Saturday , November 18 2017
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Turbo Flutters – Want a Pigeon?

You know this sound… you’ve heard it on the streets and probably wondered WTF? You know it comes from a sports car (and even buses!) but… what on earth is it?

The distinct “dose” or “pigeon” sound that flutters like “suuuuutututututututu” has many fans and many haters, it is a byproduct of turbo cars and many owners modify their cars just to get this sound.

The sound is so popular that it’s even invented one liners like “got sik flutters bro?” and “flutters get the chicks”, not to mention the majority of us making the “zzzzzzz tututututututu” sound on our own… yes I’m one of them (Jay: even my sneeze sounds like flutter).

So now that you know what sound I’m talking about and you’ve made your own attempt at the sound, let’s get down to the nitty gritty.

What is the actual flutter sound?

It’s air… lots of it being released out the air intake side of the turbo.

Why does it happen?

At the most basic level, turbo cars suck in massive amounts of air on open throttle hence the turbine sucking “zzzzzzzzZZZZ” sound. When the throttle is suddenly closed on a gear change or deceleration, the left over air that doesn’t get ingested by the engine needs to be released somewhere. That somewhere is via the Blow off valve (BOV), and in doing so can make a soft “PSSHHH” noise.
However when the BOV is removed from the equation (explained in the video and further down) and the pipes that were once connected are blocked off properly, the air has no other escape path except to travel back to where it came from… out the air intake resulting in this unique and sexy “Tutututututu” sound.

Why does it sound like there’s a pigeon stuck in the engine?

Best to check if there really are any pigeons stuck under your bonnet… but really the chopping effect of the flutter/pigeon sound – the “tu-tu-tu-tu-tu”, is actually the air bouncing between the closed throttle and spinning turbine wheel as it gets pushed out the direction of the air intake.

The slower the turbine wheel is spinning (resulting in low volumes of slow moving air in piping), the slower the chopping sound will be which results in a better and clearer flutter sound… this is experienced by releasing the throttle on light acceleration. After heavy acceleration however, the massive amounts of compressed air leftover in the intercooler piping (since it sucked in so much on open throttle) will reverse out quickly through the still spinning turbine wheel resulting in more of a whoosh sound with a slight flutter instead.

So different throttle position equals different flutter duration/rhythm.
Turbo flutters and air path

What do I need for flutters?

Besides a turbo car, you don’t really need anything. What you don’t need however, is the Blow off valve (BOV) that came fitted to your car from factory.
Manufacturers included them as a way to recirculate the surplus air mentioned above back into the engine to minimise both noise and emissions. Even though some cars do make a subtle flutter noise with the factory BOV in place (mainly Nissan engines), you’d really need to bin it in order to get some good audible flutters.

Highly desirable items that will amplify the flutter noise are an alloy/metal intake pipe and a pod filter attached to the end of it like this:
Turbo-Flutter-Airintake
Why the intake pipe? Because sounds are amplified, reverberating off a metal pipe compared to rubber or plastic which has none of those properties. And the pod filter? Well because you want the sound outlet to be exposed and not muffled in the stock airbox.

So… will sexy flutters get me the chicks?

This should be the sole deciding factor as to whether or not you go down the flutter path… no really.
Being the truth seeker that I am, I asked the opposite sex for their opinions… here are the results:

66% of the sample group thought it was cool!
33% of the sample group thought it was lame… (maybe they like N/A)

So there you have it… majority of females do think turbo flutter is cool!
So what are you waiting for? Turn your ride into a chick magnet now!

Turbo-flutters---getschicks
Chances are 2 out of 3 chicks will love your pigeon.

(Disclaimer: sample size may not be indicative for rest of the female population. Also having turbo flutter may not guarantee attracting the opposite sex. And finally making the “tututututu” noise yourself won’t get you anywhere).

Don’t full atmospheric BOV’s sound better?

Have you not learnt anything? Flutters get the chicks! “Dose” sound is better than anything else and that includes “Pisssshhhhh” and human flutters.

Are flutters damaging to the turbo and/or other engine components?

Million dollar question that has a billion shades of grey all over it. All you need to do is do a search and read the countless threads on forums that debate over this question to realise there is no black or white answer. It doesn’t help either that top tuner cars like the HKS S15 drift car or Mines R34 GTR run no BOV while some rally cars do.

Whilst running no BOV to achieve flutter may put slightly more wear and tear on turbos, there’s no solid evidence out there that it will outright bend fins and break your turbo. But when you think about it logically for a moment… if you’re running massive boost (say above 2bar), it would make sense to dispose the copious amounts of highly pressurised air somewhere else instead of reverse path through a spinning turbine wheel.

It is also worth noting that your car may shudder or stall if modded for flutter as the stock ECU can go a little crazy after seeing the unexpected air in the intake. This isn’t that noticeable on Nissans but others aren’t so lucky (like Evo’s) and need a ECU retune to fix this problem. Be sure to do your research first!

Does trak-life like and condone flutters?

Jay and I are running a no BOV setup and have no gripes with it. Personally I actually disliked the sound and the slight shudder feel on flutter but have gotten used to both over time… it’s a much sexier sound than my previous Blitz DD and HKS SSQVII BOV sounds.

In the end the flutters don’t really offer much in terms of functionality but it also doesn’t degrade anything so I’m happy to leave it as is… besides, Jay loves Pearl’s flutter… so much that she sounds like she ran over a flock of pigeons and turkeys whenever he takes her for a spin… stop wasting my fuel damn it!

Do you think flutter is awesome too? Does it get chicks? Let us know below!

About Flop

Flop
Open minded car enthusiast who appreciates most things on four wheels although JDM is where his heart lies. Wannabe racecar driver but having trouble fitting into his bucket seat since he's also a dedicated gym goer.

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19 comments

  1. Hey guys!

    Just wanna say “AWESOME SITE!””

    Love the DIY stuff for the S15’s.

    One question. When you setup the dose, do you get back fires? I do when i setup the dose.

    I run a 3″ exhaust from the front pipe (soon to get a dump pipe)

    If you don’t can you quick explain in a nutshell? Thanks

    Dave

    • Johnny

      Thanks for the positive feedback, it keeps us going 🙂

      If you’re running a standard ECU you will get backfires the reversion from the “dose” causes the air flow meter to read more air than that is actually ingested by the motor, thus more fuel is added to the mixture.

      Of course if you’re running an aftermarket ECU, the injection table can be trimmed to eliminate the over fueling or better yet run a MAP sensor based ECU and delete the AFM altogether.

      Hope that helps!

      Cheers,
      Jay

    • Flop

      Don’t worry Dave I’m still running the stock ECU and get plenty of pops on flutter so it is normal until you can get an aftermarket ECU like Jay said.

      Glad you like the site!

      Flop

  2. 160,000 rpm to zero rpm in under a second.
    Your fucking up your turbo and advising others to do it because it will get them chicks.
    What does this have anything to do with ‘trak-life’. You’ve made your cars slower and less reliable in the effort to impress a chicks.

    • Johnny

      We appreciate your comment, however our cars are punished on the track often without any issues to any of our turbochargers.

      It is just a long and ongoing myth that running no BOVs damage turbos, if you look at most trucks, buses, heavy machinery, etc. you’ll often find they also do not run BOV and yet they do millions of kilometres without failure.

      There is no conclusive evidence that not running a BOV damages turbos. Most of what you hear are internet myths and fictional. The idea of compressor stall or turbines turning backwards is entirely not possible. If you have any sensible understanding of fluid dynamics or even just a good understanding of physics neither of the two scenarios can be achieved from not running a BOV. Simply put it, if your motor is still running, there’s no way a turbo can spin backwards or stop. This is not fundamentally possible as a motor, at a basic level is an air pump. If you block the exhaust ports (from a compressor stopping OR turning backwards) the motor would come to nearly a complete halt as exhaust gases aren’t able to escape fast enough.

      I’ve owned many turbo charged cars, have run different aftermarket turbos and often don’t run BOVs and I’ve yet to see any exploding turbines or motors blowing up.

      Also if you look back in the 1980s when turbo chargers truly came to the spotlight, you will notice most turbo systems did not run BOVs, heck let’s look at F1 back in the 1980s!

      BOVs were mainly introduced to reduce noise emissions and improve throttle transitions and that’s about it.

      By the way, turbines don’t go from 100000 rpm to 0 rpm, its not possible as it defies the laws of physics (well unless you’ve got an external waste gate venting the exhaust gasses and you decide to stick a screw driver in the compressor)

      However, we have taken your comment on board James. A little debate never hurts!

      • I don’t want to sound like a know-it-all, but I develop turbochargers for a living and feel compelled to share some industry knowledge after reading this comment. This isn’t my opinion, this is just a brief explanation of facts regarding surge (stall) and BOVs. Much of Jay’s post is wrong and it is bad information to propagate to the public that surge is not a harsh condition. If you remove a BOV (or make the spring much heavier) and you hear “flutter,” it is a phenomenon called compressor surge (there is varying degrees of intensity from soft to very hard – obviously soft surge is not as harsh).

        Blow off valves exist not for noise or emissions… The purpose of the blow off valve is to regulate air pressure at the high pressure side of the compressor to ensure compressor surge does not occur. It is placed after the turbo to prevent damage (and it can improve throttle response because the comp wheel is terribly inefficient during surge). This is simply fact (and come on… just google blow off valve to you can read about this). Surge won’t completely destroy a turbo in seconds, but it is hard on it and CAN reduce life. Just because you have turbos that survive for a long period of time doesn’t mean it’s not a harsh condition – statistics and other influences are always involved in these kinds of things. It is not just rough on the compressor because of blade excitation which causes high cycle fatigue, but it oscillates loading of the thrust bearing.

        Surge is rapid reversals of fluid flow through the compressor (not rotor speed or direction reversals). When the engine no longer demands air mass flow, the angular momentum of the rotor (the high angular velocity and inertia) causes pressure to increase rapidly with mass flow reducing rapidly. This moves the aero conditions of the system to push the compressor into the surge line. Basically you can think of it like reverse turbo lag… the engine’s air demand slows down faster than the turbo’s speed and ability to deliver air. It can also be produced under load with a very poor wheel/engine match, but people like to induce it more often during shifts or from lifting the throttle.

        Using the idea of, “if trucks and buses don’t have them, then I don’t need them,” is not founded on an understanding of how engines work. If industrial equipment (which uses diesel engines) had a blow off valve it would be a terrible design. Diesel applications of turbochargers do not need blow off valves. This is because diesel and gas engines are radically different. Gas engines are based on the otto cycle not diesel cycle. Long story short – gas engine transients are far more aggressive and have much more rapid changes in air mass flow through the system. A properly matched turbo on a diesel engine will not need it (under extreme circumstances such as complete engine stall under load it can still surge). Gas engines are often a much different story (especially these days when much higher boost levels are used – unlike less aggressive use decades ago).

        EVERY manufacturer of turbochargers and engines work VERY hard to prevent compressor surge from ever occurring when they are matched to engines. If a BOV is required to limit pressure so surge does not occur, it is unwise to remove it ’cause it sounds good. Surge is definitely not the most harsh thing you can do to a turbo, but trucks, buses, etc. would never last millions of km if it was surging every time they shifted gears.

      • Flop

        Thanks for the very detailed reply, it’s great to have feedback from a technical standpoint.

    • Flop

      Thanks for your comment James.
      This article is purely for informational purposes, we don’t condone or condemn the removal of BOV’s.
      You are free to speculate and express your opinions but know that we share facts base on our experience.

      My stock turbo has seen 10+ trackdays and more than 140,000kms and is still in perfect running order.

  3. I run a GPC atmo Bov setup with a stiff gate so I get a release of air when I`m under it hard, however flutter when I`m just cruising. Works for me 🙂

    Thanks for the write up guys!
    Keep up the great work.

  4. What diamter pipe and silicone did you use for the intake??

    • Flop

      Hey mate

      The alloy intake is 2.5″ and it’s a 2.5″ to 3″ silicon pipe to connect to my pod filter adaptor (Z32). Hope that helps 🙂

      Phil

      • Awesome thanks mate. What about tne connection at the turbo end to the factory outlet? Is that 2.5 silicone hose? I am doing this very soon and not havn a great time finding out anything. Hence why im dredging up ur several year old article haha

      • Flop

        Haha no probs we’re still around to help out.
        But yup it’s 2.5″ from the stock snout on the compressor housing all the way to the stock AFM.

        Some local guys sell a 3″ snout if you wanted to go 3″ custom all the way… more power and flutters! But then again no point if it tapers down to 2.5″ on the stock AFM 🙁

  5. Hey Guys, I just bought an Evo 8 GSR Japanese imported model, it currently has the stock GSR BOV on it but i wouldnt mind doing an upgrade and getting a new BOV and was wanting to get the flutter. But reading forums its apparentlly very hard to get an evo to flutter any help please.

    • Flop

      Hey mate!

      Not that we’ve tried personally but the word on the street is that evo AFM’s are super sensitive so chances are the car will stall or splutter quite badly after flutterz. You can always give it a shot :p

      Or maybe wait for when you have an ECU that doesn’t require an AFM.
      It’s true though we definitely don’t see many fluttering evos!

      Phil

  6. Cool thanks for that. Yeh i will go the gktech snout and 3 inch all the way when i finally get around to setting up an r35 afm with my power fc… so many commitments..so little money 🙁

    • Flop

      Yup they’re definitely a money pit but it’s all worthwhile… I think 🙂

      Love to see some pics of your setup when done, especially as this is the first I’ve heard about using an R35 afm?

      • Yeh its the bew z32 haha. Much much cheaper and zero reversion issues. Apparantly can be tune much smoother with it too. However ot dosnt flow quite as much power as the z32 unless u put it in a larger pipe. Next option is pmas z32 replacement. Suuper cool part.

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