single turbos question

[Jake]

I get the impression from reading around about this that it\'s \'one of those issues\' like the which oil question.  Some people swear by them and others completely disagree.  Compressor surge definitely sounds better though IMO

[Jake]

If I ever get a single I definitely won\'t be running a BOV, I\'ve never heard anything to convince me they are needed.  Plus compressor surge is just the best sound and if it\'s good enough for WRC it\'s good enough for me.

[monkey-fd3s]

There\'s no need to run one on a drag car because longevity is not an issue and the gear change from a glide or lenco is so quick you\'d loose more than you gain.  I don\'t have enough experience of circuit cars to say if they are used on them or not.

Now there\'s probably a reason most manufactuers, subaru, mitsubishi, etc fit a recirc to their standard cars... I\'m sure they don\'t do it for no reason or because it\'s fun to...

EXACTLY Jake!!!! Between Gear changes your turbo doesnt stall or stop spinning it still rotates in the same direction at hundreds of rpm

Hmmm ok so your idea is that all the compressed air seeps out of the tiny gaps between the blades of the compressor in the turbine housing during which time the turbo is still spinning and making boost? And compressor don\'t stall...


If you\'d studied some engineering principals you\'d know that there are two general types of compressor stall.

One type of stall is know as "axis-symmetric stall", which is an expulsion of air out an intake when the compressor\'s isn\'t able to maintain pressure on the combustion chamber.

Rotational stall occurs when the air flow disruption causes pockets of air to rotate in the compressor without moving along the axis.

The general cause of compressor stall is a sudden change in the pressure between the intake and combustion areas.

[davegttph1]

As Monkey says the gear changes are so quick and theyre doing full throttle changes so it doesnt effect it in drag and rallies, but in reality me and you take our foot off the accelerator whilst changing gears. When the throttle closes and the turbo is now trying to push alot of air though a closed door its going nowhere and will cause long term problems IMO.... Doesnt take a genious to work out.

[antnicuk]

here is another angle for you

Blitz is right in the fact that you create more spool up time with a BOV as you have to recharge the inlet track and if you are a racing and 100th of a second counts and you can bolt a new turbo on it when you get to the pits then dont run one.

But, if its your road car and you have just spent £3000 on your shiney turbo that you are running 1.4 through then every day use a BOV will put less stress on your turbo and either help it last longer or maybe prevent your shaft from snapping (which is quite common)

You could always put one on and just pull the vacume line from it when you get to the Pod.  

There is a reason most stock turbo cars run BOVs,  and that is running 7 - 10 psi,  and although most of our turbos are stronger than the stock one, we are running 2 or 3 times the boost.

It is just down to choice at the end of the day....

[BlitzBoy]

Now there\'s probably a reason most manufactuers, subaru, mitsubishi, etc fit a recirc to their standard cars... I\'m sure they don\'t do it for no reason or because it\'s fun to...

A Recirc valve is different to a BOV. Its metered air thats already measured by the ECU therefore is recirculated to keep mixture correct.

Sooo why dont WRC fit BOVs then?? longevity is the name of the game in Rallies were reliablilty iv VERY important. I mean its not an expensive bit of equipment so why dont they fit them. To me BOVs are just noise makers.

Also I did NOT  say ALL compressed air seeps out of the housing I said execess air, the intercooler tubes and intercooler remain partly pressurised when not running a bov you dont lose all the compressed air

[Jake]

When WRC cars do rallies they do have to drive between stages don\'t they under their own steam?  I\'m sure under these circumstances they drive much more like you and me and if a BOV would really aid reliability at all surely they would run one?

[antnicuk]

it could go on like this for weeks

a rally car still only does hundreds of miles maybe a thousand or so before getting checked/rebuilt etc.  

a recirculating valve does the same job as a BOV and for the same reason, it just recirculates it for the reason you gave......... an FD doesnt meter the air.

Also, the pressure will drop in the whole system.  it may not loose all pressure but the pressure is almost the same through the whole system,  it cant drop pressure in the turbo side but not the engine side.....

[Jake]

I know that rally cars are checked and rebuilt very regularly but surely if running a BOV decreased the chances of the turbo destroying itself out on a stage then surely they would run one wouldn\'t they?  I\'m just really trying to understand this as it doesn\'t seem to add up.  Race cars are always striving for reliability as a fast car is useless if I can\'t go a race distance, if a BOV gave that then why wouldn\'t they run with them?

[monkey-fd3s]

If reliabillity was really an paramount issue on rally cars they\'d never run an anti-lag map.  In reality it takes a lot more than a whole rally inc driving between stages to kill things like turbos.

Rally/drag teams can afford to have a shorter turbo/engine life cycle because they are able to replace them.  For us on the street it make sense to protect your £2000 turbo or £4000 engine as best you can.  It\'s not an essential item, but perhaps a sensible one, shown by the installation of these devices on OEM turbo engines.

On the drag car I crew for we strip the engine down at a minimum every half season, we replace anything that\'s worn, I\'m not sure people on thes street can afford that.  

Another example is running no air filter, it seems to be popular yet slightly retarded trend to have chicken mesh over the intake.  We tried an open intake and after one weekend racing had to replace the cylinder liners and pistons on the drag car because of the garbage that was getting sucked in.  Again you can do it but why run the risk...

[Jake]

Thanks, that does make more sense than anything I\'ve heard before on this issue about why they are needed.  So it\'s basically a risk versus reward kind of scenario.

[monkey-fd3s]

Yup that\'s it in a nutshell