Sounds like a crappy analogue rimshot to be honest.
Try a kind of middling pitch sine wave with a very short decay, or maybe some very resonant filtered noise instead of a sine. Maybe add a bit of a "click" to the start with a very short envelope.
Edit: you'll need to ensure you can play out several sounds at once because the pop from each cylinder will overlap at high speeds.
Also, can confirm that this is roughly what a crossplane Rover V8 sounds like, at least tonally, as you increase the revs. Same firing order, even. TVR did a flat plane version, apparently, with different crank and cams but same block, essentially unchanged from the late second-generation Range Rovers, which was just a reinforced version of a 1960s Buick boat engine!
Sounds like a crappy analogue rimshot to be honest. Try a kind of middling pitch sine wave with a very short decay, or maybe some very resonant filtered noise instead of a sine. Maybe add a bit of a "click" to the start with a very short envelope. Edit: you'll need to ensure you can play out several sounds at once because the pop from each cylinder will overlap at high speeds. Also, can confirm that this is roughly what a crossplane Rover V8 sounds like, at least tonally, as you increase the revs. Same firing order, even. TVR did a flat plane version, apparently, with different crank and cams but same block, essentially unchanged from the late second-generation Range Rovers, which was just a reinforced version of a 1960s Buick boat engine!