BOV or no BOV?

[Roundabout-Now]

Ok, so I\'ve just spent quite a while reading all about BOV\'s on the aussie rotary forum and the general consensus, from what I could see, is that you don\'t need one?

The Pink Panther is in at WGT at the moment for a few jobs, one of which was to fit a BOV as recommended by Pip as there isn\'t one on it at the moment.

What should I do? Apparently I\'ll lose the wastegate flutter if I get  BOV, but some say that a BOV will protect the turbo.

It might be irrelevant, because if Pip has finally received the part tomorrow, then it will get fitted, but at the moment I\'m toying with the idea of phoning Pip in the morning and telling him not to bother with the BOV if it hasn\'t arrived yet (been on backorder for over a week).

I\'m highly confused.:confused:

[g11ary]

a stock car has both but because of the design set up you cant here them, on my other 2 rx\'s both non standard, they both have wastegate and bov and you do get that chatter. No fear of damage or stalling the turbo\'s if you have both, if your turbo is weak it blow it. IMHO just my 2p worth.

[clive]

I don\'t run a BOV and love the chatter !!!

However it depends what Turbo you run, mine is a Garrett GT ball bearing with a strong shaft [spindle],
 
If running an older style Turbo with plain bearings and small shaft without a BOV, you risk twisting the shaft as it can\'t cope with the changes in pressure on either side of the Turbo upon lifting off the throttle.

l will however be useing a BOV from now on for Drag strip only use to try and speed up my gear changes.

l am sure people with much more knowledge than me will further this debate .

[Roundabout-Now]

Taking a worst case scenario, if the turbo goes is it usually just the turbo that needs replacing, or will bits make their way through the IC and wreck the engine?

[g11ary]

forget the ic, more likely to get parts into the engine and goodbye.

[20B_boy]

If the shaft fails I\'m not sure how yer motor is going to digest bits of your turbo...?

[Roundabout-Now]

I just wasn\'t sure if the IC would just block up with most of the bits - after all, the passages aren\'t too big through the IC.

[richrx]

obviously safety first, if it was recomended to get one then go for it.

out of the 2 choices then wastegate EVERY time:D

[igy]

Ok, no BOV shortens the life of the turbo.  In high boost applications no BOV can cause immediate damage by twisting the turbine shaft.  Every cool little chatter is a violent stoping and restarting of the turbo and a load and unload of the thrust bearing.  I have seen plain bearing turbos go bad in a month of highboost with no BOV and ballbearing turbos go bad in 6 months.  The bad thing about blowing a turbo this way is that they usually don\'t smoke until after the compressor wheel is machined 2mm smaller from contacting the compressor housing.

[Roundabout-Now]

To quote a few bits off the Aussie forum that got me thinking...

Rice Racing -

To put some numbers to it, even if you were making 1000bhp worth of air flow this would result in a massive amount of 3kg or there abouts of air weight acting against the impellor trying to escape out back past the compressor wheel in one second (if it could maintain turbine speed, which it does not!) so this peak load of 3kg is far less after 1 second in a 1000bhp application! Aluminium is pretty strong last time I looked, you could apply over 50kg or more to the tips before you would bend them and this would have to be a very very big load or force, such as waht is generated via a backfire to casue such damage.

You would never generate enough force to casue damage in a closed throttle situation. And you could not overspeed either as the throttle is shut too, some clowns go on about the "stress" on the shaft again BS, the turbine does not speed up in stages, it is slowing down in stages as soon as the throttle is shut, untill it reaches a speed that the compressor will not open the WG on a trailing throttle, it is very very simple stuff and it is easy to see that you have been sold a lie by people who realy have no idea what they are talking about in regards to what merits their "performance products" I would go as far as saying the potential failure of a BOV will at least casue you a performance loss and at worst cost you a turbo failure due to overspeeding

Examples of cars not running BOVs (all from the aussie forums again)...

One example of F1 cars from 1986 running at Monza G.Berger was pulling 4.5bar gauge pressure that is 65+psi again no BOV. No special compressor wheel materials either mind you or turbo design !

Tractor pulling machines running three staged turbos in a row pull up to 250psi boost pressure in some examples, guess what they don\'t use BOV\'s either and all on old tech turbo\'s.

Audi Motorsport did a world record 24hr speed trial in Italy in 1988 in a road car equiped with a S1 Quattro motor (fitted with a KKK27 turbo no BOV running 2.5bar boost) it averaged well over 320kph for the 24hrs and covered over 7000km. ( It was lifting off a few times during the lap for corners on the speed bowl slowing from almost 400kph!)

many Many 24 Le Mans races have be won dating back from Renault in 1978 (first turbo car to win it) running 28psi all day and night! to Porsche 962 and almost every car in between...... all of which ran NO BOV, so I would say reliabilty is not a problem  

Remember these guys are on full boost for 24hrs! or over 5500km of racing ! that is more than ANY drag or road car would do in 20 life times  @ that load level, to say that the turbos are un reliable is complete BS  We are not talking high tech either a majority in the early days up to 1987 ot there abouts are all plain bearing truck derived units, same as what a majority of us run today  

Every International Group C sports car to 1991 NO BOV
Every F1 car from 1979 to 1988 NO BOV
Every Indy car from 1970 to NOW NO BOV
DJR Group A Sierra till its last races NO BOV

You want a current example from Japan (the home of the BOV), find a down load of Rod Millens Toyota Tacoma truck (runs 1000bhp 4 cyl single turbo) and it runs NO BOV, turbo flutter in all its glory  



These are all quotes from other people, but it makes you think, doesn\'t it.

[PGiljevic]

That\'s right its not needed :flamed

[Prof]

I wonder about the wisdom of comparing race engines which are probably well built and maintained with road going cars...
 
I would also say that a 24 hour race - yes there will be lift of events, isn\'t the same as daily driving - where the stop start nature of the driving puts more frequent although lesser loads on the whole car.  The average driver is not going to be gear changing as fluidly as a race driver, so the dump events will be more prolonged and more frequent.
 
It may be that the bov/recirc (car manufacturers go for recirc more often than not) has more to do with emissions / noises / fuel economy rather than mechanical reliability.
 
Just some thoughts...

[BlitzBoy]

wow Rice talk about bringing a thread back from the dead LOL :rollin

6 years old was the last post before yours hahaha

PS I dont run a BOV for the last 3 years

[neil_jdmr]

I didnt run a bov on the stock twins for nearly 2 years at 0.9bar and still on the same set boosting fine over 3 years on.
 
Thought i had seen this thread before lol

[Grant Monkhouse]

If people are worried about using or not using a bov the easiest solution would to be to use a manly sized turbo that has a ported shroud?? By manly I mean a gt40 upwards sized turbo.