Though The Air Bypass Valve (ABV) and Charge Relief Valve (CRV) have similar functions, are the the exact same part number? While reviewing the turbo troubleshooter at http://www.autosportracetech.com/RX-...leshooting.htm I noticed the the test conditions for these valves are not the same. So, I checked my ABV and CRV and they have the same part number: "N390 084900-0580 CRV".

Was the previous owner a bonehead? Are these supposed to be the same part?

 

The ABV has N3A1 084900-065 0 written on it. They are not the same.

 

They do have different part numbers and different labels on it, but functionally they seem to be the same. I think the major difference is the label for techs to know which one is which.

Might be worth getting a good used one of the one you don't have just so things are right (small things like this bug the heck out of me ). But, I seriously doubt any boost problems you might have are related to this.

Has anyone actually had a stock ABV/CBV actually *fail*? From what I've seen, they're pretty durable and reliable.

Dale

 

It appears that I have two CRVs. Would someone please post their CRV model number for comparison.

Dale,
I'm glad to hear that these are functionally the same. Do you know why their test conditions are slightly different? Is it just an oversight? From the turbo troubleshooting page:

ABV:
With a vacuum tester apply 3.9-6.7 inHg of vacuum to port (A), verify air will flow from port (B) to port (C). At 9.2 inHg of vacuum to port (A) the valve will be fully open.

CRV
With a vacuum tester apply 6.5-9.3 inHg of vacuum to port (A), verify air will flow from port (B) to port (C).

 

By functionally, he means they will 'function' the same (i.e. releasing air) by exchanging them, but it's not ideal.

I believe I still have my stock BOV laying around if you need one.

 

The crv is a bit softer than the abv...it opens easier with vacuum applied.

 

When I bought my FD it had a nasty loud RFL bov on it. Not liking the ricer sound, I installed the stock BOV. Boost response was markedly worse. I couldn't believe it thinking I had screwed something up re-installing it, but all was OK. Reinstalled the loud ricer bov and worked better.

 

Hmm, that's interesting. I guess the only real difference is the spring pressure on the BOV. The CRV has a stiffer spring of the two - might be an upgrade if you're running enough boost to overcome the spring, but I haven't heard of anyone with that problem.

Dale

 

Yep. Since the aftermarket BOV's have stronger springs, you'll notice a little better boost response over the stock unit. Garfinkle on TN apparently does a modification to the stock BOV to replace the stock spring with a stronger one.

 

Both valves are supposed to be able to stay closed with 15 psi applied in the direction of flow with the control lines disconnected. A crude test to see if you have a problem is to have the discharge side of the bypass valve disconnected from the air filter box. Rev the engine wide open throttle, to more than 5k revs, but less than red line, and see if there is any discharge from the valve. Mine did, so I rigged up a simple test rig using a standard air line blower with a 1/4" end. I set the air line pressure using an old boost gauge and the applied the 15 psi to the valve, with a hose within a hose to make the seal. It blew at about 4 psi. I've subsequently got a good used one that passes both tests, but what pressure is the bypass valve supposed to stand with the control line connected and under pressure?

 

Witch valve goes where im having issues with mine and I mixed them up.

 

ABV=front....CRV=Rear

 

FYI, the part numbers have changed:

ABV ( air bypass valve ): N3A1-20-250
CRV ( charge relief valve ): N390-20-250

:-) neil

 

I think my crv might have failed...or is damaged anyway. I got my car smoke tested and it looks like there was quite a bit of smoke coming from the valve itself. I wonder if that could be causing the slight surge I get when my car idles?
Is that verified that those new numbers are the proper replacement parts?

ABV ( air bypass valve ): N3A1-20-250
CRV ( charge relief valve ): N390-20-250