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Discussion Starter #1
i have a turboXS type H adjustable BOV, which you can adjust the spring tension by inserting 'pack washers' to shorten spring length and hence increase the force required to open the valve. i have read the that the speedparts stg2 is capable of 17-19psi peak boost, and the valve is rated for 10-30psi. so my question is more a search for clarification...perhaps someone can shed some light on this..i have heard two different thoughts on this:

1-leave the BOV in a state where it is adjusted ONLY to the point that it is closed on idle

2-adjust the BOV so it will not leak pressure at high psi

i think the thought behind (1) is that it will not take much pressure to open and prevent any reverse shock to the turbo if pressure gets 'caught' due to the spring tension, and the thought behind (2) is that you will be able to hold more pressure without it leaking off through the weak spring tension?....can someone clear this up once and for all?

cheers/eric
96 900SET
 

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The spring does not have to resist full boost pressure because both sides of the diaphragm or piston (depending on the valve construction) will generally see almost the same pressure at full throttle (when you will get maximum boost). This means the pressure difference (which is what will work against the spring) is quite small. When you lift off, however, the throttle plate closes and the manifold is under vacuum while the inlet is still under pressure. This causes a very large pressure difference which opens the valve against spring pressure.

Basically, you want enough pressure to keep the valve closed at idle and also at part-throttle as the turbo spools up. I think the idle condition generates the greater pressure difference of the two conditions so you probably want answer number 1.

Best to check, if you can, that it isn't opening up at part-throttle and slowing turbo spool-up.
 

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Sorry Eric, the link you sent does not seem to work.
 

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Discussion Starter #8
great article eric..still a little confused about stacking the pack washers in my turboxs...maybe i should just get a pump setup and see how many washers it takes for 17-20psi....i have one washer in now...in the test, he was using 4? seems like he may have been asking for a little shock with that setup..i'll play around with it...maybe try 3-4 washers and see what happens..

/eric
 

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Originally posted by ericl:
[qb]great article eric..still a little confused about stacking the pack washers in my turboxs...maybe i should just get a pump setup and see how many washers it takes for 17-20psi....i have one washer in now...in the test, he was using 4? seems like he may have been asking for a little shock with that setup..i'll play around with it...maybe try 3-4 washers and see what happens..

/eric [/qb][/b]
The washer adjustment is mainly to ensure proper idling of the car and that it doesn't stall if you completely let off the gas and let it fall to idle.

With the TurboXS, atleast with my MR2, basically as long as the car idles fine, doesn't stall if you say, let off at 5500k and just let it fall to idle, and it releases at high cruising speeds then you are fine. I found that I acutally had to REMOVE washers from my TurboXS bov in my MR2 because it wouldn't release at cruising speeds with minor adjustments in throttle position, causing the car to buck, and it would stall after I let off sometimes. Removed a few washers, still holds boost fine and doesn't stall now..
 

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Discussion Starter #10
thanks turborush...i actually have an update on this...i spoke with the folks at turboxs and the washers only provide 1/3 psi increase in tension, and they are only for keeping the valve closed at idle primarily...they said that some folks will use to hold boost better between shifts?, but they really weren't intended necessarily to do this...but the customization sets them apart..i did stack a few in and got the 'bucking' that you describe..i didn't like it and took them back out...i have one washer in now...and everything seems fine...

/eric
 

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Originally posted by ericl:
[qb]thanks turborush...i actually have an update on this...i spoke with the folks at turboxs and the washers only provide 1/3 psi increase in tension, and they are only for keeping the valve closed at idle primarily...they said that some folks will use to hold boost better between shifts?, but they really weren't intended necessarily to do this...but the customization sets them apart..i did stack a few in and got the 'bucking' that you describe..i didn't like it and took them back out...i have one washer in now...and everything seems fine...

/eric [/qb][/b]
Yeah, you defiently don't want that bucking, thats the air slamming back into the compressor side of the turbo.. BAD..
 
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