If the engine is warm and you nail it on the hwy and its not open you are going to get a heck of alot of pressure built up instantly. On a gasser or non turbo diesel it could be slow as you stated. On a turbo it will be hella quick.

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1995 E420 Schwarz
1995 E300 Weiss
#1987 300D Sturmmachine
#1991 300D Nearly Perfect
#1994 E320 Cabriolet
#1995 E320 Touring
#1985 300D Sedan
OBK #42