We have seen a rise in demand for popcorn limiters on diesel vehicles. A popcorn limiter basically changes the way a diesel car behaves when the engine hits the rpm limiter. Most stock diesel vehicles will hit the pre-set rpm limiter and will stay at that exact rpm point until the driver intervenes (soft cut limiter). However, with a popcorn limiter applied the engine will bounce at the limiter in a similar way to a petrol vehicle (hard cut limiter).