As of 2016, is there a Scheme implementation which supports 100% of R7RS (small) with no deviations?

The Chairman of R7RS Small Language ("Working Group 1") committee, Alex Shinn, created Chibi Scheme as the standard evolved. I believe it is fully compliant. It is a bytecode compiler.

Larceny has a mostly (totally?) compliant R7RS mode, and compiles to machine code.

I have been playing with Picrin which aims for R7RS compliance, and is very very close. It is a bytecode compiler.

A list of implementations that are aiming for R7RS compliance at the committee's wiki include:

• Chibi
• Chicken (partial)
• Foment
• Gauche
• Guile (partial)
• Husk
• Kawa
• Larceny
• Mosh (partial)
• Picrin
• Sagittarius

Although the question explicitly excludes Racket from consideration as not being Scheme I will point to Racket package "R7RS" which implements R7Rs small.

There are some small incompatibilities documented on project's page.