r_wiggum01

i know the topic of of catch cans has been kind of beaten to death, but i'm curious about a different source of vacuum from the can. most people hook up to the pre-turbo intake or the exhaust as a source of vacuum to open the pcv, but i'm wondering if maybe i could actually hook up to the upper charge pipe and use a slash cut tube or an L-shaped fitting. theoretically, that should draw air out from the catch can as the boost pressure flows past it, creating a vacuum source. is there something i'm overlooking? if it works, i kind of wonder why no one seems to be using it, as it would keep whatever oil vapors and crap that makes it past the catch can out of the turbo, and return them to the intake manifold as it would on a n/a setup.

on a semi-related question, w/ a naturally aspirated setup could intake piping that is too small for the engine(old d-series aem short ram on new b18b1) create extra vacuum? would it be enough to hold the pcv open longer and suck out blow-by? i'm losing coolant, but i've had leakdown and compression tests and can't find any leaks or headgasket problems. honda tried to tell me that my intake caused extra vacuum, opening the pcv and sucking oil and coolant blow-by out. i thought this sounded like crap, as i doubt a filter and a piece of pipe could do this, and as far as i know there shouldn't be coolant in the crankcase anyway. ideas?

p.s. - sorry for the long first post. and i have tried searching but this particular question hasn't come up, so please don't flame me.

beepy

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote &raquo;</TD></TR><TR><TD CLASS="quote">but i'm wondering if maybe i could actually hook up to the upper charge pipe and use a slash cut tube or an L-shaped fitting. theoretically, that should draw air out from the catch can as the boost pressure flows past it, creating a vacuum source.</TD></TR></TABLE>

This would only work if the catch can and the charge pipe were at the same pressure. The Bernoulli effect would then cause a slight pressure drop at a reduction in diameter in the charge pipe. However since your catch can is atmospheric and your charge pipes are higher, you would just pressurize your catch can.

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote &raquo;</TD></TR><TR><TD CLASS="quote">w/ a naturally aspirated setup could intake piping that is too small for the engine(old d-series aem short ram on new b18b1) create extra vacuum?</TD></TR></TABLE>

Vacuum is for the most part only created by the throttle. However because of the constriction in piping, a slight reduction in pressure is created along its length. Theoretically the Honda mechs could be right, but it is highly doubtful because the amount of vaccum generated would be on the order of 10 millibar.

r_wiggum01

good info., thanks beepy. now does anyone have any idea where the hell my coolant might be going? like i said, it's not the headgasket and i can't find any external leaks anywhere.