single turbos question

[jurgen]

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.

[davegttph1]

its a choice. dont need one but can have one if you want.

[jurgen]

so the wastegate on its own is enough to vent the pressure  :Thumbs-up

[richard cash]

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

[jurgen]

the reason being was i had a t88 supra with wastegate only and i was told by specialists it also needed a dump valve

[BlitzBoy]

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

[davegttph1]

the 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

[Mave]

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

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!

[antnicuk]

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.

[BlitzBoy]

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

[McCARTHY]

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.

[monkey-fd3s]

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

[BlitzBoy]

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

[Jake]

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?

[BlitzBoy]

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