B.O.V's....

[Richf]

Originally Posted by ISJ

So you think a turbo compressor wheel - still spinning from the exhaust gases that drives it - will stop?

Remind me again, roughly, how fast does a tubine spin again? Especially one which has just come off full boost....

Exhaust gasses arent sufficient to spin the turbo with the throttle closed , i know my car doesnt make boost on idle , does yours???

The instant the throttle is closed the turbo is already slowing it is subject to friction and spins only due to its own inertia its not a case of how fast its spinning or of how long it takes , 0.5 of a second may seem fast to us but it can be enough time for a turbo to spin up and enough time for it to slow down drastically

I've seen compressor wheels shredded by a nitrous burp and they happen far quicker than a gearchange thats for sure

With 18psi going to the wrong way though any fan what do you think the effects are , Newtons 3rd law comes in here equal and opposite reactions but of course the lower the boost pressure the less effect it will have on the turbo but the slower the turbo will be spinning to start with

Having tried both with and without in the last few months with my car i can assure you the car makes boost quicker and harder between gear changes with a bov and running without causes no end of problems

[Richf]

A comparison to the turbo spinning would be

How long does it take a car to stop from 100mph

A) It would take a long time if the car was allowed to coast to a stop

b) It would happen instantly if the car hit a brick wall

In front of that spinning turbine is a lump of pressurised of air ie a brick wall and as there is nothing driving the turbine to force against the air the air will just push past the turbo and out of the air filter

[ISJ]

Originally Posted by Richf

Exhaust gasses arent sufficient to spin the turbo with the throttle closed ,

Originally Posted by Richf

i know my car doesnt make boost on idle , does yours???

Originally Posted by Richf

The instant the throttle is closed the turbo is already slowing....

Originally Posted by Richf

it is subject to friction and spins only due to its own inertia

It's quite clear to me that you are not willing to accept my explanation as having any degree of truth to it - as demonstrated by your patronising manner (not for the first time I might add) with the dictionary link, and the above quotes.

Then again, I am just a forum in-frequenter and you are the "Nitrous Guy".

You also avoided my question:

Originally Posted by ISJ

So you think a turbo compressor wheel - still spinning from the exhaust gases that drives it - will stop?

If anybody else wishes to educate themselves, I suggest googling compressor stall.

[Kojak]

we can talk about them all day long. However they are made for gayers to fanny about on the high street thinking they look cool.

im right. don't argue with me .. so shut it.

[Jez-R32 GTR]

I'm a gayer so i should know.

[Lambo Door Kits Ltd.]

Originally Posted by Richf

If boost pushes back against a compressor wheel it will slow or stop or STALL ie bring to a standstill which is the correct use of the word stall

stall definition |Dictionary.com

Afraid not buddy, the definition stall in the dictionary was referring to a numpty with crap clutch control.

I have run Giant compressors in the guise of Tornado Rolls royce engines and believe me the blades don`t stop spinning. With a locked in surge the air flow goes back and forth and it`s quite scary. Stall is the definition of an aerofoil with an angle of attack greater than 15 degrees. The aerofoil can not longer create lift and stalls.

We also have B.O.V`s on aircraft engines. They are open until 85% NH that`s basically an RPM scale related to Aircraft engines. The B.O.V is there to release the excess pressure built up to prevent surge or stalling. Compressor do exactly what they are named after. They compress the air by use of a divergent ducts. Divergent ducts increase pressure where as Convergent ducts in the turbine incesase velocity of gas. Therefore the aircraft goes forward as the gases are accelerated out the exhaust. However at the speed of sound this process is reversed.

[Bubble]

Sits back and opens another packet

[Lambo Door Kits Ltd.]

Originally Posted by Bubble

Sits back and opens another packet

Enjoying the show Geoff?

[Richf]

Originally Posted by ISJ

It's quite clear to me that you are not willing to accept my explanation as having any degree of truth to it - as demonstrated by your patronising manner (not for the first time I might add) with the dictionary link, and the above quotes.

Then again, I am just a forum in-frequenter and you are the "Nitrous Guy".

You also avoided my question:


If anybody else wishes to educate themselves, I suggest googling compressor stall.

Oh well if i'm patronising then add me to your ignore list , you are going on mine

Pressure flowing back through a turbine slows and eventually will stop the blades yes, with the throttle shut there is nothing to drive the turbo so yes it will slow or stall and it will do this with a bov fitted or without one fitted but if there is no load or area to pressurise then this will take longer as there is less resistance

Do i think the turbine actually stops between rapid gearchanges , no of course not , do i think it slows down considerably more without a bov , yes i do unless of course you shift without shutting the throttle like dragracers do

Do i think the reason BOV's are fitted is for drag racing or where only rapid changes are needed , no , the longer the throttle is closed the more important a bov becomes and thats the real point , when driving normally on the road or racing on a circuit the throttle is closed for a lot longer periods especially where engine braking is concerned

Of course a jet engine has a great deal more mass and inertia and is a slightly different beast its like a series of turbochargers

[MR Y]

Originally Posted by Richf

add me to your ignore list , you are going on mine

wheres the fun in that? nothing like a heated debate

[Squeak]

Just to spice things up a little I found this

I know some people who always think they're right. And they're not content in simply believing they are the ultimate authority on any topic you might care to bring up. They have to point out how you're wrong about it. I've often wondered why they feel it's necessary to do this. Why can't they simply bask in the personal knowledge that they know the answer without trying to prove that you're wrong?

It's interesting to watch the dynamics at play when two characters who are both like this get together. Talk about the irresistible force meeting the immovable object! Usually, they can't be friends, at least for very long. It's just too hard to relate to someone who won't let you prove him wrong because he's too busy trying to prove you're wrong.

I usually interact with these individuals by simply not responding to their challenges. If they have a need to be right, I let them be right. Frankly, I don't give a hoot, and over time I've learned that it's difficult to convince someone like this that they should check their facts or re-examine their argument no matter how sincerely you try. They're just too busy advocating their views to listen to you.

The unfortunate thing in all this is that these people drive potential friends away. No one wants to be around them, and most of the time they don't have a clue as to why. I, for one, don't believe it's very likely that anything you might say will change their behavior, so if you like them despite their need to be right, you just have to let them be right. And if they're wrong, well, you just have to let them be right. A cop-out perhaps, but heck, it works for me.

[Bubble]

Did you copy and paste that?

[Lambo Door Kits Ltd.]

Very true, very true, met plenty of people like that. I just say what I know and if I`m proved wrong then I`ll accept that no problem. After all we can`t know everything and I only know what I know from 12 years of experience. At the end of the day it`s good to discuss things and banter ideas about, but not good to go for someones jugular.

The point is, Nissan decided that the best piece of equipment for a Standard turbo was a recirculatory B.O.V otherwise it would have been fitted with a vent to atmoshire type. That suggests that it doesn`t have to much effect on the Turbo, but helps a little. If you up the power then I can see the benefits in fitting one. Otherwise why would they be invented in the first place. I wouldn`t personally fit one to a standard car as I know they are a pain in the arse to set up and not worth the hastle. The noise would soon get irratating also. Just my opinion. Shoot me down with flames and don`t piss on me to put me out lol.

[ISJ]

Originally Posted by Richf

Do i think the turbine actually stops between rapid gearchanges , no of course not ,

Ahh, right, ok, so your saying that the turbine doesn't actually stall now? Seems a slight contradiction to the initial explanation & your Post #13. See below, you even underlined the "bring to a standstill" bit.

Originally Posted by Richf

If boost pushes back against a compressor wheel it will slow or stop or STALL ie bring to a standstill which is the correct use of the word stall

stall definition |Dictionary.com

It's a common misconception of what "happens." It is far easier for people to imagine the turbine to stop/start than the airflow passing over the blades, transitioning from laminar flow to turbulent.

Originally Posted by Richf

Of course a jet engine has a great deal more mass and inertia and is a slightly different beast its like a series of turbochargers

Yes and no. The air passing over the turbine blades can stall on any turbine, no matter what size or shape. It all depends on circumstances and loads.

Originally Posted by Richf

Oh well if i'm patronising then add me to your ignore list , you are going on mine

Touchy! Am I on yet? I hope so, then you won't see this........

[Squeak]