So much misinformation. A flat plane crank has PERFECT primary balance. The secondary imbalance is caused by the stroke itself because the piston doesn't move with a constant speed and instead the connecting rod itself pulls on it and then pushes on it because of its angle. A flat plane crank shaft has BOTH primary AND secondary imbalances and it's actually HARDER to balance out and that's why a cross plane crank shaft is thicker and heavier with various balance shafts. In a v8 configuration, the cross plane will achieve secondary balance IF it's a 90° V but its primary balance will still be shitty and require heavy counterweights. The reason that cross plane exists in i4 engines is to space out firings and give tyres more time to recover similar to a shared pin v4. In v8 engines the only advantage of a cross plane is the lack of secondary vibrations. Exhaust pulses have nothing to do with what RPMs the engine is happy at and crankshaft design has nothing to do with where the torque comes in. You can make a flat plane engine have torque down low and a cross plane to have all its power at peak RPMs. Exhaust scavenging works to enhance the power band of an engine and maybe even broaden it, it doesn't change it. What is inherent to crankshaft design is peak RPM, not the powerband. While a cross plane will peak at around 7 to 7.5k RPM, it can be set to have its power come that high and at the same time a flat plane will naturally rev to 9.5-10k RPM but it can be set to have its power come in much lower in the power band, it's just not optimal. Firing interval is different in i4 engines between flat and cross plane but in a 90° v8 engines, both crank shaft designs have a firing pulse every 90° of crank shaft rotation, it's just that the interval is irregular per bank and that's why exhaust scavenging is sub optimal in cross plane v8s, because the headers are split into two banks. If you join the exhaust headers down the line into one pipe, both engines will sound the same. A cross plane crank i4 does not have a smoother power delivery, it has a more docile power delivery, because of the irregularly spaced power pulses, contrary to a flat plane, which has evenly spaced power pulses and it does indeed have a smooth power delivery. The advantage of the cross plane is that, like mentioned above, it gives the tires more time to recover grip because of the longer pause and helps manage the power easier than the constant power stream of a flat plane. This advantage only applies to motorcycles because they have very limited grip. In v8 engines both crank shaft configurations have the same power delivery. Seriously, do not spread so much misinformation.
Hi. Very good video - thanks for that. Could you include a simulation - and the soundtrack - of a V12 (e.g. Jaguar V12) in a future video, please? Thanks. Peter
2:45 Sorry, not a flat plane crank i4 rather in twin cylinder 180 degree and V4 of the Aprilia but if is car the best sound = twin cylinder 180 degree and V4 Aprilia (Motorcycles). 3:41 Half crossplane (Engine Sound) half flatplane (Exhaust Sound)!
I4 doesnt have primary vibration issue, secondary vibration not caused by "crankpin weight" and crossplane i4 doesnt have "smoother power delivery" - quite the opposite in reality. Uneven pulses = uneven torque delivery... wtf is this nonsense :D
Cross plane was the answer to weak flat plane cranks in the first place. Cross plane crank engines are capable of more overall power by about double no matter how well suited materials become. It's just a superior design durability wise. With low power engines you may as well save on material quantity so a flat plane will do.
Crossplane are a mess is balance and firing order, they cannot rev over 6000rpm, giant counterbalance on giant crankshaft, big space big weight, they got nice sounds for the consecutive double firing per bank.
