kubernetes cluster node with 4cpu can't hold two pods with 2cpu
It seems like you found your answer but let me add a little color since we went through the same thing.  

Your yaml for the pods can have both a request and limit for both CPU and memory.  Since you are discussing CPU here I'll stick with that.  What you can do in order to utilize your resources efficiently is set your resource request to the minimum requirement to get scheduled. Say 1.8.  But also set the limit to a higher limit, say 2 or more.  What this will do is make your pod be schedulable on the machine and if CPU is not completely consumed, your pod will utilize the available CPU up to 2 or the limit you set.  This is the way kubernetes can make good use of the resources by "sharing" CPU to the application that needs it. 

See here for requests and limits:
https://kubernetes.io/docs/concepts/configuration/manage-compute-resources-container/