This paper summarizes efforts to integrate, for the first time, two geographically-dispersed hardware-in-the-loop simulation setups over the Internet in an observer-free way. The two setups are the engine-in-the-loop simulation setup at the University of Michigan (UM) in Ann Arbor, MI, USA, and the driver-in-the-loop ride motion simulator at the US Army Tank-Automotive Research, Development and Engineering Center (TARDEC) in Warren, MI, USA. The goal of this integration is to increase the fidelity of experiments and to enable concurrent engineering. First, a model-based simulation of the setup is utilized to analyze the effects of variable delay, an intrinsic characteristic of the Internet, on the integrated system, particularly in terms of stability, robustness, and transparency. Then, experiments with the actual hardware are presented. The conclusion is that the two pieces of hardware can indeed be integrated over the Internet without relying on observers in a stable and subjectively transparent manner, even if the nominal delay is increased by four times.