List of differences between the CJAA and CBEA engine in Audi A3, Golf, and Jetta TDI
The CJAA engine is used in 2010 and newer VW Golf, Jetta, Sportwagen TDI. The CBEA is used in the 2009 VW Jetta TDI and 2010, 2011 Audi A3 TDI. Why does the Audi A3 still use the CBEA? No clue but this has been confirmed by users. You can view your engine code as a 3 letter code on a white sticker on top of the timing belt cover (passenger side)
I decided to spend the afternoon trying to figure out exactly what the differences are other than the engine codes and here are the differences I found according to the parts catalog. There may be some variance during the transitions periods.
What's the same in CJAA vs. CBEA engines:
front and rear crank oil seals
oil pan (also same as BRM engine))
engine plastic beauty cover
connecting rod bearings
crankshaft timing belt sprocket
crankshaft pulley (harmonic balancer pulley/AC pulley)
camshafts and valves
oil filter and housing
water pump and thermostat
fuel pump, injectors, and fuel rail
turbo and intercooler
What's different in the CJAA engine vs. the CBEA engine:
cjaa has windage tray in oil pan
oil dipstick and tube
cylinder head valve cover
crankshaft - my best guess is that the difference is the gear for the balance shaft.
front crankshaft drive gear for balance shaft
fuel filters (see 1000q: crd TDI fuel filters for details)
The CJAA DPF and NOx catalyst are 2 separate pieces/part numbers connected with a v-band clamp. The CBEA DPF and NOx catalyst are 1 piece, no clamp. See 1000q: DPF FAQ for pictures of the exhaust and more details.
balance shaft module. It appears that CBEA built during 2009 use part # 03g 103 295 k (03g103295k). CBEA engines built during 2010 and later and CJAA engines use 03g 103 295 ak (03g103295ak). The exception is the Audi A3 which always uses the AK suffix module. NOTE: Although the CJAA has a balance shaft module listed, the CJAA does NOT have any balance shaft module. This is confirmed from people taking the oil pan off.
I don't know if there's a physical difference in the modules but the drive gear on the crankshaft is different on K vs. AK modules. Also, K should take one type of intermediate gear (gear between the crankshaft drive gear and balance shaft drive gear) and AK should take another. The 3rd gear which drives the balance shaft is the same on K vs. AK. What's confusing is that according to the parts manual, K gears are found on AK modules in the Audi A3 TDI. This is either a mistake or it means they are interchangeable. My best guess is that the gears are all interchangeable as a set and are the same except for the crankshaft sprocket gear because of how it mounts to the crankshaft. Keeping the number of teeth the same is important because it drives the balance shaft and the oil pump. If the teeth were different, the balance shafts would be thrown off and the engine would shake.
Attached is a picture showing the gears I'm describing on a similar engine.
oil pump - the oil pump is driven by a shaft from the balance shaft module.
The cjaa has a 77mm oil pump drive shaft, cbea has 100mm. The exception is the Audi A3 TDI oil pump. These are all CBEA engines but if built before 10-19-09, they use a 77mm shaft. Later shafts are 100mm. Because all Audi A3 have the CBEA engine and AK balance shaft module according to the parts catalog, my best guess is that the oil pumps are interchangeable between the K and AK balance shaft modules and that both K and AK balance shafts are interchangeable between CBEA engines and CJAA engines.
EDIT: now that I've seen the crank of a CJAA from a Golf after the oil pan was removed, and the parts manual has changed some info, the CJAA does not have ANY balance shaft. I don't know why it was removed, there was probably a miscommunication from the guys who made the parts catalog.
Last edited by chittychittybangbang; 03-11-2012 at 11:56 PM. Reason: balance shaft correction.
I'm pretty sure that the oil pump shaft mm refers to length not width. I believe they are interchangeable between balance shaft modules so the difference can't be the width or diameter of the oil pump shaft.
The oil pumps are different so it's possible there was a change in oil pressure. Not sure.