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Re: B210/120Y Dedicated thread

Subject: Re: B210/120Y Dedicated thread
by ddgonzal on 2017/12/15 6:19:49

yes a chassis dyno is called a rolling road

To get an old A12 up to it's potential it's important to have:
* Good spark (correctly set dwell/gap)
* Correct timing (34 degrees BTDC)
* Gearing to match top speed with max power RPM (6000 rpm)

More information: stock Datsun 1200 sedan/coupe top speed was 145 to 150kph, confirmed by magazine tests. Not bad for 69 flywheel HP (~40 rear wheel HP)

A chassis/wheel dyno can be loaded to simulate wind resistance which is the limiting top-speed factor for the Datsun 1200. At 150 kph, it takes every bit of HP the stock A12 outputs to just barely push the car through the wind. That means a stock A12 must be outputting top HP -- which occurs at 6,000 RPM. Hence small tires or steep gearing are needed. Five speeds won't help with top speed. VB110 has 10kph lower top speed partially due to less aerodynamics and partially due to over-steep gearing (hitting max HP RPM too soon and then the wagon can't go faster because engine HP is going down as you rev past 6000 RPM)

Wind resistance is squared with speed e.g. There is 4 times the aerodynamic drag when you go 2x the speed

Tuning your car to best feel will not make the most HP, if the feel at low speeds is what is aimed for. For example overadvancing the timing can pick up some acceleration but it will slow down when revved high enough. With careful recurving of the distributor you can get both, but even without that a stock distributor can be used to go 140/150 kph