Blowoff vs dump valve

Riekert · Post by **Riekert** » Sat Sep 22, 2007 2:48 pm

Well i did a wikipedia search and it said a blowoff valve is not the same as a dump valve. But saying that, whats the best one to fit. whats the pros and cons. Because i wanted to fit a dumpvalve but now i want to know which one to fit.

Vlade · Post by **Vlade** » Sat Sep 22, 2007 2:55 pm

One that doesn't leak and one that won't seez up on you...

I got one of those HKS nockoffs does the job...

Downside on standard management... I hear some say you will get slight over fueling when it dumps and a slight decrease in fuel economy... but I can't comment I don't have std management.

Upside it sounds cool and it increases the life of the turbo also helps the spooling...

If I could afford it I would stick to a name brand, Turbosmart, HKS, Greddy... but its a bit difficult to pay R2000 for a BOV

The Calibrator · Post by **The Calibrator** » Sat Sep 22, 2007 4:00 pm

There are two different types of thses valves.
The recirculating type which is what is fitted as std to all factory turbo cars. This is the onkly type to run if your car is eqiupped with a maf sensor.

Then you have BOV or Blow Off Valves these vent to atmosphere and make that boy racer sound.
If you fit one of these to a maf equipped vehicle it richens the mixture up when cruising as you are throwing away some the air that the maf has measured.

Toby · Post by **Toby** » Sun Sep 23, 2007 9:52 pm

The way I inderstand it, the blow-off valve (BOV) refers to the valve that keeps your turbo from over-boosting. This is the one that keeps standard boost at 0.6bar, etc. (the one with the actuator arm). It's internal to some turbos, others need an external one. The SX has it internal to the turbo.

The dump valve is the one you fit onto the intake side to vent out boost when you close the throttle (lift off). Read my driving techniques article and you'll realise that boost is a terrible thing to waste...

Daniel · Post by **Daniel** » Sun Sep 23, 2007 10:30 pm

Toby wrote:The way I inderstand it, the blow-off valve (BOV) refers to the valve that keeps your turbo from over-boosting. This is the one that keeps standard boost at 0.6bar, etc. (the one with the actuator arm). It's internal to some turbos, others need an external one. The SX has it internal to the turbo.

The dump valve is the one you fit onto the intake side to vent out boost when you close the throttle (lift off). Read my driving techniques article and you'll realise that boost is a terrible thing to waste...

Actually ur confused with a wastegate Toby.

As far as im concerned a BOV and dumpvalve is the same thing just diffrent names. I prefer BOV as dumpvalve sounds danville.

veecee · Post by **veecee** » Sun Sep 23, 2007 10:40 pm

Toby wrote:The way I inderstand it, the blow-off valve (BOV) refers to the valve that keeps your turbo from over-boosting. This is the one that keeps standard boost at 0.6bar, etc. (the one with the actuator arm). It's internal to some turbos, others need an external one. The SX has it internal to the turbo.

The dump valve is the one you fit onto the intake side to vent out boost when you close the throttle (lift off). Read my driving techniques article and you'll realise that boost is a terrible thing to waste...

sorry toby - this time you are incorrect!!!

dumpvalve and blow-off valve are the same thing. its two different terms coined for the same concept. they both release pressure built up when the throttle is closed and the turbo is still compressing air. calibrator mentioned the options for where the excess air is released to (atmosphere or intake manifold), but essentially thats what they do.

the control of boost function (i.e keeping the turbo at 0.6 bar) that you mentioned is controlled by a valve of similar design but with a completely different term used to describe it. its called a wastegate, and its well known worldwide by this term. once the desired air pressure is reached on the compressor side of the turbo, the wastegate valve (which is connected in line on the exhaust side of the turbo) opens to allow the exhaust gases to bypass the exhaust wheel of the turbo and go directly out of the exhaust pipe. it essentially "wastes" those exhaust gases that would normally cause the boost to increase, by directing away from the exhaust wheel and out of the exhaust usually at the rear of the car!!!

this doesnt mean you're completely wrong though, because a wastegate is commonly found in one of two orientations. most "smaller" or OEM turbos are designed with an internal wastegate that is an integral part of the exhaust housing of the turbo. most of the "larger" or high performance turbos are designed to have a separate (and more controllable) wastegate mounted on its own perch on the exhaust manifold. these are usually much larger valves associated with high output motors, and were designed because internal wastegates couldn't be produced large enough to handle those amounts of waste generated by such motors!

kapish!!!???!!!!

veecee · Post by **veecee** » Sun Sep 23, 2007 10:42 pm

dammit daniel,

you posted 10 minutes before me because it took me 10 friggin minutes to type all that out nicely!!!

but my sentiments exactly. damn danville dumpvalves!!!

Toby · Post by **Toby** » Tue Sep 25, 2007 6:40 am

Oh hehe, ok. I always thought BOV = wastegate. My bad

Drillergy · Post by **Drillergy** » Tue Sep 25, 2007 3:53 pm

So, If I want to fit a BOV to my car SX(stock). Can I just fit it or do I need to chip it before I can fit the BOV and I dont think I want a re-circ one.

Any advise....?

What happens when you change gears and it runs rich...any disadvantages to this?

Gary57 · Post by **Gary57** » Tue Sep 25, 2007 4:06 pm

You will momentarily run rich which might leave unburt fuel entering the turbo and exploding in the exhaust housing, not very good for the turbo.

Hennie Marais · Post by **Hennie Marais** » Tue Sep 25, 2007 4:28 pm

Some people refer to the wastegate as bumpvalve, might be where the confusion lies. There's also the pop-off valve, as used on earlier racecars, it opens up when the boost are too high, it was used on indy cars to prevent overboosting and cheating.

Riekert · Post by **Riekert** » Tue Sep 25, 2007 6:36 pm

Ja i also have a std sx. Wha must i do?

The Calibrator · Post by **The Calibrator** » Tue Sep 25, 2007 10:15 pm

Fix the things that will kill you like the suspension and brakes leave the engine alone untill you will not be killed.

Gary57 · Post by **Gary57** » Wed Sep 26, 2007 8:10 am

Fix the things that will kill you like the suspension and brakes leave the engine alone untill you will not be killed.

Not a truer word spoken

Riekert · Post by **Riekert** » Wed Sep 26, 2007 10:01 am

Ok im hijacking but, Is the std brakes on the sx ok? I know the suspension isnt that good bt at the moment i dont have the cash for coilovers.