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Posted by Eiron (more from Eiron) on Wed, 27 Aug 2003 09:47:33 Share Post by Email
In Reply to: Hey Eiron, master of BPV's..., Jeff in ATL, Wed, 27 Aug 2003 05:32:24
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Hey Jeff,

Rob has some good advice, especially regarding the grease. I think Forge's only caution is to stay away from "metallic" greases. I use a syn grease similar to Rob's Super-Lube, but I don't recall the name right now. It's a hi-temp grease, so it resists migration (due to heat separation) a little bit better. Obviously, you can't go wrong with M1 grease.

If you're changing your oil every 3k miles, then I'd clean the valve during the first two oil changes & make a note of how it's holding up for grease retention & aluminum oxide accumulation (the dark grey "dirt" in the grease). I'd do a simple wipe-down of the valve body & piston, without removing the O-rings. If it looks OK, you can extend out to 6k mile cleanings & make another assessment. Basically, you don't want too much of the grease to migrate off of the O-rings. You may find out you can easily go 9k-12k miles between cleanings, but it's always nice to verify it with conservatively-spaced checks up front. I'd pull the O-rings out once a year & clean out the grooves.

On mine, I also noticed some wear on the piston-nose/bottom-port interface (the chamfered "seat" that the piston seals against), so I'd check that area for wear/dirt & wipe it down if necessary. Oh, & don't forget a thin layer of grease around the top rim of the valve body, before you screw the top back on. The newer valves have a third O-ring seal there which needs lube, but older valves without the O-ring can benefit from the extra leak-resistant "grease seal" too.

Valve orientation is subject to several aspects of operation. Bosch said that valve orientation is dictated by each car manufacturer's design goals, but Saab wouldn't answer my questions about it. Forge says that pressure to the bottom port makes their valves operate more efficiently, since that puts pressure in-line with the spring's travel. (Pressure coming in from the side flows across the piston's nose, potentially "disrupting" the piston's travel.) The valves actually start to leak boost pressure sooner with pressure coming into the side port, & I'm assuming Saab chose this orientation on purpose (maybe for turbo protection reasons?).

So for me, it's a decision based on which spring pressure I've chosen for the valve & whether or not I've increased operating boost pressures. From my tests, I know that pressure into the side port with the light (green) spring leaks sooner than the stock Bosch valve, while the heavy (blue) spring starts leaking at about the same point as the stock Bosch. If I'm using the light spring with normal boost, then I know I can safely run the valve with pressure to bottom port. This gives me the benefit of lighter spring force (better turbo protection), no boost leaks, & Forge's preferred spring/boost match. But if I'm using the heavy spring with normal boost, I'll run pressure to side. And if I'm running the heavy spring with increased boost, I'll run pressure to bottom.

Let me know if I missed anything, & feel free to email me anytime.

-Greg

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