diff --git a/hbs2-peer/app/PeerMain.hs b/hbs2-peer/app/PeerMain.hs
index d091876d..7ba173b3 100644
--- a/hbs2-peer/app/PeerMain.hs
+++ b/hbs2-peer/app/PeerMain.hs
@@ -1203,7 +1203,7 @@ runPeer opts = respawnOnError opts $ do
                 peerThread "pexLoop" (pexLoop @e brains tcp)
 
                 -- FIXME: new-download-loop
-                peerThread "blockDownloadLoop" (blockDownloadLoop denv)
+                -- peerThread "blockDownloadLoop" (blockDownloadLoop denv)
 
                 peerThread "blockDownloadQ" (downloadQueue conf (SomeBrains brains) denv)
 
diff --git a/hbs2-peer/app/RPC2.hs b/hbs2-peer/app/RPC2.hs
index 5f3a8560..4fe06e8f 100644
--- a/hbs2-peer/app/RPC2.hs
+++ b/hbs2-peer/app/RPC2.hs
@@ -55,6 +55,8 @@ import PeerInfo
 import Control.Monad.Trans.Maybe
 import Control.Monad.Trans.Cont
 import Control.Concurrent.STM (flushTQueue,retry)
+import Data.Map qualified as Map
+import Data.Map (Map)
 import Data.HashSet (HashSet)
 import Data.HashSet qualified as HS
 import Data.IntMap qualified as IntMap
@@ -169,6 +171,105 @@ queryBlockSizeFromPeer cache e h peer = do
     Right x -> pure (Right x)
 
 
+data BurstMachine =
+  BurstMachine
+  { _buTimeout  :: Double
+  , _buBurstMax :: Int
+  , _buStepUp   :: Double
+  , _buStepDown :: Double
+  , _buCurrent  :: TVar Double
+  , _buErrors   :: TVar Int
+  }
+
+burstMachineAddErrors :: MonadUnliftIO m => BurstMachine -> Int -> m ()
+burstMachineAddErrors BurstMachine{..} n =
+  atomically $ modifyTVar _buErrors (+n)
+
+newBurstMachine :: MonadUnliftIO m
+                => Double      -- ^ timeout
+                -> Int         -- ^ max burst
+                -> Maybe Int   -- ^ start burst
+                -> Double      -- ^ step up
+                -> Double      -- ^ step down
+                -> m BurstMachine
+
+newBurstMachine t0 buMax buStart up' down' = do
+  BurstMachine t0 buMax up down
+    <$> newTVarIO bu0
+    <*> newTVarIO 0
+
+  where
+    bu0 = realToFrac $ fromMaybe (max 2 (buMax `div` 2)) buStart
+    down = min 0.85 down'
+    up   = min 0.5 up'
+
+getCurrentBurst :: MonadUnliftIO m => BurstMachine -> m Int
+getCurrentBurst BurstMachine{..} = readTVarIO _buCurrent <&> round
+
+runBurstMachine :: MonadUnliftIO m
+                => BurstMachine
+                -> m ()
+
+runBurstMachine BurstMachine{..} = do
+
+  pause @'Seconds ( 0.5 * 2.71 )
+
+  bu0  <- readTVarIO _buCurrent <&> realToFrac
+  let buMax = realToFrac _buBurstMax
+  let down  = _buStepDown
+  let up    = _buStepUp
+
+  _dEdT <- newTVarIO 0.00
+
+  _rates <- newTVarIO (mempty :: Map Double Double)
+
+  _buMaxReal <- newTVarIO buMax
+
+  flip runContT pure do
+
+    void $ ContT $ withAsync do
+      forever do
+        pause @'Seconds (realToFrac _buTimeout * 10)
+
+        atomically do
+          e <- headDef bu0 . Map.elems <$> readTVar _rates
+          writeTVar _rates mempty
+          modifyTVar _buMaxReal (max e)
+          -- writeTVar _buCurrent e
+
+    void $ ContT $ withAsync do
+      forever do
+        pause @'Seconds 600
+        atomically $ writeTVar _buMaxReal buMax
+
+    forever do
+
+      e1 <- readTVarIO _buErrors
+
+      let dt = realToFrac _buTimeout
+
+      pause @'Seconds dt
+
+      atomically do
+
+        e2      <- readTVar _buErrors
+        current <- readTVar _buCurrent
+        buMaxReal <- readTVar _buMaxReal
+
+        let new = if e2 > e1 then
+                    max 2.0 (current * (1.0 - down))
+                  else
+                    min buMaxReal (current * (1.0 + up))
+
+        writeTVar _buErrors 0
+        writeTVar _buCurrent new
+
+        let dedt = realToFrac (e2 - e1) / realToFrac dt
+
+        writeTVar _dEdT (realToFrac dedt)
+
+        modifyTVar _rates ( Map.insertWith max dedt current )
+
 data S =
     SInit
   | SFetchQ
@@ -198,6 +299,8 @@ downloadFromPeerRec t bu0 cache env h0 peer = do
   q <- newTQueueIO
   qq <- newTQueueIO
 
+  bm <- newBurstMachine 3.00 256 (Just bu0) 0.05 0.10
+
   flip runContT pure do
 
     ContT $ withAsync $ forever do
@@ -208,6 +311,8 @@ downloadFromPeerRec t bu0 cache env h0 peer = do
       void $ queryBlockSizeFromPeer cache env h peer
       pause @'Seconds 1.5
 
+    ContT $ withAsync $ runBurstMachine bm
+
     flip fix SInit $ \next -> \case
 
       SInit -> do
@@ -226,6 +331,7 @@ downloadFromPeerRec t bu0 cache env h0 peer = do
           pe <- isEmptyTQueue p
           qe <- isEmptyTQueue q
           when (qe && not pe) retry
+          -- when (not pe) retry
           pure qe
 
         if done then
@@ -239,13 +345,15 @@ downloadFromPeerRec t bu0 cache env h0 peer = do
             Just bs -> next (SFetchPost h bs)
             Nothing -> none
 
-          w <- lift $ downloadFromPeer t bu0 cache env (coerce h) peer
+          bu <- lift $ getCurrentBurst bm
+          w  <- lift $ downloadFromPeer t bu cache env (coerce h) peer
 
           case w of
             Right bs -> do
               next (SFetchPost h bs)
 
             Left e -> do
+             lift $ burstMachineAddErrors bm 1
              err $ "DOWNLOAD ERROR" <+> viaShow e
              next SFetchQ
 
@@ -335,7 +443,7 @@ downloadFromPeer t bu cache env h peer = liftIO $ withPeerM env do
 
         let watchdog = fix \next -> do
              s1 <- readTVarIO _sBlockChunks2 <&> IntMap.size
-             pause @'MilliSeconds ( max (realToFrac chunkN * rtt) 2000 )
+             pause @'MilliSeconds ( 1000 )
              s2 <- readTVarIO _sBlockChunks2 <&> IntMap.size
              when (s1 /= s2)  next