I am adding a spring loaded check valve between the turbo outlet / carb inlet and the blow-off valve (BOV). In series with the BOV, BOV is last in line. I did some testing last year on the street and under most cruise conditions (no boost, vac in manifold) the turbos were not supplying enough air to the carb. Some of the air was being sucked in or short cutted through the BOV (which is open during cruise) to the carb. The check valve will be normally closed during cruise and blow open under boost, against the BOV, which will be closed untill engine vaccum opens it. Once the pressure is gone in the inlet plumbing, the check valve will close again (boost blows it open). Anyone else see this problem of sucking in unfilter air?? I am building a new "big" engine and I want to protect it as much as possible. Any comments?? Thanks, Dave two

 

I don't quite understand what your describing. Could you do a real simple diagram in paint or something?

 

jaredsamurai, I would be happy to but i do not know how to draw on my computer. Just picture a tube coming out of a turbo with a tee in it, one end of the tee going to a carb, the other end going to a check valve, than a BOV. Maybe I could post a picture. Thanks, Dave two

 

Maybe what I don't understand is why your BOV isn't hooked to the intake manifold. BOV's don't function at all with out vacuum. When you say hooked to the "carb inlet" do you mean the carb hat or the nipple under the carb?

 

jaredsamurai, BOVs are hooked, connected, welded) to the carb inlet tube, sometimes welded to the carb hat (but are controlled by the intake manifold vacuum) and are used to relieve pressure in the inlet pipe and are held open with engine vacuum. I am not touching any vacuum controls. I am only trying to keep the outside, unfiltered air from going into the carb. I only want the air from the turbos to feed the carb. The check valve keeps the air from entering the carb but "lets the pressure out at any time" (but the BOV vacuum control stops this from happening until it is necessary because the BOV & Ck Valve are in series). Hope this helps, thanks, Dave two

 

Ohhhhhhhhh ok. I though this whole time you wanted to mess with the signal to the BOV, your talking about the actual discharge air. Your Idea should work if you can find a check valve that is large enuff to flow as much as your BOV. Do you have one in mind?

There are other options to stop unfiltered air from getting in.

1) Use a BOV that you can put an air filter on the discharge. It won't be as pretty and it might muffle the BOV noise that everyone loves so much (personally I don't care if I hear it)

2) Get a recirculation valve that runs the air back to the inlet of the turbo down stream of the filter

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I don't know what your combo is but maybe one or two of these. Put little breather filters on em or recirc them

http://www.forgemotorsport.co.uk/content.asp?inc=product&cat=0006&product=FMCL007P

 

Bosch also makes cheaper plastic ones if you don't need a flashy metal one

 

jaredsamurai, now we are on the same idea! I have a WGS Blow Off Valve. A filter will not fit it without making it a big deal. Recirculating it could work also but tubing, fittings would be more work / cost than a check valve. Check Valve = ACE Hardware, 2" PVC spring loaded water valve = $8.00, paint to match. How did you post that hand made picture. Draw it, than photo, than post? Thanks, Dave two

 

just go into microsoft paint. Every computer since the early 90's has it. Draw the pic, save it, then when replying to a post, hit additional options and add the pic.

 

did you mean JGS?

 

jaredsamurai, thanks for the drawing information. Yes, I have a JGS valve. Dave two.

 

Most of the time there is positive air when the bov is open but if your concerned you can use a prefilter sock over the bov.

 

JGSturbo. Correct, I also think there is flow (positive) out of the BOV. My Prochargers always blew air out the BOV. But in a few cases I have seen and mine, large turbos do not spool enough air at cruise speeds on the street. I have no hood, my turbos and plumbing are 4" above the hood line, real easy the see what was happening when I was driving. I put one of my foot socks over the BOV and watched it being sucked in at low / no boost speeds. After a few weeks the sock was getting dirty around the BOV holes, proving some air was taking a short cut. A sock or filter would work but I want all the air to come through the air filter.
If anyone is interested I built a pressure relief valve out of the same water valve (check valve) to protect my engine from over boost (set @ 12PSI). Water valve, waste gate spring, threaded reducer, 2 plastic furniture skids, paint, drill a few holes ($20). Two years and still working with compound turbos blowing agains it. Thanks, Dave two

 

If it's opening under high vacuum/no boost conditions, you just need a stiffer spring. Right? I'm still a little confused if you want it open when it's not supposed to be (aka 'bypass valve'), or if you're trying to keep it closed.

High vacuum = should be closed. High boost = should be closed. High vacuum + high boost = should be open.

 

I was gonna ask if you had a little stiffer spring. As long as it still opens under the vacuum spike when the throttle snaps shut you should be good. Spring it just a hair tighter than your vacuum at light cruise

 

cat herder, jaredsamurai, My BOV in non adjustable. My old engine cruised at 12" HG. My new engine is still being put together, vac unknown. Your spring change may get it closer to what I want but a chech valve is sooooooo much easer. To cat herder, I am not trying to modify or change anything about the BOV. It does what it is designed for. My engine just sucks dirt through the BOV because the turbos are large, not spooling at low speed cruise so they pose a restriction to get air to the carb, so it short cuts through the BOV. My problem only happens when using oversized turbos (high horse power). It is different at the drag strip. Thanks, Dave two

 

I assume you have a JGS500/560/600, and not the little one with the recirc tube on the side, or else this thread wouldn't exist 'cause you would have just clamped a filter to the tube. Your BOV is adjustable, by changing springs. The man who designed and built it already posted in this thread, talk to him and he'll get you sorted if you don't have the spring(s) you need.

 

With that check valve the BOV should NEVER open... even when it needs to open.
Should have been 2 extra springs in the package.

 

JGSturbo, did I miss something? The check valve is not in the vacuum control line. I do nothing to the Bov control line. The ck valve is in series with the pressure / no pressure, large end of the valve. The ck valve inside diameter is 2".
Example?
Normal cruise, Bov open engine no boost ck valve spring loaded closed, no random air in ck valve closed prevents air going backwards to the engine through holes in Bov
Under boost, Bov closed engine boost ck valve blown open, but no air out ck valve is open, but no air can get past the Bov, Bov still controls outer air flow
Thanks, Dave two