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Quote:
Originally Posted by RarlyL8 View Post
If you must leave the decel valve mounted on your engine at least put a rubber nipple on the vac port feeding it and one the port on the face of the valve.
I can see a set of vice grips going through your engine fan ...
You didn't really take me seriously about the vice grip bracket, did you?
Hey, vice grips are expensive. There's no way I'd want to damage them in the fan!
Old 07-17-2008, 09:00 PM
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You wouldn't believe what I've seen.

Glad you are more on the ball than that. Unfortunately humor doesn't translate well with the typed word. I started a firestorm on a thread about the C2T digi-gage setup due to misinterpretation of my style of humor. Guess we'll have to wait for the web to go live view, ha!
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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 07-18-2008, 03:53 AM
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Great reading, all of this. Thanks for all your contributions.

So the moral of the story is to leave "B", the "AAR", in there? I love losing unecessary crap, yoinking that would be great but not if I need it here in chilly CT.

D'oh - I'm "that guy" who plugged the decel valve (with a golf tee and a zip tie - I'm so high fashion)... but left the vacuum port wide open. Now that you type it Brian capping it seems so obvious. Again, d'oh. All seems fine as is, I'll cap it next time I'm in there I guess.

Funny - for some reason, before even reading this thread (I was only in the BOV delete thread until today), I saw the manifold nuts there staring me in the face (I'm sans A/C) and opted to check tension - a couple were pretty darn loose. Well, relatively at least. Nice!

Speaking of sans A/C... I'd LOVE to loose that huge hunka alum. that used to mount the compressor. Quick glance shows the exhaust strap bracket mounted to it. Anyone loose this? Any tips?

I'll be posting up my Jenny Craig results sometime soon - it is ohso gratifying looking at the MOUNTAIN of f'n crap I've pulled off the arse of the biatch thus far. Gotta be 150lbs.

Keep the great ideas flowing gents.


ps. and yes - I too fell for the vice grips bit... too funny.
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Old 07-18-2008, 05:15 AM
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I believe that you could quickly make two little spacers that could replace the spacing that the A/C bracket provides. Although, the a/c bracket could not have weighed more than 2 lbs.
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Old 07-18-2008, 05:25 AM
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Ahhh! Kindred spirits.
I think I'm in love again.
Just love this place.
Old 07-18-2008, 05:29 AM
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YOU CAN TAKE THE BRACKET OFF AND CUT THE PART OFF THAT GOES FROM THE BOTTOM WHERE THE EXHAUST MOUNTS AND COMES INTO THE ENGINE COMPARTMENT TO THE TOP OF THE MOTOR. Thats what I did , Looks very clean. I'm glad to see that your rev problem is solved , another thing you may consider is cleaning the air plate under the air box . My car had the same problem loose bolts and a dirty air plate , tightened bolts and cleaned my plate no problem. Just a thought
Old 07-18-2008, 07:22 AM
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Quote:
Originally Posted by DSPTurtle View Post
I believe that you could quickly make two little spacers that could replace the spacing that the A/C bracket provides. Although, the a/c bracket could not have weighed more than 2 lbs.

Thanks DSP - will do.

2 whole pounds!?!?!? I'll take it! 8-)

Heck, 2lbs here there everywhere - it adds up. I so cannot wait to put my large box 'o JUNK on the scale and weigh that bish. So gratifying - like giving the pig an enormous diharretic... - aahhhhhhhhhhhhhhhhhhh...

Again, to yoink the AAV or to not yoink the AAV - that is the question... Bueller? I bet it's gotta be 0.25lbs!!! 8-)
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past:

| '01 ///M5 | '96 993 C2 cab | '05 S600 Sport - biturbo V12@Just Not Right 495rwhp / 612rwtq |
| '58 TR3A | '01 //S8 | '95 //S6 6gang | '88 ///M5 | '87 190E 2.3-16 |

Last edited by krasuskyp; 07-18-2008 at 10:34 AM..
Old 07-18-2008, 10:17 AM
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If you remove the whole engine and trans you can save like 800 pounds
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Old 07-18-2008, 10:25 AM
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Yank the AAV.
Take advantage of the component design of CIS. You can put the AAV back in the winter if it bothers you.
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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 07-18-2008, 07:09 PM
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How exactly can I delete the decel valve / throttle bypass valve on a 965?
I also would like to enjoy more pops and faster drop of revs while shifting.
Is the easiest way to unplug the hose going from the Bosch Bypass valve to the Decel Valve? Or do I have to plug both connecting points after taking that hose out?? Thanks for any advice!
Old 07-23-2008, 09:18 AM
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You should be able to remove the small vacuum line that goes to it and plug it. There is no need to plug the device itself at all.
Do not muddle the Blow Off / Recirculation Valve with the Decel Valve as you could damage your turbo.
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1981 UK 930. G50/01 shortened, 964 3.8RS Fibreglass Body Kit, 18" Alloys 8.5" F & 10" R, 225's F & 285's R, Special Colour Metallic Blue Paint, FIA Sparco Evo's, A/C and Air Pump removed, Electronic Boost Controller, GHL Headers, Tial46 WG.
Fitting - New service kit.
Needs Fitting - Innovate XD-16 Kit, Kokeln IC. Stephen's K27 HFS, EVO Intake Assy & his Modded USA Fuel Head.

1983 UK 911 3.2 Carrera Sport Coupe. Black, Black Leather with Red Piping, Black Alloy Gear Knob, K&N Air Filter Element, Turbo Tie rods.
Needs Fitting - K&N CO Sensor, Round A/F Dial Gauge, Factory Short Shift Kit.

http://www.danasoft.com/sig/Iamnotanumber.jpg
Old 07-23-2008, 12:05 PM
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Quote:
Originally Posted by gogomobil View Post
How exactly can I delete the decel valve / throttle bypass valve on a 965?
I also would like to enjoy more pops and faster drop of revs while shifting.
Is the easiest way to unplug the hose going from the Bosch Bypass valve to the Decel Valve? Or do I have to plug both connecting points after taking that hose out?? Thanks for any advice!
You would have to plug the hose going into the intake, plug the signal line that runs to the decel valve and vent the recirculation valve (bov) to atmosphere.
Better yet, if you have an aftermarket recirculation valve (bov) tune it with the different springs that should have been supplied with the bov. If you have a OE bov, replace it as the spring is too weak or the diaphram is ruptured.
I had the hanging RPM and I cured it by installing the intermediate spring supplied with my Forge bov. The weaker spring popped open too quickly, causing a big pressure impulse to be pushed into the intake and causing the RPMs to hang for a second, which is like an eternity. The heavier spring allows for a slower opening and a more controlled air dump to the intake.
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Old 09-07-2008, 09:27 AM
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The question asked by gogomobil is about the decel valve, not the BOV.
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1981 UK 930. G50/01 shortened, 964 3.8RS Fibreglass Body Kit, 18" Alloys 8.5" F & 10" R, 225's F & 285's R, Special Colour Metallic Blue Paint, FIA Sparco Evo's, A/C and Air Pump removed, Electronic Boost Controller, GHL Headers, Tial46 WG.
Fitting - New service kit.
Needs Fitting - Innovate XD-16 Kit, Kokeln IC. Stephen's K27 HFS, EVO Intake Assy & his Modded USA Fuel Head.

1983 UK 911 3.2 Carrera Sport Coupe. Black, Black Leather with Red Piping, Black Alloy Gear Knob, K&N Air Filter Element, Turbo Tie rods.
Needs Fitting - K&N CO Sensor, Round A/F Dial Gauge, Factory Short Shift Kit.

http://www.danasoft.com/sig/Iamnotanumber.jpg
Old 09-07-2008, 11:15 PM
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Quote:
Originally Posted by NathanUK View Post
The question asked by gogomobil is about the decel valve, not the BOV.
Where do you think the air comes from for the decel valve to move to the intake?
The two are a system; it makes no sense to talk about one without the other.
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Port matched, SC cams, K27/K29 turbo, Roush Performance custom headers w/Tial MV-S dual wastegates, Rarlyl8 muffler, LWFW, GT2 clutch & PP, BL wur, factory RS shifter, RS mounts, FVD timing mod, Big Reds, - 210 lb
Old 09-08-2008, 12:18 PM
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I see what you are saying and you are correct, but the question was how to remove the decel valve. All 3 connections need to be blanked or capped off.

Why do you suggest having the BOV venting to atmosphere?
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1981 UK 930. G50/01 shortened, 964 3.8RS Fibreglass Body Kit, 18" Alloys 8.5" F & 10" R, 225's F & 285's R, Special Colour Metallic Blue Paint, FIA Sparco Evo's, A/C and Air Pump removed, Electronic Boost Controller, GHL Headers, Tial46 WG.
Fitting - New service kit.
Needs Fitting - Innovate XD-16 Kit, Kokeln IC. Stephen's K27 HFS, EVO Intake Assy & his Modded USA Fuel Head.

1983 UK 911 3.2 Carrera Sport Coupe. Black, Black Leather with Red Piping, Black Alloy Gear Knob, K&N Air Filter Element, Turbo Tie rods.
Needs Fitting - K&N CO Sensor, Round A/F Dial Gauge, Factory Short Shift Kit.

http://www.danasoft.com/sig/Iamnotanumber.jpg
Old 09-09-2008, 10:41 AM
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Quote:
Originally Posted by NathanUK View Post
I see what you are saying and you are correct, but the question was how to remove the decel valve. All 3 connections need to be blanked or capped off.

Why do you suggest having the BOV venting to atmosphere?
Because the air that the bov is releasing has to be vented out of the intake tract otherwise you might as well eliminate the bov too, which will eventually damage the compressor.

I just installed a Forge Splitter bov. It vents to both the i/c and the atmosphere. I bought it so that the revs won't hang under boost and it does a great job of venting. Now the revs drop immediately.

Granted I could have got rid of the decel valve, blocked off all the ports on the i/c and had the bov vent to atmosphere but this was a quick and easy way to prove out my theory that the initial spike of high pressure air coupled with the inertia of the bov and decel valve were causing the hanging revs.

The nice thing about the spliter valve is that it comes with a block-off cap so it can be made to function like either a recirc valve or a bov.
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Old 10-11-2008, 10:26 AM
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Venting the BOV to atmosphere is not recommended as it upsets the metering flap of the CIS.

I guess some of the boosted air will enter the engine due to the electrically heated idle control valve. So, venting to atmosphere would cause the revs to drop faster.
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1981 UK 930. G50/01 shortened, 964 3.8RS Fibreglass Body Kit, 18" Alloys 8.5" F & 10" R, 225's F & 285's R, Special Colour Metallic Blue Paint, FIA Sparco Evo's, A/C and Air Pump removed, Electronic Boost Controller, GHL Headers, Tial46 WG.
Fitting - New service kit.
Needs Fitting - Innovate XD-16 Kit, Kokeln IC. Stephen's K27 HFS, EVO Intake Assy & his Modded USA Fuel Head.

1983 UK 911 3.2 Carrera Sport Coupe. Black, Black Leather with Red Piping, Black Alloy Gear Knob, K&N Air Filter Element, Turbo Tie rods.
Needs Fitting - K&N CO Sensor, Round A/F Dial Gauge, Factory Short Shift Kit.

http://www.danasoft.com/sig/Iamnotanumber.jpg
Old 10-11-2008, 04:13 PM
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Quote:
Originally Posted by NathanUK View Post
Venting the BOV to atmosphere is not recommended as it upsets the metering flap of the CIS.

The only reason I can think that the metering flap might get upset is that it will feel neglected
When the air flow across the plate goes to 0, it shuts the fuel off. End of story. It will do that if the bov is shoving air into the intake manifold behind the plate or dumping air to atmosphere because everything is occurring downstream of the plate.
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Old 10-11-2008, 05:57 PM
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I think the theory is that when the bov allows bypass the turbo can continue to spin although there is no exhaust to power it so it will eventually slow down. This should help keep the turbo spooled while changing gear for instance.
Surely when you dump to atmosphere the turbo will also continue to spin but it will pull air through the metering plate causing extra unneeded fuel to get injected as though you just opened the throttle. The turbo once again will eventually slow down.
No bov/recirc should cause the turbo to stop spinning pretty quickly and put it under a lot of unnecessary strain.
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1981 UK 930. G50/01 shortened, 964 3.8RS Fibreglass Body Kit, 18" Alloys 8.5" F & 10" R, 225's F & 285's R, Special Colour Metallic Blue Paint, FIA Sparco Evo's, A/C and Air Pump removed, Electronic Boost Controller, GHL Headers, Tial46 WG.
Fitting - New service kit.
Needs Fitting - Innovate XD-16 Kit, Kokeln IC. Stephen's K27 HFS, EVO Intake Assy & his Modded USA Fuel Head.

1983 UK 911 3.2 Carrera Sport Coupe. Black, Black Leather with Red Piping, Black Alloy Gear Knob, K&N Air Filter Element, Turbo Tie rods.
Needs Fitting - K&N CO Sensor, Round A/F Dial Gauge, Factory Short Shift Kit.

http://www.danasoft.com/sig/Iamnotanumber.jpg
Old 10-11-2008, 11:56 PM
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Quote:
Originally Posted by NathanUK View Post
I think the theory is that when the bov allows bypass the turbo can continue to spin although there is no exhaust to power it so it will eventually slow down. This should help keep the turbo spooled while changing gear for instance.
Surely when you dump to atmosphere the turbo will also continue to spin but it will pull air through the metering plate causing extra unneeded fuel to get injected as though you just opened the throttle. The turbo once again will eventually slow down.
No bov/recirc should cause the turbo to stop spinning pretty quickly and put it under a lot of unnecessary strain.
Nathan, let's back up here for a minute.
High pressure air that gets trapped between the air sensor plate and the throttle plate during a throttle closed event has to be vented somewhere. The factory chose to send it back into the engine for the following reasons (1) emissions as the overrun of the metering plate and extra fuel getting dumped to the engine will be burnt (2) to prevent compressor stall (3) noise abatement. So, the pressure spike that occurs when the throttle butterfly closes gets vented into the engine. Problem is, there's inertia in that air moving into the engine, inertia in the bov and decel valve so they don't open instantaneously, inertia in the vacuum signal going to both valves and hysteresis in the vacuum signal line and air feed lines (rubber flexing).
Dump the high pressure air to atmosphere and only the inertia of the bov alone is present. Hysteresis is no longer a consideration.
When the bov relieves the pressure it closes as the vacuum signal won't overcome the spring force alone in the valve (the bov is designed and tuned so that boost pressure and vacuum pressure > spring force. Therefore no further air will be ingested when the pressure in the intake between the metering plate and the throttle plate drops below the a value that is a little less than full boost pressure.
I agree that to remove or disable the bov will cause bad things to happen (1) the compressor gets hammered and stalls (2) the metering plate oscillates.
I'm not advocating removing or disabling the bov, just changing where it vents to. The metering plate won't know the difference but the driver will because the engine speed will drop much more quickly as less air has to get pumped through the engine when the throttle plate closes.
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'91 964 Turbo
Port matched, SC cams, K27/K29 turbo, Roush Performance custom headers w/Tial MV-S dual wastegates, Rarlyl8 muffler, LWFW, GT2 clutch & PP, BL wur, factory RS shifter, RS mounts, FVD timing mod, Big Reds, - 210 lb
Old 10-12-2008, 06:46 AM
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