do u run blow off valves or dump valves on single turbos i have had 3 rx single turbos and all have just had wastegate, do i need a dump or blow off valve ????
i was told i do as my t88 supra didnt have one and i was recommended to get one on, so does this apply to rx7 my rx is t88 33d.
its a choice. dont need one but can have one if you want.
so the wastegate on its own is enough to vent the pressure :Thumbs-up
i think your getting confused, unless i am. heres how i understand it.
BOV- vents pressure from inlet side when throttle plate is closed to stop compressor surge (air going through turbo the wrong way)
wastegate- vents pressure on the exhaust side to control the boost flowing through the turbo and getting boost creap.
If you dont have a BOV/dump valve then you will probably get the rally chatter from the compressor wheel. If you do get one then youll get the usual cchhhhh noise. Either way it doesnt affect the amount of boost you car will run
the reason being was i had a t88 supra with wastegate only and i was told by specialists it also needed a dump valve
I dont run one. There was a big discussion on the American forums about this with a lot of techical arguments. Performance wise u might have a slight edge by not running one as you dont have repressurise the intercooler pipes and any excess air is vented back through the turbo compressor housing giving you that rally type noise. Reliablilty by running one no air is forced back over the blades causing no damage, but that was were the arguments were raised, as they were saying how can air break hardened steel blades.
Personally I have seen no damage on my turbo, I regularly check my compressor blades. The compressor suge sound is awesome and its good enough for the WRC boys not to run one is good enough for me not to run one
Quote from: jurgenthe reason being was i had a t88 supra with wastegate only and i was told by specialists it also needed a dump valve
Thing is it didnt need a dump valve but with a larger turbo its probably best, all the dump valve will do is release the pressure and stop the turbo from stalling and you dont want a larger turbo stallings because of the revs its needs to respool back up :)
Quote from: BlitzBoyI dont run one. There was a big discussion on the American forums about this with a lot of techical arguments. Performance wise u might have a slight edge by not running one as you dont have repressurise the intercooler pipes and any excess air is vented back through the turbo compressor housing giving you that rally type noise. Reliablilty by running one no air is forced back over the blades causing no damage, but that was were the arguments were raised, as they were saying how can air break hardened steel blades.
Personally I have seen no damage on my turbo, I regularly check my compressor blades. The compressor suge sound is awesome and its good enough for the WRC boys not to run one is good enough for me not to run one
Interesting debate, I\'d always thought that the WRC boys did use BOVs just to keep the speeds up. Regarding air breaking hardened steel blades, you\'d be amazed how quickly the air can crack steel blades if it hits them at the right frequency :( That\'s why a lot of jet engines have snubbers half way up their fan blades!
i though it was to help the shaft last longer not the blades as forcing air through it the wong way basically tries to stop the shaft spinning by trying to spin the blades backwards. If you have a BOV they carry on spinning the same way.
on bush bearing turbos, the shaft is floating on layer of oil cant see how the shaft would wear more by changing rotation, Ball bearing turbos even less so.
WRC cars defo do not use BOVs. My turbo spools up pretty quick between shifts
Only by mistake when you have decided not to change gears like a granny :rollin
I have one and i\'m loosing it as they can leak, just something else that can go wrong.
A blow off valve and a dump valve are two different items and have different purposes.
A dump valve uses a vaccum sense line from the intake manfold after the throttle body. They open when the throttle closes to prevent the compressor stalling from reverse airflow, i.e. the air that cannot pass the close throttle trying the go the wrong way around the turbo. A dump valve does not offer any protection against compressor surge/overboosting.
A blow off valve is used a secondary prevention mechanism again over boost and compressor surge. A typical BOV has two ports, one from the intake manifold after the throttle body and one from the compressor outlet side, the valves are BOOST sensing and will open under certain conditions that they "believe" are detrimental, they are ususally tuneable to give the correct response.
I would suggest if you don\'t have anything investing in a BOV, perhaps one such as the Raptor or Godzilla from Turbonetics...
http://www.turboneticsinc.com/valves_bypassoverview.htm
Give me that WRC compressor surge noise over those poofy dump/bovs anytime. BOVs are for G%Ys :rollin. A lot of the Oz drag boys dont run BOVs
I remember reading a lot about this a while ago on one of the Oz forums. The argument that stuck in my mind was that race teams don\'t run BOV\'s. If there was a performance gain because it stopped the turbo stalling then surely race teams would run them? Also if there was a reliability gain then again surely race teams would run them?
EXACTLY Jake!!!! Between Gear changes your turbo doesnt stall or stop spinning it still rotates in the same direction at hundreds of rpm, the excess pressurised air just gets vented back through the compressor housing making the funky noise, your turbo is still spinning in the right direction. In fact when I switch my car off my turbo is still spinning in the right direction.
Its more of a benefit not to have one as your turbo doesnt have to repressurise your intercooler and intercooler pipes which would be lost via a bov
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
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.
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...
QuoteEXACTLY 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.
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. :)
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....
Quote from: monkey-fd3sNow 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
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?
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.....
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?
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...
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.
Yup that\'s it in a nutshell :)