Phlukey Posted May 3, 2015 Share Posted May 3, 2015 I'm sure this has probably been asked many times before, but here goes....... How damaging is compressor stall (referred to incorrectly as waste gate chatter, BOV chatter or compressor surge by many) to a modern large BB turbo from a reputable manufacturer? I ask because I love the 'chattering' noise created when you let off the throttle, but when you think about what's actually causing the noise - charge air 'bouncing' back off of the closed throttle butterfly plate, if the BOV can't then flow enough charge air to atomsphere quick enough, it then backs up, stalling the compressor wheel before reverse flowing out of the intake. That surely can't be good for a turbo, as there must be large levels of mechanical stress involved (to bearings, shaft and compressor wheel / blades)? Question is, are newer aftermarket turbos strong enough now to cope easily with these stresses and thus make their consideration irrelevant? Quote Link to comment Share on other sites More sharing options...
add heywood Posted May 3, 2015 Share Posted May 3, 2015 Ooo, worms and can springs to mind lol. I think the thought is the turbo will die of something else far before the stall kills it. I have never run a bov on the supra (or rx7) and the turbo is fine... Quote Link to comment Share on other sites More sharing options...
Tricky-Ricky Posted May 3, 2015 Share Posted May 3, 2015 I have never seen a turbo killed by not running a BOV. Quote Link to comment Share on other sites More sharing options...
TheTurtleshead Posted May 3, 2015 Share Posted May 3, 2015 If you run with no bov, my concern would be splitting the IC or popping pipes off all the time. Quote Link to comment Share on other sites More sharing options...
Wez Posted May 3, 2015 Share Posted May 3, 2015 Compressor surge and stall are different Surge is when the turbo is spun up too quickly and chokes, normally from an incorrectly sized turbo, being too small etc. Compressor stall is the release of pressure back through the turbo during lift off etc, normally fluttery in sound, can be heard on Motorsport turbo engines, blow / dump valves dump this to atmos and recirc dump back to inlet. Recirc are installed by car manufactures purely to silence the process. I've seen no evidence to backup any claims of decrease in spool between gear change or increased longevity of the turbo. Quote Link to comment Share on other sites More sharing options...
Phlukey Posted May 3, 2015 Author Share Posted May 3, 2015 (edited) Thanks for the responses guys. I do already understand the differences between compressor surge and stall. My question here is not aimed at the effectiveness of a BOV in protecting against compressor stall (I know they can help prevent compressor stall along with anti surge compressor housings), but at how much harm compressor stall can actually do to the life of the turbo. I know I can probably prevent compressor stall altogether on my car if I want to, as I have 2 large, high flowing 50mm TS Raceport BOVs fitted currently, but I'm wondering if I actually NEED / HAVE to if the effects of compressor stall aren't actually that detrimental to the life of the turbo, as I actually like the chattering noise it creates. I just don't want to end up sacrificing reliability for a noise I like. A recent ride in John Baileys car has not helped with this dilemma either. The noise in his car sounded awesome! Edited May 3, 2015 by Phlukey (see edit history) Quote Link to comment Share on other sites More sharing options...
supra matt Posted May 3, 2015 Share Posted May 3, 2015 Thanks for the responses guys. I do already understand the differences between compressor surge and stall. My question here is not aimed at the effectiveness of a BOV in protecting against compressor stall (I know they can help prevent compressor stall along with anti surge compressor housings), but at how much harm compressor stall can actually do to the life of the turbo. I know I can probably prevent compressor stall altogether on my car if I want to, as I have 2 large, high flowing 50mm TS Raceport BOVs fitted currently, but I'm wondering if I actually NEED / HAVE to if the effects of compressor stall aren't actually that detrimental to the life of the turbo, as I actually like the chattering noise it creates. I just don't want to end up sacrificing reliability for a noise I like. A recent ride in John Baileys car has not helped with this dilemma either. The noise in his car sounded awesome! Im the same as you mate and love the noise so am running no bov it has Been covered before and should not prove a problem, Quote Link to comment Share on other sites More sharing options...
Swampy442 Posted May 3, 2015 Share Posted May 3, 2015 if the BOV can't then flow enough charge air to atomsphere quick enough A BOV will always flow enough air, thats its job Compressor surge and stall are different Actually, if you want to get technical, stall and surge go hand in hand, surge is a product of stall. Whats the worst that can happen, your turbo slows down quicker that it normally would once the pressure is released to atmosphere, you have an intake system full of pressurised air ready to go into the engine... To answer your question though, a certian Mr Chris Wilson of this parish doesn't run BOVs on his race Skyline, no bigger recommendation in my eyes. Quote Link to comment Share on other sites More sharing options...
Phlukey Posted May 4, 2015 Author Share Posted May 4, 2015 (edited) A BOV will always flow enough air, thats its job I'm not so sure that is true. I may be wrong, but from what I understand any BOV has a limit to the amount of charge air it can flow to atmosphere in a given time period. If the turbo being used can overcome the BOVs maximum flow capacity to atmosphere, then a certain amount of charge air will still back up (all be it less) and could cause compressor stall. Hence why a lot of high HP builds go with a twin BOV setup to increase BOV flow capacity. For example the supra in this video is running one HKS SSQV BOV, but you can still clearly hear the chattering noise of compressor stall. Surely this is because the turbo is overcoming the BOVs ability to flow enough charge air to atmosphere, resulting in it backing up and causing compressor stall? Please correct me if I'm wrong though, because I don't claim to be any Chris Wilson expert on the subject, just someone trying to learn and understand. Interesting what you say about Chris's choice not to run a BOV on his Skyline. I doubt he'd do this if he thought it was detrimental to the turbo, so cheers for that info Edited May 4, 2015 by Phlukey (see edit history) Quote Link to comment Share on other sites More sharing options...
Scott Posted May 4, 2015 Share Posted May 4, 2015 A BOV will always flow enough air, thats its job I assume there's a punchline here? A BOV is effectively a wastegate for the pressure side. Too small a wastegate = overboost. Ditto with the BOV. Quote Link to comment Share on other sites More sharing options...
Phlukey Posted May 4, 2015 Author Share Posted May 4, 2015 I assume there's a punchline here? A BOV is effectively a wastegate for the pressure side. Too small a wastegate = overboost. Ditto with the BOV. Exactly that Scott....... I wish I could just have explained what I was trying to say that easily lol Quote Link to comment Share on other sites More sharing options...
Scott Posted May 4, 2015 Share Posted May 4, 2015 Occams Razor Quote Link to comment Share on other sites More sharing options...
Phlukey Posted May 4, 2015 Author Share Posted May 4, 2015 Occams Razor True indeed....... so in short I ramble too much Quote Link to comment Share on other sites More sharing options...
Chris Wilson Posted May 4, 2015 Share Posted May 4, 2015 REcirculation valves are fitted by manufacturers to STOP the noise of compressor stall. That's ALL they do. They don't aid turbo life, and they add slightly to lag. No serious professional race engine has one, not even world sports prototype endurance race engines, If they aided turbo longevity or reduced lag they would have one of these tuppence ha'penny gizmos! Quote Link to comment Share on other sites More sharing options...
Phlukey Posted May 4, 2015 Author Share Posted May 4, 2015 Good point Chris, guess I should just stop worrying about it then and enjoy the noise Quote Link to comment Share on other sites More sharing options...
mellonman Posted May 4, 2015 Share Posted May 4, 2015 I have a adjustable bov, so set it to a nice balance of atmosphere vs turbo stall Quote Link to comment Share on other sites More sharing options...
V8KILR Posted May 5, 2015 Share Posted May 5, 2015 (edited) REcirculation valves are fitted by manufacturers to STOP the noise of compressor stall. That's ALL they do. They don't aid turbo life, and they add slightly to lag. No serious professional race engine has one, not even world sports prototype endurance race engines, If they aided turbo longevity or reduced lag they would have one of these tuppence ha'penny gizmos! A BOV does reduce the slow down of the turbo during gear changes and does reduce turbo lag on gear changes. This is based on personal experience. A long time ago when I upgraded to USA spec turbos, I had to add a second JDM BOV (20mm) to improve how quickly the boost recovered on gear changes and that worked great. After I changed back to the Getrag a few months ago, I then raced at the drags (currently running a 65mm MasterPower turbo) and realized my twin 30mm HKS SSQV BOVs (probably fake ones) were no longer working. There was no noise on gear changes under boost and the boost was incredibly slow to recover when changing in to the next gear. I have removed both the HKS BOVs and added a 50mm Turbosmart raceport BOV (for more flow than both HKS BOVs combined), which I'm sure will fix the issue. I'm racing again in 2 weeks, so I will know for sure then. In a race car, you could set it up so you didn't lift on the gear change (flat shifting) or you could use anti-lag on the gear change to keep the boost up. Both these would be better than using a BOV, but it is hard on the car but for a race car that doesn't matter. I didn't need them when the Supra was auto of course as no lifting on gear changes. On a manual street car it's optional, but I did like the sound that the HKS SSQV made on gear changes. Edited May 5, 2015 by V8KILR (see edit history) Quote Link to comment Share on other sites More sharing options...
V8KILR Posted May 18, 2015 Share Posted May 18, 2015 I can confirm that the new 50mm Turbosmart raceport BOV fixed the huge delay in boost recovery during gear changes. I tested this at the Powercruise #55 meet yesterday in Hampton Downs. It worked so well in fact, that I won the Off Street drags event. Quote Link to comment Share on other sites More sharing options...
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