To blow-off or not to blow-off ?????????

[Fats]

Had a curry earlier getting a bit worried :flamed . On a serious note just finished my project, Fitted Garrett T04S, 1600 secondarys, blitz front mount etc....... I had the turbo rebuilt by ATS turbo\'s before fitting, just wondering whether to fit a blow off valve or not, I\'ll only be running 0.8-1.0 of boost so not overkill, There\'s mixed opinions on this but surley the turbo would be fine at the low boost level?

Cheers

[Initial-D]

I\'m also tempted to loose the dump valve, over on the GTR forums there was a similar thread and it was said that its fine to run without and that there were far too many other things that could fail before the turbo due to stalling. Personally I much prefer turbo stalling/flutter to a dump valve any day.

[Fats]

Agree 100%, I haven\'t had mine on the road yet but it\'s flutterin a gud un on the spot with a good rev, can\'t wait to see what it sounds like on the road!!!!!. It\'s the first car I\'ve driven with an external wastegate, think it\'s going to be a bit anti social... but who give\'s a ****!

[Carl]

Simple really,
If there was no need to have one then Manufacturers would not fit them as standard to production cars cos it would save them money.
I think that your investment should be looked after by having one as it does take the strain off the compressor when  throttle is shut.
If you want it to be quieter then plumb it back into the system preturbo.
Regards
Carl

[BlitzBoy]

oh no , not this old chestnust again :rollin
I vote no to a dump valve as it hurts performance, do a search on previous threads on the fors and against dump valves

[rico2k_uk]

alot of manufaturers didnt actually fit any as standard originally. then they started fitting recirc valves to quiet things down as people want cars to be quiet. you wont have any problems - was running without one on my skyline for a while and no probs at all. infact the turbo was running better as wasnt loosing lots of compressed air! just dont do it if you have a roller-bearing turbo.

[BlitzBoy]

Been running without a dump valve for the last two years on a roller bearing turbo no problem at all with it

[12A]

oh no , not this old chestnust again :rollin
I vote no to a dump valve as it hurts performance, do a search on previous threads on the fors and against dump valves

Hurts performance? Why do all the 8 sec car downunder use them then:Hammer

[rico2k_uk]

it does hurt performance, basically becasue you are blasting all the compressed air out of the system into the atmosphere - takes some power to create it using the turbos!

[BlitzBoy]

I seem to remember a huge thread fors and against dump valves on Ausrotary, also ive seen quite a few drag cars run without as well and they run 6s and 7s,8s, so this argument will never go away

Rally cars run without them as they do many gear changes so time iwould be lost repressurising the intercooler pipes at every gear change if they did run them.

[BlitzBoy]

Hurts performance? Why do all the 8 sec car downunder use them then:Hammer

oooohhh what we have here yes its a 7 second Supra, whats with wrong with this picture?? thats right NO dump valve!

[rico2k_uk]

lol! there is no winning, you can run with and without.. wihtout sounds great!

[BlitzBoy]

for every Drag car that has a dump valve I can show you another that does not have one.

oooooh what we have here another 6 second drag car oooh and guess what NO dump valve

[Prof]

oooohhh what we have here yes its a 7 second Supra, whats with wrong with this picture?? thats right NO dump valve!

...but I bet that turbo has a ported shroud, which is a little like having a dump valve in any case.
 
Dump valve only releases the excess pressure between throttle and turbo compressor wheel, which prevents slowing down or stalling of the turbine.  Without one the compressor wheel loses a lot of speed, so is no longer \'on boost\'.
 
As far as performance goes - it\'s the difference between spinning up the turbine again after it\'s been slowed/stalled or re pressurizing the pipework between throttle and compressor - there probably isn\'t a lot in it - but depends on pipe lengths and diameters, volume of air in the intercooler and so on.
 
Certainly for the smaller turbo\'s, the dump valve should be used as you will be causing bearing wear every time you \'let off\' and the turbo won\'t last anywhere near as long.   Larger turbo\'s can probably take the punishment.
 
I think someone should do some tests on various factors with this - and post up the results so that we all know what the pros and cons are.

[12A]

But are they missing because they "hurt performance"? or because they use extremely short inlet tracts. 468bhp and only 11.39 - i guess you know it all :rolleyes: