Hi,
I was wondering what the flutter noise was that this FD makes (follow video link.)
http://www.youtube.com/watch?v=tfujAW4cwWc&feature=related
It sounds pretty cool to me, is it a BOV or wastegate or just the large single turbo?
I\'m new to all this btw so go easy.... ;)
Compressor surge/wastegate chatter and a load of other names its the noise of the pressurised air passing back over your turbine blades if you blank off and remove the bov, very common on single turbo cars but works the same on twins. I ran my twins like that for a long time until the flutter got tiresome.
If you like the flutter noise pull off and blank the small vac pipe to your bov and give it a try if not its easily put back on.
Now for the inevitable for and against posts for removing the bov
ok thanks mate, so what would you say are the pro\'s and con\'s?
pros = funky noise,
cons = depending who you speak to - risk of lunching turbos.
compressor surge is a phenomenon (as Neil says above) where you get a flow reversal of air over the blades.
Basically, it happens when at any given flowrate, the compressor can no longer impart the necessary pressure rise to the gas (in this case air) to allow it to move through the downstream part of the system (in this case the intercooler / inlet manifold, etc). When this happens, the higher downstream pressure overcomes the lower upstream pressure (in this case atmospheric as your air filters are open-to-atmosphere) and the gas forces it\'s way back across the blades, attempting to spin them the wrong way.
If you imagine that a compressor impeller is turning at ~100000rpm and all of a sudden it\'s getting forced into reverse, you can see the stresses it is put under. And when you further consider that this condition can reverse again (ie, force air the RIGHT way again) many times in a very short space of time, you can see where damage can occur.
I\'ve seen massive, massive, industrial compressors hit the surge line and can tell you it\'ll wake you up. Think of the forces needed to vibrate a 30tonne piece of equipment clean off it\'s foundations. That\'s why these machines, costing upto £10m each, have ridiculously specc\'ed anti-surge systems (essentially big recirculating dump valves) - that can easily cost upto £500k a pop.
HTH
graeme
so is there a safer way of achieving the same results without the chance of damage?
I\'m guessing the same result is compression surge so thats probably a stupid question...
Buy a turbo with a ported shroud
Quote from: adamrogers3091;712633http://www.youtube.com/watch?v=tfujAW4cwWc&feature=related
Ahhh, Kash\'s car back when it had a BGW....and working brakelights :rollin
that noise is compressor stall...
many people run their turbos without bovs with no problems but the pros/cons are massively debated. some say the bov helps spool, some say no bov increases response etc etc.
Import Tuner did do back to back dyno tests with a recirc versus atmosphere bov and found that the recirculating system was mildly better for spool, so much so that you\'d never realise it on the road.
Thanks Jackaleks, so what your saying is either way there wasn\'t much difference in the dyno test.
I understand compression stall is unhealthy at high boost levels (bigger surge through the turbo) but not to bad at low boost and revs...?
If you\'re on stock twins and remove the recirc dump valve, btw, it won\'t make a really cool noise like Kash\'s car in that vid, which has a big single conversion. Stock twins with no dump valve just sound like a really big turkey being flushed down a really small toilet :rollin According to SiH, this is also called "the Zoidberg"...watch to the end of this to understand http://www.youtube.com/watch?v=P_WI0VI7aIw
Quote from: adamrogers3091;712819Thanks Jackaleks, so what your saying is either way there wasn\'t much difference in the dyno test.
I understand compression stall is unhealthy at high boost levels (bigger surge through the turbo) but not to bad at low boost and revs...?
here\'s the Import Tuner article (http://www.importtuner.com/tech/impp_0903_2008_mitsubishi_lancer_ralliart_fact_or_fiction/index.html#), however, "2nr" is the American equivalent of Redline so take it with a grain of salt. if the turbo goes past the surge line whilst on boost - i.e. throttle open and exhaust going through turbine - then it\'s going to cause damage. doesn\'t really matter if the throttle is closed though. tbh, in their article both cases showed the boost dropping below 5psi in less than half a second so you\'ll probably not notice the difference in real world driving.
Quote from: Nik da Greek;712828Stock twins with no dump valve just sound like a really big turkey being flushed down a really small toilet :rollin According to SiH, this is also called "the Zoidberg"...watch to the end of this to understand http://www.youtube.com/watch?v=P_WI0VI7aIw
sounds better than my R2D2, which sounds like a muppet farting!
Quote from: Nik da Greek;712828If you\'re on stock twins and remove the recirc dump valve, btw, it won\'t make a really cool noise like Kash\'s car in that vid, which has a big single conversion. Stock twins with no dump valve just sound like a really big turkey being flushed down a really small toilet :rollin According to SiH, this is also called "the Zoidberg"...watch to the end of this to understand http://www.youtube.com/watch?v=P_WI0VI7aIw
Thats so funnny!! I certainly don\'t want the Ziodberb!! lol :Giggle
Thanks for all your help guys its good to know the helps available!!
Quote from: adamrogers3091;712819Thanks Jackaleks, so what your saying is either way there wasn\'t much difference in the dyno test.
I understand compression stall is unhealthy at high boost levels (bigger surge through the turbo) but not to bad at low boost and revs...?
i can only speak from experience of big turbines, although the theory is the same for turbos. To my (engineers admittedly) mind, surge is a bad thing at ANY time - in theory. But even at low boost, your turbo is still spinning >10000rpm.
But as has been said some people have no issues, some people have loads - you pays yer money and takes yer choice.
graeme