Forums Forums Enthusiast Forums A - Z Autowirral BOV's/DV's - Do you REALLY need one?

On a different board im in there's been quite a large discussion on the necessity of blow off valves and dump valves. I've heard before that you need them to prolong turbo life etc, but if thats the case then why dont cars come with them as standard? Some come with recirculationg ones but is that just to keep the noise of the turbo (wastegate flutter/chatter/whatever) down ?

So basically, will it harm your car by not using a BOV or DV?

Dump valves release the pressure on the turbo when you shut the throttle butterfly. As mentioned above.

This has its advantage and disadvantage.

Advantage is that when you let off, the valve opens due to the pressure change and dumps the air releiving the pressure from the turbo, disadvantage is that its let all the air from the pipes go, and this will need filling next time you get on the throttle making more lag between gears.

The reason you dont hear then on Rally cars is - the car is quicker without a dump valve, as lag is less between gears, and even with the pressure on the turbo, they are still tough enought to last a rally without letting go - they are after the performance rather than making the turbo last. Antilag also doesnt work as well with a DV as you are getting rid of air in the system.

Cars that have them fitted have recirc valves to keep noise down, and as it recircs the air keeps it all in the intake system which is better for economy and emmissions.

The cars that dont have them either dont produce enough boost in std trim to really harm the turbo and its more cost effective to not fit a recirc DV and live with a few 1000miles life off the turbo.

So would you recommend running with one and prolonging the life of the turbo (if they actually make a difference?) or run without one and get less lag between gears and that lovely noise from the turbo

I killed a 2 T3s on my S13 (before going to a t34) within 8k miles due to not using a DV (Main oil seal went twice) - though it was pushing 20psi on a T3.

Each recon was circa £300, so £300 every 4000ish miles - depends how much value you put on the added performance and noise. For me it was well worth it

So it makes that much of a difference? What boost were you running and im guessing with your driving stu you were boosting quite a lot

I would have thought that running without a BOV would drastically shorten the lifespan of the turbo ??

Interesting topic, i know my own knowledge on BOV's and understand the Pro's & Con's of running with a BOV.

My Lag is so very slight expecially if your quick on the up-shift and the turbo keeps spinning up at stupid RPM therefore when i get back on the gas the turbo is already spinning its ass off and builds your boost up with minimal lag.

Surley if my turbo is spinning at 10,000 rpm and i close the throttle on it then the pressure build up will be quite severe and simply start blowing hoses wide open and putting the delicate turbo bearings under allot of pressure ??

Never ran a car without a BOV when its designed to have one

More info Chewwy mate.... and anyone else with good knowledge on this.

Lol, on full chat the turbo is spinning at 100000rpm on some turbos, up to 250000rpm on others

The momentum in the turbo keeps it spinning when you you shut the throttle and still pushes the air at the closed throttle housing for a split second - a DV gets rid of this, otherwise if has to go back through the turbo, causing the chatter noise and putting a lot of load on the turbo.

The DV empties the intake pipes of most of the air which must be refilled by the turbo when you go back on the throttle before you can make decent boost pressure again.

Without the DV, there is still some pressure in the pipes which makes the time to fill them again less - and less lag.

Best compramise is an adjustable BOV, which gets rid of a limited amount of air, taking some strain off the turbo, but leaving some air in the pipes.

Scoobys have quite low lag as the IC and pipe work is close to the turbo and inlet, and the distance the air needs to travel to get to the engine is quite minimal.

Thats about as much as i know, i also though it'd be good to have a technical topic on the board too

So basically its mainly stressing the oil seals on the turbo? and not worth the hasstle of not running one by the sound of it!

Another thing an atmospheric BOV does is run the car rich when it releases the air. As all the air in the intake has passed the AFM, the car thinks it has "x" amount of air in the system, you get rid of it and the ECU doesnt know, and is still putting fuel in for "x" amount of air when you have just vented it to atmos via the DV and it runs rich - though only until the engine has cought back up.

He drives a cherade turbo btw**

Firstly, I find it had to see how a std turbo with a 270 degree bearing would last for 5 years at 29psi with or without a BOV - that is some serious punishment

Secondly, the GTTi's use tiny turbos, meaning the volume (not pressure) of air is very small, meaning there is less air coming back at the turbo when the throttle shuts, and the compressor housing blades are also very small and provide less surface area for the air to back up against causing less stress on the bearings. Therefore the smaller the turbo, the less damage it can physically cause.

So basically he's chatting shit?

Is that a plenum chamber??

Intersting........