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How bad is the rich spike if I put a BOV on my 740?

Ohh, I can add to the never dying thread as well. When I put my BOV on my LH 2.2 Auto car, it ran a bit rough as well, mainly at low speeds. THe car did exactly as others noted in that it would stumble and almost die when jsut slowly coasting around town. I I drove it hard, it was no problem, I think becuase when it shifted the rpm's in the next gear were much higher when I would jsut dabble around. It seems like the trend that in an auto the BOV will give you issues using any sort of LH, where as in a manual it seems to work ok.
 
I have noticed a real difference in mine since i put it on, its deff got worse as in stalling and not feeling right but ive only started on the car so ill get it sorted!!!
 
Geoff240Ti said:
I'm running a turboXS BOV vented to atmosphere on my B230ft lh2.2
245070.jpg


As far as I can tell everything is working a-ok, no puffs between shifts.. it's very smooth. No sign of stalling or studdering or anything.

I never installed the factory CBV.. so I can't compare it to that setup. I'm not to sure why my setup works with no issues! The spring tension seems fairly high.. it won't blow off under 4 psi but it dumps after 5psi with sound.

I know bosh made a CBV specially for porsche, it is bigger, more stable in its releases and sounds better than the stock volvo CBV, has anyone every heard of someone swapping to stocker for a porsche one???

BTW, im looking at your engine bay (clean, sweet) and i fail to see an AMM????, If you have no amm that might exlplain why you have no problems with your bov. Anywayz, cya
 
My 2 cents

Ive read this post a few times and i thought id just put my own 2cents in about CBV's BOV's :

CBV's- COMPRESSOR BYPASS VALVE- come stock with many turbocharged cars. Always plumbed back into the intake tract at some point to keep metered air in a cycle. Normally before the turbo. At idle and non-WOT throttle position, the CBVs DO NOT seal, and leak air back through the intake. ON WOT, the CBV seals to prevent the air from escaping. When the throttle closes, engine vacuum pressure causes the seal open to release the air back into the intake and prevent the air from returning through the piping to the Compressor wheel of the turbo. With a pod style filter on, you can hear the CBV open when the throttle is released. Regardless of transmission type- if the throttle is released quickly air will be vented through the CBV. Therefore, CBV's should only be used in a plumb-back setup.

BOV- BLOW OFF VALVE- Can, but not always, be vented to the atmosphere. Some are designed with trumpets etc to make nice noises, and others are designed like a CBV to plumb back into the intake tract. BOV's have a spring inside to ensure that the valve is sealed ALL THE TIME and should only open when sufficient engine vacuum causes the valve to open. Many BOV's are adjustable to change the rate of the spring, and therefore adjust how much vacuum is required for the valve to open. Setting the valve to a 'soft' setting will make the valve behave similarly to a CBV, in that it may leak at idle an non-WOT position. This is what causes poor running and stalling in AFM equipped cars. Setting the valve to a 'hard' setting keeps the valve sealed until there is enough vac to open it- ie, on rapid throttle release. In this case, however, compressor surge may occur when there is not enough vacuum to open the valve, but the throttle is closed quickly. On a blip of the throttle, you may get a 'ch ch ch' out of the air filter, which is compressor surge. On a WOT blip, you should get a 'pshh'. If that makes sense!

You should be able to try this on any AFM car, and i have many times before. With the engine at idle, if you loosen the BOV you will eventually find the car will idle badly. Similarly, adjustments can be made by tightening the valve a little and then testing my revving the motor to see when it vents.

Assuming the valve is adjusted properly, there should be few problems with fitting a BOV to an AFM equipped car. It may run a little rich when the valve vents, but if it is adjusted propely, it should only be venting for a very short amount of time.

Hope this helps a bit
Cheers
Chris
 
Geoff240Ti said:

Back from the dead..again..

I wondered about this too. He doesn't appear to have an AMM or any other sort of device. But I was under the impression that it was neccessary...can anyone clear this up for me?
 
Cbv conspiracy theory

Im youre thinking of getting a cbv, heres my 10 cents.

Bosh made one for stock porshe 911 turbo's, its is higher quality than the volvo ones and can flow a bit more air.

One downside to a cbv that has not been discussed yet. This is theory and the difference may be neglectable. When air goes thru the compressor, it heats up quite a bit, thus the need for an IC. If the cbv redirects compressed (hot) air back into the compressor inlet, that hot air would get even hotter as it goes thru the compressor a second time.

Now it is possible that this makes near nothing of a difference but if you are shifting at redline under full throttle, there is alot of air that will go thru the cbv and you compressor will be particularly hot at the time.

And depending on how much of a grannyshifter you are, that same air could get redirected thru the cbv 2 or more times. (as the turbo is still spinning between shifts)

This is my theory, anyone have any feedback, theory bashing, lol! I dont claim this to be the thruth, only an idea
 
I just can't resist! So, it is time to resurrect this thread!

So, what if the CBV is placed after the intercooler and before the throttle body. Wouldn't that mean that it is seeing cooler air even though not as cool as ambient?
 
i want the BOV noise DAMN IT

lol


i like the porche spec bosch CBV idea..i'll see if i can do anything with that when i go to the JY next time...
 
Got the Greddy type RS on 2.4 and it puffs some serious clouds (black) Hitting like 10psi in 4 gear and letting on and off the gas real quick does the trick. It some serious rich spiking but its fun sometimes :)
 
From reading through this thread, it's quite obvious that BOV's simply CAN'T work on LH systems (and there seems to be debate on the K-jet systems). The best bet seems to be to go with a cone filter, since that should provide the sound your looking for, without anything else or any other problems. I work as a Subaru tech at a local dealership, and it's the same way on STI's. Although they don't have a problem when they do run BOV's, the same sound can be acomplished by simply running a cone filter. On every lift of the throttle, you hear the BOV noise most people are looking for, but through the stock recirculation valve. It's actually pretty loud too, and it sounds just like a regular BOV.

Anyone with experiance on running a cone filter on the 700 or 900 series turbo's feel free to post here. It seems like it'd work, and I thought I remembered reading something about it in this thread even.
 
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