diff --git a/docs/impl/reports/Z27AG-CAN-PRIOR-ART.md b/docs/impl/reports/Z27AG-CAN-PRIOR-ART.md
index 15d7c20..83bcd17 100644
--- a/docs/impl/reports/Z27AG-CAN-PRIOR-ART.md
+++ b/docs/impl/reports/Z27AG-CAN-PRIOR-ART.md
@@ -42,8 +42,23 @@ Ralliart's 4G15T is also the forfour Brabus engine, and parts listings show the
 sharing reaches the electrics (Z30 engine ECUs carry Mercedes-style `A135…` part
 numbers; the steering rack is the 454's). The forfour notes bear that out for the
 body bus. Their layouts are the first hypothesis for every shared ID, and their
-engine-side IDs a hint of what a petrol forfour or EU Colt would add. A forfour
-1.5 Brabus or a CZT capture would be the true sibling; none is public. The smart
+engine-side IDs a hint of what a petrol forfour or EU Colt would add.
+
+**The forfour Brabus is the sibling to look for.** EcuTek's [Colt CZT tuning
+manual](https://ecutek.zendesk.com/hc/en-gb/article_attachments/204299089/Mitsubishi_Colt_CZT_-_Tuning.pdf)
+(2005-on "CAN ECUs"): "The Smart ForFour Brabus edition is basically a Colt CZT
+with the fibreglass body"; one ProECU package tunes both. Brabus owners run CZT
+ECUs (MH8304F; ECUFlash definitions exist for CZT ROM 47110032 and Brabus
+49100033, [EvolutionM](https://www.evolutionm.net/forums/ecu-flash/767782-xml-file-smart-brabus-w454.html)).
+So a Brabus's engine-ECU frames should be ours (if the JDM Ralliart's ECU
+matches the EU CZT's), while its body frames come from smart's SAM module: on the
+454 "the SAM … sits at the awkward edge of Mitsubishi engine management and
+Mercedes body electronics" ([smartcarmanuals](https://smartcarmanuals.com/models/454-forfour/)).
+Expect, from a Brabus capture: engine frames equal, chassis frames (ABS, the shared
+electric steering) probably equal, body frames different. No Brabus or CZT capture
+is public; asking an owner for a minute of `candump` at the OBD port is the cheap way
+to get one. The same manual notes that the **Euro CZT has no MAP sensor**, so OBD PID
+`0B` may be unsupported on the Z27 (`obd-poller` discovers that by itself). The smart
 fortwo 451 ([hackaday.io](https://hackaday.io/project/19931-smart-fortwo-can-bus-reverse-engineering))
 shares `423` as the cluster status frame, little else.