Definitely a GOOD idea to look at this Blow Off Valve...

[tigerdog]

...a cheap knock-off dump valve from Ebay. Smaug already wears a TurboXS dump; it's loud and I want something I can duct into the intake. I could buy the TurboXS H34, for about $175 but that seem excessive considering I already have a perfectly good valve. If the photos are an indication, these appear to be of a different quality than most of the Ebay stuff, much of which can be traced to a single Chinese factory and look like crud. For $25, it might be worth a try. Anyone had experience with one like this?

[Mike_H]

Hi Tigerdog,

I don't think much of any of the cheap Chineese BOVs you see around .

You get what you pay for I think !

By the way you don't have to route the air back into the airfilter can .

I used a norgren quietair silencer and it makes no noticable sound at all.



Have a look at my old thread.

viewtopic.php?f=31&t=13780&p=182300#p182300

Mike.

[tigerdog]

I used a norgren quietair silencer and it makes no noticable sound at all.

I saw your thread before and was impressed with the clever solution. Unfortunately, the TurboXS model I currently have is vented around its entire circumfrence; there's no place to attach a silencer or duct to the intake. That's why I'm looking for something different. I tend to agree about cheap knockoffs; in the photos at least, the finish and alignment of these parts is definitely a cut above the usual crud you see on Ebay. By trolling the seller feedback, I've identified people who bought BOVs from the seller in early June. I've sent direct ebay messages to them to ask about quality, etc. I'll share the feedback I get.

[dapinky]

Not trying to say that THIS seller would do such a thing, but are you certain that the picture is of the item you're actually getting, not a "in the style of" type thing????

[tigerdog]

Of course not - it's ebay The guy moves a tonne of these, though and the feedback is very positive. Either many people have very low standards or the stuff is pretty good. Probably the former...

[tigerdog]

I moved a couple of vintage Blaupunkt car stereos so my newly-padded my Paypal account forced me to buy this valve. Seriously, I've received responses from several people who've purchased BOVs from this seller. Different models, but the response has been 100% positive. Fit and finish are reported as very good or excellent; users report running between 14 and 20 PSI successfully. I'll update the thread, send photos, etc. for $35 bucks (including shipping) it's hard not to experiment.

[Elanlover]

Doug, I had the Turbo XS valve you have then replaced it last year with the H34 an have been very happy.

[tigerdog]

Doug, I had the Turbo XS valve you have then replaced it last year with the H34 an have been very happy.

Yes, it's a bit of a roll of the dice but for $125 or so (the difference between this and the H34) it's worth it to experiment. if we were talking about a wastegate it'd be different but if this malfs, there's no immediate damage.
H34 is plan B.

[tigerdog]

I received the valve and I'm very pleasantly surprised. Surface is polished to a near mirror, valve/piston moves smoothly. The vacuum fitting is sealed with an o-ring instead of a tapered pipe thread, but I don't see that as a major issue; I really expected it to be threaded in place and sealed with muck. I'll take a few photos as I replace the TurboXS with this one. Initially, I'll leave the little megaphone in place for testing, then replace it with a duct to the intake if all works out.

[tigerdog]

I installed the valve and using the tried-and-true method learned from audio-balancing SU carburettors, I stuck a tube in my ear and placed the other end into the valve outlet. With the car running, I tried to tighten the spring adjustment until the valve was just closed at idle; unfortunately the stock spring with this unit is inadequate to the task. So I've disassembled the valve and taken a few photos. I'm still pretty impressed with the build quality for an item that's less than a quarter the price of the usual suspects.

Using the highly scientific method of placing the spring on my bathroom scale and pushing down, I saw it needed only about 6 lbs pushing to compress 1" and only about 18 lbs to completely compress the spring. Today I will trundle off to my handy industrial hardware supplier in search of a replacement and report the results.

BOV 001.JPG

BOV 009-1.JPG

BOV 013-1.JPG

[tigerdog]

I've picked up a couple of promising springs from the friendly local industrial hardware store (Is there anything Marshall's doesn't have???) In my initial try, I still had it too tight and I'm beginning to believe the design of this valve (simple tapered seat) does not lend itself to free-air venting; if the spring is loose enough for the valve to open in vacuum, it's open (albeit slightly) at idle. Unless the turbo is still spinning, there a chance the engine might draw air back through the intake. The TurboXS valve has a stepped piston with quite a bit of "slide" before it exposes the outlet port. This leaves more adjustment to balance against vacuum before the valve begins to open. More to follow.

[ektrolleyboy]

After doing my research I was led to believe that the 'trumpet' stle valves are much louder than the piston type. Would you concur?

[tigerdog]

After doing my research I was led to believe that the 'trumpet' stle valves are much louder than the piston type. Would you concur?

Yes, but that's not a function of the valve type so much as the trumpet itself. Whether a poppet valve like Greddy or piston valve like TurboXS, the trumpet on the outlet acts to restrict the dispersion of the sound at wavelengths shorter than the length of the "trumpet". As such, the energy at those frequencies is focused and therefore louder. Regarding the cheapie valve I'm experimenting with, the trumpet is removable; my plan is to replace it with a length of straight pipe, connected to a duct into the air cleaner.

[tigerdog]

Here's a vid of the Ebay valve equipped with an auxiliary high tech airflow indication system. Note that most of the time, even at idle, there is outward airflow. However, as vacuum momentarily increases just off idle, air flows in through the valve until the vacuum is overcome by spring pressure to close the valve. Vid plays with quicktime on windows & mac; my Linux box shows vid but no audio.

VideoClicky

Thanks, Chris!

[tweetdriver63]

Here's a vid of the Ebay valve equipped with an auxiliary high tech airflow indication system. Note that most of the time, even at idle, there is outward airflow. However, as vacuum momentarily increases just off idle, air flows in through the valve until the vacuum is overcome by spring pressure to close the valve. Vid plays with quicktimeo on windows & mac; my Linux box shows vid but no audio.

Where??

[tigerdog]

I finally got a chance to exercise the Elan a bit with the new valve in place. First impressions are quite good now that the new spring is fitted. As noted before, the design of the valve holds it slightly open at idle and the initial throttle blip draws air in through the valve. This behavior has actually cured a problem Smaug has had since day one - a tendancy to hesitate when moving from a standing stop. I have no way of proving, but I suspect the bigger injectors overfuel slightly when the throttle is opened; the faster inrush of air through the BOV allows the engine to breathe and burn the fuel instead of going over-rich.

Second thing I noticed: even with its little megaphone venting to atmosphere, this valve is quieter than the TurboXS valve I had in place before.

Third, and for reasons completely unclear, the engine now boosts consistently to 11PSI instead of 8-9, as expected by the 3 Bar MAP sensor's voltage fooling the ECU. More driving is needed to prove this is related to the valve but I like it!

Engine w New BOV SMALL'.jpg

Finally, it looks nice under the bonnet and my total cash outlay so far is $35.98 for the valve and postage plus $2.95 for the stronger spring. That puts me about $100 in the black compared to buying a TurboXS type H34. I'm happy so far.

Next step is to connect the outlet into the clean-air system.

[tigerdog]

In the photos above, you can see the valve (blue) is a simple tapered poppet that mates with a seat in the body of the BOV. The trouble with this design is that there is zero tolerance for manifold vacuum at idle. Either the spring holds it closed, or it doesn't. Valves like the TurboXS (and maybe Greddy) use a stepped piston instead of an angled seat, so the valve can float a bit at idle but still release pressure when needed. If the BOV you choose uses an angled-seat poppet, it must be ducted to the clean-air side of the intake. In this configuration, one pseudo-scholarly web reference calls it a "Compressor Bypass Valve." Regardless of what you call it, at throttle opening just off idle, air can pass into the engine without having to run through the entire intake duct maze, meaning the initial off-idle demands can be met more quickly. The video linked above shows this behavior. Tomorrow, I'll discover how it feels on the road.

[lotos]

The video does well to explain what you're saying - vent the valve into the air cleaner because it's sucking air into the engine - and unfiltered air be dangerous!

You could always simply use one of those sound-suppression fittings on the valve, I'm sure that it does some filtering.

[tigerdog]

I have completed a recirculation duct so the BOV output connects to the clean side of the intake. An 8" piece of 3/4" rubber radiator hose (cost $0.79) and a 90 degree 3/4" barb-to-pipe fitting ($1.79). I used an Exact-o to knife cut a tidy hole in the end of the K&N filter for the fitting. The 3/4" hose is a press-fit into the threads of the BOV body. I coated it with RTV silicone seal before attaching it in place of the tiny megaphone. I re-used two clamps left-over from last summer's coolant pipe change; the one at the BOV end is just for show - it doesn't clamp to anything! The only change I'll make is to substitute a black right-angle fitting when I can find one.

Driving impressions are very positive. The annoying boy-racer PWOOSHHH is gone, replaced by a muted exhalation. The car now sounds like the Porsche-priced vehicle it once was, not some chavved-up JDM wannabe in the Yoshinoya Beef Bowl car park. Whether by mis-adjustment or by design, the old TurboXS BOV allowed some stalling of the turbine, manifested in the same "whiffling" noise heard with the stock setup. When it did blow, it was LOUD. The new setup, by comparison, displays almost zero whiffle. Every now and then you can hear it for a fraction of a second when going from part- to no-throttle coasting as the valve opens. The turbine spins up much more quickly, especially during on-off-on transitions. When the valve opens from max boost, a zephyr-like "whaaaaaahh" is audible, but does not impinge. I was afraid the press-fit would not stand up to the pressure of a full boost blow-off but repeated openings at 11PSI have not moved the pipe at all. I'll crank the boost up to 16 PSI for a final test later this week

Total cost for the project was well under $50, including valve and shipping ($34), new spring ($3), rubber pipe and fitting ($2.75). I think I'm a happy puppy.

Engine with new CBV 2 (small).jpg

Engine w New CBV 1 (small).jpg

[Blue_Bullet]

Such a lovely shiny blind engine you got there, something for me to admire and make me think of getting off my ass with Mr Sheen to bling mine up too lol

Thanks for photos and great idea of re-circulating the blow off gases into the air filter!

Do you think this will work with the Bailey Dump ~Valve too into ye old trash can???

See look what you have gone and done,,,,given me more ideas thanks again!

BTW great posts!