diff --git a/src/muz/spacer/CMakeLists.txt b/src/muz/spacer/CMakeLists.txt
index 68464a40d..162216055 100644
--- a/src/muz/spacer/CMakeLists.txt
+++ b/src/muz/spacer/CMakeLists.txt
@@ -25,6 +25,7 @@ z3_add_component(spacer
   spacer_callback.cpp
   spacer_json.cpp
   spacer_iuc_proof.cpp
+  spacer_mbc.cpp
   COMPONENT_DEPENDENCIES
   arith_tactics
   core_tactics
diff --git a/src/muz/spacer/spacer_mbc.cpp b/src/muz/spacer/spacer_mbc.cpp
new file mode 100644
index 000000000..d002998b3
--- /dev/null
+++ b/src/muz/spacer/spacer_mbc.cpp
@@ -0,0 +1,101 @@
+#include <climits>
+
+#include "muz/spacer/spacer_mbc.h"
+#include "ast/rewriter/rewriter.h"
+#include "ast/rewriter/rewriter_def.h"
+#include "ast/rewriter/th_rewriter.h"
+#include "ast/scoped_proof.h"
+#include "model/model_evaluator.h"
+
+
+namespace spacer {
+
+mbc::mbc(ast_manager &m) : m(m) {}
+
+namespace {
+class mbc_rewriter_cfg : public default_rewriter_cfg {
+
+    ast_manager &m;
+    const mbc::partition_map &m_pmap;
+    model &m_mdl;
+    model_evaluator m_mev;
+    vector<expr_ref_vector> &m_parts;
+    unsigned m_current_part;
+
+    obj_map<expr,expr*> m_subs;
+public:
+    mbc_rewriter_cfg(ast_manager &m, const mbc::partition_map &pmap,
+                     model &mdl, vector<expr_ref_vector> &parts) :
+        m(m), m_pmap(pmap), m_mdl(mdl), m_mev(m_mdl),
+        m_parts(parts), m_current_part(UINT_MAX)
+        {m_mev.set_model_completion(true);}
+
+    br_status reduce_app(func_decl *f, unsigned num, expr * const * args,
+                         expr_ref &result, proof_ref & result_pr) {
+        unsigned part = UINT_MAX;
+        // not a constant
+        if (num != 0) return BR_FAILED;
+        // not in partition map
+        if (!m_pmap.find(f, part)) return BR_FAILED;
+
+        // first part element, remember it
+        if (!found_partition()) {
+            set_partition(part);
+            return BR_FAILED;
+        }
+
+        // decide value based on model
+        expr_ref e(m), val(m);
+        e = m.mk_app(f, num, args);
+
+        // already in our substitution map
+        expr *t = nullptr;
+        if (m_subs.find(e, t)) {
+            result = t;
+            return BR_DONE;
+        }
+
+        // eval in the model
+        m_mev.eval(e, val, true);
+
+        // store decided equality
+        m_parts[part].push_back(m.mk_eq(e, val));
+        // store substitution
+        m_subs.insert(e, val);
+
+        result = val;
+        return BR_DONE;
+    }
+
+    bool get_subst(expr * s, expr * & t, proof * & t_pr) {
+        return m_subs.find(s, t);
+    }
+
+    void reset_partition() {m_current_part = UINT_MAX;}
+    unsigned partition() {return m_current_part;}
+    bool found_partition() {return m_current_part < UINT_MAX;}
+    void set_partition(unsigned v) {m_current_part = v;}
+};
+}
+
+void mbc::operator()(const partition_map &pmap, expr_ref_vector &lits,
+                     model &mdl, vector<expr_ref_vector> &res) {
+    scoped_no_proof _sp (m);
+
+    mbc_rewriter_cfg cfg(m, pmap, mdl, res);
+    rewriter_tpl<mbc_rewriter_cfg> rw(m, false, cfg);
+    th_rewriter thrw(m);
+
+    for (auto *lit : lits) {
+        expr_ref new_lit(m);
+        cfg.reset_partition();
+        rw(lit, new_lit);
+        thrw(new_lit);
+        if (cfg.found_partition()) {
+            SASSERT(cfg.partition() < res.size());
+            res[cfg.partition()].push_back(new_lit);
+        }
+    }
+}
+
+}
diff --git a/src/muz/spacer/spacer_mbc.h b/src/muz/spacer/spacer_mbc.h
new file mode 100644
index 000000000..5dbf50f6d
--- /dev/null
+++ b/src/muz/spacer/spacer_mbc.h
@@ -0,0 +1,45 @@
+/*++
+Copyright (c) 2018 Arie Gurfinkel
+
+Module Name:
+
+    spacer_mbc.h
+
+Abstract:
+
+  Model-Based Cartesian Decomposition
+
+Author:
+
+    Arie Gurfinkel
+
+Revision History:
+
+--*/
+
+#ifndef _SPACER_MBC_H_
+#define _SPACER_MBC_H_
+
+#include "ast/ast.h"
+#include "util/obj_hashtable.h"
+#include "model/model.h"
+
+namespace spacer {
+
+class mbc {
+    ast_manager &m;
+public:
+    mbc(ast_manager &m);
+
+
+    typedef obj_map<func_decl, unsigned> partition_map;
+
+    /**
+       \Brief Model Based Cartesian projection of lits
+     */
+    void operator()(const partition_map &pmap, expr_ref_vector &lits, model &mdl,
+                    vector<expr_ref_vector> &res);
+};
+
+}
+#endif