To make a long story short, my dispstick blew out last night.

It is a c5 vette with all stock internals running about 9.5 psi with an ATI d1 blower. The car was finally running good and the AF was 11.5 and there was no KR at all. I’ve been relying on water/alky injection to protect my motor from detonation and it has been working great.

I'm assuming I may have a cracked piston/ringland or something of that nature, but it raised allot of questions in my mind about blow by. I have a check valve right after the normal pcv valve to keep the pressure from going out the intake and into the valve cover, so I don't think the pressure came from that direction. I would think this means that it has to have been caused by air coming around the pistons.

Here are my questions.

1. How much blowby is considered normal on a boosted car?

2. Is more blowby expected on a boosted motor compared to a NA motor?

3. Do you need a breather in the PCV on a boosted car? It seems that pressure from blowby has somewhere to go on a NA motor (the PCV line going into the intake manifold), but has no escape on a boosted motor when under boost.

I have a check valve in my PCV line to keep the boost from pressurizing the valve cover, but I'm assuming this provides no breathing for pressure from blowby when the boost is on.

I’m still a little confused about exactly how the PCV is suppose to work. I have one line that goes to the intake manifold (it has a check valve and the normal PCV valve inline) and one that goes to the blower inlet area. The one going to the inlet is referred to as the PCV inlet. Can someone explain how these two different lines are routed down in to the crankcase? I’m having trouble conceptualizing how one is restricted to pulling air into the crankcase. I would think that the pressre would have found it's way out into the line that goes to my blower inlet (where there should have been some vacuum)

 

Well I pretty much figured out when blowby is too much, I think my car detetonated due to oil being put into the intake, not sure if it was a bad PCV or a cracked ringland....I ripped out the PCV system and installed two breather valves on my stock shortblocked setup..

The things were smoke stacks and dripped oil....burned all over the headers, I decided that it was enough, and with the motor being hurt as it was, there was no point to try and put boost through it..

My new motor I have the same breathers on, and it doesn't smoke at all....

 

Sounds like it's time for a compression test.

 

This is very interesting to me, as it's something I've never thought about (being new into looking at forced induction)

On an N/A car the vacuum of the engine sucks excess blowby from the crankcase and valve covers.

In a FI car, there is no vacuum. In fact you'd think that the pcv system would flow backwards (unless it's a one way valve which I don't know about) and create a positive pressure in the crankcase, regardless of the amount of blowby. Combine that with the blowby of the engine and all this pressure only has a few ways to escape. One being the dipstick.

I think breathers is going to be your best bet to help this problem...ditching the pcv system.

 

dude, get a crank case evap kit hooked up, you know what that is right?

 

I know what it is, but don’t much about them? I've never heard street cars needing it.


Anyway, here is what I rigged up tonight and plan to test tomorrow.

I put a T in the PCV line before my check valve. The T connects to a solenoid that only opens when 1+ psi is detected in the manifold. The line out of the solenoid goes to a well vented catch can in the batt box.

This way I get a good vacuum from the PCV in normal operation and have a good vent path for when the boost is on.

I'm going to put it on the dyno tomorrow and see what happens. I'm keeping my fingers crossed.

 

On My car.. I tied all PCV Sources into a Single Hose and dump that into a Catch Can. For VACUUM Source on the other side of the Catch Can I'm using the Tap on the back side of the Supercharger Intake Duct. As you know both Vortech and ATI have this little hole.. It's supposed to be connected to the Passenger side Valve Cover as a Fresh Air Supply. Since that side of the Blower will never see BOOST it makes a great Vacuum Replacement. Just Cap Off your Intake PCV Port and you'll never have to worry about one way Check Valves, etc.

 

ive tried alot of stuff and i think this will end up being the only solution.
the crank case needs a vacuum to help seal the rings as well.

i did a compression test on my car, had good equal compression on all eight cylinder, but i still was/am getting bad blowby crank case pressure. i am going to pull the motor next spring and re do the rings just incase
and get me one of those crank case evacts

 

my friend just ended up needing one for his car also, its just a reg 350 though, if your running 11's consider your car a race car, in fact if its a street car also it'll take even more abuse, the c.c.e kit takes about 1/2 to get going but taking out the headers and drilling a hole for the pipe takes the longest amount of time, should still be able to do it in a day in the driveway, if you've got a lift......... jizzzz

 

Can you post a link to the kit mentioned above?

 

I dont have a link, go to napa and ask for a crankcase evap. kit, look on the box, it has the directions!.............ok, I just called napa, the technical name is crankcase evacuation system, its $41.90 over here, might be cheaper over there!

 

The only thing with the crankcase evap kit is that it will screw with the O2 readings if its before the O2 sensors. The sensors should see extra air, reading lean, and will throw fuel in to compensate when none is actually needed.

If there placed after the O2 sensors, I dont know how effective they will be... may be no difference.

 

no, they go behind the o2's

 

I'm far from an FI expert, but one thing strikes me as wrong:

Since the stock place the engine get's it's "fresh" air (the pasenger side valve cover in the front which connects to the throttle body) now has air being forced into from a supercharger, there is no way your PCV sysetm is going to be able to pull vacuum.
As a cheap test, just try capping off that hose, and running a breather, so no air is being forced INTO the valve covers. See how that works. (And make sure you use a good cap on the throttle body pipe so it doesn'r come flying off! Good luck!

Tommy

 

We all have the nipple in front of the throttle plate capped. The one on the manifold also needs a check valve for boost conditions since the PCV valve can't hold boost.

 

for the evac kits i was thinking of a belt driven or electric pump.

not sure how the header method will work with a street car with full exhaust.

 

I'm working on an Electric solution for my NA car... If it works, I'll post it up.

Tommy

 

I have an electric evac setup for sale, Caddy 4-6-8 pump complete with tank.

 

ANy more info on the pump John, pics? price?

and have you sent my plugs yet?