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Bob
Aug 31, 2016 - 7:19AM
BMW 3/20 Engine's Origins

Was wondering if somebody can clear up whether the 788cc OHV engine in the BMW 3/20 was an all-new engine design or indeed based on the Austin Seven 747cc Side-Valve engine (albeit now featuring OHV, water-pump, plain-bearings crankshaft and increased 80mm stroke)?

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Aug 31st, 2016 - 7:19 AM
Reckless Rat
Aug 31, 2016 - 8:58PM
Re: BMW 3/20 Engine's Origins

I was talking to a German guy a bit back at a car show in Poussan. He's the owner of a 1928 Dixi which was made under licence from Austin. Even at that early stage a lot of the Dixi didn't follow exactly the design of the Austin Seven. Many things were different apart from the engine pattern being a mirror image. All fastenings were metric, all electrics were Bosch. However Dixi was not owned by BMW at that particular time. When they took over the company in late 1928 and it changed from Fahrzeugfabrik Eisenach to become Bayerisch Motorenwerke (BMW)- the German guy told me that the new company didn't like a lot of the Dixi engineering and set out to improve things, so later cars were very different to the 3/15 DA1.

I guess the development of their own engine for the completely non Austin based 3/20 was the start.

Location: Gard, France 30960

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Aug 31st, 2016 - 8:58 PM
b
Bob
Sep 1, 2016 - 12:07PM
Re: BMW 3/20 Engine's Origins

Reckless Rat
I was talking to a German guy a bit back at a car show in Poussan. He's the owner of a 1928 Dixi which was made under licence from Austin. Even at that early stage a lot of the Dixi didn't follow exactly the design of the Austin Seven. Many things were different apart from the engine pattern being a mirror image. All fastenings were metric, all electrics were Bosch. However Dixi was not owned by BMW at that particular time. When they took over the company in late 1928 and it changed from Fahrzeugfabrik Eisenach to become Bayerisch Motorenwerke (BMW)- the German guy told me that the new company didn't like a lot of the Dixi engineering and set out to improve things, so later cars were very different to the 3/15 DA1.

I guess the development of their own engine for the completely non Austin based 3/20 was the start.


Though understand Wikipedia is hardly reliable, on the BMW 3/20 page it says:

"The engine used in the 3/20 was based on the Austin Seven engine used in the 3/15, but its crankshaft ran in plain bearings instead of roller bearings and had an 80 mm (3.1 in) stroke, generating a displacement of 788 cc (48.1 cu in). The new engine design also had a water pump and an overhead valve cylinder head."

While citing its sources for the engine being Austin-based in Jan P. Norbye's BMW - Bavaria's Driving Machines and Andrew Noakes's The Ultimate History of BMW books.

Perhaps it is possible some relation between the Austin Seven and BMW 3/20 engines does exist, similar to Nissan producing new and improved 4/6-cylinder engines derived from the BMC B-Series?

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Sep 1st, 2016 - 12:07 PM
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