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Turbo XS Bov proper adjudtment


importwarrior
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i need to adjust the Turbo XS Bov. it seems to bee way too tight.

 

i know the BOV has washers and spring tension but whats the

proper way to adjust it?

 

car is running 20 PSI and it does not seem to want to open i get

some turkey gobble as if it was not there like stock turbo'd car.

 

i opened the BOV and noticed 4 washers in there. how can i

determine the proper amount of washers to use?

 

Thanks for the help.

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You build a boost leak tester and check the BOV with the vacuum line off. Add washers until the valve opens a few PSI higher than your boost setting. Also those BOVs respond better to a larger vacuum line. 1/4" line works great and don't hook it to one of the 3 ports on the TB. Use the port below the TB or the capped off port on the #4 runner. When mine was TBI I tapped the port on the #4 runner to 1/8" NPT and put a 1/4" hose barb there just for the BOV. The result was the BOV was more responsive. You can tap it on the car without shavings getting into the intake by hooking an air compressor to the PCV port. By pressurizing the intake any shavings from tapping are pushed out of the hole by the air pressure. Wear safety glasses. You can just buy an adapter for that port but,.... it's 1/16" NPT so the adapter will be more expensive and the hole will be smaller. Kinda like taping a small straw to a bigger straw. It doesn't have the same affect as just using the bigger straw.
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  • 5 weeks later...
I would definitely boost leak it, I've only seen a handful that actually sealed. Not sure on the reasoning behind testing without the vac line tho? The valve works by pressure differential, the spring is only there to hold it closed at idle theoretically on boost the valve should not move even if there were no spring, it sees boost on both sides. The vacuum it sees when you let off the throttle and the boost still in the charge pipe are what open it. That's why BOV springs are rated in vacuum not pressure. it's there to hold the valve closed at idle and any condition not in boost once your in boost the spring is a non issue. When you shim those valves it affects how much the piston can actually open, affecting the flow of the valve, not good. I would take out all the washers and boost check the system as it would be running on the car, closest thing to real world operation. If it doesn't piss out of the piston assembly under boost leak(leak being a faulty and leaking valve) mark the valve with a sharpie with the car off in its closed position, start up the car and see if it stays closed, if it does and it did not bleed pressure with boost to both sides your golden, if it doesn't the right way to adjust is with a stiffer spring. Personally I've seen too many turbo xs valves that leak to have any confidence they seal up unless it's brand new out of the box. They are not precision made and it is a part that needs to be very precise to work properly. The bronze or brass piston they use usually scores due to loose tolerances and movement of the valve. That or the o ring is blown out and people try to compensate for it by jamming shims in there to get it to seal. If the valve blows when your on the throttle under boost it's because it's leaking from the manifold side either through the cap or the piston creating a pressure differential and allowing it to open. Edited by boostintsi
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Thanks for the information. lots of good stuff in there.

 

Well i took out 2 washers so there was only 2 in there.

still have turbo stall. as in the BOV not opening fast enough.

I then took them all out and left just the spring in there. i still

have turbo stall. most of the time it opens fine but under a hard

acceleration when shifting fast the BOV still just does not open

fast enough. i am thinking i need a different type of BOV.

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I've run a tial on every turbo car I've had and that is what we recommend to every customer in need of a valve. They are pricey but they LAST, will be the last bov you ever buy for the vehicle. Very good quality made in the USA. They also have good customer support and rebuild kits are cheap and readily available as are the different springs.

 

What turbo are you running? It could be that the reference hose is too small as ucw458 had mentioned or you have surpassed the flow of the valve, or it is leaking. The bigger the reference the better they work. My tial recommends a 6mm reference I believe, that's a big vacuum line. That valve should snap open quickly did you boost leak the car? A leaky bov on reference side will absolutely cause poor operation sluggish response, as well as the piston not opening fully. Not to mention a boost leak anywhere is bad for performance and bad for turbo and engine life. over spinning wreaks havoc in shafts and bushings/bearings as well as intake temps. I boost leak my car every time i change the oil for peace of mind and also to catch little problems before they turn into big ones. Its a normal part of turbo vehicle maintenance. More often then not when I boost leak a customer car there's at least one or two little leaks be it from a charge pipe coupler or vac line fitting, throttle shafts, sensor bugs anything that sees pressure. If it hasn't been leak checked I'd highly recommend not only for testing the bov but also overall system performance.

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  • 3 weeks later...
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