emilios

Hi everyone,

I've just had a new, adhustable Hyperboost CBV/diverter valve fitted to my '94 964/5 turbo 3,6 installed to replace the OE Bosch item. The car is now so much smoother and so much more drivable than before, even off-boost (don't know if this is due to the new CBV or not).

The brochure says "the adjustable valve allows you to fine-tune turbo actuation points for supreme performace".

Does anybody know what/how the Hyperboost adjustment procedure is?

I contacted Stratmoshere (where I bought the CBV from) and was told "(..turning the adjuster) clockwise is more pre-load, anti-clockwise is less" - What does that mean - how does that work?

Any assistance greatly appreciated.

Many thanks and best regards

Emilios

fc-racer

Emilio,

You essentially want enough resistance that the CBV does not leak boost, but you also don't want it so tight that it cannot discharge the excess pressure on light boost settings. A car that is running at full throttle all day long should use a higher setting to prevent boost leakage, but a car driven on the street should use a lighter setting so it can blow off quicker and be more responsive.

It's tough to explain, but when you play with the settings, you will know what I mean. The funnest setting will be when you are too loose and it's leaking boost, if it's vented to atmosphere rather than piped back, you will get a wicked turbo noise, but you are losing boost so don't get addicted to the sound

Is your vented to atmosphere or back into the intake?

emilios

Hello fc-racer, and thank you very much for your assistance.

With regards to your question, all the connections were as per the OEM valve.

Thanks and best regards

Emilios

Olli Snellman

If you want to have original look then your best choise is to have Bosch valve 0-280-142-110.
It's better than 993 valve. It was originally used in Saab 9000 Turbo models.
I used to have 993 valve in my 951. Comparing to this 993 valve Saab valves spring is much stiffer.
I just bought one for 35 euros <img border="0" title="" alt="[Wink]" src="wink.gif" />

John McM

FWIW: After all of the recent talk about CBVs, I decided to test the one on my car ['93 Turbo 3.6 with 53k miles on the clock].

It took all of five minutes to remove the CBV for testing. Given the part number is 0280 142 102, I gather it is the original one.

Blowing through the intercooler side of the valve I detected leakage out the top vacuum pipe connection, but none out of the bottom pipe.

My conclusion is that the diaphragm is ruptured and therefore my CBV isn't working. Thankfully, the spring is still working so I don't think the performance is affected on boost.

I rang the OPC and they quoted part 993.110.337.50 for NZD 197 [USD 134]. With Pelican listing the same part @ USD 46.24 I know where I'll be going if I decide to replace it with an OEM part.

69COU

I think this is the correct one. I hope so as i have just ordered one from Forge Motorsport on the basis that for £100 it will replace a part that seems to play up on most of our cars.

FMDV007P
Fast Road Closed Loop Diverter Valve (piston)

Fitment Guide
All VAG 1.8T engines
All VAG 2.7 Bi-Turbo engines
Porsche 911/996 turbo
Made from billet aluminium, this recirculating diverter valve dumps the charge-air back into the air intake system keeping external noise to a minimum. This increases both quicker throttle response and higher clamping load to maintain boost pressure more reliably.

___________________________________________

Hope the above is the right replacement as i have just read the following.


Just ordered but have read this on an earlier link.
Primary reason is to reduce strain on the compressor turbine wheel due to compressor surge. Between shifts, or sudden throttle lift-off, the turbine is still spinning very fast (but slowing) and pumping air at the closed throttle plate, as well as placing strain on the intercooler, hoses and fittings. A CBV / BOV keeps air from flowing backwards over the compressor wheel, allowing the turbine to continue spinning freely. When back on the throttle, boost pressure quickly rises again with little lag. A suitable valve location is just before the throttle plate.

A CBV must be used with Bosch K-Jet injection, as being a closed system, any loss of air for which fuel has already been metered by the movement of the airflow sensor plate, will result in an over-rich condition and possible backfire. A CBV is found on many "OEM" original engine manufactured EFI turbo systems.

A BOV is suited to an EFI system that uses a MAP (manifold absolute pressure) sensor. As the MAP sensor source is inside the inlet manifold's plenum chamber, relieving air before this with a closed throttle butterfly (throttle lift-off) will not affect running.

cobalt

I just posted a thread the other day regarding this same valve. I replaced my 30k mile valve with the nonadjustable EVO bypass valve advertised by Paragon products on the 911 forum page. I figured for $104.00 and lifetime warrantee what the heck. The old valve does leak and when I replaced it with the new one the results were outstanding.

However I had questions on the readings I was getting from my boost gauge. The boost appeared to begin spooling up at much lower RPMS which is what I was told I should be seeing with the B&B exhaust. Previously the boost appeared to start spooling up at the standard 2800 to 3000 rpm range now it was coming on much sooner 2400rpm range. By the seat of the pants feel I was definitely gaining considerable acceleration by maintaining boost between shifts.

What concerned me more than anything was the fact that I was seeing a reading of .3 bar at 80mph with slight throttle as before I saw nothing and when i brought the car to a complete stop I was still reading .2 bar which eventually dropped to .1 bar but would not drop to 0.0 until I turned off the engine and restarted it.

Could this be what you are talking about that it is to tight and not discharging the excess pressure? If this is the case could this new valve be of no value or does it need a break in period. I plan on only using the car for the street. DO you have any opinions on this new valve.

fc-racer

There must be something wrong with your boost pressure sensor. Maybe you knocked while installing the bypass valve. Unless you have anti-lag, you can't get boost at idle (well, without revving it to 6500 under load of course). I would hook up a mechanical boost gauge first and see what it shows.

Your gains sound about right for a car with a bad valve. As an aside, while doing my injectors today, I checked on the condition of my forge valve. I found the piston inside to be binding a bit. Opened it up, cleaned it up, re-fit it all and it works great again and I notice a difference between shifts so it must have gummed up after two years of use. It's great that you can just whip the top off, clean things up and re-install.

1mturo

I'm confused. I just replaced my intake entire air box with an individual filter for the intake and the other two hoses connecting to the air box. I was on the track yesterday and noticed considerable turbo lag that I did not experience in the past prior to the change. In the higher gears the boost would just fall off between shifts. Lowering my overall top speed. What is the problem? Is it the CB valve or is something not connected right? Other than that the car ran great.

fc-racer

My hunch would be that your new air filter is collecting hot air which is causing your low hp. You may have also torn your CBV in the harsher racetrack environment. Checking it is a 10min job so you can't go wrong testing it out before doing anything else.

I would highly recommend a Forge or Bailey valve, you will never have to replace it again. I have had the 993 valve tear as well, and it's not as efficient as the Forge valve.

1mturo

Does the CBV valve plug into the airbox in some way? I had good boost after a shift before the air box was replaced.

fc-racer

The CBV pipes into the intercooler and then back into the inlet pipe leading from the plunger to the turbocharger. Maybe while they installed the airbox, they put the intercooler back on poorly and now you have a leak there? Check that stupid orange o-ring at the intercooler/throttly body neck.

1mturo

I took the CBV valve off. I am not sure when you mentioned blow in it, what part to blow in. I blew into the small nipple at the top that I guess connects to a vacuum device and there was no air flow through the other two openings. I blew through the side Intercooler opening and when doing that air blew through the nipple. I blew through the bottom part and no air passed through the other openings. I pressed against the bottom of the valve and pushed it up. It will move, it seems to be under heavy spring pressure. How does that sound?

Also you mention picking up power venting to the atmosphere, why do think that is? How did you do it? Did you block off the inlet to the intercooler?

John McM

Michael,

The way I assume that this valve works is that vacuum applied to the top nipple sucks the diapragm up and opens the valve against the spring force. When the vacuum is no longer applied then the spring helps force the valve closed.

If that assumption is correction, then blowing through the side intercooler opening shouldn't allow air to come out of the nipple unless the diaphragm is ruptured. If the the diaphragm is ruptured, then the valve won't open and the CBV can't do its job. NB: I hope I'm correct, as I've just ordered two of the replacement OEM valves on that assumption.

I can't help you with the sound it makes when working, as I'm not sure mine has ever worked while I've owned the car.

KeithC2Turto

John,

That is how I understand them to work.

The nipple on top is hooked to the manifold section and receives vac when you let off the throtle or are at cruse. This adds presure which works toward trying to open it which is offset agenst the spring tension & boost pressure.

It also receives boost presure to help keep it closed as it only has about 5 lbs of presure from the spring.

The stock valve is realy a nice effecent fast acting design that probably flows very well but seems prone to failure.

A beter way to test it is to put a mini vac on it and see if it holds vac or pressure at a low level.

Don't stick your finger in it and push the valve open manualy as I think this creats a high potental to rupture it.

I went to the Stratospher adjustable also as I thought it had a larger piston in the top end which should creat more force to open or close the valve.

I will likely change the orintation of my valve soon as a test.

I suspect that in the stock or normal orintation that there is suction in the intake tract in the area between the metering plate and turbo that at high rpms is exerting force that is working toward trying to keep it closed. Also w 15psi of presure from the side, there might be some side loading of the plunger valve. Don't know if these are significant loads or a concern but this in my intuition.

Changing the orintation will set the boost up to assisit in pushing the plunger valve open for a faster response when the throtle body is slammed shut.

Also our De-accel Valve helps some to release preaure by venting it back into the intake manafold but only dose so at prety high pressure.

On the CBV spring tension combined with boost presure on the valve top is what keeps it closed.

The second the boost to the top of the valve is killed the boost trying to open it should make it open faster.

If you look at the EFI blow off valves they put them in this way when they vent them.

Thought of also puting another valve on the AAV tube w a tee conector. This would double the relive capacaty. I would vent it. Yes this will make it go a bit rich on shifts.

I think this was an old 935 trick as they pushed extra fuel out to the exaust during shifts which turned the turbo into a turbine which kept is spinning between shifts. Not the best way to keep your turbo healthy though.

Can you say flames!!!

Just an idea anyway.

Another idea! I don't know of this is a proper aplication but I estimate that during each rpm we have about 1.75 intake valves open at anyone time and that when we shift we are droping our intake duty needs by about 70%. Thus if we wanted to try to have a CVB that was large enough to equal our air flow needs we would need a CBV w an effective port "area" (not width)of about 122% the size of ones intake port size.

Thus a 32mm port motor could use about a 1.4" ID port. Even two standard valves would be on the small side but one 1.5" od valve could be about right.

Not sure if this is a propper approach but this is my intuition.

Keith