Alrighty... made my slash-cut exhaust ventilation setup and my slash-cut tube is creating pressure instead of vacuum most of the time. I wondered why my check valve was going nuts all the time when I was testing the setup, and this explains it. At idle is is just straight pressure, as I rev it up it turns slowly to a LITTLE vacuum... then when I let of it seems to go back and forth.

My tube is cut at 45 degrees and the opening is away from the flow as it should be. Could this be because my exhaust hasn't been upgraded behind the cat yet? Perhaps alot of back pressure from restriction in the exhaust? I've got it parked until I figure this out... worst case I could drive it with an opening in the can, but that is pretty nasty for the environment.

One more question... even with the extra hole that I made in addition to the factory valve cover vent hole I have ALOT of pressure in my valve cover. I took the oil cap off at idle and air was RUSHING out of there pretty intensely... unlike anything I've seen when taking an oil cap off before. Even if I just let both holes run open into the engine bay it is still like this under the cover. Does this mean I need MORE ventilation or is this sort of thing just going to happen?

As an FYI my car started smoking when it was turbocharged... so perhaps my rings are messed up? Would that cause the pressure? The smoking calmed down quite a bit when I added my extra venitilation but it still smokes when I rev high and then let off... it is delayed until the revs come back down, which seems a little weird.

 

you did put the slash cut after the cat right ? if not, you have a problem that needs to be addressed.


Modified by dturbocivic at 8:30 AM 1/17/2007

 

As of right now there is no cat on the car. It's got one of those e-bay resonators on there in place of the cat with the slash cut tube in the down-pipe before the resonator -- it's just a straight through perforated tube. Once I re-do the exhaust and have a cat in place it will be going behid the cat.

 

is your engine internally stock?

how much boost are you laying on that sucker? how long has it been running?


in order for a valvecover vent setup to work properly, the hoses that you attach onto it, neeed to be of nominal diameter(1inch) at least 2 of them......

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by sundownz &raquo;</TD></TR><TR><TD CLASS="quote"> Could this be because my exhaust hasn't been upgraded behind the cat yet? </TD></TR></TABLE>

I'd say most likely that's the reason. Exhaust gas will find the path of least resistance, remember that there's not just linear flow, there's expansion as well.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by dturbocivic &raquo;</TD></TR><TR><TD CLASS="quote">is your engine internally stock?

how much boost are you laying on that sucker? how long has it been running?

in order for a valvecover vent setup to work properly, the hoses that you attach onto it, neeed to be of nominal diameter(1inch) at least 2 of them......</TD></TR></TABLE>

It is internally stock and on the Dyno it hit 8 PSI before the gate opened. I've probably put ~2000 miles on it with the turbo, none of it over 5k RPM due to the injector limits.

Sounds like I need more ventilation... I've got one 3/4" ID hose and the factory valve cover breather hose at the moment. I'll look into adding another one and another fitting on my can for it ASAP.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Mr. Helsinki &raquo;</TD></TR><TR><TD CLASS="quote">I'd say most likely that's the reason. Exhaust gas will find the path of least resistance, remember that there's not just linear flow, there's expansion as well.</TD></TR></TABLE>

I am getting 2.5" all the way back on it very soon -- down-pipe all the way to the rear with a high flow 2.5" cat. So that should take care of my vacuum issue then, correct?

I'm thinking this motor may be on it's last leg anyway. It had about 115k before the turbo and it is the stock motor in a 1994 vehicle, so age probably has taken it's toll. It is basically my "low risk" learning build since the D15B7 in it is a really cheap motor that I have no money into other than the turbo and other parts that can be transferred.

I'm looking into picking up a rebuilt D16 bottom end and a rebuilt non-VTEC SOHC head as well... having those done with forged rods, vitara pistons, king bearings, ARP bolts and studs, and upgraded valve springs. I'm hoping the D15 will hold together for long enough to build that setup... fortunatly I have another car to drive if it breaks down completely!