuel efficient.
All the rest engine makers, of super-cars and of normal cars, have a serious problem.
Questions:
For an engine whose main duty is to charge a battery, what is the significance of having one of the most advanced / most variable VVA's?
Shouldn't the engine be tuned at specific revs and load?
For a car that is mainly electric, what is the reasoning of having 600bhp peak power from its ICE?
What about the vibrations from the three big cylinders? (after a period of quiet, vibration free electric cruise, the battery is discharged and the engine is cranked).
So far, is there a free valve engine in a car for tests?
Judging from the specifications of Gemera's engine, shouldn't Koenigsegg start producing, in millions, a smaller version (say, 500cc / 150bhp) of it, and shell it to all automakers ?
Thanks
Manolis Pattakos
