Suction at tail pipe - PeachParts Mercedes-Benz Forum

leathermang · #19 04-29-2009, 07:04 PM

CarlG, What do you mean " sorry "... I am not some black sheep you need to be ashamed of agreeing with....
LOL

I do think we should define some parameters when trying to discuss this whole thing...
Lets try to distinguish between a ' lack of power stroke' on a cylinder.... as could happen with a lack of fuel to a single cylinder...
and suction which would mean some way that the piston going down in the bore pulls air from the wrong place... the exhaust pipe.. as compared to the intake.
It would be easy to confuse them when down there at the exhaust pipe smelling those wonderful fumes...
Lets define the test equipment which might distinguish between those two types of symptoms....
If a playing card were held near the tip of the exhaust pipe the gas would push it away from the tip... and if a pulse was missed it would snap towards the pipe end....
Lets assume the card has its fulcrum at the top and only gravity to bring it back to vertical if gas pressure is reduced... I am using the lightweight card for an example because a heavier object ,having been pushed off vertical, would then have stored kinetic energy sufficient to cause it to drop back further than vertical... thus giving the false impression that it was pulled back towards the pipe due to suction... as compared to just a missed positive pulse of exhaust gas.
This is also the case if this item is hand held... the reaction just like someone let go of a rope in a tug of war.
So the ideal test instrument is very light, placed very close to the end of the exhaust pipe , nonflammable (LOL), hinged close to the top of the horizontal extension of the top of the exhaust pipe and hopefully dampened slightly in its reaction to the lack of backward pressure....
This would distinguish between a lack of positive pressure out of the exhaust...and actual suction caused by some deficiency in the one way function usually provided by the valve action in an engine.