diff --git a/sysid/src/main/native/cpp/view/DataSelector.cpp b/sysid/src/main/native/cpp/view/DataSelector.cpp
index c160490889f..c5bc6a30c7e 100644
--- a/sysid/src/main/native/cpp/view/DataSelector.cpp
+++ b/sysid/src/main/native/cpp/view/DataSelector.cpp
@@ -155,7 +155,9 @@ DataSelector::Tests DataSelector::LoadTests(
     std::string_view prevState;
     Runs* curRuns = nullptr;
     wpi::log::DataLogReader::iterator lastStart = range.begin();
+    int64_t ts = lastStart->GetTimestamp();
     for (auto it = range.begin(), end = range.end(); it != end; ++it) {
+      ts = it->GetTimestamp();
       std::string_view testState;
       if (it->GetEntry() != testStateEntry.entry ||
           !it->GetString(&testState)) {
@@ -165,7 +167,7 @@ DataSelector::Tests DataSelector::LoadTests(
       // track runs as iterator ranges of the same test
       if (testState != prevState) {
         if (curRuns) {
-          curRuns->emplace_back(lastStart, it);
+          curRuns->emplace_back(lastStart->GetTimestamp(), ts);
         }
         lastStart = it;
       }
@@ -189,7 +191,7 @@ DataSelector::Tests DataSelector::LoadTests(
     }
 
     if (curRuns) {
-      curRuns->emplace_back(lastStart, range.end());
+      curRuns->emplace_back(lastStart->GetTimestamp(), ts);
     }
   }
   return tests;
@@ -208,34 +210,75 @@ static void AddSample(std::vector<MotorData::Run::Sample<T>>& samples,
   } else {
     float val;
     if (record.GetFloat(&val)) {
-      samples.emplace_back(units::second_t{record.GetTimestamp() * 1.0e-6},
-                           T{static_cast<double>(val * scale)});
     }
   }
 }
 
+template <typename T>
+static void AddSamples(std::vector<MotorData::Run::Sample<T>>& samples,
+                       const std::vector<std::pair<int64_t, double>>& data,
+                       int64_t tsbegin, int64_t tsend) {
+  // data is sorted, so do a binary search for tsbegin and tsend
+  auto begin = std::lower_bound(
+      data.begin(), data.end(), tsbegin,
+      [](const auto& datapoint, double val) { return datapoint.first < val; });
+  auto end = std::lower_bound(
+      begin, data.end(), tsend,
+      [](const auto& datapoint, double val) { return datapoint.first < val; });
+
+  for (auto it = begin; it != end; ++it) {
+    samples.emplace_back(units::second_t{it->first * 1.0e-6}, T{it->second});
+  }
+}
+
+static std::vector<std::pair<int64_t, double>> GetData(
+    const glass::DataLogReaderEntry& entry, double scale) {
+  std::vector<std::pair<int64_t, double>> rv;
+  bool isDouble = entry.type == "double";
+  for (auto&& range : entry.ranges) {
+    for (auto&& record : range) {
+      if (record.GetEntry() != entry.entry) {
+        continue;
+      }
+      if (isDouble) {
+        double val;
+        if (record.GetDouble(&val)) {
+          rv.emplace_back(record.GetTimestamp(), val * scale);
+        }
+      } else {
+        float val;
+        if (record.GetFloat(&val)) {
+          rv.emplace_back(record.GetTimestamp(),
+                          static_cast<double>(val * scale));
+        }
+      }
+    }
+  }
+
+  std::sort(rv.begin(), rv.end(),
+            [](const auto& a, const auto& b) { return a.first < b.first; });
+  return rv;
+}
+
 TestData DataSelector::BuildTestData() {
   TestData data;
   data.distanceUnit = kUnits[m_selectedUnit];
   data.mechanismType = analysis::FromName(kAnalysisTypes[m_selectedAnalysis]);
-  bool voltageDouble = m_voltageEntry->type == "double";
-  bool positionDouble = m_positionEntry->type == "double";
-  bool velocityDouble = m_velocityEntry->type == "double";
+
+  // read and sort the entire dataset first; this is memory hungry but
+  // dramatically speeds up splitting it into runs.
+  auto voltageData = GetData(*m_voltageEntry, 1.0);
+  auto positionData = GetData(*m_positionEntry, m_positionScale);
+  auto velocityData = GetData(*m_velocityEntry, m_velocityScale);
 
   for (auto&& test : m_tests) {
     for (auto&& state : test.second) {
       auto& motorData = data.motorData[state.first];
-      for (auto&& range : state.second) {
+      for (auto [tsbegin, tsend] : state.second) {
         auto& run = motorData.runs.emplace_back();
-        for (auto&& record : range) {
-          if (record.GetEntry() == m_voltageEntry->entry) {
-            AddSample(run.voltage, record, voltageDouble, 1.0);
-          } else if (record.GetEntry() == m_positionEntry->entry) {
-            AddSample(run.position, record, positionDouble, m_positionScale);
-          } else if (record.GetEntry() == m_velocityEntry->entry) {
-            AddSample(run.velocity, record, velocityDouble, m_velocityScale);
-          }
-        }
+        AddSamples(run.voltage, voltageData, tsbegin, tsend);
+        AddSamples(run.position, positionData, tsbegin, tsend);
+        AddSamples(run.velocity, velocityData, tsbegin, tsend);
       }
     }
   }
diff --git a/sysid/src/main/native/include/sysid/view/DataSelector.h b/sysid/src/main/native/include/sysid/view/DataSelector.h
index 95d7e197d3b..dc4b91d2601 100644
--- a/sysid/src/main/native/include/sysid/view/DataSelector.h
+++ b/sysid/src/main/native/include/sysid/view/DataSelector.h
@@ -8,6 +8,7 @@
 #include <future>
 #include <map>
 #include <string>
+#include <utility>
 #include <vector>
 
 #include <glass/View.h>
@@ -57,7 +58,7 @@ class DataSelector : public glass::View {
 
  private:
   // wpi::Logger& m_logger;
-  using Runs = std::vector<glass::DataLogReaderRange>;
+  using Runs = std::vector<std::pair<int64_t, int64_t>>;
   using State = std::map<std::string, Runs, std::less<>>;   // full name
   using Tests = std::map<std::string, State, std::less<>>;  // e.g. "dynamic"
   std::future<Tests> m_testsFuture;