
「Although B58’s closed deck is structurally strong, it also has shortcomings. For example it carries a higher manufacturing cost; Also the coolant flow is more restricted, which prompts BMW to use a dedicated heat management module on the B58 engine.
On the other hand, this does not mean open deck design is bad. Open deck block is lighter and has better cooling effect, therefore it is more suitable to applications that does not call for high cylinder pressure.
The N54/55 uses cast iron cylinder sleeve, but B58 is different: it uses one latest technology called “
Electric Arc Wire Spraying”. This is a type of the ferrum plasma spray method, which creates a thin layer (0.3 mm thick) of iron on the cylinder wall surface and thus eliminates the need for using the cylinder sleeves. The ultimate goal is to save weight. For your reference: plasma spray is an exotic technique previously (
for example GT-R, LFA etc.), however nowadays its cost is lowered so significantly that even Ford uses it in the EcoBoost engine family.
You may also find most of the BMW inline six engines are all undersquare, and this is exactly the same on B58 too. The B58 engine has a bore of 82 mm and stroke of 94.6 mm. The purpose of such geometry design is not for lower-end torque, but with consideration in packaging. Had BMW used a shorter stroke, in order to maintain the same displacement, its cylinder bore need to be much larger. Since here 6 cylinders are placed inline together, this will lead to a excessively long cylinder block, and thus hard to arrange spaces inside the engine compartment, or requires the vehicle to has a longer nose (which is unnecessary for many car models). What’s more, a longer crankshaft (caused by long block) is weaker too.
」
・GTRやLFAのエンジンもシリンダースリーブが無く、プラズマ・スプレー法による鉄被膜溶着だそうです。日本の技術ですよね。(エキゾチック・テクニック...と表現されています。)
・B58が短ボア、長ストロークなのは低回転時のトルクアップの為ではなく、6気筒エンジンの全長を短くするため。
*同じプラットフォームで縦置きの6気筒モデルと4気筒モデルをラインアップする為には6気筒を短くつくる必要があるのでしょう。
・日本の車関係のwebsiteに、このような基礎的な「自動車工学」的な記事がほとんど見られないのは残念です。
・私がマニアックなだけ?
*記事は 'youwheel.com' より転載
*同じ記事が2つアップロードされていましたので、1つ削除しました。
「いいね」して下さったのにすみません。m(_ _)m
Posted at 2019/10/26 23:48:33 | |
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