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need a option for decel valve after BOV install.

My car now runs amazing ,with just one problem . I get way to much crackeling without the decel valve .I was told u can use a BOV , can I T-off the ARR to I/C < I have a modern type BOV not the recerculating valve>??I can not see the type of adjustable BOV I need on ebay . they all have some sort of horn ,not a hose conector. If you see a link to one I need let me know.
Thanks
Erick Marciano
Old 04-07-2010, 07:15 PM
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Crotchety Old Bastard
 
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The throttle bypass valve is independant of the BOV. Connect the TBV between the intercooler and the intake manifold then hook up the vac line. You should be able to T off the AAR if the T is large enough.
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RarlyL8 Motorsports / M&K Exhaust - 911/930 Exhaust Systems, Turbos, TiAL, CIS Mods/Rebuilds
'78 911SC Widebody, 930 engine, 915 Tranny, K27, SC Cams, RL8 Headers & GT3 Muffler. 350whp @ 0.75bar
Brian B. (256)536-9977 Service@MKExhaust Brian@RarlyL8
Old 04-08-2010, 04:13 AM
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You might try lifting you throttle but keep it open a bit and see if you still get the overrun.

If you do not see an improvement the TBV will not help much.

There are several things that contribute to this. One is a non stock muffler that allows you to hear it more. The main issue is CIS dose not cut fuel off on throttle lift. Part of this is that with throttle lift, control pressure can not be established quick enough and the metering assembly dose not close down as fast as it should so excess fuel is set in. Adding a diaphragm dampener might help some. Last is ignition timing can have impact. Disabling the Vac-Retard function may or may not make a small improvement.

I am a big fan of TBV's so all I am trying to say is it might not cure your issue totally.
Old 04-08-2010, 06:57 AM
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Hi Erick,

Here's an eBay link to a BOV that can be confured to vent to atmosphere, or as a recirculation valve. It's the same unit I'm using as my main recirc valve now. Adjustable Turbo Blow Off Valve OR Bypass Valve : eBay Motors (item 160420879180 end time Apr-12-10 12:11:18 PDT)

I think you're already aware of this, but for posterity I'll repeat it: When I did away with the stock boost recirc valve and associated manifold, I left the AAV/decel valve connected pre-throttle body and left the vacuum line connected as well. Now, when shifting it vents to atmosphere. The only negative (if viewed that way) is that it causes a momentary richer mixture when shifting (AFR's drop to around 10.5 for a half second during shifts or sudden off throttle).
But another unanticipated thing (benefit?) is that on prolonged decelleration (within 2 to 3 seconds of no gas pedal) the pressure in the IC and associated pre-throttle body plumbing drops and is equal to the intake manifold; i.e., a slight vacuum occurs. With the AAV open, it will draw in a small amount of air (thus, I have a small air filter attached to the open end). That little bit of air leans the mixture and seems to prevent any exhaust popping. My vehicle does not gurggle or burbble or pop. But that might also be because I'm running with quite a bit more initial timing than most.

Hope this helps.
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Old 04-08-2010, 07:30 AM
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can i T off from the hose that goes from the B OV to the I/c like this drawing i made, I only have 2 hose conectors at the I/C?
and does the decel valve a bov use the same vacuum hose?
for the ebay link do I need a BOV or a recerculating valve?
thanks

Last edited by ertech; 04-10-2010 at 05:14 AM..
Old 04-09-2010, 08:45 PM
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That BOV on eBay: The only difference between it being configured as a recirc valve vs. a blowoff, is that the recirc configuration has hose connections on both the bottom and side ports. Configured as a standard BOV, it has only the hose connector on the bottom and a horn venting to atmosphere on the side mounts.

The decel valve and the BOV can use the same vacuum line.

You could install it as your drawing indicates, attached to any line on the IC that sees boost pressure, but I'm not clear on what you're trying to accomplish. You stated that you have a modern-type BOV installed. Are you not recirculating the boost, and instead just venting to atmosphere? And are you wanting to put another BOV in there somewhere to vent even more to atmosphere?

You can vent to atmosphere, but it's generally not recommended because of the pig rich condition it will cause when shifting and possibly increasing your turbo lag. The small amount that my AAV/decel valve vents to atmosphere doesn't cause huge rich mixture swings because it isn't letting all that much air out.

Please explain a bit more on your setup. I'm a little dense today.
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Mark H. 1987 930, GP White, Wevo shifter, Borla exhaust, stock everything else. The result of a massive Pelicanite good will fire recovery effort. Truely an open book, ready for the slippery slopes to modification.
Old 04-10-2010, 06:28 AM
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If you are tied to using all of those devices and that intercooler then you have little to lose by attempting the sharing of vac ports.
Optimally all of these devices need their own large vac port and should not share unless the port is large enough to support both or if both devices are not open at the same time (which isn't the case). You typically don't need both AAV and AAR. I would ditch the AAV in favor of a throttle bipass valve (TBV) if you are looking to reduce exhaust cackle on decel. The current setup on my personal car has niether AAV or AAR, only a 965BOV and TBV. I am near the end of designing an intercooler that fits both stock and 965BOV configurations and have been working with all the issues you are now experiencing. There will be enough ports to accommodate all of these devices.

Mark, one side issue with the BOV open to ambient air is oil spray. There is a film of oil always present in the intake track which will be pressurized when that BOV opens. Just a picky point ...
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'78 911SC Widebody, 930 engine, 915 Tranny, K27, SC Cams, RL8 Headers & GT3 Muffler. 350whp @ 0.75bar
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Old 04-10-2010, 06:42 AM
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i AM SO CONFUSED WHAT IS A TBV?
WHAT i WANT TO INSTALL IS THE SAUCER THING WITH VACUUM ON ONE SIDE AND THE 2 OUTLETS ON THE OTHER SIDE.
sorry for the caps forgot them on .
what does a TBV look like ? and will it reduce the poping/crackeling ?
Thnaks
PS: for mark:my modern BOV blows to the I/C.I want to unse a BOV insted of the old AAV to send some air under the TB at decel to mininze the cracking Thanks

Last edited by ertech; 04-10-2010 at 07:00 AM..
Old 04-10-2010, 06:54 AM
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Quote:
Originally Posted by mark houghton View Post
Hi Erick,


When I did away with the stock boost recirc valve and associated manifold, I left the AAV/decel valve connected pre-throttle body and left the vacuum line connected as well. Now, when shifting it vents to atmosphere. The only negative (if viewed that way) is that it causes a momentary richer mixture when shifting (AFR's drop to around 10.5 for a half second during shifts or sudden off throttle).
I did this too.
Being able to shift immediately keeps the turbo from decelerating as much. Now when I get into the throttle after shifting I've already got 2-3 psi of boost instead of 0.
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Old 04-10-2010, 08:06 AM
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Quote:
Originally Posted by ertech View Post
i AM SO CONFUSED WHAT IS A TBV?
WHAT i WANT TO INSTALL IS THE SAUCER THING WITH VACUUM ON ONE SIDE AND THE 2 OUTLETS ON THE OTHER SIDE.
sorry for the caps forgot them on .
what does a TBV look like ? and will it reduce the poping/crackeling ?
Thnaks
PS: for mark:my modern BOV blows to the I/C.I want to unse a BOV insted of the old AAV to send some air under the TB at decel to mininze the cracking Thanks
LOL! This can be confusing, using the "written word" to try to describe things. Interpretting AAV, AAR, TBV, IC, BOV...$hit, all these abbreviated "things" and what DO they do!

Ok, so you want to use the saucer-shaped (decel valve) thing to add some air post-TB. That's cool, and is exactly how I'm using mine. Why not use yours, then, vs. using a BOV instead. A BOV will let a lot more air into the intake than you probably want. Maybe that's why you're looking for an adjustable BOV to limit the amount of air being injected (but the term "adjustable BOV" usually refers to adjusting the opening point via spring tension). That BOV that I pointed you to has almost 1" openings and will move a lot of air. Unless your saucer-thing is toast, I would consider using it instead, or a throttle body valve as Brian pointed out.

Brian, good point on the oil mist. Just another reason why venting to atmosphere may not be the best thing.

One more comment: For BOV vacuum source, I'm using the original stock location that actuated the old boost recirc piston valve (big half inch? pipe on the intake manifold, necked down with a nipple). Lots of vacuum there and would most likely support more than one line if needed.

Not sure if this is helping. Hope it is.....
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Old 04-10-2010, 08:07 AM
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Quote:
Originally Posted by RarlyL8 View Post
I am near the end of designing an intercooler that fits both stock and 965BOV configurations and have been working with all the issues you are now experiencing. There will be enough ports to accommodate all of these devices.
I'm a buyer when you get it done! Thanks
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Old 04-10-2010, 09:34 AM
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Here is a (highjacked) picture of Mark's 965 BOV (blow off valve) setup clearly showing the TBV (throttle bipass valve).




Here is a picture of my current setup with the TBV installed in the stock location using a modified 930 BOV housing. You can see it on the left side of the assembly.




This is where I plumbed the 965BOV on my old B&B Intercooler while designing my new one. Not too user friendly for those with a functional AAR.




The latest prototype will be completed and ready for testing in 2 weeks. I think this will be the last version and if so we will begin production after testing.


.
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'78 911SC Widebody, 930 engine, 915 Tranny, K27, SC Cams, RL8 Headers & GT3 Muffler. 350whp @ 0.75bar
Brian B. (256)536-9977 Service@MKExhaust Brian@RarlyL8

Last edited by RarlyL8; 04-10-2010 at 12:18 PM..
Old 04-10-2010, 12:13 PM
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Brian

Looks like electronic monitoring of control pressure?

Cool!
Old 04-11-2010, 07:33 AM
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just finished the car as per my drawing and no more crackeling .runs fine but as expected the rpm do not drop between shifts like before.
Thanks all will post pics later today
Old 04-11-2010, 08:15 AM
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It's good to know that you were able to share vac ports with no ill affects. I've got a few large T's that may work in a couple of spots when all these CIS air control devices are in use.
Please do show pictures. I'm moving this stuff around as well so any configurations that have been tested and work are useful.

Keith yes I am doing a lot of experimentation right now that requires I keep an eye on a few key parameters.
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'78 911SC Widebody, 930 engine, 915 Tranny, K27, SC Cams, RL8 Headers & GT3 Muffler. 350whp @ 0.75bar
Brian B. (256)536-9977 Service@MKExhaust Brian@RarlyL8
Old 04-11-2010, 10:01 AM
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Brian, so you are currently running the vaccum limiter valve (decel valve) - why is that?

I have not run one for about a year (after determining that mine was bad) - I like the throttle responce without it in place, but the overrun crackling/popping is really excessive. I am thinking about getting a used one via eBay and try running with it again . . .

Ron
Old 04-11-2010, 11:43 AM
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B,

With your CP moniter have you seen if CP is stable with throtle lift at higher rpm?

Do you see a temporary drop and/ or spike before recovery in CP?

Thx.
Old 04-11-2010, 11:51 AM
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Ron, one of the side effects of my free flowing mufflers is cackle on decel. This is exaggerated in the Hooligan (no sound deadening material) muffler. Some folks don't like the cackle so I put the decel valve back on my car to see what the reduction would be. It was reduced significantly. I also have it on while testing my new intercooler for all the possible vac/boost related connections.

Keith, my LM-1 is still very noisy so I have no exact data. I am still working out what I think are grounding issues. If I smooth the curves enough to get usable info the spikes are smoothed as well.
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'78 911SC Widebody, 930 engine, 915 Tranny, K27, SC Cams, RL8 Headers & GT3 Muffler. 350whp @ 0.75bar
Brian B. (256)536-9977 Service@MKExhaust Brian@RarlyL8
Old 04-11-2010, 05:22 PM
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Brian,

Great effort.

It will be cool when you will be able to see what CIS is really doing!

Larry at CIS Flowtech mentioned System Pressure drops significantly when the FD is working at higher flows. Might be interesting if you could monitor that to, at some point.

If this is true, looking at the fuel pumps might help gross delivery and or take some of the leanness off the upper RPM area. It would be interesting if we found it was the drop in System Pressure at high rpm that makes for the AFR's getting progressively leaner instead of the metering plate starting to slow or stall.

Fun stuff and good luck with it. Guesses are fun but real info rules.

The best.
Old 04-12-2010, 07:08 AM
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